2008.11a
-
Due to the self-similarity of Berkovich and conical indenters, different materials may show the same loaddepth curve for single indentation. In this study, we first compare the load-depth characteristics of conical and Berkovich indenters via finite element method. We also analyze the variation of load-depth curves with angle of Berkovich indenter, indentation parameters, and material properties. With numerical regressions of obtained data, we then propose dual-Berkovich indentation formulae for material property evaluation. The proposed approach provides the values of elastic modulus, yield strength and strain-hardening exponent and corresponding stress-strain curve with an average error of less than 3%. The method is valid for any elastic indenters made of tungsten carbide and diamond for instance.
-
Yum, Young-Jin;Kim, Jong-Gook;Lee, Hyun-Woo;Hwang, Jung-Bok;Kim, Sun-Ung;Kim, Won-Hyuck;Yoo, Seung-Jo 7
A hot stamping technology of vehicle door impact beam made of thin sheet steel has been developed, with the aim of ensuring occupant safety in a side collision. This technology has been implemented to increase the strength of vehicle body parts and to reduce not only the weight of door impact beam but also the number of work processes. Mechanical tests were performed to obtain material properties of hot-stamped specimen and those were used as input data in stamping and structural simulation for optimal design of door impact beam. Strength of hot-stamped door impact beam increased to the value 102% higher than that of conventional pipe-shaped door impact beam and structural simulation showed that hot-stamped door impact beam achieved 28% weight reduction. -
A Wire-woven Bulk Kagome (WBK) is the new truss type cellular metal fabricated by assembling the helical wires in six directions. The WBK seems to be promising with respect to morphology, fabrication cost, and raw materials. In this paper, first, the geometric and material properties are defined as the main design parameters of the WBK considering the fact that the failure of WBK is caused by buckling of truss elements. Taguchi approach was used as statistical design of experiment(DOE) technique for optimizing the design parameters in terms of maximizing the compressive strength. Normalized specific strength is constant regardless of slenderness ratio even if material properties changed, while it increases gradually as the strainhardening coefficient decreases. Compressive strength of WBK dominantly depends on the slenderness ratio rather than one of the wire diameter, the strut length. Specifically the failure of WBK under compression by elastic buckling of struts mainly depended on the slenderness ratio and elastic modulus. However the failure of WBK by plastic failed marginally depended on the slenderness ratio, yield stress, hardening and filler metal area.
-
Sulfide stress corrosion cracking (SSCC) of materials exposed to oilfield environment containing hydrogen sulfide (
$H_2S$ ) has been recognized as a materials failure problem. Laboratory data and field experience have demonstrated that extremely low concentration of$H_2S$ may be sufficient to lead to SSC failure of susceptible materials. In some cases,$H_2S$ can act synergistically with chlorides to produce corrosion and cracking failures. SSC is a form of hydrogen embrittlement that occurs in high strength steels and in localized hard zones in weldment of susceptible materials. In the heat-affected zones adjacent to welds, there are often very narrow hard zones combined with regions of high residual stress that may become embrittled to such an extent by dissolved atomic hydrogen. On the base of understanding on sulfide stress cracking and its mechanism, SSC resistance for the several materials, those are ASTM A106 Gr B using in the oil industries, are evaluated. -
In the fields of electronics and displays where inkjet printing has demonstrated its capability to fabricate colorant subpixels of thin film transistor liquid crystal(TFT LCD) color filters and organic light emitting diode (OLED) displays, conducting tracks and TFTs, the production of satellite droplets is one of primary things to eliminate because they generally deteriorate the pattern quality. To understand the production mechanism of satellite droplets in this paper, driving waveforms such as monopolar and bipolar were employed and the influence of the pulse duration time were investigated in both experimental and numerical aspects.
-
A study on mechanical characterization of nano-thick films fabricated by transfer assembly techniqueThe transfer assembly (or transfer printing) technique is a promising method for fabricating multi-scale structures on various substrates including semiconductors and polymers, and has been applied to fabrication of flexible devices with superior performance to conventional organic flexible devices. The mechanical behaviors of the structures fabricated by the transfer assembly is a very important information for design and reliability evaluation purpose, but the measurement of the behaviors is difficult since their critical-dimensions are very tiny. In this study, Au films with nano-scale thickness were fabricated on a silicon substrate and their mechanical properties were measured using micro-tensile test. The Au films on the silicon substrate were then transferred to a PDMS substrate using the transfer assembly technique. Self-assembled monolayer (SAM) with a thiol group was used to enhance the transfer of Au films, and the mechanical behaviors were characterized using wrinkle-based test. The test results from micro-tensile and wrinkle-based test are compared to each other, and their implication to the transfer assembly technique is discussed.
-
In this study, electromechanical properties of carbon nanotube (CNT) thin film on flexible substrates were measured using a micro-tensile machine with functionality of simultaneous measurements of displacement, load and electrical resistance. The CNT thin film of about 100 nm thick was deposited on flexible substrates, polyethylene terephthalate (PET) using spraying and ink-jetting techniques. To investigate the effect of process condition on the electromechanical properties of CNT thin film, sets of CNT samples were fabricated under various heat treatments and microwave process. The microstructures of the CNT thin film before and after tensile test were investigated using Scanning Electron Microscope (SEM), and the failure modes of the CNT thin films were identified to understand their electromechanical behaviors and interaction with the flexible substrates. Based on the experimental results, the use of CNT thin film as flexible electrodes and strain gages is discussed.
-
The interfacial adhesion energy between resist and a substrate is very important due to resist pull-off problems during separation of mold from a substrate in nanoimprint process. And effect of substrate surface roughness on interfacial adhesion energy is very important. In this paper, we have treated glass wafer surface using
$CF_4$ gas for increase surface roughness and it has tested interfacial adhesion properties of UV resin/glass substrate interfaces by 4 point bending test. The interfacial adhesion energies by bare, 30, 60 and 90 sec surface treatments are 0.62, 1.4, 1.36 and 2$J/m^2$ , respectively. The test results showed quantitative comparisons of interfacial fracture energy (G) effect of glass wafer surface roughness. -
The mechanical behavior of small-sized materials has been investigated for many industrial applications, including MEMS and semiconductors. It is challenging to obtain accurate mechanical properties measurements for thin films due to several technical difficulties, including measurement of strain, specimen alignment, and fabrication. In this work, we used the micro-tensile testing unit with the real-time DIC (Digital Image Correlation) strain measurement system. This system has advantages of real time strain monitoring up to 50 nm resolution during the micro-tensile test, and ability to measure the young's modulus and Poisson's ratio at the same time. The mechanical properties of SCS (Single Crystal Silicon) are measured by uniaxial tension test from freestanding SCS which are
$2.5{\mu}m$ thick,$200-500{\mu}m$ wide specimens on the (100) plane. Young's modulus, Poisson's ratio and tensile strength in the <110> direction are measured by micro-tensile testing system. -
Strip bending test has been frequently utilized to measure the mechanical properties of freestanding thin films in substitute for the micro-tensile test. However, in spite of its simplicity and reliability, strip bending test has a few problems, for example, the measurement of strain and the calculation of stress at zero strain. In this study, these problems are precisely reviewed and proved. Upon this review, strip bending tester has been developed, which uses the confocal laser displacement meter to measure the deformed configuration of the specimen and the possibility and limitation of this testing system is carefully investigated including the estimation of uncertainty of the measurement of strain. Finally, to prevent errors and to improve the accuracy of this testing system, the shape of the specimen has been carefully studied and is proposed.
-
Laser cladding technology was studied as a method for upgrading the present repair procedures of damaged tubes in a nuclear steam generator and Doosan subsequently developed and designed a new Laser Cladding Repair System. One of the important features of this newly developed Laser Cladding Repair System is that molten metal can be deposited on damaged tube surfaces using a laser beam and filler wire without the need to install sleeves inside the tube. Laser cladding qualification tests on the steam generator tube material, Alloy 600, were performed according to ASME Section IX. Residual stress analyses were performed for weld metal and heat affected zone of as-welded and PWHT with SYSWELD software.
-
This study is performed to compare characteristics of various measurement technique for weld residual stress. AISI 304 plate with one path weld on the surface was manufactured for this study. Hole drilling method, X-ray diffraction method and instrumented indentation method were used to measure the residual stress before and after welding. All the results were compared and analyzed.
-
The objective of this study is to design a laboratory specimen for simulating residual stress of circumferential butt welding of pipe. Specimen type and method for residual stress generation were proposed based on the review of prior studies and parametric finite element simulation. To prove the proposed specimen type and loading method, the residual stress was generated using the designed specimen by applying proposed method and was measured. The measured residual stress using X-ray diffraction reasonably agreed with the results of finite element simulation considered in the specimen design. Comparison of residual strains measured at several locations of specimen and given by finite element simulation also showed good agreement. Therefore, it is indicated that the designed specimen can reasonably simulate the residual stress of circumferential butt welding of pipe.
-
The paper presents the characteristics of mechanical properties within the heat affected zone (HAZ) of dissimilar metal weld between SA508 Gr.1a and F316 stainless steel (SS) with Alloy 82/182 filler metal. Tensile tests were performed using small-size specimens taken from the HAZ regions close to both fusion lines of weld, and the micro-structures were examined using optical microscope (OM) and transmission microscope (TEM). The results showed that significant gradients of the yield stress (YS), ultimate tensile stress (UTS), and elongations were observed within the HAZ of SA508 Gr.1a. This was attributed to the different microstructures within the HAZ. In the HAZ of F316 SS, however, the welding effect dominated the YS and elongation rather than UTS, and TEM micrographs conformed the strengthening in the HAZ of F316 SS was associated with a dislocation-induced strain hardening.
-
Song, Tae-Kwang;Bae, Hong-Yeol;Kim, Yun-Jae;Lee, Kyoung-Soo;Park, Chi-Yong;Yang, Jun-Seog;Huh, Nam-Su;Kim, Jong-Wook;Park, June-Soo;Song, Min-Sup;Lee, Seung-Gun;Kim, Jong-Sung;Yu, Seung-Cheon;Chang, Yoon-Suk 79
In this paper, results of simulational round robin test on residual stress prediction was provided. Welding residual stress is one of the reasons for primary water stress corrosion cracking in PWR. Therefore, quantifying the welding variables and defining the recommendation for prediction welding residual stress is important. Through the round robin test, it is known that compressive axial and hoop residual stress occurs in dissimilar metal weld and pre-existing residual stress distribution in dissimilar metal weld was affected by similar metal weld due to short length of safe end. -
The primary water stress corrosion cracking (PWSCC) of dissimilar metal weld based on Alloy 82/182 is one of major issues in material degradation of nuclear components. It is well known that the crack initiation and growth due to PWSCC is influenced by material's susceptibility to PWSCC and distribution of welding residual stress. Therefore, modeling the welding residual stress is of interest in understanding crack formation and growth in dissimilar metal weld. Currently in Korea, a numerical round robin study is undertaken to provide guidance on the welding residual stress analysis of dissimilar metal weld. As a part of this effort, the present paper investigates distribution of welding resisual stress of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two-dimensional thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed design and fabrication data. The present results are compared with those from other participants, and more works incorporating physical measurements are going to be performed to quantify the uncertainties relating to modelling assumptions.
-
DMWs are common feature of the PWR in the welded connections between carbon steel and stainless steel piping. The nickel-based weld metal, Alloy 82/182, is used for welding the dissimilar metals and is known to be susceptible to PWSCC. A round-robin program has been implemented to benchmark the numerical simulation of the transient temperature and weld residual stresses in the DMWs. To solve the round-robin problem related to Pressurizer Safety & Relief nozzle, the thermal elasto-plastic analysis is performed in the DMW by using the FEM. The welding includes both the DMW of the nozzle to safe-end and the SMW of the safe-end and piping. Major results of the analyses are discussed: The axial and circumferential residual stresses are found to be -88MPa(225MPa) and -38MPa(293MPa) on the inner surface of the DMW; where the values in parenthesis are the residual stresses after the DMW. Thermo-mechanical interaction by the SMW has a significant effect on the residual stress fields in the DMW.
-
Weld overlay is one of the residual stress mitigation method which arrest crack. An overlay weld sued in this manner is termed a preemptive weld overlay(PWOL). PWOL was good for distribution of residual stress of dissimilar metal weld(DMW) by previous research. Because range of overlay welding is wide relatively, residual stress distribution on PWR is affected by welding sequence. In order to examine the effect of welding sequence, PWOL was applied to a specific DMW of KORI nuclear power plant by finite element analysis method. As a result, the welding direction that from nozzle to pipe is better good for residual stress distribution on PWR.
-
Oh, Chang-Young;Song, Tae-Kwang;Bae, Hong-Yeol;Chun, Yun-Bae;Kim, Yun-Jae;Lee, Kyoung-Soo;Park, Chi-Yong 94
In the welding process, weldments usually include repair weld during the manufacturing process. Repair welds is supposed to cause strong tensile residual stress. Moreover weldments, usually made by Alloy 82/182, is susceptible to PWSCC. Therefore, mitigation of welding residual stress in weldments is important for reliable operating. PWOL is one of the methods for mitigation and verified for over twenty years. In this paper, residual stress distribution of repaired weldments and the effect of PWOL on mitigation is examined for surge nozzle. -
This paper is to discuss distribution of welding residual stresses of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two dimensional (2D) thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed and fabrication data. On performing the welding analysis generally, the characteristics on the heat input and heat transfer of weld are affected on the weld residual stress analyses. Thermal analyses in the welding heat cycle process is very important process in weld residual stress analyses. Therefore, heat is rapidly input to the weld pass material, using internal volumetric heat generation, at a rate which raises the peak weld metal temperature to
$2200^{\circ}C$ and the base metal adjacent to the weld to about$1400^{\circ}C$ . These are approximately the temperature that the weld metal and surrounding base materials reach during welding. Also, According to the various ways of appling the weld heat source, the predicted residual stress results are compared with measured axial, hoop and radial through-wall profiles in the heat affected zone of test component. Also, those results are compared with those of full 3-dimensional simulation. -
Distribution of welding residual stresses are mainly characterized by degrees and frequencies of thermal loads applied to materials. However, other effects as component size and clamping condition can also affect stress distributions to a certain extent thus careful manipulation of these parameters based on clear understanding of how they affect residual stresses distributions and why can be additional measure to mitigate residual stresses. This paper discusses aforementioned issues for the case of safety and relief nozzle in nuclear power plant through finite element analysis.
-
Determination of weld-induced residual stress has been an important issue in nuclear power industry because several failures were reported in dissimilar metal weld parts due to primary water stress corrosion cracking. In this context, a couple of remarkable round robin analyses were conducted to quantify the welding simulation variables and to establish optimized numerical analysis process. The purpose of the present research is to introduce welding simulation results for a safety and relief nozzle, which has a dissimilar metal weld part as well as a similar metal weld part. First, finite element analyses are carried out to calculate residual stresses at the inside of nozzle considering only dissimilar metal welding. Subsequently, residual stresses taking into account both the dissimilar and similar metal welding are computed. The similar metal weld effect is evaluated by compa
-
Cho, Tae-Min;Choo, Yeon-Seok;Lee, Min-Jung;Oh, Hyeon-Cheol;Lee, Byung-Chai;Park, Tae-Hak;Shin, Young-Sug 115
In this study, effects of surface roughness on adhesive strength of heat-resistant adhesive RTV88 were examined. Sandblast was used to generate rough surfaces on aluminum adherends, and then tensile-shear tests of Al/RTV88 single lap joints were performed. The shear strength was shown to be affected by the surface roughness. Effective area, peel failure area, and cohesive failure area were introduced to explain the effects of surface roughness on the adhesive strength. An empirical relation for the failure force was proposed based on these parameters and verified by the test results. -
A plane strain problem of a crack on interface between an isotropic elastic conductor and a transversely isotropic piezoelectric ceramics is considered. The problem is reduced to system integrodifferential equations on the interface. These equations relate the normal and tangential components of the crack opening vector with distribution of normal and shear stresses on the crack surfaces. It therefore make it possible to obtain an exact solution as a function of the loading applied to the crack surfaces. As an example, some analytical solutions of the crack problem are given.
-
In the disk braking of the railway trains, kinetic energy of the vehicles is converted into thermal energy by friction between a brake disk and the pad materials. This can be cause of the iterative thermal shock and generates thermal cracks on the brake disk surface. In this study, we show the comparative thermal fatigue test procedures and thermal crack analysis process to evaluate the thermal fatigue characteristics of candidate materials designed for development of heat-resistant brake disk material. We carried out tests on the conventional brake disk materials used for Saemaul and Mugunghwa trains, then we comparatively analyzed the thermal crack initiation and propagation on the surface of a specimen. A thermal fatigue test procedure and a crack analysis process were suggested to evaluate the heat resistance of the developed materials at later studies.
-
A failure analysis of ammonia converter which suffered hydrogen attack in two years since its initial operating time was presented. It is constructed from 2.25 Cr.1 Mo steel. Analysis showed that the failure on closing seam weld joint was due to local improper post weld heat treatment (PWHT). Improper PWHT can introduce high residual stresses in thick-walled pressure vessel. High residual stress level in weld joint is very prone to hydrogen attack for any components which are operating in hydrogen gas environment. The repair procedures based on the principle to decrease the residual stress then proposed. The repair was controlled very carefully by applying several nondestructive tests in the each stage of repair. To assure the successful of the proposed repair, after one year since repair time, high temperature ultrasonic and TOFD methods were applied on-stream to this equipment in order to evaluate its post repair condition. The two methods showed good results on the repaired area.
-
Recently, a new periodic cellular metal(PCM) named as Wire wove Bulk Kagome(WBK) was introduced. Based on the shape of tetrahedra composing a WBK, WBKs are classified into two types, namely, concave and convex type. They are easily differentiated by changing the assembling sequence. The effect of geometrical parameters such as the wire diameter, strut length and number of layers on the compressive behavior of concave type WBK has already been investigated. In this work, the similar works were performed with the convex type WBKs. It was shown that the compressive strength of the convex type WBK was quite similar to that of the concave type. The compressive strengths of convex type specimens also depend on the slenderness ratio, but a little different from those of concave type specimens in the detailed behavior. And densification occurs earlier than the concave type WBK.
-
A transient finite element simulation is developed for the two-dimensional stationary elastoplastic layer between sliding layers, to investigate thermoelastoplastic instability(TEPI) due to frictional heating in the material. The analysis will show some differences between the case of thermoelastic instability and TEPI, especially according to the contact pressure above yield stress. A transient behavior of contact pressure is captured to explain the behavior of thermoplasticity of contact with different sliding velocity. The instability of contact pressure in the long range of braking time will be explored to understand the generation mechanism of hot spots.
-
In this research, stress components and principal stresses of O-ring under internal pressure and under uniform squeeze rate were obtained from the stress freezing method of photoelastic experiment and photoelastic experimental Hybrid method for 3-dimensional problems. The obtaining processes of those were introduced. It was certified that the processes of those are effective for the 3-dimensional stress analysis of structures. Stress freezing method, the obtaining processes of those and photoelastic experimental hybrid method were effectively applied to the stress analysis of O-ring made from rubber that under uniform deformation and internal pressure. Stress components and principal stress of Oring under uniform squeeze rate and under internal pressure were analyzed.
-
Using a three-dimensional (3-D) FE analyses, this paper provides the shape optimization of the standard test specimen for the torsion test, as well as a method for analyzing effects of misalignment under the angular and concentric misalignment. For verification, FE analysis is performed, which is designed for the perfectly full-model. To optimize the design shape of the torsion-controlled fatigue test specimen, we performed sensitivity analysis using shape parameters. Additionally, two kinds of misalignment (angular misalignment and concentric misalignment) are applied to the circular and tubular specimens to show effects of misalignments in the FE analysis. The present results will provide valuable information for designing shafts for every kind of mechanical system under torsional force.
-
In general structures, cleavage fracture may develop under the low constraint condition of larger scale yielding with a shallow surface crack. However, standard procedures for fracture toughness testing require very severe restrictions of specimen geometry. So the standard fracture toughness data makes the integrity assessment irrationally conservative. In this paper, cleavage fracture toughness tests have been made on side-grooved PCVN (precracked charpy V-notch) type specimens (10 by 10 by 55 mm) with varying crack depth, The constraint effects on the crack depth ratios are quantitatively evaluated by scaling model and Weibull stress method using 3-D finite clement method, After correction of constraint loss due to shallow crack depths, the statistical size effect are also corrected according to the standard ASTM E 1921 procedure, The results snowed a good agreement in the geometry correction regardless of the crack size, while some over-corrections were observed in the corrected values of
$T_0$ . -
This study is to evaluate the fatigue crack growth characteristics for base metals and welded metal of 9% Ni steels. Since this material has very excellent fracture toughness at low temperature, it has been widely used for inner walls of LNG storage tank. These materials to compare fatigue crack growth (FCG) behaviour are treated with heat by the method of quenching and tempering (QT), and quenching, lamellarizing and tempering (QLT). FCG tests using compact temsion (CT) specimen under stress ratio R=0.1, 0.5, and constant load are carried out. K-increasing tests are conducted by the standard test method described in ASTM E 647. To investigate the effect of welded metal on the crack growth rate, the locations of notch tip were chosen at the center of welded metal and heat affected zone (HAZ). Form the results, FCG rate has almost same tendency according to stress ratio, base and welded metal, the locations of welded metal. FCG rate of welded metal is somewhat faster than base metal. Also scanning electron microscope (SEM) is used to observe the striation of the fractured surface after fatigue crack tests.
-
The four-point bending test is a widely used method to determine material parameters. The aim of the present study was to evaluate the flexural strength (or modulus of rupture) and the Weibull modulus of cordierite ceramic substrate by means of four-point bending tests. The strength data from experiments followed Weibull statistics. These data indicate that the fatigue effects are more severe when the substrate temperature in the peripheral region is near
$200^{\circ}$ . At temperatures well above$200^{\circ}C$ the available design strength can be as high as 65% as substrate's initial strength. -
Thermoelectric materials convert temperature difference to electric power for power generation and vice versa for refrigeration. Recent advances in enhancing the thermoelectric figure-of-merit shed light on efficient power generation from the waste heat available in industries and vehicles. Nanoscale phenomena with both nanoscale constituent-embedded bulk samples and nanoscale materials proving enhanced thermoelectric performance have been widely reviewed. Bulk materials of crystal-orientation and nano-structured particle embedding seem to promise a higher thermoelectric figure-of-merit and an effective power generation application. As a preliminary study, Si-Ge nanocomposite was prepared with spark plasma sintering method and its properties were examined.
-
Seo, Jung-Ro;Go, Han-Ok;Chang, Yoon-Suk;Choi, Jae-Boong;Kim, Young-Jin;Kim, Hong-Ki;Choi, Young-Hwan 181
Recently, the Virtual Reality(VR) became one of the most powerful tools in making media files. In the field of engineering, while it is increasing to use 3D CAD model in the process of design to manufacturing, the VR is not popular in comparison with media business. XVL(eXtensible Virtual Reality Markup Language) is one of XML(eXtensible Markup Language) which is a standard web media language. XVL provides the connection between 3D CAD data and virtual reality, and it can be easily published through internet for the engineering purpose. In this study, a web based VR model for major components in a nuclear power plant has been developed by using XVL and corresponding 3D CAD data. The proposed model is expected to be used in the engineering field to cooperate among experts, and also, it will provide more plausible explanation to ordinary people. -
Injection molding is used to manufacture various kinds of products including very thin plate like frames. One such product is Door video phone system Panel which is our present object of investigation. During the molding process, large deflection problems in the final product always provokes for the several trials for the accuracy. To solve the issue we use Moldflow6.2 which is injection molding simulation software. It simulates the product exactly the way it happens in actual manufacturing environment. Differences in the geometrical parameters such as thickness changes will lead to the large deformation problems in the frame. However in our present study we simulate it in a well defined condition under several trials. Interesting observations are made in minimizing the deformation of the frame during the injection molding process. This way of approach is very useful in further works if any changes have to be made in the product.
-
As the lifetime of nuclear power plants (NPPs) reaches design life, the probability for fatal accidents increases. Most of accidents are known to be caused by degradation of mechanical components. Pressure tubes are the most important components in CANDU reactor. They are subjected to various aging mechanisms such as delayed hydride cracking (DHC), irradiation and corrosion, etc. Therefore, the integrity of pressure tube is key concern in CANDU reactor. Up to recently, conventional deterministic approaches have been utilized to evaluate the integrity of components. However, there are many uncertainties to prevent a rational evaluation. The objective of this paper is to assess the failure probability of pressure tube in CANDU. To do this, probability fracture mechanics (PFM) analysis based on the Genetic Algorithm (GA) is performed. For the verification of the analysis, a comparison of the PFM analysis using a commercial code and mathematical method is carried out.
-
Array of micro-dimple on polyoxymethylene (POM) surface was fabricated using Q-switched Nd:YAG laser and its characteristics were studied in terms of heat affected zone (HAZ), dimple geometry, and the effect of specimen surface roughness. Process parameters such as lamp current, process time, and the stream of air in order to minimize HAZ and flow of molten polymer into cavity were extensively studied in this work. Dimple geometry was further investigated by 3-D optical microscopy to provide deep insight into morphological analysis near the dimples. This paper also presents the applicapability of micro-dimples in polymeric tribological system, such as a thrust bearing. Micro-dimples were expected to provide low coefficient of friction and enhanced lubricity at the sliding interface.
-
In the present study, the deformation behavior of both of metal and polymer combination on impact was investigated. They have showed a different deformation behavior when the co-axially combined projectile was impacted on rigid target. The theory according to Taylor's simplified approach assumes an ideally rigid-plastic material model exhibiting rate-independent behavior and simple one-dimensional wave propagation concepts that neglect radial inertia. In the case of impact with polymeric materials, elastic strain in general are not negligible compared with plastic strain; and the rigid-plastic material behavior assumed by Taylor for metallic materials cannot be applied any more. Since, the sleeve and the core materials have widely different mechanical properties, they will produce a significant difference of mechanical impedance with each other. Therefore these impedance mismatch influences on the deformation behavior sleeved polymer projectile on impact. As a result, sleeved projectiles will generate a very interesting impact behavior. Therefore, the according to sleeved metal material and core polymer material can see expected. The objective of this study was to investigate the factors which influences on deformation behavior pattern of sleeve materials surface.
-
The interest in the mechanical behavior of materials at high strain rates has increased in recent years, and by now it is well known that mechanical properties can be strongly influenced by the speed of applied load. The split Hopkinson pressure bar (SHPB) has been widely used to determine mechanical properties of materials at high loading rates. However, to ensure test reliability, measurement error source must be accounted for and eliminated. During experiment, the specimens were located between the incident and the transmit bar. The presence of contact frictions between the test bars and specimen may cause errors. In this work, numerical experiments were carried out to investigate the effect of friction on test results. In SHPB test, the measured stress by the transmitted bar is assumed to be flow stress of the test specimen. Through the numerical experiments, however, it is shown that the measured stress by the transmit bar is axial stress components. When, the contact surface is frictionless, the flow stress and the axial stress of the specimen are about the same. When the contact surface is not frictionless, however, the flow stress and the axial stress are not the same anymore. Therefore, the measured stress by the transmitted bar is not flow stress. The effect of friction on the difference between flow stress and axial stress is investigated.
-
This paper presents an experimental study on a bending actuator with a shape memory alloy wire. In this study, we introduced design process and experimental result of the bending actuator. The bending actuator consists of a SMA wire, springs, and a glass/epoxy strip. In the bending actuator, springs were used to restore the SMA wire to its initial shape right after actuation. To obtain properties of the SMA wire, DSC test was performed and the behavior of the SMA wire under different loadings was observed. Finally, the proposed bending actuator shows reasonable actuation behavior with relatively lower power consumption, fast response and effective efficiency.
-
In this study, disk type of thermal barrier coating system for gas turbine blade was isothermally aged in the furnace changing exposure time and temperature. The aging conditions that determination occurs were determined by the extensive microscopic analyses and bond tests for each aging condition. The delamination map was drawn from the time-temperature matrix form which summarize the delamination conditions. Finally, a method to draw the delamination life diagram of a thermal barrier coating system by using the delamination map was suggested
-
This study is focused on an integrated numerical modeling enabling one to investigate the dynamic behavior and failure of 2-D textile composite and 3-D orthogonal woven composite structures weakened by micro-cracks and subjected to an impact load. The integrated numerical modeling is based on: I) determination of governing equations via a three-level hierarchy: micro-mechanical unit cell analysis, layer-wise analysis accounting for transverse strains and stresses, and structural analysis based on anisotropic plate layers, II) development of an efficient computational approach enabling one to perform transient response analyses of 2-D plain woven and 3-D orthogonal woven composite structures featuring the matrix cracking and exposed to time-dependent loads, III) determination of the structural characteristics of the textile-layered composites and their degraded features under various geometrical yarn shapes, and finally, IV) assessment of the implications of stiffness degradation on dynamic response to impact loads.
-
The reflection type photoelastic experiment can be used more effectively than the transparent type photoelastic experiment in industrial fields. However, the reflection type photoelastic experiment for orthotropic material has not been studied. Therefore, the reflection type photoelastic experimental hybrid method for the fracture mechanics of orthotropic material was developed in this research. Comparing the results obtained from this method with those from the hybrid method for isotropic material about the same isotropic specimen, the validity of this method was verified. And then, the reflection type photoelastic experiment for orthotropic material was applied to the orthotropic plates with a central crack of the various inclined angle. Using this hybrid method for the orthotropic material, it is able to obtain stress intensity factors and separate stress components at the vicinity of the crack-tip in orthotropic plates from only the isochromatic fringe patterns of isotropic coating material.
-
The efficiency of fiber reinforced CMC(ceramic matrix composite) on the SiC materials have been investigated, in conjunction with the fabrication process by liquid phase sintering and the characterization. LPS-
$SiC_f$ /SiC composites was studied with the detailed analysis such as the microstructure, sintered density, flexural strength and fracture behavior. The applicability of carbon interfacial layer has been also investigated in the LPS process. Submicron SiC powder with the constant total amount and composition ratio of$Al_2O_3,\;Y_2O_3$ as sintering additives was used in order to promote the performance of the SiC matrix material. LPS-$SiC_f$ /SiC composites were fabricated with hot press under the sintering temperature and applied pressure of$1820^{\circ}C$ and 20MPa for 1hr. The typical property of monolithic LPS-SiC materials was compared with LPS-$SiC_f$ /SiC composites. -
Nonferrous metals have a very important position in industry. At present, parts of shipbuilding, automobile, and aircraft etc. are designed and manufactured accurately, simultaneity need light-weight and high-strength. Aluminum copper alloys are one kind of typical precipitation hardening alloy which has been widely used. It is interesting to investigate transformation behavior of precipitated phase in such kind of alloys under high magnetic field. Transformation of materials under high magnetic field is many different compared with conventional condition. The author prepared the Al-4%Cu alloy.
