• 한국전산구조공학회논문집
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• 제15권4호
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• pp.649-659
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• 2002

다양한 평면변형률 시편들의 균열선단 탄·소성 응력상태들에 대한 경우, 여러 연구들을 동해, J-T접근방법의 유효 타당성이 충분히 검증되어졌다. 그러나 J-T 두 변수에 의한 균열선단 응력장 예측의 타당성을 보편화시키기 위해서는, 평면변형률 시편들과 같이 이상화된 구조가 아닌 실제적인 3차원 구조형상에 대한 연구가 필요하다. 이를 배경으로 본 연구에서는 평판과 직관에 대해 완전 3차원 유한요소해석을 수행하여 얻어진 응력장과 계산된 J-T두 변수로 예측되는 응력장을 비교함으로써, J-T 접근방법의 유효성 내지 한계성을 규명하였다.

• Steel and Composite Structures
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• 제21권6호
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• pp.1307-1325
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• 2016

Nonlinear behavior of two-span, continuous composite steel-concrete girders strengthened with Carbon Fiber Reinforced Polymers (CFRP) bonded to the top of concrete slab over the negative moment region was evaluated using a non-linear Finite Element (FE) model in this paper. A three-dimensional FE model of continuous composite girder using commercial software ABAQUS simulated and validated with experimental results. The interfacial regions of the composite girder components were modeled using suitable interface elements. Validation of the proposed numerical model with experimental data confirmed the applicability of this model to predict the loading history, strain level for the different components and concrete-steel relative slip. The FE model captured the different modes of failure for the continuous composite girder either in the concrete slab or at the interfacial region between CFRP sheet and concrete slab. Through a parametric study, the thickness of CFRP sheet and shear connection required to develop full capacity of the continuous composite girder at negative moment zone have been investigated. The FE results showed that the proper thickness of CFRP sheet at negative moment region is a function of the adhesive strength and the positive moment capacity of the composite section. The shear connection required at the negative moment zone depends on CFRP sheet's tensile stress level at ultimate load.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2436-2441
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• 2002

Finite element technique considering adhesive forces is proposed and applied to analyze the behavior of elastic hemispherical asperity adhesively contacting the plane surface of semi -infinite rigid body. It is demonstrated that the finite element model simulates interfacial phenomena such as jump -to-contact and adhesion hysteresis that cannot be simulated with the currently available adhesive contact continuum models. This simulation aiso provides valuable information on contact pressure, contact region and stress distributions. This technique is anticipated to be utilized in designing a low-adhesion surface profile for MEMS/NEMS applications since various contact geometries can be analyzed with this technique.

• Journal of Welding and Joining
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• 제16권4호
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• pp.109-116
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• 1998

The three-dimensional profile of a solder fillet is predicted by minimizing the surface tension and gravity energies of the solder joint using finite element modeling. Geometric complexity stemming from the inclined plane of the gullwing lead is resolved by employing three element types. These element types are used to describe the joint profile formed on the vertical, inclined and interfacial planes. The predicted solder joint profiles show good agreements with the experimental data provided that the solder volume is adjusted considering the wicking effects. Effects of the pad length, inclined lead angle and solder volume on joint profiles are also investigated.

• 대한전기학회논문지
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• 제36권11호
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• pp.777-782
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• 1987

A new composite method of finite element and boundary integral methods is presented to solve the two dimensional magnetostatic field problems with open boundary. The method can deal with the current source of the boundary integral regin where the boundary integral method is applied, and also Neumann and Dirichlet boundary conditions at the interfacial boundary between the boundary integral region and the finite element region where the finite element method is applied. The new approach has been applied to a simple linear problem to verify the usefulness. It is shown that the proposed algorithm gives more accurate results than the finite element methed under the same elementdiscretization.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1993년도 추계학술강연 및 발표대회강연 및 발표논문 초록집
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• pp.3-3
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• 1993

