Static friction in elastic adhesion contacts in MEMS

Static friction in a shearing mode can be expressed as the product of the shear strength of the interface and the real contact area. The influence of roughness on friction in elastic adhesion contact is analyzed. The effect of adhesion is included using Maugis' expansion of the Greenwood and Williamson model. Special attention is paid to low loading conditions, in which the number of contact points is small and the statistical models fail. A discrete contact model is proposed for this regime. The models are used to analyze friction experiments in a MEMS friction meter. The measured friction force as a function of the load can be explained by the discrete contact model, assuming three contact points