A crack-location correction for T ₀ analysis of an alloy 52 dissimilar metal weld

For narrow-gap Alloy 52 dissimilar metal welds, the fusion boundary between the ferritic pressure vessel steel and austenitic Ni-base alloy weld metal is the weakest region from fracture mechanical perspective. Producing of the pre-crack for fracture toughness test specimens in the fusion boundary region to determine T ₀ is challenging. For pre-cracks further away from the fusion boundary, the brittle fracture initiation does not necessarily occur on the initial crack plane, but rather in the fusion boundary region. This offset in initiation site can increase the measured fracture toughness leading to a nonconservative T ₀ estimate. In this study, a method is proposed for correcting the fracture toughness for crack location and obtaining a lower boundary fracture toughness curve. The crack-location correction shows promise for analysing T ₀ of specimens with pre-cracks systematically at a significant distance from the weakest region, but with brittle fracture initiation still occurring at the weakest location.