Fretting wear-induced evolution of surface damage in press-fitted shaft

The evolution of surface appearance and the initiation characteristics of fretting fatigue cracks in press-fitted specimens were studied by interrupted rotating-bending fatigue tests. The results show that the distance from each fretting damage zone boundary to the contact edge changes with the number of fatigue cycles, while the wear mechanism remains unchanged. The depth and width of the fretted wear scar near the contact edge increase gradually. Fretting fatigue cracks initiate from the contact area 50-200 μm from the contact edge and appear at approximately 30% of the total fretting fatigue life. Three-dimensional finite element models with the fretted wear scars for interrupted specimens were developed to investigate the effects of fretting wear on surface damage. The models show that the wear scar induced by fretting wear is a source for changes in each fretting damage zone boundary. The stress concentration near the contact edge is reduced and the locations of the maximum values of both the Smith-Watson-Topper (SWT) and Fatemi-Socie (FS) multiaxial fatigue parameters move inward towards the contact zone because of the fretting wear. This causes the crack initiation sites to shift from the contact edge to the inner area; the initiation life increases accordingly.