Single-edge precracked beam test and electric fracture mechanics analysis for piezoelectric ceramics

The electric fracture behavior of a piezoelectric ceramic under applied electric fields has been discussed through experimental and theoretical characterizations. The single-edge precracked beam tests were performed on a commercial lead zirconate titanate ceramic. Mechanical loading was applied by the crosshead displacement control of the screw-driven electromechanical test machine. The fracture initiation loads under different electric fields are obtained from the experiment. It is shown that the crack opens less under a positive electric field (electric field in poling direction) than under a negative electric field. A finite element analysis was also employed to calculate the energy release rate and stress intensity factor, and to study the validity of the electrical boundary conditions at the crack surfaces to be permeable in piezoelectric materials. An expression is presented for determining the fracture properties due to electrical effects by experimental and theoretical means. For a given displacement, the energy release rate is lower for positive electric fields and higher for negative electric fields. This is in agreement with the experimental findings. The numerical results under an applied force are in contrast to those under a constant displacement, and consistent with the relevant experimental results.