Characterization of fracture toughness of dissimilar metal weld joint

The dissimilar metal welds (DMW) are mainly used to connect ferritic steel pressure vessel nozzles with austenitic stainless steel piping in nuclear power plant. The weld joint locations are critical in comparison to base metal and their integrity must be assured against fracture. In view of the variations in the tensile and fracture properties across theses weld joint, the integrity assessment is not straight forward. Accurate structural integrity assessment required accurate estimation of fracture toughness of different zones of DMW. Existing fracture toughness test standard methods, e.g. ASTM 1820 are not directly intended for DMW. Therefore, further investigations are required in order to define the best practice in evaluation of fracture toughness of theses joints. For that exhaustive experimental and numerical studies were carried out. This paper will briefly outline the procedure followed for evaluation of J-R curve and J_ic of different regions of DMW weld. The details of variation of plastic eta factor with weld strength mismatch, crack locations and crack size, and effect of weld strength mismatch on blunting line equation will be discuss in full paper