Investigations on Fatigue Life of Ball Pin After Laser Shock Peening

Abstract

In the present work, laser shock peening (LSP) was applied on critical areas of ball pins made of 41CrS4 steel to extend their fatigue life. The treatment introduced compressive residual stresses up to a depth of 1 mm with maximum value of −592 MPa on the ball pin surface. This led to a suppression of fretting fatigue in the conical section of the ball pin under lower stress amplitudes and overall fatigue life improvement by a factor of 2.4. After LSP, the crack propagation speed was slowed down to 0.001 μm/cycle down from 0.1 μm/cycle. At high stress amplitudes, the location of the main fatigue crack shifted into a notched part of the ball pin. The combined effect of high stress amplitude and stress concentration changed the elastic strain dominated high cycle fatigue to plastic strain dominated low cycle fatigue where the LSP treatment had no significant impact on the fatigue life.