In this study, the design of prestressed die for spur gear forging have been investigated. The stress concentration at notch of the die insert is very important in the design of die for the forging of spur gear such as non-axisymmetric geometry. In the previous study, the flexible tolerance method was used in order to search the optimal value of design variables considering the constrain conditions. In the design process, it was also involved the safety factor to the yield strength of each ring by considering allowable tensile or compressive hoop stress in each ring. Using this technique, the die deign for spur gear forging has been successfully performed without yielding of the die after shrink fitting and during forging.

This paper explains the die cooling method for improving tool life in the hot forging process. In continuous forming operation such as hot forging process, performed at high speeds, temperature increases of several hundred degrees may be involved. Die hardness was reduced due to thermal softening. Factor of die fracture are wear and plastic deformation of die due to hardness reduction by high temperature. Because die service life was reduced due to this phenomenon during hot forging, quantified data for optimal die cooling method is required. The new developed techniques for predicting tool life applied to estimate the production quantity for a spindle component and these techniques can be applied to improve the tool life in hot forging process

In closed-die forging process, blocker has been used to fill and distribute metal well in finisher die. Generally, the blocker shape was determined by an expert with many experiences. However, the manual blocker design process takes much time and efforts, so various automatic methods for the blocker design process have been suggested for the last three decades. The method with filtering in FFT (Fast Fourier Transform) for the blocker design provides general solution than other methods. But, due to the properties of FFT in time-frequency domain, this method has some drawbacks such as long calculation time, difficulty of local control and additional boundary process after filtering. In this study, DWT (Discrete Wavelet Transform), which is more flexible and is more wildly used than FFT, is applied to the blocker design. The method with filtering in DWT is very proper to design blocker in both 2-D and 3-D shapes. To verify the efficiency of this method, blockers of some models are designed and the results show that blocker design with DWT is effective fer the blocker designs

Cold forging has several advantages as compared with conventional forming by cutting process. In this study, the elastic deformations of straight bevel gear and die induced by cold forging process are investigated to use 3D-Scanner. So we could estimate the total elastic deformation as comparing between forged bevel gears and die. And finite element analysis has been performed to predict the elastic deformation, each of cold forged bevel gear and die. The predicted values are compared with the experimental values and as a result they are well agreed with experimental data.

The dimensions of die and workpiece are changed continuously during loading, unloading, and ejecting stage. Finally, to predict precisely the dimension of forged part and get the die dimension for the net-shape components, the analysis of die and workpiece should be evaluated from the loading to ejecting. Therefore, the experimental and FEM analysis are peformed to investigate the elastic characteristics at workpiece and die in the closed-die upsetting for ferrous material. FE techniques are proposed to consider the unloading and ejecting stages and estimate more precisely the dimension of forged part and die. The dimensional changes for the workpiece were evaluated quantatively during loading, unloading, and ejecting stages. The strains measured by the strain gages were compared with the estimated values by the FEM.

In metal working, cold forging that has profit to satisfy dimension accuracy is using in various manufacturing products. Recently, most of the interest thing is precision forging of gear, Gear forging product is more strength than broaching gear, and it has many advantages with reduction of factory expenses. The reason of difficulty to improve accuracy of gear dimension compare to another products is the dimension accuracy is very high, approximately 10$\mu\textrm{m}$, and because die of involute teeth and elastic strain of forged tool differ from standard curve. This paper represent quantitative analysis of die and teeth of forged tool, namely difference of curves, with experiments and analyze the factor of dimension gap, finally, will design compensated involute curve.

The effects of nitrogen on the deformation behavior of duplex stainless steel have been studied The variation of strength was correlated with the characteristic microstructures. Analysis based on Hall-Petch relation confirmed that nitrogen enhances phase-boundary strengthening effect. The evolution of dislocation structure, slip traces, and misorientation distribution during deformation were also characterized to elucidate the effect of nitrogen on inelastic deformation mechanism.

The disappearance of continuous yielding and the formation of an extended region in engineering stress-strain curves at tempering temperatures of 673-873K is closely related to the reduction of mobile dislocations during tempering and dynamic recovery during tensile deformation. In addition, the occurrence of discontinuous yielding at tempering temperature above 923K would be attributed to the formation of new strain-free polygonal ferrite grain.

The purpose of this study is to investigate the high temperature deformation behavior of Ti-6Al-4V alloy and to predict the final microstructure under given forming conditions. Equiaxed and widmanstatten of Ti-6Al-4V alloys were prepared as initial microstructure and the compression tests were performed to obtain the flow curves at high temperatures (700∼1100$^{\circ}C$) and various strain rates (10$\^$-4/∼10$^2$/s). Form the results of compression test various parameters such as strain rate sensitivity (m) and activation energy (Q) were calculated and used to establish constitutive equations. To predict the final microstructure after forming, finite element analysis was performed considering the microstructural parameters such as the grain size and the volume fraction of second phase.

In the field of automobile industry, suspension parts have been fabricated by the light metal part to substitute the steel part. For application light metal of suspension parts, mechanical property of high strength was performed. For anting semi-solid die casting of suspension part, die filling and solidification simulation have been carried out with Ostwald-de Waele rheological model. We designed the optimal die and secured injection condition as possible as laminar flow based on the result of computer simulation. Mechanical properties of knuckle part and heat treatment condition were investigated.

The effects of microstructural features on the fracture behaviors, including impact, high-cycle fatigue, fatigue and crack propagation, of thixoformed 357-T5 (Al-7%Si-0.6%Mg) alloy were examined. The resistance to impact and high-cycle fatigueof thixoformed 357-T5 tended to improve greatly with increasing solid volume fraction. An almost three-fold increase in impact energy value was, for example, observed with increasing solid volume fraction from 59 to 70%. The improvement in both impact and fatigue properties of thixoformed 357-75 with increasing solid volume fraction in the present study appeared to be related to the magnitude of stress concentration at the interface between primary and eutectic phase, by which the fracture process was largely influenced. Based on the fractographic and micrographic observations, the mechanism associated with the beneficial effect of high solid volume fraction in thixoformed 357-T5 alloy was discussed.

Semi-solid processing is now becoming of great interest for the production of various parts by pressure die casting. Many advantages are associated with this forming process at the condition that the forming operation is performed under appropriate conditions in terms of alloy microstructure, injection velocity and pressure. In this study, to look into the relation along them, the experiment of semi-solid die casting has been peformed with various condition of injection, and investigated their microstrucure and solid fraction

When workability at the a certain bulk deformation process is defined as the maximum plastic deformation capability that the workpiece can sustain without causing any cracks or fracture, the workability is dependent on the microstructure, initial workpiece shape, stress state developed during the deformation process, strain rata and presence of the interfacial friction between workpiece and tool. For a review purpose, the workability definition and test methods are summarized depending on the applied stress state at bulk deformation process in Table 1 at the text. In this study, the cold workabilities of as-cast A16061 bulk material have been measured and comparatively analyzed at the primary tensile stress state by using tensile specimens, the primary compressive stress state by using cylindrical specimens, and the forming limit diagram by ductile fracture.