-
It happened a failure on special bolt which supported main landing gear actuator up-lock rod of 00 aircraft. Fracture was occurred at end of center drilled hole and thread machined on bolt. Metallographic, fractographic, and other characteristics of embrittlement analysis and experiments carried out on the failed bolt to find out the reason. Bolt surface was cadmium electroplated(EP) to give lubrication and provide excellent corrosion resistance. Resultly, Bolt was failed due to cadmium embrittlement occurred during baking treatment as well as center drilled hole. for the failure that are relevant to failure analysis and prevention. For their successful functional application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and is complete with no center drilled hole
-
This study utilized a high speed lap-shear test to evaluate the mechanical behavior of Sn-37Pb/Cu and Sn-37Pb/Electroless Nickel immersion Gold under bump metallization solder joints under high speed loading and hence the drop reliability. The samples were aged for 120 h at different temperatures (
$120^{\circ}C,\;150^{\circ}C,\;170^{\circ}C$ ) and afterward tested at different displacement rates (0.01 mm/s to 500 mm/s) to examine the effects of aging on the drop life reliability. The combination of the stress-strain graphs captured from the shear tests and identifying a fracture mode dominant in the samples for different strain rates leads us to conclude that the drop reliability of solder joints degrades as the aging temperature increases, possibly due to the role of the IMC layer. This study successfully demonstrates that the analysis based on a high speed lap-shear test could be critically used to evaluate the drop reliability of solder joints. -
An micro-probe tip must be manufactured using thin film to evaluate integrity of the semiconductor with narrow distance between pads. In this study, fatigue tests were performed for BeCu thin film which is used in micro-probe tip of semiconductor test machine. The thin film was manufactured by electro plating process, and the specimens were fabricated by wire-cut electric discharge method to make hour glass type specimen of
$5000{\mu}m$ width,$29200{\mu}m$ length and$30{\mu}m$ thickness. The fatigue test of load control with 10Hz frequency was performed, in ambient environment. The fatigue cycles were tension-tension with mean stress, at stress ratio, R=0.1. -
The bending test of an individual ZnO nanorod was performed with a nano-manipulator and a force sensor inside the scanning electron microscope (SEM), and the bending properties of ZnO nanorod were also discussed. The ZnO nanorod used in this experiment was fabricated by means of solution base process. The force sensor used for bending test of ZnO nanorod was typed with cantilever. The force sensor was mounted on the nano-manipulator. The nano-manipulator was controlled and manipulated by a personal computer. The each end of an individual ZnO nanorod was attached on the rigid support and the tip of the force sensor with an electron beam exposure, and then the bending test was carried out by controlling of the nano-manipulator. The bending modulus of a ZnO nanorod was calculated at 69.35GPa after the bending test.
-
An assessment of creep-fatigue crack behavior is required to ensure the structural integrity for high temperature components such as fast breeder reactor structures or thermal power plant components operating at an elevated temperature. In this study, an evaluation of creep-fatigue crack growth has been carried out according to the French assessment guide of the RCC-MR A16 for austenitic stainless steel structures. The assessment procedures for creep-fatigue crack growth in the recent version of the A16 (2007 edition) have been changed considerably from the previous version (2002 edition) and the material properties (RCC-MR Appendix A3) have been changed as well. The impacts of those changes on creep-fatigue crack growth behavior are quantified from the assessments with a structural model. Finally the assessment results were compared with the observed images obtained from the structural tests of the same structural specimen.
-
For fitness-for-service analyses of underground natural gas pipelines, engineering assessment methods against possible defects need to be developed. The assessment methods for high pressure pipeline of KOGAS, was developed using the full size pipe burst tests and the finite element analysis. It included the defect assessment methods for a single and multi-corrosion, corrosion in girth welding part, corrosion in seam welding part, the mechanical damage defects as dent and gouge, crack and large plastic deformation of API 5L X65 pipe. In addition, we developed method to assess pipeline integrity by internal and external load to buried pipeline. Evaluation results were compared with other methods currently being applied to the gas pipeline. The program of Windows environment is made for easily using assessment methods. It provides a consistent user interface, so non-professional technician can easily and friendly use the FFS program from company intranet. Several evaluation programs is easily installed using one installer. Each program constitutes a common input interface and the output configuration program, and evaluation result store and can be recalled at any time. The FFS program based on independent evaluation method is used to evaluate the integrity and safety of KOGAS pipeline, and greatly contribute to safe and efficient operation of pipeline. This paper presents experimental, analytical and numerical investigations to develop the FFS methods for KOGAS pipeline, used as high pressure natural gas transmission pipeline within KOREA. Also, it includes the description of the integrated program for FFS methods.
-
To improve the durability of a hydrogen pressure vessel which is applied high-pressure, it needs the autofrettage process which induces compressive residual stress in the Aluminum liner. This study presents the elasto-plastic analysis to predict the behavior of structure accurately, and the Tsai-Wu failure criterion is applied to predict failure of pressure vessel of Aluminum liner and composite materials. Generally, plastic analysis is more complex than elastic analysis and has much time to predict. To complement its weakness, the AxicomPro(EXCEL program), applied radial return algorithm and nonlinear classical laminate theory (CLT), is developed for predicting results with more simple and accurate than the existing finite element analysis programs.
-
Wall thinning defect due to flow accelerated corrosion is one of major aging phenomena in most power plant industries, and it results in reducing load carrying capacity of the piping systems. A failure testing system was set up for real scale elbows containing various simulated wall thinning defects, and monotonic in-plane bending tests were performed under internal pressure to find out the failure behavior of thinned elbows. Various finite element models were generated and analysed to figure out and simulate the behavior for other thinning shapes and loading conditions. This paper presents the decreasing trends of load carrying capacity according to the thinning dimensions which were revealed from the investigation of finite element analysis results. A mechanical integrity evaluation model for thinned elbows was proposed, also. This model can be used to calculate the TES plastic load of thinned elbows for general internal pressure, thinning location, and in-plane bending direction.
-
The applicability of stainless steel type 316N to the PZR surge-lines of OPR1000 and APR1400 is investigated. So far, strainless steel type 347 has been used for the OPR1000 surge-lines. The degree of improvement in the leak-before-break(LBB) and component design margin is evaluated when stainless steel type 347 is substituted by type 316N. For the study, the tensile and J-R tests on type 316N and type 347 stainless steels were performed at 316 and the microstructure of both types was examined. Stainless steel type 316N shows the higher values on the stress-strain curves, J-R curves and stress intensity, Sm, compared to those of type 347. Therefore, stainless steel type 316N ensures the higher LBB and component design margins. As a result, this study shows that stainless steel type 316N could substitute type 347 for the surge-lines of OPR1000 and APR1400.
-
This paper attempts to quantify the effect of mismatch in creep properties on steady-state stress distributions for a welded branch vessel. A particular geometry for the branch vessel is chosen. The vessel is modeled by only two materials, the base and weld metal. Idealized power law creep laws with the same creep exponents are assumed for base and weld metals. A mismatch factor is introduced, as a function of the creep constant and exponent. Steady-state stress distributions within the weld metal, resulting from threedimensional, elastic-creep finite element (FE) analyses, are then characterized by the mismatch factor. We can find that average stresses in the weld can be characterized by the mis-match factor. And there is an analogy between elastic-creep and elastic-perfectly plastic.
-
This paper presents plastic limit loads of piping branch junctions with local wall thinning under combined pressure and in-plane bending, based on systematic three-dimensional finite element limit analyses using elastic-perfectly plastic materials. An ideal branch junction without weld or reinforcement around the intersection is considered with two locations of wall thinning; one in the run pipe, and the other in the branch pipe. Based on FE results, effects of thinning geometries on plastic limit moments are quantified and simple approximations of plastic limit loads are proposed.
-
This paper provides the methods to estimate the burst pressures of the pipes with defects, based on finite element analyses. FE codes are frequently adopted for the simulations of the burst tests of the pipes with defects. However, those do not give the burst pressure directly. Because the post-processing should be followed; determination of the fracture strains in accordance with triaxialities, monitoring the strains of pipes, etc. In the present work, these efforts are implemented in the user subroutine UHARD within the general-purpose FE code, ABAQUS. Four fracture criterions are introduced to estimate the burst pressure of pipes, and a simple fracture strain estimate is also developed. FE analyses for the pipe with gouge and corrosion are performed, and the results are compared with the experiment results.
-
Thick-walled cylinders, such as a cannon or nuclear reactor, are autofrettaged to induce advantageous residual stresses into pressure vessels and to increase operating pressure and the fatigue lifetimes. As the autofrettage level increases, the magnitude of compressive residual stress at the bore also increases. The purpose of the present paper is to predict the accurate residual stress of SCM440 high strength steel using the Kendall model which was adopted by ASME Code. Hydraulic pressure process was applied and thick-walled cylinders were autofrettaged up to 30% overstrain levels. Electro polishing was performed to get more accurate data. Residual stresses were measured by X-ray diffraction method. The autofrettaged surface which was plastically deformed analyzed using a scanning electron microscope(SEM). Although there were some differences in measured residual stress and numerical, there is a tendency to agree.
-
Piping in the Nuclear Power plants (NPP) are mostly consisted of carbon steel pipe. The wall thinning defect is mainly occurred by the affect of the flow accelerated corrosion (FAC) of fluid which flows in carbon steel pipes. This type of defect becomes the cause of damage or destruction of piping. Therefore, it is very important to measure defect which is existed not only on the welding partbut also on the whole field of pipe. Over the years, Infrared thermography (IRT) has been used as a non destructive testing methods of the various kinds of materials. This technique has many merits and applied to the industrial field but has limitation to the materials. Therefore, this method was combined with lock-in technique. So IRT detection resolution has been progressively improved using lock-in technique. In this paper, the quantitative analysis results of the location and the size of wall thinning defect that is artificially processed inside the carbon steel pipe by using IRT are obtained.
-
In this paper, we have studied the images which have been reconstructed by using combination of images acquired by the variation of operating frequency. When inner images have been reconstructed, they have been superposed by the surface state effect. In this case, the images of the phase object can be enhanced by the contrast of inner images. There is a kind of specimen, one is a reference block having 1/4T, 1/2T, 3/4T side drilled holes as main run piping material of the steam generator in nuclear power plants. It has been shown that the two results of defect shapes have better than before in this processing and phase contrast grow about twice. And we have constructed the acoustic microscope by using a quadrature detector that enables to acquire the amplitude and phase of the reflected signal simultaneously. Further more we have studied the reconstruction method of the amplitude and phase images, the enhancement method of the defect images' contrast.
-
For the cracked component under combined primary and secondary stress, an interacion between the loads occurs and the secondary stress is relaxed by the primary load. To account for this phenomena, R6 code provides the correction factor which is called V-factor. However, evaluation corrected with V-factor need to be examined for its conservatism. In this paper the conservatism of the current V-factor is examined for the circumferentially cracked pipe under the combined load and new evaluation method is proposed to reduce the conservatism.
-
This study investigates crack propagation behavior of Sn-3.0Ag-0.5Cu solder under pull-push loading conditions. Fatigue Crack Growth (FCG) tests were conducted on Center Cracked Plate (CCP) specimens in fast-fast (pp) strain waveform. The fast-slow (pc), slow-fast (cp) and slow-slow (cc) strain waveforms were also used to study the effect of strain rates. The crack propagation rates for the four strain waveforms were correlated with J-integral range and a scatter band of factor 4 was found. The crack growth rates for the pc waveform was highest, followed by cp, cc and then pp waveforms.
-
Fracture characteristics of plates and dome shapes for machinable glass ceramics using compressed shock wave. Machinable glass ceramics have been considered as a promising candidate material for the dome port cover of air breathing engine. This part of the air breathing engine has an important role separating solid and liquid fuel, and needs the frangible characteristics whereby the fracture of a part should not affect the internal components of combustion. The objective of this study are to evaluate the fracture pressure and phenomena of separated membrane using a shock tunnel. The experimental apparatus consists of driver, a driven section and a dump tank. The used material is machinable glass ceramic from Corning company. Specimens are used 3, 4.5 and 6mm thickness with plates and dome shapes. It is expected that the results obtained from this study can be used in the basic data for the dome port cover design of an air breathing engine.
-
Ratcheting behavior of IN 718 was investigated at
$649^{\circ}C$ under various proportional and non-proportional loading conditions with stress control. The material response was initially elastic but substantial plastic strain was developed as the material softened cyclically. Ratcheting strain was measured to near fatigue life, and is found to have three stages of development - primary, secondary (steady-state) and tertiary. The secondary stage dominates for most cases. Under the same equivalent stress amplitude and mean stress, it was revealed that circular path loading gives higher ratcheting rates and shorter lives than linear paths and that the more ratcheting occurs when the cyclic load is in the same direction as the mean stress. The ratcheting strain at failure depends not only on its rate but also on fatigue life itself, and it is not a primary life-determining factor. -
A Rubber mount is widely used for mechanical parts or engineering materials. Especially, it plays an important role in reducing mechanical vibration due to cyclic loading. But, rubber mount is damaged due to the cyclic loading and resonance. Therefore, it is necessary to investigate evaluation of fatigue life considering vibration characteristics for rubber. In this study, a vibration fatigue analysis was performed and based on Power Spectral Density(PSD) and the stress-life curve and a result of frequency response analysis in the finite element method. The measured load history in experiment was transformed to PSD curve. The stress-life curve was obtained by nonlinear static analysis and fatigue test. In addition, frequency response analysis was conducted for mechanical part. In order to evaluate fatigue life of rubber mount, vibration fatigue test was conducted at the constant acceleration-level as well. Fatigue life was determined when the load capacity is reduced to 60% of its initial value. As a result, predicted fatigue life of rubber mount agreed fairly well with the experimental fatigue life.
-
In characteristics of fatigue crack propagation, it is important that fatigue life is affected by crack closure phenomenon in thin sheet Al alloy. The purpose of this paper is to analyze the characteristics of fatigue crack propagation in constant loading condition for sheet Al 2024-T3 alloy of two sort of thickness and identify the difference of fatigue life in thin sheet specimen comparing experimental results of thin sheet specimen and relatively thick sheet specimen under same fatigue loading condition. In applying fatigue related material constants from fatigue crack propagation analysis, we attempt to operate the fatigue life estimating process of thin sheet specimen by modified Paris‘ law considering crack closure phenomenon and analyze the experimental and prediction results of fatigue life in thin sheet Al alloy.
-
In the present work, we address electric fatigue behavior in bending piezoelectric actuators using an acoustic emission technique. Electric cyclic fatigue tests have been performed up to ten million cycles on the fabricated specimens. To confirm the fatigue damage onset and its pathway, the source location and distributions of the AE behavior in terms of count rate are analyzed over the fatigue range. It is concluded that electric cyclic loading leads to fatigue damages such as transgranular damages and intergranular cracking in the surface of the PZT ceramic layer, and intergranular cracking even develops into the PZT inner layer, thereby degrading the displacement performance. The electric-induced fatigue behavior seems to show not a continuous process but a step-by-step process because of the brittleness of PZT ceramic. Nevertheless, this fatigue damage and cracking do not cause the final failure of the bending piezoelectric actuator loaded up to 107 cycles. Investigations of the AE behavior and the linear AE source location reveal that the onset time of the fatigue damage varies considerably depending on the existence of a glass-epoxy protecting layer.
-
An extensometer system to measure strain and displacement of cylindrical fatigue specimen in a autoclave of high temperature and high pressure environment has been developed by KEPRI. The extensometer reads the displacement caused by fatigue loads at the target length of the specimen installed inside the autoclave. The performance of the extensometer were tested at 15MPa,
$315^{\circ}C$ of a operating pressurized water reactor. Two LVDT's of magnet type were connected to the extensometer and used for converting the fatigue displacement to electronic signal. The device is being used for developing environmental fatigue curve of CF8M cast austenitic stainless steel (CASS) in the test condition of low cycle and low strain. This paper introduces the background and results of the development. -
Camber with positive deflection is one of the very important design parameters in the manufacture of railway coach. Positive camber is defined as concave shape such as an arch and it increases the strength of structure remarkably. But during the operation of a structure, the positive camber turns into negative camber and it loses the strength of structure. Therefore we should consider the camber effect when we evaluate the fatigue strength of negative cambered structure. For this purpose, we made a model of negative cambered locomotive car body and performed structural analysis and also we measured the dynamic loads at critical points during commercial line operation. Fatigue strength of locomotive was calculated by applying Miner's damage accumulation rule. Fatigue strength of the two locomotives which have different camber were compared to find out the effect of camber on dynamic load amplitude. We found that the more negative camber a locomotive had, the shorter fatigue strength obtained.
-
Bogie frame of the locomotive is an important structural member for the support of vehicle loading. A lot of study has been carried out for the prediction of the structural integrity of the bogie frame in experimental and theoretical domains. The objective of this paper is to estimate the structural integrity of the bogie frame. Strength analysis has been performed by finite element analysis. From these analysis, stress concentration areas were investigated. For evaluation of the loading conditions, dynamic stress were measured by using strain gage. It has been found that the stress and strain due to the applied loads were multi-axial condition according to the location of strain gage. The fatigue strength evaluations of the bogie frame are performed to investigate the effect of the multi-axial load through the employment of the critical plane approach.
-
An accelerated fatigue test is essentially required to maintain the reliability of the actual structure of KTX under operation conditions. However, actual fatigue life cannot be obtained if specimens are not adequate to the conventional fatigue test. Moreover component maker did not provide data of loading stress (S) - cycles at the failure (N). In this study, we suggest a prediction method of the S-N curve for establishing an accelerating test under various load levels. Load history was acquired from the field tests. A Rainflow method was used on the cycle counting of the field load data, and then, an S-N curve was obtained through the iteration process under the condition that the damage index satisfies to 1 in the Miner's rule.
-
This study is performed to understand three dimensional characteristics of weld residual stress for the surface weld on the stainless steel plate. AISI 304 plate with one path weld on the surface was used as a test specimen. Finite element analysis was done to analyze thermal transient and residual stress due to weld. The result of finite element analysis was validated by previous paper and measurement data. Among various techniques for residual stress measurement, instrumented ball indentation method was applied. The calculated residual stresses by finite element analysis showed good agreement with the measured results.
-
The disc-pad brake system is an important part of automobile safety system. During braking, the kinetic energy and potential energies of a moving vehicle are converted into the thermal energy through frictional heat between the brake disc and the pads. Most of the thermal energy dissipated through the brake disc. The temperature could be exceed the critical value for a given material, which leads to undesirable effects, such as the brake fade, premature wear, brake fluid vaporization, bearing failure, thermal cracks, and thermallyexcited vibration. The object of the present study is to investigate temperature field and temperature variation of brake disc and pad during single brake. The brake disc is decelerated at the initial speed with constant acceleration, until the disc comes to stop. The pad-disc brake assembly is built by 3D model with the appropriate boundary condition. In the simulation process, the mechanical loads are applied to the thermomechanical coupling analysis in order to simulate the process of heat produced by friction.
-
We suggest a linear elastic flat shell element based on the HT(hybrid Trefftz) method. We formulate the membrane part of the proposed element as an HT plane element with the drilling DOF. For the bending part, we developed a thick HT plate element that can represent transverse shear deformations accurately. Because we derive both the membrane and the bending parts consistently using the HT functional, we can easily construct the triangular and the quadrilateral elements in a unified way. In addition, warping of quadrilateral element is compensated by force and moment equilibrium equations. We evaluate the performance of the new element in terms of accuracy and convergence.
-
This paper presents a new development for topology optimization of heat-dissipating structure with forced convection. To cool down electric devices or machines, two types of convection models have been widely used: Natural convection model with a large Archimedes number and Forced convection with a small Archimedes number. Nowadays, many engineering application areas such as electrochemical conversion device or fuel cell devices adopt the forced convection to transfer generated heat. Therefore, to our knowledge, it becomes an important issue to design flow channels inside which generated heat transfer. Thus, this paper studies optimal topological designs considering fluid-heat interaction. To consider the effect of the advection in the heat transfer problem, the incompressible Navier-stokes equation is solved. This paper numerically studies the coupling phenomena and presents optimal channel design considering forced convection.
-
A topology optimization technique to develop extremely light trailer frame structure is performed due to the strong needs of the customers and makers owing to high level of oil price. First, the overall layout of the frame is derived using topology optimization and then, final specification is also derived utilizing DOE optimization technique for mass product.
-
In a traditional topology optimization method, material properties are usually distributed by finite element density and visualized by a gray level image. The distribution method based on element density is adequate for a great mass of 2-D topology optimization problems. However, when it is used for 3-D topology optimization, it is always difficult to obtain a smooth model representation, and easily appears a virtualconnect phenomenon especially in a low-density domain. The 3-D structural topology optimization method has been developed using the node density instead of the element density that is based on SIMP (solid isotropic microstructure with penalization) algorithm. A computer code based on Matlab was written to validate the proposed method. When it was compared to the element density as design variable, this method could get a more uniform density distribution. To show the usefulness of this method, several typical examples of structure topology optimization are presented.
-
Among various sensitivity evaluation techniques, semi-analytical method is quite popular since this method is more advantageous than analytical method and global finite difference method. However, SAM reveals severe inaccuracy problem when relatively large rigid body motions are identified for individual elements. Such errors result from the numerical differentiation of the pseudo load vector calculated by the finite difference scheme. In the present study, the adjoint variable method combined with complex variable is proposed to obtain the shape and size sensitivity for structural optimization. The complex variable can present accurate results regardless of the perturbation size as well as easy to be implemented. Through a few numerical examples of the static problem for the structural sensitivity, the efficiency and reliability of the adjoint variable method combined with complex variable is demonstrated.
-
Aircraft flutter analysis model consists of dynamic FE model and aerodynamic model. Dynamic FE model is composed of stiffness and mass model, and is used for the prediction of normal mode characteristics of the structure. Since aircraft flutter analysis is normally performed in the modal domain, dynamic FE model shall be constructed to describe the modal characteristics of the structure with sufficient accuracy. In this study, dynamic FE modeling method was described using full airframe FE model and structural and system weight data for aircraft flutter analysis. In addition, full airframe dynamic FE model for composite small aircraft was constituted for normal mode and flutter analysis, and the mass modeling results were compared with the target weight data to validate the mass modeling method proposed. Finally, full airframe flutter analysis of composite small aircraft was performed with the dynamic FE model and the aerodynamic model composed.
-
This research deals with the implementation hydrodynamic (HD) lubrication system with an integration of multibodydynamics (MBD) in order to analyze bearing lubrication characteristics such as pressure distribution and oil film thickness dynamically. The HD solver developed newly will transmit force and torque data to MBD solver, and receive position and velocity data from it continuously. After an analysis, we will verify the result with existing commercial software. Moreover, other functions like adjusting size of mesh grid, setting oil hole & groove effects, and consideration of thrust force will be introduced.
-
One of important factors in designing array-type MEMS resonators is obtaining a desired frequency response function (FRF) within a specific range. In this paper Krylov subspace-based model order reduction using moment-matching with non-zero expansion points is represented to calculate the FRF of array-type resonators. By matching moments at a frequency around a specific range of the array-type resonators, required FRFs can be efficiently calculated with significantly reduced systems regardless of their operating frequencies. In addition, because of the characteristics of moment-matching method, a minimal order of reduced system with a specified accuracy can be determined through an error indicator using successive reduced models, which is very useful to automate the order reduction process and FRF calculation for structural optimization iterations.
-
This paper presents a new approach to simulate fluid-solid interaction problems involving non-matching interfaces. The coupling between fluid and solid domains with dissimilar finite element meshes consisting of 4-node quadrilateral elements is achieved by using the interface element method (IEM). Conditions of compatibility between fluid and solid meshes are satisfied exactly by introducing the interface elements defined on interfacing regions. Importantly, a consistent transfer of loads through matching interface element meshes guarantees the present method to be an efficient approach of the solution strategy to fluid-solid interaction problems. An arbitrary Lagrangian-Eulerian (ALE) description is adopted for the fluid domain, while for the solid domain an updated Lagrangian formulation is considered to accommodate finite deformations of an elastic structure. The stabilized equal order velocity-pressure elements for incompressible flows are used in the motion of fluids. Fully coupled equations are solved simultaneously in a single computational domain. Numerical results are presented for fluid-solid interaction problems involving nonmatching interfaces to demonstrate the effectiveness of the methodology.
-
2-stroke marine diesel engine has generally one exhaust valve and three fuel injection nozzle which are key component for engine's performance and combustion. Fuel injection and exhaust valve driving system are driven by rotating of camshaft. Rotation of crank shaft drives the cam shaft through gear train that is composed of
$3{\sim}4$ gear wheels. Gear column supporting the gear wheel has to bear against the dynamics forces by engine running as well as gearing forces. In this paper, structural analysis for engine structure and fatigue strength assessment of welded joint is shown. Repeatedly full cyclic simulation during one cycle is performed to investigate the structural behavior of engine. Fatigue analysis is carried out based on IIW using submodeling technique to obtain more detailed stress distribution. -
Under driving condition, A vehicle experiences various kinds of loads, which brings on the buckling and fracture of suspension systems. Lower control arm (LCA), which consists of 2 bush joints and 1 ball joint connection, is the one of the most important parts in the suspension system. The bush joints absorb the impact load and reduce the vibration from the road. When analyzing the LCA behavior, it is important to understand the material properties and boundary conditions of bushing systems correctly, because of the nonlinearity characteristics of the rubber. In this paper, in order to predict the large scale deformation of the LCA more precisely, three factors are newly suggested, that is, coupling of bush stiffness between translation and rotation, bush extraction force and maximum rotation angle of ball joint. LCA stiffness is estimated by CAE and component test. Analysis and test results are almost same and the validity of considering three factors in LCA analysis is verified.
-
Induction hardening has been used to improve torsional strength and characteristics of wear for axle shaft which is a part of automobile to transmit driving torque from differential to wheel. After rapidly heating and cooling process of induction hardening, the shaft has residual stress and material properties change which affect allowable transmit torque. The objective of this study is to predict the distribution of residual stress and estimate the torsional strength of induction hardened axle shafts which has been residual stress using finite element analysis considered thermo mechanical behavior of material and experiments. Results indicate that the torsional strength of axle shaft depends on the surface hardening depth and distribution of residual stress.
-
In most of the passenger side airbag door in hard type IP today is designed with invisible tear-seam line. In order to design the tear-seam invisible, the tear-seam must be designed with required RWT (residual wall thickness) that is just thick enough to be broken by the PAB pressure on deployment and not by other surrounding impact forces. Hence, keeping the right optimum opening force is very important, and finding the right RWT became the key in designing the tear-seam. The study conducted in this paper describes the search for the optimum RWT around the tear-seam by using finite element method and the optimum RWT is suggested for milling type tear-seam having V-shape cross-section.
-
The reason for crashworthy landing gear is to contribute to the overall aircraft design goals in the event of a crash. One of crashworthy landing gear design approaches is inclusion of structural fuse. Structural fuse is used to control the mode of failure of landing gear. If structural fuse doesn't work at desired condition, other unexpected accidents can occur. In this paper, failure probability is calculated for landing gear structural fuse and improvement measure is introduced to improve failure probability of structural fuse.
-
Hemming, especially curl hemming, is required along the wheel housing for safety. Robot roller hemming is suitable for it. In this paper, both the flat hemming and the curl hemming along either the straight profile or the curved profile are analyzed using finite element program MSC.Marc to verify the hemming test results. Both the inner panel and the outer panel are modeled using 3-D solid elements and the roler is modeled using rigid surface. In the curl hemming, there is a case that the curl is not formed if the pre-hemming force is not sufficient. It agrees with the test results.
-
The important factor to evaluate the running safety of a railway vehicle would be the interaction force between wheel and rail(derailment coefficient), for which is one of important factors to check the running safety of a railway vehicle that may cause a tragic accident. Element that analyze derailment coefficient is consisted of wheel load and lateral force. In this paper, studied about method that calculate vertical force(wheel load) by bending load of axle in rolling stocks.
-
Under localization developing for the control valve of the safety grade Q Class 1 which is established in the atomic power plant followed ASME Code and important parts (Body, Yoke, Bonnet, Actuator) design and produced. In order to verify this analyzed the earthquake stress of AOV. AOV the above of 33Hz occurred from fIrst mode, the earthquake stress occurred from inside the yield strength of the material.
-
A HEV-relay plays a significant role as a mechanical switch which determines the operation of a gasoline engine or an electric motor in a hybrid electric vehicle (HEV). The HEV-relay has critical two problems in the operating process. First, the unstable current can occur in the operating process of the HEV-relay due to the severe bounce between moving and fixed electrode. Second, noises occur due to impact between electrodes in HEV-relay. In this research, spring properties such as stiffness and initial compression force, and electrode shape are designed to reduce the bounce time and noises caused by impact between moving and fixed electrode. The operating process of HEV-relay is simulated using LS-DYNA3D as explicit finite element code. The optimum spring properties are determined using the response surface method (RSM) as the design methodology, and the electrode shape is newly designed through the modifying the stiffness of moving and fixed electrode.
-
To improve occupants' safety in an emergency, crashworthy design is necessary to rotorcraft design and development. To improve crashworthiness capability, most of the crash energy should be absorbed by rotorcraft and the energy transmitted to the occupants should be minimized. To absorb the crash energy efficiently, the individual energy attenuation provided by landing gear, structure, fuel tank and seats should be considered totally. Especially, landing gear has the important role for crashworthy design because landing gear absorbs relatively large energy for the crash landing. In addition, military specifications require failure of landing gear shall not increase danger to any occupants by penetration of the airframe. To meet the specification requirements, failure mechanism should be prepared so that landing gear is collapsed safely and doesn't penetrate the airframe. In this study, design of failure mechanism which is necessary for the rotorcraft landing gear was performed and the results were presented.
