Brittle fracture of nuclear pressure vessel steels—II. Prediction of fracture toughness

Abstract

A model for the prediction of fracture toughness for nuclear pressure vessel steels has been worked out on the basis of brittle and ductile fracture criteria formulated by the authors in an earlier paper. An analysis was performed of the stress-strain state near the crack tip in the finite strain statement. The model proposed allows one to obtain an adequate prediction for fracture toughness both at the low temperatures at which brittle fracture is realized and higher temperatures at which fracture is ductile. Also the proposed model describes the plastic prestrain effect on fracture toughness. As applied to a 2·5CrMoV steel it has been shown that fracture toughness is controlled by condition of cleavage microcrack nucleation near the crack tip but not by any propagation condition. Critical brittle fracture stress S c which is usually considered as a main parameter controlling brittle fracture, determines the temperature T tr of brittle to ductile fracture transition only but not a value of K IC.