Fracture toughness prediction of reactor grade materials using pre-notched small punch test specimens

The crack initiation point has been predicted by numerical and experimental methods. The numerical method involves the GTN material damage model to identify crack initiation point. This is observed when first Gauss point failed completely. The GTN parameters which are used to invoke the crack initiation point in the p-SPT specimen were calibrated by experimental results of 3 mm diameter disk SPT specimens. However, the experimental method involves the analysis of the slope just before the maximum load to predict the crack initiation point. The predicted crack initiation points using both methods are utilized to estimate crack initiation toughness of structural steel. The crack initiation toughness values were obtained for two structural steels viz. T91 and SS304LN using the p-SPT test and compared with the standard test. The differences found were duly justified.