-
An entire composite structure satellite is developing for the first time in Korea. All of the structure is made of CFRP-composite faced aluminum honeycomb sandwich structure. Here the random and sinusoidal spectrum analysis of the satellite was carried out by using the finite element method. The general spectrum analysis was herein performed but also the PSD (power spectrum density) function for random vibration analysis had been transformed into equivalent time domain function and then transient analysis is conducted. The time history of displacement, acceleration, stress and velocity responses with respect to the PSD input has been achieved by the time dependent transient function transformed from frequency PDS function. It enables one to perform dynamic durability analysis and then expect the life time of the composite structure. The composite faced sandwich structure's spectrum analysis of a domestically-developed satellite, STSAT-3, has been discussed in the present study.
-
The most landing gear use oleo-pneumatic shock strut to absorb the impact energy during touchdown. The shock strut is composed of the oil damper and the gas spring, especially the oil damper provides resistance force which is proportional to the square of landing speed. In case of high landing speed, the abnormal peak load can be occurred and transferred to the airframe structure. To prevent this, the pressure-relief valve is used to limit the damping force under the specific level. In this paper, it is presented the design process to find optimal damping and analysis results using pressure-relief valve.
-
The brake system is very important part of the machine working. If the machine can't be stopped, it would be serious accident. It is the same as the ship. The mooring winch brake hold the ship in harbor. But sometimes it appeared the excessive stress and brake lining would be broken. So it is necessary to change the shape of brake system with improve the braking power. This study carried out research on optimum design like as moved the position of link pin or modified the thickness of brake band and lining.
-
Recently, many patients related to heart disease have surgical operation by expanding a blood vessel to treat the angiostenosis. So far most angioplasties have been performed using balloon-dilative stent made of stainless steel. Some researchers are studying the stent made of shape memory alloy (SMA) to operate the angioplasty more easily. and there are several papers which introduce the angioplasty using SMA. However, most of the analysis models for stents are constructed using solid elements. So much computing time is required to solve the analysis model. In this study, we suggest the SMA stent model using 1D truss element which is much faster than stent model using 3D solid element. To represent non-linear behavior of SMA, we apply 1D SMA constitutive equation of Lagoudas'. Pseudo-elastic behavior of stent structures is presented as a numerical example.
-
An open frame structure is fastened by bolt joints for strength and shock attenuation. Therefore the full finite element model of an open frame structure should be properly modeled including bolt joints for strength analysis of the frames and joint assemblies which are operated under multi-loading conditions such as driving, drop, inertia and torsional loads. Then the joints and frames must satisfy the specified allowable strength constraints. Because the full finite element model has a large number of elements to perform strength analysis, a detailed fine bolt analysis seems to be very expensive. Therefore bolts of the full finite element model are approximately modeled by constraints equations to constrain degree of freedoms between adjacent nodes. However, the constraints equation method can exaggerate stress results at the constrained nodes. Thus a detailed bolt analysis and a theoretical/experiential formula of bolts for a worst bolt joint are performed using reaction force applied both bolt and bolt joint. Finally, the results from the two methods are compared and discussed to verify the safety of the open frame structure.
-
Thick pipes have been used in fields of ocean and industrial plants, and pipe arrangement of oil and water pipelines. Mostly, roll bending process has been used in manufacture of the pipes. Recently, however, studies on the pipe forming processes using brake press have been performed. Normally, the brake press has high aspect ratio, so structural integrity evaluation should be conducted. In this study, finite element analysis of structural integrity for the brake bending press was carried out for thick pipe forming process.
-
In recent years, the dissimilar metal, Alloy 82/182 welds used to connect stainless steel piping and low alloy steel or carbon steel components in nuclear reactor piping system have experienced cracking due to primary water stress corrosion(PWSCC). It is well known that one reason of the cracking is the residual stress by the weld. But, it is difficult to estimate exactly weld residual stress due to many parameters of welding. In this paper, the analysis of 3 FEM models made by ABAQUS Code is performed to estimate exactly the weld residual stress on the dissimilar metal weld. 3 FEM models are Butt model, Repair model and Overlay model and are the plane.strain 2D model. The thermal analysis and the stress analysis are performed on each model and the residual stresses on each model were calculated and compared respectively. Also, the specimen of Butt model was made and the residual stresses were measured by X-Ray method and Hole Drilling Technique. These results were compared with the FEM result of Butt model.
-
A roller with a shaft and hot oil paths for pressing electrodes of polymer batteries were modeled and analyzed by FEM. There are many hot oil tubes in the roller and shaft, through which
$72^{\circ}C$ hot oil flows for heating the surface of a roller and shaft. Thermal deformations and temperatures distributions of the roller and shaft were calculated and a convection boundary condition on surfaces was used. The influence of existence of a groove in the shaft on the flatness of a roller surface caused by thermal deformation was investigated. In addition, the amount of spring-back of electrodes under vacuum pressure and heating was calculated after the hot rolling process. It was shown from this study that the groove in one shaft had a favorable effect on the surface flatness. -
As the mobile electronic product is getting slimmer and smaller, the necessity of keypad is being increased. But the possibility of mis-typing keypad is increased rapidly due to the integrated keypad in the small mobile product. The business division has not considered the methodology of keypad design essentially. In this paper, analysis method and design evaluation standard to reduce the mis-typing of UMPC(Ultra Mobile Personal Computer) is suggested. First, the finite element analysis model and the biomechanical human body model are implemented in order to simulate the exact contact characteristic between finger and keypad. The reliability of analysis model is guaranteed by the comparison of the contact pressure between analysis result and experiment result of the pressure sensor. The design optimization of key shape and layout is derived through the response surface method. The prototype model is produced with the optimized design of keypad, and then it verified the advanced function with user mis-typing detection test. The optimized keypad design reduced the mis-typing ratio from 35% of existing model to 75 of proposed model. If this paper is widely applied to not only UMPC but also the other electronic products, the emotional quality of all products could be improved considerably.
-
Low Floor buses have no steps to get on or get off the main cabin to provide the old and the handicapped with easy access. The car body for the low floor bus was designed to consider Korean physical standard, passenger capacity (standee, seated, handicapped), arrangement of vehicle components, and bus law or regulations. It was designed as an one body, without any reinforcement armature, which has light-weight sandwich constructions with glass epoxy skins, aluminum honeycomb cores and inner-frames. In this paper, torsion rigidity of the designed car body was evaluated and compared with that of a car body with reinforcement armatures in the cabin. Finite element method verified that the designed car body without reinforcement armatures could satisfy requirements of torsion rigidity.
-
Most of vehicle manufacturers have applied exhaust gas recirculation (EGR) system to the development of diesel engines in order to obtain the high thermal efficiency without
$NO_X$ and Particulate Matter (PM) emitted from the engine. EGR system, which reflow a cooled exhaust gas from vehicles burning diesel as fuel to a combustion chamber of engine, has been used to solve this problem. In order to confirm the safety of the EGR system, finite element analysis was carried out. The safety of EGR system against temperature variation in the shell and tubes was evaluated through the thermal and structural analysis, and the modal analysis using ANSYS was also performed. Finally, the performance of EGR system was verified through the experiment and numerical simulation using effectiveness-NTU method. Program for the estimation of the heat exchange efficiency of the EGR system with regard to the dimpled tube shape was developed. -
풍력발전에 사용하는 풍력터빈의 블레이드의 적어도 20년 이상의 설계수명이 요구된단. 블레이드는 바람에 의한 압력, 지지대 구조에 의해서 가해지는 힘과 모멘트에 의해 블레이드에 변형이 가해진다. 특히 바람에 의해 블레이드는 연속적인 하중을 받아서 재료를 손상시킨다. 본 연구에서는 블레이드와 허브로 구성된 모델을 이용하여, 전산유체해석을 일차적으로 수행하여 블레이드 주변의 압력분포를 구하였다. 계산된 압력을 이용하여 다음 단계로 유한요소해석을 수행하여 블레이드 재료에 발생하는 응력을 계산하여 피로해석을 수행하였다. 피로해석을 통해 재료에 미치는 손상률을 구하였다. 다양한 블레이드 피치 각도과 바람의 속도에 따라 해석결과를 비료 분석하였다.
-
Recently, the intelligent service robot is applied for the purpose of guiding the building or providing information to the visitors of the public institution. The intelligent robot which is on development has a sensor to recognize its location at the bottom of it. Four wheels which are arranged in the form of a lozenge support the weight of the components and structures of the robot. The operating environment of this robot is restricted at the uneven place because the driving part and internal structure is designed in one united body. The impact from the ground is transferred to the internal equipments and structures of the robot. This continuous impact can cause the unusual state of the precise components and weaken the connection between each structural part. In this paper, a suspension system which can be applied to the intelligent robot is designed. The dynamic model of the robot is created, and the driving characteristics of the actual robot and the robot with suspension are compared. The road condition which the robot can operate is expanded by the application of the suspension system. Additionally, the suspension system is optimized to reduce the impact to the robot components.
-
An engine cradle is a quite important structural assembly for supporting the engine, suspension and steering parts of vehicle and absorbing the vibrations during the drive and the shock in the car crash. Recently, the engine cradle having structural stiffness enough to support the surrounding parts and absorbing the shock of collision has been widely used. The hydroforming technology may cause many advantages to automotive applications in terms of better structural integrity of parts, reduction of production cost, weight reduction, material saving, reduction in the number of joining processes and improvement of reliability. We focus on increasing the durability and the dynamic performance of engine cradle. For realizing this objective, several optimization design techniques such as shape, size, and topology optimization are performed. This optimization scheme based on the sensitivity can provide distinguished performance improvement in using hydroforming.
-
Rubber material properties and useful life evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the evaluation of characteristics and useful life prediction of rubber component for elevator cabin were experimentally investigated. The material test and accelerated heat-aging test were carried. Rubber material constants were obtained by curve fittings of simple tension, pure shear and bi-axial tension test data. Heat aging test results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the rubber material and component test several useful life prediction equations for rubber component were proposed. Predicted useful life of rubber component for elevator cabin agreed fairly with the experimental lives.
-
At the inlet and outlet differential pressure and The fluid velocity over 32m/s are damaged (Plug, sheet ring, trim) About reduction trim parts of the control valve. AOV of the differential pressure 1,500psi become often the damage in the nuclear power plant. Damages of AOV studied CFD analysis and improvement program. Multi-stage trim designs which decrease a fluid kinetic energy are demanded and AOV parts are demanded case hardening and material change.
-
This study is performed to analyze the fluid flow about 150mm shower heads of semiconductor device. Under the air pressure, the ideal gas of moving fluid is injected as 5m/s velocity into inlet of shower heads and the flow distribution in shower heads is measured according to pitch of plasma distribution device. As results, the maximum and minimum value of fluid velocity are investigated with their position. The velocity values at outlet are also studied. From two experiment using the plasma distribution device, the results of CFD are compared with the experimental results. That results shows stable flow of fluid in that case of corrected design from CFD.
-
A spacer grid is one of the most important structural components in a LWR nuclear fuel assembly. The primary considerations are to provide a Zircaloy spacer grid with crush strength sufficient to resist design basis loads, without significantly increasing pressure drop across the reactor core. In this study, the dynamic crush strength analysis and test are carried out for the specimens of a spacer grid assembly.
-
The reed switch position transmitter (RSPT) is used as a position indicator for the control rod in commercial nuclear power plants made by ABB-CE. But this position indicator has some problems when directly adopting it to the integral reactor. The Control Element Drive Mechanism (CEDM) for the integral reactor is designed to raise and lower the control rod in steps of 2mm in order to satisfy the design features of the integral reactor which are the soluble boron free operation and the use of a nuclear heating for the reactor start-up. Therefore the resolution of the position indicator for the integral reactor should be achieved to sense the position of the control rod more precisely than that of the RSPT of the ABB-CE. This paper adopts seismic resistance reed switches to the position indicator in order to reduce the damages or impacts during the handling of the position indicator and earthquake.
-
Most of structural analyses are concerned with the deformation and stress in a body subjected to external loads. In many fields, however, the interpretation of inverse problems is needed to determine surface tractions or internal stresses. In this study, the inverse processes by using the finite elements and the boundary elements are formulated for the evaluation of internal residual stresses from displacements measured on a remote surface. Small errors in the measured displacements often result in a substantial loss of accuracy of an inverse system. We use the Tikhonov regularization techniques to regularize the ill-conditioned system. Advantages and disadvantages are discussed through numerical examples.
-
It is well known that the topology optimization for plastic problem is not easy since the iterative analyses to evaluate the objective and cost function with respect to the design variation are very time-consuming. The finite element limit analysis is an efficient tool which is possible to predict collapse modes and sequential collapse loads of a structure considering not only large deformation but also plastic material behavior with moderate computing cost. In this paper, the optimum topology of a structure considering large and plastic deformation is obtained using the finite element limit analysis. To verify the constructed optimization code, topology optimizations of some typical problems are performed and the optimal topologies by elastic design and plastic design are compared.
-
Eddy current is usually generated in material with high conductivity by time-varying source such as AC current and also is induced in the moving source with relative velocity. The contactless magnetic brakes make use of the braking force from the eddy current generated by moving source and currently used for the secondary brakes of heavy trucks, buses and rail vehicles. This study aims to design the magnetization pattern of a permanent magnet type eddy current brake system to maximize the braking force. The analysis of the brake system is based on the two-dimensional finite element analysis. We use the sequential linear programming as the optimizer and the adjoint variable method for the sensitivity analysis.
-
In this present work, trimmed surface analysis for the 2D elasticity problem is presented. The main benefit of the proposed method is that no additional modeling for analysis of a trimmed surface is necessary. As the first attempt to deal with a trimmed surface in spline FEM, the information of the trimming curve and trimmed surface exported from CAD system is directly utilized for analysis. For this, trimmed elements are searched through employing projection scheme. For the integration of the trimmed elements, NURBSenhanced integration scheme which is used in NEFEM is adopted. The quadtree refinement of integration cell is performed for the complicated trimmed cases. The information of trimming curve is used for obtaining integration points as well as constructing stiffness matrix. The robustness and effectiveness of the proposed method are investigated by presenting various numerical examples.
-
The magnetic recording system shows the difference of the magnetic recording density according to the direction of the magnetic field. The yoke shape of the recording system affects the magnetic field direction; therefore, the recording density may be raised by changing the shape. This paper intends not only to increase the magnetic flux density of the record region but also to reduce the recording loss of a specific region through the simultaneous design of the yoke and the magnet. The recording loss can be reduced by minimizing the magnetic flux of the adjacent area to the recording region. The topology optimization method is used to obtain the optimal shape both of the yoke and the magnet. And the commercial package, Maxwell is used to verify the result.
-
This investigation studies the effects of material properties and corresponding propagation wave types on optimal configurations of sound absorbing porous materials in maximizing the absorption performance by topology optimization. The acoustic behavior of porous materials is characterized by their material properties which determine motions of the frame and the air. When the frame has a motion, two types of compressional wave propagate in the porous material. Because each wave in the material make different influence on the absorption performance, it is important to understand the relative contribution of each wave to the sound absorption. The relative contribution of the propagating waves in a porous material is determined by the material properties, therefore, an optimal configuration of a porous material to maximize the absorption performance is apparently affected by the material properties. In fact, virtually different optimal configurations were obtained for absorption coefficient maximization when the topology optimization method developed by the authors was applied to porous materials having different material properties. In this investigation, some preliminary results to explain the findings are presented. Although several factors should be considered, the present investigation is focused on the effects of the material properties and corresponding propagation waves on the optimized configurations.
-
In the manufacturing industries, viewing CAE analysis results is frequently required during the product development process for design verification. CAE data which include all related information of an analysis is, however, not efficiently shared among designers because CAE data size is in general large to deal with. In order to increase collaboration among designers this paper introduces the development of a CAE visualization system based on JT format exploiting for a large model visualization with a scene graph-based toolkit. Since CAE analysis results and JT format have different structure we developed a translator to convert the CAE result in binary format to the JT format. To show the effectiveness of JT format in showing the CAE result we also developed a prototype viewer offering basic functions provided by commercial systems. By using JT format we are able not only to reduce the size of analysis results, but to store a series of analysis results with several LOD in a data file.
-
The cylindrical shells are mainly used in the nuclear energy structure, pressure vessel, boiler and so on. When designing of shell structures, predicting the structure change under variety boundary conditions are necessary for estimating the safety. Design variables for the design engineer include multiple material systems and boundary conditions, in addition to overall structural design parameters. Since the vibration of stiffened cylindrical shell is an important consideration for structures design, the reliable prediction method and design methodology should be required. In this study, the optimum design of stiffened cylindrical shell for maximum natural frequency was studied by analytic and numerical method.
-
Autofrettage analysis of a bend in the fuel injcetion pipe has been performed to investigate the distribution of residual stresses due to pipe bending and autofrettage processes. The pipe bending was simulated by metal forming analysis using finite element method, and residual stress distribution after bending was found. Autofrettage following the pipe bending was performed by applying the hydrostatic internal pressures of 603 MPa, 535 MPa, 500 MPa on the pipe bend, corresponding to theoretical 26 %, 14 %, 9 % overstrain levels, respectively. Residual stress distributions due to bending and autofrettage were evaluated.
-
To obtain weight reduction and high performance, level set based topology optimization in magnetic fields is promising for the design of magnetic devices where the precise boundary shape and topological chanages are required. Level set function is introduced to represent ferromagnetic material boundaries and material properties of the magnetic reluctivity are determined. The optimization problem is formulated for maximizing the actuating force in a prescribed direction under limited usage of ferromagnetic material.
-
Bolts and nuts are widely used to fasten each mechanical part together in the machines and structures as vital elements. The primary role of bolts and nuts is keeping its axial force against the large external force and vibration. In this study, a lock nut using a spring was developed to maintain axial force. When the lock nut was made, crack occurred in the process of manufacturing the lock nut. Thus, optimized structure of lock nut was found by using the design of experiments. Lastly, the prototype of the optimized lock nut was created, and then the optimization result was verified by comparing results of the initial model and optimized model.
-
A stress distribution of composite laminates patches is obtained by using the Kantorovich method when the substrate is under uniaxial load. The analysis is based on the stress function approach and uses the complementary virtual work principle. The three-dimensional stresses satisfy the traction free conditions at the free edges and the top surfaces of the patch. The stress of the bottom surfaces of the patch is obtained from equilibrium equation of patch and substrate. To demonstrate the efficiency and validity of the proposed analysis, numerical examples for cross-ply and quasi-isotropic laminates are included. The present method provides accurate stresses in the interior and near the free edges of composite laminate patches.
-
The mechanical study on the anterior and posterior cruciate ligament(ACL, PCL) is of importance because the recent increase of outdoor and indoor activities is directly related to causing sport injuries on the knee joints. Constitutive models for many biological tissues have been known as hyperelasticitic models. The elastic behavior of ACL and PCL may be described by the free energy function which accounts for the matrix and the collagen fibers. This paper addresses a comparison of different types of the free energy function to the existing results.
-
Since the advent of pedicle screw fixation system, posterior spinal fusion has markedly increased This intemal fixation system has been reported to enhance the fusion rates, thereby becoming very popular procedure in posterior spinal arthrodesis. Although some previous studies have shown the complications of spinal instruments removal, i.e. loss of correction and spinal collapse in scoliosis or long spine fusion patients, there has been no study describing the benefit or complications in lumbar spinal fusion surgery of one or two level. In order to clarify the effect of removal of instruments on mechanical motion profile, we simulated a finite element model of instrumented posterolateral fused lumbar spine model, and investigated the change of mechanical motion profiles after the removal of instrumentation.
-
In this paper, we developed a physically-based micromechanical model for inelastic deformation of ceramic powders. The aggregate response of ceramic particles was modeled using the two-surface yield function which considered the shear-induced dilatancy caused by friction, rolling resistance and cohesion between powder particles and consolidation caused by plastic deformation of powder themselves under high compression. The constitutive equations were implemented into the user-subroutine VUMAT of finite element program ABAQUS/Explicit. The material parameters in the constitutive model were identified by calibrating the model to reproduce data from triaxial compression tests and simple compression tests. The density distribution obtained by using the proposed model was in good quantitative agreement with the experimental results of the triaxial compression and cold isostaic compression as well.
-
An advanced computational strategy for improvement of the accuracy of the structural analysis is developed in this paper. The finite elements connecting the primary nodes are constructed as a ground mesh in a domain, and the secondary nodes can be placed arbitrarily without reconstruction of a mesh. The support domains of the secondary nodes are defined on the basis of finite element mesh, and the shape functions are constructed by using MLS(moving least square) approximations. The present method is useful for controlling the errors without reconstruction of mesh when you add or remove nodes in a domain.
-
Moment-based reliability analysis is the method to calculate reliability using Pearson System with first-four raw moments obtained from simulation model. But it is too expensive to calculate first four moments from complicate simulation model. To overcome this drawback the MD(multiplicative decomposition) method which approximates simulation model to kriging metamodel and calculates first four raw moments explicitly with multiplicative decomposition techniques. In general, kriging metamodel is an interpolation model that is decomposed of global model and local model. The global model, in general, can be used as the constant global model, the 1st order global model, or the 2nd order global model. In this paper, the influences of global models on the accuracy and robustness of raw moments are examined and compared. Finally, we suggest the best global model which can provide exact and robust raw moments using MD method.
-
In this study, homogenization method combined with the effective interface model for the characterization of properties of the nanoparticulate composites is developed. In order to characterize particle size effect of nanocomposites, effective interface model has been developed. The application range of analytical micromechanics approach is limited because a simple analytical approach is valid only for simple and uniform geometry of fiber particles. Therefore this study focuses on the analysis of mechanical properties of the effect interface through the continuum homogenization method instead of using analytical micromechanics approach. Using the homogenization method, elastic stiffness properties of the effective interface are numerically evaluated and compared with the analytically obtained micromechanics solutions. The suggested homogenization method is expected to be applied to optimization problems for nanocomposite design.
-
In this presentation, we study numerically an optimization problem of a fire fighting robot cooling system. The governing equation for the system is the unsteady heat equation with source term. We use a multigrid method for numerical solutions in three-dimensional space. We investigated the effects of various parameters and the results will be presented.
-
Artificial neural network (ANN) has been extensively used in areas of nonlinear system modeling, analysis and design applications. Basically, ANN has its distinct capabilities of implementing system identification and/or function approximation using a number of input/output patterns that can be obtained via numerical and/or experimental manners. The paper describes a role of ANN, especially a back-propagation neural network (BPN) in the context of engineering analysis, design and optimization. Fundamental mechanism of BPN is briefly summarized in terms of training procedure and function approximation. The BPN based causality analysis (CA) is further discussed to realize the problem decomposition in the context of multidisciplinary design optimization. Such CA is also applied to quantitatively evaluate the uncoupled or decoupled design matrix in the context of axiomatic design with the independence axiom.
-
Design analysis and computer experiments (DACE) model is widely used to express efficiently the nonlinear responses in the field of engineering design. Kriging model, a DACE model, can approximately replace a simulation model that is very expensive or highly nonlinear. The kriging model is composed of the summation of a global model and a local model representing deviation from global model. The local model is determined by correlation coefficient of the pre-sampled points, where determination of the correct correlation coefficient has an effect on accuracy and robustness of the kriging model. Therefore, robustness of the correlation coefficient is explored with respect to degrees of the global model. Then we propose the range of correlation coefficient to make correct and robust kriging model and the influence of the correlation coefficients on the degrees of global model with respect to the nonlinearity of the pre-sampled responses.
-
The experiment of dome port cover under shock impact is performed with shock tube. The dome port cover blocked intake air duct up from the solid propellant during air breathing vehicle speed reach Mach 2.0. When the air breathing vehicle reach Mach 2.0, the inlet cover is removed and the dome port cover is broken to pieces by detonator or pressure of inlet air. Thus the dome port cover not only must stand the pressure of combustion chamber but also easy to break from the RAM pressure. In this study, a fracture evaluation on the
$Al_2O_3$ ceramic spherical dome and circular plate port under impact has been presented. Ceramic were supported by the rigid body and a couple of O-ring. The Mooney-Rivlin model have been used to describe behaviors of both O-ring. And spherical dome and circular plate fracture results of the LS-DYNA code using Johnson-Holmquist(JH-2) constitutive equation was compared. -
Upper Bound Analysis of Dynamic Buckling Phenomenon of Circular Tubes Considering Strain Rate EffectA circular tube undergoes bucking behavior when it is subjected to axial loading. An upper bound analysis can be an attractive approach to predict the buckling load and energy absorption efficiently. The upper bound analysis obtains the load or energy absorption by means of assumption of the kinematically admissible velocity fields. In order to obtain an accurate solution, kinematically admissible velocity fields should be defined by considering many factors such as geometrical parameters, dynamic effect, etc. In this study, experiments and finite element analyses are carried out for circular tubes with various dimensions and loading conditions. As a result, the kinematically admissible velocity field is newly proposed in order to consider various dimensions and the strain rate effect of material. The upper bound analysis with the suggested velocity field accurately estimates the mean load and energy absorption obtained from results of experiment and finite element analysis.
-
Very High Temperature Gas Cooled Reactor (VHTR) has been selected as a high energy heat source for nuclear hydrogen generation, which can produce hydrogen from water or natural gas. A primary hot gas duct (HGD) as a coaxial double-tube type cross vessel is a key component connecting the reactor pressure vessel and the intermediate heat exchanger for the VHTR. In this study, structural sizing methodology for the primary HGD with a coaxial double-tube of the VHTR that produces heat at temperatures in the order of
$950^{\circ}C$ was suggested and a structural pre-sizing of it was carried out as an example. -
This paper proposes elastic stress intensity factors and crack opening displacements (CODs) for a slanted axial through-wall cracked cylinder under an internal pressure based on detailed 3-dimensional (3-D) elastic finite element (FE) analyses. Based on the elastic FE results, the stress intensity factors along the crack front and CODs through the thickness at the center of the crack were provided. These values were also tabulated for three selected points, i.e., the inner and outer surfaces and at the mid-thickness. The present results can be used to evaluate the crack growth rate and leak rate of a slanted axial through-wall crack due to stress corrosion cracking and fatigue. Moreover, the present results can be used to perform a detailed Leak-Before-Break analysis considering more realistic crack shape development.
-
The objective of this study is to evaluate the integrity for a reactor pressure vessel under the pressurized thermal shock by applying the probability fracture mechanics. A semi-elliptical axial crack is assumed to be in the beltline region of the reactor pressure vessel. The selected random variables are the neutron fluence on the vessel inside surface, the content of copper, nickel, and phosphorus in the reactor pressure vessel material, and initial RTNDT. The probabilistic integrity analysis was performed using the Monte Carlo simulation.
-
A thermal stratification may occur in the horizontal parts of the surge line during operating transients of the pressurizer, which produces relatively high fatigue usage factor. Heat-up transient is the most severe case among the transient conditions. In this study, to study the relationship between the magnitude of thermal stratification and the length of vertical part of the surge line, some parametric fluid-structure interaction (FSI) analyses with different length variables of the vertical part of the surge line were performed for plant heat-up transient condition by using 3-dimensional numerical analysis. The conservativeness of the traditional finite element model for thermal stratification analysis based on the conservative assumption in the surge line was also discussed by comparison of the results of 3-dimensional transient FSI analysis of this study. Stresses calculated with 3-dimensional transient model were considerably reduced comparing with the traditional analysis.
-
A 6 D.O.F Stewart platform type parallel robot has been developed as a simulator to test the surveillance robot stabilization control. Since the surveillance robot is installed on the unmanned ground vehicle (UGV), it is required to have a stabilization control system to compensate the disturbance from the UGV. PID control scheme has been applied to the parallel robot to generate controlled motion following the input motion.
-
Human-like biped robot is a representative multi-links manipulator and undoubted redundancy system. However many researchers separate biped robot into each limb and analyze the members individually for the convenience analysis. This approach is not desirable for natural trajectory generation and energy optimization. This paper proposes the analysis method considering both legs together and the weighted pseudoinverse optimizing energy consumption.
-
Uncertain dynamic parameters and joint flexibility have been problem to control robot manipulator precisely. Hence, even if the controller tracks the desired trajectory well with the feedback of the motor encoders, it is hard to achieve the desired behavior at the end-effector. In this paper, robot trajectory is taught by a general heuristic iterative learning control (ILC) algorithm in order to reduce tracking error of the tool center point (TCP) and the results of tracking with 6 DOF industrial robot manipulator are presented. The performance is verified based on ISO 9283.
-
This paper presents the fluid characteristics of the spool actuator used for construction vehicles. A spool actuator is used for directional control of pressurized fluid and has a roll to lock the fluid flow. It is important to design the spool actuator optimally because this actuator is actuated in the sleeve by sliding motion and has some critical design parameters such as stick-slip, leakage and shock pressure. The parameters like stick-slip and leakage can be solved by precision manufacturing but the shock pressure which is taken place when the fluid direction is changed needs the parameter analysis procedure throughly. In this study, mathematical modeling and 2 & 3 phase flow dynamics analysis of the spool actuator were achieved. Using suggested model, all possible operating conditions were analyzed.
-
The aerostat dynamic equation of motion has been built including the tether cable dynamic effects. A numerical program to solve the derived equation of motion has been developed. The dynamic motion of the 32m aerostat has been analyzed under discrete gust and continuous turbulence. The aerostat behaviors under discrete gust which represents a deterministic approach for determining design loads for manned aircraft are solved to verify the effect of aerostat mechanical properties on the aerostat dynamic behavior. Continuous turbulences are simulated for each given altitude, translational mean wind velocity and gust intensity. Dynamic behaviors of the 32m aerostat are simulated for each continuous turbulence conditions. Translational and vertical velocity and pitching behavior and tether reaction force are monitored for each simulation.
-
Estimated values for maximum lift coefficients of a light airplane, ChanGong-91, derived from an analytical method using a test database, a computational fluid dynamic method, a wind tunnel test, and a flight test are compared. The DATCOM method and VSAERO code are applied as the analytical method and the computational fluid dynamic method, respectively, in order to estimate the maximum lift coefficients of a light airplane. The wind tunnel test is conducted using a 1/14.5 scaled model installed in a closed circuit type wind tunnel. For the flight test approach, the wings-level power-off stall tests are performed to obtain the maximum lift coefficients. As a point of reference for the flight test results of the maximum lift coefficients, the differences of both estimates derived from the DATCOM method and the wind tunnel test data are smaller than those derived from VSAERO.
