3.3.1 Morphology of fretting region
During the fretting fatigue process of the material, the fretting wear occurred on the contact surface between the specimen and the fretting pad due to contact stress and cyclic stress. Under different contact stresses, the fretting region showed different morphology. Fig.6 presents the morphology of the fretting region of 35CrMoA steel with different contact stresses under DP and SP;