• 대한기계학회논문집A
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• 제29권2호
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• pp.325-332
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• 2005

This paper presents a study on defects in pearlite lamella structure of high carbon steel by means of finite-element method(FEM) simulation. High carbon pearlite steel wire is characterized by its nano-sized microstructure feature of alternation ferrite and cementite. FEM simulation was performed based on a suitable FE model describing the boundary conditions and the exact material behavior. Due to the lamella structure in high carbon pearlite steel wire, material plastic behavior was taken into account on deformation of ferrite and cementite. The effects of many important parameters(reduction in area, semi-die angle, lamella spacing, cementite thickness) on wire drawing process can be predicted by DEFORM-2D. It is possible to obtain the important basic data which can be guaranteed in the ductility of high carbon steel wire by using FEM simulation.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.205-209
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• 1998

Unlike the drawing of round section from round bar, the shaped drawing like polygonal section is known to have influence not only drawing stress but also comer filling. Therefore, this study analyze the drawing process of suqare rod from round bar using nonsteady state rigid-plastic FEM. To investigate effects of process variables of the drawing process of square rod from round bar, FE-simulations with variety of reduction in area and semi-die angle for a given frictional condition have been conduction. By this results, it has to suggest optimal process condition on the drawing stress and the comer filling. In addition, it has determined forming limit considering necking and bulging.

• 소성∙가공
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• 제8권2호
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• pp.160-168
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• 1999

This paper is concerned with the process sequence design of longneck flange forming by using cold extrusion with thick hollow pipe. The conventional hot forming process to produce a longneck flange is investigated by thermo-viscoplastic finite element method to observe the metal flow in detail and evaluate design requirements. Based on the results of simulation of the current hot forming process, design strategy for improving the process sequence are developed using the thick hollow pipe. The main goal is to obtain an appropriate improved process sequence which can produce the required product most economically without tensile cracking, workpiece buckling, and overloading of tools. Newly process condition such as semi-die angle, reductio ratio of cross-sectional area of axisymmetrical extrusion process. The final designed process can provide very useful guidelines to other flange forming industries.

• 소성∙가공
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• 제26권3호
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• pp.162-167
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• 2017

The tensile surface residual stress in the multi-pass drawn wire deteriorates the mechanical properties of the wire. Therefore, the evaluation of the residual stress is very important. Especially, the axial residual stress on the wire surface is the highest. Therefore, the objective of this study was to propose an axial surface residual stress prediction model of the multi-pass drawn steel wire. In order to achieve this objective, an elastoplastic finite element (FE) analysis was carried out to investigate the effect of semi-die angle and reduction ratio of the axial surface residual stress. By using the results of the FE analysis, a surface residual stress prediction model was proposed. In order to verify the effectiveness of the prediction model, the predicted residual stress was compared to that of a wire drawing experiment.

• 한국정밀공학회지
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• 제15권11호
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• pp.145-151
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• 1998

Unlike the drawing of round section from round bar, the shaped drawing like polygonal section is known to have influence not only drawing stress but also corner filling. Therefore. this study analyze the drawing process of suqare rod from round bar using nonsteady state rigid-plastic FEM. To investigate effects of process variables of the drawing process of square rod from round bar, FE-simulations with variety of reduction in area and semi-die angle for a given frictional condition have been conducted. By this results, it has to suggest optimal process condition on the drawing stress and the corner filling. In addition, it has determined forming limit considering necking and bulging.

• 소성∙가공
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• 제16권7호
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• pp.530-537
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• 2007

This paper is concerned with the analysis of plastic deformation of bimetal co-extrusion process. Two sets of material combination have been adopted for analysis, i.e. combinations of Cu/Al and Fe/Al. In the first set of material combination, the selected materials are AA 1100 aluminum alloy as hard material and CDA 110 as soft one. This type of material selection is to examine the effect of hard core and soft sleeve and vice versa on the deformation pattern in terms of plastic zone and velocity discontinuity along the contact surface between construction materials. Four different cases of co-extrusion process in terms of material combination and interference bonding were simulated to investigate the effect of material arrangement between core and sleeve, and of bonding on the plastic zones and velocity discontinuity. In the other set of material combination, model materials used as core and sleeve were AA 1100 and AISI 1010, which are relatively soft and hard, respectively. Process parameters except diameter ratio of core to sleeve material such as semi-die angle, reduction in area in global sense and die comer radius have been set constant throughout the simulation to concentrate our effort on the analysis of influence of diameter ratio on deformation behavior such as deformation zone, surface expansion, exit velocity discontinuity between composite materials, and extrusion forces.

• 소성∙가공
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• 제19권4호
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• pp.224-229
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• 2010

During the multi-pass wire drawing process, wires suffer a great amount of plastic deformation that is through the cross-section. This generates tensile residual stress at surface of drawn wires. The generated residual stress on surface is one of the problems for quality of wires so that prediction and reduction of residual stresses is important to avoid unexpected fracture. Therefore, in this study, the effect of process variables such as semi-die angle, bearing length and reduction ratio on the residual stress was evaluated through Finite Element Analysis. Based on the results of the Analysis, a prediction model was established for predicting residual stress on the surface of high carbon steel(AISI1072, AISI1082). To identify the effectiveness of the proposed model, X-ray diffraction is used to measure the residual stresses on the surface. As the result of the comparison between calculated residual stresses and measured residual stresses, the model could be used to predict residual stresses in cold drawn wire.

• 대한기계학회논문집
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• 제11권3호
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• pp.488-500
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• 1987

본 연구에서는 축대칭 봉재의 원주상에 기계가공된 인공릿지가 공구를 통하여 진행할 때의 변형모델을 제시하고 이를 상계해법으로 해석하여 표면소성 연마가공이 되기 위한 릿지의 물결모양운동과 이 운동이 일어나지 못하고 릿지가 편평해지면서 소 멸되고 또는 전단이 되는 경우들에 대한 판정조건 및 한계영역을 설정하였다. 순동 및 연강 그리고 알루미늄등을 시험재료로하여 이론적으로 예측된 릿지의 세 가지 운동 에 대해 실험을 통하여 검증하였으며 물결모양운동으로 인한 가공물의 표면조도 개선 정도를 시험전후에 최대높이 표면조도의 크기로 측정하여 비교하였다. 또한 릿지의 물결모양운동으로 인하여 가공물의 표층부에 형성된 가공변질층의 깊이를 이론적으로 예측하여 실험과 비교하였다.