Creep and Stress Rupture Behavior of an Advanced Silicon Nitride: Part III, Stress Rupture and the Monkman-Grant Relationship

The applicability of the Monkman–Grant relationship to predict the stress rupture life of NT154 silicon nitride is examined. The data show that the Monkman–Grant lines relating rupture life to minimum creep rate are stratified with respect to temperature. A modification to the current expression for the Monkman–Grant relation is proposed to accommodate this temperature dependence. A phenomenological approach based on crack growth as the failure mechanism is presented to explain this temperature dependence. The results can be interpreted as suggesting that the stress dependence of the failure process is greater than that for creep.