Time-dependent fracture of an alumina under long-term static and cyclic loading was investigated by four- and three-point flexure tests. Bend bars with two different sizes were prepared to evaluate the size effects on the failure time distribution. The resulting stress-life data mere analyzed by two statistical time-dependent fracture theories which incorporate the statistics of strength and flaw size distribution with subcritical crack growth that leads to delayed fracture. The first model considers only the growth of a single major crack to a critical size while the second considers the size distribution of multiple flaws and their slow crack growth characteristics. Both models provided commonly acceptable description of the static and cyclic strength-probability-lifetime relationships for the experimental results from various specimen sizes and flexure modes.
