• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.471-476
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• 2001

Even though structural performance evaluation techniques for reinforced concrete structures have been improved, there are still many problems in the evaluation of structural performance for underground structures which interacts with surrounding soils. Since experimental evaluation of underground RC structures considering the interaction with the surrounding soil medium is quite difficult to be simulated, the evaluation for underground RC structures using an analytical method can be applied very usefully, For underground structures interacted with surrounding soils, it is important to consider path-dependent RC constitutive model, soil constitutive model, and interface model between structure and soil, simultaneously. In this paper, an elastoplastic interface model which consider thickness was proposed and importance of interface model is discussed. The effects of stiffness of structures to entire underground RC system are investigated through numerical experiment for underground RC structure for different reinforcement ratios and thickness of interfaces.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 추계학술대회 논문
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• pp.173-179
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• 1996

A computer simulation has been performed for the application to the elastoplastic stress analysis in a discontinuous composite solid. To obtain the internal field quantities of composite the micromechanics analysis and finite element analysis (FEA) were implemented. As the procedure the reasonably optimized FE mesh generations the appropriate imposition of boundary condition and the relevant postprocessing such as elastoplastic thermomechanical analysis were taken into account. For the numerical illustration an aligned axisymmetric single fiber model has been employed to assess field quantities. It was found that the proposed simulation methodology for stress analysis is applicable to the complicated inhomogeneous solid for the investigation of micromechanical behavior.

• 비파괴검사학회지
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• 제14권1호
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• pp.7-15
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• 1994

동을 중간재로 하는 $Si_3N_4/SUS304$ 접합재의 접합계면 근방의 잔류응력 분포를 유한요소법과 X선 응력측정법을 이용하여 해석을 하였다. 그 결과, 접합재의 세라믹부 계면 근방의 잔류응력 분포를 정량적으로 밝혀낼 수 있었다. 세라믹부에 발생되는 접합 잔류응력은 접합계면 근방에서 대단히 크게 나타났으며, 특히 최대인장 잔류응력 ${\sigma}_x$는 단부에서 발생하였다. 한편, ${\sigma}_x$는 접합계면 근방에서 3차원분포를 하고 있기 때문에 2차원 유한요소 해석결과와는 대단히 다른 값을 나타내고 있으며, 특히 시험편 중앙부의 계면 근방에서는 X선 실측결과가 인장 잔류응력임에 반하여 2차원 유한요소 해석결과는 압축 잔류응력으로 계산되어짐을 알았다. 따라서, 이와같은 3차원 분포를 하고 있는 접합계면 근방의 잔류응력 ${\sigma}_x$보다 간편하고 정확하게 예측할 수 있는 유한요소 해석모델에 대하여 서로 검토하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.507-512
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• 2003

A finite element analysis for near-net-shape forming of Al6061 powder was performed under warm pressing. The advantages of warm compaction by rubber isostatic pressing were discussed to obtain parts with better density distributions. To simulate densification and deformed shape of a powder compact during warm pressing, the elastoplastic constitutive equation based on yield function of Shima-Oyane was implemented into a finite element program(ABAQUS). The hyperelastic constitutive equation based on the Ogden strain energy potential was employed to analyze nonlinear elastic response of rubber. Finite element results were compared with experimental data for Al6061 powder compacts under warm pressing.

• 대한기계학회논문집A
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• 제28권8호
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• pp.1140-1151
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• 2004

This paper reports on the finite elements analysis for die compaction process of cemented carbide tool parts. Experimental data were obtained under die compaction and triaxial compression with various loading conditions. The elastoplastic constitutive equations based on the yield function of Shima and Oyane were implemented into an explicit finite element program (ABAQUS/Explicit) and implicit finite element program (PMsolver/Compaction-3D) to simulate compaction response of cemented carbide powder during die compaction. For simulation of die compaction, the material parameters for Shima and Oyane model were obtained by uniaxial die compaction test. Explicit finite element results were compared with implicit results for cemented carbide powder.

• Structural Engineering and Mechanics
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• 제15권2호
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• pp.199-223
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• 2003

The formulation of a non-linear shear deformable shell element is presented for the solution of stability problems of stiffened plates and shells. The formulation of the geometrical stiffness presented here is exactly defined on the midsurface and is efficient for analyzing stability problems of thick plates and shells by incorporating bending moment and transverse shear resultant force. As a result of the explicit integration of the tangent stiffness matrix, this formulation is computationally very efficient in incremental nonlinear analysis. The element is free of both membrane and shear locking behaviour by using the assumed strain method such that the element performs very well in the thin shells. By using six degrees of freedom per node, the present element can model stiffened plate and shell structures. The formulation includes large displacement effects and elasto-plastic material behaviour. The material is assumed to be isotropic and elasto-plastic obeying Von Mises's yield condition and its associated flow rules. The results showed good agreement with references and computational efficiency.

• 대한기계학회논문집A
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• 제21권7호
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• pp.1116-1126
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• 1997

The effects of friction between powder and a mandrel on densification behavior of metal powder were investigated under cold isostatic pressing. The elastoplastic constitutive equations based on the yield function of Shima and Oyane were implemented into finite element program (ABAQUS) to simulate compaction responses of metal powders during cold isostatic pressing. The friction coefficients between powder and mandrels with different roughness were determined by comparing experimental data and finite element results. Density distributions in the powder compacts were also studied for different friction coefficients. Finite element results were compared with experimental data for pure iron powder under cold isostatic pressing.

• 대한기계학회논문집A
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• 제21권7호
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• pp.1073-1080
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• 1997

The stage 1 compaction behavior of tool steel powder under die pressing was studied. The friction effects between the powder and the die wall under different die pressing modes were also investigated. The elastoplastic constitutive equations based on the yield functions by Fleck et al. and by Shima and Oyane were implemented into a finite element program to simulate die compaction processes. Finite element calculations were compared with experimental data for densification and density distribution of tool steel powder under single and double action die pressing. Finite element calculations using the yield function by Fleck et al. agreed better with experimental data than by Shima and Oyane.

• 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.

• 소성∙가공
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• 제26권4호
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• pp.205-209
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• 2017

In this paper, finite element prediction of deformation of material due to springback after material removal by an axisymmetric forging fabrication at room temperature is conducted. An elastoplastic finite element method is employed considering die plastic deformation. The predictions of a springback analysis conducted after the final stroke of an axisymmetric cold forging process containing residual stresses are utilized to be mapped onto the final material after the material removal. It is assumed that material removal occurs at an instant, i.e., all the material to be removed disappears at once. The predictions are compared with experiments, revealing strong qualitative agreement.