A model of electric fracture and fatigue of ferroelectric material under electromechanical loading

The fracture and fatigue of ferroelectric ceramics under an electric field or a combined electric and mechanical loading are investigated in this paper. Domain switching is generally regarded as the cause for nonlinearity of ferroelectrics. A group of integrity expressions for the domain switching regions near the crack tip are given to distinguish the different regions of 90°domain switching and 180°domain switching under various electromechanical coupling loads, as well as under different initial poling directions. Based on the two-step switching criteria, another method is additionally developed to discuss the domain switching zones. The toughness variation of ferroelectric ceramics due to the domain switching is analyzed, showing that a positive electric field enhances the propagation of an insulating crack perpendicular to the poling direction, while a negative field impedes it. The problem of electric-field-induced fatigue failure in ferroelectric ceramics is theoretically and numerically studied by modifying the small-scale domain switching model[1][2]. In the modified analytical model presented in this paper, both the effect of anisotropy of the material and the effect of the electromechanical coupling of loading are considered. The fatigue crack growth under various coupling loads and the effects of the stress field and electric field on toughness variation are analyzed. The prediction of the crack growth versus cyclic electric field agrees well with experimental measurements.