Approach for J-R curve determination based on sub-size specimens using a triaxiality dependent cohesive zone model on a (ferritic-martensitic) steel

An approach has been developed which is able to predict J-R curves of standard-size specimen geometries. The general idea is based on the assumption that the finite element method in combination with the cohesive model, which is based on the traction-separation relationship, is able to cover the geometrical size effects of fracture mechanics specimens. This means that cohesive zone parameters can be identified independent on geometry. For ductile crack growth a stress triaxiality dependent cohesive zone model developed by Scheider (2000) is used to cover different stress states within the specimens. The evaluation procedure is verified on steel T91.