MECHANISTIC PREDICTION OF FRACTURE PROCESSES IN FERRITIC STEEL WELDS WITHIN THE TRANSITION-TEMPERATURE REGIME

This work examines the fracture behavior of ferritic steel welds in th e transition temperature regime, where failure can occur either by duc tile tearing or cleavage fracture. A computational and probabilistic-b ased mechanistic approach to cleavage fracture and ductile crack growt h is adopted to model the fracture processes. The softening effect of ductile damage close to the crack tip is described by a Gurson-type ma terial model. A statistical approach linked to both the Weibull stress and the initial void volume fraction is employed to determine the pro bability of cleavage fracture and the coupling between both fracture m echanisms. Finite element results are relied upon to interpret experim ental fracture toughness data for the welds and to examine the effects of near crack tip damage and crack growth on the cleavage failure pro babilities and cleavage and ductile fracture toughness distributions. The scatter in the weld experimental fracture toughness data is well r eproduced by the proposed cleavage and ductile tearing models.