Effects of Stress Ratio and Fretting Fatigue Cycles on the Formation of Fretting Fatigue Damage of Carbon Steel S45C

Fretting fatigue damage formation of carbon steel S45C has been examined using interrupted fretting fatigue tests, which consist of two-stage fatigue loading, i.e., the first stage is fatigue loading with fretting under one of the stress ratios R=-1, 0, 0.33 and 0.5, and the second stage is fatigue loading without fretting under R=0.5. The minimum number of cycles, Ncr, in the the first stage which caused rupture in the second stage was 7.5×104, and was independent of R. The damaged layer at Ncr was about one grain size, and was hardened due to the formation of fine cell structure. It was concluded that the fretting fatigue damage is formed in the early cycles of fretting fatigue, and does not depend on R.