Statistical analysis of the effects of prior load on fracture

Collated fracture data for three steels, A533B, A508 and BS1501, and an Aluminium alloy, 2650, were examined to assess the statistical significance of the effect of prior loading on subsequent fracture. Weibull statistical and probabilistic analysis was used throughout. Two prior loading conditions were examined; one associated with warm pre-stress, and a second using pre-compression. For the former, prior loading resulted in an increase in the mean toughness together with an increase in the shape parameter and a decrease in variability compared to the as-received material. In contrast, when prior loading involved out-of-plane compressive loading (or side-punching) statistical evidence revealed that there was a reduction in toughness together with a decrease in the shape parameter and an increase in variability. Two numerical models were applied to steel data and were able to predict the overall trends obtained from the experiments, but could not reproduce accurately the experimental statistical distributions.