Contact mechanics of real vs. randomly rough surfaces:: A Green's function molecular dynamics study

It is commonly assumed that knowing the height auto-correlation function of two solids in contact along with their materials properties is sufficient to predict the contact pressure distribution P(p). We investigate this assumption with contact mechanics calculations that are based on quickly converging Green's function molecular dynamics. In our simulations, elastically deformable solids are pressed against a rigid substrate. Their profile is either given by experimental data or produced with random numbers such that the artificially generated height spectra ressemble that of the real profiles. Randomly rough surfaces produce Gaussian tails in the P(p)'s, while they are exponential for experimentally determined topographies. This difference, however, does not affect significantly the true contact area, which, for the given real profile is about 20% larger than that of the random surface. Both surfaces obey Persson's contact mechanics theory reasonably well. Copyright (C) EPLA, 2007.