Numerical analysis of crack propagation in piezoelectric ceramics

The formulation of an isoparametric displacement-eleclric potential finite element method that accounts for the electro-mechanical coupling effect of piezoelectric materials is briefly presented in this paper. The crack propa gation behaviour and the elasto-electric fields near a crack tip in a PZT-5 piezoelectric ceramic under mechanical, electrical and mechanical-electric al mixed loads are investigated using this electro-mechanical finite elemen t method. From the numerical results, it can be seen that crack propagation along the crack plane direction will be impeded and the crack will tend to propagate at an angle of about 84 degrees to the crack plane under a negat ive electric field on the basis of the maximum stress criterion. The physic al explanation of the phenomena is presented in this paper and it is shown that the mechanical strain energy release rate is not a good criterion for predicting crack propagation in the case where the ratio of the electric fi eld to the mechanical load becomes large.