• 한국지반공학회논문집
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• 제16권4호
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• pp.183-190
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• 2000

본 연구에서는 피에조콘 시험의 유한요소해석을 점탄소성 bounding surface 구성모델과 large displacement large deformation 개념을 이용하여 수행하였다. 이에 따라 구성모델, 가상일의 방정식 및 관련 유한요소 식 등을 Updated Lagrangian reference frame에서 formulation 하였으며 지반의 거동은 theory of mixtures를 통하여 설명하였다. Theory of mixtures 역시 Updated Lagrangian reference frame에서 formulation하였다. 구성모델 중 점성 부분이 전체 formulation 과정에 중요한 영향을 미친다는 사실이 고찰되었다. 유한요소 해석의 결과는 실내에서 실시한 대형 모델시험의 결과와 비교, 분석하였다. Formulation 과정은 'I' 결과는 'II'에서 설명된다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.375-382
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• 2003

Porous media consist of physically and chemically different materials and have an extremely complicated behavior due to the different material properties of each of its constituents. In addition, the internal structure of porous media has generally a complex geometry that makes the description of its mechanical behavior quite complex. Thus, in order to describe and clarify the deformation behavior of porous media, constitutive models for deformation of porous media coupling several effects such as flow of fluids of thermodynamical change need to be developed in frame of Arbitrary Lagrangian Eulerian (ALE) description. The aim of ALE formulations is to maximize the advantages of Lagrangian and Eulerian methods, and to minimize the disadvantages. Therefore, this method is appropriate for the analysis of porous media that are considered for the behavior of solids and fluids. First of all, governing equations for saturated porous media based on ALE description are derived. Then, weak forms of these equations are obtained in order to implement numerical method using finite element method. Finally, Petrov-Galerkin method Is applied to develop finite element formulation.

• 한국지반공학회논문집
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• 제16권4호
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• pp.191-199
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• 2000

본 연구에서는 피에조콘 시험의 유한요소해석을 수행하였다. 이를 위하여 점탄소성 bounding surface 모델, 가상일의 방정식(virtual work equation) 및 theory of mixtures를 Updated Lagrangian reference frame에서 formulation하였다. 결과적으로 구성된 유한요소 formulation을 컴퓨터 프로그래밍 하였으며 유한요소해석에서 얻은 콘 저항치, 과잉간극수압 및 간극수압소산 등의 결과를 실험치와 비교 분석하였으며 피에조콘 주변의 응력, 변형율 및 과잉간극수압의 contour를 유한요소해석에서 구하여 이를 고찰하였다. 비등방성 및 점성이 추가된 구성모델을 사용함으로서 응력의 비등방성 및 관입속도를 효과적으로 simulation할 수 있었다. 유한요소 Formulation 과정은 'I' 결과는 'II'에서 설명된다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 추계학술대회논문집
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• pp.20-28
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• 1996

An Eulerian finite element method for the analysis of steady state rolling/extrusion of sintered powder metals is presented. Initial guess of the porosity distribution in an Eulerian mesh is obtained from the velocity and scaled pressure field computed by the Consistent Penalty finite element formulations-the standard one and the consistent penalty type one-are invoked for the analysis of strain hardening, dilatant viscoplastic deformation of porous metals. Comparisons of the predicted distributions of porosity to those by a Lagrangian finite element method and by experiments reported in the articles prove the effectiveness and validity of the proposed method.

• 한국정밀공학회지
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• 제22권5호
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• pp.205-213
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• 2005

This paper addresses a method for numerical simulation in the pressing process of hot glass. Updated Lagrangian finite element formulations are employed for the flow and energy equations to accommodate moving meshes. The model is assumed axi-symmetric and creep flow is assumed due to the high viscosity. Commercial software ANSYS is used to solve the coupled flow and energy equations. Moving contact points as well as free surface during the pressing are effectively calculated and updated by utilizing API functions of CAD software Unigraphics. The mesh distortion problem near the wall is overcome by automatic remeshing, and the temperatures of the new mesh are conveniently interpolated by using a unique function of ANSYS. The developed model is applied to the pressing process of TV glasses. In conclusion, the presented method shows that the pressing process accompanying moving boundary can be simulated by effectively combining general purpose software without resorting to special dedicated codes.

