• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.62-63
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• 2005

Recently, a tiny piezoelectric linear motor using a vibration made of the transducer has been invented. The motor consists of a shaft, mobile element, and piezoelectric transducer using a piezoelectric radial mode bimorph disk. The fringe of the bimorph disk is fixed firmly which means this area has no degree of freedom. Therefore, the radial mode of the tranducer transfers to the flexurd mode. The mobile elements move along the shaft by the impact force generated by the flexurd mode of the piezoelectric transducer. The piezoelectric ceramic disks have thickness of 0.1 mm and diameter of 3.5 mm. The elastic disk is introduced between two disks of the ceramic, which has thickness of 0.1 mm and diameter of 3.8 mm. The fringe of the elastic disk is fixed by a brass cylinder which height is 1.2 mm. The Pyrex shaft is used which has diameter of 1 mm and height of 10 mm. The motors are operated at their resonant frequencies. The dynamic properties of the motor have been intensively measured and analyzed according to the applied voltage wave forms at the resonant frequencies. As the sawtooth and rectangular voltage waves are applied, the velocity, the thrust force, and the velocity dependence of the mobile position are measured. The dynamic characteristics are also analyzed within a period of each wave using laser vibrometer. The velocity of the mobile is moderately constant along the shaft. The better dynamic characteristics are obtained in the case of applying the rectangular wave.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.2
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• pp.63-67
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• 2018

Recent mold industry uses many roll-to-roll processes that can produce high production speed and precision machining and automation process. In the circular cylinder mold, however, patterns of less than $10{\mu}m$ are difficult to manufacture and maintain. In this study, we fabricated a circular cylindrical mold with a DLC thin film which have high hardness, low coefficient of friction and high releasability by using lithography and lift-off process. The height, line width, and pitch of the fabricated DLC macro pattern are $3.1{\mu}m$, $9.1{\mu}m$ and $20.2{\mu}m$, respectively. The pattern size is finer than the current applied to the aluminum cylinder type, and this shows the possibility of practical use of DLC micro pattern roll mold.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.229-234
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• 2005

Following the recent trend in the automotive manufacturing technologies, the product design subject to the die casting becomes more and more complex. The requirement of the die design becomes more demanding than ever before. In some cases the product's shape can have multiple slender manifolds. In such cases, design of the inlet and outlet parts of the die is very important in the whole manufacturing process. The main issues required for the qualified products are to attain gentle and uniform flow of the molten liquid within the passages of the die. To satisfy such issues, the inlet cylinder ('bed cylinder' in this paper) must be as large as possible and simultaneously the outlet opening at the end of each passage must be as small as possible. However these in turn obviously bring additional manufacturing costs caused by re-melting of the bed cylinder and increased power due to the small outlet-openings. The purpose of this paper is to develop effective simulation methods of calculation for fluid flows in multiple columns, which mimic the actual complex design, and to get some useful information which can give some contributions to the die-casting industry. We have used a commercial code CFX in the numerical simulation. The primary parameter involved is the size of the air-vent. We will show how the very small opening of the outlet, i.e. the air-vent, can be treated with the aid of the porous model provided in the code. To check the validity of the numerical results we have also conducted a simple experiment by using water.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.4
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• pp.290-298
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• 2016

This study aims to reduce the force exerted to the buoy of the gillnet by wave and current. Five buoy models were selected for experiments and their rope tensions under wave and current action were compared. Five models were EL (ellipsoid), EL-H (ellipsoid-hole), SL (streamlined body), SP (sphere) and CL (cylinder, traditional type). In the first experiment, the Five models were tested without any attachment. In the second experiment, a flagpole was attached to each model. As a result, in the condition without flagpole, the tensions of four models with the exception of the CL were about a half of that of the CL. In the condition with flagpole, the tension of all models was twice larger than that without flagpole. Thus, a new model was suggested to improve the problem, which has a combined body that of a flagpole and a buoy Three new models of CL-L (long and thin cylinder), LF (leaf shape) and LF-F (leaf shape with fin) were designed. Also a cylinder type (CLD) with a flagpole as a control was included in the experiment. As a result, the LF-F had the smallest tension and a half tension of the CLD. Therefore, it is supposed that the flagpole and buoy combined model could reduce the tension on buoy rope and contribute to improve the gillnet loss problem.

