Mechanistic Prediction of Fracture Processes in Ferritic Steel Welds Within the Transition Temperature Regime

Abstract

This work examines the fracture behavior of ferritic steel welds in the transition temperature regime, where failure can occur either by ductile tearing or cleavage fracture. A computational and probabilistic-based mechanistic approach to cleavage fracture and ductile crack growth is adopted to model the fracture processes. The softening effect of ductile damage close to the crack tip is described by a Gurson-type material model. A statistical approach linked to both the Weibull stress and the initial void volume fraction is employed to determine the probability of cleavage fracture and the coupling between both fracture mechanisms. Finite element results are relied upon to interpret experimental fracture toughness data for the welds and to examine the effects of near crack tip damage and crack growth on the cleavage failure probabilities and cleavage and ductile fracture toughness distributions. The scatter in the weld experimental fracture toughness data is well reproduced by the proposed cleavage and ductile tearing models.