Generally, forging process has been known to enhance most of the mechanical properties by developing the continuous metal flow across the forged stocks. However, we have found out that forging of Al 6061 did not always give the enhancement of the mechanical properties but the degradation of the original characteristics, especailly for a extruded Al 6061. There are several candidates for the culprit of this unfavorable phenomenon. We have been trying to clear out the cause of the mechanical degradation of the forged a extruded Al 6061. One of the most plausible causes seems to be that the particles containing Mn and/or Cr is coarsened and redistributed preferencially onto grain boundaries due to a repetitive exposure in an elevated temperature condition. On the other hand, a continuously cast Al 6061 did not show any strength degradation after a hot forging under the same process condition with the extruded Al 6061.

Microstructural evolution and dry sliding wear behavior of ultra-fine grained 5052 Al alloy obtained by an accumulative roll-bonding process have been investigated. After 7 ARB cycles, ultra-fine grains with large misorientations between neighboring grains were obtained. The grain size was about 0.2$\mu\textrm{m}$. The hardness, tensile and yield strengths of the ultra-fine grained alloy increased as the amount of accumulated strain increased with the ARB cycles. Sliding wear teats of the ultra-fine grained 5052 Al alloy were conducted at room temperature. Wear rate of the ultra-fine grained alloy increased in spite of the increase of hardness. Surfaces of the worn specimens were examined with SEM to investigate wear mechanism of the ultra-fine grained alloy.

The forging of Al 6061 has been studied by using finite element analysis and real forging experiment to find out the effect of strain rate and strain on the final forged product. It seems to be well known that the mechanical properties depend on the microstructures of forged products. The hot deformation of Al alleys including Al 6061 has been researched quite a long period on the various aspects. However, the forging of Al alloys seem to have few information, especially the recrystallization, recovery and grain growth. To elucidate the process variables to control those microstuctual aspects the specially designed model was used for finite element simulation and forging experiments, in which the variation of strain and strain rate could be obtained. The effect of strain md strain rate has been related with the microstructures of forging stocks.

Asymmetric rolling of AA1050 Al alloy sheets was performed to obtain the shear textures for improving the deep drawability and the grain refinement. The effect of roll velocity ratio on the texture and the grain refinement of 50％ asymmetrically rolled sheets was studied. The textures of the asymmetrically rolled sheets after annealing at 400$^{\circ}C$ for 1 h was also investigated.

The evolution of texture and microstructure during continuous confined strip shearing (CCSS) in aluminum 3003 alloy sheets was investigated. The tools of CCSS based on the equal channel angular pressing (ECAP) were designed to provide a constant shear deformation of the order of 0.5 per pass while preserving the original sheet shape. FEM results indicated that the shear formation is not homogeneous throughout the sample thickness, in particular at the surface layers. A randomization of textures took place during the CCSS deformation. Observations by TEM and EBSD revealed the formation of sub-micrometer sized grains after CCSS.

TiN coated films show a good mechanical properties, high thermal properties and wear, erosion and corrosion resistance and are widely used as a coating materials in tools, ornaments, parts and semiconductors. In spite of these good properties, the fracture of TiN coated films occur during use. The fracture of TiN thin films is related to their microstructure. Especially, the life of TiN coated layer is related to the texture of the TiN films. One researcher suggested that the corrosion and erosion resistance of the TiN thin films is related to a uniform and dense structure of films. In this study, we studied the relationships between textures and friction coefficient, erosion and corrosion in TiN coated films. The flatness of (115) texture surface of TiN thin films is flatter than that of (111) texture surface. The friction coefficient of (115) texture surface of TiN thin films is similar with that of (111) texture surface. The wear resistance of (115) texture surface of TiN thin films is better than that of (111) texture surface. The erosion and corrosion resistance of (115) texture surface of TiN thin films is better than that of (111) torture surface. As well as texture, the wear, erosion and corrosion of TiN thin films has to consider defects such as pinholes, cracks, surface roughness and open columnar structure. The life of TiN coated products is influenced by the properties of wear, erosion, and corrosion resistance of TiN thin films and is related to texture of TiN coated films, density of pinholes and cracks, density of structure, and surface flatness.

Sheets of aluminum alloy 1100 were asymmetrically cold rolled in a rolling mill with different roll speeds. In order to promote the shear deformation during asymmetrical rolling, cold rolling without lubrication was performed. The evolution of texture components during asymmetrical rolling was investigated by the calculation of the orientation distribution function (ODF) using the monoclinic sample symmetry. The strain state during asymmetrical rolling was tackled by means of FEM calculations. Asymmetrical rolling gave rise to the development of pronounced strain gradients throughout the thickness layers which resulted in the formation of strong texture gradients in the aluminum sheet.

Nanoindentation is simply an indentation test in which the length scale of the penetration is measured in nanometres rather than microns or millimetres, the latter being common in conventional hardness tests. Three-dimensional molecular dynamics simulations have been conducted to evaluate the nanoindentation test. Molecular dynamics simulations were carried out on single crystal copper by varying crystal orientations to investigate nano-behavior of material beneath an indenter in nanoindentation. Morse potential function was used as an interatomic force between indenter and thin film. The result of the simulation shows that crystal orientation significantly influenced the slip system, dislocation nucleation and dislocation behavior.

In this study, to achieve the optimal conditions for mechanical hyper-fine pattern fabrication process, deformation behavior of the materials during indentation was studied with numerical method by ABAQUS S/W. Brittle materials (Si, Pyrex glass) were used as specimens, and forming conditions to reduce the elastic restoration and pile-up was proposed. The indenter was modeled a rigid surface. Minimum mesh sizes of specimens are 1-10nm Comparison between the experimental data and numerical result demonstrated that the finite element approach is capable of reproducing the loading-unloading behavior of a nanoindentation test. The result of the investigation will be applied to the fabrication of the hyper-fine pattern.

Finite element analysis model is suggested for analysis of milli-forming process, which forms milli-size products. Since the size of workpiece in a milli-forming process ranges from a few hundred micrometers to a few millimeters, microstructural changes such as the growth of micro-voids and the development of preferred orientation in a grain become crucial factors for the success of milli-forming. This analysis model incorporates anisotropy from deformation torture and deterioration of mechanical properties due to the growth of micro-voids. Applications of the proposed modeling to milli-forming are given and the results are carefully examined to understand the deformation characteristics such as texture development and damage evolution during extrusion/drawing of a milli-bar.

Electrolytic polishing is the anodic dissolution process in the transpassive state. It removes non-metallic inclusions and improves mechanical and corrosion resistance of stainless steel. Electrolytic polishing is normally used to remove a very thin layer of material from the surface of a metal object. An electrolyte of phosphoric, sulfuric and distilled water has been used in this study. In the low current density region, there can be found plateau region and material removal process and leveling process occur successively. In this study, an electrochemical polishing process using pulse current is adopted as a new electrochemical polishing process. In electrochemical machining processes, it has been found that pulse electrochemical processes provide an attractive alternative to the electrochemical processes using continuous current. Hence, this study will discuss the electrochemical polishing processes in low current density region and pulse electrochemical polishing.

