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In this paper, numerical and experimental studies are conducted to investigate the effect of post-weld heat treatment (PWHT) parameters, including holding time and temperature, on the distribution of welding residual stresses. The selected material is AISI type 304 austenitic stainless steel in the form of a pipe, for which the determination of heat treatment parameters is complicated by the risk of intergranular corrosion. The study includes experimental measurements of residual stresses both before and after PWHT of the pipe, and creep and tensile tests to determine the viscoplastic behaviour and mechanical strength of the material. Good agreement between experimental measurements and numerical predictions is obtained; therefore, further simulations were performed to study the effect of variation of heat treatment parameters on the relaxation of welding residual stresses.

The present study evaluates the effects of tensile residual stresses on fatigue behaviour of ASTM A516 pressure vessel steel specimens. In this regard, fatigue specimens containing a smooth notch region are studied. A damage coupled elastic-plastic constitutive material model is developed to investigate effects of residual stresses on fatigue life. Isotropic and kinematic hardening parameters of the material are experimentally determined. Additionally, the damage model parameters are specified from fatigue experiments conducted on standard specimens in different stress ratios. Tensile residual stresses are introduced into the smooth notched specimens through employing four-point-bending method. The hole drilling technique is utilized to measure the residual stress magnitudes. The results indicate that about two third of fatigue life of the specimens is decreased due to the existed tensile residual stresses. Furthermore, fatigue crack initiation and propagation behaviour in the specimens containing residual stress are studied based on the developed continuum damage model.