• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.854-858
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• 2002

In this study, Fatigue crack growth behavior of the laser welded sheet metal due to a single overload was investigated. From Fatigue crack propagation test, it was observed that the retardation of fatigue crack growth has been more effective in the welded specimen than in the base metal. And if the distance between the welded part and the position of overload is too close the retardation of fatigue crack growth at the welded part has been decreased. From FEM analysis, it was observed the retardation has been more effective compressive residual stress than plastic zone.

• Membrane Journal
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• v.22 no.6
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• pp.435-440
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• 2012

In this study, nanoporous HKUST-1 membranes were synthesized by solvothermal method. It is very difficult to prepare uniform and crack-free HKUST-1 layer on macroporous alumina support by in-situ solvothermal method. In this study, continuous and crack-free HKUST-1 membranes could be obtained by spraying solvothermal precursor solution on the heated alumina support, followed by solvothermal synthesis. HKUST-1 membranes were characterized by XRD, FE-SEM and single gas permeation experiments.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.28-34
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• 2004

It is well known that tensile peak overloads may significantly delay suubsequent constant amplitude fatigue crack growth in many materials. Since real structures are usually subjected to complex load histories, the ability to predict accurate crack growth under realistic service conditions is of major engineering interest. This paper describes experiments on fatigue track growth in the integrally stiffened panel of 7075-T6 aluminum alloy. The effect of shape parameters and overload position on the fatigue crack growth behavior of integrally stiffened panels are discussed. Based on the experimental results, the following conclusions have been drawn: the overall fatigue crack growth retardation resulting from single overload in the stiffened panels was generally larger in the larger thickness ratio, although the retardation trends, according to the change in overload positions, were similar to those exhibited in the non-stiffened panels.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.75-86
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• 1996

A fatigue life prediction program for multiple planar surface cracks in finite plates and T-fillet joints, based on linear elastic fracture mechanics was developed. This prediction technique include the crack coalescence, mutual interation and the stress intensity concentration effect in welded joints. Total of 44 cases were compared with lida's and Vosikovsky's experimental results and it was found that the present method was a reasonable tool for the predictioin of fatigue life.

• Journal of the KSME
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• v.32 no.1
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• pp.4-17
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• 1992

이 글에서는 복합적층판의 역학적 특성인 층간분리, 모재균열, 초기파손 후의 거동에 대한 문헌을 간단히 서술하고 그 특성을 살펴 보았다. 이상에서 살펴본 바와 같이 이방성인 층으로 구성된 복합적층 구조의 역학적 특성은 균질인 단일구조와 달리 각층의 재료상수가 달라층과 층 사이의 층간응력이 존재하여 층간분리현상이 발생하지 않도록 섬유방향뿐만 아니라 적층순서를 중요한 설계변수로 고려하여야 한다. 또한 모재균열로 인한 기계적 거동의 변화를 이해하고 초기파손 후의 손상을 고려한 해석을 수행하여 복합적층 구조의 응력해석 및 파손, 강도예측을 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.115-116
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• 2010

• Journal of the Korean GEO-environmental Society
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• v.10 no.4
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• pp.65-71
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• 2009

Hydraulic fracturing technology has been widely applied in the industry for the recovery of the natural resources such as gas, oil and geothermal heat from hot dry rock. During hydraulic fracturing stimulation, multiple cracks are created resulting in mechanical interaction between cracks. Such an interaction influences obtaining hydraulic fracturing key parameters (crack opening, length, and borehole net pressure). The boundary collocation method (BCM) has been proved to be very effective in considering mechanical interaction. However, for better confidence, it needs to be verified by comparison with analytical solutions such as stress intensity factors. In this paper, three cases, single fracture in remote uniaxial tension, single fracture in remote shear stress field and two arbitrary segments in an infinite plane loaded at infinity are considered. As a result, the BCM is proved to be valid technique to consider mechanical interaction between cracks and can be used to estimate the hydraulic fracturing parameters such as opening of the fracture, and so on.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.413-419
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• 2002

Particulate composites of $Al_2O_3$/TiC/SiC, $Al_2O_3$/TiC and $Al_2O_3$/SiC have been fabricated by hot pressing and their R-curve behaviors and mechanical properties were investigated. $Al_2O_3$ containing 30 vol% TiC particles showed higher toughness by 8% than that for monolithic alumina and its fracture strength was increased significantly by approximately 30%. On the other hand, the addition of 30 vol% SiC of $3{\mu}m$ in $Al_2O_3$ decreased the fracture strength slightly but induced a rising R-curve behavior owing to the strong crack bridging of SiC particles. In case of $Al_2O_3$/TiC/SiC, arising R-curve behavior was also observed and the fracture toughness reached 6.6 MPa${\cdot}\sqrt{m}$ at the crack length of $1000{\mu}m$, which was lower than that of $Al_2O_3$/SiC, however, while the fracture strength was higher by about 20%. The fracture toughness seemed to be decreased as smaller TiC particles roughened the SiC interface and pullout of the SiC particles for crack bridging became less active.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.5
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• pp.356-361
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• 2014

The eddy current testing performance directly affects the results of a steam generator tube integrity assessment because the integrity assessment of defected tubes is conducted based on eddy current testing results. This means that it may not be possible to accurately discriminate between adjacent flaws. This paper presents an investigation on the resolution of rotating pancake coils with multiple cracks and the effects on the structural integrity assessment of steam generator tubes.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.93-100
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• 2005

The occurrence of multi-segmented hydraulic fractures that show different behavior from the single fracture is common phenomenon. However, it is not easy to evaluate the behavior of multiple fractures computed by most numerical techniques because of complicated process computation. This study presents how to efficiently calculate the displacement of the multi-segmented hydraulic fractures using the boundary collocation method (BCM). First of all, asymptotic solutions are obtained for the closely spaced overlapping fractures and are compared with those by the BCM where the number of collocation points is varied. As a result, the BCM provides an excellent agreement with the asymptotic solutions even when the number of collocation points is reduced ten times as many as that of conventional implementations. Accordingly, the numerical simulation of more realistic and, hence, more complex fracture geometries by the BCM would be valid with such a significant reduction of the number of collocation points.