The form-joining process (or clinching) uses a set of die and punch to impose the plastic deformation-induced geometric constraint on a sheet metal pair, But their joining strength ranges 50-70 percent of that of the resistance spot welding. In this paper, a new form-joining process with the aid of adhesive is proposed in which an epoxy adhesive is applied to a sheet metal pair, to improve joining strength. The strength and mechanical properties of the new process are discussed and compared for other joining processes.

Strain states of clad sheets consisted of AL3003 and SUS430 were studied by FEM simulation. Main simulation parameters include roll size, reduction, material properties, material temperature, and friction between roll and material (or friction between materials). To investigate the effect of friction on the evolution of strain states, the friction coefficient between roll and material (or fraction coefficients between materials) was varied. Components of strain rate, strain were compared according to the variation of friction coefficients. And strain states during cladding were compared with those induced by simple rolling process.

In this study, casting/forging process was used to produce an aluminum lower control arm for automobiles. Firstly, casting experiments were carried out to get an enhanced preform for forging the lower control arm. In the casting experiment, the effect of an additive, Sr, on the mechanical properties such as tensile strength and elongation and the microstructure of a cast preform were investigated. And a finite element analysis was peformed to determine an optimal configuration of the cast preform. Lastly, a forging experiment was carried out to make the final product of aluminum lower control arm by using the above cast preform. In the casting experiments, when 0.025% Sr was added into molten A356, the maximum values of tensile strength and elongation of the cast preform were obtained. In the forging experiment, It was confirmed that the optimal configuration of a cast preform predicted by FE analysis was very useful. The cast/forged product using designed preform was made without any defects.

Despite of outstanding optical performance of glass lens, glass lens have not been widely used because of poor productivity and high cost due to manufacturing process i.e. grinding, polishing. However, press-forming method of glass lens overcomes this disadvantage because of mass production. When glass lens is produced by press-forming method using closed die, it is needed that the volume of glass lens preform precisely measured in order to prevent incomplete products and to increase in life of die. The present paper shows the shortcoming of forming process with closed die, and performs FEM simulation of forming process with open die in order to overcome this shortcoming. The design parameter of open die is selected in standard of assembly with optical module and maintenance of optical performance. FEM simulation is carried out with selected parameter of open die and two basic preform. According to distribution of effective strain in glass lens, optical property of glass lens formed at each set of die and preform is compared.

The purpose of this study is to investigate the manufacturing technique on the U type Draw-Bending of inner groove tube. The U type tube requires the quality of product that satisfy sufficient conditions for a heat exchanger. The mandrel components act the important roles that prevent wrinkles and keep the shape of cross section of bended tube at bending process. We performed the FEM simulation using LS-DYNA software and the bending test of inner groove tube and then, compared bending simulation with bending test results about mandrel ball diameter, mandrel position and optimal clearance between mandrel and tube.

The automotive industry is currently trying to develop light- weight vehicle for both improvement of fuel efficiency and reduction of environmental pollution. For the reduction of vehicle weight, the substitution of aluminum for steel has been increased. However, the change of material causes a significant problem with respect to the method of joining. In this paper, strength of several aluminum joining methods such as spot welding, metal insert gas(MIG) welding, adhesive bonding was evaluated by performing lap test.

Surface normal vector and surface velocity are very important parameters to simulate rolling processes precisely. In this study, Local displacement functions are constructed for each node on the contact surface and parameters are found by the least square fitting of displacement on the neighbor nodes. Deformation gradient tensor is calculated from the displacement function and surface normal vector and velocity also can be derived. Flat rolling simulation model is presented on the basis of the suggested contact scheme. Series of rolling process simulation are carried out and the results are compared with the experiments.

For the purpose of rolling hard metals such as silicon steel and non-ferrous metals, the backup roll driven-type mill has been widely used in cold rolling industry. Since the backup roll drive results in horizontal bending of the work rolls and therefore exerted reciprocal action on the roll gap contour, the selection of slim work rolls is very restricted. In this paper, we present an analytic equation based scheme to determine a proper horizontal position of work roll minimizing the horizontal force subject to mechanical constraints.

Profile ring rolling process is simulated by using the general purpose commercial finite element analysis software MSC.Superform Because the deforming region is restricted to the vicinity of the roll gap, only a ring segment spanning the roll gap is analysed in order to save computation time and cost. A profile ring with an external round groove is chosen as an example to be analysed. The rolls with and without groove were analysed to compare the amount of side spread. It is found that the grooves in the rolls reduce the amount of side spread.

Generally RF AGC (Roll Force Automatic Gauge Control) controls the roll gap using the variation of rolling force caused by the roll eccentricity and the entry thickness of material, but RE AGC takes the bad effect of the roll eccentricity. The Feed-forward (FF) AGC method, which controls the next stand roll gap by the estimation of the thickness variation due to skid mark is needed to supplement the shortage of RF AGC. In this paper, an adaptive filtering method which takes account of the kind of material, the final objective thickness and the rolling speed is proposed to predict skid mark thickness variation. In addition, an improved estimation method of control point using a speedometer and looper angle is suggested. Via on line test, the performance improvement of the suggested FF AGC method is verified.

Run-Out-Table is the region between EDT and CT. Hot killed strip is cooled by air and water in ROT. In this procedure, phase transformation and shape deformation occur due to temperature drop. Because of un-ideal cooling condition, deformation of strip and non-uniform phase distribution come into existence. This phenomenon affects the strip property and lead th the existence of residual stress. And it exerts effects on the Coiling process, Coil Cooling process, and Un-coiling process. Through these process, the residual stresses of strip are more larger and unbalance of these stresses become more severe. Finite element (FE) based models for the analysises of non-steady state heat transfer and elastoplastic deformation are described in this investigation. The analysises of thermodynamics and phase transformation kinetics are suggested also. Using the ROT simulation result coiling process and coil cooling process simulations are carried out.

The mean temperature prediction of strip is very important in hot strip finishing mill because of affecting on product quality and shape. Also, temperature can be used by basic information in other on-line control models with affecting control accuracy in factory. So, FE based on-line temperature model was developed for predicting strip mean temperature accurately in various process conditions and factory environments. There are many variables in affecting strip mean temperature in on-line states of factory. But some problems are occurred in considering all variables for making temperature model because of the bad efficiency of regression or fitting analysis. In this report, we have adopted dimensional analysis for solving these problems. We have many variables with dimensions affecting strip temperature but we are able to make non-dimensional variables less than dimensional variables from the combination of dimensional variables caused by PI-Theorem in fluid mechanics. The developed models are divided by two parts. The one is interstand temperature prediction model. The other is roll gap temperature model.

In this research, on-line model for prediction of effective strain distribution hi strip on finishing mill process is prescribed. It has been developed using several selected non-dimensional parameters and previously made average effective strain model via series of finite element process simulations, $\Delta$$\varepsilon$ was introduced to describe the effective strain distribution in strip. To confirm adequate non-dimensional variables uniqueness test was done. And to decide the order of polynomial in on-line model equation tendency test for each variables was done. The prediction accuracy of the proposed model is examined through comparison with finite element calculation results.