• 대한토목학회논문집
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• 제10권3호
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• pp.29-38
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• 1990

본(本) 연구(硏究)에서는 종래(從來)의 일반적(一般的)인 비선형(非線型) 해석(解析) 방법(方法)인 Lagrangian방법(方法)을 개선(改善)한 새로운 Pseudo Lagrangian방법(方法)에 의한 기하학적(幾何學的) 선형(非線型) 보요소(要素)의 정식화(Formulation) 과정을 제시(提示)하고 예제해석(例題解析)을 통한 대변형(大變形) 해석결과(解析結果)를 고찰(考察)하여 Pseudo Lagrangian방법(方法)에 의한 보요소(要素)의 대변형(大變形) 해석(解析)의 타당성(妥當性)과 정확도(正確度)를 검증(檢證)하였다. Pseudo Lagrangian방법(方法)에서는 변형전(變形前) 또는 변형후(變形後)의 상태(狀態)를 기준(基準)로 변형(變形)을 나타내는 Total Lagrangian방법(方法)과는 달리 어떠한 물리적(物理的)인 의미(意味)가 없는 임의(任意)의 Pseudo(가상(假想))변형상태(變形狀態)를 기준(基準)으로 변형(變形)을 나타낸다. 유한요소법(有限要素法)에 의한 비선형(非線形) 해석시(解析時) 일반적(一般的)인 Lagrangian방법(方法)은 각(各) 구조요소(構造要素)에 대한 유한요소(有限要素) Mapping과 변형(變形) Mapping을 따로 수행(遂行)하여야 하는데 비하여 Pseudo Lagrangian방법(方法)에서는 한번의 직접적(直接的) Mapping으로 구조요소(構造要素)의 변형상태(變形狀態)를 나타낸다. 예제분석(例題分析) 결과(結果)는 이 PLF방법(方法)에 의한 비선형(非線型) 정식화가 종래(從來)의 Lagrangian방법(方法)보다 적용성(適用性)이 양호(良好)하며 유도과정(誘導過程)이 간편(簡便)함을 보여주고 있으며 PLF방법(方法)에 의한 보요소(要素)의 비선형(非線型) 해석(解析)이 매우 정확(正確)한 결과(結果)를 나타내고 있음을 입증(立證)하고

• Structural Engineering and Mechanics
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• 제72권4호
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• pp.433-441
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• 2019

In this paper, geometrically nonlinear static analysis of laminated composite beams is investigated under hygrothermal effect. In the solution of problem, the finite element method is used within the first shear beam theory. Total Lagrangian approach is used nonlinear kinematic model. The geometrically nonlinear formulations are developed for the laminated beams with hygro-thermal effects. In the nonlinear solution of the problem, the Newton-Raphson method is used with incremental displacement. In order to verify of obtained formulations, a comparison study is performed. The effects of the fiber orientation angles, the stacking sequence of laminates, temperature rising and moisture changes on the nonlinear static displacements and configurations of the composite laminated beam are investigated in the numerical results.

• 대한기계학회논문집A
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• 제21권11호
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• pp.1912-1920
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• 1997

In the analysis of metal forming process, ALE(Arbitrary Lagrangian Eulerian) finite element methods have been increasingly used for the capability to control mesh independently from material flow. The methods can be divided into two groups i.e., coupled and split formulations. In the present work, the split ALE formulation is used for computational efficiency. A split ALE finite element method developed for rigid-viscoplastic materials and applied to the analysis of hot square die extrusion. Since thermal state greatly affects the product quality, an ALE scheme for temperature analysis is also presented. As computational examples, profile shapes as square and cross-like sections are chosen.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.458-461
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• 2009

Thermo-mechanical simulation of the Friction Stir Spot Welding (FSSW) processes was performed for the AA5083-H18 sheets, utilizing commercial Finite Element Method (FEM) and Finite Volume Method (FVM) which are based on Lagrangian and Eulerian formulations, respectively. The Lagrangian explicit dynamic FEM code, PAM-CRASH, and the Eulerian Computational Fluid Dynamics (CFD) FVM code, STAR-CD, were utilized to understand the effect of pin geometry on weld strength and material flow under the unsteady state condition. Using FVM code, material flow pattern near the tool boundary was analyzed to explain the weld strength difference between the weld by cylindrical pin and the weld by triangular pin, while the frictional energy concept using the FEM code had limitation to explain the weld strength difference.

• Structural Engineering and Mechanics
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• 제7권1호
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• pp.111-126
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• 1999

The work presented here focuses on the development of suitable discretised formulations, for large-displacement shape and non-shape design sensitivity analysis (DSA), which enable the straightforward incorporation of structural optimisation into established finite element analysis (FEA) codes. For the generalised displacement-based functional the design sensitivity vector has been expressed in terms of displacement sensitivity. The Total Lagrangian formulation is utilised for modelling of large deformation of truss structures. The variational formulation of the sensitivity analysis procedure is discretised by using "pseudo" - finite elements, Results are presented for the sensitivity analysis and optimisation of standard truss structures. For the purposes of this work, the analysis and optimisation procedures outlined below are incorporated into the FEA code ABAQUS.