Some Remarks on “Improved Analysis for Flexural Creep with Application to SiAlON Ceramics”

Abstract

An earlier paper co-authored by the present author contains a major assumption in the analytical method that may not be valid in a general class of structural ceramics. A more-rigorous mathematical analysis without this assumption has been performed, and the closed-form solutions of the description of the asymmetric power-law creep behavior are presented. The results presented here should be regarded as further improvements to the original paper, because they are applicable to a more-general case without such an assumption. Using the two loading cases as a numerical example, the present solutions indicate that, in the case of SiAlON ceramics, the original predictions on the stress exponents are still valid. However, the predictions on the pre-exponent constants differ from one to three orders of magnitude, because of error propagation.

Prediction of tensile power law creep constants from compression and bend data for ZrB2–20 vol% SiC composites at 1800 °C

“…Most importantly, we showed the solution proposed by Chuang [17] to successfully predict the compressive stress exponent which we measured here. The predicted tensile creep parameters were within those published for refractory compounds under tension or tensile bending stress, and based on recent findings published by our research group.…”

“…(12) and (ii) use of load-point displacement rates instead of curvature rates leading to a systematic error of ~20% as stated in Ref. [17]. Although the calculated results were satisfactory, compressive creep data were included to determine the tensile parameters by "pinning" the theoretical values to the experimental measurements by adjusting the Fig.…”

“…For the range of values expected for t n in the present system, and after inspection of different parameters, inequality (9) can be accepted for the present system and Chuang's equations can be adopted [17]:…”

“…Two governing equations relating the neutral axis position and the curvature rate of the beam subjected to a bending moment were given in a coupled non-linear algebraic form that can be solved numerically. He later introduced a simplified analytical solution that can be used given that shift in neutral axis location and curvature rates from two different bend data are available [16,17].…”