On the calculation of a dry friction coefficient

Abstract

AbstractNormal contact problems of rough surfaces have already been extensively investigated. For Gaussian surfaces, the normal force Fn is often found to be proportional to the real contact area A. Following the approach of Bowden and Tabor [1] for the tangential force Ft = τA, where τ denotes the yield shear stress of the softer surface, the friction coefficient µ = Ft/Fn , as ratio of tangential to normal force, is constant. This result is commonly used to justify Coulomb's friction law.Nevertheless, velocity dependent friction coefficients are widely used in many static and dynamic friction laws, although detailed simulative investigations on the physical background of the velocity dependence are missing. For these reasons, a halfspace simulation for rough surfaces subjected to sliding motion is presented here. The simulation includes temperature evolution as well as thermal expansion and their influence on contact forces, real contact area and friction coefficient. It is found that the frictional heat affects all of these variables and in particular leads to a velocity dependent friction coefficient.