The micro-scale adhesive contact behavior of a spherical rigid punch on a piezoelectric half-space is investigated in this paper. The governing equations describing the adhesive contact behavior are obtained by using the Maugis-Dugdale (M-D) elastic adhesive contact theory [J. Colloid Interface Sci. 150 (1992) 243]. The solutions for indentation of piezoelectric materials and for elastic adhesive contact can be reduced from the present results in the absence of adhesion effect and piezoelectric effect, respectively. The effect of the electric load on the adhesive contact behavior is analyzed. It is shown that the piezoelectric effect has a significant effect on the adhesive contact behavior of piezoelectric materials. The obtained results will be helpful to understand the micro-indentation properties of piezoelectric materials.

A micromechanics model is presented for estimating the effective thermoelastic properties of layered media. The continuity condition across a perfectly bonded interface between two dissimilar materials is introduced by decomposing the stress and strain tensors into two orthogonal complementary parts, an interior part and an exterior part that are tangential and normal to the interface, respectively. This model follows from the fact that the exterior part of the stress tensor and the interior part of the strain tensor are each continuous across the perfect interface. Thereby, the interaction between different phases of composites is accounted for. The exact expressions for the effective thermoelastic properties of layered media are derived, and the connections between the present scheme and some conventional micromechanics models are examined.

Some closed-form equations for the coupling problem of buckling and growth of circular delamination are derived by recourse to the moving boundary variational principle The axisymmetric buckling of a circular delamination subjected to an equal bi-axial compression is analysed by using high-order perturbation expansion The axisymmetric buckled delamination has the following properties: under a certain residual pressure, there exist two characteristic radii, namely the critical radius Rc and growing radius Rg; for a certain interface toughness, the blister has three configuration of stationary, stable growth and unstable growth with increasing the loads Under a higher edge thrust, the nonaxisymmetric secondary buckling will occur on the base of axisymmetric buckling and then the toughness and the driving force of the interface crack will be different along the delamination front. So the growth of circular delamination will not be self-similar. Without any assumption regarding the delamination front, the cogfigurations of the blister with several nonaxisymmetric buckling modes n=2, 3, 6, 8, are simulated. The nonaxisymmetric growth process for the nonaxisymmetric buckling mode n=2 is simulated also under a sequence of loads.

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.

The problem of an interface crack between dissimilar piezoelectric layers under mechanical and electrical impacts is formulated by using integral transform and Cauchy singular integral equation methods. The dynamic stress intensity factor and dynamic energy release rate (DERR) are determined through use of the obtained solutions and the effects of the loading ratio, the geometry of crack configuration and the combination of material parameters on the above two quantities are discussed. The numerical calculations indicate that the electrical load can promote or retard the crack growth depending on its magnitude, direction and the existence of the mechanical load and that with the increase of the value of ratio of two material parameters, some material parameters will inhibit the crack growth. On the other hand, some material parameters play the contrary roles. In addition, the geometry of the crack configuration has the significant effects on the DERR. Finally the results are compared with those obtained in a previous investigation.

The wave function expansion method and singular integral equations are used to investigate the scattering of SH waves by a cylindrical piezoelectric inclusion partially debonded from piezoelectric matrix. For impermeable crack case, dynamic stress intensity factors are obtained and numerical results show the phenomenon of low frequency resonance for various debonding sizes and incident angles.

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.

Using the integral transform and the Cauchy singular integral equation methods, the problem of an interface crack between two dissimilar piezoelectric layers under mechanical impacts is investigated under the permeable electrical boundary condition on the crack surface. The dynamic stress intensity factors (DSIFs) of both mode-I and II are determined. The effects of the crack configuration and the combinations of the constitutive parameters of the piezoelectric materials on the dynamic response are examined. The numerical calculation of the mode-I plane problem indicates that the DSIFs may be retarded or accelerated by specifying different combinations of material parameters. In addition, the parameters of the crack configuration, including the ratio of the crack length to the layer width and the ratio between the widths of two layers, exert a considerable influence on the DSIFs. The results seem useful for design of the piezoelectric structures and devices of high performance.