Abstract
The lifetime prediction of ceramics has been discussed on the basis of the relationship between the crack velocity, V, and the stress intensity factor KI. In the present study, crack growth tests by double torsion (DT) method were carried out under static and cyclic loadings in order to examine the effect of both water environment and stress cycling on the KI-V characteristics for alumina and zirconia. In both materials in static and cyclic loading crack velocity in water was higher than that in air, and that tendency was more remarkable in zirconia. In addition, the decrease in crack propagation parameter n and the increase in crack velocity due to cyclic stress were clearly observed in both materials in air and water environment. The KI-V characteristics determined by double torsion method were used to predict time-to-failure under static and cyclic loading of alumina and zirconia ceramics. The predictions agreed qualitatively with the experimental results.
