Study on Residual Stress Releasing of 316L Stainless Steel Welded Joints by Ultrasonic Impact Treatment

In this paper, the effect of ultrasonic impact treatment (UIT) on the residual stress of 316L welded butt-joint was investigated. Firstly, the temperature field distribution in the welded joint was simulated based on the double-ellipsoidal heat source model, and the residual stresses were calculated by a sequential coupling thermo-mechanical finite element method. Subsequently, based on the theory of transient contact mechanics, the effects of UIT on releasing of the welding residual stress was analyzed. The microstructure of the weld metal before and after the UIT treatment was compared to study the influence of UIT. The results show that the maximum residual stresses in the weld metal and heat affected zones are released due to the dislocation multiplication during the UIT, and this effect on the weld metal is more remarkable than that on the heat affected zones. The results of numerical simulation of UIT are consistent with the corresponding experimental results. After UIT, the transverse and longitudinal tensile stresses near the fusion line are changed to compressive stresses.