• Composites Research
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• v.13 no.4
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• pp.67-74
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• 2000

The general solution of the anti-plane shear problem for the curved interfacial crack between viscoelastic foam and composites was investigated with the complex variable displacement function. Kelvin-Maxwell three parameter model is used to present viscoelasticity and the Laplace transform was applied to treat the viscoelastic characteristics of foam in the analysis. The stress intensity factor near the interfacial crack tip was predicted by considering both anisotropic and viscoelastic properties of two different materials. The results showed that the stress intensity factor increased with increasing the curvature of the curved interfacial crack and it also increased and eventually converged to a specific value with increasing time. The stress intensity factor increased with increasing the ratio of stiffness coefficients between foam and composites and the effect of fiber orientation on the stress intensity factor decreased with increasing the ratio of stiffness coefficients between foam and composites.

• Nuclear Engineering and Technology
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• v.23 no.1
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• pp.12-19
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• 1991

An engineering approach for estimating the stress intensity factors of a semi-elliptical crack is presented. An approximate 2-dimensional approach solution for semi-elliptical crack is derived in terms of simple equation, through weight function technique, by reflecting on the physical character of cracks.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.36-43
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• 1987

Stress intensity factors are computed by the boundary element method employing the multiregion technique along with the double-point concept. To demonstrate the validity of the current method, the stress intensity factors of the well-known simple models such as a slanted edge crack and an arcular crack are determined, in advanced, which are proved to be in good agreement within 5% with the pre-existing solutions. Z-shaped cracks are analyzed with various branch crack lengths and branching angles.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.130-137
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• 1990

Thermal shock stress intensity factor for an edge-cracked plate subjected to thermal shock is obtained from Bueckner's weight function method. It is shown that thermal shock stress intensity factor has maximum values with variation of time and crack length and that there is most dangerous crack length. By comparing thermal shock stress intensity factor with fracture toughness, the fracture time and critical temperature difference due to thermal shock are determined theoretically. Under constant thermal shock temperature difference, and increase of crack length is shown to increase fracture time. The theoretical fracture time is compared with experimental value measured by acoustic emission method with soda lime glass.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.463-474
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• 1995

Modified Vainshtok weight function method is developed. The thermal shock stress intensity factors for elliptical surface cracks existed in the thin and thick walled cylinders are determined. The present results are compared with previous solutions and shown to be good agreement with them.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.119-129
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• 1990

In case that the body with a cusp crack is under uniform heat flow, thermal stress intensity factors are calculated by using boundary element method with linearized body force term. The crack surface is under insulated or fixed temperature condition and the types of crack are symmetric lip and airfoil cusps. Numerical values of thermal stress intensity factors for a Griffith crack and cusp cracks in infinite bodies are proved to be in good agreement within .+-.5% when compared with the previous numerical and exact solutions, respectively. The thermal stress intensity factors for symmetric lip and airfoil cusp cracks in finite bodies are calculated about various effective crack lengths, configuration parameters, and heat flow directions. With the same crack surface thermal boundary conditions, heat flow directions and crack lengths, there are no appreciable differences in variations of thermal stress intensity factors between symmetric lip and airfoil cusp cracks. The signs of thermal stress intensity factors for each cusp crack are changed with each crack surface thermal boundary condition.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1700-1710
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• 1992

The boundary element method is applied to determine thermal stress intensity factors for a cusp crack in transient state. In the steady temperature field, numerical values of thermal stress intensity factors for a Grifith crack and a symmetric lip cusp crack in a finite body are in good agreement within .+-. 5% with the previous solutions. In transient state, the numerical values of thermal stress intensity factors for the Griffith crack are also in good agreement with the pervious solutions. In both steady and transient states, those for the symmetric lip cusp crack with the crack surface insulated or fixed to the constant temperature are calculates for various effective crack lengths, configuration parameters and uniform heat flow angles. The variations of the thermal boundary conditions of the crack surface have a effect on stress intensity factors. The signs on the values of thermal stress intensity factors can be changed in time variation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.680-683
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• 1998

In case of the infinite body containing a rigid inclusion with line crack shape, stress intensity factor is determined and the relation between stress intensity factor and stress distribution near a crack tip is developed. Also, the relation between stress intensity factor and Kolosoff stress function is developed. Finally, these results are compared with those that the crack surface is under no traction.

• Journal of Welding and Joining
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• v.15 no.1
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• pp.55-65
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• 1997

The stress intensity factor has been calculated for the cracked plate subjected to remote normal stress and reinforced with a plate by symmetric spot welding. The solution was based on displacement compatibility condition between the cracked sheet and the reinforcement plate. It is shown that the results from the derived equation for stress intensity factor were agreed with previous solutions. The reinforcement effect gets better as a joining spot is closer to the crack tip and the other joining spots become nearer to the crack surface.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.901-909
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• 1996

A model is constructed to evaluate the stress intensity factors(SIFs) for composites with an interlaminar crack subjected to as arbitrary crack surface loading. A mixed boundary value problem is formulated by Fourier integral transform method and a Fredholm integral equation of the second kind is derived. The integral equation is solved numerically and the mode I and II SIFs are evaluated for various shear modulus ratios between each layer, crack length to layer thickness, each term of crack surface polynomial loading and the number of layers. The mode I and II SIFs for the E- glass/epoxy composites as well as the hybrid composites are also evaluated.