• Transactions of Materials Processing
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• v.1 no.2
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• pp.20-31
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• 1992

대형 강괴의 업셋팅 공정은 주조 조직의 방향성을 없애고, 코깅작업의 효율을 향상시키기 위한 충분한 단조비를 확보하기 위하여 필요한 공정이다. 공정에 영향을 주는 인자로써 상부 금형의 형상을 변화시켜 가면서 해석을 수행하였다. 극단적인 긴 파이프성 기공의 변형거동과 중심부에서 높이에 따른 원형기공의 닫힘거동 및 압하율과 기공폐쇄 정도를 관찰하였다. 충분한 단조비를 얻고 기공의 닫힘 및 압착을 이루기 위한 적절한 압셋팅 다이의 선택 및 업셋팅 공정을 예측하여 공정개선에 기여하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1877-1889
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• 1992

Upsetting is performed in open-die press forging to deform metal in all directions in order to enhance soundness of a product and reduce directionality of properties caused by casting. It is necessary to ensure sufficient forging ratio for subsequent cogging operations and consolidate the void along the centerline. To obtain these benefits, the upper die shape (dome and dished shape) is considered as an upsetting parameter. Thermo-viscoplastic finite element analysis has been carried out so as to understand the influence of upper die shape on the effective strain, hydrostatic stress and temperature in the upset-forged ingots without internal defects. The analysis is focused on the investigation into internal void closure in ingots with pipe holes and circular voids. The computational results have shown that the volume fraction of the void is independent of the circular void size and the closure of internal voids is much more influenced by the effective strain than the hydrostatic stress around the void. It is finally suggested that the height reduction must be over 35% for consolidation of internal voids.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.177-182
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• 2007

We simulated an electric upsetting process by the rigid-thermoviscoplastic finite element method. Several engineering assumptions were made to calculate the heat generation due to the electric resistance. The skin effect of the bar was taken into account for the heat generation. The approach was applied to simulate an artificial electric upsetting process for the exhaust valve of the ship engine.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.6
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• pp.152-158
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• 2011

An electric upsetting process by the rigid-thermoviscoplastic finite element method was simulated in this study. Several engineering assumptions were made to calculate the heat generation due to the electric resistance. The skin effect of the bar was taken into account for the heat generation. The approach was applied to simulate an artifical electric upsetting process for the exhaust valve of the ship engine.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.122-130
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• 1996

During the cold forming, due to high working pressure acting on the die surface, failure mechanics must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. Die wear affects the tolerances of formed parts, metal flow and costs of process etc. The only way to control these failures is to develop methods which allow prediction of die wear and costs of process etc. The only way to control these failures is to develop methods which allow prediction of die wear and which are suited to be used in the design state in order to optimize the process. In this paper, the wear experiments to abtain the wear coefficients and the upsetting processes was accomplished to observe the wear phenomenon during the cold forming process. The analysis of upsetting processes was accomplished to observe the wear phenomenon during the cold forming process. The analysis of upsetting processes was accomplished by the rigid-plastic finite element method. The result from the deformation analysis was used to analyse the die wear during the processes and the predicted die wear profiles were compared with the measured die wear profiles.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.82-85
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• 2000

In cold forging, the final product is usually given by multi-stage process and the preform with stepped shape can be manufactured through the various forging method. The forward extrusion and upsetting processes for preform with stepped shape have been analyzed by using the rigid-plastic finite element analysis code, InteFORM and compared for load and stroke according to ae reduction of weを An engineer should select the proper processes considering the capacity and the stroke of the corresponding press in the forging of the preform with stepped shape.

• Transactions of Materials Processing
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• v.32 no.4
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• pp.180-190
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• 2023

This study deals with residual stress prediction and hardness evaluation within cross ball grooved inner race fabricated by cold upsetting process consisted of upsetting and ejection steps. A raw workpiece material of AISI 5120H (SCr420H) is first spheroidized and annealed, then phosphophyllite coated to form solid lubricant layer on its outer surface. To investigate influences of the heat treatment, uni-axial compression tests and Vickers micro-hardness measurements are conducted. Three-dimensional elasto-plastic FE simulations on the upsetting step and the ejection one are performed to visualize the residual stress and the ductile (plastic deformation) damage. External feature of the fabricated inner race is fully captured by using an optical 3D scanner, and the micro-hardness is measured on internal cross-sections. Consequently, the dimensional compatibility between the simulated inner race and the fabricated one is ensured with a difference of under 0.243mm that satisfied permissible error range of ±0.50mm on the grooved surface, and the predicted residual stress is verified to have similar distribution tendency with the measured Vickers micro-hardness.