-
Various scanning systems have been studied in many industrial areas to acquire a range data or to reconstruct an explicit 3D model. Currently optical technology has been used widely by virtue of noncontactness and high-accuracy. In this paper, we describe a 3D laser scanning system developped to reconstruct the 3D surface of a large-scale object such as a curved-plate of ship-hull. Our scanning system comprises of 4ch-parallel laser vision modules using a triangulation technique. For multi laser vision, calibration method based on least square technique is applied. In global scanning, an effective method without solving difficulty of matching problem among the scanning results of each camera is presented. Also minimal image processing algorithm and robot-based calibration technique are applied. A prototype had been implemented for testing.
-
The subway noise in curved line is affected not only by rail condition but also wheel condition and dynamic characteristics. The railway curving noise can be divided into 2 categories. The first is noise depending on the vehicle speed, and the second is the one independent on vehicle speed. In this study the noises were reviewed by using eigen-mode of wheel and waterfall plot which shows noise level in time-frequency domain. And also those were reviewed in viewpoint of stick-slip noise and wheel flange contact noise.
-
This paper presents a the method for estimating the noise source contribution on the road noise of the vehicle in a multiple input system where the input sources may be coherent with each other. By coherence function method, it is found that the biggest part of the noise source in the road noise is generated by structural vibration on the mechanical-acoustic transfer functions of vehicles. This analysis is modeled as four input/single output system because the noise is generated with four wheels that mechanism of the road noise is very complicated. The coherence function method is proved to be useful tool for identifying of noise source. The overall levels of the interior noise be coherence function method are compared with those measured and calculated by the frequency response function approach using mechanical excitation test. The experimental results have shown a good agreement with the results calculated by the coherence function method when the input sources are coherent strongly each other. The estimation of the road noise indicates that significant coherent can be achieved in the vehicle interior noise.
-
Vibration of a non-linear system under random parametric excitations was evaluated by probablistic methods. The non-linear characteristic terms of a system were quasi-linearized and excitation terms were remained as they were given. An analytical method where the square mean of error was minimized was ysed. An alternative method was an energy method where the damping energy and rstoring energy of the linearized system were equalized to those of the original non-linear system. The numerical results were compared with those obtained by Monte Carlo simulation. The comparison showed the results obtained by Monte Carlo simulation located between those by the analytical method and those by the energy method.
-
MRE(Magneto-rheological Elastomer) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb broader frequency range of vibration. These characteristic phenomena result from the orientation of magnetic particle (i.e., chain-like formation) in rubber matrix. In this study, NR was used as a matrix in order to manufacture MREs. Magnetic reactive powder(MRP), having rapid magnetic reaction, was selected as a magnetic particle to give magnetic field reactive modulus. The mechanical properties of manufactured MREs were measured without the application of magnetic field. The results showed that the tensile property and resilience were decreased while the hardness was increased with the addition of CIP. The analysis of MR effect was carried out by FFT analyzer with various magnetic flux. As the addition of MRP and magnetic flux increased, increment of MR effect was observed.
-
The paper presents research for the established experiment environment of multi vehicle robot, localization algorithm that is based on vehicle control, and path tracking. The established experiment environment consists of ultrasonic positioning system, vehicle robot, server and wireless module. Ultrasonic positioning system measures positioning for using ultrasonic sensor and generates many errors because of the influence of environment such as a reflection of wall. For a solution of this fact, localization algorithm is proposed to determine a location using vehicle kinematics and selection of a reliable location data. And path tracking algorithm is proposed to apply localization algorithm and LOS, finally, that algorithms are verified via simulation and experimental
-
Today, hydraulic systems play an important role in modern industry for the reasons that hydraulic actuator systems take many advantages over other technologies with high durability and the ability to produce large forces at high speeds. In recent years, electro-hydraulic actuator systems, which combine electric and hydraulic technology into a compact unit, have been adapted to a wide variety of force, speed and torque requirements. Moreover these systems resolve energy consumption and noise problems characteristic existed in the conventional hydraulic systems. Therefore, these systems have a wide range application fields especially in an excavator. So the purpose of this paper is to demonstrate efficiency of the energy saving and present some control algorithms which apply to electro-hydraulic actuator system in the bucket of the excavator. Experiments are carried out to verify the effectiveness of the proposed system with various external loads as in real working conditions.
-
This paper introduces the automatic fine Bituminous Coal injection lance position control method using flame image process. The fine Coal injection lance is used to supply additional heat into the furnace in Mill plant. It injects fine coal into high pressured air flow and produces very heated and high pressured flame. For the such high temperature and pressure, the fine coal injection lance effects not only efficiency of burner but also furnace abrasion. To keep efficient combustion status and to avoid the abrasion, in this paper, the flame is monitored by computer image process. This paper proposes the flame image process method and lance position control according to calculated result for flame image process.
-
Train dynamics affects significantly safe and efficient operation of a train, especially during traction or braking period. Train dynamics is intrinsically complex due to many DOF motions in a three-dimensional space, and its behavior during the braking stage is too complex to understand and design an effective braking logic of the train. In this paper, we present a two-dimensional model with three DOF motion in a longitudinal, vertical, and pitch direction for the Hanvit 200 tilting train, which is efficient to analyze a braking performance. Furthermore, we analyze the braking logic and simulate the braking process of the Hanvit 200 tilting train using Simulink.
-
Wind turbine requires service life of about 20 years and each components of wind turbine requires high durability, because installation and maintenance costs are more expensive than generated electricity by wind turbine. So the design of wind turbine must be verified in various condition before production step. This paper demonstrates the application of a generic methodology, based on the flexible multibody simulation technique, for the dynamic analysis of a wind turbine and its drive train. The concern of the paper is the computation of dynamic loads of wind turbine in emergency-stop condition. The finite element model is used to analyse the dynamic behaviour of the wind turbine.
-
A linkage mechanism is a device to convert an input motion into a desired output motion. Traditional linkage mechanism designs are based on trial and error approaches so that size or shape changes of an original mechanism often result in improper results. In order to resolve these problems, an improved automatic mechanism synthesis method that determines the linkage type and dimensions by using an optimization method during the synthesis process has been proposed. For the synthesis, a planar linkage is modeled as a set of rigid blocks connected by zero-length translational springs with variable stiffness. In this study, the sizes of rigid blocks were also treated as design variables for more general linkage synthesis. The values of spring stiffness and the size of rigid block yielding a desired output motion at the end-effecter are found by using an optimization method.
-
In this paper, kinematic analysis for a planar 3-DOF redundant stage which has four actuators is presented by using SimMechanics software package. SimMechanics is a block sets of the Matlab/Simulink package. The SimMechanics enables a simplified model for a complex kinematic mechanism, since kinematic relationship between joints and linkages for the kinematic chains are expressed as line vectors and block diagrams. Here, positional error and limit values of movement ranges of the stage are evaluated by using the SimMechanics. The validity of the kinematic characteristics model was compared with theoretical kinematic analyses for the 3-DOF stage.
-
A modeling method for the modal analysis of a multi-packet blade system having tapered cross section undergoing rotational motion is presented in this paper. Blades are idealized as tapered cantilever beams that are fixed to a rotating disc. The stiffness coupling effects between blades due to the flexibilities of the disc and the shroud are modeled with discrete springs. Hybrid deformation variables are employed to derive the equations of motion. To obtain more general information, the equations of motion are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters including tapered ratio and the number of packets as well as blades on the modal characteristics of the system are investigated with some numerical examples.
-
Since thickness deformation and lateral deflection often occurs during the collision of flexible bodies, they should be considered simultaneously in the impact analysis. The thickness deformation, however, cannot be considered in beam/shell theory since the thickness is assumed to be constant in the theory. So, solid elements are employed to estimate the thickness deformation. However, the CPU time increases significantly if solid elements are employed. In the present study, a modeling method for the impact analysis of a flexible body employing Hertzian contact theory is presented. The efficiency and the accuracy of the modeling method are discussed with some numerical examples.
-
A nano-imprinting stage has been widely used in various fields of nano-technology. In this study, A 4-axis nano-imprinting stage is modeled with using the 3D-CAD Tool. Structural components such as an upper-plate, bearings and cross-roller-guides are modeled with finite elements to analyze flexibility effect during the precision stage motion. In addition, Dynamic analysis is executed to reproduce actual motion of 4-axis nano imprinting stage.
-
Heo, Wook;Kim, Seock-Hyun;Park, Doo-Yeon;Kim, Jung-Han;Lee, Youn-Bok;Kim, Do-Shik;Choi, In-Su 850
In the motorized retractor of the smart seat belt system, anti-overload clutch is a very important element to prevent the excessive belt tensional force. Anti-overload clutch is the essential device to protect drivers from chest damage by the excessive belt tension. It generates slipping motion under excessive webbing moment and the belt tensional force is limited below critical value. In this study, slipping mechanism in the antioverload clutch is investigated by analysis and experiment. On the prototype model, finite element analysis is performed to identify the slipping condition and to determine the critical load. Analysis result is compared with the experimental result and the validity of the analysis model is verified. The purpose of the study is to provide the analytical background for the systematic design of the anti-overload clutch mechanism. -
In a railway vehicle, contact between wheel and rail is a peculiar characteristic and variations of wheel and rail profile influence on the dynamic characteristics of railway vehicle. Thus the variations of the wheel and rail profile are very important in railway dynamics. Recently a research relating to active steering to improve the curving performance of vehicle is progressing actively at home and abroad. In this field, a pre-study for the wheel/rail contact geometry is needed and especially the variation of the wheel/rail contact geometry with wheel wear is the key design parameter to develop the controller of the active steering bogie. In this paper, we have experimentally studied to analyze the variation of the wheel/rail contact geometry with wheel wear as a pre-study to develop the active steering bogie for electric multiple unit (EMU). For this, we have made an experiment with EMU operating in curving area. We have measured the wear profiles of the wheel of the test vehicle and analyzed the wheel/rail contact geometry with a mileage of the test vehicle. In experiment with test vehicle, we have got the useful data to design the steering controller of the wheelset.
-
In modern society, people tend to spend their time on various types of chairs. However, it is not easy for a designer to design a comfortable chair, because satisfaction with the chair depends not only on the quantitative elements such as size, but also on the qualitative element such as the user's feeling. To deal with these problems, there have been many studies on designing an ergonomics chair. In this paper, the hapticaided design (HAD) system was adopted to design the ergonomics chair. Based on the HAD system, the designer can experience whether the chair is comfortable or not through the haptic device, and also can modify the design parameters instantaneously. The haptic chair capable of controlling the design parameters in real time was proposed as a haptic simulator. The controllable parameters such as the seat height, reclining angle, stiffness of the backrest, and so on were selected based on the previous researches related to ergonomics chairs. It will reduce the development cost and time by replacing the process of making the real mock-up and prototype with the haptic chair.
-
Juryeonggu is a Cuboctahedral die that had used in ancient Korea. This Cuboctahedral is consisted of different two penal servitudes of 14 facepieces, but the probability distribution can appear equally so it can be usable as a die. In this paper, achieved research study about probability of a Cuboctahedral die that have quadrilateral and triangle preferentially to search Juryeonggu's probability calculation method. First, confirmed probability distribution through Multibody-dynamics analysis and verified probability distribution through several experiments. Finally, with this simulation data, achieved theoretical analysis about Cuboctahedral die occurrence probability by using the residual momentum energy.
-
The main objective of this paper is to control a trajectory tracking of the fish-mimetic robot by CPG (Central Pattern Generator), which is biological approach. CPG is biological neural networks that generate rhythmic movements for locomotion of animals, such as walking, running, swimming and flying. Animals show marvelous ability of autonomous dynamic adaptation for an unsteady fluid dynamic environment or various environments. So, we propose the 3-DOF CPG controller to track the trajectory of the fish robot in plane motion. The conformity of the proposed control algorithm is validated by simulation for a fish robot model, which is made by a commercial dynamic package.
-
When biped robots speed up to run and reduce speed to walk after running, it needs stable speed translation. This paper proposed simple speed translation using the modified LIPM (Linear Inverted Pendulum Mode). We can change stride and period time of a biped robot in some bounded sets with this propose algorithm. This method is simple and effective in simulation.
-
In this paper, the dependency of energy efficiency on the walking/running pattern and the walking/running period is analyzed though simulations of walk, trot and gallop. A quadruped animal has its own original features in the walking pattern and the walking period for adaptation to the environment. The robot model used in the simulations has three active joints and one passive spring-loaded joint at each leg, which is based on the actual quadruped robot, HUNTER (Hanyang UNiversity TEtrapod Robot), developed in the lab. Also included is the dependency of energy efficiency on the walking period in trot.
-
In This paper proposes the control algorithm for quadruped robots on irregularly sloped uneven surface. Body balance is important in stable running locomotion. Since the body balance is determined by the forces applied at the feet during touchdown phase, the ground reaction force is controlled for stable running. To control the forces at each foot, the desired force is generated. The generated desired force is compared with actual contact force, then, the difference between them modifies the foot trajectory. The desired force is generated by combination of the rate change of the angular and linear momentum at flight. Then the rate change of momentum determines each force distribution. The distribution of the force is carried out by fuzzy logic. The computer simulation is carried out with the commercial software RecurDyn
$^{(R)}$ . Dynamic model simulation program show that the stable running on the irregularly sloped uneven surface are accomplished by the proposed method. -
Measured sensor datum from a quadruped robotics is commonly used for recognizing physical environment information which controls the posture of robotics. We can advance the ambulation with this sensed information and need to synthesize various sensors for obtaining accurate data, but most of these sensors are expensive and require excessive load for the operation. Those defects can be serious problem when it comes to the prototype's practicality and mass production, and maintenance of the system. This paper suggests virtual sensor technology for avoiding previous defects and presents ways to apply a theory to a walking robotics through virtual sensor information which is trained with several kinds of actual sensor information from the prototype system; the general algorithm is initially based on the neural network theory of back propagation. In specific, we verified a possibility of replacing the virtual sensor with the actual one through a reaction force measurement experiment.
-
In this research uses a predetermined initial weight vectors of 1-dimensional string, gives the systematic input vector whose position best matches obstacles, and trains the weight vectors such that neurons within the activity bubble are moved toward or reverse the input vector. According to simulation results one can conclude that the modified neural network is useful tool for the global path planning problem of a mobile robot.
-
The linear motors are easily affected by load disturbance, force ripple, friction, and parameter variations because there is no mechanical transmission to reduce the effects of model uncertainties and external disturbance. For highspeed/high-accuracy position control of a linear-motor-driven two axes, a nonlinear adaptive controller including a cross-coupling algorithm is designed in this paper. The nonlinear effects such as friction and force ripple are estimated and compensated. An enhanced approach for cross-coupling algorithm is proposed to effectively improve the biaxial contour accuracy with the closed-loop stability. The proposed controller is evaluated through the computer simulations.
-
The wheel radiation noise characteristic of Korean tilting train(Hanvit 200) on curved rail under the field test conditions is analyzed in this paper. The test railroad track was selected from Seodaejon to Songjeongri in Honam line.
$5^{th}$ and$6^{th}$ car are decided to measure radiation noise level among a train of six cars. The test subject curve radius executed from R400, R500, R600, R700 and R800 segments. The speed of test trains when from R600 and R800 curves existing operation speed and speed up 20% of existing speed. On curved rail at the time of operation speed of Hanvit 200 trains from below 95km/h wheel radiation noise level at$94dBA{\sim}99dBA$ , the operation speed from between$100km/h{\sim}144km/h$ wheel radiation noise level at$100dBA{\sim}106dBA$ . -
Impact noise caused by the collision of bodies is difficult to estimate because of the complexity of impact phenomenon. In this study, impact noise is estimated using two different methods when the noise is caused by the vibration due to impact. First, impact noise is analyzed using impact analysis and boundary element analysis. Second, modal expansion technique is applied to the estimation of impact noise. Experiment is carried out to validate the analysis results.
-
In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. Based on the nominal model derived from mathematical model, the feedback type two-degree-of-freedom controller is designed and implemented. From simulation results, the disturbances including nonlinear friction torque, leakage flow and load force can be compensated and good positioning accuracy is obtained. It show that the proposed controller is effective.
-
As known generally, when permanent magnets whose poles are upward and downward in order, arranged into the circumferential direction rotate under the conducting plate, the rotating force acts on the plate as well as the repulsive force. If the magnetic field by the magnet wheel(the above rotating permanent magnets) is partially shielded, the magnet wheel over open region can be a linear induction motor. The distinct feature from induction motor is that the traveling magnet field is produced by the moving permanent magnet instead of ac current. Furthermore, a variation of the open region changes the direction of the thrust force. In this paper, we introduce a concept of the linear actuator using the magnet wheel. Under the above shielding condition, a few simulation results and its verification from a simple test setup are described.
-
In order to design a high-performance controller with excellent positioning and tracking performance, an optimal tuning method based on the integrated design concept is studied. DOBs, feedforward controllers and CCC are applied to control the bi-axial linear servomechanism. To derive accurate dynamic models of mechanical subsystems equipped with linear servos for the integrated tuning, system identification processes are conducted through the sine sweeping. An optimal tuning problem with stability, robustness and overshoot constraints is formulated as a nonlinear constrained optimization problem. Optimal gains are obtained through the SQP method. Experimental results confirm that both tracking and contouring errors are significantly reduced by applying the proposed controller and integrated tuning method.
-
The pulsation of a reciprocating type hydrogen compressor is occurred from the mechanism and this pulsation makes much noise and vibration. To reduce this pulsation, snubber is usually installed on that. To maintain the efficiency in the reciprocating type hydrogen compressor, the pulsation and vibration should be reduced. so it is necessary to research about the characteristic of pulsation and vibration. Therefore in this paper, the vibration characteristic of the snubber is analyzed in the base of optimized modeling condition through the flowing analysis of existing snubber. The prototype of reciprocating type hydrogen compressor is analyzed with numerical analysis. And making sure the present condition of hydrogen compressor through measurement of vibration and noise, and then it is established that the vibration characteristic data base on numerical analysis which will be develope.
-
To detect the failures in machine, the signals of current, vibration and acoustic emission are widely used in industry. And unexpected failures of gears are not only extremely damaging but also lead to economic losses. In this paper, to detect the misalignment occurred at between two gears in gearboxes, the signals of current, vibration and AE were measured at gearbox and motor power line. FFT(Fast Fourier Transform) was used for current and vibration signal analysis to find gear failure frequency. Especially, the envelop analysis and wavelet transform were applied for AE signal. Therefore, compared with the results of three kinds of signal, the possibility of earily detection by AE is identified or checked.
-
Dynamic response characteristics of a beam undergoing impulsive force are investigated using the wavelet transform method in this study. When an impulse is applied to an arbitrary position of a beam, it will generate a structural deformation wave. The characteristics of the wave are changing in the domain of time and space. The maximum amplitude of each natural frequency mode and the time to reach the maximum amplitude are obtained in this study. The effects of the location of impulse on the variations of the dynamic characteristics is also investigated.
-
In this study, vibrational characteristics of two nano-imprinting stages is analyzed and compared with respect to the methodology to support the upper-plate of the stage. The first type of the stage has three supporters at each corners of the stage and one thrust bearing at the center of the stage. The other type of the stage has four supporter in each corner of the stage without a thrust bearing. The FEM software with flexible modeling is used for the normal mode analysis. The result depicts the difference of vibrational characteristics caused by the difference of support methods. The design criteria for the precision nano-imprinting stage is also discussed.
-
In this paper, an impulse of an industrial chop Saw is identified by experimental method and the impulse is reduced by structural modification. For the impulse identification, vibration signals are measured by an accelerometer when the chop saw is operating. From some experiments, it is found that the impulse occurs when there is slip between spindle and the wheelwasher and contact area is small between the wheelwasher and cutting discs. The design of the wheelwasher for optimization is performed by the FEM and experiments and the prototype is manufactured. It is verified that considerable amount of impulses are reduced by the structural modification.
-
In this paper, the purpose is to investigate the stability and variation of natural frequency of a Timoshenko cantilever beam subjected to Subtangential follower force and tip mass. In addition, an analysis of the flutter instability(flutter critical follower force) of a cantilever beam as slenderness ratio is investigated. The governing differential equations of a Timoshenko beam subjected to an end tangential follower force is derived via Hamilton;s principle. The two coupled governing differential equations are reduced to one fourth order ordinary differential equation in terms of the flexural displacement. Finally, the influence of the slenderness ratio and tip mass on the critical follower force and the natural frequency of a Timoshenko beam are investigated.
-
This paper presents the free vibration analysis of a circular plate with a concentric square hole. The present problem deals with the numerical calculation of the natural frequencies and mode shapes of vibration of the structure by means of Independent Coordinate Coupling Method (ICCM). In this study, the boundary condition is the edge of the square hole is free and the outer circular plate is simply supported. Due to the geometric abnormality, this analysis does not permit an exact solution. Since the ICCM employs coordinate systems corresponding to each domain independently, the kinetic and potential energy expressions necessary for the Rayleigh-Ritz method can be easily obtained. Lastly, the kinematic relation is imposed. In this way, the eigenvalue problem can be easily set up. The numerical results show the efficacy of the ICCM and changes in natural frequencies and modes due to the square hole size.
-
This study concerned on the critical speed due to hunting and snake motion train to ensure the stability. First, the critical speed was calculated by using a numerical model, and calculated the critical speed of the vehicle through the simulation with the use of ADAMS/RAII. Also, the snake motion was confirmed through a modal analysis and running simulation. The calculated results, show that the rail irregularity becomes the influential factors of the stability since it is the direct source of excitation of the vehicle.
-
A bi-modal tram can travel in not only dedicated way but also road so as to reduce construction costs and increase vehicle operation efficiency, whose passenger capacity is 2,500 to 7,000 persons/direction/hour. A bi-modal has an electronic guidance system that knows the location and route of the vehicle, and uses magnetic markers in the road surface for reference. Since a bi-modal tram will be operated in the downtown area, there is some possibility that strong wind occurred between high-rise buildings can produce sudden lateral movement (displacement) of the vehicle to influence its automatic operation controlled by electronic guidance system. For bi-modal tram in the automatic operation mode, lateral movements occurred by strong wind were calculated and analyzed in the dynamic model developed by using the ADAMS. Some useful relations among vehicle speeds, wind speeds, and lateral behaviors were discussed in this paper.
-
An estimation of high-order damping in flexible multibody dynamic simulation is introduced in this paper. The suggested damping model based on the experimental modal analysis leads to more accurate correlation results comparing to the traditional linear damping model because it directly uses the modal parameters of each mode achieved from experiment even high frequency modes. The modal parameters until the 5th mode are extracted from the experimental modal testing of the flexible beam using a high speed camera. And using the measured damping ratio and natural frequency until the 5th mode, the generic damping model is constructed. Then, the ANCF (absolute Nodal Coordinate Formulation) simulation results are compared to experimental results until the 5th mode.
-
During the ship's construction process, most high place workings have been carried out by human power, like welding, grinding and so on. Because of the ability to relieve human beings from these, the need of developing a hull-plate moving robot has been rising. This paper describes a hull-plate moving robot, using magnet modules as the adhesive method. Magnet modules maintain the magnetic force between hull-plate and magnets constantly. So that allows the robot to perform movements on the curved plate without the loss of adhesive force. The robot consists of driving motors, control system and magnet modules. The performance of the robot is verified on the curved plate.
-
Aspheric polymer lens fabrication using isothermal compression molding is presented in this paper. Due to increasing definition of an image sensor, higher precision is required by a lens which can be used as a part of an imageforming optical module. Injection molding is a factory standard method for a polymer optical lens. But achievable precision using injection molding has a formidable limitation due to the machining of complex mold structure and melting and cooling down a polymer melt under high pressure condition during forming process. To overcome the precision requirement and limitation using injection molding method, isothermal compression molding is applied to fabrication of a polymer optical lens. The fabrication condition is determined by numerical simulations of temperature distribution and given material properties. Under the found condition, the lens having a high precision can successfully be reproduced and does not show birefringence which results often in optical degradation.
-
Hydro-mechanical forming process has numerous advantages compared to those of a conventional deep drawing process such as an excellent surface quality and low costs of dies. In fact, Hydro-mechanical forming is a desirable forming process for producing complex parts in automotive body components, and it is an excellent candidate for the forming process of aluminum panels. In this research, Hydro-mechanical forming process with a cross shape punch has been studied for Al-Si-Mg alloy sheets. Finite element analysis by LS-Dyna has predicted the deep drawing depth of the aluminum sheets, and the experiment has confirmed that result. Put Abstract text here.
-
The rapid wear rate of cutting tools due to high cutting temperature is a critical problem to be solved in machining of hardened steel. Application of cutting fluid influences the performance of machining because of its lubrication and cooling actions. But, the environmental concerns call for the reduced use of cutting fluids in machining operations. Near-dry machining such as minimum quantity lubrication is regarded as one of the solutions to this difficulty. In the present work, cutting fluid was applied as a high velocity jet at the machining zone continuously at an extreme low rate using a fluid application system developed namely Electro Static Lubrication (ESL) during drilling of hardened steel. The performance of ESL has been compared with that of dry and MQL (minimum quantity lubrication) machining.
-
In this study, effective methods for reliability estimation and reliability-based design optimization(RBDO) are proposed using kriging metamodel and genetic algorithm. In our previous study, we proposed the accurate method for reliability estimation using two-staged kriging metamodel and genetic algorithm. In this study, the possibility of applying the previously proposed method to RBDO is examined. The accuracy of that method is much improved than the first order reliability method with similar efficiency. Finally, the effective method for RBDO is proposed and applied to numerical examples. The results are compared to the existing RBDO methods and shown to be very effective and accurate.
-
This paper represents a study on the conceptual design of new automatic bicycle transmission. The gear change in a commercial bicycle is carried out by moving the chain between sprockets. By the use of a multiple sprocket for speed change the power loss and transmission shock may occur. To solve the problem of bicycle transmission, the improved solution was derived by the technical contradiction matrix of TRIZ. The conceptual solution is one sprocket which replaces the function of multiple sprockets and adapts actively to the pitch of chain. And it was confirmed to be an adequate design through the Independence Axiom of design axiom.
-
The mount type HVAC control system is a type of an HVAC control system which is installed between a ceiling and ceiling boards of a room to control room temperature. Although the device is quite popular, design is conducted by a conventional way where engineering intuition and experiences are utilized. It is found that the design process is fairly inefficient and time-consuming because there are a lot of feedbacks. The axiomatic approach is used to investigate the design characteristics of the mount type HAVC control system and the Independence Axiom is utilized for the investigation. The Overall hierarchy is established up to the level of parts. It is found that the current design has many coupled and redundant aspects. The hierarchy is reorganized based on the Independence Axiom and a new design process is found. To exploit the new design process in practice, a design manual is made.
-
Recently, the sludge suction collector is preferred rather than the scraper type sludge collector due to enhancement of the clarifier efficiency. The sludge suction collector is usually operated by the user's experience without any scientific and technical consideration. There are many factors that should be considered for higher quality of discharged water and stabilized flow in the rectangular sludge suction collector but, the optimal design on the inflow channel and orifices connecting with the inflow channel is needed for similar flow rates at the orifices. The 4 cases of channel geometry are considered and mass flow rates of each case at the orifices are evaluated using Computational Fluid Dynamics applied VOF(Volume of Fraction) model.
-
Hypoid gears are widely used in rear drive and 4WD vehicle axles. Investigation of their sensitivity to deflections is one of the most important aspects of their design and optimization procedures. The deflection test is performed in the actual gear mounting using completely processed gear. This test should cover the full operating range of gear loads from no load to peak load. Under peak load the contact pattern should extend to the tooth boundaries without showing a concentration of the contact pattern at any point on the tooth surface. Transmission error is tested on an axle assembly triaxial real car load condition.
-
Difficulties in developing process of Liquid Crystal Display(LCD) products such as frequent design modifications, various design requirements, and short-term development period bring on the need of integrated design approach that is efficient and easy to handle. Back Light Unit(BLU) of the LCD, which drastically affects the optical performance of LCD products, is divided into in-coupling part and out-coupling part. Serration of the in-coupling part flattens the light received from point light sources and dot pattern of the out-coupling part regularizes the light sent to screen. Therefore, the optical performance of a LCD product is largely influenced by the shape of serration and the arrangement of dot pattern. In this research, a new design approach which enables to improve the optical performance of LCD products and overcome the prementioned difficulties in developing process of LCD products is proposed. The shape of serration is parameterized to 3 parameters and out-coupling part is partitioned into 10 partitions to apply the optimization technique to this problem. 3 parameters for the shape of serration and densities of 10 partitions are used as design variables in the design optimization. Optical simulation tool named SPEOS is used to evaluate the optical performance of the LCD product. Since the optical simulation uses the random ray tracing technique, numerical noise may possibly be included in the simulation process. To solve the problem caused by numerical noise, the PQRSM which can stably find the solution of the noise problem is used in this research.
-
An application of CSG (Constructive Solid Geometry) modeling technique in Machining Simulation is introduced in this paper. The current CSG model is based on z-buffer CSG Rendering Algorithm. In order to build a CSG model, frame buffers of VGA (Video Graphic Accelerator) should be used in term of color buffer, depth buffer, and stencil buffer. In addition to using CSG model in machine simulation Stock and Cutter Swept Surface (CSS) should be solid. Method to create a solid Cuboid stock and Ball-end mill CSS are included in the present paper. Boolean operations are used to produce the after-cut part, especially the Difference operation between Stock and CSS as the cutter remove materials form stock. Finally, a small program called MaSim which simulates one simple cut using this method was created.
-
Representing a complex, three-dimensional shape, such as an automobile, requires a large amount of CAD data consisting of millions of approximated discontinuous points, which makes it difficult or even impossible to efficiently optimize the entire shape. For this reason, in this paper, function based design method is proposed to optimize the external shape of an automobile. A vehicle modeling function was defined in the form of a Bernstein polynomial to smoothly express the complex 2D and 3D automobile configurations. The sub-sectional parts of the vehicle modeling function are defined as section functions through classifying each subsection of a box model. It is shown that the use of the vehicle modeling functions has the useful advantages in an aerodynamic shape optimization.
-
A lens system of a camera module for mobile phones is comprised of the composition and design of various shapes of lens. To improve responses such as the modular transfer function (MTF), a lens system should always be constructed by considering uncertainty that can be caused by manufacturing and assembly error. In this study, tolerance optimization using the Latin Hypercube Sampling (LHS) technique is performed. In order to reduce the computational burden of the tolerance optimization process and decrease the influence from numerical noise effectively, we use the Progressive Quadratic Response Surface Modeling (PQRSM), which is one of Sequential Approximate Optimization (SAO) techniques. Using this method, we achieved optimal tolerance for each lens and obtained reliability for satisfying user‘s requirements. In addition, through the design process the manufacturing and assembly cost of a lens system was reduced.
