Study on the effect of welding residual stress on creep-cyclic plasticity behaviour

Creep-cyclic plasticity and creep-fatigue damage interaction of a welded flange are studied considering both the thermo-mechanical load and the welding residual stress (WRS). The presence of WRS was found to have a minimal effect on the shakedown and ratcheting interaction curve, though the stress distribution changes considerably in the presence of WRS. The effect of WRS is predominant for the initial cycles after which it relaxes so that at steady state the creep-cyclic plasticity response is similar with and without WRS. Depending on the magnitude and sign of the WRS at different locations in the weldment, it has both detrimental and beneficial effect on the creep-fatigue life. Investigations are carried out using the Linear Matching Method (LMM), which is further modified to assess the creep- fatigue damage considering both transient cycles and the WRS. Results show that the presence of weldment induces tensile and compressive stress/strain at the vicinity of the weldment, which substantially influences the creep and fatigue damage. The presence of WRS further complicates this. For all the combinations of damage calculations undertaken, with and without the consideration of WRS or mean strain, the order of elements with maximum damage differed