In mechanical testing of W-Ni-Pe heavy alloys, the cracks nucleate at W/W interface and propagate through W/ Imatrix interface or through matrix phase together with the cleavage of W grains. The mechanical properties can therefore be improved by control of the interfacial strength and area. In this presentation, some experimental result and techniques on this subject will be reviewed and discussed. The hydrogen embrittlement caused by the hydrogen segregation at interfaces during sintering in an hydrogen atmosphere can be removed by an heat-treattnent in vacuum or in an inert atmosphere. The heat-treatment condition can be estimated by using a diffusion equation for a cylindrical shape. The mechanical properties, in particular the impact property, are degraded by the segregation of non-metallic impurities, such as Sand P. The degradation can be prevented by adding a fourth element, such as La or Ca, active with the non-metallic impurities. The cyclic heat-treatment at usual heat-treattnent tempemture causes the penetration of matrix between W/W grain boundaries and results in remarkable increase in impact energy. This is due to an increase in the area of ductile failure during the impact test. The instability of W/matrix interface casued by addition of Mo or Re can be controlled by using W powders of different size. The increase in the interfacial area in found to be related to the presence of non-equilibrium pure W gmins among W(Mo or Re) solid solution gmins.

• Corrosion Science and Technology
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• 제12권4호
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• pp.171-178
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• 2013

In a polymer membrane fuel cell stack, the bipolar plate is a key element because it accounts for over 50% of total costs of the stack. In order to lower the cost of bipolar plates, 316L stainless steels coated with nitrides such as TiN and CrN by physical vapor deposition were investigated as alternative materials for the replacement of traditional brittle graphite bipolar-plates. For this purpose, interfacial contact resistances were measured and electrochemical corrosion tests were conducted. The results showed that although both TiN and CrN coatings decreased the interfacial contact resistances to less than $10m{\Omega}{\cdot}cm^2$, they did not significantly improve the corrosion resistance in simulated polymer electrolyte membrane fuel cell environments. A CrN coating on 316L stainless steel showed better corrosion resistance than a TiN coating did, indicating the possibility of using modified CrN coated metallic bipolar plates to replace graphite bipolar plates.

• Composites Research
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• 제16권1호
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• pp.42-49
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• 2003

취성기지 복합재료는 섬유와 기지 사이에 계면분리가 존재하는 경우가 있는데 이것은 복합재료의 강도와 강성저하의 원인이 된다. 계면분리와 섬유체적비가 복합재료의 기계적 물성치에 미치는 영향에 대만 유한요소해석을 수행하였다. 우선 몇 가지 가정하에 복합재료를 구성하는 섬유와 기지에 대하여 간단하게 모델링하고 이웃하는 대표체적요소의 경계를 따라 응력과 변위 연속조건을 부과하였다. 강성상수들을 역변환하여 복합재료의 유효물성치를 구하였다. 완전접착의 경우 수치해를 혼합물법칙에 의한 이론해와 비교한 결과 일치함을 알 수 있었고 계면분리가 큰 경우 섬유체적비가 증가하더라도 물성치가 감소함을 알 수 있었다.

• Advances in aircraft and spacecraft science
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• 제4권6호
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• pp.639-650
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• 2017

The objective of this paper is to obtain three-dimensional (3D) effective properties for layered composites with imperfect interfaces using mechanics of structure genome. The imperfect interface is modeled using linear traction-displacement model that allows small infinitesimal displacement jump across the interface. The predictions obtained from the current analysis are compared with the 3D finite element analysis (FEA). In this study, it is found that the present model shows excellent agreement with the results obtained using 3D FEA by employing periodic boundary conditions. The prediction also reveals that in-plane longitudinal and shear moduli, and all Poisson's ratios are observed to be not affected by the interfacial stiffness while the predictions of transverse longitudinal and shear moduli are significantly influenced by interfacial stiffness.

• International Journal of Aeronautical and Space Sciences
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• 제13권3호
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• pp.282-295
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• 2012

Fiber reinforced polymer matrix composites are widely used to provide protection against ballistic impact and blast events. There are several factors that govern the structural response and mechanical properties of a textile composite structure, of which the fiber-matrix interfacial behavior is a crucial determinant. This paper reviews the microbond or microdroplet test methodology that is used to characterize the fiber-matrix interfacial behavior, particularly the interface shear strength (IFSS). The various analytical, experimental, and numerical approaches applied to the microbond test are reviewed in detail.