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

Crack growth behavior in ferroelectric ceramics was examined under purely e lectrical and purely mechanical loading conditions. While cracks grew under mechanical loading along the plane of the maximum tensile stress, crack gr owth under electrical loading tended to be intergranular and the direction of the crack growth was found to vary greatly with geometric arrangements o f applied electric field, remnant polarization and crack orientation. When both the applied field and remnant polarization were perpendicular to the c rack plane, the crack propagated straight ahead on the original plane. Howe ver, for other electrical configurations, cracks were driven to propagate o n the planes inclined up to 90 degrees from the original crack plane. Analy sis 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. (C) 2001 Elsevier Science B.V. All rights reserved.