Evaluation of fracture toughness based on results of instrumented charpy tests

The modified Gurson model is used to determine micromechanical toughness parameters of a weld material from the irradiation surveillance of a reactor pressure vessel. These parameters were used to numerically simulate static and dynamic fracture mechanics tests for the determination of J-resistance curves. The results were confirmed by means of experiments with irradiated subsized specimens of the original material. The essential steps of the analysis-the consideration of rate-dependent stress-strain curves and the determination of the material parameters, as well as the numerical modelling of the boundary conditions at the supports of the Charpy specimen-were validated by comparing analyses and experiments with a representative unirradiated submerged arc weld material. The initiation values of the J-resistance curves converted into pseudo-plane strain fracture toughness values K Ic allowed the conservative adjustment of the ASME reference fracture toughness curve.