Mismatch effect of creep properties on steady-state stresses for welded straight pipes: Quantification and application

This paper describes steady-state stresses on welded straight pipes with the heat-affected zone (HAZ) using detailed two dimensional elastic creep finite element analyses. In our previous studies [9, 10], it was found that the mis-match effect in creep on steady-state stresses within the weld metal for a various branch junction could be uniquely quantified by the mis-match factor, defined as a function of creep exponent and constants. The present study expands the findings to be applicable for welded straight pipes, not only the most widely used but also relatively simple compared to branch junctions. To see the effects of mis-match in creep properties and weld configuration, the parametric studies have been performed for various mismatched creep properties and three different groove angles, respectively. Internal pressure, tension and its combined cases are applied to investigate the effect of the loading mode. It is found that steady-state creep stresses can be quantified as mis-match factor and creep exponent. In conclusion, validation of the findings is presented and discussed through an application to the CMV pipe.