Domain Decomposition using Substructuring Method and Parallel Comptation of the Rigid-Plastic Finite Element Analysis

In the present study, domain decomposition using the substructuring method is developed for the computational efficiency of the finite element analysis of metal forming processes. In order to avoid calculation of an inverse matrix during the substructuring procedure, the modified Cholesky decomposition method is implemented. As obtaining the data independence by the substructuring method, the program is easily parallelized using the Parallel Virtual Machine(PVM) library on a workstation cluster connected on networks. A numerical example for a simple upsetting is calculated and the speed-up ratio with respect to various domain decompositions and number of processors. Comparing the results, it is concluded that the improvement of performance is obtained through the proposed method

Improvement of stability and efficiency in two-dimensional rigid-plastic finite element method

학위논문(석사) - 한국과학기술원 : 정밀공학과, 1994.2, [ iv, 71 p. ]한국과학기술원 : 정밀공학과

영역분할에 의한 격자세분화기법을 사용한 3차원 압출공정의 유한요소해석

학위논문(박사) - 한국과학기술원 : 기계공학과, 1999.2, [ viii, 142 p. ]Extrusion is a forming process in which a billet is forced to flow through a profiled die. The traditional design procedure for extrusion has mainly depended on the experience and the knowledge of designers and the trial-and-error method, which spends much time and cost. In order to save such consumption, numerical analyses have been implemented to simulate the metal forming processes. The finite element method has been one of the most widely used numerical methods for simulation of various engineering problems including the extrusion process. The three-dimensional finite element analysis of extrusion processes, however, requires large computation time due to its nonlinear characteristics. It is more severe in the extrusion process with thin-walled sections, which needs large degree of freedom for the proper description. In the present study, mismatching refinement is developed with domain decomposition for economic computation of extrusion processes. Mismatching refinement is an efficient domain decomposition method with different mesh densities for several subdomains. The solution is obtained by iterative calculation between subdomains which have different mesh densities. For the convergence of the iterative calculation between subdomains with different mesh densities, various velocity alternating schemes have been proposed and compared. Improvement of convergence has been obtained through the proposed alternating scheme for the mismatching refinement with domain decomposition. Through several numerical examples of the extrusion processes, such as a rectangular section and an ``E``-section, the validity of the proposed method has been demonstrated. The effect of the outlet position has also been investigated through the analysis. The results have revealed that computational efficiency is highly increased, especially for the three-dimensional problems. As a numerical example for hollow section extrusion using a porthole die, an extrusion of a triply-connected ...한국과학기술원 : 기계공학과

3차원 강소성 유한요소해석을 사용한 전자 부품의 정밀단조공정 설계

In order to increase the productivity of electrical parts, manufacturing processes using progressive die have been widely used in the industry. If closed-die forging process may be included in the series of the forming process, however, there arise many problems in the die design, such as determination of blank size, feeding method and formability, etc. For the proper design of a process, a prediction of the process is requred to obtain many design parameters. In this work, three-dimensional rigid-plastic finite element analysis is carried out to simulate precision forging process. The forging process of STEM, a part of photo pick-up hologram device, is simulated with the two types of processes, open die forging and semi-closed die forging, respectively. Form the results of analyses, the forging processes can be predicted successfully, which enables to design appropriately the die and the process