The simulation program is developed to get the target strip crown of high strength steel in the continuous hot strip rolling. The developed program consists of several sub-program, which contains work roll shifting pattern, roll wear profile, roll thermal expanded profile and strip profile. Also, the variation of strip profile is investigated according to roll deflection and flattening. The results are compared with the values observed from the actual hot rolling of high strength steel. And effect of bender force on the strip profile is studied. The strip crown is shown to decrease with increasing bender force.

A crank throw, which is one of the part of crankshaft for a large diesel engine, is manufactured by both closed die forging and open die forging. For the improvement of productivity the open die forging method is usually adopted to manufacture it these days. In case of the open die forging for the crank throw, a preform shape is very important because it seriously affects final dimensions of the product. The purpose of this study is to investigate affective factors of the preform to obtain a good shape of final product through simulation and the results are compared to downsized lead experiments.

High temperature deformation and softening behavior of SAF 2507 super duplex stainless steel (SDSS) has been investigated in connection with an FEM analysis of hot forging process. Flow curves at various strain rates and temperatures were determined first from compression tests, and the kinetics of dynamic recrystallization were also formulated through the analysis of load relaxation test results. Applying the dynamic materials and proposed by Prasad et al., it was possible to determine the characteristics of deformation behavior effectively at a given condition of deformation. Constitutive relations and recrystallization kinetics formulated from the test results were then implemented in a commercial FEM code. Flow stress compensation formulated upon the volume fraction of recrystallization and adiabatic heating was found to improve significantly the FEA solutions in predicting the forming load and the distribution of recrystallized volume fraction after forging.

Idler of excavator are large product with diameter 500 - 600 mm and parts of a power transmit device. The object of the paper is developed large products by hot closed-die forging. The forging process which is proposed from numerical analysis and various tests is developed a large products with good quality. To estimate the design process parameters such as working load, temperature and flash thickness so on, numerical analysis are used by DEFORM 2D. To obtain a flow stress data and optimal forging temperature is carried out hot compression and tensile test at a various temperature range. Developed product is tested mechanical properties of elongation, hardness and tensile strength so on. Test results are presented excellent mechanical properties.

Cam mechanisms are one of the most popular devices for generating intermittent motion and are widely used in many areas. Also, as being interested in research of precision field, cam mechanism is required high accuracy and continuity, In. In this paper, the cam mechanism of filament automatic assembly machine design for precision motion is proposed. The modelling of a cam mechanism, cam profile functions, and the design of the cam considering the precision positioning of the cam mechanism is studied. And, simulation of designed cam mechanism had been carried out dynamic analysis.

A terminal pin, which is a part of high-voltage capacitors, has a head section of plate-shaped geometry with 0.8 thickness. The current manufacturing process, in which the head section is welded on the body part, has given wide deviations of part qualities such as geometrical accuracy, mechanical strength and electrical stability. In this paper, a cold forging process sequence was designed in order to produce the terminal pin as one piece. The plate-shaped head section requires an upsetting in the lateral direction of a cylindrical billet, which is followed by a blanking process. The deformed geometry of the upsetting, however, could not be predicted precisely by intuition since metal flows of an axial and a lateral direction of the cylindrical billet would occur simultaneously. Therefore, the geometry of the initial billet was determined by three dimensional finite element analysis in order to avoid defects in blanking process and intermediate forging processes were designed by applying design rules and two dimensional FE analysis. In addition, cold forging tryouts were conducted by using the die sets which were manufactured based on the designed process sequence.

Most important for meaningful forging simulation is the determination of correct process parameters. In addition a check and a compensation of the data base after the comparison between experiments and the computation of the developed process is necessary. The existence of a systematic process parameter data bank for special kinds of forming process in combination with forging specific simulation lifts the value of the products. Finite volume method is applied to simulate the hot forging process to investigate the defects for the automobile product. Three typical forging processes have been investigated; Extrusion by hydrolic press, Upsetting by crank press and Inclined upsetting by hammer press. Simulated result has compared with the experiment and provided a direction to improve the process.

In the open die forging process, it is difficult to optimize process parameters such as die shape, initial ingot size, feeding pitch, rotation angle and other process parameters in the operational environments. Therefore in this study, 3D finite element analysis has been performed to obtain optimal process condition for open die forging process. FEM analyses at various feeding pitches and rotation angles provide process conditions to make round bar having precise dimensional accuracy.

When hot strip is trimmed in the side trimming process at the entry side of tandem cold rolling mill, due to bad quality of trimming face and burr, product quality(saw ear)becomes so bad that it causes drop of yield and claim from customers. Therefore, it was examined that applying ultrasonic vibration is an effective method to improve quality of strip trimming face and decrease burr magnitude by decreasing shear force acting between strip trimming face and knife in side trimming process of cold rolling.

In the micro hole punching, the size and shape of burr and burnish zone are very important factors to evaluate quality of micro holes which depend on punch-die clearance, stain rate, workpiece material and etc. To get micro holes with small burr and wide burnish zone for industrial demands, not only the parametric study but also a study on fracture behavior in shear band are necessary. In this study, 100 $\mu\textrm{m}$, 25 $\mu\textrm{m}$ micro holes in diameter were fabricated on brass (Cu63/Zn37) and SUS 316 foils as aspect ratio 1:1, and the characteristics of micro holes was investigated comparing with man holes over several mm by scanning electron microscopic views and section views. Like macro hole, micro hole is also composed of 4 portions, rollover, burnish zone, fracture zone and it shows similar fracture behavior in shear band, but？ by high strain rate (10$^2$∼ 10$^3$s$\^$-1/) unlike macro hole fabrication and increment of relative grain size several different results are shown.

The spent fuel slitting device is an equipment developed in order to feed UO$_2$pellet to the dry pulverizing/mixing device. In this study, we have compared and analyzed the handling method of the slitting and that of the pellet and hull, processing time, separating time for 20kgHM, the number of blades, on the existing slitting device using in DUPIC, and spent fuel management technology research and test facility. Also, we have compared and analyzed about an advantage and weak point, designing and producing, processing, establishment, operation, maintenance about the vertical and horizontal slitting device. Based on these results, we have developed the vertical slitting device. By using the results, we have enhanced the slitting processing time(over 40%)in comparison with DUPIC device, and it will is effectively applied to available data for designing and producing of the hot test facility.

Finite element analyses for bursting failure prediction in bulge forming under combined internal pressure and independent axial feeding are carried out. By means of the FEM combined with Oyane's ductile fracture criterion based on Hills quadratic plastic potential, the forming limit and bursting pressure level are investigated for a seamed tube that comprises of weldment, heat affected zone(HAZ) and base material parts. Especially, in order to determine the material property of HAZ tensile tests for the base material and the weld metal are executed based on iso-strain approach. Finally, through a series of bulge forming simulations with consideration of the weldment and HAZ it is concluded that the proposed method would be able to predict the bursting pressure and fracture initiation site more realistically, so the approach can be extended to a wide range of practical bulge forming processes.

Recently social demands of fuel economy and environmental regulations require the development of light materials and new manufacturing technologies. In this point, the aluminum tube hydroforming process which is satisfied with good strength-to-weight ratio and recyclability is innovative concept. However the level of the aluminum tube hydroforming technology is low in comparison with that of steel tube hydroforming. In this paper, the hydroformability of aluminum tubes in different heat treatments is presented. Theoretical results for forming limits of the wrinkling and bursting are compared with experimental results of aluminum tubes.

