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권기찬,박상훈,윤성기,Kwon, Kie-Chan,Park, Sang-Hoon,Youn, Sung-Kie 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11
The first-order least-squares meshfree method for linear elasticity is presented. The conventional and the compatibility-imposed least-squares formulations are studied on the convergence behavior of the solution and the robustness to integration error. Since the least-squares formulation is a type of mixed formulation and induces positive-definite system matrix, by using shape functions of same order for both primal and dual variables, higher rate of convergence is obtained for dual variables than Galerkin formulation. Numerical examples also show that the presented formulations do not exhibit any volumetric locking for the incompressible materials.
병렬 컴퓨터를 이용한 형상 압연공정 유한요소 해석의 분산병렬처리에 관한 연구
권기찬,윤성기,Gwon, Gi-Chan,Yun, Seong-Gi 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.5
Parallel Approaches using Cray T3E which is NIPP (Massively Parallel Processors) machine are presented for the efficient computation of the finite element analysis of 3-D shape rolling processes. D omain decomposition method coupled with parallel linear equation solver is used. Domain decomposition is applied for obtaining element tangent stifffiess matrices and residual vectors. Direct and iterative parallel algorithms are used for solving the linear equations. Direct algorithm is_parallel version of direct banded matrix solver. For iterative algorithms, the well-known preconditioned conjugate gradient solver with Jacobi preconditioner is also employed. Moreover a new effective iterative scheme with block inverse matrix preconditioner, which is named by present authors, is presented and its results are compared with the one using Jacobi preconditioner. PVM and MPI are used for message passing and synchronization between processors. The performance and efficiency of each algorithm is discussed and comparisons are made among different algorithms.
권기찬,윤성기,Gwon, Kie-Chan,Youn, Sung-Kie 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.12
A parallel approach using a network of engineering workstations is presented for the efficient computation in the elastoplastic analysis of strip rolling process. The domain decomposition method coupled with the frontal solver for elimination of internal degrees of freedom in each subdomain is used. PVM is used for message passing and synchronization between processors. A 2-D plane strain problem and the strip rolling process are analyzed to demonstrate the performance of the algorithm and factors that have a great effect on efficiency are discussed. In spite of much communication time on the network the result illustrates the advantages of this parallel algorithm over its corresponding sequential algorithm.
충격완충체의 효과를 고려할 수 있는 운반용기의 파열낙하시험 유한요소해석 방법
권기찬,서기석,유길성 한국방사성폐기물학회 2009 방사성폐기물학회지 Vol.7 No.1
방사성물질 운반용기는 가상 사고조건에서 구조적 건전성이 유지됨을 실험 및 수치해석을 통해 입증하여야 한다. 가상 사고조건에 포함되는 파열낙하 조건에 대한 기존 유한요소해석의 경우 충격완충체에서 재료의 파손이 발생하기 때문에 일반적으로 유한요소모델에서 이 부분을 무시하고 해석한다. 본 논문에서는 파열낙하 해석에서 충격완충체의 변형으로 인한 낙하에너지 흡수의 효과를 고려하기 위해 요소의 적분점에서 응력이나 변형율이 재료의 파손 기준치에 도달하면 그 요소를 제거하는 방법을 제안한다. 본 해석방법의 효용성을 보이기 위해 한국원자력연구원에서 설계중인 핫셀 운반용기에 대해 파열낙하 해석을 수행하였으며, 요소제거 기법의 적용을 통해 낙하 에너지의 80% 정도가 충격완충체에서 흡수되는 것으로 계산되었다. 본 해석방법은 시험조건에 비해 보수성을 가지는 평가방법이며, 기존의 해석방법과 비교해 파열낙하 조건을 보다 근사적으로 해석할 수 있는 방법이다. Transport package for radioactive material should be structurally safe under puncture drop condition and itssafety should be verified by test and numerical analysis. Most finite element analyses for puncture drop havebeen performed without modeling the impact limiter since failure is occurred in the materials of the impactlimiter. This paper presents a new modeling methodology, where an element is eroded in case that thematerial’s failure criteria are reached at the element’s integration point, to investigate the effect of the impactlimiter in the puncture process. The effectiveness of the proposed scheme is shown through the puncture dropanalysis of hotcell transport cask, which is under design in KAERI. The results show that about 80 percent of thetotal impact energy is absorbed due to the deformation of impact limiter. Using the present method thepuncture drop can be analyzed more accurately, but it would give conservative results compared to the actualtest condition.