STATISTICAL-ANALYSIS OF SIZE EFFECTS ON TIME-DEPENDENT FRACTURE OF ANALUMINA

Time-dependent fracture of an alumina under long-term static and cycli c loading was investigated by four- and three-point flexure tests. Ben d bars with two different sizes were prepared to evaluate the size eff ects on the failure time distribution. The resulting stress-life data mere analyzed by two statistical time-dependent fracture theories whic h incorporate the statistics of strength and flaw size distribution wi th 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 flaw s and their slow crack growth characteristics. Both models provided co mmonly acceptable description of the static and cyclic strength-probab ility-lifetime relationships for the experimental results from various specimen sizes and flexure modes.