Probabilistic sensitivity analysis of dwell-fatigue crack initiation life for a two-grain microstructural model

Crack initiation in Ti-6242 has been observed to occur in a grain with a hard orientation for basal slip neighbouring a grain with a soft orientation. Because there is significant variability in microstructural features and crack initiation life, it is useful to explore the effects of the variability of the microstructural components through a probabilistic sensitivity analysis. In this paper, a probabilistic crystal plasticity finite element model of a hard soft grain combination (2 grains) was exercised considering the Schmid factor of the soft grain, the misorientation angle between the two grains, and the soft grain size as random variables. A probabilistic sensitivity analysis of the time-to-crack initiation was then employed in order to ascertain the relative importance of the random variables. The results indicate that the variance in the Schmid factor accounts for the majority of the variance in the time-to-crack initiation. A local sensitivity analysis found that larger Schmid factors result in smaller mean life and larger variance. The neighbouring soft grain size was found to be less important than the Schmid factor and misorientation angle.