Analysis of electric boundary condition effects on crack propagation in piezoelectric ceramics

There are three types of cracks: impermeable crack, permeable crack and con ducting crack, with different electric boundary conditions on faces of crac ks in piezoelectric ceramics, which poses difficulties in the analysis of p iezoelectric fracture problems. In this paper, in contrast to our previous FEM formulation, the numerical analysis is based on the use of exact electr ic boundary conditions at the crack faces, thus the common assumption of el ectric impermeability in the FEM analysis is avoided. The crack behavior an d elasto-electric fields near a crack tip in a PZT-5 piezoelectric ceramic under mechanical, electrical and coupled mechanical- electrical loads with different electric boundary conditions on crack faces are investigated. It is found that the dielectric medium between the crack faces will reduce the singularity of stress and electric displacement. Furthermore, when the per mittivity of the dielectric medium in the crack gap is of the same order as that of the piezoelectric ceramic, the crack becomes a conducting crack, t he applied electric field has no effect on the crack propagation.