• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.1
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• pp.75-82
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• 1999

일반 해양 구조물이나 해저면에 설치되는 해저 관로는 외력에 의한 변형이 발생된다. 구조물 형상이 복잡하거나, 구성 요소의 개수가 많을 경우 응력해석 시 많은 초기값이 필요하고 해석 시간 또는 장 시간 소요된다. 해양 구조물에 작용하는 대표적인 외력은 파도, 조류, 바람이고 이런 외력은 구조물의 사용 기간(operation life)동안 계속적으로 작용하기 때문에 구조물의 변형율은 항상 허용치 안에서 발생되도록 설계되어야 한다. 허용 변형은 탄성범위 내에 존재해야 하며, 비교적 큰 변형을 일으키는 구조물이나 해저파이프라인의 응력해석을 수치적으로 접근하는 방법을 고찰하였다. 평행상태의 하중 벡터값만 직각 좌표계에서 인트린직(intrinsic) 좌료로 변환시킬 때 변형이 발생함으로, 본 논문에서 소개하는 이차 요소(quadratic element)방법을 사용할 경우 수치해석 시 많은 장점이 있다는 것을 보여준다. 본 방법을 도입함으로써 비교적 큰 변형이 발생되는 구조물 해석 시 일반 수치해석 방법과 그 결과는 같으나 해석 시간을 단축시킬 수 있다는 장점이 있다. 응력 해석 시 국부 강도 행열(element stiffness matrix)은 방향과 무관하며 이차요소 방법을 사용하여 각 요소 벡터를 발생시켰다. 해저관로 일점 상승 시 관로에 작용하는 변형과 상승력에 따른 휨 모멘트를 산출하여 일반적으로 사용되는 선형이론과 비교하였다.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.726-733
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• 2002

Shrinkage strip or separation strip is a temporary joint that is left open for a certain time during construction to allow a significant part of the shrinkage to take place without inducing stress. A shrinkage stress analysis method of shrinkage strip in concrete slab of multi-story building considering the relaxation effect of creep and construction sequence is proposed. The analysis results of 10-story example building show that the effect of shrinkage strip can be analyzed easily by the proposed method. And shrinkage strip installed in a particular floor makes the stress of that floor reduced and the stress of the other floors increased a little. The rate and amount of stress reduced with closing time mainly depends on the development of shrinkage with time of concrete model used. The amount of stress reduced is determined by the amount of shrinkage strain developed before the closing of shrinkage strip.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1054-1064
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• 2009

In this work, we predict a true fracture strain using load-displacement curves from tensile test and finite element analysis (FEA), and suggest a method for acquiring true stress-strain (SS) curves by predicted fracture strain. We first derived the true SS curve up to necking point from load-displacement curve. As the beginning, the posterior necking part of true SS curve is linearly extrapolated with the slope at necking point. The whole SS curve is then adopted for FE simulation of tensile test. The Bridgman factor or suitable plate correction factors are applied to pre and post FEA. In the load-true strain curve from FEA, the true fracture strain is determined as the matching point to test fracture load. The determined true strain is validated by comparing with test fracture strain. Finally, we complete the true SS curve by combining the prior necking part and linear part, the latter of which connects necking and predicted fracture points.

• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.243-251
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• 2005

The fracture mechanics analysis of a crack in a weld must consider residual stress generated during welding. The standard definition of the J-integral requires a path dependent value in the presence of a residual stress field. Therefore, it is necessary to develop a path independent J-integral definition for a crack in a residual stress field. This paper addresses the modification of the Rice-J-integral to produce a path- independent J-integral when residual stresses and external forces are present. The residual stress problem is treated as an initial strain problem and the J-integral proposed for this type of problems is used. A program which can evaluate the J-integral for a crack in a weld is developed using the proposed J-integral definition. The situation when only residual stress is present is examined as is the case when mechanical stresses are applied in conjunction with a residual stress.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.149-156
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• 2011

