Brittle–ductile transition in F82H and effects of irradiation

We present here a computer simulation model for prediction of the shift in the brittle–ductile transition with irradiation dose. The model is based on discrete dislocation simulation, and is applied to the ferritic/martensitic steel, F82H. The simulated crack system involves microcracks embedded in the plastic zone of a macrocrack. The inherent scatter in fracture toughness measurements are studied by using a size distribution for microcracks, distributed on the crack plane of the macrocrack. The criterion for fracture is the propagation of any of these microcracks located at a distance ahead of the macrocrack. The fracture toughness of F82H at various temperatures is estimated by using measured irradiated and unirradiated yield stress values. Using the yield stress–temperature dependence; the shift in the transition temperature with the irradiation dose is simulated and compared with experiments. Furthermore, the observed scatter in fracture toughness measurements is found to be the result of the distribution in the size of microcracks.