IMPROVED ANALYSIS FOR FLEXURAL CREEP WITH APPLICATION TO SIALON CERAMICS

By using a statistical least‐squares method to minimize the differences between predicted and measured load‐point displacement rates from four‐point bend specimens, power‐law creep parameters for tension and compression were estimated. An alternative but simpler method of estimating power‐law creep parameters from flexural creep data is also proposed. This method entails the direct measurements of steady‐state creep strain rates at two stress levels by an indentation technique. Based on a closed‐form solution, the power‐law creep parameters could then be estimated from both the measured neutral axis locations and curvature rates. The results from these two methods compare favorably with one another, and with the simple compressive creep data. Both methods yield a high stress exponent of about 14 for tension and a stress exponent of about unity for compression. Cavitation‐enhanced creep in tension and diffusional creep in compression are responsible for this asymmetric behavior. Copyright © 1990, Wiley Blackwell. All rights reserved