Engineering Framework to Transfer the Lower Bound Fracture Toughness between Different Temperatures in the DBTT Region

In this paper, an engineering framework to transfer the lower bound fracture toughness between different temperatures in the ductile–to–brittle (DBTT) temperature region is proposed and validated for 0.55% carbon steel using 0.5TSE(B) specimens. The framework requires only stress–strain curve for different temperatures as experimental data. The approach was based on the authors’ finding that the critical stress σ22c of the modified Ritchie–Knott–Rice criterion (the criterion predicts onset of cleavage fracture of a material in the DBTT transition temperature region, when the mid-plane crack-opening stress σ22 measured at a distance from the crack-tip equal to four times the crack-tip opening displacement δt, denoted as σ22d, exceeds a critical value σ22c) seems to be correlated with the lower bound fracture toughness for a specific specimen configuration. The proposed approach is expected to overcome some inconveniences which recent studies have reported to the Master Curve Local approaches to cleavage fracture that the Weibull parameters vary with size and temperature and are different from those stated in the Master Curve.