Variability and Lower Bound of Fracture Toughness of Welds in the Ductile to Brittle Transition Regime

The reference temperature To was measured for both T-S and T-L-specimen orientation in 24 layers across the thickness of the beltline weld of a reactor pressure vessel. It turned out to vary in a bandwidth of more than 40K. Because of a high scatter, no clear pattern of To as a function of the thickness position could be recognized. A more detailed analysis revealed that the median of K-Jc was considerably steeper than predicted by the Master-Curve, which leads to a bias of T-0 with respect to the test temperature relative to To. By a modified evaluation procedure, the scatter of the reference temperature could be significantly reduced, which enabled the global pattern of To to be recognized. By comparing the theoretical lower bound to K-Jc-data of the used specimens with the individual measured K-Jc a representative To that characterizes the overall toughness behaviour of the weld was determined. It turned out to be about 10 K lower than the maximum local T-0. (C) 2014 Published by Elsevier Ltd.