Fracture criteria of piezoelectric ceramics with defects

In this paper, based on a solution of an elliptic cavity in piezoelectric ceramics with uniform loading at infinity, we analyze the stress and electric fields in the limit cases of the solution when the elliptical cavity tends gradually to a crack. The result in the zone near the crack tip is different from the result in the zone far away from the crack tip. The calculation results of a PZT-4 material are presented. Two new fracture criteria are developed for piezoelectric fracture in this paper. One is based on a generalized stress intensity factor related to the stress field at the tip of the crack and another is based on the crack opening displacement (COD) related to the relative displacement of crack faces. PZT-5h ceramics with a center crack were subjected to the combined effect of mechanical load and electrical load in this experiment to analyze the effect of electric field on fracture. The measured fracture toughness of central crack specimens of poled soft lead zirconate titanate ceramics (PZT-5) is presented to compare with the theoretical results. Some existing fracture criteria are examined through the comparison of their calculation results and the experimental results.