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Mapping of Metallic Sliding Wear

The field of wear is so extensive and complex that it is unlikely that its jungles can be penetrated with the aid of a single map. Ashby’s map, which chose normalized load and speed as coordinates, was particularly effective in mapping the thermal eflects in wear, since frictional heating is proportional to the product of load and speed. In his paper, Dr Childs has made effective use of the ‘rigid wedge’ model of Challen and Oxley to map the regimes of abrasive wear. In so doing he has associated the wedge angle 8 with the mean slope of the hard abrasive asperities and has used it as one of the coordinates of his map. It is difficult to see how this choice of coordinate could be applied to the wear of surfaces of comparable hardness whose topography will change during sliding by the process of ‘running in’. Current research in the Engineering Department at Cambridge into the plastic deformation of surfaces in rolling and sliding contact (90) suggests an alternative model for the wear of metals of comparable hardness. A sliding asperity is modelled as a sphere moving repeatedly over the surface of a plane (Fig. 19). If the contact pressure exceeds the elastic limit of either or