• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.238-241
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• 2007

A roller straightening process is a metal forming technique to improve the geometric quality of products such as straightness and flatness. The geometrical quality can be enhanced by eliminating unnecessary deformations produced during upstream manufacturing processes and minimizing any detrimental internal stress during the roller straightening process. The quality of steel cords can be achieved by the roller straightening depends the process parameters. Such process parameters are the roll intermesh, the roll pitch, the diameter of rolls, the number of rolls and the applied tension. This paper is concerned with the design optimization of the roller straightening process for steel cords with the aid of elasto-plastic finite element analysis. Effects of the process parameters on the straightness of the steel cord are investigated by the finite element analysis. Based on the analysis results, the optimization of the roller straightening process is performed by the response surface method. The roller straightening process using optimum design parameters is carried out in order to confirm the quality of the final products.

• 대한치과기공학회지
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• 제35권1호
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• pp.57-64
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• 2013

Purpose: Waste parts of zirconia blocks and powders were remained after CAD/CAM process. In order to make these residual zirconia fit for practical use, zirconia single cores were produced by drain casting process. Methods: Remained zirconia blocks were reduced to powders with zirconia mortar, and screened with 180 mesh sieve. Zirconia slip was prepared from waste parts of zirconia by ball milling. Plaster molds for forming cores by slip casting were also prepared. Formed cores were removed from mold after partial drying. Dried cores were biscuit fired at $1,100^{\circ}C$ for 1hour. Biscuit fired cores were treated with tools to control the fitness and thickness. Finished cores were $2^{nd}$ fired at $1,500^{\circ}C$ for 1hour. Microstructure of cross section of core was observed by SEM. Results: When mill pot was filled with 100g of zirconia and alumina mixed powder, 300g of zirconia ball, and 180g of distilled water, the optimum slip for drain casting was obtained. Gypsum plaster for ceramic forming was more suitable then yellow stone plaster for casting process. SEM photograph showed the microstructure of fully dense with uniform grain size of zirconia and well dispersed alumina grains into the zirconia matrix. Conclusion: Zirconia single cores were produced by drain casting process. Drain casting is useful process to make these residual zirconia fit for practical use. Further study will be focused on the preparation of the bridge type cores by casting.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.87-90
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• 2008

Since fastener bolt for airplane require high specific strength and corrosion resistance, Ti-6Al-4V alloy is widely used. However, the Ti-6Al-4V bolt is generally manufactured by cutting and rolling because of their poor workability. The aim of present work is to develop hot forming technology for high strength Ti-6Al-4V. Various heat-treatments were applied to specimen in order to increase hot-workability and prevent galling with die Multiple forging were simulated with FE code to determine optimum process parameters including specimen temperature, strain rate, local strain, and thermal shrinkage. Forged samples were heat-treated again to increase their mechanical properties.

• 소성∙가공
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• 제21권7호
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• pp.453-458
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• 2012

The flange hub is a main component of an automotive steering system. Dimensional precision of the flange hub is very important for precise control of the steering force. Consequently, the process design for precision forming of a flange hub is required. The teeth of the flange hub are generally formed by bending. In this study, the formability of flange bending was investigated using FE simulations. For the optimum process conditions, the flange is bent by movement of an insert die, and the die angle and bending length are selected as $90^{\circ}$ and 4mm respectively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.498-501
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• 2001

Blanking is one of the most frequently used processes in sheet metal forming. In this paper, attention is paid to the blanking simulation of aluminium foil with $20{\mu}m$ thickness which is used an anode in lithium-ion polymer battery. In order to study the shearing mechanism for the metallic foil, finite element analysis with Crockroft and Latham fracture criterion was performed. The objective of the present work is to evolve a methodology to obtain the optimum punch-die clearance for a given aluminium foil by the simulation of the blanking process using a general purpose FEM code.

• Journal of the Optical Society of Korea
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• 제20권2호
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• pp.291-299
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• 2016

We have investigated the ultimate limits of nonuniform grating couplers (NGCs) for optimized fiber coupling to silicon waveguides, compared to uniform grating couplers (UGCs). Simple grating coupler schemes, which can be fabricated in etching steps of the conventional complementary metal-oxide semiconductor (CMOS) process on silicon-on-insulator (SOI) wafers without forming any additional overlay structure, have been simulated numerically and demonstrated experimentally. Optimum values of the grating period, fill factor, and groove number for ultimate coupling efficiency of the NGCs are determined from finite-difference time-domain (FDTD) simulation, and confirmed with experimentally demonstrated devices by comparison to those for the UGCs. Our simulated results indicate that maximum coupling efficiency of NGCs is possible when the minimum pattern size is below 50 nm, but the experimental value for the maximum coupling efficiency is limited by the attainable fabrication tolerance in a practical device process.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.151-154
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• 1998

Stainless steel sheets are widely used to produce electrical appliances. But there are various problems occured in forming stainless steel sheets such as scratch, local fracture, earing. So the productivity of electrical appliances made of stainless steel sheets is decreased. And it is very important to improve the formability of stainless steel sheets. In this study, rectangular cup drawing tests have been carried out to obtain optimum process parameters for improving the formablity of stainless steel sheets. In the tests, selected process parameters are materials of dies and punches, lubricating conditions, and blank holding force. From the test results, we suggest the appropriate conditions to be applicable to the actual manufacturing processes.

• 소성∙가공
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• 제23권4호
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• pp.244-249
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• 2014

The thixoforming process has been applied to forming of a joint node for the aluminum frame of a low speed electric vehicle. A joint node should connect three aluminum extruded chassis showing different profiles. The MHS(magnetohydrodynamic stirring) A357 billet was selected because homogeneous globular grains are necessary as the billet materials for thixoforming. A careful design of joint node has been performed by the considerations of structural demands and the simulation results for the thixoforming process using the MAGMAsoft. Optimum heating temperature for the A357 billet was between 580 and $585^{\circ}C$ corresponding to the semi-solid temperatures showing 20-30% of liquid fraction. An injection speed of around 100mm/s and preheating of die at temperatures of $200^{\circ}C$ were also necessary conditions to obtain reasonable thixoformed parts.

• 소성∙가공
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• 제18권3호
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• pp.251-255
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• 2009

Since fastener bolt for airplane require high specific strength and corrosion resistance, Ti-6Al-4V alloy is widely used. However, the Ti-6Al-4V bolt is generally manufactured by cutting and rolling because of their poor workability. The aim of present work is to develop hot forming technology for high strength Ti-6Al-4V. Various heat-treatments were applied to specimen in order to increase hot-workability and prevent galling with die. Multiple forging were simulated with FE code to determine optimum process parameters including specimen temperature, strain rate, local strain, and thermal shrinkage. Forged samples were heat-treated again to increase their mechanical properties.

• 소성∙가공
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• 제19권5호
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• pp.290-295
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• 2010

Shaving technology is one of the significant metal forming technologies which can make the smooth and fine sheared surface of products after shearing process. The sheared surface on the side wall of the cutting edge is very important because it functions as a basic surface for measuring the dimensions of product. Effective sheared surface after shaving can be influenced by several working variables such as shaving allowance, shaving clearance, type of material and profile of cutting edge. The influence of these variables on shaving characteristics was investigated in this study. A cut-off die to make the simplified gear-shaped products was manufactured. Three kinds of sheet metals (AL5052, SPCC and SAPH440) of 3mm thickness were firstly sheared and then shaved for four shaving allowances and three sharing clearances. It was shown through experiments that the optimum working condition to give the maximum effective sheared surface in shaving was found ; Shaving allowance is 0.2mm and Shaving clearance is 0.01mm.