Cyclic Fatigue Crack Growth in PZT Under Mechanical Loading

Crack growth under static and cyclic mechanical loading in lead zirconate titanate was studied using four point bend specimens in poled and unpoled states. Fatigue crack growth occurred at lower stress intensity factors than crack growth observed under static loading. The relation between crack velocity and applied stress intensity factor under static loading was affected by poling and followed a power‐law relationship. Crack velocity vs. stress intensity amplitude under cyclic loading followed a Paris power‐law relationship and was found to be unaffected by poling. A controlled unloading experiment revealed that the apparent stress intensity factor for crack extension decreased with increased unloading time but was essentially unaffected when the unloading cycle was less than five seconds, hence indicating the absence of an extrinsic fatigue mechanism.