RELATIONSHIP BETWEEN NORMAL AND TANGENTIAL CONTACT STIFFNESS OF NOMINALLY FLAT SURFACES

A study of the static frictionless contact between two elastic bodies having nominally flat surfaces is made. The normal and tangential contact stiffnesses between these two elastic bodies are determined by measuring the system's natural frequencies under the effect of different values of normal load. The theoretical analysis has been carried out to compute the contact stiffness between flat surfaces from profile measurements using the theories of Greenwood and Williamson and Onions and Archard. Comparison of the calculated values, based on these theories, with the experimental data shows good agreement. It is found that the ratio between the normal and tangential contact stiffness is constant and is merely a function of the Poisson's ratio of the contact surfaces.