• Proceedings of the KTCVS Conference
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• 1998.10a
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• pp.140-140
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• 1998

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.75-82
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• 1987

It is the objective of this study to estimate J-integral by numerical analysis, in which J-integral as aparameters in fracture mechanics can be used to evaluate unstable ductile fracture which is a important problem with respect to structural stability when the scope is beyond small scale yielding criteria. For this, 8-node isoparametric singular element as crack tip element of a cracked material was used to solve plastic blunting phenomenon at crack tip, and crack opening was forced to start when J-value was exceeding fracture toughness $J_{IC}$ of the material. And crack propagation behaviour was treated by using crack opening angle. From this study, it was shown that crack opening, stable propagation and unstable opening point of the cracked material found by using J-value obtained from this study were accord with the other study, so think, J-value obtained from this study can be directly used as a parameter in fracture mechanics to deal with the problem of stable propagation of crack and unstable ductile fracture.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.49-49
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• 2004

고도화로 정밀해진 현대 과학기기에는 여러 가지 전자 팩키징 제품들이 쓰이고 있으나 이 제품들은 여러 가지 파손인자들의 영향 때문에 고유의 수명을 다하지 못하고 고장이 발생하게 된다. 전자부품 실장에 이용되는 솔더 조인트의 열화에 관련되는 열 피로와 이온 마이그레이션(Migration) 현상이 솔더 조인트의 신뢰성에 영향을 미치는 가장 중요한 인자로 알려져 있고 이러한 인자 이외에도 여러 가지 요인들이 복합적으로 작용하여 솔더의 접합부분에 피로파괴를 일으킨다.(중략)

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.235-253
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• 2018

Groundwater flow induced by cracks in a buried pipe causes ground loss in the vicinity of it which can lead to underground cavities and sinkhole problems. In this study, the ground collapse mechanism and the failure mode based on an aperture in the pipe located in cohesionless ground were investigated through a series of physical model studies. As the influence parameters, size of the crack, flow velocity in the pipe, groundwater level, ground cover depth and ground composition were adopted in order to examine how each of the parameters affected the behavior of the ground collapse. Influence of every experimental condition was evaluated by the final shape of ground failure (failure mode) and the amount of ground loss. According to the results, the failure mode appeared to be a 'Y' shape which featured a discontinuous change of the angle of erosion when a groundwater level was equal to the height of the ground depth. While in the case of a water table getting higher than the level of ground cover depth, the shape of the failure mode turned to be a 'V' shape that had a constant erosion angle. As the height of the ground depth increased, it was revealed that a mechanism where a vertically collapsed area which consisted of a width proportional to the ground height and a constant length occurred was repeated.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.62-72
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• 2007

Fracture analysis of human bone is necessary to predict the failure of musculoskeletal structures and to heal them by several possible mechanisms under different loading conditions. But human bone is a complex material, with a multiphase, heterogeneous and anisotropic microstructure. Due to the difficulty of obtaining experimental and clinical results, the importance of numerical analysis and computational simulations in biomechanics are increasing gradually. In this study, stress analysis for human femur model is performed by using the 2-dimensional finite element method(FEM) and its stress distribution is determined. From these results, the fracture mechanic parameters are calculated and the fracture criteria on human femur are investigated and discussed.

• Journal of Welding and Joining
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• v.10 no.4
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• pp.44-57
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• 1992

본 보에서는 용접 구조물의 파괴 방지를 위한 제반 용접 구조 설계에 대하여 전반적으로 기술 하였다. 현대 용접 구조물의 각 선급이나 spec.에서 규정한 식들에 의해 산정된 정적하중으로 구조 설계되는 종래의 방법과는 달리, 유한 요소 구조 해석에 의한 강도 평가, 외부하중의 직접 계산에 의한 보다 정확한 설계 하중의 설정 및 통계적 처리를 통한 합리적인 구조해석(피로강도 포함)등으로 설계되고 있다. 더우기 구조설계시 구조물의 취성파괴를 고려한 파괴강도 및 인성 개념을 도입하였을 뿐 아니라 균열의 존재와 성장을 파괴 역학적으로 해석하여 구조물의 조업 중에서의 파괴관리 및 제어도 실시할 수 있는 총합적인 설계에 의하여 용접 구조물은 제작되고 있다. 비록 구조물의 총합적인 구조 설계로 제작되었을지라도, 구조물의 사용 성능은 용접부의 특성에 의하여 크게 변하게 되므로 용접 설계의 역할을 매우 중요하다. 용접 설계란 용접시공법, 구조부재 및 용접재료의 선정, 용접 이음부의 구조적 형상과 세부 형상 및 그외 용접에 관련된 제 인자들을 상호 유기적으로 조합함으로써 보다 경제적이고 신뢰성 있는 용접부를 얻고자 함에 그 목적이 있다.

