A WEIBULL STRESS MODEL FOR PREDICTION OF CLEAVAGE FRACTURE IN FERRITIC STEELS

摘要

This study applies recent advances in the Weibull stress model to predict cleavage fracture in ferritic steels. The procedure to calibrate the Weibull stress parameters builds upon the toughness scaling model between two crack configurations having different constraint levels and eliminates the recently discovered non-uniqueness that arises in calibrations using only fracture toughness data obtained under small scale yielding (SSY) conditions. The introduction of a non-zero threshold value for Weibull stress in the expression for cumulative failure probability is consistent with the experimental observations that there exists a minimum toughness value for cleavage fracture in ferritic steels, and brings numerical predictions of the scatter in fracture toughness data into better agreement with experiments. In this work, the Weibull stress parameters are calibrated using fracture toughness data of deep-notch C(T) specimens and shallow-notch SE(B) specimens of an A515-70 steel. The calibrated model is then applied to predict the measured response of surface-cracked plates of the same material loaded in different combinations of tension and bending. The model predictions accurately capture the measured distributions of fracture toughness values.