On the crack face boundary conditions in electromechanical fracture and an experimental protocol for determining energy release rates

摘要

An experimental protocol for measuring the energy release rate in a non-linear reversible electromechanical body is proposed and summarized. The potential results are capable of shedding light on the true physical nature of the conditions prevailing at the crack surface and in the space within the crack. The experimental procedure is simulated numerically for a linear piezoelectric specimen in a four point bending configuration subjected to electrical loading perpendicular to the crack. Two efficient finite element formulations are presented for nonlinear crack face boundary conditions. Methods for the numerical determination of the crack tip energy release rate and the simulation of the experimental method for obtaining the total energy release rate are developed. It is shown that the crack tip energy release rate calculated under energetically consistent boundary conditions is equal to the total energy release, when the exact boundary conditions are used, there is no such agreement.