Validated numerical analysis of residual stresses in Safety Relief Valve (SRV) nozzle mock-ups

In general, the tensile residual stresses typically associated with weldments, and the presence of corrosive environments, are a major concern due to the possibility of Stress Corrosion Cracking (SCC). In the case of the dissimilar metal welds typically used in the primary circuits of pressurised light water nuclear reactors the presence of tensile residual stress and corrosive environment leads to so-called Primary Water Stress Corrosion Cracking (PWSCC). It is thus of technological importance to know the residual stresses associated with the dissimilar metal welds in order to assess the susceptibility of components to PWSCC. The current paper presents finite element simulations of the full manufacturing process of dissimilar metal weld mock-ups with and without a full structural overlay weld. The present simulations are validated by comparison with deep hole drilling (DHD) and incremental deep hole drilling (iDHD) residual stress measurements. A dedicated welding heat source modelling tool was used in order to reduce the uncertainties in the thermal solution by calibrating ellipsoidal Gaussian volumetric heat sources using the detailed welding records. In the mechanical analysis a mixed isotropic–kinematic (Lemaitre-Chaboche) material hardening model was employed to produce the most representative material response to the cyclic thermo-mechanical loading imposed during welding.