Quantification of stress redistribution due to mismatch in creep properties in welded branch pipes

This paper reports steady-state stress distributions within the weld metal in a welded branch component, via detailed three-dimensional elastic-creep finite element analyses. The creep exponent and constants for the base and weld metal are systematically varied to simulate under-matching, even-matching and over-matching conditions in creep. Various loading conditions are also considered to see the effect of the loading mode. It is found that the mismatch effect in creep on steady-state stresses within the weld metal can be uniquely quantified by the mismatch factor, defined as a function of creep exponent and constant. Ratios of section-averaged (effective and maximum principal) stresses for the mismatched case to those for the even-matched case are linearly dependent on the mismatch factor.