Two parameter approaches in the probabilistic failure assessment of ferritic steels

The present study is concerned with an assessment of constraint effects in the probabilistic assessment of cleavage fracture in ferritic steels. For this purpose, a variety of fracture mechanics specimens with different geometries, overall sizes and crack depths is tested and assessed according to the master curve concept. It is observed that the choice of the specimen has a distinct effect on the reference temperature T0. The crack front constraint situation of the different specimen types is quantified in terms of different two parameter concepts including the K-Tstress, J-Q, J-A2 and J-h approaches. The inclusion of higher order terms enables an improved description of the mechanical fields in the vicinity of the cleavage origin ahead of the crack front. Their effect on the fracture toughness KJc for brittle failure within the master curve concept can be included by an appropriate shift of the reference temperature.