A triggering criterion is suggested to determine the instability of a dislocation source under Mode-I singular stresses. Two kinds of configurations are considered, including a crack and a wedge formed by climbing dislocations pileup. Numerical results are given and discussed for both the cases.

In present paper, the anti-plane problem of thermal effect near crack tipregion of piezoelectric material subjected to electrical impact loading is investigated by means of the integral transforms and the singular integral equations. By introducing the thermal power, the temperature field near crack tip is finally obtained on the basis of the hypotheses of the uncoupling between the thermal field and the electro-mechanical fields and the adiabatic approximation. The numerical results indicate that a high temperature field of small region near crack tip is deduced when high electrical impact load is applied. Moreover, the results show that the temperature field strongly depends on crack size. However, the thermal effect of mechanical impact comparing with electrical impact may almost be neglected.

Classical elastoplastic theory predicts that the rotation angle near an interface between two mismatched materials is discontinuous under shear. The strain gradient effects, however, can be significant within a narrow region near the interface. This can be shown by application of the strain gradient plasticity. The matching expansion method was used to obtain asymptotic results. Comparison is then made with those found numerically for the interface torsion problem of a two-layered cylindrical tube. The strain gradient plasticity theory solution differs from that of the classical elas-toplastic theory solution, depending on the properties aside from the interface behavior and the loading mode. A failure criterion is also proposed that accounts for the strain gradients.

The scattering problem of a plane elastic wave by an interface crack between a piezoelectric layer and an elastic substrate is analyzed by means of the integral transform and the Cauchy singular integral equation methods. The effects of the crack configuration, the incident direction of the wave and the material combinations are examined.