Abstract
This paper presents time-temperature parameter (TTP) methods for predicting the slow crack growth (SCG)-type creep rupture life in ceramics. First, a probabilistic delayed-fracture (PDF) model was proposed on the basis of the Arrhenius-type SCG concept in conjunction with the two-parameter Weibull distribution. Larson-Miller parameter (LMP) and Orr-Sherby-Dorn parameter (OSDP) were then derived from the PDF model, respectively. As a result, it was theoretically demonstrated that LMP could not be then related with the SCG concept , but OSDP could be related with that. Therefore, OSDP has more clear physical meaning than LMP for ceramics. Second, the material parameters associated with the PDF model were determined using the experimental creep data for silicon nitride. The validity of the model was confirmed through the comparison of LMP plots and OSDP plots using the experimental creep data and the material parameters. In addition, it was found that SCG mechanism changes at a transition temperature where the crack propagation index drastically drops.
