size correction scheme to determine fracture toughness with mini-CT geometry in the transition regime

The mini-CT geometry is known to provide appropriate experimental fracture toughness along with master curve characterization in the transition regime. However, due to significant loss of constraint experienced at J-levels close to reference temperature T0, current size correction for the fracture toughness according to ASTM E1921 standard requires a better assessment in order to avoid censoring a large number of mini-CT specimens. Indeed, the current tight ASTM E1921 requirements on KJC limit value to ensure that the computed transition temperature T0 is reliable often implies that many samples need to be censored. A large number of censored specimens leads to a significant loss of time, money and material and unnecessary activated material in the case of irradiation campaigns. Besides, because of the specimen size reduction, more mini-CT samples and lower test temperatures as compared to large sized samples are required to generate a reliable T0 value. In this study, an improved method of size correction for KJC as determined from the mini-CT geometry is proposed based on a local approach of brittle fracture model combined with FEM simulations. The results show that the proposed size correction reduces the T0 bias compared to the 1T-CT geometry. It also contributes to the relaxation of the KJC limit for the mini-CT geometry as compared to the ASTM size corrected values