NEW APPROACHES TO IMPROVE THE RPV MATERIALS DATA-BASE

The models for the local approach to cleavage fracture and to ductile tearing include the effects of specimen geometry and loading situation on the damage development. Thus, these concepts can be used to predic t fracture toughness and tearing resistance curves for different sizes of specimens or structures, based on an analysis of tests with small, simple specimens. This advantage is especially valuable if only small pieces of material are available for testing which do not allow for s tandard fracture specimens. The paper outlines the basic ideas of the Beremin concept for the fracture process in brittle-to-ductile transit ion regime and of the modified Gurson model for ductile fracture in th e upper shelf. A systematic study for the brittle-to-ductile transitio n regime showed that the Beremin model has to be modified to take into account the effect plastic strain has on the fracture process. For du ctile fracture, it was demonstrated that by testing and modeling a smo oth bar and a fracture mechanics specimen, one set of material paramet ers may be found which can be subsequently applied to other structures and, hence, used to extend the material data base. (C) 1998 Elsevier Science S.A. All rights reserved.