Strength of many ceramics and glasses show a noticeable influence on the environment and measurement conditions. This can be also the case for typical strength measurement experiments following the standards, e.g. performing a 4-point bending test under constant stress rate conditions, where fracture occurs within several seconds [1]. Assuming a Weibullian inert strength distribution and taking the effect of sub-critical crack growth in terms of a Paris-law type v-K curve into account, the resulting strength distribution obtained by constant stress-rate experiments can be expressed by a simple closed-form expression [2]. This general ansatz for strength distributions can be used to interpret the whole sets of data measured at different stress rates, which leads to more accurate strength parameters with respect to the width of corresponding confidence intervals.
Finally an example will be presented that the slope of strength data with respect to the stress rate depend on features of the underlying v-k curve [3]. This relationship can be used for an indirect method to estimate the v-K curve.
References:
[1] ASTM C1161-18
[2] P. Supancic, H. Schöpf, J. Eur. Ceram. Soc., 32[16] (2012).
[3] R. Bermejo, P. Supancic, C. Krautgasser, R. Morrell, R. Danzer, Eng. Fract. Mech., 100 (2013)