Macrocrack Microcrack Interaction in Piezoelectric Materials

Abstract

Owing to the well known performance of the mechanical electric coupling in piezoelectric ceramics, these kinds of materials are found to have wide technological applications such as transducers, sensors, and actuators. Generally speaking, piezoelectric ceramics show a brittle nature, from the mechanical point of view, and are susceptible to fracture when a macrocrack is formed. The understanding of the fracture behavior of piezoelectric ceramics is of great importance, consequently it received considerable attention in the past decade. Sosa and Pak (1990), Sosa (1991, 1992), Pak (1990, 1992), Park and Sun (1995a, b), and Pak and Carman (1997) studied the two-dimensional problems for an elliptic hole or crack in piezoelectric materials. They defined two kinds of intensity factors, i.e., the traditional mode I and mode II stress intensity factors (SIF’s) and the electric displacement intensity factor (EDIF). As regards the conservation integrals in piezoelectric materials, Pak (1990), Suo et. al. (1992) proposed the J integral which also has a clear physical significance as the total potential energy release rate (TPERR). However, Park and Sun (1995a, b) pointed out that neither the SIF’s nor the TPERR are suitable for describing the fracture behavior of piezoelectric ceramics. They showed that a new fracture criterion should be proposed, which is based on the concept of Mechanical Strain energy release rate (MSERR).