Effect of contact pressure on fretting fatigue in type 316L stainless steel

The effect of contact pressure on fretting fatigue in solution-treated austenitic stainless steel was studied under load control at a stress amplitude of 180 Mpa and a stress ratio of 0.1. With an increase in contact pressure, fretting fatigue life was almost unchanged at contact pressures between 15 and 45 MPa, but it decreased drastically at contact pressures beyond 60 MPa. Frictional stress amplitude at the fretted area increased smoothly with contact pressure. It was impossible to explain the contact pressure dependence of life by the change in frictional stress amplitude. At low contact pressures, stress cocentration due to fretting damage occurred at the middle portion of fretted area and the main crack responsible for failure was initiated there. At high contact pressures, deep concavity associated with plastic deformation of the specimen under the contact of fretting pad was formed without accompanying heavy wear. The main crack was initiated at the outer edge corner of the concavity which probably acted as a notch. It was suggested that the stress concentration at the concavity edge corner played an important role in fretting fatigue at high contact pressures.