The Effect of Shot-Peening on Thermal Residual Stress around the Singular Point of Cu-Low Alloy Rail Steel in Welded Joints

Abstract

A copper wire was welded to low-alloy rail steel by exothermic welding. There were pre-heating and post-heating processes before and after welding, respectively. Unfortunately, the cooling rate of temperature could be controlled in the post-heating process. The cooling rate of temperature was too fast because the ambient temperature was very low (-5 °C). After that, the large value of thermal residual stresses remained in the welding joint and led to failure. In the present study, a welded joint between copper and low-alloy rail steel was analyzed using finite element analysis (FEA). The singularity of thermal residual stresses in the welding joint was observed after post-heating processes. The intensity of stress singularity (Kqq) was estimated around a singular point of the welded joint by least-square method. The possibility of crack initiation was determined. Then, a shot-peening process was applied on the surface of the low-alloy rail steel near the singular point of the welded joint. A small particle of 3 mm diameter was shot to make it plastically deform on the low-alloy rail steel surface. The effect of the shot-peening on the singularity of thermal residual stresses around the singular point of the welding joint was determined and found that the value of singularities for the stress sqq profile were reduced and became steady.