-
Tool condition monitoring (TCM) is crucial for improvement of productivity in manufacturing process. However, TCM techniques have not been applied to monitor tool failure in an industrial gear shaving application. Therefore, this work studied a statistical TCM method for monitoring gear shaving tool condition. The method modeled the shaving process using beta probability distribution in order to extract the effective features. Modeling includes rectifying for converting a bi-modal distribution into a unimodal distribution, estimating parameters of beta probability distribution based on method of moments. The usefulness of features obtained from the proposed method was evaluated and discussed.
-
An engine for marine propulsion and power generation consists of several cylinder liner-piston sets. And the oil groove is on the cylinder liner inside wall for the lubrication between a piston and cylinder. The machining process of oil groove has been carried by manual work so far, because of the diversity of the shape. Recently, we developed an automatic grinding robot system for oil groove machining of engine cylinder liners. It can covers various types of oil grooves and adjust its position by itself. The grinding robot system consists of a robot, a machining tool head, sensors and a control system. The robot automatically recognizes the cylinder liner's inside configuration by using a laser displacement sensor and a vision sensor after the cylinder liner is placed on a set-up equipment.
-
During the manufacturing process of a propeller for a large scale commercial ships, several times of turn-over process should be required. Propeller turn-over is a indispensible process but not easy because of its heavy weight and complicate shape. Recently, we developed a new type of turn-over system for a large scale propeller. The system consists of turning roller devices, sliding transfer system, clamping devices and so on. In this paper, we described the design process which includes mechanical structure design, dynamic analysis and assembly with a laser tracker.
-
This paper presents the electro-luminescence (EL) display lamp which is patterned on a curved surface by the pad printing method. The printing methods, including the gravure, screen, flexo, inkjet, and pad printing, have an advantage of one-step direct patterning. However, in general, the printing and semi-conductor process, except pad printing method, cannot be applied for patterning on a curved surface. Thus, in this paper, we used pad printing method for patterning an EL display lamp on a curved surface. The EL display lamp consists of 5 layers: Bottom electrode; Dielectric layer; Phosphor; Transparent electrode; Bus electrode. Finally, we printed EL display lamp on a dish, which has a radius of curvature 80mm. The EL display lamp was driven at AC 200V of 1kHz.
-
Roll-to-roll based manufacturing plays an important role in producing devices at high speed with lower production cost in printed electronics and publishing industry. Web lateral control is one of the most important factors in improving the quality of product and contributes a considerable point in making devices at micrometer-level accuracy. In recent years, most algorithms proposed for web lateral control base on the Shelton‘s model for designing the feedback control system using the PI controller. Experimental results showed that the existing models do not fully describe the characteristics of the lateral dynamics for some typical operating conditions and so result in poor control algorithms. In this paper, a new lateral control algorithm is proposed for web lateral control system based on back-stepping approach. The outcome of this study proves the reliability throughout simulation results in Matlab/Simulink and comparison with the algorithms based on the existing results.
-
To increase the ink transfer rate in the micro-gravure-offset printing, the liquid transfer process between two separating plates is investigated. During the liquid transfer process, in which one plate is fixed and the other one moves vertically, a sessile droplet is separated into two droplets. The volume ratio of the two droplets depends on the contact angles of the two plates. In a numerical study of the ink transfer processes, liquid transfer between two parallel separating plates and between a trapezoidal cavity and an upward moving plate are simulated, as models of the printing of ink from the offset pad onto the substrate and the picking up of ink from the gravure plate by the offset pad, respectively. Also, in experimental study, to obtain various surface contact angles, chemical treatment, plasma treatment, and electrowetting- on-dielectric (EWOD) surface are considered. The transfer rate between two plates is calculated by analyzing the droplet images. From the results, the optimal surface contact angles of the units of the micro-gravure-offset printing can be characterized.
-
For the current display process, the innovative micro pattern fabrication process using semiconductor process should be developed, which requires the expensive equipment, the limited process environment and the expensive optic-sensitive material. The effort of process innovation during past several years ends up the limit of cost reduction. The existing ink jet technologies such as a thermal bubble ink jet printing and a piezo ink jet printing are required to shorten the nozzle diameter in order to apply to the micro pattern fabrication. In this paper, as one way to cope these problems the micro pattern equipment based on the electrostatic ink jet has been developed and carried out some experiments.
-
The objective of this paper is to investigate into the influence of the injection conditions on the insert deformation and the wall thickness of the injection part using the three-dimensional injection molding analysis. Full three-dimensional insert model was added to the injection molding analysis model to consider the effects of insert deformation during the injection molding process. In order to obtain the optimum injection molding condition with a minimum insert deformation, degree of experiments were utilized. From the results of the analyses, it was shown that the optimum injection condition is injection time of 1.6 sec, injection pressure of 30 MPa and packing time of 15 sec. In addition it was shown that the wall thickness is approached to target thickness when the core deformation is considered in the injection molding analysis.
-
In the hot forging process, The forging defects that are caused by metal were strain, temperate, and inclusion. In this paper, the computer simulation analyzed the effective plastic strain and temperature behaviors. The quantitative analyses which proposed the effective mold design of S/CAM shaft was executed. The parameters of forging shape that affected on the optimize conditions that was calculated with simple equation were investigated. it is expected that the developed analysis model and design technique would greatly contribute to the drum brake optimal design considering temperature affected and material behaviors. This development could save more than 20% of production cost and reduced failure rate to more than 30%. By improving the life span of mold from 15,000 to 25,000, financial difficulty of company imposed on a mold manufacture could be overcome.
-
High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a noncontact procedure. It has been recently applied to the injection molding of thin-walled parts or micro/nano structures. Though the induction heating has an advantage in terms of its rapid-heating capacity on the mold surface, it still has difficulty in efficient mold temperature control due to the restriction of an induction coil design suitable for the given mold shape. The present study proposed a localized mold heating method by means of selective use of mold material. For localized induction heating, an injection mold composed of ferromagnetic material and paramagnetic material is used. The electromagnetic induction concentrates on the ferromagnetic material, from which we can selectively heat for the local mold elements. The feasibility of the proposed heating method is investigated through an experimental measurement in terms of the heating efficiency on the localized mold surface.
-
Thin-wall injection molding is associated with many advantages, including increased portability, the conserving of materials, and the reduction of the molding cycle times. In the application of the thin-wall molding, a considerable reduction of the effective flow thickness results in filling difficulty. High-frequency induction is an efficient way to overcome this filling difficulty by means of heating the mold surface by electromagnetic induction. The present study applies the induction heating to the injection molding of thinwalled micro structures with high aspect ratio. The feasibility of the proposed heating method is investigated through a numerical analysis. The estimated filling characteristics of the micro-features are investigated with variations of mold temperature and part thickness, of which results are also compared with experimental measurements.
-
We injection molded a plate with micro surface features including micro prizms & micro channels patterns on its surface and investigated the replication of the micro features depending on the mold temperature which is one of typical process parameters. The size of the patterns were 8um, 10um, 15um of prizm features & 15um, 30um, 45um of channel features. The size of the plate is about
$400mm{\times}400mm$ and the thickness is 1mm of plate. the repliction of the mucro features turned out to depend on the mold temperature and also the location on the plate. The pressure and the feature of the melt in the cavity were also measured in real-time for the investigation on the micro feature replication. -
The sludge grown up in steam generators of nuclear power plants shortens the life-cycle of steam generators and reduces the output of power plants. So KHNP(Korea Hydro and Nuclear Power), the only nuclear power utility in Korea, removes it periodically using a steam generator lancing system during the outage of plants for an overhaul. KEPRI(Korea Electric Power Research Institute) has developed lancing systems with high pressured water nozzle for steam generators of nuclear power plants since 2001. In this paper, the design of a partial inter-tube lancing system for model F type steam generators will be described. The system is actuated without a DC motor inner steam generators because the motors in a steam generator make a trouble from high intensity of radioactivity as a break down.
-
The helicopter rotor system generates lift, thrust, maneuvering force and moment to the helicopter with the torque and pitch control force transferred from the main rotor hub/control. And the tail rotor system generates the thrust for yaw axis control of the helicopter with the torque and pitch control force transferred from the tail rotor hub/control. Ground whirl test shall be performed to verify the compliance of requirement performance test and dynamic test of rotor blade and hub/control. This paper describes a design of whirl tower test facility for helicopter rotor system test and evaluation. Design results are summarized and compared with design requirements.
-
도시철도의 환승체게 개선과 차량의 이용편이성 향상 및 고유가 등으로 도시철도 이용객수는 해마다 증가하고 있다. 이렇게 많은 승객이 이용하는 차량실내는 미세먼지, co2등의 오염물질이 증가하여 이용승객의 건강을 해치고 있는 실정이다. 이를 해결하기 위해 새롭게 개발되는 차세대전동차에 수치해석 기법을 적용하여 설계단계에서 덕트 및 실내기기배치 등을 모델링하여 열유동 및 쾌적성을 해석하여 국제기준과 비교하여 그 기준을 만족하는 차량임을 확인하였다.
-
Converting technology has developed to print information for the decades. Recently, this technology (like gravure, gravure-offset) is rising as an alternative way for mass production of printed electronics such as RFID, solar cell. For the width of printing line is under 10 microns, registration error should be minimized less than several microns. Tension disturbance is main cause of registration error and this should be minimized before the substrate is transported into printing zone. With PI controller, it is possible to suppress the disturbance within 2% of operating tension. But register error appears more than 10 micron using PIcontroller considering noise. So LQG controller is needed as an alternative control method. In this paper, the comparision of PI and LQG controller in the converting machine including measured noise and tension disturbance is presented. It is shown that the LQG controller is more suitable for precision tension control in printed electronics.
-
Parameter analysis has been performed for an equal channel angular process. The processing variables such as channel configuration, friction coefficient, and ram speed were investigated by means of the magnitudes and distributions of effective plastic strain analysis through the deformation. The materials considered were pure aluminum and titanium. Here firstly, a finite element implementation by using the commercial ABAQUS software was carried out for both the aluminum and titanium materials based on the L-channel configuration. The experimental investigation then has been conducted using the obtained data. Finally, the ability of robust metals which can be produced by the optimized ECAP has been discussed by the appropriate parameter analysis.
-
Nonlinear dynamic analysis is generally used in automobile crash analysis and structural optimization considering crashworthiness uses the results of nonlinear dynamic analysis. Automobile crash optimization has high nonlinearity and difficulty in calculating sensitivity. Recently the equivalent static load (ESL) method has been proposed in order to overcome these difficulties. The ESL is the static load set generating the same displacement field as the nonlinear dynamic displacement field at each time step in dynamic analysis. From various researches regarding the ESL method, it has been proved that the ESL method is fairly useful. The ESL method can mathematically optimize a crash optimization problem through nonlinear analysis and well developed static optimization. The ESL is applied to nonlinear dynamic structural optimization of the automobile frontal impact problem. An automobile bumper is optimized. The mass of the structure is minimized while some constraints are satisfied.
-
This study provides how the Dimension Reduction (DR) method as an efficient technique for reliability analysis can acquire its increased efficiency when it is applied to highly nonlinear problems. In the highly nonlinear engineering systems, 4N+1 (N: number of random variables) sampling is generally recognized to be appropriate. However, there exists uncertainty concerning the standard for judgment of non-linearity of the system as well as possibility of diverse degrees of non-linearity according to each of the random variables. In this regard, this study judged the linearity individually on each random variable after 2N+1 sampling. If high non-linearity appeared, 2 additional sampling was administered on each random variable to apply the DR method. The applications of the proposed sampling to the examples produced the constant results with increased efficiency.
-
The validation technique is classified with two methods whether to demand of additional experimental points. The method which requires additional experimental points such as RSME is actually impossible in engineering field. Therefore, the method which only use experimented points such as the cross validation technique is only available. But the cross validation not only requires considerable computational costs for generating metamodel each iterations, but also cannot measure quantitatively the fidelity of metamodel. In this research we propose a new validation technique for representative metamodels using an variance of metamodel and confidence interval information. The proposed validation technique computes confidence intervals using a variance information from the metamodel. This technique will have influence on choosing the accurate metamodel, constructing ensemble of each metamodels and advancing effectively sequential sampling technique.
-
This paper represents a study on design hypothesis to improve properties of a product. The functional requirements and function structure of various technical products are analysed. From the above analysis we could formulate one hypothesis. This hypothesis also satisfies basic rules clarity, simplicity and safety that are required in all design cases. The hypothesis says that functional requirements is refined to improve and if there are components which have the same function, they can be integrated into one component and improved. A one-handed faucet was developed by applying the above hypothesis to a two-handed faucet. The design of heat exchange tester was be improved successfully through the hypothesis.
-
Insulators which are used in the domestic electrical industries are mostly depended on importation from some advance countries. Even though insulators which are made of ceramic material have been mostly used domestically, the ratio of usage on composite insulators is recently being increased because of difficulties in manufacturing and high cost regarding ceramic stuffs. In this research, we are trying to develop the composite insulators which are very efficient in insulation regardless of the matter of weight. Even though the technique of manufacturing composite insulator are quite generalized worldwide at the moment, one of the most important issue is to keep security on the know-how that an ingredient of insulated material named 'SF6 gas' is included. Therefore, The aim of this paper is to improve the bonding force and air tight property between two components of composite insulator, Flange and FRP Tube.
-
In this paper, a versatile multi-objective optimization concept for fatigue life prediction is introduced. Multi-objective decision making in engineering design refers to obtaining a preferred optimal solution in the context of conflicting design objectives. Compromise decision support problems are used to model engineering decisions involving multiple trade-offs. These methods typically rely on a summation of weighted attributes to accomplish trade-offs among competing objectives. This paper gives an interpretation of the decision parameters as governing both the relative importance of the attributes and the degree of compensation between them. The approach utilizes a response surface model, the compromise decision support problem, which is a multi-objective formulation based on goal programming. Examples illustrate the concepts and demonstrate their applicability.
-
Bridge is Most from stay of Gantry structures part. In compliance with oneself weight of the bridge deflecting, this occurs drops the location precision of the work tool. Also accelerative at the time of gives a serious load to Y axial motors which transfer the bridge damages. The motor with high-speed transfer of location control which is accurate makes disrupt. The malleability of the bridge to maintain consequently and necessary to minimize a weight. This paper the structural FEM interpretations of the stone and the aluminum alloy with the material by which will be used in the bridge and static deflected and a candle precise plane X-Y stage optimal design with character the interpretation result.
-
An efficient sequential optimization approach for metamodel was presented by Choi et al [6]. This paper describes a new approach of the multilevel optimization method studied in Refs. [5] and [21-25]. The basic idea is concerned with multilevel iterative methods which combine a descent scheme with a hierarchy of auxiliary problems in lower dimensional subspaces. After fitting a metamodel based on an initial space filling design, this model is sequentially refined by the expected improvement criterion. The advantages of the method are that it does not require optimum sensitivities, nonlinear equality constraints are not needed, and the method is relatively easy to understand and use. As a check on effectiveness, the proposed method is applied to a classical cantilever beam.
-
Design is important in the IT, digital appliance, and auto industries. Aesthetic and art images are being applied for better design satisfaction of the products. Various artistic image patterns are used to satisfy demand of design, but it takes much lead-time and effort to implement them for making dies and molds. In this paper, a hybrid reverse engineering method generating accurate 3D engraving models from 2D art images is proposed through image processing, 3D reconstruction, and NURBS interpolation methods. In order to generate the 3D model from the 2D artistic image, cloud points with z-depth are extracted according to intensity values of the image. An adaptive median filter and harmonic filter are used to obtain the intensity values accurately. NURBS surfaces are generated through the interpolation of the cloud points. Performance of the developed system is to be confirmed through the realization of Mona Lisa and Golden Gate Bridge.
-
Electro-pneumatic servo valve is an electro-mechanical device which converts electric signal into pneumatic flow rate or pressure. In order to improve the overall performance of pneumatic servo systems, electro-pneumatic servo valves are required, which have fast dynamic characteristic, no air leakage at null, and can be fabricated at a low-cost. The first objective of this research is to design and fabricate a new electro-pneumatic servo valve which satisfies the above-mentioned requirements. In this paper, we has been modeled as a system consisting of coupled electro-mechanic and mechanical subsystems. The appropriateness of the model has been verified by simulation. The simulation model resolves the valve body motion and the solenoid current at high accuracy. Also, we are calculate the displacement of spool and computed results show winding currents, magnetic actuator force, flux density line, displacement, velocity, back EMF, eddy current etc.
-
The aim of this paper is to perform a finite element analysis that will have the ability to predict the seal performance characteristics, such as deformation, contact load and friction and also is to provide a means of potential seal designs, which can reduce the time and cost of designing the performance of the seal. The material property tests of elastomer seal are performed to obtain the hyperelastic properties and The Mooney-Rivlin constants are determined from these test results. A 2D modelling of the seal cross section is performed to simulate the contact behavior between the seal on the piston and the cylinder bore under operation conditions. The deformation behavior, contact load and friction of an elastomer seal is analyzed by a finite element method which performs three analytic phases of interference fit, the variations of pneumatic pressure and piston movement under the operational conditions.
-
In this paper, analysis of pressure and flow characteristics have been performed with a servo valve. A number of servo valve have been used in various applications including the inserting device, bearing transportation and welding machine. By analysis of flow and pressure gradient, technology can be obtained about optimal simulation of high response servo valve for competitiveness. Spool displacement and ratio of inlet/outlet pressure can give big effects to flow and pressure inside servo valve.
-
In this paper, we designed sandwich type pressure regulator for air pressure control system. As a result of research, we obtained several important conclusions. First, we decided theory of poppet valve and relief valve which are used in sandwich type pressure regulator, and then designed prototype of pressure regulator. Second, we organized circuit diagram of dual pressure regulator of air pressure control system.
-
Of all of pneumatic components utilized in the make up of pneumatic circuits on either automatic assembly machine or industrial equipment, the pneumatic cylinder is more oriented toward being a structural as well as a pneumatic member. The structural design must be based to a large degree on the end of application of the cylinder on the equipment it is operating. In this paper, design studies of a double-acting pneumatic cushion type cylinder with low-friction and high-speed driving have been developed. Of interest here is to investigate the structural analysis of cylinder tube, piston rod, end cover, and to analyze the buckling of piston rod. Also, a relief valve type cushion mechanism is considered. This cushion mechanism is found to be adequate under a high-speed driving of pneumatic cylinders.
-
Through the optimization design of the pneumatic components it leads the energy efficiency increasement and resources saving. Also it effects on the high speed operation, low speed operation, low weight, and complexity of pneumatic systems. In this paper the development of the software will be described based on Object-Oriented technology, which will provide function for development of pneumatic system without any deep knowledge about pneumatic system.
-
The tempering and magnetic annealing are used to improve the soft magnetic properties such as initial permeability coercivity and core loss of the KM35F alloy. The first heat treatmentis performed at the temperature less than the curie temperature of the KM35F alloy to remove the thermal stress for few hours in nitrogen atmosphere. The second stage heat treatment is performed the magnetic annealing at
$500{\sim}800^{\circ}C$ for few hours in nitrogen atmosphere, and then quenching to room temperature in absence of oxygen. Finally, magnetic properties of the thermally treated KM35F alloy are investigated for application as a soft magnetic material of the ISO solenoid valve core and plunger. -
This paper shows a perfonnance analysis for pneumatic servo cylinder. The pistons without seal have partly cylindrical and conical shapes. 2 dimensional Reynolds equation and FD(finite differential) numerical techniques are utilized for the perfonnance analysis. The relationship among self-centering forces and leakage flows are investigated. Also, optimal design values for a servo cylinder are presented. A prototype of servo cylinder which had rod bearing with four pockets, five pockets, and six pockets was manufactured respectively.
-
In this study, A special quality analysis and experiment for low power consumption type pneumatic ISO Solenoid valve was performed. And flow characteristics of the ISO Solenoid valve by stroke change was numerically investigated. As a result, it is shown that magnetic force(2.4N) is exerted enough to move poppet with 0.3mm stroke with 0.01 seconds of response time, and that there is no magnetic force emitted by yoke.
-
Roll to roll (R2R) system, known as 'web processing', is the process of producing these electronic devices on a roll of flexible plastic. With the need of improved performance and productivity in R2R industry, effective control and on-line supervision for web quality is essential. In this report, we present a system for on-line measurement of wrinkles, one of defects incurring due to compressive stresses developed in the web. This system is able to capture an image generated when a well defined line shape laser beam passes through a transparent web. The system calculates 3D shape information, including the height of the wrinkle on the web, and displays the images for the shape information of the web in real time. By using area scan camera and machine vision laser, this system takes more advantages of setting up as a simple and low cost system compared to the line scan camera systems that widely used in web manufacturing. Specific calibration method and analysis on the achievable accuracy will be discussed.
-
This paper presents an accelerated life test for burn out of tungsten filament of automotive halogen lamp. There are many failure modes and failure factors that associated with tungsten filament. But in this explain the dominant failure mode of tungsten filament is the bumout of the filament failure. At first, over voltage, high temperature, inrush current and vibration are selected as stress factors by using of two stage Quality Function Deploymeng(QFD). And we planed accelerated life test that has one factor(voltage) and three levels. By experiment it has absorbed that over voltage has an effect on the life of halogen lamp. Using ALTA programs, we estimated the common shpae parament of Weibull distribution, life-stress relationship and
$B_{100p}$ life. -
Electromigration is a one of a critical failure mechanism in microelectronic devices. Minimizing the thin film interconnections in microelectronic devices make high current densities at electrrical line. Under high current densities, an electromigration becomes critical problems in a microelectronic device. This phenomena under DC conditions was investigated with high temperature. The current density of 1.5MA/cm2 was stressed in interconnections under DC condition, and temperature condition
$150^{\circ}C,\;175^{\circ}C,\;200^{\circ}C$ . By increasing of thin film interconections, microelectronic devices durability is decreased and it gets more restriction by temperature. Electromigration makes electronic open by void induced, and hillock induced makes electronic short state. -
This study has explained about LED for BLU which is widely used in the kinds of display devices or lighting. It was shown that the open due to delamination were the dominant LED for BLU failure mode and mechanisms from failure analysis of LED samples. Then, we have defined failure as yellowing and 100% reduction of light output intensity of LED for BLU and acceleration factors as temperature and current in Accelerated Life Test(ALT). Finally, we have estimated the Weibull distribution, life-stress relationship, and accelerating factor is used by ALTA Software.
-
Recently LCD panels have becom very important components for portable electronics. In the high density interconnection material, ACF's are used to connect the outer lead of the tape automated bonding to the transparent indium tin oxide electrodes of the LCD panel. ACF consists of an adhesive polymer matrix and randomly dispersed conductive balls. In this study, we analyzed Failure Mode / Mechanism of ACF which is identified Conductive ball Corrsion, Delamination, Crack and Polymer Expansion / Swelling. In ALT(Accelerated Life Test), we select primary stress factors as temperature and humidity. As time passes by, an increase of connection resistance was observed. In conclusion, we have found that high temperature / humidity affects the adhesion.
-
The FPCB is used as the important component of the sliding mechanism of mobile phones. FPCB have been used as jumper cables(fixed wiring) in various types of circuits because of their flexibility and bending property. The dominant failure mode of the FPCB is open that was caused by fatigue. The fatigue is repeated whenever the sliding is open, so it is a mainly cause of FPCB fatigue. We examined the bending-fatigue lifetime of FPCB. we focused on observing the contact resistance degradation of FPCB of mobile phones according to different test condition of bending strain. As a result, it has proved that lifetime decreased by increasing bending strain.
-
Electrostatic discharge(ESD) phenomenon is a serious reliability concern. It causes approximately most of all field failures of IC. To quality the ESD immunity of IC product, there are some test methods and standards developed. ESD events have been classified into 3 models, which are HBM, MM and CDM. All the test methods are designed to evaluate the ESD immunity of IC products. This study provides an overview among ESD test methods on ICs and an efficient ESD stress method. We have estimated on all pin combination about the positive and negative ESD stress. We make out the weakest stress mode. This mode called a worst-case mode. We proposed that positive supply voltage pin and I/O pin combination is efficient because it is a worst-case mode.
-
During the manufacturing and the service life of Au-Al wire bonded electronic packages, the ball bonds experience elevated temperatures and hence accelerated thermal diffusion reactions that promote the transformation of the Au-Al phases and the IMC growth. In this paper, the IC under high temperature storage (HTS) tests at
$175^{\circ}C,\;200^{\circ}C$ , and$250^{\circ}C$ are meticulously investigated. Thermal exposure resulted in the IMC growth, Kirkendall void and the crack of the Au-Al phases. The crack propagation occurs resulting in the failure of the Au-Al ball bonds. As the IC was exposed at the high temperature, decreased in the lifetime. -
In this study, the fracture strength for fracture mechanism porous calcium phosphate made from sintered with
${\beta}$ -tricalcium phosphate obtained by wet precipitation procedure is analyzed using finite element method and experiment measurement. First, three$3{\times}3{\times}3mm^3$ and$5{\times}5{\times}5mm^3$ specimens are prepared and tomographic images of one$5{\times}5{\times}5mm^3$ specimen are obtained by micro focus X-ray CT. The compression tests using the specimens are carried out to measure the elastic modulus and fracture strength to analyze the fracture mechanism of porous calcium phosphate specimen. The tomographic images are reconstructed by 3D reconstruction program. The finite elements are directly built up in the reconstructed specimen. The numerical simulation for the compression tests is performed using the element. The mechanism of calcium phosphate of simulation are obtained by the compression tests using there cylindric specimen of height 19.5 mm and diameter 10 mm. From the results, the applicability of porous calcium phosphate is evaluated to care fracture and vacant bone of a patient as the reinforcement material. -
In this study, we researched how to estimate life-stress relationship and acceleration factor through performing accelerated life test and analyzing it. The purpose of this study is to predict life of pneumatic cylinder within short time which is widely used in automation manufacturing line. In design of accelerated life test, we selected operating pressure and load that have the most influence on main failure mode of pneumatic cylinder as accelerated factor. We used two-way factorial design for arranging of test condition to accelerated factor and accelerated level.
-
This paper suggests an example of modification of the durability test specifications of electronic control unit for an automotive system in phase of design validation. The basic concept to redefine the specifications of durability test is based on the Arrhenius relationship for accelerated temperature test and the modified Coffin-Manson model for temperature cycle test. The ambient temperature of the powered-event durability test is increased to reduce the required test time of the current specification. Furthermore, the holding time between the events to cool down the temperature of the components is shortened and the resultant temperature rise affects the durability of the components. Thus, the acceleration factor due to the increased temperature range of temperature cycle is also estimated by the modified Coffin-Manson model.
-
Fatigue reliability problems are nowadays actively considered in the design of mechanical components. Recently, Dimension Reduction Method using Kriging approximation (KDRM) was proposed by the authors to efficiently calculate statistical moments of the response function. This method, which is more tractable for its sensitivity-free nature and providing the response PDF in a few number of analyses, is adopted in this study for the reliability analysis. Before applying this method to the practical fatigue problems, accuracies are studied in terms of parameters of the KDRM through a number of numerical examples, from which best set of parameters are suggested. In the fatigue reliability problems, good number of experimental data are necessary to get the statistical distribution of the S-N parameters. The information, however, are not always available due to the limited expense and time. In this case, a family of curves with prediction interval, called P-S-N curve, is constructed from regression analysis. Using the KDRM, once a set of responses are available at the sample points at the mean, all the reliability analyses for each P-S-N curve can be efficiently studied without additional response evaluations. The method is applied to a spring design problem as an illustration of practical applications, in which reliability-based design optimization (RBDO) is conducted by employing stochastic response surface method which includes probabilistic constraints in itself. Resulting information is of great practical value and will be very helpful for making trade-off decision during the fatigue design.
-
In the manufacture of automobile suspension modules at a company as parts supplier, the design process includes the detail design and the design modification via structural and fatigue durability analyses considering PoF(physics of failure) of their weldments that are repeated more than four times sequentially. The approval of the design and the release of final drawings follows. For the suspension modules, e.g. control arms and cross member, the man-hours per worker required in the process outlined above can reach as high as 1,414hours. Application of the developed integrated design system can reduce the man-hours of 1,004. In comparison with the conventional design process, this integrated design system reduces the required time by about 40%. If expense is taken into account, a savings of approximately $192,000 is estimated, assuming the design process accounts for 1.5% of total sales for the parts supplier
-
The failure mode of steel road wheels in a vehicle is cracks from ventilation hole through to contact plane on steel wheel's disc plate. But a number of cracks of Cornering Fatigue Limit Test is on contact plane near to wheel nut mounting area, even though it's satisfied with specified cycles. So this paper searches out causes to improve durability and reliability of C.F.T by uni-axial bending moment test. The verified cause is a "fretting" on contact area of steel wheel. In result, this paper suggests a solution to prevent a fretting by inserting a damping shim, 0.7mm between steel wheel contact areas. Therefore this paper makes it possible to move crack position of C.F.T in steel wheel from contact plane to vehicle's failure mode.
-
This paper suggests a method using Bayesian inference to estimate the parameters of Weibull distribution and acceleration parameters under the condition that the stresses are time-dependent functions. A Bayesian model based on the discrete time approximation is formulated to infer the parameters of interest from the failure data of the virtual tests and a statistical analysis is considered to decide the most probable mean values of the parameters for reasoning of the failure data.
-
The whisker grows at the plating of a lead frame so that it causes the serious problem like the short. To prove this case, many people have studied the cause and influence of the tin whisker growth. This study explains the grain size affects the growth of the whisker in the lead frame. By these studies about the whisker, the whisker growth is discovered by stresses generated by the intermetallic compound and CTE mismatch in both plating and base metal. The stresses or lattice defect generated in the plating process changes grain structure of plating. Consequently, these various stresses are stabilized by forming unspecified whiskers through lots of grain boundaries. Because the grain boundary is the path of the whisker growth, the smaller grain size exists, the more whiskers grow.
-
LEDs which have many merits are widely used in the field of light devices, and have rapidly replaced old light devices such as incandescent or fluorescent lamps. Long life, on the order of 50,000 to 100,000 hours, is one of the key features of light emitting diodes(LEDs) that has attracted the lighting community to this technology. High Power white LEDs have yet to demonstrate this capability. This paper planed accelerated life test that has two factor(temperature, current) and two levels. Finally, using ALTA programs, we estimated the common shape parameter of Weibull distribution, life-stress relationship, B10 life and accelerating factors.
