Evaluation of electromechanical fracture behavior by configurational forces in cracked ferroelectric polycrystals

A micromechanical non-linear model is developed to predict the polarization switching and domain structure evolution in cracked ferroelectric polycrystals with both 2D and 3D implementation by finite element method. A criterion for evaluating fracture behavior is performed by means of configurational forces at the crack tip based on generalized energy balance theory. The x1-component of configurational forces corresponds to the electromechanical J-integral in linear piezoelectric materials. Now, the physical meaning and the path-dependence properties of configurational forces are investigated for non-linear ferroelectric behavior. The microstructure of domain evolution is simulated near the crack tip. Numerical results of the configurational forces at the crack tip with respect to the applied electric fields show a butterfly loop for the initially unpoled ferroelectric body, while a half butterfly loop is obtained for the initially poled case. It is also found that the configurational forces on specific crack front positions are strongly dependent on the local orientation of grains surrounding the tip.