Crack Stability and Strength Distribution of Ceramics That Exhibit Rising Crack‐Growth‐Resistance ( R ‐Curve) Behavior

Crack stability and strength distribution are examined for ceramics that exhibit R‐curve behavior. An empirical power‐law description for the R curve leads to simple analytical formulations for the Weibull modulus and the scale parameter; however, the power law is inconsistent with the stability of surface cracks recently observed in MgO‐partially‐stabilized zirconia and coarse‐grained alumina. It is shown that alternate empirical fits to the R curve are compatible with the stable extension of surface cracks, even in the absence of any localized residual stresses.