• Proceedings of the KSME Conference
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• 2001.11a
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• pp.299-303
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• 2001

Adherend-adhesive interface failure will occur on a macroscale when surface preparation or material quality are poor. It is well known that the stress singularity occurs at the edges of interface between the adhernds and the adhesive, and that crack will initiate from these positions. Also if bubbles are created and remained in the adhesive layer during the bonding process, the stress concentrates around these hole defects. In this paper, the effects of the hole defects on the SIF of interface crack were examined. From results, SIF increased with the hole defects near the interface crack and increased with an decreae in the upper adherend thickness, an increase in the center adhesive thickness.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.2
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• pp.101-108
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• 2021

To date, a number of stress intensity factor (SIF) solutions have been proposed for the cylindrical structure with circumferential through-wall cracks. However, each solution has a different format as well as applicable range. It is also known that there is a significant difference in predicted SIF values depending on the shape of the structure and the size of the crack. In this study, the applicability of various SIF solutions was analyzed by comparing the finite element analysis results for the case where a tensile load is applied to the cylindrical structure with circumferential through-wall crack. It is found that the calculated SIF gradually decreases and converges to a certain value with increasing length-to-radius ratio. Therefore, an appropriate length-to-radius ratio should be set in consideration of the dimensions of the actual cylindrical structure. For piping with sufficiently long cylinder, the ASME solution is found to be the most appropriate, and for a short cylinder, the API solution should be applied. On the other hand, the WEC solution requires careful attention to its application.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.48-53
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• 2004

This paper suggested the method determing the stress intensity factor (SIF) for functionally gradient materials (FGMs) by photo elastic experimental method. The SIF for the center crack in a finite rectangulat plate with a linear variation of shear modulus with constant density and Poisson's ratio along the direction of the crack under mode I static loading is obtained. The exponential and linear variation of stress fields are used for obtaining the SIF. The greater crack length, the increaser the difference of the SIF between right and left side crack tip.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.4 s.23
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• pp.136-145
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• 2005

특이응력해석을 위한 일반화된 가역상반일 경계적분식이 섬유강화복합재를 모형화한 직교 이방성 크랙평판의 수치해를 위하여 발전시켰다. 이 적분방정식은 평판경계에서의 탄성변위와 트랙션의 변수로 구성된 경계적분식의 형태로 하중이 없다는 두 크랙면의 경계조건과 유한의 탄성변형에너지의 개념에서 경계적분식에 필요한 특성해를 규정하고 대응되는 보조해를 계산하였다. 대칭모우드 I형의 중앙원공크랙평판 및 복합모우드형의 반원편측크랙 일단고정평판의 응력확대계수가 임의의 섬유방향각에 따라서 계산되었다.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.36-48
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• 2021

As the material aging of nuclear power plants has been progressing in domestic and overseas, crack growth becomes one of the most important issues. In this respect, the crack growth assessment has been considered an essential part of structural integrity. The crack growth assessment for nuclear power plants has been generally performed based on ASME B&PV Code, Sec. XI but the idealization of crack shape and the conservative solutions of stress intensity factor (SIF) are used. Although finite element analysis (FEA) based on iterative crack growth analysis is considered as an alternative method to simulate crack growth, there are yet no guidelines to model the crack-tip spider-web mesh for such analysis. In this study, effects of various meshing factors on FE SIF calculation are systematically examined. Based on FEA results, proper criteria for spider-web mesh in crack-tip are suggested. The validation of SIF calculation method through mapping initial stress field is investigated to consider initial residual stress on crack growth. The iterative crack-tip modeling program to simulate crack growth is developed using the proposed criteria for spider-web mesh design. The SIF results from the developed program are validated by comparing with those from technical reports of other institutes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.579-580
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• 2008

• Computational Structural Engineering
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• v.9 no.4
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• pp.189-198
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• 1996

The fracture behaviour of concrete gravity dam mainly due to uplift pressure acting at the crack face was studied. Triangular type and parabolic type distribution of the uplift pressure including uniform type were first considered in case of calculating stress intensity factor(SIF) by the surface integral method. Second, the directions of crack propagation according to the uplift pressure distribution were pursued by FRANC(FRacture ANalysis Code). Third, critical crack lengths according to the uplift pressure distribution under the overflow depth were calculated. The SIF values obtained from the surface integral method were compared with those by FRANC and relatively good agrements could be obtained between both of them. And it could be seen that the direction of crack propagation in case of triangular pressure distribution was a little benter to the dam base than the one by the uniform type. Maximum critical crack lengths under the overflow depth were obtained at about 2/5-1/2 of the dam height.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.6
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• pp.84-90
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• 2004

For the precise assessment of the effect of welding residual stresses on structural strength and fatigue crack growth behavior, new FE analysis algorithms for the estimation of residual stress relaxation due to external load and redistribution due to fatigue crack propagation were proposed in this paper. Initial welding residual stress field was obtained by thermal elasto-plastic analysis considering temperature dependent material properties, and the amount of residual stress relaxation and redistribution were assessed by subsequent elasto-plastic analysis In the analysis of fatigue crack propagation, the applied SIF(Stress Intensity Factor) range was evaluated by $\frac{1}{4}$-point displacement extrapolation method, and the effect of welding residual stresses on crack propagation was considered by introducing the effective SIF concept. The test results of crack propagations were compared with the predicted data obtained by the analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.727-730
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• 2001

In many structures a common method of construction is to make use of bolted or riveted joints. With this type of joint the load is transmitted through a pin from one section of the structure to another. Fatigue cracks often start from the edges of holes, due to local stress concentration. In order to predict the fatigue crack growth, the stress intensity factor K for hole-edge cracks should be available. In this paper the stress intensity factors are computed for cracks in bolt-joint region considering the contact condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.560-566
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• 2000

Many researchers have dealt with the problems of fracture mechanics. Generally, these researches are concerned with crack in isotropic material without other micro defects. Actual structure, however, may contain micro defects as well as crack in manufacture processing or operation. If it contains mi defects near a crack, some different characteristics will be appear in fracture behaviors of the crack. This study examines the effect of the micro defect on stress intensity factor of center slant crack rectangular plate subjected to uniform uniaxial tensile stress. In this study, boundary element method(BEM) is used for analysis in stress intensity factor(SIF).