Modelling for Ductile-to-Brittle Transition under Ductile Tearing for Reactor Pressure Vessel Steels

摘要

The local stress-strain fields (SSF) near the crack tip has been investigated by finite element method in finite strain statement (with regard for a change of the crack tip blunting) for both stationary crack and crack growing by ductile mechanism. Using the revealed particularities of SSF near the stationary and growing crack tips and the local cleavage fracture criterion proposed earlier, the phenomenon of the ductile-to-brittle transition has been explained for reactor pressure vessel steels. The model has been proposed to predict the amount of ductile crack extension preceding the ductile-to-brittle transition as a function of test temperature. The procedure for calculation of cleavage fracture toughness has been also elaborated with regard for ductile crack extension. Analysis of the obtained calculated results and available experimental data has been performed. Alternative approaches for interpretation of the ductile-to-brittle transition have been discussed.