• The Korean Journal of Zoology
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• v.38 no.1
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• pp.1-9
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• 1995

연두·금파리에서 혈구 세포가 면역반응의 일환으로 일으키는 결절형성(nodule formation) 현상을 형태학적으로 관찰하고자 본 실험이 수행되었다. 연두금파리 종령 유충 체내에 정상 효모, 고정된 대모, 세포액이 제거된 원형질체의 효모를 각각 주입하여 면역반응 과정을 전자현미경으로 관찰하였다 먼저 정상 효모를 주입하였을 경우, 효모와 접촉한 헐구의 과립방출과 곧 이은 혈구의 파괴 그리고 효모 주위에 혈림프와 함께 점액성응혈(clot)의 형성을 관찰 할 수 있었다 점액성 응혈에는 여러 유형의 파괴된 혈구가 포함되어 있었다. 이같은 면역반응에는 체내 혈구 중 과립혈구(granulocyte)가 가장 활발히 반응였고 응혈의 대부분을 형성하였다. 결절의 중심부인 응혈은 대모와 파괴되지 않은 혈구 대 파괴된 혈구 그리고 방출된 과립들로 차 있었고, 효모 주입 3시간 까지는 이같은 응혈은 계속 확대되었다. 그러나 10시간 이후에는 응혈이 관찰되지 않았으며 이때 체강내에서 효모가 관찰되곤 하였다. 고정된 효모를 주입하였을 경우에는 혈구파괴나 과립방출 등이 관찰되지 않았으며, 고정된 효모에 대한 혈구의 식 세포작용만이 관찰되었다. 이 식세포작용은 주입후 10시간 까지 계속되었다. 원형질 체의 효모를 주입하였을 경우에는 혈구에의한 면역반응이 관찰되지 않았다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.415-422
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• 2010

Development of the reliability-based design program in the GUI environment is inadequate for engineers familiar with the deterministic design to deal with the international design criterion based on the probabilistic design. In this study, the design program based on the GUI environment is developed in order to more efficiently input the design factor and more easily carry out the design works. The GUI environment is the GUIDE (Graphic User Interface Development Environment) tool supported by the latest MATALB version 7.1. In order to test the model reliability, the probabilities of failure (POF) on the breakwater armor block (AB) and gravity quay-wall (QW) in the sliding mode are computed using the model in the Level II and Level III. The POF are 55.4~55.7% for breakwater AB and 0.0006~0.0007% for gravity QW. A non-GUI environment program results of the POF are 55.6% for breakwater AB and 0.0018% for gravity QW. In comparison, the POF difference is negligible for breakwater AB because the exact input design parameters are available, whereas the large POF difference, but within the same order, for gravity QW can be explained by the difference of the input design factors because of the poor input data information.

• Journal of the Korean Geosynthetics Society
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• v.3 no.4
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• pp.13-19
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• 2004

This paper presents the results of an investigation on the failure mechanism of geosynthetic-reinforced segmental retaining walls in tiered arrangement using reduced-scale model tests. In this laboratory model tests, a reduced scale model of the full-scale geosynthetic-reinforced wall which was constructed in Geotechnical Experimental Site at Sungkyunkwan University was used to perform a study on the failure mechanism. In order to a high degree of realism, the geometry of the wall and the material properties were selected applying Similitude Laws was used to perform laboratory model tests. And contrary to the previous failure tests with various surcharge pressures, the failure by the tired wall weight was observed. Primary variables considered in the model tests include the different offset distance between the tiers and the different reinforcement length in the lower tier and as a result of the parametric study, a different failure pattern was observed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.1
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• pp.125-136
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• 1984

In the weled structures, fatigue fracture mainly depends upon crack growth behavior. Specially anisotropy of crack growth orientation and welding direction become important factor of fracture in the welding jone. When fatigue stressed steel welded with nonfatigue stressed steel, at the low stress intensity factor range, residual stress become more important factor of growth behavior then properties of base metal but when the crack growth in the weld metal, toughness of weld metal become the most important factor. Especially nonhomgeniety of toughness for the weld metal make more scatter the relations of $da/dN-{\Delta}K$.