In recent years, developments of light weight vehicle are one of the most important issues in automotive makers. New materials and new processes have been studied on the point of weight saving of chassis worldwide. Associated with materials, applications of high strength steel, aluminium, magnesium are being developed. On the point of new processes, tailored welded blank and hydroforming have been applied. In this paper, focusing to both material and process, we have applied hydroforming process to the engine cradle. In addition to that, three kinds of high strength steel have been applied to the development of light weight material for hydroforming. All the studies have been carried by FEM.

The modified yield function of Gologanu-Leblond-Devaux in conjunction with the Barlat and Lian's yield criterion is studied to clarify the plastic deformation characteristic of voided anisotropic sheet metals. The void growth of an anisotropic sheet under biaxial tensile loading and damage effect of void growth on forming limits of sheet metals are investigated. Also, the shape parameter defining non-spherical(prolate ellipsoidal) voids with initially random orientations is introduced in M-K model. The predicted forming limits are compared with the published experimental data.

In this study, finite element analysis for multi-stage deep drawing process of rectangular configuration with extreme aspect ratio is carried out especially for the blank design. The analysis of rectangular deep drawing process with extreme aspect ratio is likewise very difficult with respect to the design process parameters including the intermediate die profile. In order to solve the difficulties, numerical approach using finite element method is performed in the present analysis and design. A series of experiments for multi-stage rectangular deep drawing process are conducted and the deformed configuration is investigated by comparing with the results of the finite element analysis. Additionally, to minimize amount of removal material after trimming process, finite element simulation is applied for the blank modification. The analysis incorporates brick elements for a rigid-plastic finite element method with an explicit time integration scheme using LS-DYNA3D.

In the present study, subframe was developed using hydroforming technology. The manufacturing process for subframe consists of tube bending, pre-forming and hydroforming. The effects of bending process for manufacturing hydroformed subframe were researched. And the variables of bending process were studied by FEM simulation. The bending method is rotary draw bending that is the most popular, cost-effective bending method for thin walled tubes.

This paper is concerned with a forming analysis of front side members and the application of the forming effect in crash analysis of auto-body. Drawbead restraining forces are calculated with ABAQUS/Strandard in order to identify the boundary condition in forming process. Forming analysis with equivalent drawbead is carried out with LS-DYNA3D. In order to demonstrate the validity of the forming analysis, quantitative comparison of the thickness variation between the real product and the numerical simulation result is carried out. Forming histories obtained from the forming analysis are utilized as the initial condition of the crash analysis for accurate assessment of the crashworthiness.

The strain measurement of the panel in the sheet metal forming is essential work which provides experimental data needed to die design, process design, and product inspection. To measure efficiently the complex geometry strain, the 3-dimensional automative strain measurement system, which has high accuracy in theory, but has some 3∼5% errors in practice, is often used. The object of this study is to develop the error compensation technology to eliminate the strain, errors resulted when formed panels are measured using an automated strain measurement system. To achieve the study object, the position error calibration method correcting coordinates of the grid node recognized by a camera using error functions is suggested. Then the position errors were found by calculating the difference in the position of the cube node between real coordinates and measured coordinates in toms of node coordinates and the error calibration equations were derived by regressing the position errors. In order to show the validation of the suggested position error calibration method, finite element analysis and current calibration method was performed for the initial-blankformed.

The purpose of this study is preparing the database for conventional spinning of the steel sheets which are applied into the mechanical parts such as wheel disc and driving clutch drums. The experimental work for the conventional spinning of cylindrical typed shell has been carried out and the database for limiting spinning ratios, suing-back and thickness distributions has been obtained. The working conditions are categorized for the feeding velocity and dimension of rotating mandrel and forming roller. The results are useful to the product design of conical parts. And the present study can contribute to the improvement of industrial technology.

There is a strong industrial demands for the development of light-vehicle to improve fuel efficiency. It is more effective to reduce weight of the parts directly driven by an automobile engine. So the saving in weight of wheels which is operated by an automobile engine improve fuel efficiency more than other parts. There are many step of sheet metal forming in fabricating automotive wheel, so that it is difficult to design process and tools of multi-stage stamping. Traditionally, design process and tools have depended on the experience of skilled workers and it has done by trial and error methods. However, it needs too much costs and time. Taguchi methods has an advantage of the number of required experiments and reliability compared with trial and error method. In this study, Taguchi methods and response surface methods are applied to design process and tools of automotive wheel. As a result, the principal variables are selected and process conditions are optimized.

In recent years, design of an optimal blank shape is very important for sheet metal forming process in the automobile industry because the raw material cost rate is significant part in the automobile industry. With the design of an optimal blank shape, the engineer can protect a blank from an excessive holding force to improve the quality and reduce the ratio of material scrap. Therefore design of an optimal blank shape is inevitable in sheet metal forming process. However, if it causes a complicated shape of blank, it may be difficult to do the blank layout optimally. In this study, we developed software of optimal blank layout connected with the software of optimal blank shape design which was created in the past by the present authors. And by using these softwares, we would like to present the method in order to get optimal utilization ratio easily and precisely within short time for the sequence of works from design to blank layout.

Ball indentation tests have been used to estimate the mechanical properties of materials by some investigators. In this study, load-depth curves from ball indentation tests have been analysed using the geometric conditions of ball indentation. Series of numerical calculations and experimental results showed that those curves could be simplified by linear functions. After linearizing the indentation curves, the estimation process of the flow properties became straight forward and the scatter of results could be drastically reduced.

High temperature deformation behavior of a Ti-Al intermetallic compound has been investigated. Specimens with a near gamma and a lamella structures were obtained by performing heat treatment at 1200 and 1330$^{\circ}C$, respectively, for 24 hr and stabilized at 900$^{\circ}C$ for 4 hr followed by air cooling. A series of load relaxation tests has been conducted on these samples at temperatures ranging from 850 to 950$^{\circ}C$ to construct flow curves in the strain rate range from 10$\^$-6//s to 10$\^$-3//s. Strain hardening was observed even at the temperature of 950$^{\circ}C$ in both the near gamma and the lamella structures. Further aging treatment for 12 hr at test temperatures has found to cause no softening in both microstructures.

The interface heat transfer coefficient was measured for non-isothermal bulk forming of Ti-6Al-4V. FE analysis and experiments were conducted. Equipment consisting of AISI H13 die was instrumented with thermocouples located at sub-surface of the bottom die. Die temperature changes were investigated in related to the process variables such as reduction, lubricant and initial die temperature. The calibration approach based on heat conduction and FE analysis using an inverse algorithm were used to evaluate the interface heat transfer between graphite-lubricated die and glass-coated workpiece. The coefficients determined determined were affected mainly by the contact pressure. The validation of the coefficients was made by the comparison between experimental data and FE analysis results.