-
In this study, we try to find the root cause of water condensing failures in a headlamp using chemical and mechanical analysis. Through the surface inspection by OM, SEM and CT, it was found that water infiltrate into the headlamp through hotmelt adhesive debonding part caused by adhesion force degradation and poor quality. IR spectra shows that adhesion force degradation are characterized by increase of some functional group(1742, 1710, 1649, 1016). Through the ESPI measurement, it is turned out that bonding structural change by thermal expansion and degradation of adhesive can be the cause of void generation. So it is recommended that cooling passage and the bonding part should be redesigned to give a guarantee of less thermal stress and high adhesion quality.
-
Stainless steel sheets are widely used as the structure material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. Gas welding is very important and useful technology in fabrication of an railroad car and vehicles structure. However fatigue strength of the gas welded joints is considerably lower than parent metal due to stress concentration at the weldment, fatigue strength evaluation of gas welded joints are very important to evaluate the reliability and durability of railroad cars and to establish a criterion of long life fatigue design. In this paper,
${\Delta}P-N_f$ curve were obtained by fatigue tests. Using these results, the accelerated life test (ALT) is conducted. From the experimental results, an acceleration model is derived and acceleration factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of plug and ring gas welded joints and data analysis by statistic reliability method, to save time and cost, and to develop optimum accelerated life prediction plans. -
Failure mechanism of the poor contact is analyzed on the basis of used connectors and this poor contact of connectors is reappeared by the new forced fretting wear method. As the result of failure analysis and reappearance, fretting wear and corrosion of the contact interface causes the contact resistance degradation and the poor contact of connectors. The amount of degradation depends on the fretting stroke. Changes in contact resistance of static contacts are likely to be small and gradual, while motions of contact interface may result in larger and discontinuous changes in resistance and voltage. This voltage drop by fretting motions is large enough to cause the distortion of sensor signal and mis-working of electric components.
-
A plate type supporting structure of a tube bundle in axial flow generates a certain band of a high frequency periodic excitation of a vortex shedding and/or a flow separation due to sharp edge of the plate thickness and a severe pressure drop due to a cross-sectional area of the supports. With a design consideration of the low vibration and a small flow resistance, the analysis method is uniquely confined to an experimental approach because a complex geometry of a cylindrical tube bundle and/or physical phenomena related to the fluid-structure interaction of tube bundle in a flow impede a theoretical or a numerical approach. A 5x5 cylindrical tube bundle with 5 supports which were discretely located along the bundle's axis was tested in the FIVPET hydraulic test loop for a design evaluation and an analysis perspectives. A high frequency flow-induced vibration of the supporting structures of the cylindrical tube bundle was measured at a outer surface of a supporting structure through a transparent flow housing by the laser dopper vibrometer. Pressure drop in-between three measurement distances was measured by the differential pressure transmitter. High frequency vibration and pressure drop fairly depends on the geometric design of supporting structure. So, these two parameters would be used as a qualitative design variables for design evaluation and analysis.
-
A supporting structure for a long tube bundle of a large diameter is considered in this paper. The primary purpose of the present study is to develop a spacer grid structure for a so-called "dual cooled nuclear fuel", which has been being studied for a nuclear power uprate. The outer diameter of the fuel rod increases considerably from the conventional one. So a completely new shape of the supporting structure (spacer grid) needs to be developed. One of the challenges is to insert a supporting tube into the cross points of the grid straps. To meet a supporting performance, the load vs. displacement characteristics should be obtained. So the present study focuses on the finite element analysis technology to evaluate the characteristics through a parametric study. As a result, major influencing parameters are investigated for an optimized spacer grid design.
-
Evaluation of Endcap Welding Test for a Nuclear Fuel Rod having External and Internal Tube StructureAn irradiation test of a nuclear fuel rod having external and internal tube structure was planned for a performance. To establish fabrication process satisfying the requirements of irradiation test, micro-TIG welding system for fuel rods was developed, and preliminary welding experiments for optimizing process conditions of fuel rod was performed. Fuel rods with 15.9mm diameter and 0.57mm wall thickness of cladding tubes and end caps have been used and optimum conditions of endcap welding have been selected. In this experiment, the qualification test was performed by tensile tests, helium leak inspections, and metallography examinations to qualify the endcap welding procedure. The soundness of the welds quality of a dual cooled fuel rods has been confirmed by mechanical tests and microstructural examinations.
-
In this study, we studied failure cause of check valve through analysing characteristic of it used in turbo compressor. We researched how to improve to reduce chaterring occurrence which is cause of main failure mode and suggested how to improve reliability of check valve through it.
-
Pneumatic cylinder is widely used in the various industrial fields. Reliability Study of this field is very important part to the related companies. In this study, we want to predict the life of pneumatic cylinder using Cox (or proportional hazards) model. Used in biomedical applications, the Cox model can be used as an accelerated life testing model. We considered working pressure and temperature as stress factors. The statistical software is used to analyze and forecast the life data.
-
In this paper, the long-term reliability for 1.25G transceiver in use of high speed optical access network is investigated. High temperature storage tests and accelerated life tests are used to long-term reliability. Accelerated aging test have been during 3,000 hour of the three accelerated aging conditions by caused high temperature stress. Mean life is assumed to follow the Arrhenius relationship and analysis from the failure data obtained in the accelerated aging conditions.
-
This study investigates the Failure Modes, Effects and Criticality Analysis (FMECA) Method for the railroad vehicle. Recently, RAMS (Reliability, Availability, Maintainability and Safety) is one of the most important issues in the railroad industry. FMECA is prerequisite for the RAMS Analysis, and it is a procedure to identify the potential failure modes and their effects and to reduce or mitigate the critical effects on the system. FMECA is used in various industries and it is specialized in each industry. For instance, MIL-1629a and SAE-J1739 are specialized FMECA method for Military industry and Automotive industry, respectively. Although the railroad industry requires the high reliability system, it does not have a specialized FMECA yet. Thus, in this paper, an FMECA method specialized to the railroad vehicle was proposed through analyses and comparison of the MIL-1629a, SAE-J1739 and IEC-60812 standards.
-
Considering that human body is continuously experiencing mechanical stimuli due to daily activities, the micro-physical environments of cells/tissues should be considered for the successful outcomes in tissue engineering and/or related researches. Obviously, there are many factors involved in cell-based researches. In this presentation, the current trends and some of outcomes are introduced. Through this studies, the roles of mechanical engineering in relation to medical/biological researches are to be emphasized.
-
The migration and proliferation of vascular endothelial cells (VEC), which play an important role in vascular remodeling, are known to be regulated by hemodynamic forces in the blood vessels. When shear stresses of 2, 6, 15 dynes/
$cm^2$ are applied on mouse micro-VEC in vitro, cells surprisingly migrate against the flow direction at all conditions. While higher flow rate imposes more resistance against the cells, reducing their migration speed, the horizontal component of the velocity parallel to the flow increases with the flow rate, indicating the higher alignment of cells in the direction parallel to the flow at a higher shear stress. In addition, cells exhibit substrate stiffness and calcium dependent migration behavior, which can be explained by polarized remodeling in the mechanosensitive pathway under shear stress. -
Layer manufacturing technology has been recently spotlighted as a promising candidate to fabricate porous scaffolds for tissue engineering, because it can provide three dimensional interconnectivity and different pore structures and on-demand scaffold design. This study aims to fabricate HA/PCL composite scaffolds for bone tissue engineering by a layer manufacturing technology, paste extruding deposition, and to characterize in vitro and in vivo biocompatibilities of the scaffolds. This study discusses the mechnical properties, proliferation and differentiation of osteogenic cells, and tissue in-growth and bone regeneration behavior using animal models.
-
It is reported that mechanical stimulation takes a role in improving cell growth in skeletal system. And various research groups have showed that developed bioreactor to stimulate cell-seeded and threedimensional scaffold. In this study, we designed a custom-made bioreactor capable of applying controlled compression to cell-seeded agarose gel. This device consisted of a circulation system and compression system. In circular system, culture chamber was sealed for prohibiting contamination and media solution was circulated by pump. In compression system, mechanical stimuli were controlled by LabVIEW software and mechanical transfer system. Cell-encapsulated agarose gels were cultured for up to 7 days. There were significant differences between the number of cells grown in dynamic cell culture and in static cell culture from 3 days to 7 days.
-
Scaffold fabrication for regenerating functional human tissues has an important role in tissue engineering, and there has been much progress in research on scaffold fabrication. However, current methods are limited by the mechanical properties of existing biodegradable materials and the irregular structures that they produce. Recently, Solid freeform fabrication (SFF) technology was remarked by fabricating 3D free-form micro-structures. Among SFF technologies, we tried to fabricate scaffolds using micro-stereolithography which contain the highest resolution of all SFF technologies and precision deposition system which can use various biomaterials. And we developed the CAD/CAM system to automate the process of scaffold fabrication and fabricate the patient customized scaffolds. These results showed the unlimited possibilities of our SFF technologies in tissue engineering.
-
Fulminant hepatic failure is a clinical syndrome associated with a high mortality rate. Orthotopic liver transplantation is the only clinically proven effective treatment for patients with end-stage liver disease who do not respond to medical management. A major limitation of this treatment modality is the scarcity of donor organs available, resulting in patients dying while waiting for a donor liver. An extracorporeal bioartificial liver (BAL) device containing viable hepatocytes has the potential to provide temporary hepatic support to liver failure patients, serving as a bridge to transplantation while awaiting a suitable donor. In some patients, providing temporary hepatic support may be sufficient to allow adequate regeneration of the host liver, thereby eliminating the need for a liver transplant. Although the BAL device is a promising technology for the treatment of liver failure, there are several technical challenges that must be overcome in order to develop systems with sufficient processing capacity and of manageable size. In this overview, the authors describe the critical issues involved in developing a BAL device. They also discuss their experiences in hepatocyte culture optimization within the context of a microchannel flat-plate BAL device.
-
This paper describes the locomotion of a water jumping robot which attempts to emulate the fishing spider’s ability to jump on the water surface. While previous studies of the robots mimicking arthropods living on water were focused on recreating their horizontal skating motions, here we aim to achieve a vertical jumping motion. The robot jumps by pushing the water surface with rapidly released legs which were initially bent. The motion is triggered with a latch driven by the shape memory alloy actuator. The robot is capable of jumping to the maximum height of 26mm. Jumping efficiency, defined the maximum jumping height on water over the maximum jumping height on rigid ground, is 0.26 This work represents a first step toward robots that can locomote on water with superior versatility including skating and jumping.
-
Flagellate bacteria such as Escherichia coli or Serratia marcescens possess a remarkable motility system based on a reversible rotary motor. We have employed S. marcescens as microactuators in low Reynolds number fluidic environments to move a larger engineering element around. Microstructures fabricated using conventional microfabrication techniques are blotted on the swarm plate, which leaves a bacterial monolayer on the surface of the microstructure. We have investigated microstructures powered by bacteria to determine how cell orientation on the microstructure surface relates to the swarming patterns as well as how the orientation is affected by the blotting process. This study will help to refine directional control of bacterial transporters by exploiting bacterial sensory mechanisms.
-
This research describes about designing and manufacturing X-wing type flapping micro aerial vehicle which intends to improve the performance of one-pair wing flapping vehicle with innovated design. This design, X-wing as we call, was introduced for some time ago from many laboratories but still there hasn’t any reports dealing on its theoretical or numerical analysis. By manufacturing the X-wing with our own design and succeeding its flight test will give us the general idea on X-wing which may guide us to conduct the numerical and experimental analysis later on. We focused to design the X-wing and introduce some conceptual theories about its characteristics on this report.
-
Insect flight is adapted to cope with each circumstance by controlling a variety of the parameters of wing motion in nature. Many researchers have struggled to solve the fundamental concept of insect flight, but it has not been solved yet clearly. In this study, to find the most effective flapping wing kinematics, we conducted to analyze CFD data on fixing some of the optimal parameters of wing motion such as stoke amplitude, flip duration and wing rotation type and then controlled the deviation angle by fabricating wing tip motion. Although all patterns have the similar value of lift coefficient and drag coefficient, pattern A(pear-shape type) indicates the highest lift coefficient and pattern H(pear-shape type) has the lowest lift coefficient among four wing tip motions and three deviation angles. This result suggest that the lift and drag coefficient depends on the angle of attack and the deviation angle combined, and it could be explained by delayed stall effect.
-
Immune system is composed of multiple cells with distinct functions, and immune responses are orchestrated by complex and dynamic cell-cell interactions. Therefore, each cell behavior and function should be understood under right spatio-temporal context. Studying such complexity and dynamics has been challenging with conventional biological tools. Recent development of new technologies such as state of art imaging instruments and microfabrication techniques compatible with biological systems have provided many exciting opportunities to dissect complex and dynamic immune cell interactions; new microscopy techniques enable us to observe stunning dynamics of immune system in real time. Microfabrication permits us to manipulate microenvironments governing molecular/cellular dynamics of immune cells to study detailed mechanisms of phenomena observed by microscopy. Also, microfabrication can be used to engineer microenvironments optimal for specific imaging techniques. In this presentation, I am going to present an example of how these two techniques can be combined to tackle challenging problems in immunology. Obviously, this strategy can readily be applied to many different fields of biology other than immunology.
-
In the conventional biology, the most of cell studies was carried out by culturing cells in the Petri dish and by investigating cellular behavior under the diverse bio-molecule (cell signalling materials, drugs or etc.) conditions. However, in vivo environments, diverse stimulations including chemical, mechanical and topological environments involved in the proliferation, differentiation and migration of cells and it is almost impossible to provide these conditions with traditional method. We have developed the methods to provide the well defined chemical and mechanical stimulations using microfluidic devices and applied these approaches to the study of environmental effect on cells. In this paper, we will introduce our microfluidic chips to provide microenvironment and its applications using several cells.
-
Cell adhesion is a coordinated process involving initial binding of integrin receptors to extracellular matrix (ECM), recruitment of adhesion proteins, and focal adhesion assembly. The formation of mechanically stable focal adhesion assembly of cells within surrounding ECM is a key parameter to direct numerous cellular functions including cell migration, differentiation, and apotosis. With current cell adhesion assays, it is difficult to understand contributions of each coordinated event on evolution of cell adhesion strengthening since cells spontaneously spread upon their adhesion to the substrate, thus remodeling their cytoskeletal structure. In this presentation, novel approaches for analysis of cell adhesion strengthening process based on the combination of mechanical device, micro-patterned substrates, and molecular biological techniques will be discussed.
-
Tissue engineering is an interdisciplinary field that utilizes the principles of engineering and life sciences toward the creation of biological substitutes. Traditionally, major components of tissue engineering are cells, scaffolds, growth factors and recently biomechanical aspects have been given much attention. A large number of studies have reported that mechanical signals are of particular interest in either encouraging or inhibiting cellular responses. In tissue engineering, cell adhesion is a very important step, because quality of adhesion may determine a cell fate in the future. Elasticity of cell-adhesive substrate is found critical in regulating stem cell differentiation. Cells exert different contractile forces for cell migration, depending on substrate mechanics. Though tissue engineering is very interactive with diverse expertise, for a breakthrough, principles of biomechanics in tissue and cell level needs to be fully understood.
-
In the case of Posterior Cruciate Ligament (PCL), the most frequent mechanism is the dashboard injury, which is directly pressurized to the anterior of the proximal tibia in the state of the knee hyperflexion. The PCL associated ligament damage happens when the posterior injury, the varus, the valgus, the hyperextension and the severe vagus torque are out of the critical value of PCL. After the successful operation cases of Anterior Cruciate Ligament (ACL) reconstruction using the allograft were informed from 1986, a number of results kept over the maximum 10 years were reported. Unfortunately, PCL reconstruction are crowded the surgery techniques such as the graft, the tibia fixing method, the fixation device, the location of the femoral tunnel, the number of the graft bundles and PCL reconstruction to access to the stability of the normal joint is being developed. Therefore, this study is the basic research of these above facts. The current transtibial tunnel surgery using the cadaveric Achilles tendon grafts is chosen for the various PCL reconstruction. The initial extension of the Achilles tendon by the fixing device and its location under the cyclic loading, were observed.
-
An upper tibial opening wedge osteotomy is an operation to cure a malalignment and a degenerate arthritis. To prevent the postoperative malalignment caused by the upper tibial opening wedge osteotomy, the research to define the relationship between a Hinge Axis Angle and a Posterior Slope Angle is needed. The effect of the relationship between the hinge axis angle and the gap angle on the posterior slope angle is studied. After 3-D Compute Tomography (CT) scanning image is reconstructed, the virtual surgery is performed by the reconstructed 3-D tibia model. It was proved that the relationship between the hinge axis angle and the gap angle were constant and the simple mathematical model could be derived. To verify the suggested mathematical model, it compared with the measured data from the virtual surgery. In conclusion, while the deviation between the data from the virtual surgery and ones of the mathematical model under the gap angle<
$10^{\circ}$ was less than 1%. -
To analyze biomechanical effects of various types of menisectomy in the knee joint, the contact area and pressure distribution of intact the knee joint and the operated by various menisectomies were studied by using finite element method their results are compared with each other. In this study, the femur, the tibia, the articular cartilage and the menisci were three dimensionally reconstructed using MR Images of healthy knee joint in full extension of 26 years old male. Also, three dimensional finite element model of the knee joint was constructed including the models of ligaments and tendons on the reconstructed three dimensional model. Bones were considered to be rigid, articular cartilage and menisci were considered as homogeneous, isotropic and linearly elastic materials and ligaments and tendons were modeled as hyperelastic materials. Based on the results, the effects of various types of menisectomy on the knee joints are clearly elucidated.
-
In the total knee arthroplasty (TKA), kinematic benefic of a mobile-bearing total knee prosthesis is still arguing. Main reasons for implant failure are loosening and polyethylene wear and should be solved with new designs with mob ile bearings. The kinematics of the knee prosthesis also affects the implant failure. Recently, a second generation of p rostheses with a mobile-bearing was developed. The current study aimed to assess the kinematic path of the 2nd generation mobile knee prosthesis compared to the normal knees. Using 3D/2D registration method, CT-derived 3D knee models were fitted to sequential 2D X-ray images during knee flexion. 3D kinematics of the femur and the tibia were analyzed. The 2nd generation mobile-bearing TKA prosthesis (e.motion, Aesculap, Germany) knees showed less external rotation and knee flexion range compared to the normal knee, but the trend of external rotation was similar each other.
-
We have investigated the blood sucking phenomena of a female mosquito. The main objective of this study is to understand the mosquito's blood sucking mechanism and eventually to develop a bio-mimic technology that can be used to resolve the problem encountered in the transport of infinitesimal biological fluids in various bio-chips and microchips. At first, the consecutive velocity fields of blood-sucking flow in a proboscis were measured using a micro-particle image velocimetry (PIV) system employed with a high-speed camera. The velocity signals of the blood-sucking flow in the proboscis represent a periodic pulsatile flow pattern and spectral analysis on the velocity waveform shows a clear peak at 6.1 Hz.
-
The three main physiological functions of nose are air-conditioning, filtering and smelling. Knowledge of airflow characteristics in nasal cavities is essential to understand the physiological and pathological aspects of nasal breathing. Several studies have utilized physical models of the healthy nasal cavity to investigate the relationship between nasal anatomy and airflow. In our laboratory, there have been a series of experimental investigations on the nasal airflow in normal and deformed nasal cavity models by PIV under both constant and periodic flow conditions. In this time, airflow inside normal nasal cavity is investigated numerically by the FVM general purpose code. The comparisons with PIV measurement are appreciated. Heat and humidity transfer is dealt numerically. Dense CT data and careful treatment of model surface under the ENT doctor’s advice provide more sophisticated cavity models for both PIV experiment and numerical grid system. Average and RMS velocity distributions have been obtained for inspirational and expirational nasal. Temperature distribution, heat and humidity transfer through the mucosa are obtained.
-
Characteristics of pulsatile flow in 3-dimensional elastic vessel wall should be investigated in order to understand the physiological blood flow in human body. In this study, the modelling of the physiological blood flow in the elastic blood vessel is proposed. Variation of the pressure and the velocity wavefroms are obtained using the FSI method
-
Detailed knowledge on the motion of blood cells flowing in micro-channels under simple shear flow and the influence of blood flow is essential to provide a better understanding on the blood rheological properties and blood cell aggregation. The microscopic behavior of red blood cell (RBCs) is numerically investigated using a fluid-structure interaction (FSI) method based on the Arbitrary-Lagrangian-Eulerian (ALE) approach and the dynamic mesh method (smoothing and remeshing) in FLUENT (ANSYS Inc., USA). The employed FSI method could be applied to the motions and deformations of a single blood cell and multiple blood cells, and the primary thrombogenesis caused by platelet aggregation. It is expected that, combined with a sophisticated large-scale computational technique, the simulation method will be useful for understanding the overall properties of blood flow from blood cellular level (microscopic) to the resulting rheological properties of blood as a mass (macroscopic).
-
As a prerequisite of developing muscle biofeedback system which can simulate analogous isokinetic exercise, the purpose of this study was to study the effects of frequency and amplitude of whole-body vibration on the difference in sEMG on lower extremities during leg press exercise with/without vibration. The amplitude of vibration was set to 20, 50, 80 and the frequency of vibration was set to 10, 20, 30, and 50 Hz. EMG were measured at Vastus lateralis muscle and Vastus medialis muscle. MP100 EMG module(BIOPAC system Inc., USA) was used for EMG measurement. The result showed that the combination of frequency of 30Hz and amplitude of 50 had more activated EMG than other combination with relatively small work load (30kg). It is necessary to experiment the frequency between 20 and 40Hz in detail, and to normalize sEMG using maximal voluntary contraction (MVC).
-
Less than 1 % directional error in the range of 5 meters in the green could cause a stroke or more. Although there are several reasons offsetting the direction of the golf ball, lie angle and sidespin effect are the most crucial factors of the putting game. Simple equation is conformed to the experimental results of the deviation of the directional error in all distance. Also, the experimental results of the putting robot show that there are significant side spin effects.
-
By applying sonic wave vibration technology in weight exercise equipment, we introduced an completely new concept of device into the fitness and medical industry creating a new trend. Sonic wave leg press exercise system which got over the limit of technology will be easily accessible not only by professional athletes but also by ordinary users and even minority groups such as disabled, elderly, children.
-
One of the important functions of prosthetic foot is the foot inversion-eversion which is so important when walking on uneven surfaces. The aim of our study was to evaluate the effect of foot eversion angle especially on knee and ankle joint for transtibial amputees by motion analysis. The experimental data were collected from three transtibial amputees and then ten healthy individuals. To simulate walking on side sloping ground, we used custom-made slope (5, 10, 15 degrees). Motion analysis was performed by 3-dimensional motion analyzer for 6 dynamic prosthetic feet. The results showed that knee abduction moments of amputated leg were decreased but those of sound leg were mainly increased as foot eversion angle increased. And ankle abduction moments of sound leg were inconsistent in magnitude and tendency between control and experimental group. Therefore foot eversioncharacteristics should be considered to develop advanced prosthetic foot.
-
To fabricate microsized poly(methyl methacrylate)(PMMA) beads of uniform size and density on poly(ethylene terephthalate) (PET) fis, we introduce an electro spraying technique that uses a target electrode applied with an ac electric fid. Using the apparatus and various material properties, we could obtain uniform size PMMA beads which were deposited on the thin PET film. The optical properties, transmittance and light diffusivity of the fis electro sprayed with the PMMA were characterized. The results show that the sprayed beads appear to act as a good optical diffuser, like microlenses. To understand the effect of process variables, applied field conditions and rheological properties, the morphological pictures of the deposited particles were investigated through the optical and scanning electron microscope.
-
The purposes of this study were to measure the ranges of motion in knee joint and during continuous passive motion(CPM) treatment and to computationally calculate joint angles at the knee joint dependent on the CPM machine design and its application. Four CPM machines and eleven candidates were recruited for this study. Experimental and numerical studies have been peformed to calculate the range-of-motion of CPM machines. From the experimental measurements, the average range of motions at the knee joint for the CPM machine #1, #2, #3, and #4 were lower than the manufactures suggested values due to improper alignments of the hip and knee joints to the CPM machines. Different design of CPM machine generated different outcomes of the ROM at the knee joints during CPM. The experiments and kinematic simulation in this study could be used to provide useful guidance in the treatment of CPM after joint surgery.
-
Recent clinical studies have shown that computer navigation for total knee arthroplasty (TKA) provides improved component alignment accuracy. However, femoral stress fracture after computernavigated TKA have been reported due to the pin hole and we hypothesized that osteoporosis would be one of the key factors in pin hole fracture after computer-navigated TKA. We investigated the von-Mises stress around the femoral pin-hole for different elastic modulli and ultimate stresses and four different pin penetration modes to understand the aging effect on femoral stress fracture risk after computer-navigated TKA by finite element analysis. In this study, aging effect was shown to increase the femoral stress fracture risk for all pin penetration modes. Especially, aging effect was shown dramatically in the transcortical pin penetration mode.
-
IPMC(Ionic Polymer-Metal Comosite) exhibits large deformation, having great attention in many application fields. It generates bending moment by ion exchange polymer film. It can be quickly bended by the applied voltage across the plated electrode of the polymer film. In the present paper, we derive the theoretical modeling and dynamic analysis of bending motions of IPMC actuators using the Euler-Bernoulli beam theory. The theoretical model of a cantilever IPMC actuator estimates the moment produced by the applied voltage. The dynamic characteristics, including natural frequencies and frequency response, are calculated by the theoretical model, and they are compared with the experimental results and finite element analysis. It is shown that the mathematical modeling allows precise estimation to the voltage-driven motion of the cantilever IPMC in air.
-
45% of the sports accidents is the knee damage and the representative case is the damage of an Anterior Cruciate Ligament (ACL) and the Posterior Cruciate Ligament(PCL). Although the past different views of ACL reconstruction comes to an agreement, the disputes of PCL is remained yet. The most important engineering approach for these various surgery techniques is accurately to understand and to evaluate the fatigue behavior depending on the stress flow and the stress distribution under the allotted load and the cyclic load, which are caused by the graft fixing device, the proximal tibia of the PCL reconstructing structure. Therefore, this study is the basic research of these above facts. The current transtibial tunnel surgery using the cadaveric Achilles tendon grafts is chosen for the various PCL reconstruction. The relationships between the slippage, the extension ratio, and the slippage ratio by the heel bone fixing method and the soft tissue fixing method of the Achilles tendon were also defined. This research will be the essential data to help the resonable operating techniques for the next PCL reconstruction.
-
The development of new material systems like Carbon Fiber Reinforced Polymer (CFRP) places ever higher demands on the techniques for non-destructive material characterisation. Image-producing eddy current methods also need to satisfy these demands. Eddy-current imaging of FRP is based on the anisotropic electrical properties of the material investigated. Significant differences in conductivity between carbon fibres, polymer matrix and integrated functional components can be found. The availability of high-resolution sensors enables access to the local distribution of the electromagnetic properties. The static and dynamic procedures for isolating influential characteristics, already in use in eddy-current technology, can now be supplemented by topographical images. The precondition for a successful implementation of the eddy-current procedure is a deeper understanding of the image-generating process which allows correct interpretation of the images obtained.
-
Plasma is 4th state of matters, which consists of electrons, neutral, and ionized particles. In biomedical research, cold plasma, which is generated in atmospheric condition, has been applied to disinfect microorganisms such as bacteria and yeast cells. Because of its low temperature condition, the heat-sensitive medical device can be easily sterilized by the cold plasma treatment. In recent years, the effects of plasma on mammalian cells have arisen as a new issue. Generally, plasma induces intensity dependent necrotic cell death. In this research, we investigate the feasibility of cold plasma treatment for cancer therapy by conducting comparative study of plasma effects on normal and cancer cells. We use THLE-2 (human liver normal cell) and SK-Hep1 (human liver metathetic cancer cell) as our target cells. The needle type of cold plasma is generated by the Helium plasma device. Two types of cells have different onset plasma conditions for the necrosis, which may be explained by difference in electrical properties of these two cell types.
-
Shin, Eun-Ji;Kim, Cheol-Woong;Lee, Ho-Sang;Bae, Ji-Hoon;Wang, Joon-Ho;Park, Jong-Woong;Oh, Dong-Joon 1543
The purpose of this study was to investigate factors affecting the change of tibial posterior slope and introduce a mathematical model which calculate, through 3-dimensional analysis of the proximal tibia, how the angle of the opening wedge along the anteromedial tibial cortex influences the tibial posterior slope and valgus correction when performing a medial open wedge osteotomy. This mathematical model with navigation system can be guidelines which provide surgeons on preoperative and intraoperative measurements to maintain or correct the tibial slope and to obtain the desired valgus correction of the lower limb during an opening wedge osteotomy. -
The tip of these catheter with straight needles is not able to reach in the vicinity of the disc bulging, which are the cause of the low back pain and because the far indirect radio-frequency treatment results in the decompression, the nucleoplasty has the limit. Many incurable diseases has not been solved due to the unexistence of the advanced technique for the MIS human body catheter device. To increase the possibility of nucleoplasty, the needle tip should be located at the closest area of the lesion. For this reason, the best way to increase the success rate of the operation is that the needle tip should access 3-dimensionally to the operating field as soon as possible. To achieve this aim, our studies are restricted as follows: 1) the SMA catheter design to control the 3-dimensional direction, 2) the security of the immediate response by the positive control of the SMA element thermal distribution using Peltier thermoelectric elements, 3) the aquisition of the control data by monitoring the relationship between the temperature of SMA element and the displacement, and 4) the design of the controller to guarantee the accurate location.
-
Super-hydrophobic treated Polyimide film was used as a flexible substrate for developing a new method of metallization. Hydrophilic patterns were fabricated by IN irradiation through shadow mask. Patterned super-hydrophobic substrate was dipped into a bath containing silver nano ink Silver ink was only coated on hydrophilic patterned area. Metal lines of
$600{\mu}m$ pitch were fabricated successfully. However, their thickness was too thin to serve as interconnection. To overcome this problem, iterative dipping was conducted. After repeating five times, the thickness of silver metal lines were increased to over than$2{\mu}$ . After heat treatment of silver lines, their resistivities were reduced to order of$30{\mu}{\Omega}$ -cm the similar level of values reported in other literatures. So, a new method of metallization has high potential for application of RFID antenna and flexible electronics substrates. -
"Biomimetics" is the study and simulation of biological systems with desired properties. In recent times, biomimetic surfaces have emerged as novel solutions for tribological applications in micro-electromechanical systems (MEMS). These biomimetic surfaces are attractive for MEMS application as they exhibit low adhesion/friction and wear properties at small-scales. In this paper, we present some of the examples of biomimetic surfaces that have potential application in small-scale devices.
