Dependence of friction coefficient on the resolution of asperities in metallic rough surfaces under cyclic loading

In this paper the friction mechanism that is developed between metallic rough interfaces with irregularities of different scales, submitted to cyclic loading is studied. The main purpose of the paper is to investigate how the resolution δn, which takes into account asperities of different scales of the rough interfaces and the intensity of the excitation, affect the friction that develops between the two surfaces. Friction is assumed to be the result of gradual plastification of the interface asperities in a metallic body with elastic-plastic behaviour. The interface of the body is described by a fractal interpolation function f with iterative regular construction, which permits the analysis of interfaces with irregularities of different scales. In the sequel, the structures resulting from the different iterations (i.e. resolutions) of the rough interface are submitted to different acceleration histories that induce forces leading to plastification of the interface asperities. The apparent dynamic friction coefficient is studied macroscopically, as the ratio between the forces that develop parallel and normal to the interface. Finally, the influence of the applied normal pressure to the friction mechanism is investigated with respect to the fractal resolution and the acceleration history of the interfaces.