On Some Criteria Defining Fretting Wear

Based on the mechanics of discrete contact of rough surfaces of machine parts, quantitative criteria are proposed that determine the boundaries of fretting wear regimes. The physical foundation of these criteria is the ratio of the amplitude of tangential oscillatory displacements of contacting bodies and characteristic linear quantities associated with the dimensions of the real contact areas of the contacting surfaces. It is convenient to characterize fretting wear regimes using maps on which the boundaries of the areas of the corresponding regimes are shown in the coordinates: oscillation amplitude/normal contact load (or nominal contact pressure). The influence of the wear regime on the life of one of the common types of connections subject to fretting wear, namely electrical contacts, has been shown experimentally. Using a map of fretting wear regimes, the influence of the amplitude of tangential oscillations and normal load on the dependence of the contact electrical resistance on the number of oscillation cycles under different regimes was analyzed. The fundamental difference between this dependence in the fretting wear regime and in the normal reciprocating sliding of contacting surfaces is shown. The proposed criteria of fretting wear regimes and their visual representation in the form of wear regime maps allow predicting the wear mechanism of a given contact joint. Understanding the wear mechanism allows for a reasonable choice of materials for contacting parts and contact joint parameters (contact pressure, contact rigidity) to ensure the reliability of friction joints, including electrical contacts, under fretting wear conditions.