A fracture criterion for conducting cracks in homogeneously poled piezoelectric PZT-PIC 151 ceramics

A fracture criterion For conducting cracks in piezoelectric ceramics under combined electrical and mechanical loads is proposed in connection with a measured material specific fracture curve of PZT-PIC 151. The characteristic fracture curve of the investigated material is a function of the stress intensity factor, K-I, which is known from fracture mechanical concepts, and the recently defined electric field intensity factor, K-E, for conducting cracks. A four-point-bending device for fracture tests under combined electrical and mechanical loads serves as the experimental set-up. The measured quantities, force, displacement, applied voltage and crack length, are used to evaluate the experiments. The finite element method (FEM) was used to determine the mechanical stress intensity factor, K-I, and the electric field intensity factor, K-E, taking into account linear piezoelectric coupling in the material. A qualitative process zone model is proposed for a physical interpretation of the Fracture curve. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.