To reduce the storage space of spent fuels used at the atomic power plants all over the world, the uranium elements contained in the spent fuels is being extracted and effectively stored. For this, the spent fuel are oxidized and deoxidized. In this study, it is produced conceptual design specification about the spent fuel management technology research and test facilities have been produced. The first considered processes in the facilities is the metal conversion furnace in the dry environment. Since this process is operates at the high temperature range, we have to consider heat-resisting designs for the device. For the heat-resisting designs, we have surveyed and analyzed technical references for material properties. Also, we have determined the temperature distribution condition of the device based on experimental results. We have calculated thermal stress and strain of each devices by the commercial analysis software, I-DEAS. By using the results, we have analyzed design configurations of the point at issue by thermal effects, and suggested alternative design configurations. It is experimented for inspecting confidence rate of heat strain. Based on these results, necessary design specifications for heat-resisting design have been produced.

Non-heat treated steels are attractive in the steel-wire industry since the spheroidization and quenching-tempering treatment are not involved during the processing. In this study, three different steels such as dual phase steel, low-Si steel, and ultra low carbon bainitic steel were used to investigate their deformation resistance and forming limit. Deformation resistance was estimated by calculating the deformation energy and the forming limit was evaluated by measuring the critical strain revealing crack initiation at the notch tip of the specimens. The results showed that deformation resistance was the lowest in the low-Si steel, and the forming limit strain was the highest in the ultra low carbon bainitic steel.

Superconduction materials possess electrical/electronic and magnetic properties. Because superconduction materials is a ceramic powder, that can not be produced singlehandedly. So Ag sheathed Bi-2223 wire was produced by drawing process using powder-in-tube(PIT) method This superconductor has many difficulties to produce. The main difficulty is that the mechanical properties of the ceramic powder are very different from those of the Ag sheath. Actually, the fabrication of Ag sheathed Bi-2223 superconductor by PIT tends to lead to non-uniformity in the core thickness during drawing process. That is so called “Sausaging”. This study analyzed a sausaging using the finite-element method. Also, Effects of drawing process parameters on a sausaging has been carried out using finite element method. Finally, A way to prevent a sausaging has been discussed.

Recently, condenser tube which is used for a cooling system of automobiles is mainly manufactured by the conform extrusion but this method is inferior as compared with direct extrusion in productivity per the unit time and in the equipment investment. Therefore, it is essential for the conversion of direct extrusion with porthole die. The direct extrusion with porthole die can produce condenser tube which has the competitive power in costs and qualities compared with the existing conform extrusion. This study is designed to evaluate metal flow, welding pressure, extrusion load tendency of mandrel deflection that is affected by variation of porthole shape in porthole die. Estimation is carried out using finite element method under the non-steady state. Also this study was examined into the cause of mandrel fracture through investigating elastic deformation of mandrel during the extrusion.

For the analysis of leveling process by the 3-dimensional elastic-plastic finite element method, a finite element analysis program modeling large deformation of shell has been developed. This program fur analyzing large deformation of sheet during leveling includes spring-back analysis as well as efficient contact treatment between sheet and rolls of leveler. This is verified by the simple leveling experiment with 5 rolls at laboratory. Besides the leveling examples, problems within the category of large strain and rotation, such as 3-dimensional roll-up and gutter occurrence at continuous bending-unbending process are also tested for verification of the program. The residual curvatures of strip predicted by finite element analysis are within 20% error range of the experiment. The formation and direction of anticlastic curvature or gutter during bending-unbending under tension is predicted and this agrees with the experimental results.

This paper presents a new algorithm that can refine hexahedral elements while maintaining the appropriate connectivity. In the algorithm, at first the regions of mesh to be refined are defined and, then, the zero-thickness element layers inserted into the interfaces between the regions. All the meshes in the regions, in which the zero-thickness layers are inserted, are to be regularized in order to improve the shape of the slender elements on the interfaces. This algorithm is applied to the analysis of plastic deformation process. The results show that the refined mesh gives smaller relative errors than the original mesh.

In this paper, a viscoelastic structural analysis for the spent pressurized water reactor(PWR) nuclear fuel disposal canister is carried out to predict the collapse of the canister while the canister is stored in a deep repository for long time. There may exist some subterranean heat in a deep repository while the nuclear fuel disposal canister is stored for long time. Then, a time-dependent viscoelastic structural deformation may occur in the canister due to the subterrnean heat Hence, the viscoelastic stress variation according to time should be computed to predict the structural strength of the canister. A viscoelastic material model is adopted. Analysis results show that even though some subterrnean heat may exist for quite a long time, the canister structure still endures stresses below the yield strength of the canister. Hence, some subterranean heat cannot seriously affect the structural strength of the canister.

In the finite element simulation of hot forging processes using hexahedron, remeshing of a flash is very difficult. The mesh compression method is a remeshing technique to construct an effective hexahedral mesh. However, because mesh is distorted during the compression procedure or the mesh compression method, mesh smoothing is necessary to improve the mesh Qualify. in this study, several geometric mesh smoothing techniques and a matrix norm optimization technique are applied and compared which is more adaptive to the mesh compression method.

A finite element-based, integrated process model has been developed and applied to predict the detailed, three-dimensional aspects of the thermo-mechanical behavior occurring in the slab caster considering inclusion removal from molten steel by argon bubble flotation. Gas bubbles are simulated using the dispersion model calculating the volume fraction, and the bubble capture effect is included by a source term in the transport equation for particles. The process model is applied to the investigation of the effect of various process parameters on the inclusion removal in the molten steel.

This paper newly proposes a mesh regularization method for the enhancement of the efficiency in sheet metal forming analysis. The regularization method searches for distorted elements with appropriate searching criteria and constructs patches including the elements to be modified. Each patch is then extended to a three-dimensional surface in order to obtain the information of the continuous coordinates. In constructing the surface enclosing each patch, NURBS(Non-Uniform Rational B-Spline) surface is employed to describe a three-dimensional free surface. On the basis of the constructed surface, each node is properly arranged to form unit elements as close as to a square. The analysis results with the proposed method are compared to the results from the direct forming analysis without mesh regularization in order to confirm the validity of the method.

In order to construct the extrusion die surface of arbitrarily shaped sections, an automatic surface construction method based on NURBS surface and area mapping method is proposed in the present work. In the present study, a center point for area mapping is determined by introducing the marring concept based on constant area proportionality between original billet and final product. The characteristic points of inlet profile is determined using the traditional area mapping method and the root finding numerical method. The inlet and outlet profiles are precisely described with NURBS curves using the characteristic points of entry and exit sections. For the construction of NURBS surface, an interpolation method for the pre-determined two section curves has been developed to be used in the generation of interior control points and weights. To show the validity of the proposed method, automatic die surface generation is carried out for the several kinds of shaped sections.

The metal forming behavior and defect formation in Ti-6Al-4V tube during hot backward extrusion were investigated. To predict the forming-defects such as shear band, inner cracks or surface cracks, dynamic material model(DMM) including Ziegler's instability criterion and modified Cockcroft-Latham fracture criterion(C-L model) were used. These models were coupled to the internal variables generated from FE analysis. The chilling effect and friction indicated a great influence on the deformation mode of the tube and the formation of surface cracks. The simulation results for the backward extrusion were compared with the experimental observations.

