• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.17 no.1
• /
• pp.1-10
• /
• 2004

Adaptive finite element analysis, in which its solution error meets with the user defined allowable error, is recently used to improve the reliability of finite element analysis results. This adaptive analysis is composed of two procedures; one is the error estimation of an analysis result and the other is the reconstruction of finite elements. In the (p-method, an element size is controlled by relocating of nodal positions (r-method) and the order of an element shape function is determined by the hierarchical polynomial (p-method) corresponding to the clement solution error by the enhanced SPR. In order to show the effectiveness and the accuracy of the suggested rp-method, various numerical examples were analyzed and these analysis results were examined by comparing with those obtained by the existed methods.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.37 no.4
• /
• pp.205-213
• /
• 1988

It has been very difficult to solve the semiconductor problems by numerical analysis techique due to the strong nonlinearity of the governing equations. Thus, we proposed a double structured adaptive refinement scheme to the finite element analysis of semiconductor devices, which guarantees a succesive convergency and gives better quality to the solutions.i.e., in the first step, the main factor of divergence in the current continuity equation is eliminated and the next, the solution quality is improved by reducing the discontinuity of current. The result of test application to the GaAs MESFET model shows that the proposed method is much dffective and efficient in the numerical analysis of semiconductor.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.26 no.5
• /
• pp.385-392
• /
• 2013

The finite element method has become the most widely used method of structural analysis and recently, the method has often been applied to complex dynamic and nonlinear structural analyses problems. Even for these complex problems, where the responses are hard to predict, finite element analyses yield reliable results if appropriate element types and meshes are used. However, the dynamic and nonlinear behaviors of a structure often include large deformations in various portions of the structure and if the same mesh is used throughout the analysis, some elements may deform to shapes beyond the reliable limits; thus dynamically adapting finite element meshes are needed in order for the finite element analyses to be accurate. In addition, to satisfy the users requirement of quick real run time of finite element programs, the algorithms must be computationally efficient. This paper presents an adaptive finite element mesh generation scheme for dynamic analyses of structures that may adapt at each time step. Representative strain values are used for error estimates and combinations of the h-method(node movement) and the r-method(element division) are used for mesh refinements. A coefficient that depends on the shape of an element is used to limit overly distorted elements. A simple frame example shows the accuracy and computational efficiency of the scheme. The aim of the study is to outline the adaptive scheme and to demonstrate the potential use in general finite element analyses of dynamic and nonlinear structural problems commonly encountered.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.3
• /
• pp.265-272
• /
• 2007

The finite element linear buckling analysis of folded plate structures using adaptive h-refinement methods is presented in this paper. The variable-node flat shell element used in this study possesses the drilling D.O.F. which, in addition to improvement of the element behavior, permits an easy connection to other elements with six degrees of freedom per node. The Box-typed structures can be analyzed using these developed flat shell elements. By introducing the variable-node elements some difficulties associated with connecting the different layer patterns, which are common in the adaptive h-refinement on quadrilateral mesh, can be overcome. To obtain better stress field for the error estimation, the super-convergent patch recovery is used. The convergent buckling modes and the critical loads associated with these modes can be obtained.

• Computational Structural Engineering
• /
• v.6 no.3
• /
• pp.125-137
• /
• 1993

Recently, many researches are being dealt with the adaptive method for improving the accuracy of finite element solution. This paper deals with rh-methods that are the combination of r and h-method ; r-method is to relocate the nodes for the grid optimization, h-method is to divide the elements with great error into the equal shape. As a results, rh-method has the same error decrease and convergence as h-method in the same degree of freedom, but it has more exact result of finite element in the state of restraining degrees of freedom than h-method alone.

• Electrical & Electronic Materials
• /
• v.6 no.2
• /
• pp.137-146
• /
• 1993

유한요소법을 이용하여 반도체 해석을 하는 경우 국부적인 overshoot, 진동 및 해의 발산등의 문제점등이 발생하기 쉽다. 이는 지배방정식의 특성에 좌우되는 경우가 많은데 특히 반도체 전류연속 방정식을 처리하는 데는 그 해석이 매우 불안정하다. 본 연구에서는 유한요소법을 반도체 해석에 적용하는 경우 해의 발산원인을 적용 방정식의 수치적 안정도 검사에 의하여 도출하였으며 이 요인이 요소상수 m의 값에 좌우됨을 밝혔다. 또한 요소상수가 후치조작에 의해서만 계산될 수 있는 단점을 보완하기 위하여 적응요소법을 도입하여 프로그램으로 구현함으로써 임의의 초기 요소망과 초기치에 대해서도 자동적으로 해의 수렴을 얻을 수 있는 적응해석 프로그램을 개발하였다. 본 프로그램의 효용성을 검증하기 위하여 GaAs MESFET 모델을 선정하여 계산하였고 산출 결과를 검토해 본 결과 임의의 초기치에 대해서도 강인한 수렴성을 얻을 수 있었으며 요소 분할이 필요한 부위에만 집중됨으로써 비교적 적은 수의 요소만으로도 해를 얻을 수 있음을 확인하였다.

• Journal of the Society of Naval Architects of Korea
• /
• v.33 no.1
• /
• pp.90-97
• /
• 1996

The optimal mesh refinement has a meaning that error of the every element is within an allowable level and in uniformly distributed. The adaptive mesh generation may be required to achieve the optimal mesh generation. For the purpose of optimal mesh generation, an error estimation and an adaptive mesh refinement are required. Using the adaptive mesh generation the second finite element analysis is performed with the result of the first analysis. In the process the error estimation is required. In this study the adaptive mesh generation program for triangular element is developed, and for a posteriori error estimation the stress projection approach is considered. It has been found the multigrid technique, where the error estimation and the mesh generation are combined in multi-step of analysis, may be used efficiently in the finite element analysis.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.3
• /
• pp.447-455
• /
• 1999

An adaptive mesh generation scheme is developed for effective non-linear analysis of the shell structures under large deformation. In particular, based on a posteriori error estimation, remeshing method on each load step is of primary interest here. An advancing front method, called paving method, is adopted for remeshing. It can be known that the adaptive mesh generation using contours of spacing values obtained from stress errors has an advantage in the adaptive analysis of the shell structures.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.7 s.196
• /
• pp.7-12
• /
• 2007

• Computational Structural Engineering
• /
• v.11 no.1
• /
• pp.90-95
• /
• 1998

본 고에서는 비압축성 점성유체의 유한요소해석 기법을 소개하였다. 대류항의 상류화 기법으로 안정된 해를 도출할 수 있으며 Penalty 방법에 기반하여 압력항을 지배방정식으로부터 소거함으로써 해석시간과 요구저장공간을 감소시켰다. 실린더 주변의 유동장을 해석하여 와의 방출을 성공적으로 묘사하였으며 항력계수를 17%정도의 오차로 계산하였다. 적응적 요소세분화 기법에 대한 연구를 통해 적절한 오차평가 기법 및 최적의 체눈을 형성하는 기법을 제시하였다. 또한 동적 해석에 적합한 요소재결합 알고리즘에 대한 연구가 진행중이다. 본 고의 결과는 직접적으로 풍공학분야에 사용하기에는 아직 계산 시간의 효율성이나 해의 정확도 및 안정성면에서 무리가 있으나 추가적인 연구를 통하여 해석기법의 개선을 도모하고 컴퓨터 등 계산장비의 급속한 발전으로 장래에 경쟁력을 획득할 수 있을 것으로 기대된다.