Experimental validations of elastic to plastic asperity-based models using normal indentations of rough surfaces

Many studies have presented theoretical developments on asperity deformation models for large plane on plane contacts subject to normal loading. The aim of this work is to supplement these theoretical results with experimental findings based on measurements of the indention of microgeometry under a controlled normal load. The specific device is first described and different results, obtained using three different materials (steel, brass and aluminium alloy), each with two levels of microgeometry, are discussed. Finally, these experimental determinations are compared to two models. One is the well known classical Greenwood–Williamson model and the other is a more complete model proposed in order to obtain a more complete description of the microgeometry (including radius distribution) and a more pertinent deformation of asperities (elastic to plastic deformation). As can be predicted, the more complete model provides better agreement with experimental results. But an interesting finding is that good results were obtained with the simplest GW model despite the strong hypothesis (especially elastic deformation for all asperities).