Titanium alloys are a vital element for developing advanced structural components, especially in aerospace applications. However, process design for successful forming of titanium alloy is a difficult task, which is to be achieved within a very narrow range of process parameters. Presented in this paper is a finite element - based optimal design technique as applied to ductile fracture minimization process design in backward extrusion of titanium alloys.

Recently, micro forming process technology have been developed since the size of machine parts become the crucial factor for minimizing of products in general electronic products. Most small machine parts consist of gear and rotation axis and the wear by mechanical contact is known as the primary factor for life reduction of high precision machine part. Lots of studies for mechanical wear and friction have been reported and many researches of MEMS technology have been studied recently. But just few studies for wear of micro or milli sized machine part have teen implemented. In this research, the wear equation is suggested according to the contact shape of axial part in micro or milli sized machine part. And wear analysis model which can predict the magnitude of wear through this suggested equation with numerical analysis program.

The bending phenomenon has been known to be occurred by the different of velocity at the die exit. The difference of velocity at the die exit section can be obtained by the different velocity of billets through the multi-hole container and by the cohesion of billet inside the porthole die chamber. The bending phenomenon can be controlled by the different hole diameter. The experiments using aluminium material for the curved tube product had been done. The results of the experiment show that the curved tube product can be formed by the extru-bending process without the defects such as the distortion of section and the thickness change of the wall of tube and the folding and wrinkling. It is known that the welding and extruding of each billet has done simultaneously although the curved tube is extruded with four billets.

Shrinkage of injection molded parts is different form operational conditions of injection molding such as injection temperature, injection pressure and mold temperature, and mold design such as gate size. It is also various for different resins which have crystalline structure or not. In this study part shrinkage was investigated for various operational condition and resins; PBT for crystalline polymer, and PC and PMMA for amorphous polymer was used in experiment. Crystalline polymer shows higher part shrinkage by about three times than amorphous polymer. Part shrinkage increased as injection temperature and mold temperature increased and injection pressure decreased. Part shrinkage decreased as gate size increased since the pressure delivery is mush easier for large gate size. Part shrinkage according to the gate location was that the position in the part with close to the gate showed large shrinkage and this phenomenon might be occurred by residual stress.

The bending process for the "ㄱ" section product can be developed by the hot metal extrusion machine with the two punches moving in the different velocity. The bending phenomenon can be controlled by difference of velocity at the die exit section by the different velocity of billets through the two-hole container. The results of the experiment show that "ㄱ" section product can be bended by the extrusion process and that the curvature of the product can be controlled by the velocity of punch and that the defects such as the distortion of section and the thickness change of the product and the folding and wrinkling of the product did not happen after the bending processing by the extrusion bending machine.

In the present study, a new approach to predict the strength of sintered materials has been carried out and a new framework combining neck growth model and ideal pore model has been established based on the results of tensile tests on powder injection molded specimens with the various porosity. Powder injection molding (PIM) uses the shaping advantage of injection molding but is applicable to metals and ceramics. PIM delivers structural materials in a shaping technology previously restricted to polymers. 17-4 PH stainless steel powders with average diameters of 10 $\mu\textrm{m}$ were injection-molded into flat tensile specimens sintered at the various temperatures ranging from 900 to 1350$^{\circ}C$ for 1h. The relationships between strength and porosity were applied to the experimental results and verified.

The paper presents our study of development for multi-cavity preform mold system which consists of hot runner system and valve gate. For this purpose, stretching blow molding process and preform injection process were simulated by Polyflow and Moldflow. Based on various results of the preform injection process analysis, process planning was established. The sectional thickness distribution of preform was optimized. Preform injection mold system was designed by these technical analysis data. Finally, 24-cavity preform mold system was successfully developed.

The deterioration of dimensional accuracy, caused by springback, is one of problems to always occur in sheet metal forming processes. As the demand for lighter and stronger metals increases, the development of improved forming processes settling the springback problem becomes more important. In this work, springback phenomena are investigated which occur in the press forming process with the anisotropic sheet metal and axisymmetric tools. The improvement possibility of dimensional accuracies, mainly, flatness, will be examined by applying blank holding forces as a method of springback control.

A systematic investigation for the process design in deep drawing is necessary to improve the quality of drawn cups. This study concentrates mainly on the influence of process design strategy on the product quality. Several types of process design were chosen from initial blank of 100mm in diameter to make final cup of 50mm in diameter. Forming analysis are carried out to find out optimal design in terms of drawing force. We assume that the case which shows minimum drawing force in the subsequent operations is the best case. Through experiments it is found that the case which shows minimum drawing force also results in minimum drawing force and better product quality than other case. Thus, it is shown that this design strategy is very effective in the improvement of quality in drawn cups.

In this work, diamond turning process is used to produce mirror surface on a Al cone. The Al cone as used as a mirror which can reflect a laser beam without scattering and, hence, it is critical to minimize the surface roughness of a Al cone. During diamond turning, feedrate and tool nose radius are changed to investigate characteristics of the ultra precision machined surface of a Al cone. A laser beam of 633 nm is applied to examine the effect of surface roughness on the characteristics of reflectivity. It is found that surface roughness is not significantly affected by feedrate. The main factor influencing surface roughness is tool nose radius. The line patterns of reflected laser beams show that the minimum surface roughness of 0.08 $\mu\textrm{m}$ (Ra) is required to avoid scattering phenomena of reflectivity.

Currently tube hydroforming has many studies and applications in manufacturing industry, especially in automotive industry. But tube hydroforming was applied to the automotive component with simple shape. So the manufacturer and the researcher proposed additional processes to form the automotive component with complex shape. It is prebending and preforming. Prebending is to crush bend or rotary draw bend a tubular blank into a shape that facilitates placement into the next forming tool. Preforming is where the prebent tube is crushed into a shape that facilitates placement into the final forming tool. This paper analyzed and compared to the tube hydroforming process to using of general and preformed bending tube, also explained the importance of tube bending and preforming process. The explicit finite element program PAM-STAMP$\^$TM/ was used to simulate the tube hydroforming operations.

The dies & molds are a very economical production tool and a high value-added product because of its mass production capability compared to other production methods. Due to the very stiff international competitiveness, the industries meet many obstacles. At this moment, measured the status, the international trends and try to find the vision and strategy to promotion of the industry. In Korea, large portion of dies and molds are still low value-added and make large number of tools. In order to advance this industry to the high-tech area and gain competitiveness in the golbal marketplaces, effective means of resource investment and strategy should be properly provided.

Micro-suing that used on micro mechanism should be equal to distance between pitch and correct of shape. Therefore, micro spring must make by super-precision working. But, current step of super-precision processing depends on special quality of work piece and is ineffective the aspect of cost and productivity yet. Also, to use as demandable length shearing process perform but even if make precision spring, in the aspect of quality of coil spring make difficult that produce product of good quality. Therefore, purpose of this study presented proposed process that extract the point of processing factor after perform finite element analysis applying existing sheet shearing process to suing shearing process consider cost and productivity after evaluate.

