Slow crack growth in 3Y-TZP under static and cyclic fatigue

An analysis of the slow crack propagation in a 3Y-TZP zirconia ceramic is presented under static and cyclic loading. A wide range of crack velocities, from 10-12 m/s to 10-2 m/s, was investigated with the double torsion (DT) and indentation techniques. The results reveal the presence of threshold stress intensity factor values, for both static and cyclic fatigue, below which no slow crack growth occurs. These thresholds are of major importance for hip prostheses applications because they theoretically define safety factors for 3Y-TZP ceramics. The influence of the grain size on crack velocity is investigated and a single master law independent of the grain size is proposed. (orig.)