FRACTURE CRITERIA FOR PIEZOELECTRIC CERAMICS

Fracture criteria for piezoelectric materials mere investigated. Mode I and mixed mode fracture tests were performed on PZT-4 piezoelectric ceramics to verify the validity of the mechanical strain energy releas e rate as a fracture criterion. Experimental results indicated that cr ack extension could be aided or impeded by an electric field, dependin g on the field direction. Further, the direction of crack extension wa s studied. A crack closure method, together with finite element analys is, was introduced to calculate the mechanical strain energy release r ate. The maximum mechanical strain energy release rate was used to pre dict fracture loads under combined mechanical and electrical loads. It was found that the mechanical strain energy release rate criterion is superior to other fracture criteria and predicts fracture loads fairl y accurately.