by Yan, Cheng; Mai, Yiu-Wing

Large deformation finite element analysis has been carried out to investigate the stress-strain fields ahead of a growing crack for compact tension (a/W=0.5) and three-point bend (a/W=0.1 and 0.5) specimens under plane stress condition. The crack growth is controlled by the experimental J-integral resistance curves measured by Sun et al. The results indicate that the distributions of opening stress, equivalent stress and equivalent strain ahead of a growing crack are not sensitive to specimen geometry. For both stationary and growing cracks, similar distributions of opening stress and triaxiality can be found along the ligament. During stable crack growth, the crack- tip opening displacement (CTOD) resistance curve and the cohesive fracture energy in the fracture process zone are independent of specimen geometry and may be suitable criteria for characterizing stable crack growth in plane stress.

DOI: 10.1023/A:1007568804469
Print publication date: 5/1/1998
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by Selvarathinam, Alex S.; Weitsman, Y. Jack

Motivated by experimental observations, the finite element method is employed to model the competition between the transverse cracking and delamination modes of failure that occur in cross-ply AS4/3501-6 gr/ep coupons subjected to fatigue. The results explain the extensive delaminations and reduced crack densities that arise under immersed fatigue, as compared with fatigue in air.

DOI: 10.1023/A:1007572318272
Print publication date: 5/1/1998
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by Chen, Bi-Trong; Hu, C.T.; Lee, Sanboh

A comparison of elastic interaction of a dislocation and a crack for four bonding conditions of the crack plane was made. Four cases of single crystalline material, sliding grain boundary, perfectly bonded interface, and sliding interface were considered. The stress intensity factors arising from edge and screw dislocations and their image forces for the above four cases were compared. The stress intensity factor at a crack tip along the perfectly bonded interface arising from screw dislocation can be obtained from that in a single crystalline material if the shear modulus in the single crystalline material is replaced by the harmonic mean of both shear moduli in the bimaterial. The stress intensity factor at a crack tip along the sliding interface arising from edge dislocation in the bimaterial can be obtained from that along the sliding grain boundary in the single material if the μ/(1−ν) in the single material is substituted by the harmonic mean of μ/(1− ν) in the bimaterial where μ and ν are the shear modulus and Poisson’s ratio, respectively. The solutions of screw dislocation near a crack along the sliding grain boundary and sliding interface are the same as that of screw dislocation and its mirror image. Generally, the effect of edge dislocation for perfectly bonded interface on the crack propagation is more pronounced than that for the sliding interface. The effect of edge dislocation on the crack propagation is mixed mode for the cases of perfectly bonded interface and single crystalline material, but mode I fracture for the cases of sliding interface and sliding grain boundary. All curves of Fx versus distance r from the dislocation at interface to the right-hand crack tip are similar to one another regardless of dislocation source for both sliding interface and perfectly bonded interface. The level of Fx for m=0 is larger than that for m=−1.

DOI: 10.1023/A:1007533914501
Print publication date: 5/1/1998
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by Chen, Bi-Trong; Hu, C.T.; Lee, Sanboh

The edge dislocations near a cracked sliding interface were investigated. A continuous distribution of edge dislocations with Burgers vector along the y direction was used to simulate a crack of finite length along the sliding interface. From the dislocation distribution the stress field in the entire space was obtained. The stress intensity factors at both crack tips and image force on the edge dislocation were derived. The effects of the dislocation source and shear modulus ratio on both stress intensity factors and image force were also studied. Only mode I stress intensity factors at both tips were found in the composite materials with a sliding interface. The edge dislocations with Burgers vector along the y direction emitted from the crack always shield it to prevent propagation. The above results may reduce to an edge dislocation near a semi-infinite crack along a sliding interface including a sliding grain boundary.

DOI: 10.1023/A:1007529730431
Print publication date: 5/1/1998
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by Chen, Zeng-Tao; Karihaloo, B.L.; Yu, Shou-Wen

The problem of an anti-plane Griffith crack moving along the interface of dissimilar piezoelectric materials is solved by using the integral transform technique. It is shown from the result that the intensity factors of anti-plane stress and electric displacement are dependent on the speed of the Griffith crack as well as the material coefficients. When the two piezoelectric materials are identical, the present result will reduce to the result for the problem of an anti-plane moving Griffith crack in homogeneous piezoelectric materials.

DOI: 10.1023/A:1007479401141
Print publication date: 5/1/1998
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by Berger, J.R.; Martin, P.A.; Lien, J.P.

We investigate the free-edge stresses in anisotropic bimaterials through the use of the free-edge stress intensity factor, Kf. This requires a determination of the singularity order at the free-surface as well as a calculation of the near-field stresses. We determine the order of the singularity for arbitrary free-surface orientation of the upper material using an eigenvalue analysis for anisotropic bimaterials. The interfacial stresses are determined using a boundary element calculation based on anisotropic, bimaterial Green’s functions. The variation of Kf with free-surface orientation is determined. We find that the free-edge singularity vanishes for certain angles dependent on the anisotropic elastic constants.

DOI: 10.1023/A:1007426532324
Print publication date: 5/1/1998
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by Moon, H.J.; Earmme, Y.Y.

The relations between the J-based mutual integral and the T-stress are derived for in-plane and anti-plane problems, respectively. The mutual integral is shown to be evaluated without solving the boundary value problems. The T-stress, a useful parameter for crack stability, is thus obtained easily by a suitable application of the concept of the conservation integral. As an example to show this, the fundamental interface crack problems for an infinite dissimilar solid and two infinite strips are presented.

DOI: 10.1023/A:1007457720550
Print publication date: 5/1/1998
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