Physical-and-mechanical model for prediction of the neutron irradiation effect on the strength, ductility and fracture toughness of austenitic steels

A physical-and-mechanical model of ductile fracture is developed to predict fracture toughness and fracture strain of irradiated austenitic stainless steels taking into account stress-state triaxiality and radiation swelling. The model is based on criterion of plastic collapse of a material unit cell and takes into account deformation voids nucleation, growth of deformation and vacancy voids, and their coalescence controlled by strain hardening of a material. For justification of the model experimental data on fracture strain and fracture toughness of austenitic stainless steel 18Cr-10Ni-Ti grade irradiated up to 46-49 dpa with various swelling have been used. The developed model is applied for prediction of drastic decrease in the ultimate tensile strength of irradiated austenitic steels with high swelling values. The mechanism called by the authors the 'running collapse mechanism' is used for modeling the material ductile fracture when stresses are less than the yield strength, this mechanism makes an unstable crack growth possible at low stresses