• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1991년도 가을 학술발표회 논문집
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• pp.75-80
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• 1991

The purpose of this study is to ascertain the robustness of p-version model with hierarchic intergrals of Legendre shape functions in various applications including plane stress/strain, axisymmetric and shell problems. The most important symptoms of accuracy failure in modern finite elements are spurious mechanisms and a phenomenon known as locking which are exhibited for incompressible materials and irregular shapes which contain aspect ratios(R/t, a/b), tapered ratio(d/b), and skewness. The condition numbers and energy norms are used to estimate numerical errors, convergence characteristics and algorithmic efficiencies for verifying the aforementioned symptoms of accuracy failure. Numerical results from p-version models are compared wi th those from NASTRAN, SAP90, and Cheung's hybrid elements.

• 대한토목학회논문집
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• 제8권2호
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• pp.25-32
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• 1988

본 연구에서는 8절점 28자유도를 갖는 사각형 고차 판 유한 요소를 면내고차 변위를 고려하여 3차원 연속체로부터 유도하였다. 요소매트릭스들은 판의 운동방정식으로부터 Galerkin 가중잔차법으로 유도하고 감차적분을 수행하여 구하였다. 고차 판 유한요소를 이용하여 판의 처짐해석과 자유진동해석을 수행한 결과 판의 두께와 경게조건에 관계없이 매우 정확한 결과를 나타내었다.

• Structural Engineering and Mechanics
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• 제5권1호
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• pp.69-83
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• 1997

A new efficient hybrid/mixed thin~moderately thick plate bending element with 6-node (HM6-14) is formulated based on the Reissner-Mindlin plate bending theory. The convergence of this element is proved by error estimate theories and verified by patch test respectively. Numerical studies on such an element as HM6-14 demonstrate that it has remarkable convergence, invariability to geometric distorted mesh situations, to axial rotations, and to node positions, and no "locking" phenomenon in thin plate limit. The present element is suitable to many kinds of shape and thin~moderately thick plate bending problems. Further, in comparison with original hybrid/mixed plate bending element HP4, the present element yields an improvement of solutions. Therefore, it is an efficient element and suitable for the development of adaptive multi-field finite element method (FEM).

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.11-17
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• 2000

,An residual stress and out-of plane deformation produced by butt welding was analyzed by four kinds of 3D-FEM programs(Thermal El-P1 Analysis) developed by authors. The magnitude of deformation of perpendicular to the welding line generated by butt welding was large when the reduced integration method was used. This was because of removal of the locking phenomenon, which it was generally known that the stiffness of the shear component of out-of-plane was largely evaluated. And the magnitude of residual stress was analyzed by using the FEM program based on a large and small deformation theory was similar to that was analyzed by the redeced integration method.

• 전산구조공학
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• 제10권2호
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• pp.139-148
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• 1997

A finite element method is programmed to analyse the nonlinear behavior of axisymmetric structures. The lst order Mindlin shell theory which takes into account the transversal shear deformation is used to formulate a conical two node element with six degrees of freedom. To evade the shear locking phenomenon which arises in Mindlin type element when the effect of shear deformation tends to zero, the reduced integration of one point Gauss Quadrature at the center of element is employed. This method is the Updated Lagrangian formulation which refers the variables to the state of the most recent iteration. The solution is searched by Newton-Raphson iteration method. The tangent matrix of this method is obtained by a finite difference method by perturbating the degrees of freedom with small values. For the moment this program is limited to the analyses of non-linear elastic problems. For structures which could have elastic stability problem, the calculation is controled by displacement.

• 한국전산구조공학회논문집
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• 제29권2호
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• pp.201-208
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• 2016

최근에 요소망의 재구성이 불필요하고 균열의 가시화에 강점을 가지는 확장유한요소법(XFEM)을 이용한 균열 해석이 많이 연구되고 있지만 주로 단일재료로 이루어진 부재의 해석에 집중되어 있다. 본 논문에서는 복합재료 부재인 철근콘크리트 보의 다중균열 해석에 확장유한요소법을 적용하며 그 적용성과 타당성을 살펴보았다. 확장유한요소해석 기능이 탑재된 상용 해석프로그램인 ABAQUS를 사용하여 균열해석을 수행하였으며 그 결과를 실험결과와 비교하였다. 확장유한요소법에서 인접요소에 동시에 균열이 발생할 경우 균열의 불연속성이 나타나지 않은 부가자유도 잠김 현상을 발견하였고 이에 대한 원인과 그 해결방안을 제시하였다. 또한 실험결과와 유사한 다중균열 발생을 위한 모델링 기법도 제시하였다. 확장유한요소법을 이용한 해석결과는 실험결과와 유사한 균열 양상 및 균열 간격을 보여 주었으며 하중-변위 관계에 있어서도 실험에 근접한 결과를 보여 주었다.

