CREEP AND STRESS RUPTURE BEHAVIOR OF AN ADVANCED SILICON-NITRIDE .3. STRESS RUPTURE AND THE MONKMAN-GRANT RELATIONSHIP

The applicability of the Monkman-Grant relationship to predict the str ess rupture life of NT154 silicon nitride is examined. The data show t hat the Monkman-Grant lines relating rupture life to minimum creep rat e are stratified with respect to temperature. A modification to the cu rrent expression for the Monkman-Grant relation is proposed to accommo date this temperature dependence. A phenomenological approach based on crack growth as the failure mechanism is presented to explain this te mperature dependence. The results can be interpreted as suggesting tha t the stress dependence of the failure process is greater than that fo r creep.