• 대한기계학회논문집A
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• 제24권8호
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• pp.2007-2014
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• 2000

It has been reported that the dynamic stress intensity factor for a propagating crack is increasing or decreasing according to the increasement of the crack propagating velocity. It is confirmed in this study that the increasement or decreasement of stress intensity factor with crack growing velocity is accused by loading condition. When the crack propagates under a constant displacement along upper and lower boundary in finite plate, the dynamic stress intensity factor decreases according to the increasement of the propagating crack velocity. When the crack propagates under a constant stress along upper and lower boundary in finite plate, the dynamic stress intensity factor increases according to the increasement of the propagating crack velocity. The increasement or decreasement of stress intensity factor with crack growing velocity is greater in a fast crack propagation velocity than in a slow one.

• 대한기계학회논문집
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• 제17권7호
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• pp.1794-1804
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• 1993

The thermal stress intensity factors for interface cracks of Griffith and symmetric lip cusp types under vertical uniform heat flow in a finite body are calculated by boundary element method. The boundary conditions on the crack surfaces are insulated or fixed to constant temperature. The relationship between the stress intensity factors and the displacements on the nodal point of a crack tip element is derived. The numerical values of the thermal stress intensity factors for interface Griffith crack in an infinite body and for symmetric lip cusp crack in a finite and homogeneous body are compared with the previous solutions. The thermal stress intensity factors for symmetric lip cusp interface crack in a finite body are calculated with respect to various effective crack lengths, configuration parameters, material property ratios and the thermal boundary conditions on the crack surfaces. Under the same outer boundary conditions, there are no appreciable differences in the distribution of thermal stress intensity factors with respect to each material properties. But the effect of crack surface thermal boundary conditions on the thermal stress intensity factors is considerable.

• 대한기계학회논문집
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• 제19권5호
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• pp.1229-1242
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• 1995

The thermal shock stress intensity factors of semi-elliptical surface crack in finite plate and the stress intensity fractors of embedded elliptical crack in turbine rotor is determined by means of Vainshtok weight function method. In case of semi-elliptical surface crack, the solution is compared with previous solution. The stress intensity factor for embedded elliptical crack in turbine rotor loaded by centrifugal and thermal loading is also determined. In this case, the value of stress intensity factor is larger at crack contour near internal radius surface and is almost constant at the crack contour farther from internal radius surface.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 추계학술대회 논문
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• pp.194-197
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• 1996

The high-strength aluminum alloy 7075-T651 was used to observe the fatigue-crack-propagation behavior for the various stress ratios with constant amplitude loading and thus to predict the fatigue life. With a chevron notch in the specimen the fatigue-crack-propagation behavior of through crack was investigated. Crack propagation behavior of through crack in the depth direction and crack growth of weldments were experimentally studied. Base material heat affected zone and weld material were considered in the fracture of weldments. The change of crack-propagation length with respect to several parameters such as stress intensity factor range(ΔK) effective stress intensity factor range(ΔKeff)ration of effective stress intensity factor range(U) stress intensity factor of crack opening point(K op) maximum stress intensity factor(K max) and number of cycles(Nf)was determined. The crack length of through crack of weldments was 2.4mm and the remaining part was a base material. The experiment was accomplished by making the crack propagate near the base material.

• Tribology and Lubricants
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• 제16권5호
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• pp.373-380
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• 2000

Finite element analysis is performed on the subsurface crack propagation in brittle materials due to sliding contact. The sliding contact is simulated by a rigid asperity moving across the surface of an elastic half-surface containing single and multiple cracks. The single crack, coplanar cracks and parallel cracks are modeled to investigate the interaction effects on the crack growth in contact fatigue. The crack location is fixed and the friction coefficients between asperity and half-space are varied to analyze the effect of surface friction on stress intensity factor for horizontal cracks. The crack propagation direction is predicted based on the maximum range of shear and tensile stress intensity factors. With a coplanar crack, the stress intensity factor was increased. However, with a parallel crack, the stress intensity factor was decreased. These results indicate that the interaction of a coplanar crack increases fatigue crack propagation, whereas that of a parallel crack decreases it.

• 대한기계학회논문집
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• 제16권7호
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• pp.1255-1265
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• 1992

본 연구에서는 단열 및 온도가 영으로 고정된 경계조건을 갖는 대칭 입술형과 대칭 익형 강체함유 물상의 접합경계면 균열에 대한 Hilbert 문제로부터 복소 포텐셜 함수와 커스프 균열선단 그리고 접합경계면 균열선단에서 TSIF를 구하고자 한다.

• 대한기계학회논문집
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• 제14권1호
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• pp.119-129
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• 1990

본 연구에서는 선적분화 된 체적력항을 갖는 경계요소법을 이용하여, Griffi- th균열에 대한 열응력세기계수를 구하여 Sumi의 결과와 비교 검토하고, 유무한체내의 대칭 입술형및 대칭 익형 커스프균열들(symmetric lip and airfoil cusp cracks)의 열 응력세기계수를 균열묘면이 단열된 경우와 일정 온도로 유지된 경우에 대해 계산하고 자 한다.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1659-1664
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• 2003

A cracked plate with a patch bonded on one side was treated with a crack-bridging model using weight function: assuming continuous distribution of springs acting between th crack surfaces, the stress intensity factor of the patched crack was numerically obtained. Especially in the case of a patched crack subjected to residual non-uniform stress, the stress intensity factor was easily with the corresponding approximate weight function. This paper presented the stress intensity factors for a crack partially patched within a finite plate or a patched crack initiated from a notch.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.297-302
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• 1999

Finite element analysis is peformed about the crack propagation in half-space due to sliding contact. The analysis is based on linear elastic fracture mechanics and stress intensity factor concept. The crack location is fixed and the friction coefficient between asperity and half-space is varied to analyze the effect of surface friction on stress Intensity factor for horizontal crack. The crack propagation direction is predicted based on the maximum range of shear and tensile stress intensity factor.

• Structural Engineering and Mechanics
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• 제30권3호
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• pp.317-330
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• 2008

Stress intensity factors for a planar crack parallel to a bimaterial interface are considered. The formulation leads to a system of hypersingular integral equations whose unknowns are three modes of crack opening displacements. In the numerical analysis, the unknown displacement discontinuities are approximated by the products of the fundamental density functions and polynomials. The numerical results show that the present method yields smooth variations of stress intensity factors along the crack front accurately. The mixed mode stress intensity factors are indicated in tables and figures with varying the shape of crack, distance from the interface, and elastic constants. It is found that the maximum stress intensity factors normalized by root area are always insensitive to the crack aspect ratio. They are given in a form of formula useful for engineering applications.