Development and application of micromechanical material models for ductile fracture and creep damage

Abstract

Different micromechanical material models were applied to simulate ductile fracture and creep damage. Ductile fracture behaviour of different specimens was analysed by using the modified Gurson model which is based on physical descriptions of micromechanisms of ductile fracture characterized by nucleation, growth and coalescence of voids. Due to the transferability of micromechanical parameters between different geometries and loading situations this model has been used to extend the fracture mechanics data base of an irradiated weld material. In contrast to the J-integral concepts the modified Gurson model can be employed to assess the initiation and propagation behaviour of a crack at the interface of two different materials like ferrite and austenite, with large gradients of the properties at the fusion line. A new material model for creep damage is a combination of the Rodin and Parks model and the viscoplastic model of Robinson. It contains a strain controlled evolution law for the damage parameter ρ. The material parameters were fitted to different creep curves. The application of the model to different specimens shows a good agreement between the predictions and the experiments.