Modeling for ductile-to-brittle transition under ductile crack growth for reactor pressure vessel steels

The local stress-strain state (SSS) near the crack tip is investigated by t he finite element method in the finite strain statement (with regard to a c hange of the crack tip blunting) for both stationary cracks and crack growi ng by a ductile mechanism. Using the revealed particularities of SSS near t he stationary and growing crack tips and the local cleavage fracture criter ion the phenomenon of the ductile-to-brittle transition is explained for re actor pressure vessel steels. The model is proposed to predict the amount o f ductile crack extension preceding the ductile-to-brittle transition as a function of the test temperature. The procedure for calculation of the clea vage fracture toughness is also elaborated with regard to ductile crack ext ensions. Analysis of the obtained calculated results and available experime ntal data is made. Alternative approaches for the interpretation of the duc tile-to-brittle transition are discussed. (C) 1999 Elsevier Science Ltd. Al l rights reserved.