FATIGUE OF YTTRIA-STABILIZED ZIRCONIA .1. FATIGUE DAMAGE, FRACTURE ORIGINS, AND LIFETIME PREDICTION

Uniaxial tension-compression fatigue behavior of 3-mol%-yttria-stabilized tetragonal zirconia polycrystals was investigated. Hysteresis in the stress-plastic strain curve featured cumulative plastic strain and weakened elastic stiffness. Fracture statistics in terms of cycle-to-failure depends strongly on the maximum stress and less on the stress amplitude. Preexisting processing flaws were identified as the fracture origins in all cases. We suggest that microcracking is the dominant mechanism of fatigue damage, that nucleation of fatigue crack is usually not necessary, and that fatigue lifetime is primarily controlled by crack propagation, which is most sensitive to the maximum stress.