-
Ionic polymer metal composite (IPMC), one of Electro- Active Polymer (EAP) actuators, has great attention due to the low-voltage driven, large deformation and its potential for artificial muscles. In this paper, we firstly review fish swimming modes using various propulsion mechanisms. Based on study on the swimming mechanisms, we develop an underwater robot actuator which mimics fanning motion of webfoot form. It consists of four actuators fabricated by using IPMC and PDMS which mimics Bio-inspired motion Experiments using a prototype show that the webfooted IPMC actuator generates large deformation and propulsion.
-
Hydrophobic plastic plates employing nano surface features are injection molded using thermoplastic materials. A variotherm molding process is devised for filling the nano pores and releasing the molded nano features from the master. The size of the molded nano surface features are about 100nm in diameter and 200nm in height. The size of the molded plate is about 30mm x 30mm and the thickness is 1mm. As molding materials, Polypropylene, PMMA, COC and PC are employed, which are all typical commodity thermoplastic materials. The mold temperature(stamper temperature) is investigated as a major processing parameter for molding high aspect ratio nano surface features. Almost fully molded nano features are fabricated above a certain level of mold temperature depends on the employing material. The contact angles on the injection molded plates are measured to estimate the hydrophobicity and found to have higher contact angle up to 180% compared to the blank plate with no surface features.
-
The flow visualization is conducted in order to investigate an unsteady flight characteristic of a model dragonfly. The flapping wings are analyzed using smoke-wire and high speed camera. The results of this experiment show that three mechanisms and high incidence angle of the wings are responsible for the lift. The leading edge vortex, which is induced by the rapid acceleration of the wing at the beginning of a stroke, causes the lift enhancement. The delayed stall during the stroke and the fast supination and pronation of the wing near the end of each stroke are also responsible for the lift generation.
-
Relationship between Crosslinking Processes and Mechanical Properties of UHMWPE for Artificial JointVarious mechanical test were conducted on conventional and crosslinked ultra-high molecular weight polyethylene(UHMWPE) all prepared from the same lot of medical grade GUR 1050 for artificial joint. The conventional materials were not irradiated and treated by heating. The cosslinked materials were irradiated with
$25kGy{\sim}200kGy$ by gamma-ray andthen annealed or remelted. Gamma-ray irradiation and heat treatment process were found to significantly impact the crystallinity, and hence the mechanical behavior, of the highly crosslinked UHMWPE. The radiation dose and heating conditions were key predictors of the uniaxial yielding, plastic flow, and failure properties of conventional and highly crosslinked UHMWPE. The correlation model from experiments would be the basic information to enhance the were resistance of artificial joint liner. -
The purpose of this study was to investigate how maximum-effort eccentric exercise over different contraction ranges affects the characteristics of torque-angle relationship of human ankle plantarflexor in-vivo. Subjects were randomly assigned in two groups. One group (n=6) performed 120 maximum-effort eccentric ankle dorsiflexion contractions at short muscle length (ankle range of motion from -5 to 15 deg) and the other group (n=6) at long (ankle range of motion from 10 to 30 deg) muscle length. Eccentric exercise decreased the maximum isometric ankle plantarflexion torque
${\sim}40%$ . It was found that the optimum ankle joint angle changed from 7.5 deg to 11.1 deg and 10.1 deg, shifted toward the longer muscle length, regardless of the exercise range. The results of this study suggest that eccentric exercise alters the characteristics of torqueangle relationship of the muscle but there is no differential effect of the eccentric contraction range. -
We investigated the effects of intermittent hydrostatic pressure with various duration of resting period on changes in calcium (
$Ca^{2+}$ ) concentration and adhesive forces of cells on substrates. The quantitive adhesive forces of cells were measured under various resting periods. When the pressure applied to the cells, the concentration of$Ca^{2+}$ increased. Under intermittent hydrostatic pressure, the concentration of$Ca^{2+}$ was maintained under a resting period of 15 min, while it was not decreased with other resting periods of less than 15 min. With a resting period of 15 min, the magnitudes of adhesive forces were significantly increase. In addition, the adhesive forces were measured with and without$Ca^{2+}$ chelating agents to evaluate the effect of$Ca^{2+}$ on cell adhesiveness. When$Ca^{2+}$ ions were chelated, the adhesive forces dramatically decreased, even under intermittent hydrostatic pressure. We conclude that$Ca^{2+}$ plays an crucial role in modulating the adhesive forces of cells, and that the concentration of$Ca^{2+}$ can be increased by intermittent hydrostatic stimuli. -
This paper reports a simple fabrication method for creating the superhydrophobic polymer surface using a plasma etching. Generally, it is necessary for the superhydrophobic surfaces to have a rough structure on surface with the composition of the low surface energy. In this study, Poly(methyl methacrylate) (PMMA), poly(ethylene terephthalate) (PET), acrylonitrile butadiene styrene (ABS) with superhydrophobic surface were fabricated using
$O_2$ plasma etching and vapor deposition with the fluoroalkylsilane self-assembled monolayers. The plasma treated polymer surfaces are covered with the nano-pillar shaped structures after treatment for$1{\sim}2min$ . And these samples with FOTS SAMs coating are showed the superhydrophobicity having the water contact angle of around$150^{\circ}$ and sometimes around$180^{\circ}$ depending on the treatment time. Furthermore the nanostructured polymer is transparent for the visible light. -
Fibroblast is constantly subjected to mechanical loads in connective tissues where mechanical signals are converted to intercellular biochemical events. The aim of this study is to understand the effects of tensile stress on the neurotrophin (NT) and transforming growth factor (TGF) expression of fibroblast in vitro. Nerve growth factor (NGF) stimulates fibroblast migration, and TGF is related to tissue repair. In this study, at the uniaxial stretch of 10% strain and frequency of 0.5 Hz, different resting times of 0, 20, and 60 min are placed in between 10 min stimulations periods. Results show increase in NGF mRNA levels and a substantial decrease in NT3 mRNA after 1 hr of stimulation, indicating that the tensile stress may regulate NGF and NT3, key factors for the neurocosmetic applications. The mRNA level for TGF-
${\alpha}$ and TGF-${\beta}2$ had increased up to two-folds after 1 hr of stimulation, showing that the tensile stress may control TGF, an important part of wound healing. -
This paper describes a real-time isometric pinch force prediction algorithm from surface electromyogram (sEMG) using multilayer perceptron (MLP) for human robot interactive applications. The activities of seven muscles which are observable from surface electrodes and also related to the movements of the thumb and index finger joints were recorded during pinch force experiments. For the successful implementation of the real-time prediction algorithm, an off-line analysis was performed using the recorded activities. Four muscles were selected for the force prediction by using the Fisher linear discriminant analysis among seven muscles, and the four muscle activities provided effective information for mapping sEMG to the pinch force. The MLP structure was designed to make training efficient and to avoid both under- and over-fitting problems. The pinch force prediction algorithm was tested on five volunteers and the results were evaluated using two criteria: normalized root mean squared error (NRMSE) and correlation (CORR). The training time for the subjects was only 2 min 29 sec, but the prediction results were successful with NRMSE = 0.112
${\pm}$ 0.082 and CORR = 0.932${\pm}$ 0.058. These results imply that the proposed algorithm is useful to measure the produced pinch force without force sensors in real-time. The possible applications include controlling bionic finger robot systems to overcome finger paralysis or amputation. -
Haptic rendering is a process that provides force feedback during interactions between a user and an object. This paper presents a haptic rendering technique for a telemanipulation system of deformable objects using image processing and physically based modeling techniques. The interaction forces between an instrument driven by a haptic device and a deformable object are inferred in real time based on a continuum mechanics model of the object, which consists of a boundary element model and
${\alpha}$ priori knowledge of the object's mechanical properties. Macro- and micro-scale experimental systems, equipped with a telemanipulation system and a commercial haptic display, were developed and tested using silicone (macro-scale) and zebrafish embryos (micro-scale). The experimental results showed the effectiveness of the algorithm in different scales: two experimental systems applied the same algorithm provided haptic feedback regardless of the system scale. -
Various applications of exoskeleton system are reported in the area of military, healthcare, and industries. More the user gets help from exoskeleton system, more power is consumed. To resolve this design conflict, we suggest an energy efficient exoskeleton system which compensates muscle fatigue in isotonic and isometric contraction conditions. Fatigue compensated exoskeleton significantly reduced muscle fatigue while consumed less operation power. In addition, the level of fatigue compensation can be managed by motor control using various input profile. It can make user customized exoskeleton system.
-
Powered robotic exoskeletons are currently under development for assisting or supporting human muscle power. Many applications using this system for the purpose of national defense system, medical support, and construction industry are now frequently introduced. In this paper, we proposed the exoskeletal wearable robotics for construction workers. First, we analyzed general work conditions at the construction site and set up target tasks through the datum. Then dominant muscles’ activity which is related with the defined target tasks was checked up. Herein, wearers’ intent signal generation methodology was introduced in order to effectively activate the proposed system. In the final part of this paper, we evaluated the capability and feasibility of the exoskeletal robotics by the electromyography (EMG) signal variance; demonstrated that robotic exoskeletons controlled by muscle activity could be useful way of assisting with construction workers.
-
RQ(Respiratory Quotient) value is obtained from the ratio of the consumed oxygen and the produced carbon dioxide during the patient's respiration. To investigate the efficacy of insulin and diagnosis the metabolic disorder in short time, the RQ value can be used as important parameter. The measurement of oxygen and carbon dioxide amounts is needed large chamber and complex sensors. But If the atmospheric oxygen and carbon dioxide concentrations do not change, the expiratory oxygen and carbon dioxide can be used to obtain RQ value. A convenient RQ measuring device has been developed by using two sensors for O2 and CO2. The estimation of RQ devices confirms that the RQ device can obtain accurate data by eliminating uncertain factor such as delay time and remaining gases.
-
A Transcutaneous Energy Transmission System (TET) has been developed for the wireless energy transmission with two magnetically coupled coils. A resonance circuit is used to raise the induced voltage and current of the secondary coil. Its resonance frequency depends on the internal resistance of circuit and the transferred energy. Because the transferred energy usually changes in wide range, the output voltage is unstable and the energy transferring efficiency decrease. A push-pull class E amplifier is usedto generate high frequency AC voltage. To maintain proper resonance frequency, the voltage output of the amplifier was continuously monitored and adjusted to the optimized resonance frequency. Because of its high frequency (370 kHz), a phase lockedloop circuit and a comparator are used to monitor the output waveform. The results of experimentaldata show that the PLL circuit can increase the transmission efficiency and stabilize the output voltage of TET.
-
We report a new molecular detection process which measures the changes in the plasmon resonance peaks of periodic Au nanoparticle arrays fabricated using the electron beam lithography. As the Au nanoparticle arrays are modified by the chemical reaction in solutions having various concentrations of a target molecule, both the position and intensity of the plasmon peak change in proportion to the concentration of the target molecule. We expect that the process developed in this work can be employed for fine tuning of the plasmon peak wavelength and also for the optical detection of various kinds of molecules. Moreover, this method may improve the measurement accuracy compared with existing approaches that use only one change (peak wavelength or peak intensity) as a readout value for the molecular detection.
-
A temperature gradient focusing (TGF) via Joule heating phenomenon was numerically studied. The governing transport equations are implemented into a quasi-1D numerical model to predict the resulting temperature, velocity, and concentration profiles along a microchannel of varying width under an applied electric field. The model is used to analyze the effects of varying certain geometrical parameters of a microchannel on the focusing performance of the device. We show the effects of varying width of the microchannel having a fixed length, and propose the optimal geometry of the device. This method can be easily implemented into lab-on-a-chip (LOC) applications where focusing is required based on its simple design.
-
Rapid, real-time detection of pathogenic microorganisms is an emerging and quickly evolving field of research, especially with regard to microorganisms that pose a major threat to public health. Herein, a new method that uses bioimpedance and solid culture medium for the real-time detection of microorganisms is introduced. We fabricated a new impedimetric biosensor by integrating solid media and two plane electrodes attached on two facing sides of an acryl well. During bioelectrical impedance analysis, the solid medium showed the characteristics of a homogenous conductive material. In a real-time impedance measurement, our solid-medium biosensor could monitor bacterial growth in situ with a detection time of
${\sim}4$ hrs. Our data indicate that the solid-medium biosensor is useful for detecting airborne microorganisms, thereby providing a new analytical tool for impedance microbiology. -
In this study, we developed 3D MLS-based variable-node elements for easy meshing. These elements should be derived from 2D MLS-based variable-node elements and would be utilized as key elements of easy meshing technique we proposed. Using developed 3D MLS-based variable-node elements, we demonstrated several examples having complex configuration compared with conventional meshing technique. Moreover, we compared with the stress results of our model and conventional one.
-
Cell migration is one of the essential mechanisms responsible for complex biological processes. Intensive researches have begun to elucidate the mechanisms and search intriguing conditions for efficient control of cell migration. One general mechanism which is widely applicable for cells including neutrophil, Escherichia coli and endothelial cell is chemotaxis. Especially, understanding the chemotactic mechanics of cell crawling has important implications for various medical and biological applications. The single cell study for chemotaxis has an advantage over studies with the population of cells in providing a clearer observation of cell migration, which leads to more accurate assessments of chemotaxis. In this paper, we propose a three-dimensional model considering a single crawling cell to study its chemotaxis. The semi-implicit Fourier spectral method is applied for high efficiency and numerical stability. The simulation results reveal rich dynamics of cell.
-
In this study, an elastic network model is established in order to find dominant factors which reflect thermostability of protein structures. The connections in the elastic network model are selected with respect to the free energy between alpha-carbons, which is representatives of residues in the elastic network model. We carried out normal mode analysis and compared eigenvalues of the stiffness matrix from the elastic network model. In most cases, thermophilic proteins are observed to have higher values of lowest natural frequency than mesophiles and psychrophiles have. As a result, the thermophiles are calculated to be stiffer than other proteins in view of dynamic vibration.
-
The moyamoya disease is a type of cerebrovascular disease which produces thin abnormal blood vessels like haze in the brain base because the end of internal carotid artery which supplies about 80% of blood is blocked. Regarding this moyamoya disease, the shearing stress and thrombus generation are mentioned as its main causes. This study three-dimensionally implemented the ICA, ACA, and MCA parts of the cerebrovascular configuration related to the moyamoya disease, and analyzed the hydrodynamic phenomenon with the commercial program ADINA. In particular, the correlations between shearing stress and speed distribution according to the branch angle of ACA and MCA. A numerical analysis found that the greater the branch angle of ACA and MCA, the lower the shearing stress and the greater the stationary area of the flow.. Put Abstract text here.
-
Previous reports have introduced the technique of spinous process osteotomy to decompress spinal stenosis, a procedure which aims to afford excellent visualization while minimizing destruction of tissures not directly involved in the pathologic process. However, bio-mechanically it has not been investigated whether the sacrifice of posterior spinous process might have potential risk of spinal instability or not, even though supra-spinous and inter-spinous ligament are preserved. Therefore the aim of this study is to evaluate the bio-mechanical properties after spinous process osteotomiy, using finite element analysis. In the model of spinous process osteotomy the increase of stress in the disc and segmental rangesof motions were not changed significantly. It is due to the fact that the instability of lumbar spine has been maintained by the two-types of ligaments compared with the prior surgical technique. Therefore, according to the finite element result on this study, these osotetomy was considered to be a clinicallysafe surgical procedure and could not cause the instability of patient.
-
Using numerical models, we investigated the efficiency of toxin removal using pulsatile flow in blood purification systems that use semipermeable membranes. The model consisted of a three-compartmental mass transfer model for the inside body and a solute kinetics model for the dialyzer. The model predicted the toxin concentration inside the body during blood purification therapy, and the toxin removal efficiencies at different flow configurations were compared quantitatively. According to the simulation results, the clearances of urea and
${\beta}_2$ microglobulin (B2M) using a pulsatile pump were improved by up to 30.9% for hemofiltration, with a 2.0% higher urea clearance and 4.6% higher B2M clearance for high flux dialysis, and a 3.9% higher urea clearance and 8.2% higher B2M clearance for hemodiafiltration. These results suggest that using a pulsatile blood pump in blood purification systems with a semipermeable membrane improves the efficacy of toxin removal, especially for large molecules and hemofiltration treatment. -
Extra-corporeal Life Support System (ECLS) is the device used in emergency cases to substitute a extracorporeal circulation in open heart surgery, cardiac arrest or in acute cardiopulmonary failure. To obtain the effect of counter-pulsation on hemodynamic response in the ECLS quantitatively, we developed cardiovascular model which consists of 12 compartment model of heldt et al. and 3 compartment model of Schreiner et al. based on windkessel approximation. We compared coronary perfusion, arterial pulse pressure, cardiac output, and left ventricular pressure-volume diagram according to flow configuration such as counter-pulsation, copulsation, and continous flow. When counter-pulsation was applied, 5% higher coronary perfusion, 26% lower pulse pressure, and 2% higher cardiac output than copulsation condition were calculated. We conclude that counter-pulsation configuration in the ECLS is hemodynamically more stable than copulsation and influences the positive effect to recover ventricles.
-
Arrhythmia causes sudden cardiac death. In the past, there were medical limitations in finding the cause of arrhythmia. As an alternative solution for research of arrhythmia, there have been studies to find the causes of arrhythmia by producing a virtual heart model. Medically, arrhythmia has two main causes: abnormal occurrence of action potential and abnormal conduction of action potential. Based on these, the tachycardia, which is one of the arrhythmia, was manifested and the phenomenon of ventricular fibrillation was numerically analyzed in this study. For this purpose, an electrophysiological model of ventricular cells was implemented, which was subsequently applied to the reaction-diffusion partial differential equation to interpret the macroscopic conduction phenomenon in two-dimensional tissues. The ventricular fibrillation refers to a condition where several irregular waves occur in cardiac tissue, whose generation mechanism is pathologically related to the cardiac tissue.
-
In this study, we simulated the atrial arrhythmia numerically. By using electro-physiological model of atrial cell from Nygren et al. and applying reaction-diffusion partial differential equation, we simulated electrical conduction in atrium. A 3-D mesh system representing the human atrium was reconstructed from the surface geometry of atrium. We used a stimulus in the form of an archetype around pulmonary vessels in the left atrium to cause the atrial arrhythmia. The septal atrial tarchycardia was developed after the stimulus.
-
본 연구에서는 심장의 세포 변화에서부터 혈류 순환의 시스템 변화까지 일련의 과정을 시뮬레이션 할 수 있는 통합모델을 개발하였다. 본 통합 모델을 이용하여 대동맥의 탄성도 변화 따른 Pulse Wave Velocity를 추정하였으며 심근의 수축 Mechanics의 변화를 시뮬레이션 하였다. 심장은 단순한 구 형상으로 모델링 되었다. 특히 동맥순환의 특성인 Wave propagation 과 Wave deflection의 현상을 모델링하기 위해 기존 모델에서 사용된 동맥계 순환 모델을 수정하였다. 즉 기존의 동맥 모델을 1차원의 운동방정식과 연속방정식을 기반으로 하는 Distributed arterial model로 대체하였다. Distributed arterial model은 혈액의 점성에 의한 에너지 손실, 혈관의 점탄성 효과 그리고 분지 되는 혈관에서의 에너지 손실을 포함하는 정교한 동맥 순환 모델이다. 정교한 동맥계 순환 모델의 동맥 탄성도 값을 조절함으로써 탄성도 변화에 대한 PWV를 계산 할 수 있었다. 이러한 수치적 방법을 사용하여 노화에 따른 동맥벽 탄성도의 저하가 심근세포의 Cross-bridge 동역학에 미치는 영향을 시뮬레이션 하였다.
-
Pulsatile Extracorporeal Membrane Oxygenation(ECMO) can mitigate the heart load and raise the patient's blood perfusion. But If the ECMO pulsate the blood flow during the systolic period, It can burden to the patient's heart. To avoid the heart injury, we have to consider the relation between output of ECMO, hemodynamic states and heart movement. To raise the efficacy of the pulsatile ECMO, we investigated the coronary perfusion, cardiac muscle tension and hemodynamic states during the ECMO perfusion by using the mathematical model of human blood circulatory system and ECMO. The outflow data of the pulsatile ECMO(T-PLS, Bioheartkorea, Korea) was obtained in vitro experiments. According to the phase and pumping rate of the ECMO, the heart's load and coronary perfusion could be adjusted to the proper levels. The results of the human- ECMO lumped parameter model showed that the synchronizing operation of the pulsatile ECLS can be helpful at stabilizing the patient's hemodynamic states.
-
For direct detection of microbes in air, samples have to be collected but environmental particles such as dust are also trapped in such samples. Therefore the isolation of target bacteria from non-biological materials of similar size is of great importance in the identification of such organisms. Dielectrophoresis is an emerging technique that can rapidly separate cells in microfluidics. In this paper we proposed a new method for the separation of airborne microbes using condensation and dielectrophoresis. This system could be used as a continuous flow through separation system for various particles and utilized as a pretreatment technique for microbe detection.
-
This paper presents the design and experiment results of a multi-layered microsystem for magnetic bead applications. The magneto-microfluidic device is designed for capable of separating magnetic beads. In the presence of the magnetic field, magnetic beads are attracted and moved to high gradient magnetic fields. A multi-layered microfluidic channel consists of top and bottom layers in order to separate magnetic beads in the vertical direction. Our channel is easily integrated magnetic cell sorter, especially on-chip microelectromagnet or permanent magnet device. Fast separation of magnetic beads in top and bottom channels can be used in high throughput screening to monitor the efficiency of blood and drug compounds.
-
In the detection of pathogenic microorganisms ATP-bioluminescence reaction is a fascinating method. ATP(adenosine triphosphate) is an energy source of all kinds of living organism and ATP-bioluminescence reaction uses this ATP. However, ATP exists not only in the cells but also outside the cells. Therefore ATP-bioluminescence reaction only with intracellular ATP is very important in pathogenic microorganism detection. Because of that reason we developed a microfluidic channel containing Dielectrophoretic zone which capture microorganisms and eliminating and washing extracellular ATP with ATP-degarading enzymes, adenosine phosphate deaminase and apyrase. Microorganisms are captured by pDEP force at the DEP electrode zone and only extracellular ATPs are washed and eliminated outside the zone.
-
Micro cell stimulation device is interested in many researchers because it has several advantages such as saving time and reagents. We introduce new micro-bioreactor using micro bead and conduct cell stimulation experiments to verify effective time because cell have operated by cell-cycle (G1, S, G2, and M phase). Micro-bioreactor was made by soft lithography and CAPE (calf pulmonary artery endothelial cell) was cultured in PDMS (polydimethylsiloxane) micro device for 12 hour and cell starvation process was performed for 24 hours. Micro glass beads were rolled only by slating device every hour during 15 hour because of minimizing other stimulation force like flow and pressure. The result represents that cells under exposed under micro bead stimulation show higher growth rate than normal condition and earlier and later stimulation time are more effective.
-
In this paper, we characterize the mechanical properties of PCL strand which is made by oscillating nozzle for tissue engineering scaffold. In order to increase the mechanical properties of the PCL strand, we designed an oscillating nozzle system for the 3D plotting system. First, we check the effect of the nozzle speed (3 to 8 mm/sec), frequency (0 or 300 Hz) and the oscillating amplitude (0 or 100 V) on the diameter of the PCL strand. Second, we observe the effect of the frequency (0, 100, 200 and 300 Hz) and the oscillating amplitude (0, 50 and 100 V) on the mechanical property of PCL strand. The mechanical properties and surface morphology of PCL strand made by oscillating nozzle are compared with the PCL strand made by normal nozzle using Nano-UTM and SEM.
-
The purpose of tissue engineering is to repair or replace damaged tissues or organs by a combination of cells, scaffold, suitable biochemical and physio-chemical factors. Among the three components, the biodegradable scaffold plays an important role in cell attachment and migration. In this study, we designed 3D porous scaffold by Rapid Prototyping (RP) system and fabricated layer-by-layer 3D structure using Polycarprolactone (PCL) - one of the most flexible biodegradable polymer. Furthermore, the physical and mechanical properties of the scaffolds were evaluated by changing the pore size and the strand diameter of the scaffold. We changed nozzle diameter (strand diameter) and strand to strand distance (pore size) to find the effect on the mechanical property of the scaffold. And the surface morphology, inner structure and storage modulus of PCL scaffold were analyzed with SEM, Micro-CT and DMA.
-
The purpose of this study was to examine the effects of various mechanical stimuli for MC3T3-E1 cells. Among the several mechanical stimulations, we focused on compressive stain and ultrasound. In this study, we developed a bioreactor capable of applying controlled stimuli to scaffolds. PLLA/PCL scaffold was fabricated by using salt-leaching method. We performed dynamic cell culture using preosteoblasts MC3T3-E1 cells with 1MHz, 30mW/cm2 ultrasound and 10% of compressive strain. Result of CCK-8 analysis at 1, 4, 7, 10 days showed that mechanical stimuli had no significant effect for cell proliferation. However, those stimuli influenced ALP(Alkaline phopatase) activity, which is one of differentiation marker.
-
Cho, Young-Kuen;Hwang, Sun-Hong;Kim, Hyun-Dong;Kim, Young-Ho;Min, Jin-Young;Kim, Han-Sung;Lim, Do-Hyung 1704
Many studies have emphasized the importance of resistive exercise to maintain a healthy human body, particular in prevention of weakening of physical strength. Recently, some studies advocated that an application of vibration as a supplementary means in a regular training was effective in encouraging physical strength. Aim of the current study was, therefore, to identify if an application of vibration in a resistive exercise was effective in encouraging physical strength as that in a regular training. A 3-dimensional virtual lower extremity model for a healthy male and virtual leg-press model were generated and synchronized. Dynamic leg-press exercises on a slide machine with/without extra load and on a footboard with vibration as well as on a slide machine with extra load were analyzed. The results of the current indicated that the application of the vibration on the dynamic leg-press exercise might be not greatly effective in encouraging physical strength, compared with the dynamic leg press exercise with extra load. It was, however, thought that the application of the vibration might be helpful to elderly individuals because the reduced maximum muscle strength appeared by the effect of the vibration may avoid a muscular spasm, which can be driven from a high muscle strength sometimes produced during the leg-press exercise with extra load. -
The trunk is inclined to the loaded side when carrying an object as one of activities of daily living. As the reaction to this behavior the human body may be inclined to his/her trunk to unloaded side. The present study investigated the biomechanical effects of weight variation for sided load carriage during walking upon joint moments and muscle torques, through the tracker agent and joint driving dynamic analysis. To perform the experiment one male was selected as subject for the study. Gait analysis was performed by using a 3D motion analysis system. Thirty nine 14mm reflective markers, according to the plug-in marker set, were attached to the subject. We used BRG.LifeMOD(Biomechanics Research Group, Inc., USA), for skeletal modeling and inverse and joint driving dynamic simulation during one gait cycle. In walking with a sided load carriage, the subject modeled held the carriage with the right hand, which weighed 0, 5, 10, 15kg, 20kg respectively. The result of this simulation showed that knee and hip in the coronal plane were inclined to the loaded side and loaded side had larger moments as the sided load carriage was increased. On the other hand thoracic and lumbar in the coronal plane had larger negative values as the sided loaded carriage was increased. The thoracic and lumbar in the transverse plane also had larger values as the sided load was increased. And the several muscles of loaded side were increased as increasing sided load. It could be concluded that human body is adopted to side loaded circumstances by showing more biologic force. These results could be very useful in analysis for delivery motion of daily life.
-
We have developed a nanoparticle focusing mask which can generate particle arrays directly on the large area with high resolution. Using this mask, nanomaterials are precisely deposited onto desired positions on a substrate surface. We obtained various sizes of arrays ranging from 80 nm to 6
${\mu}m$ with silver and copper nanoparticles that are generated by a spark discharge and an evaporation-condensation method. The feather size is much smaller than that of mask openings due to the focusing effects, like electrostatic lens, caused by charge or electric potential on insulator mask surface, which also prevent a mask clogging. The particle array size depends on the size of mask open patterns and focusing effects near the mask relate to ion flow rate and electric potential. We have demonstrated that diverse size of arrays with high resolution could be obtained repeatedly using the same sized mask in atmosphere. -
This study explores the influence of volume fraction of nanocrystals of Cu-Zr amorphous alloys on shear band formation. As the number of crystals with very tiny size increases, the strain localization, i.e. shear band, decreases without large drop of flow stress. The DPRs also depict no sudden drop and relatively high values. The strain state during the deformation represents a few shear bands at low volume fraction while there are no distinguishable shear bands at high volume fraction of nanocrystals.
-
In recent years, there has been a remarkable progress in the development of the fiber optic sensors for the detection of various chemicals. Fiber optic sensors have the advantages of very small size, flexibility and low cost. The fiber optic sensors employing different optical or spectroscopic phenomena have been reported such as bulk absorption, optical reflectance, fluoresces and energy transfer. In this study, the effect of nanoparticle concentration in liquid upon light absorption and scattering was studied using extrinsic fiber optic method. For the evaluation, we used Red (650 nm) and Blue (430 nm) light sources which are coupled through the standard cuvette using optical fiber to detector. The experiments are carried out with Polystyrene latex (400 - 800 nm), and Silicon (35 - 110 nm) nanoparticles suspended in Isopropanol. Differences in light absorption and scattering depending on nanoparticle concentration and type are discussed. This method may be useful to study nanoparticles properties for various application and research.
