• 대한조선학회논문집
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• 제33권1호
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• pp.90-97
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• 1996

최적의 유한요소분할은 모든요소의 해석오차가 허용수준이내에 들고 균일하도록 함을 의미한다. 이러한 유한요소분할은 구조해석을 효율적으로 수행하기 위하여 필요하다. 최적요소분할을 위해서는 오차추정과 그 결과를 고려하여 요소분할을 수행할 수 있는 순응형 요소생성기법이 요구된다. 이러한 과정의 유한요소해석은 초기의 해석결과의 정보로 부터 해석오차를 추정하고 순응형 유한요소를 생성하여 다음단계의 유한요소해석을 효율적으로 수행 가능하게 한다. 본 연구에서는 유한요소해석 오차추정과 이를 다음 단계의 유한요소해석에 적응하는 다단계 유한요소해석기법 개발을 위한 기초연구를 수행하였다. 본 연구의 순응형 유한요소분할에는 삼각형요소를 사용하였고 해석 후 오차추정에는 응력투영법을 사용하였다. 또한 오차추정, 요소분할과 유한요소해석을 효율적으로 수행하는 다단계기법의 알고리즘을 제안하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.225-229
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• 2008

We present an intelligent forging simulator AFDEX. The intelligent forging simulator is determined by the adaptive and optimal mesh generation technique and many intelligent application-oriented special functions which minimize the user-intervention during forging simulation. Of course, the solution accuracy should be optimized in the intelligent simulation. We have developed AFDEX to meet the requirement on intelligent simulation. Its characteristics are introduced with the help of typical application examples.

• 대한기계학회논문집A
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• 제24권7호
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• pp.1763-1770
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• 2000

A finite element interface system for the design of optimal spot welding locations has been developed. In order to find out the optimal locations of spot welding points, iterative finite element an alyses are necessary, and thus automatic generation of finite element model for the structures with spot welded pointsis required. In this interface system, quadrilateral shell elements are automatically generated for finite element analysis of spot welded structured, which employs a domain decomposition methodand adaptive mesh(h-method).

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.203-208
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• 2005

In this paper, an automated adaptive mesh generation scheme, based on an advancing-front-Delaunay method, is developed for finite element simulation of three dimensional bulk metal forming processes. During the simulation, the finite element mesh system is adaptively remeshed whenever the mesh is unacceptable. Several schemes are developed such as curvature compensation scheme to minimize volume loss, optimal smoothing scheme to improve element quality, etc. The presented approach is evaluated and applied to automatic forging simulation in order to demonstrate the effect of the developed schemes.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.538-543
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• 2007

A procedure is proposed to generate optimal grid with minimal user intervention while keeping a prescribed level of accuracy, using an adaptive X-FEM and applied to shape optimization. In spite of various advantages of X-FEM, however, there are several obstacles for practical applications. Because of using a uniform background mesh and additional degree of freedoms for enrichment, an X-FEM is usually computationally more expensive than traditional finite element method. Furthermore, there are often accuracy problems. For an automatic procedure of optimal mesh generation, an h-adaptive scheme and a posteriori error estimation obtained by a post-processing process are utilized. The procedure is shown by 2-D shape optimization examples.

• 대한기계학회논문집A
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• 제25권6호
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• pp.1004-1014
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• 2001

The fully automatic algorithm from initial finite element mesh generation to remeshing in two dimensional geometry is introduced using bubble packing method (BPM) for finite element analysis. BPM determines the node placement by force-balancing configuration of bubbles and the triangular meshes are made by Delaunay triangulation with advancing front concept. In BPM, we suggest two node-search algorithms and the adaptive/recursive bubble controls to search the optimal nodal position. To use the automatically generated mesh information in FEA, the new enhanced bandwidth minimization scheme with high efficiency in CPU time is developed. In the remeshing stage, the mesh refinement is incorporated by the control of bubble size using two parameters. And Superconvergent Patch Recovery (SPR) technique is used for error estimation. To verify the capability of this algorithm, we consider two elasticity problems, one is the bending problem of short cantilever beam and the tension problem of infinite plate with hole. The numerical results indicate that the algorithm by BPM is able to refine the mesh based on a posteriori error and control the mesh size easily by two parameters.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.288-295
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• 2003

An adaptive procedure in finite element analysis is presented by p-refinement of meshes in conjunction with a posteriori error estimator that is based on the recovery technique. In case of the recovery technique, the SPR(superconvergent patch recovery) approach has been modified for p-adaptive mesh refinement. The strategy of finding a nearly optimal distribution of polynomial degrees on a fixed finite element mesh is discussed such that a particular element has to be refined automatically to obtain an acceptable level of accuracy by increasing p-levels non-uniformly. To verify the proposed algorithm, the limit value approach is proposed which utilizes the exact strain energy computed from the extrapolation equation. A new pre-processor is developed for the p-version finite element program in which the vector graphic editor is used for the automatic generation of node connection and coordinate by halfedge solid data structure according to uniform or nonuniform p-distribution. The general 2-D algorithm is also developed to generate face modes and internal modes in accordance with different mesh types. The quality of the error estimator is investigated with the help of two mumerical examples. The results show that the sequences of p-distributions obtained by the proposed error indicator closely follow the optimal trajectory.

• 한국정밀공학회지
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• 제23권4호
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• pp.37-43
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• 2006

In this paper, an approach to adaptive finite element analysis of three-dimensional forging processes is presented with emphasis on remeshing. In the approach, an optimal tetrahedral element generation technique is employed and the mesh density is specified by the combination of the weighted normalized effective strain and the normalized effective strain rate as well as the weighted normalized curvature. The approach is applied to computer simulation of an enclosed die forging process of a bevel gear and its results are compared with its related experiments. It has been shown that the analyzed results are in good agreement with the experimental ones.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.99-102
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• 2005

An approach to adaptive finite element analysis of three-dimensional forging processes is presented in this paper. In the approach, an optimal tetrahedral element generation technique is employed and the mesh density is specified by the combination of the normalized effective strain and the normalized effective strain rate. The approach is applied to computer simulation of an enclosed die forging process of a bevel gear and its results are compared with experiments.

• 한국전산구조공학회논문집
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• 제15권1호
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• pp.85-94
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• 2002

본 연구에서는 Bubble Mesh 기법을 이용한 적응적 최적 절점생성기법을 제안하고 이를 Element-free Galerkin 방법에 적용하였다. 무요소방법에서 제안된 일반적인 적응적 절점배치방법의 경우 적분격자를 이용하기 때문에 그 절점의 분포가 평가된 오차를 정확히 반영하지 못하고 불균등한 세분화로 인해 주변 절점분포와 급격한 절점밀도의 차이를 보이게 되어 추가적인 해석오차를 유발한다. 본 연구에서는 평가된 오차의 분포와 적분격자를 따라 구성된 불균등한 초기절점배치를 최적삼각격자 구성기법인 Bubble Mesh 기법을 이용하여 최적화 시키는 적응적 절점구성기법을 제안하였다. 절점의 불균등한 배치에 따른 추가적인 오차의 발생현상을 보이기 위해 1차원 문제를 해석하였고 본 연구에서 제안된 Bubble Mesh 기법을 이용한 적응적 무요소해석법의 적용성을 보이기 위해 2차원 문제를 해석하였다.