Neutron Diffraction Measurement and Numerical Simulation to Study the Effect of Repair Depth on Residual Stress in 316L Stainless Steel Repair Weld

Abstract

Welding is often used to repair the defects in pressure vessels and piping, but residual stresses are generated inevitably and have a great effect on structure integrity. According to the defect size, different repair depth will be carried out, which leads to different stress state. In this paper, the effect of repair depth on residual stress in 316L stainless steel repair weld has been studied by neutron diffraction measurement and finite element modeling (FEM). The results show that the residual stresses in the deep repair are larger than those in shallow repair weld, because the deep repair involves multipass welding and brings a serious work hardening. In the weld metal, the longitudinal stress has exceeded the yield stress, and increases slightly with the increase of repair depth. In contrast to the longitudinal stress, the transverse stress is more sensitive to the repair depth. With the increase of repair depth, the transverse stress increases and even exceeds the yield strength as the repair depth is 45% of the plate thickness. At the bottom surface of the plate and heat affected zone (HAZ), both the longitudinal and transverse stresses increase as the repair depth increases. It also shows that the mixed hardening model gives the best agreement with the measurement, while isotropic and kinematic hardening models cause an overestimation and underestimation, respectively. Therefore, the mixed hardening model is recommended for the prediction of residual stresses.