PROBABILISTIC MODEL FOR FRACTURE-TOUGHNESS PREDICTION BASED ON THE NEW LOCAL FRACTURE CRITERIA

The stochastic nature of various critical parameters controlling cleav age fracture of nuclear pressure vessel steels has been analysed. On t he basis of the performed analysis the local criterion for cleavage fr acture proposed by authors [1,2] has been modified into a probabilisti c statement. The probabilistic model for fracture toughness prediction has been elaborated on the basis of the modified local criterion for cleavage fracture, the ductile fracture criterion proposed by authors earlier and the approximated solution for problems relating to the str ess-strain state near the crack tip. This probabilistic model allows o ne to predict the dependence of K-IC on temperature for any given prob ability of brittle fracture; to describe the effect of the specimen th ickness on K-IC; and to determine the scatter band for the brittle to ductile transition temperature. The connection of parameters determini ng the scatter of K-IC with material properties has been analysed. Com parison of experimental and calculated results has been performed as a pplied to a 2.5Cr-Mo-V nuclear pressure vessel steel. The proposed pro babilistic model has been shown to describe the lower and upper envelo pes for a large number of experimental data. (C) 1998 Elsevier Science Ltd. All rights reserved.