In the three-dimensional finite element simulation of forging processes, the design of meshes in initial billets as well as in intermediate remeshing stages plays the most important role because of the fast mesh degeneracy. In the present work, a new systematic approach of three-dimensional remeshing, so called modular remeshing, is proposed for the finite element analysis of forging. In order to show the effectiveness of the method, various industrially useful but complicated forging processes such as forging of a spur gear, turbine blade, ball and 3-D backward extrusion are analyzed by using developed several basic modules by the general rigid-plastic finite element method. The computational results show that the computation can be effectively carried out using the proposed concept of modular remeshing and it can be extended to other more complicated forging proeesses.
An automatic renoding scheme is proposed as a new concept of weak remeshing for the finite element analysis of large deformation. In order to show the effectiveness of the scheme, three-dimensional backward extrusion process is simulated. Criteria for the renoding are automatically checked and the renoding scheme is carried out fully automatically. Experiments are carried out to check the validity of the proposed scheme for the three-dimensional case. Comparisons between the computed results and the experiments show that the proposed scheme can be effectively applied to metal forming processes of large deformation in connection with full remeshing.
A method to calculate the contact traction on the die-workpiece interface is proposed. A systematic method for the elastic finite element analysis of die deformation by using the information obtained from the finite element analysis of workpiece deformation is proposed. The proposed method can be applied to both the two-dimensional and three-dimensional analyses of die deformation independently of the friction modelling and the constitutive equations. A rigid-plastic finite element analysis of workpiece deformation is carried out for forging of a spur gear. The elastic deformation and stresses of the die for spur gear forging have been analyzed by considering a shrink ring and the results have been compared with the case without a shrink ring. It is shown that the elastic deformation of the die should be considered to obtain more precise gear products. It is recommended that a shrink ring for the die should be used to prevent yielding of the die and reduce the elastic deformation of the die. The proposed method can be applied to arbitrarily curved die geometries in three-dimensional metal forming problems.
3차원 단조의 유한요소해석에서 초기격자 설계 및 격자재구성 단계에서의 격자 설계는 격자의 빠른 퇴화(degeneracy) 때문에 중요하다. 본 연구에서는 3차원 단조해석을 위해 모듈 개념을 도입하여 단위체 격자재구성(modular remeshing) 기법을 제안하였다. 제안된 방법을 평치차단조, 터어빈 블레이드 단조, 볼단조 및 3차원 후방압출 공정에 적용하여 유용성을 입증하였으며, 해석에 필요한 여러가지 유용한 모듈들이 개발되었다.
국부적으로 심한변형을 하는 3차원 대변형 문제의 효율적인 유한요소 해석을 위해 자동 절점재구성(renoding) 기법을 제안하였다. 자동절점재구성 조건을 제안하여 격자재구성의 전과정이 자동적으로 수행되었다. 제안된 방법을 3차원 후방압출에 적용하고 기존의 결과 및 실험결과와 비교하였으며, 기존의 결과 보다 실제변형 양상이 매우 잘 예측되었다.
금형의 해석을 위해, 소재로 부터 얻어진 정보를 금형에 전달하여 주는 체계적인 방법을 제안하였다. 산업적으로 유용한 평치차 공정을 강소성 유한요소법으로 해석한 후, 평치차 금형에 발생되는 탄성변형 및 응력상태를 탄성 유한요소법으로 계산하였다. 금형의 탄성변형량 및 응력상태를 줄여주기위해 보강링이 고려되었으며, 보강링을 사용하지 않은 결과와 비교한 결과 정밀한 치차제작을 위해서는 보강링 사용이 필수적임을 입증하였다.
본 연구에서 제안된 해석방법들은 기하학적으로 복잡한 일반적인 3차원 공정에 효과적으로 적용되어 질 수 있다.