-
We present a facile, yet versatile carbon nanofabrication method using electron beam lithography and resist pyrolysis. Various resist nanopatterns were fabricated using a negative electron beam resist, SAL-601, and were then subjected to heat treatment in an inert atmosphere to obtain carbon nanopatterns. Suspended carbon nanostructures were fabricated by wet-etching of an underlying sacrificial oxide layer. Free-standing carbon nanostructures, which contain 122 nm-wide, 15 nm-thick, and 2
${\mu}m$ -long nanobridges, were fabricated by resist pyrolysis and nanomachining processes. Electron beam exposure dose effects on resist thickness and pattern widening were studied. The thickness of the carbon nanostructures was thinned down by etching with oxygen plasma. An electrical biosensor utilizing carbon nanostructures as a conducting channel was studied. Conductance modulations of the carbon device due to streptavidin-biotin binding and pH variations were observed. -
ZnO thin films with preferred orientation along the (0 0 2) plane were fabricated by a sol-gel method. The effects of the annealing temperature, time, and thickness were studied by investigating UV-visible spectra, FT-IR spectra, and XRD of ZnO films. The films were dried and annealed ed at
$100^{\circ}C,\;200^{\circ}C$ , and$300^{\circ}C$ for 1hr, 2hrs, and 3hrs, respectively. The film showed the preferred (0 0 2) orientation and high transmittance near 90% in the visible range. Also, SEM images of the films exhibited very smooth surfaces without holes and cracks. Schottky diodes were fabricated by using ZnO sol-gel material. Au and Al were used as electrodes to make Ohmic and Schottky contacts, respectively. The annealing temperature, time and the thickness dependent I-V characteristics were presented in this article. -
Dielectrophoretic behavior of semiconducting single-walled carbon nanotubes(SWNT) was investigated theoretically and experimentally. The surface conductance of nanotubes was modulated using anionic and cationic surfactant mixtures. The experimental results indicate that dielectrophoretic behavior of SWNT highly depends on the procedure of mixing two opposite-charged surfactants. Clausius-Mossotti factor was calculated by measuring zeta potentials and solution conductivity. Raman spectroscopy was used to characterize the dielectrophoretically deposited nanotubes arrary. We found that metallic nanotubes were selectively separated from the nanotubes suspension, resulting from modulation of surface conductance of semiconducting SWNT.
-
Kim, Yong-Jae;Choi, Jae-Yong;Son, Sang-Uk;Ahn, Ki-Cheol;Keum, Hyun-Joon;Lee, Suk-Han;Byun, Do-Young;Ko, Han-Seo 1742
An EHD (Electro-Hydro-Dynamic) jet for electrostatic inkjet head shows advantages to print micro-size patterns using various inks because it can generate sub-micron droplets and can use highly viscous inks. Thus, many researchers in industrial fields are concerned about the EHD jet in these days. Since the basic principle of the EHD jet is to form a droplet from an apex of meniscus at the end of the nozzle, the ejection mechanism can be changed by the shape of the meniscus. The stable ejection of the droplet is greatly affected by the shape of the meniscus which is also influenced by surface characteristics of the nozzle, electric potential and ink properties. Experiments have been performed using the nozzles with hydrophilic and hydrophobic coatings in this study. The hydrophobic nozzle forms the stable droplets in wider range of the electric potential than the hydrophilic nozzle does. -
Lee, Jun-Sung;Kim, Young-Jae;Kang, Byeong-Geun;Kim, Sang-Yoon;Park, Jae-Hong;Hwang, Jung-Ho;Kim, Yong-Jun 1747
Electrohydrodynamic jet printing (EHDP) technique is widely used for the direct writing. However, in the existing EHDP method, the printing characteristics are affected by the printing substrate used, and the line width of the printed is determined by the geometry of the nozzle. We propose an EHDP method which is capable of (1) removing the effect from the substrate, and (2) controlling the line width through the ON/OFF control of the each nozzle in the nozzle array. Printing characteristics of our EHDP system were examined and successful ON/OFF control of the nozzle array were demonstrated. By using the proposed EHDP, it is expected that stable meniscus regardless of the substrate and different line widths even using the same nozzle can be achieved. -
Simple and highly efficient droplet merging method is proposed, which enables two nanoliter or picoliter droplets to merge regularly in a straight microchannel. We observe that two droplets of the same size but of different viscosities are merged by velocity difference induced as they are transported with the carrier fluid. To make viscosity difference, the mass ratio of water and glycerol is varied. Two droplets of the same size or of different sizes are generated alternatingly in the cross channel by controlling flowrates. This droplet merging method can be used to mix or encapsulate one target sample with another material, so that it can be applied to cell lysis, particle synthesis, drug discovery, hydrogel-bead production, and so on.
-
Under typical operating conditions, flows in microfluidic devices are laminar and molecular diffusion across the channels is slow, which makes an efficient mixing in microfluidic devices difficult to achieve. The mechanism to achieve effective mixing in laminar flows is that of repetitive stretching and folding. Essential is to generate spatially periodic flows with crossing cross sectional streamlines. A mapping method is employed to analyze mixing in micromixers, enabling us to investigate the progress of mixing both qualitatively and quantitatively. The progress of mixing is characterized by a measure of mixing, called the discrete intensity of segregation. The mapping method is applied to mixing in such micromixers as the staggered herringbone mixer, the barrier embedded micromixer, and the three-dimensional serpentine channel to demonstrate the capability of the numerical scheme to tackle general mixing problems in microfluidic devices.
-
This paper deals with a novel autocalibration method of three-axis micromachined accelerometers applied to a new golf swing diagnosis equipment for golfers. This diagnosis equipment can help golfers monitor and anlalyze their swing posture and therefore modify their swing action to get better score and enjoy their lives through golf. The micromachined accelerometers to get information of the motion are the essential part of the putting club to measure the three-axis acceleration as accurately as possible. This paper presents an efficient autocalibration algorithm to find the offset and sensitivity of accelerometers by only using the static measurement data at six different positions. The experimetnal results on the developed putters show the validity of the proposed algorithm for the new smart putter.
-
A microcantilever is a well-known MEMS structure for sensing bio-chemical molecules. When bio-chemical molecules are adsorbed on the microcantilever's surface, resonance frequency shift is generated. There are two issues in this phenomena. The first one is which one between mass change and surface stress change effects is more dominant on the resonance frequency shift. The second one is what will be the performance change when the boundary condition is changed from cantilevers to double clamped beams. We have studied the effect of surface stress change and compared it with that of mass change by using FEM analysis. Furthermore, for microstructures having different boundary conditions, we have studied Q-factor, which determines the detection limit of micro/nano mechanical sensors.
-
The proper orthogonal decomposition(POD) is used to the modal analysis of microcantilever of dynamic mode atomic force microscopy(AFM). The proper orthogonal modes(POM) are extracted from vibrating signals of microcantilever when it resonates and taps the sample. We present recent ideas based on POD and detailed experiments that yield new perspectives into the microscale structures. The linearized modeling technique based on POD is very useful to show the principal characteristics of the complex dynamic responses.
-
A compact and two-dimensional atomic force microscope (AFM) using an orthogonal sample scanner, a calibrated homodyne laser interferometer and a commercial AFM head was developed for use in the nanometrology field. The x and y position of the sample with respect to the tip are acquired by using the laser interferometer in the open-loop state, when each z data point of the AFM head is taken. The sample scanner which has a motion amplifying mechanism was designed to move a sample up to
$100{\times}100{\mu}m^2$ in orthogonal way, which means less crosstalk between axes. Moreover, the rotational errors between axes are measured to ensure the accuracy of the calibrated AFM within the full scanning range. The conventional homodyne laser interferometer was used to measure the x and y displacements of the sample and compensated via an X-ray interferometer to reduce the nonlinearity of the optical interferometer. The repeatability of the calibrated AFM was measured to sub-nm within a few hundred nm scanning range. -
Molecular dynamics (MD) simulations are used to analyze behavior of copper nanowires under cyclic loading. The embedded atom method (EAM) potential is employed to represent atomic interaction. Cyclic load is applied in two ways (Forward Tension / Reverse Compression and Forward Compression / Reverse Tension). The results show that dislocations are piled up as a result of plastic deformation during alternate tensile and compressive loading. After cyclic loading with a change of direction, yield stress decreases in consequence of the effect by the dislocation pileups. On the other hand, under FC/RT cyclic load, phase transformation represent associated with mechanical twinning. And copper nanowire can return to almost former undeformed condition during tensile loading at 300K.
-
Classical molecular dynamics simulations (MDS) were conducted to simulate nano-sized cluster collisions with a weakly attractive static surface. Energy exchanges associated with the cluster collision and the adhesion probability are discussed. Routes of the energy exchanges and the kinetic energy loss are vastly altered in their mode according to the cluster incident velocity. In the elastic collision regime (
$V_0$ <0.1), most incident kinetic energy is recovered into the rebounding kinetic energy, but a little loss in the incident kinetic energy causes the cluster adhesion. Dissipated kinetic energy is converted into the rotational energy. In the weakly plastic collision regime (0.1<$V_0$ <0.3), the transition from elastic to plastic collision occurs, and a large part of the released potential energy is converted into rebounding translational energy. For strongly plastic collisions ($V_0$ >0.3), permanent cluster deformation occurs with extensive collapse of the lattice structure inducing a solid-to-solid phase transition; moreover, most of the cluster kinetic energy is converted into cluster potential and thermal energy. -
The effect of misfit on the indentation behaviour of silver coated copper multilayer was studied by molecular dynamics simulation. It was found that the misfit bands on interface formed by the mismatch of lattice structure between copper and silver in slip direction [110] and the dislocation band width depended on the mismatched lattice constants of materials. More dislocations were created and glided by indentation, which created a "four-wing flower" structure consisting of pile. up of dislocation at the interface. The size of "flower" depended on the thickness of silver layer. The critical thickness for "flower" was approximately 4nm above which the "flower" disappeared. As the result, deformation mechanisms such as dislocation pile-up, dislocation cross-slip and movement of misfit dislocation were revealed. Only silver atoms in the dislocation pile-up were involved in the creation of the "flower" while the dislocations in copper were glided in slip direction on interface.
-
A "finite volume method" is proposed to predict heat transport in a spherical enclosure at micro/nanoscale with the Boltzmann transport equation (BTE). The gray version of the BTE with the relaxation time approximation has been applied. Pointing out similarity between radiative transfer equation (RTE) and BTE, the mapping process in RTE is adopted to treat the angular derivative term and linear algebraic discretization equation is derived by using the established method which is used in 2-D BTE in cartesian coordinates. The simulation results are compared to exact solution to RTE for various acoustic thicknesses and ratio of radii. The comparison shows that this method is logical and accurate, and it is possible to easily adopt various models in spherical BTE.
-
Study that form micro pattern by direct ink jet printing method is getting attention recently. Direct ink jet printing spout fine droplet including nano metal particle by force or air pressure. There is reason which ink jet printing method is profitable especially in a various micro-patterning technology. It can embody patterns directly without complex process such as mask manufacture or screen-printing for existent lithography. In this study, research of a technology that ejects fine droplet form of Pico liter and forms metal micro pattern was carried with inkjet head of piezoelectricity drive system. Droplet established pattern while ejecting consecutively and move on the surface at the fixed speed. Patterns formed in ink are mixed with organic solvent and polymer that act as binder. So added thermal hardening process after evaporate organic solvent at isothermal after printing. I executed high frequency special quality estimation of CPW transmission line to confirm electrical property of manufactured circuit board. We tried a large area printing to confirm application possibility of an ink jet technology.
-
A small L-type megasonic module for nano-pattern cleaning was designed and manufactured. The impedance graph of the quartz waveguide with a piezoelectric actuator was predicted using finite element method (FEM). The peak value of the piezoelectric actuator alone was 3.373 MHz, which was the same as the experimentally measured value of 3.373 MHz (0.0% error). In addition, the maximum impedance value of the quartz waveguide with the actuator was 3.373 MHz, which agreed well with the measured value of 3.362 MHz (0.3% error). The acoustic pressures of a conventional megasonic system (3 MHz) and the developed system under similar conditions were measured and compared. The results showed that the maximum values and standard deviations of the developed system decreased by 29% and 18%, respectively, compared with the conventional type. This suggests that the small L-type would have higher particle removal efficiency with lower possibilities of pattern damages.
-
Self-catalytic behavior of combustion-synthesized carbon nanotubes (CNTs) is evaluated using a double-faced wall stagnation flow burner with a CNT-deposited stainless steel plate wall. CNT formation is observed using field-emission scanning and transmission electron microscopies and Raman spectroscopy. A self-catalytic behavior of multi-walled CNTs (MWCNTs) shows the enhanced ratio of channel diameter to tube wall thickness and the enhanced intensity ratio of G-band to D-band in Raman spectroscopy, implying that the quality of metal-catalytic, flame-synthesized MWCNTs can be much improved via a CNT self-catalytic flame-synthesis process. Thus, using a DWSF burner through the self-catalytic process has potential in mass production of CNTs having much improved quality.
-
A novel in-mold packaging process has been developed to manufacture devices with closed channels. In this unified process, fabrication of open channels and forming the rigid cover on top of them are sequentially integrated in the same mold. The entire process is comprised of two phases. In the first phase, the open channels are fabricated under an exquisitely controlled temperature and pressure using the conventional micro injection molding technology. In the second phase, the closed channels are fabricated by conducting the injection molding process using the molded structure with the open channels as a mold insert. As a result, the in-mold technology can eliminate the bonding processes such as heating, ultrasonic or chemical processes for cohesion between the channel and the cover, which have been required in conventional methods.
-
A simple method for the fabrication of porous nano-master for antireflective surface is presented. In conventional fabrication methods for antireflective surface, coating method with low refractive index has usually been used. However, it is required to have high cost and long times for mass production. In this paper, we suggested the fabrication method of antireflective surface by the hot embossing process using the porous nano patterned master on silicon wafer fabricated by low-temperature anodic aluminum oxidation. Through multi-AAO and etching processes, nano patterned master with high aspect ratio was fabricated at the large area. Pore diameter and inter-pore distance are about 150nm and from 150 to 200nm. In order to replicate anti-reflective structure, hot embossing process was performed by varying the processing parameters such as temperature, pressure and embossing time etc. Finally, antireflective surface can be successfully obtained after etching process to remove selectively silicon layer of AAO master.
-
This paper reports a novel gas sensing method by using a thermoelectric device, thermopile in this case, with an embedded tin oxide catalyst. By using a thin catalyst film, the response time and recovery time were remarkably improved. The fabricated gas sensor was characterized through detecting NOx gas with various concentrations.
-
Recently as the micro surface features become higher and diverse in their shapes, the releasing of the molded features becomes more crucial for manufacturing of the micro patterned products. The higher aspect ratio of the features or more complex shape of the features results in larger releasing force, elongation or cohesive failure of the features during the releasing. Another issue would be the uniformity of the released surface features after molding, especially for applications with large area surface. The micro patterned optical film, one of typical applications for micro surface features, consists of two layers, the thermoplastic base film and the micro formed UV resin layer. Therefore two interfaces are typically involved during the forming of this micro featured film; one is between the base film and the UV resin and another is between the resin and the pattern master. To improve the releasing of the molded surface features, the adhesive characteristic was investigated at these two interfaces. A PET film was used as a base film and two UV curable resins with different surface energy were prepared for different adhesiveness. Also the two different pattern masters were employed; one is made from brass-copper alloy and fabricated with PMMA. The adhesiveness at each interface was measured for some combinations of these base film, UV resins and the masters and the effect of this adhesiveness on the releasing was investigated.
-
The purpose of this study is to investigate the properties of the AAO nanohoneycomb structure. Especially the Elastic modulus and hardness play important role in determining the mechanical deformation of ceramic materials. The mechanical properties of the AAO nanononeycomb structure were investigated using indentation test.
-
This work reports development of novel liquid-level sensors based on the
$3{\omega}$ method. The sensors determine the liquid level by measuring the thermal response as in the conventional hot-wire technique. However the sensors employ an AC heating method to enhance the sensitivity, noise resistance and time response. Also, the microfabricated thin-film structure of the sensor provides mass-producibility as well as improved sensor performance owing to the increase in the surface-volume ratio of the sensor. Two different types of the sensor are developed: one for point detection of the fluid phase and the other for monitoring continuous variation of liquid level. Notable is that the performance of the sensor is not considerably affected by the liquid flow. -
Kim, Woo-Song;Park, Gyeong-Seo;Nam, Jin-Hyun;Yim, Hong-Jae;Jang, Si-Yeol;Lee, Kee-Sung;Jeong, Jay;Lim, Si-Hyeong;Shin, Dong-Hoon 1847
The process conditions during ultraviolet nanoimprint lithography (UV-NIL) process such as temperature, stamping pressure, UV irradiation, etc. are effective factors for successful imprinting of complex and fine patterns. In this study, the effects of aluminum mold on the thermal characteristics of UV-NIL process were investigated through imprinting experiments and numerical simulations. The temperature of polymer resin on mold was measured to study thermal characteristics during UV curing. From the experimental and numerical results, the importance of curing reaction control for UV-NIL process was discussed for deformation characteristics. -
A numerical program based on computational fluid dynamics has been developed to simulate characteristics of an EHD induction micropump. The ambiguity of boundary conditions was removed by adopting an equation formulated for electric potential as the dependent variable. The calculations show that the dependency of frequency agrees well with the experiments and the previous analysis. The instability, caused by backflows, is getting stronger as the channel depth increases, which is consistent with experiments. The present study reveals that it is due to the limit in the penetration depth which the electric field can affect. Despite the disadvantage of large channel depth, there is a certain optimal depth for the maximum flow rate.
-
Resonant frequency tuning of micro devices is essential to achieve performance uniformity and high sensitivity. Previously reported frequency tuning methods using electrostatic force or mass deposition are not directly applicable to non-conducting polymer devices and have limitations such as dielectric breakdown or low tunable bandwidth. In this paper, thermally frequency-tunable microactuators with poly-dimethylsiloxane membranes are proposed. Permanent and/or nonpermanent frequency tunings are possible using a simple temperature control of the device. Resonant frequency and Q-factor variations of devices according to temperature change were studied using a micro heater and laser Doppler vibrometer. The initial resonant frequencies determined by polymer curing and hardening temperatures are reversibly tuned by thermal cycles. The measured resonant frequency of 9.7 kHz was tuned up by
${\sim}25%$ and Q-factor was increased from 14.5 to 27 as the micro heater voltage increased from 0 to 70 V. -
In an electrospinning process, nanofibers are produced from a droplet of a viscoelastic polymer solution subjected to strong electric field. To date, intrinsic bending instability of the electrical jets has resulted in random piles of nanofibers on a grounded collector plate. Here we report a novel electrospinning process where a hollow micropillar is constructed by the coiling of nanofibers on a sharp grounded collector. We show that the hollow microstructure formation can be explained by the viscous fluid rope coiling theory. The current process can be employed for the fabrication of three-dimensional scaffolds for cell culturing and the three-dimensional nanoprinting.
-
In this work, to make it possible to generate glow discharge in atmospheric pressure condition with relatively high and wide electric field, micro channel reactor is proposed. Si DRIE and Cr deposition by Ebeam evaporation is used to make channel and bottom electrode layer. Upper electrode is made from ITO glass to visualize discharge within micro channel. Fabricated reactor is verified by generating uniform glow plasma with N2 / He gases each as working fluid. The range of gas electric field to generate glow plasma is from about 200 V/cm and upper limit is not observed in tested condition of up to 150 kV/cm. This data shows that micro channel plasma reactor is more versatile. Indirect estimation of electron temperature in this reactor can be inferred that the electron temperature within glow discharge in micro reactor lies
$0{\sim}2eV$ . This research demonstrates that the reactor is appropriate in application that needs to maintain low temperature condition during chemical process. -
It is not easy to detect nano-sized airborne particles (< 100 nm in diameter) in air. Therefore, the condensation of the nanoparticles alongside of the size-classification is needed for their detection. This paper proposes a hybrid (aerodynamic+electrical) particle classification and condensation device using a micro virtual impactor (
${\mu}VI$ ). The${\mu}VI$ can classify the nanoparticles according to their size and condense the number concentration of nanoparticles interested. Firstly, the classification efficiency of the${\mu}VI$ was measured for the particles, polystyrene latex (PSL), ranging from 80 to 250 nm in diameter. Secondly, the nanoparticles, NaCl of 50 nm in diameter, were condensed by 4 times higher. In consequence, the output signal was amplified by 4 times (before condensation: 4 fA, after condensation: 16 fA). It is expected that the proposed device will facilitate the detection of nanoparticles. -
Cleaning is required following CMP (chemical mechanical planarization) to remove particles. The minimization of particle residue is required with each successive technology generation, and the cleaning of wafers becomes more complicated. In copper damascene process for interconnection structure, it utilizes 2-steop CMP consists of Cu CMP and barrier CMP. Such a 2-steps CMP process leaves a lot of abrasive particles on the wafer surface, cleaning is required to remove abrasive particles. In this study, the buffing is performed various conditions as a cleaning process. The buffing process combined mechanical cleaning by friction between a wafer and a buffing pad and chemical cleaning by buffing solution consists of tetramethyl ammonium hydroxide (TMAH)/benzotriazole(BTA).
-
3-D heterogeneous nucleation was simulated by classical molecular dynamics (MD), where the Lennard-Jones (LJ) gas and solid cluster-seed molecules have argon and aluminum properties, respectively. There are three shapes of cluster-seeds, cube, rod, and sphere, and three classes of masses and the simulation took place under nine supersaturation ratios, making a total of 81 calculations. Results show that the dimension of the cluster-seed highly affects the rates of cluster development. In order to analyze heterogeneous nucleation above and below the critical supersaturation ratio, growth rate and liquefaction rate were separately defined to supplement the investigation. Design of experiments (DOE) was used for analysis which displayed that the shape and mass of the cluster-seed are prominent for the growth rate, while the supersaturation ratio is most significant followed by the mass for liquefaction rate. The significance of the supersaturation ratio for overall liquefaction suggests that thermal diffusion is more dominant than mass interactions for this system.
-
Water covers 70% of the earth's surface and the human body consist of 75% of it. It is clear that water is one of the prime elements responsible for life on earth. Over the last 30 years or so, numerous studies have attempted to find out more about the water microscopically. In this paper, we investigated how the receding and advancing contact angle of the moving water droplet changes on a solid surface having various LJ epsilon parameters. To observe the dynamic contact angle history, a body force applied to all water molecules after obtained the water droplet in equilibrium with the solid surface. We obtained the density profile and receding and advancing contact angle of the moving water droplet
-
Single crystalline copper nanowires are subjected to bending tests using molecular dynamics simulations and the embedded atom method. To observe behaviors of nanowire, bending tests are performed for various rates of deflection and different boundary conditions: fixed-free and fixed-fixed. When the deflection of nanowire becomes large, twinnings and dislocations appear, and <100> crystal structure transforms to <110>. At high rates, phase transformation occurs in whole nanowire. But, at low rates, atomic structure changes to <110> phase partially. The final deformed structures are affected by the rate of deflection and boundary conditions. These effects can be important design parameters at nanoscale.
-
The current work presents a design and fabrication technique for a microchannel system to measure the local temperature distribution inside microchannel. This micro channel system fabricated by MEMS technique is integrated with a heater and an array of temperature sensors so that detailed heat transfer phenomena inside micro-scale channel can be studied. Materials widely used in semiconductor process were selected to fabricate a heater and temperature sensors on a silicon wafer. On these heater and sensors a channel wall was fabricated with SU-8. The friction constant and the local Nusselt number distribution measured for the deionized water flow in the microchannel is presented.
-
Conductive polymers, prepared by mixing electrically conductive fillers with a suitable polymeric formulation, are widely used in applications such as interconnecting materials for high density electronic packaging. However, resins of conductive pastes used as binders and vehicles are generally nonconductive, so that they may prevent the electrical contact between conductive fillers and reduce electron transmission. In this study, we improved conductivity of silver paste by the incorporation of cabon nanotubes. It is important to achieve homogeneous dispersion of CNTs to act as reinforcements efficiently in matrix. We carried out acid treatment on nanotubes for their homogeneous dispersion in silver/conducting polymer matrix. The dispersion states of nanotubes were characterized by raman spectra and filed emission scanning electron microscope. The electrical resistivity of CNTs incorporated silver paste was also measured by 4-point probe method.
-
Electrohydrodynamic (EHD) printing has gained significant interest after a direct writing with a resolution of a few tens nanometer was demonstrated using EHD. Basically, EHD use the electric field to generate droplet which is much smaller than nozzle diameter, so that high resolution printing is possible and the clogging problem can be alleviated as well. However, to adapt this technology to the real application, the fundamental studies are necessary to stabilize EHD jetting, to maximize jetting frequency, and to optimize the design of multi EHD nozzle, etc. In this study, by imaging EHD jetting using high speed camera and measuring the current, the effect of electric field intensity and back pressure on jetting frequency and jetting diameter were studied.
-
Choi, Won-Ho;Shin, Yoon-Hyuk;Yeo, Min-Ku;Yim, Hong-Jae;Sin, Dong-Hun;Jang, Si-Youl;Jeong, Jay-Il;Lee, Kee-Sung;Lim, Si-Hyung 1917
Ultraviolet-nanoimprint lithography (UV-NIL) is promising technology for cost effectively defining micro/nano scale structure at room temperature and low pressure. In addition, this technology is fascinating because of it's possibility for high-throughput patterning without complex processes. However, to acquire good micro/nano patterns using this technology, there are some challenges such as uniformity and fidelity of patterns, etc. In this paper, we have focused on uniform contact mechanism and performed contact mechanics analysis. The dimension of the flexible sheet to get adequate uniform contact area has been obtained from contact mechanics simulation. Based on this analysis, we have made a uniform pressurizing device and confirmed its uniform pressurized zone using a pressure sensing paper. -
In the present study, deposition of discrete and small particles, which diameter is less than
$1{\mu}m$ , on a filter element was simulated by stochastic method. Trajectory of each particle was numerically solved by Langevin equation and Brownian random motion was treated by Brownian dynamics. Lattice Boltzmann method (LBM) was used to solve flow field around the filter collector and deposit layer. Interaction between flow field and deposit layer was obtained from a converged solution from an inner-loop calculation. Simulation method is properly validated and collection efficiency due to different filtration parameters are examined and discussed. Morphology of deposit layer and its evolution was visualized in terms of the particle size. The particle loaded effect on collection efficiency was also discussed. -
In this paper, elastic properties such as Young's modulus and Poisson's ratio of various transition metal nanofilms are calculated for the {100} and {110} surfaces by using molecular dynamics simulation. A new method using
$3^{rd}$ order elastic constants and least square method is presented for the calculation of elastic constants. We also introduce analytical method of calculating elastic constants for EAM potential and it's results as the reference value to be compared with the simulation results. -
Formation of air bubble is the one of common defects in UV nano imprint lithography. Location of dispensing and volume of droplets are among the most important parameters in the process. ]n this study, UV curable resin droplets with different volumes were dispensed at different locations and pressed to investigate air bubble formation. By varying volume of droplet and dispensing location, process conditions were found for minimum air bubble area.
-
Deformation of a mold is measured and analyzed in alignment and curing processes of UV-Imprint Lithography. We are focused on mold deformation caused by a UV resin, which is laminated between a mold and a target glass-panel. The UV resin is viscous in case of liquid state, and the resin will be solidified when being exposed by the ultra-violet light. The viscosity of the resin causes shear force on the mold during the alignment process. Moreover, the shrinkage during phase change from liquid to solid may cause residual stress on the mold. The experiments for measuring temperature and strain are made during alignment and curing process. Strain-gages and thermocouples are used for measuring the strain and variation of temperature on several points of the mold, respectively. The deformation of mold is also simulated and analyzed. The simulation results are compared with the experiments. Finally, sources of alignment errors in large area UV-nanoimprint lithography are discussed.
-
This paper analyzed orientation simulation of Stewart platform which is a parallel manipulator of 6-DOF. When platform shape had been given, inverse kinematics as the problem about length of actuator could get an answer using a vector function simply, and forward kinematics as the problem solving shape of platform through the length of actuator could get answer using repetitive and manual explaining Newton-Raphson method because it is expressed a high nonlinear polynomial expression. In addition, for control the Stewart platform it could drive simply and it could confirm the state of orientation in real-time.
-
Choe, Jae-Yong;Kim, Yong-Jae;Son, Sang-Uk;An, Gi-Cheol;Lee, Seok-Han;Go, Han-Seo;Nguyen, Vu Dat;Byeong, Do-Yeong 1947
Printing technology is a very useful method in the several process of industrial fabrication due to noncontact and fast pattern generation. To make micro pattern, we investigate the electrostatic induced inkjet printer head for micro droplet generation and drop-on-demand jetting. In order to achieve the drop-on-demand micro droplet ejection by the electrostatic induced inkjet printer head, the pulsed DC voltage is supplied. In order to find optimal pulse conditions, we tested jetting performance for various bias and pulse voltages for drop-on-demand ejection. In this result, we have successful drop-on-demand operation and micro patterning. Therefore, our novel electrostatic induced inkjet head printing system will be applied industrial area comparing conventional printing technology. -
Various MEMS accelerometers are used in engineering applications including automobiles, mobile phones, military systems, and electronic devices. Among them, the thermal accelerometer employing the temperature difference induced by the convective flow inside the micro cavity has been a topic of interest. As the convective sensor does not utilize a solid proof mass, it is compact, lightweight, inexpensive to manufacture, sensitive and highly endurable to mechanical shock. However, the complexity of the convective flow and various design constraints make optimization of a device a crucial step before fabrication. In this work, optimization of a 2-axis thermal convective MEMS accelerometer is conducted based on 3-dimensional numerical simulation. Parametric studies are performed by varying the several design variables such as the heater shape/size, the cavity size and types of the gas medium and the position of temperature probes in the sensor. The results of optimal design are presented.
-
As a field of MEMS, micro-heater fabricated by Au is being introduced and developed in recent years. Previous studies about thermal properties of various forms of micro-heater were not sufficient. In this work, numerical and experimental analysis of the heat generation and the temperature distribution of micro-heater packages for 8 different geometric cases were studied. We fabricated a micro-heater package with silicon wafer, on which Cr/Au layer was laminated before 8 geometric forms of micro-heater were patterned. In each cases, temperature distribution was measured with IR thermal camera. According to the experimental results, which show a good agreement with the results analyzed by CFD, it was found that at 0.5W, the temperature of micro-heater chip which contained
$20000{\mu}m$ -long, serpentine shaped micro-heater was elevated to a relatively high temperature of$78^{\circ}C$ Consequently, we proposed a geometry of micro-heater which has effective thermal characteristics. -
We fabricate and evaluate the metal-oxide-semiconductor (MOS) transistor probe with the focused-ionbeam (FIB) for surface electric properties. The probes are designed with the rectangular and V-shaped structures, and their dimensions are determined considering the contact mode operation. The conductive nano tip is grown with FIB system, and deposition condition is controlled for the sharp tip. The fabricated device is applied to the various test patterns like the metal lines and PZT poling regions, and the results show the well defined measurement patterns.