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연성파단의 예측을 위한 거슨 항복함수의 개선에 관한 연구
고윤기(Y. K. Ko),허훈(H. Huh) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
This paper deals with the modification of Gurson’s yield function in order to predict the yield of material which undergoes void initiation and growth under plastic deformation. The accurate prediction of yield point of the material will be helpful to determine ductile fracture of the material. In order to achieve the purpose, the yields of the single voided materials with the various porosities of 1%, 3%, 5%, 10% are calculated by finite element analysis and compare with the Gurson’s yield function according to the porosities. And the yield function is modified through the correction of the prediction of the yield in pure shear state and the addition of mean stress effect to 2nd order porosity term of yield function. Finally, the yield of the multi-voided material with 8, 27, 64 voids of the identical porosity is used in order to verify the modified yield function.
철도 차량용 티어링 튜브의 충돌 에너지 흡수 능력 예측 기법
고윤기(Y. K. Ko),안광현(K. H. Ahn),허훈(H. Huh),최원목(W. M. Choi),정현승(H. S. Jung),권태수(T. S. Kwon) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.5
This paper deals with the numerical prediction of energy absorbing capacity of a tearing tube, which can absorb the crash energy through expanding and axial splitting process. It is important to consider the dynamic material behavior and fracture characteristics of tube material in order to simulate accurately the deformation behavior of tearing tube. Therefore, uniaxial tensile tests are performed in order to obtain the flow stress curve and fracture strain of tube material according to strain rate. Quasi-static tensile tests were carried out in the range of strain rate from 0.001/sec to 0.01/sec using the static tensile testing machine. Dynamic tensile tests were conducted at the strain rate ranged from 0.1/sec to 300/sec using the high speed material testing machine. These dynamic material properties are applied to finite element analysis through user material subroutine of ABAQUS/Explicit. Especially, ductile fracture criterion is applied in order to describe the fracture characteristics of tube material during axial splitting process. Dynamic tearing cases are simulated and the reliability of the numerical results is verified by comparing with the experimental result in dynamic tearing test. The simulated results predict accurately the onset of fracture in axial splitting process and the energy absorption capacity has a good agreement with experimental result.