TIMES: An International Project on Transferability of Fracture Toughness Values for Irradiated RPV Steels

摘要

The prediction of specimen or component failure behavior can be attained by the use of local approach (LA) models based on Weibull stresses. Over the last years recent developments have been achieved, and the predictive capabilities of these models have been improved significantly. In this paper a concept, which is based on a LA model, will be proposed for the prediction of fracture toughness for different specimen types made of ferritic base and weld metal in the unirradiated as well as in the irradiated state. The only necessary input parameter will be the yield strength of the material at one temperature (preferably room temperature). The LA model under consideration is tuned for its temperature dependence using a ferritic base material in the unirradiated material state. The outcome of the tuning are the Weibull parameters m, u, th, p, 0. The parameters m, th, p,0 are kept constant over temperature and for variation of materials and fluences. To model the temperature dependence over the transition region, local events like plastic shielding, blunting or arrest of micro cracks have to be considered. These events are modeled via an increase of u over temperature. The temperature shift, T, in u, is obtained by using a correlation between the yield strength of the tuned material and the material under investigation. In order to validate this concept, a large number of computations, which includes different temperatures, specimen types, loading ratios, weld and base metal in unirradiated and irradiated conditions are conducted. They lead to the prediction of a median fracture toughness curve for each material and specimen type. All numerical investigations are compared with experimental results. It could be shown that the predictions made by this approach are in good agreement with the experiments. This is encouraging for further application to other materials and irradiation conditions.