• 한국전산구조공학회논문집
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• 제26권4호
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• pp.255-262
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• 2013

본 논문에서는 아이소-지오메트릭 기법을 기반으로 민들린 후판에 대한 형상 설계민감도 해석법을 제시하였다. 아이소-지오메트릭 기법은 정확한 기하학적 형상의 표현, 요소 사이의 높은 연속성 등 바람직한 강점들을 가지고 있으며 궁극적으로는 해석해로의 빠른 수렴성과 정확한 설계민감도를 제공한다. 선형 형상함수를 사용하는 유한요소법과는 달리 아이소-지오메트릭 기법에서는 높은 차수의 NURBS 기저함수를 활용하여 CAD 형상의 법선벡터와 곡률을 정확하게 고려한다. 전단 잠김(Shear locking) 현상을 극복하기 위해서 선택적 감소적분(Selective reduced integration) 기법을 사용하였다. 이 간단한 방법은 복잡한 정식화 과정 없이 정확한 아이소-지오메트릭 형상 설계민감도 해석을 수행한다. 굽힘 문제에 대한 수치예제를 통하여 제안된 아이소-지오메트릭 해석과 유한요소 해석을 비교하였으며, 유한차분 설계민감도와 비교하여 아이소-지오메트릭 형상 설계민감도는 매우 정확함을 확인하였다.

• 한국전산구조공학회논문집
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• 제18권3호
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• pp.311-320
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• 2005

본 논문에서는 평판구조물의 정적 및 동적해석에 사용할 목적으로 성능이 향상된 평판유한요소를 제시하였다. 이 요소는 비적합변위형과 선택적 감차적분방법 그리고 대체전단변형률장을 복합적으로 적용하여 각각의 장점들을 포함하는 향상된 거동을 보여주고 있다. 또한 비적합변위형의 적용으로 발생되는 조각시험의 실패 문제점을 해결하기 위하여 직접수정법을 평판유한요소의 개선에 사용하였다. 대표적인 검증문제에 대한 수치해석작업을 통하여 본 연구에서 개발한 요소는 가상적인 제로에너지모드 및 전단잠김현상의 발생과 같은 문제를 나타내지 않음을 알 수 있었다. 특히 찌그러진 형상으로 모형화 한 경우에 있어서도 전단잠김현상이 발생하지 않았다. 본 연구에서 수행한 동적반응해석 시험에 있어서도 이론해와 잘 일치하는 결과를 보여주었다.

• Structural Engineering and Mechanics
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• 제15권1호
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• pp.83-114
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• 2003

A new simple 3-node triangular flat-shell element with standard nodal DOF (6 DOF per node) is proposed for the linear and geometrically nonlinear analysis of very thin to thick plate and shell structures. The formulation of element GT9 (Long and Xu 1994), a generalized conforming membrane element with rigid rotational freedoms, is employed as the membrane component of the new shell element. Both one-point reduced integration scheme and a corresponding stabilization matrix are adopted for avoiding membrane locking and hourglass phenomenon. The bending component of the new element comes from a new generalized conforming Kirchhoff-Mindlin plate element TSL-T9, which is derived in this paper based on semiLoof constrains and rational shear interpolation. Thus the convergence can be guaranteed and no shear locking will happen. Furthermore, a simple hybrid procedure is suggested to improve the stress solutions, and the Updated Lagrangian formulae are also established for the geometrically nonlinear problems. Numerical results with solutions, which are solved by some other recent element models and the models in the commercial finite element software ABAQUS, are presented. They show that the proposed element, denoted as GMST18, exhibits excellent and better performance for the analysis of thin-think plates and shells in both linear and geometrically nonlinear problems.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.38.2-38.2
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• 2010

Biomimetc is a new domain of learning that proposes a solution getting clues from nature. There seems to be a sign of this phenomenon in fields of Renewable Energy. Foe example, Wind power was imitate the whale's fin that was improve efficiency of generating energy. This study focused on the photovoltaic generation as the instance of applying biomimetic. Efficiency is the most important factor in field of Photovoltaic generation. When given solar cell taking the sun light, most important fields of the study are absorb more light and increase the quantity of generation. For improving efficiency, the solar cell were builded up textures of taking a pyramid form, such a surface structure taking a role for remaining the light. This effects do the role as increasing absorbing efficiency. Such phenomenon calls Light Trapping, locking up the light on the surface of solar cell for a long time. Light is a vital factor to plants in the nature. Plants grow up through the photosynthesis that absorbing light for growth and propagation. So, plants make a effort how can absorb more the light in poor surroundings. This study set up a goal that imitates the minute surface structure of plants and applies to the existing solar cells's surface structure, so it can improve the efficiency of absorbing light. We used Light Tools software analyzing geometrical optics to analyze efficiency about new designed textures on the computer. We made a comparison between existing textures and new designed textures. Consequently, new designed textures were advanced efficiency, absorbing rates of light increasing about 7 percent. In comparison with existing and new textures, advancing about 20 percent in the efficient aspect.