Fatigue life of piezoelectric ceramics and evaluation of internal damage

Compression-compression fatigue tests were performed for PZT piezoelectric ceramics by using columnar specimens at various frequencies of cyclic loading. In fatigue tests, stress ratio was fixed to R=0.05, and maximum compressive stress was changed. A damage variable based on the continuum damage mechanics was evaluated by variation of apparent density of specimens. Moreover, area fraction of cavities on fracture surface was evaluated. As a result of experiments, the dependence of fatigue life on frequency of cyclic loading was clarified. It was also found that the damage variable is independent of the frequency, while the area fraction of cavities depends on the frequency.