A maximum strain criterion for electric-field-induced fatigue crack propagation in ferroelectric ceramics

Crack growth behavior in ferroelectric ceramics was examined under purely electrical and purely mechanical loading conditions. While cracks grew under mechanical loading along the plane of the maximum tensile stress, crack growth under electrical loading tended to be intergranular and the direction of the crack growth was found to vary greatly with geometric arrangements of applied electric field, remnant polarization and crack orientation. When both the applied field and remnant polarization were perpendicular to the crack plane, the crack propagated straight ahead on the original plane. However, for other electrical configurations, cracks were driven to propagate on the planes inclined up to 90° from the original crack plane. Analysis of the electromechanical conditions in the specimens indicated that the crack preferred to propagate on the plane of the maximum principal strain, thus satisfying a maximum strain criterion.