In this paper, a methodology is proposed to improve the stress prediction of plates via Saint Venant's principle. According to Saint Venant's principle, the stress resultants can be used to describe linear elastic problems. Many engineering problems have been analyzed by Euler-Bernoulli beam(E-B) and/or Kirchhoff-Love(K-L) plate models. These models are asymptotically correct, and therefore, their accuracy is mathematically guaranteed for thin plates or slender beams. By post-processing their solutions, one can improve the stresses and displacements via Saint Venant's principle. The improved in-plane and out-of-plane displacements are obtained by adding the perturbed deflection and integrating the transverse shear strains. The perturbed deflection is calculated by applying the equivalence of stress resultants before and after post-processing(or Saint Venant's principle). Accuracy and efficiency of the proposed methodology is verified by comparing the solutions obtained with the elasticity solutions for orthotropic beams.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.4
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• pp.23-33
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• 1999

A finite element method was employed fort thermal and stress analyses of an IGBT module of 3-phase full bridge. The effect of material parameters such as substrate material, substrate area, solder thickness on the temperature and stress distributions of the module packages has been investigated. Thermal analysis results have also been compared by setting of boundary conditions such as equivalent heat transfer coefficient or constant temperature at a base metal surface of the package. The increase of ceramic substrate area up to 3 times does little contribution to the reduction(8.9%) of thermal resistance, while contributed a lot to the reduction(60%) of thermal stress. Thicker solder resulted in higher thermal resistance but did slightly reduced thermal stresses. It is revealed by the stress analysis that maximum stress was induced at the region of copper pads which are bonded with ceramic substrate.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.436-436
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• 2004

사용후 연료 건식 저장 용기가 낙하, 토네이도, 미사일, 홍수 및 지진으로 인한 사고에 대하여 전복이 발생되었을 때 강체 평면과 충돌에 의한 충돌 하중시의 구조 응력 평가하였다. 이를 위해 저장 용기의 무게 중심이 한계를 넘었을 때의 초기 전복 시작각을 무게 중심을 계산을 통해 구하였다. 상용 코드를 사용하여 전복 응력 해석 수행시 저장 용기의 강체 운동에 의하여 계산 시간이 길어지는 데, 이런 계산 시간을 줄이기 위해 일차 충돌 직전까지의 모델의 속도와 각속도 계산식을 이론적인 방법으로 구하여 해석 초기 조건으로 사용하는 방법에 대하여 제안하였다.(중략)

• Tunnel and Underground Space
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• v.5 no.3
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• pp.230-239
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• 1995

암석의 인장강도 실험법의 하나로써 새롭게 개발된 Hoop Test에 대한 이론적 뒷받침을 하고자 유한요소법을 사용하여 응력분포를 해석하였다. 간단하며 사용하기 편리한 실험장치이지만 시료가공시 생길 수 있는 내부공의 지름에 대한 오차, 재부공벽면과 하중장치외벽과의 마찰 등이 있어 이들로부터 발생할 오차를 평가해 보았다. 또한 시료의 안지름과 바깥지름의 비율이 응력의 크기에 끼치는 영향을 조사하였다. 응력해석결과, 일반적인 시료준바에 필요한 주의만 기울이면 실험치에 별다른 영향을 주지않는 것으로 제안되었고 이는 그동안의 실험결과의 신뢰성을 이론적으로 보충해 주었다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.370-376
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• 1997

A Simplified Finite Element Method(FEM) model has been developed for the Exhaust System. For the verification of the usage of the developed model , Natural Frequencies, Mode Shapes and Frequency Response Function have been compared between numerical analysis and experimental result. It shows that the developed numerical model also can be utilized to prove the Stress distribution of the Exhaust System if it can be adopted for the vibration analysis adequately.

• Journal of KSNVE
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• v.9 no.2
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• pp.295-301
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• 1999

A Simplified Finite Element Method(FEM) model has been developed for the Exhaust System. For the verification of the usage of the developed model. Natural Frequencies, Mode Shapes and Frequency Response Function have been compared between numerical analysis and experimental result. It shows that the developed numerical model also can be utilized to prove the Stress distribution of the Exhaust System if it can be adopted for the vibration analysis adequately.