• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2183-2188
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• 2009

This paper describes an automatic mesh generation system for finite element analysis of three-dimensional cracks. It is consisting of fuzzy knowledge processing, bubble meshing and solid geometry modeler. This novel mesh generation process consists of three sub-processes: (a) definition of geometric model, i.e. analysis model, (b) generation of bubbles, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional crack structures. Bubble is generated if its distance from existing bubble points is similar to the bubble spacing function at the point. The bubble spacing function is well controlled by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Practical performances of the present system are demonstrated through several mesh generations for 3D cracks.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.19-19
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• 2003

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.542-545
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• 2010

재료의 마이크로 스케일 해석에서 결정의 geometrically necessary dislocation (GND) 효과에 의한 소성구배(plastic gradient)를 고려하는 것은 재료의 소성 거동을 분석하는데 영향을 미친다. 본 연구에서는 먼거리(long range)에서 전위(dislocation)의 영향을 고려하는 GND의 효과를 적용하여 소성 구배의 영향을 받는 다결정(polycrystal) 고체의 거동을 유한요소해석을 이용하여 살펴보았다. 재료의 거동을 분석하기 위해 탄성(elastic)과 소성(plastic) 변형에 먼 거리 변형률(long range strain)을 고려한 항(term)이 포함된 변형 구배(deformation gradient)의 multiplicative decomposition 모델을 사용하였다. 먼 거리 변형률에 의한 영향을 고려하기 위해 구배 경화 계수(gradient hardness coefficient)와 먼 거리 변형률 길이에 대한 재료변수(parameter)가 사용되었다. 각각의 계수들이 다결정 고체의 거동에 미치는 영향을 확인하기 위해 두 변수의 적용에 따른 다결정 고체의 거동을 분석하였다. 다결정 재료의 GND 효과에 의한 소성 구배 효과를 고려해서, 고려하지 않은 경우와 비교하여 발생하는 경화(hardening)의 차이를 분석함으로서 GND에 의한 다결정 고체 거동의 영향을 확인하였다.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.1
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• pp.23-28
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• 2024

Electronic products utilizing flexible devices experience harsh mechanical deformations in real-use environments. As a result, researches on the mechanical reliability of these flexible devices have attracted considerable interest among researchers. This study employed previous bending strain models and finite element analysis to predict the maximum bending strain of metal films deposited on flexible substrates. Bending experiments were simulated using finite element analysis with variations in the material and thickness of the thin films, and the substrate thickness. The results were compared with the strains predicted by existing models. The distribution of strain on the surface of film was observed, and the error rate of the existing model was analyzed during bending. Additionally, a modified model was proposed, providing mathematical constants for each case.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.74-82
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• 2013

This paper deals with a single stage coilgun which is a variety of EML(ElectroMagnetic Launcher) and can be applied to launching a small satellite. We propose a mathematical and physical model in order to design a single stage coilgun and study physical characteristics related to design parameters. A proposed mathematical and physical model is verified by electromagnetic FEM software FEMM 4.2.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.3
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• pp.281-292
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• 1999

지반-기초 상호작용계를 해석할 때 실제로 지반은 다양한 지반종류와 다층으로 형성되어 있으므로 지반 특성의 변화를 고려해야 한다. 초기의 대부분의 상호작용계의 정·동적 해석은 지반의 복잡한 성질을 역학적으로 탄성거동을 한다고 가정한 Winkler 지반모델 혹은 지반을 등방성이고 균질한 반무한 탄성체로 가정한 반무한 탄성지반 모델로 보아 수행되었다. 본 연구는 유한 요소법을 이용하여 지반-기초 상호작용계의 동적 거동을 해석하기 위해 기초는 4절점 후판요소를 사용하고 지반은 지반특성을 고려할 수 있도록 8절점 6면체 요소를 사용하였고, 지반의 감쇠효과 및 지반특성을 고려한 지반-기초 상호작용계의 동적 거동을 유한요소법으로 해석하고 지반의 영향범위를 결정하는 것이다.

• International Journal of Highway Engineering
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• v.9 no.1 s.31
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• pp.39-46
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• 2007

Different backcalculation results for the same material properties are caused by different structural geometry. In this paper, based on real simulation results for typical pavement systems using 3-dimensional FE models, modified AREA graphs are proposed to graphically backcalculate modulus of elasticity of slab and subgrade based on center deflection and AREA. In modified graph for single infinity slab models, deflection and AREA are increased in deeper depth to bedrock. But, effects of depth to bedrock more than 4.0 meters on backcalculation results are negligible. And, center deflection and AREA generated from multifinite slab models are larger than those of single infinity slab models with same depth to bedrock.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.4
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• pp.309-315
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• 2016

Recently, finite element analysis technique has been widely used for structural and mechanical understandings of human body in the dentistry field. This research proposed an effective finite element modeling method based on CT images, and parametric studies were performed for the occlusal simulation. The analyses were performed considering linear material behaviors and nonlinear geometrical effect, and validated with the experimental results. In addition, the skull models with two different molar relations such as Class I and full-CUSP Class II were generated and the analyses were performed using the proposed analytical method. As results, the relationships between the mandibular movement and occlusal force of both two models showed similar tendency in human occlusal force. However, stress was evenly distributed from teeth to facial bone in the skull model with Class I, while stress concentration was appeared in the model with full-CUSP Class II due to the changes of occlusal surfaces of the model.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.19-25
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• 2004

The linear analysis for the balance of linear momentum of a structure is relatively easy to perform, but the error becomes large when the structure experiences large deformation. Therefore, the material and geometric nonlinearity need to be considered for the precise calculations in that case. The plastic flow of a ductile steel-like metal mainly transforms its dissipated mechanical energy into heat, which transfers under the first and second law of thermodynamics. This heat increases the temperature of the material and the strength of the material decreases accordingly, which affects mechanical behavior of the given structure. This paper presents a finite-strain thermo-elasto-plastic steel model. This model can handle large deformation and thermal load simultaneously, which is common during earthquake periods. Two 3-dimensional finite element analyses verify this formulation.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.599-606
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• 2014

Since progressive collapse of tall buildings can cause enormous damage, it should be considered during the design phase of tall buildings. The progressive collapse analysis of tall buildings using finite element methods is almost impossible due to the vast amount of computing time. In this paper, applied element method was evaluated as an alternative to the finite element method. Reduced DOFs modeling technique was proposed to enable the progressive collapse analysis of tall buildings. The reduced DOFs model include only the part which is subjected to direct damage from blast load and the structural properties such as mass, transferred load and stiffness of excluded parts are accumulated into the top story of the reduced DOFs model. The proposed modeling technique was applied to the progressive collapse analysis of 20-story RC building using three collapse scenarios. The reduced DOFs model showed similar collapse behavior to the whole model while the computing time was reduced by 30%. The proposed modeling technique can be utilized in the progressive collapse analysis of tall buildings due to abnormal loads.