• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.113-113
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• 2004

실제 사용중인 기계나 기계구조물은 다양한 환경 및 복잡한 설계조건으로 인하여 변동하중과 다축에서 작용하는 혼합모드 하중 상태에 놓이는 경우가 대부분이다. 하지만, 순수 모드 I 하중상태 하에서의 연구는 활발히 이루어졌으나, 실제 구조물에서 대부분 발생하는 혼합모드 하중상태 하에서의 연구는 아직 부족한 실정이다. 또한 기계구조물내의 많은 성분요소에 존재하는 작용 하중 방향에 수직적이지 않게 되며, 초기균열의 균열선상에서 성장하지 않는다.(중략)

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.2
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• pp.43-49
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• 2005

The purpose of a fatigue crack arrest design is to prevent a fatigue fracture of machine and structure resulted from unstable crack growth. In all cases of load transfer to second elements such as stringers, doublers or flanges, crack arrest is possible; arrest occurring when the fatigue crack reaches the second element. In the present work, a numerical analysis was carried out to estimate the effect of shape parameters on fatigue crack growth and arrest behavior of integrally stiffened panels. Based on these results, a set of fatigue crack arrest design chart is presented as "non-dimensional arrest load - thickness ratio" relationship.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.160-167
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• 2012

This paper is concerned with a particular fracture mechanics parameter ${\Delta}K_{th}$, known as the 'threshold stress intensity range', or 'fatigue threshold'. This threshold ${\Delta}K_{th}$ constitutes, as it were, a hinge between the notion of crack initiation and the notion of crack growth. It has often been thought that, like the endurance limit, it could be an intrinsic criterion of the material. The study was conducted on a SA-508 pressure vessel steel used in the nuclear power industry. This material exhibits a typical threshold effect in the range of the crack growth rates which were determined; that is, below approximately $da/dN=10^{-6}mm/cycle$, the slope of the da./dN versus ${\Delta}K$ curve is almost vertical. The value of ${\Delta}K_{th}$ was determined at a growth rate of $10^{-7}$ mm/cycle according to the ASTM Standard for threshold testing. The fatigue threshold values are in the range 21 $kg/mm^{3/2}$ to 12 $kg/mm^{3/2}$ depending on the stress ratio effect.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.2
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• pp.50-56
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• 2005

To demonstrate the feasibility of utilizing FCAD chart proposed in our previous work, series of crack growth/arrest behavior in the integrally stiffened panels were simulated by numerical method using upper mentioned FCAD charts and a new crack growth rate equation. It is concluded that proposed family of FCAD curves, in the form of non-dimensional arrest load ranges, are reliable indicators of fatigue crack growth/arrest behavior of integrally stiffened panels considered here.

• Journal of Welding and Joining
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• v.13 no.2
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• pp.96-105
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• 1995

A modified method for the analysis of short fatigue crack growth has been presented, and calculations based upon the modified method are compared with experimental results for S45C carbon steel. It is also shown that the modified method is in good agreement with experimental data. The proposed equation for the fatigue crack growth rates includes a material constant which relates the threshold level to the endurance limit, a correction for elastic-plastic behaviour and a means for dealing with the effects of crack closure. In this study one of the modifications is to substitute the Forman' s elastic expression of the stress intensity factor range into the geometrical factor The other is a consideration of the bending effect which is developed from the moment caused by the eccentric cross sectional geometry as the crack grows. Thus, this method is useful for residual life prediction of the mechanical structures as well as the welding structures.