• Journal of Power System Engineering
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• v.21 no.5
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• pp.55-62
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• 2017

In this study, the water content and the low calorific value of the dried sludge are analyzed by using a vertical cylinder type indirect heating type dryer for evaluatation of energy source value. The vertical cylindrical thin film dryer was an Okadora Pilot Plant, and the dryer was indirect heating vertical thin film type. The internal standard consisted of 500 mm in diameter and 700 mm in height. In the drying experiment, 10 kg of dehydrated sewage sludge was added to the dryer and the total amount of the sludge was adjusted to 27 times by variable of the time, the number of revolutions and the steam temperature. The results of analysis of the 27th experiment component of the dried product showed that the average low calorific value of about 11.2 MJ/kg and the water content of 6%. This is satisfy the fuel use standard of the thermal power plant of the sludge.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.252-257
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• 2011

Magnesium thin films for marine engine parts such as the engine block and the cylinder head cover etc. were prepared on the magnesium alloy(AZ91D) substrate by Thermo-electron activated Ion-plating method. The influence of gas pressure and substrate bias voltages on the crystal orientation and morphology of the films was investigated with X-ray diffraction and field emission scanning electron microscope(FE-SEM), respectively. Moreover, the effect of crystal orientation and morphology of the magnesium films on the its hardness property was investigated as well. From the results, the hardness of the films was increased in Ar gas pressure due to the grain boundary strengthening and occlusion effects.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.87-94
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• 2006

An experimental research program providing knowledge to measure two-dimensional skin friction variation over a certain region of model surface is presented. In the oil-fringe imaging skin friction(FISF) technique, local slope of a thin oil applied on a test surface is measured from the interference fringe patterns on the oil surface, and its information is then related to the applied shear over the oil by the thin-oil lubrication theory. The FISF technique has been applied for a separation flowfield ahead of a circular cylinder vertically mounted on a flat plate, and it has been found that the FISF skin friction results show good comparison with the other numerical/experimental data obtained for similar conditions. implying an applicability of the technique.

• Structural Engineering and Mechanics
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• v.58 no.4
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• pp.731-743
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• 2016

Plastic behaviors, based on the von Mises yield criterion, of circular discs containing a purely elastic, circular inclusion under uniform temperature loading are studied with the finite element analysis. Temperature-dependent mechanical properties are considered for the matrix material only. In addition to analyzing the plane stress and plane strain disc, a 3D thin disc and cylinder are also analyzed to compare the plane problems. We determined the elastic irreversible temperature and global plastic collapse temperature by the finite element calculations for the plane and 3D problem. In addition to the global plastic collapse, for the elastically hard case, the plane stress problem and 3D thin disc may exhibit a local plastic collapse, i.e. significant pile up along the thickness direction, near the inclusion-matrix interface. The pileup cannot be correctly modeled by the plane stress analysis. Furthermore, due to numerical difficulties originated from large deformation, only the lower bound of global plastic collapse temperature of the plane stress problem can be identified. Without considerations of temperature-dependent mechanical properties, the von Mises stress in the matrix would be largely overestimated.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.4
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• pp.216-223
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• 2003

In the production of internal combustion engines, there have been trends to develop the high performance engines with improved fuel efficiency, lighter weights and smaller sizes. This trends help to answer problems related to thermal load and abnormal combustion, etc. in these engines. In order to investigate these problems, a thin film-type probe and its manufacturing method for instantaneously measuring surface-temperatures have been proposed in this study, Instantaneous surface temperature of a constant volume combustion chamber was measured by this probe and heat flux was obtained by Fourier analysis. In order to thoroughly understand the characteristics of combustion, the authors measured the wall temperature of the combustion chamber and computed heat flux through a cylinder wall while varying the protrusion height of the probe have been measured. To achieve the above goals, a instantaneous temperature probe was developed, thereby making possible the analysis of the instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

• Steel and Composite Structures
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• v.32 no.2
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• pp.199-212
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• 2019

This paper presents an investigation on seismic behavior of out-of-code Q690 circular high-strength concrete-filled thin-walled steel tubular (HCFTST) columns made up of high-strength (HS) steel tubes (yield strength $f_y{\geq}690MPa$). Eight Q690 circular HCFTST columns with various diameter-to-thickness (D/t) ratios, concrete cylinder compressive strengths ($f_c$) and axial compression ratios (n) were tested under the constant axial loading and reversed cyclic lateral loading. The obtained lateral load-displacement hysteretic curves, energy dissipation, skeleton curves and ductility, and stiffness degradation were analyzed in detail to reflect the influences of tested parameters. Subsequently, a simplified shear strength model was derived and validated by the test results. Finally, a finite element analysis (FEA) model incorporating a stress triaxiality dependent fracture criterion was established to simulate the seismic behavior. The systematic investigation indicates the following: compared to the D/t ratio and axial compression ratio, improving the concrete compressive strength (e.g., the HS thin-walled steel tube filled with HS concrete) had a slight influence on the ductility but an obvious enhancement of energy dissipation and peak load; the simplified shear strength model based on truss mechanism accurately predicted the shear-resisting capacity; and the established FEA model incorporating steel fracture criterion simulated well the seismic behavior (e.g., hysteretic curve, local buckling and fracture), which can be applied to the seismic analysis and design of Q690 circular HCFTST columns.