Determination of v–K curves from lifetime tests with reloaded survivals

Abstract

Lifetime tests under static load are often carried out in order to determine the relation v(K) of subcritical crack growth. Depending on the scatter behaviour of the most serious cracks in a specimen a number of immediate failures can occur during load application and some specimens will not fracture within a certain maximum lifetime limit. In order to get additional information on subcritical crack growth behaviour, the authors recommend performing lifetime tests at an increased load level. Appropriate procedures for the evaluation of such tests will be outlined. First, the procedure is explained for the simple case of the power-law crack growth relation. Then, a modified lifetime evaluation is proposed that needs no special crack growth law. The methods described are applied to static lifetime measurements on SiAlON in distilled water at 20 °C as the environment.