Study of surface warm shot peening on the fatigue life of a SAE 5160 leaf spring steel

Shot peening is a surface treatment used in components to improve fatigue properties. Usually, this process is performed at room temperature. However, new studies present the possibility of performing this surface treatment above room temperature in order to increase the fatigue strength even further, due to a better association of higher plastic deformation with residual stresses. The purpose of this research was to study the effects of the shot peening process at room temperature, on the fatigue performance of SAE 5160 leaf spring steel which is used by the automotive industry. Three-point bending fatigue tests were performed on specimens with the same geometry as the original component. The specimens were shot peened at 25, 100, 150, 200, 250 and 300 °C. It has been observed that the tests performed at higher temperature caused an increase in surface roughness and decreased the residual stress levels. The residual stress values increased for shot-peened specimens at temperatures up to 100 °C and decreased continuously for temperatures above this.