Adiabatic shear bands have been observed in the serrated chip during high strain rate metal cutting process of medium carbon steel and titanium alloy. The recent microscopic observations have shown that dynamic recrystallization occurs in the narrow adiabatic shear bands. However the conventional flow stress models such as the Zerilli-Armstrong model and the Johnson-Cook model, in general, do not predict the occurrence of dynamic recrystallization (DRX) in the shear bands and the thermal softening effects accompanied by DRX. In the present study, a strain hardening and thermal softening model is proposed to predict the adiabatic shear localized chip formation. The finite element analysis (FEA) with this proposed flow stress model shows that the temperature of the shear band during cutting process rises above 0.5T$\sub$m/. The simulation shows that temperature rises to initiate dynamic recrystallization, dynamic recrystallization lowers the flow stress, and that adiabatic shear localized band and the serrated chip are formed. FEA is also used to predict and compare chip formations of two flow stress models in orthogonal metal cutting with AISI 1045. The predictions of the FEA agreed well with the experimental measurements.

The shearing process for the sheet metal is normally used in the precision elements such as semi-conductor components. In these precision elements, the burr formation brings a bad effect on the system assembly and demands the additional de-burring process. In this paper, we have developed the desktop-type precision punching system to investigate the burr formation mechanism and present kinematically Punch-die auto aligning methodology, for the purpose of burr unifomizing and minimizing, between the rectangular shaped punch and die. By using the scanning electron microscope, the aligned punching results are compared with the miss-aligned ones. Also, we measured the relative burr heights using the self-designed laser measuring device for insitu self aligning. Since it is hard to get the perfect, so called, burr-free edges during the shearing process, we introduced the ultrasonic do-burring machine. The de-burring operation was carried out by a novel do-burring method, the reversal flow resistance method, under different machining loads and abrasive types. The final do-burring results show the validity of our punching do-burring system pursuing the burr-free punched elements.

This study presents a new computational model to analyze the grain deformation in a polycrystalline aggregate in a discrete manner and based directly in the underlying physical micro-mechanisms. As a result, specific characteristics have to be considered for the numerical analysis. The grains and grain boundary elements are introduced to model individual grains and grain boundary facets, respectively, to consider the size effects in the micro forming. The constitutive description of the grain elements accounts for the rigid-plastic and the grain boundary elements for elastic relationships. The capability of the proposed approach is demonstrated through application of grain element and grain boundary element in the micro forming.

The BEM (Boundary Element Method) is a computational technique for the approximate solution of problems in continuum mechanics. In the BEM both volume and surface integrals transformed into boundary integral equations. So, we applied the ECM (Electrochemical Machining) process to boundary problem, because our focus is only deformed shape. The ECM process is modeled as a two-dimensional problem assuming constant properties of electrolyte, and an incremental formulation is used with automatic mesh regeneration. As a result the final shape is roughly agreed with experimental shape. But, it has an error of exact shape, because a chemically factor is not considered

This study describes a new maskless nano-fabrication technique of Si (100) using the combination of nanometer-scale mechanical forming by nano-indenter XP and KOH wet etching. First the surface of a Si (100) specimen was machined by using the nano-machining system, which utilizes the mechanism of the nano-indenter XP. Next, the specimen was etched by KOH solution. After the etching process, the convex structure or deeper hole is made because of masking or promotion effect of the affected layer generated by nano-machining. On the basis of this interesting fact, some sample structures were fabricated.

As a fundamental study on developing elements with micro shape, micro mold parts machining and experiment of injection molding using it were performed. The ultra precision micro machining system with high functionality was fabricated, and utilized in the machining of micro parts. By using this machining system and micro end-mill tool, a micro circle column structure of high aspect ratio, diameter 60 $\mu\textrm{m}$, height 500 $\mu\textrm{m}$, was fabricated. And a micro lens molds were fabricated by using ball end-mill tool of 300 $\mu\textrm{m}$ diameter and diamond fly-cut tool of 150 $\mu\textrm{m}$ radius. A micro injection molding machine, which is clamping force 1.75 ton, injection capacity 2.8cc, was fabricated for injection molding experiment using micro molds. The injection molding experiment was performed by using the injection molding machine, micro cylinder structures and lens molds. This paper introduces these micro machining system and injection molding machine and demonstrates examples of injection molding using fabricated molds.

A new control volume finite element method is proposed for three dimensional analysis of polymer flow. Tetrahedral finite element is employed and co-located interpolation procedure for pressure and velocity is implemented. Inclusion of pressure gradient term in the velocity shape functions prevents the checkerboard pressure field from being developed. Vectorial nature of pressure gradient is considered in the velocity shape function so that velocity profile in the limit of very small Reynolds number becomes physically meaningful. The proposed method was verified through three dimensional simulation of pipe flow problem for Newtonian and power-law fluid. Calculated pressure and velocity field showed an excellent agreement with analytic solutions for pressure and velocity. Driven-cavity problem, which is reported to yield checkerboard pressure filed when conventional finite element method is applied, could be solved without yielding checkerboard pressure field when the proposed control volume finite element method was applied. The proposed method could be successfully applied to the three dimensional mold filling problem.

Microlens arrays were fabricated using a novel fabrication technology based on the exposure of a PMMA (Polymethylmethacrylate) sheet to deep X-rays and subsequent thermal treatment. X-ray irradiation causes the decrease of molecular weight of PMMA, which in turn decreases the glass transition temperature and consequently causes a net volume increase during the thermal cycle resulting in a swollen microlens. A new physical modeling and analyses for microlens formation were presented according to experimental procedure. A simple analysis based on the new model is found to be capable of predicting the shapes of microlens which depend on the thermal treatment. For the replication of microlens arrays having various diameters with different foci on the same surface, the hot embossing and the microinjection molding processes has been successfully utilized with a mold insert that is fabricated by Ni-electroplating based on a PMMA microstructure of microlenses. Fabricated microlenses showed good surface roughness with the order of 1 nm.

Extensive studies have been conducted for reducing the residual stresses and birefringence in injection-molded optical disk substrate. Flow-induced and thermally-induced stresses and birefringence have been found as two main sources during injection molding process. However, high speed rotation also induces extra stresses and birefringence in real operation of disk drives. In the present paper rotation-induced in-plane birefringence has been measured and presented for CD and DVD substrates at different radial position. About 10 - 15 nm of extra retardation has been measured up to 4,800 rpm.

The wavelike flow mark phenomenon is one of the surface defects that can arise during the injection stage of the injection molding process. We have performed a numerical analysis using a finite element method for the injection molding to verify the validity of “Go-over” hypothesis. Also, we have compared the results of numerical analysis with available experimental data. Numerical analysis results of the flow marks are qualitatively in good agreement with experimental data of reference, but are quantitatively deviated from experimental data in a consistent manner. A parametric study has been performed to examine the correlative effects of various injection molding processing parameters and material properties on the flow mark size.

In this study, we fabricated the master metallic nano-stamper with nano pillar patterns to apply replication processes which is adequate for mass production. Master nano patterns with various hole diameters between 300 nm and 1000 nm was fabricated by e-beam lithography. After the seed layer was deposited on the master nano patterns using e-beam evaporation, the nickel was electroformed. In each step, the shape and surface roughness of their patterns were analyzed using SEM and AFM.