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이민철(Min Cheol Lee),전만수(ManSoo Joun) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
In this paper, we apply a forging simulator to automatic simulation of a connecting-rod forging process and compare its results with others found in the literature. The process information comes from the distributed examples of DEFORM3D. The process is fully automatically simulated using the tetrahedral element capability of AFDEX3D, developed by the authors. Our results are compared with the results found from the related literature, already simulated using DEFORM3D by other researchers. The comparison shows that our results are relatively excellent especially in terms of mesh quality on which the solution accuracy depends mainly.
조성훈(Sunghoon Jo),정승원(Seungwon Jeong),전만수(Mansoo Joun) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.5
In this paper, a finite element approach to simulating a self-piercing riveting process is presented. The detailed formulation and numerical scheme are introduced. The material-material contact interface is formulated by a penalty method. A complicated self-piercing riveting process, which is not actual but only for the purpose of test of the approach, is simulated and the predictions are shown with emphasis on the variation of finite elements especially around the tip of the rivet of which shape is of great importance for solution accuracy.
이동형(Donghoung Lee),김봉수(Bongsu Kim),전만수(Mansoo Joun) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.5
In this paper, kinematic analysis of a general knuckle press is made for application to metal forming simulation. The predictions for and upsetting process with the knuckle press are compared with those obtained using averaged constant velocity for the same process in terms of the forming load as well as the deformed shape. The materials tested are rate-dependent and their dependencies ranging from 0.05 to 0.2 are examined to reveal the effect of die or tool velocities on the predictions of metal forming processes.
사면체요소와 육면체요소를 이용한 삼차원 단조 시뮬레이션 결과의 비교 및 검증
이민철(Min Cheol Lee),백종파(Jong Pa Baek),전만수(ManSoo Joun) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
In this paper, we simulate a rotor pole cold forging process by a forging simulator with both tetrahedral and hexahedral element capabilities and compare the predictions obtained by the two approaches with the experiments. Hexahedral element capability runs manually while tetrahedral element capability runs automatically with help of an intelligent remeshing technique. It is shown that the tetrahedral element capability can give quite accurate solution if assisted by the intelligent remeshing technique even though the tetrahedral element itself is not theoretically and numerically clear.
나노분말 분쇄 및 분산용 고성능 초경합금 볼의 제조를 위한 분말사출성형 공법
정성택(SeongTaek Chung),조주현(JuHyun Cho),이민철(MinCheol Lee),권영삼(YoungSam Kwon),전만수(ManSoo Joun) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
We present a powder injection molding technique of fabricating cemented tungsten carbide(WC) balls for milling and dispersing nano-powder in this paper. The conventional powder metallurgy approach is investigated to reveal its drawbacks of density non-homogeneity. New procedures of powder injection molding for the homogeneous high-precision WC balls, involving the binding process, powder injection molding process and sintering process, are presented in detail. Each process is investigated empirically and numerically to obtain its engineering information, which can used for process optimization.
최인수(Insu Choi),엄재근(Jaegun Eom),이민철(Mincheol Lee),전만수(Mansoo Joun) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Finite element approach to analyzing the tensile test is presented in this paper. The rigid-plastic finite element method is used. To predict the necking in the tensile test, a simple bar finite element model that is mechanically perfect is used. The Hollomon's constitutive law is employed for describing the stress-strain curve. The presented approach is applied to a ductile steel. It has been shown that the necking occurs exactly when the true strain of a specimen reaches the strain hardeningexponent of the material. The necking phenomena are investigated in detail from the analyzed results. The importance of exact prediction of the necking is emphasized for both program developers and their users.
유한요소망이 인장시험과 유한요소법을 이용한 진응력-진변형곡선 획득 기법에 미치는 영향에 관한 고찰
김홍태(HongTae Kim),엄재근(Jaegun Eom),최인수(InSu Choi),이민철(Mincheol Lee),전만수(ManSoo Joun) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
We present the numerical characteristics of a new true stress-strain curve acquisition method over a large range of strains by the tensile test and a finite element method through comparing the results obtained by various finite element mesh systems. The method is introduced in detail. The effects of the finite element mesh systems on the results are investigated to show its numerical characteristics of the new method. It is shown that the method is quite robust, implying that it can be used as a special function of the tensile test machines.
인장시험 결과로부터 고 변형률에서 진응력 - 진변형률 곡선의 획득 방법
엄재근(Jaegun Eom),지창운(Changwoon Gee),이민철(Mincheol Lee),문호근(Hokeun Moon),전만수(Mansoo Joun) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
A methodology of acquisition of true stress-strain curves over large strain by using the engineering stress-strain curves obtained by the tensile test is presented in this paper. The method employs the results of both the tensile test and its finite element analysis. A rigid-plastic finite element method is used to analyze the tensile test for providing the deformation information. The analysis is carried out with emphasis on prediction of the necking to obtain the reference true stress-strain curve, which is modified iteratively to minimize the difference in tensile force between the tensile test and its analyzed result. The validity of the approach is verified by comparing the tensile test result and its finite element solution obtained by the modified true stress-strain curve.
마찰에 민감한 긴 파이프의 축관 및 확관 동시공정의 해석을 통한 마찰법칙의 평가
최인수(InSu Choi),엄재근(JaeGun Eom),전병윤(ByungYoon Jun),이민철(MinCheol Lee),전만수(ManSoo Joun) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Frictional laws are criticized with emphasis on their application to bulk metal forming simulation in this paper. Coulomb frictional law and constant shear frictional law are investigated in detail in terms of their effect on metal forming process. A friction sensitive bulk metal forming process, a long-pipe simultaneously shrinking and expanding process, is introduced and the problems of the constant shear frictional law are revealed comparing the predictions obtained by the Coulomb frictional law and the constant shear frictional law with the experiments. It is shown that the constant shear frictional law is improper in the case that the normal stress varies very much from position to position and that the normal stress is low compared with flow stress of the adjacent material. It is also shown that the Coulomb frictional constant is more or less affected by the normal stress.