Failure behavior and failure criterion of conductive cracks (deep notches) in piezoelectric ceramics I – the charge-free zone model

The charge-free zone model proposed by Zhang et al. for the failure of conductive cracks in dielectrics was extended to predict the failure behavior of conductive cracks in piezoelectric ceramics. Piezoelectric ceramics were treated as mechanically brittle and electrically ductile materials in the charge-free zone model. The failure criterion, developed from the charge-free zone model, for conductive cracks in piezoelectric ceramics under mechanical and/or electrical loading has an elliptic shape in terms of the normalized electric intensity factor and the normalized stress intensity factor. The experimental results reported in Part II of the series verified the theoretical predictions.