An Analysis of the Deformation of Contacting Rough Surfaces : 3rd Report, Introduction of a New Contact Theory of Rough Surfaces

Abstract

The elastic and plastic deformation of plane joint lowers the static stiffness of machine tool structure. Its deformation is considered to be that of contact regions between a rough surface and a smooth one. In this report, the elastic and plastic deformation of contact regions between a directional surface asperity and a rigid flat one was theoretically analyzed. For this analysis, the following assumptions were made. (1) The projections of surface asperity are wedges and the probability density function of topography is a normal distribution. (2) The contact of rough surfaces can be replaced by that between a rough surface and a rigid flat surface and the stress acting on contacting points is equivalent to the plastic flow pressure. As a result, the depth of elastic deformation of asperity is found to be about twice the mean distance of contacting points and the computation formula coincides quantitatively with experimental data. The deformation depends on the contact surface coefficient K1 which is newly defined in this report. It is concluded that the relation between computed values of contact stress and elastic deformation is that of a straight line on a double logarithmic chart.