Plastic smoothing of rough surfaces

When two metal blocks are squeezed together the stresses in the asperity contact regions are usually so large that the asperities deform plastically, at least at short length scales. Many tribology properties of contacts, such as the contact stiffness and the electric and thermal contact resistance, and the fluid flow at interfaces, depend on the surface topography and are hence modified by the plastic flow. Here I present a new way to obtain an effective power spectra of plastically deformed surfaces to be used in the Persson contact mechanics theory. I also present results for the surface height topography obtained using the plastically modified power spectra, and compare to the experimental results of Yusof and Ripin, who studied the influence of plastic flow on the topography for a smooth steel surface squeezed against a rough steel surface. Finally, I discuss why some surfaces after plastic deformation have similar Gaussian roughness as before plastic deformation, only with smaller roughness amplitude, while other surfaces shows very skewed roughness after plastic deformation.