Effect of surface flaw on fatigue strength of shot-peened medium-carbon steel

The effect of surface flaw on fatigue strength of shot-peened medium-carbon steel was experimentally studied. The fatigue crack initiation life, fatigue crack growth life, and fatigue limit in the steel can be increased by using shot peening (SP). The fatigue fracture of SP specimen occurred by the propagations and coalescence of fatigue cracks initiated from the initial cracks due to SP. The fatigue limit of SP specimen was determined by the propagation limit of fatigue crack. When the size of surface flaw is sufficiently small compared to the SP affected zone, the flaws have not significantly changed the fatigue strength of the SP specimens.