On the damage mechanisms of bending fretting fatigue

The bending fretting fatigue tests of 316L austenitic stainless steel, 7075 aluminum alloy, LZ50 steel and 30CrNiMo8 steel have been carried out under different bending stresses and normal contact stresses. The S–N curves of varied materials are set up accordingly, which present the shape like the Greek letter “ε” and can be divided into three running regimes similar to fretting wear. Based on the OM, SEM, EDS and TEM, the fretting fatigue damages have been analyzed in detail. The fretting wear damage mechanisms of fretting zone are abrasive wear, oxidative wear and delamination, a damage physical model in the MFR is proposed. According to the TEM results, two crack initiation mechanisms have been proposed based on different material characteristics. •The S–N curves present the shape like the Greek letter “ε”.•Abrasive wear, oxidative wear and delamination were the main damage mechanisms.•The fretting cracks initiate at the subsurface and propagate in three stages.•Two crack initiation mechanisms have been proposed.