BRITTLE-FRACTURE OF NUCLEAR PRESSURE-VESSEL STEELS .2. PREDICTION OF FRACTURE-TOUGHNESS

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 an alysis was performed of the stress-strain state near the crack tip in the finite strain statement. The model proposed allows one to obtain a n adequate prediction for fracture toughness both at the low temperatu res at which brittle fracture is realized and higher temperatures at w hich fracture is ductile. Also the proposed model describes the plasti c prestrain effect on fracture toughness. As applied to a 2.5Cr-Mo-V s teel it has been shown that fracture toughness is controlled by condit ion of cleavage microcrack nucleation near the crack tip but not by an y 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 transit ion only but not a value of K-IC. (C) 1997 Elsevier Science Ltd.