IMPROVEMENT IN FATIGUE PERFORMANCE OF POWDER-FORGED CONNECTING RODS BY SHOT PEENING

Shot peening is a surface treatment that is commonly used to improve the fatigue performance of structural components. Improvement is attributed to the formation of compressive residual stresses on the surface layer of the component by the impact of spherical shot. These stresses are known to reduce service tensile stress and therefore increase fatigue performance. To quantify the effect of shot peening, a series of powder forged (PF) connecting rods were peened at several intensity levels, evaluated in fatigue, and the data correlated with compressive residual stress. Stress magnitude and depth were measured utilizing X-ray diffraction methods. Scanning electron microscopy (SEM) was also performed to determine the fracture initiation site(s).