| AVS 61st International Symposium & Exhibition | |
| Tribology Focus Topic | Thursday Sessions |
| Session TR+NS-ThM |
| Session: | Bridging Scales in Tribology |
| Presenter: | Mark Robbins, Johns Hopkins University |
| Authors: | M.O. Robbins, Johns Hopkins University L. Pastewka, Fraunhofer Institute for Mechanics of Materials IWM, Germany |
| Correspondent: | Click to Email |
Experimental surfaces typically have roughness on a wide range of length scales. This roughness greatly reduces the fraction of the area that is in intimate molecular contact and thus can contribute to friction and adhesion. The talk will first describe recent numerical calculations of elastic contact between rough surfaces with nominally flat or spherical geometries on large scales. An efficient Greens function approach allows calculations for systems with roughness on nanometer to micrometer scales to be performed with atomic resolution in the contact. Results for a wide range of geometries can be collapsed using simple scaling relations that depend on the root mean squared surface slope, sphere radius, elastic modulus, and work of adhesion. The scaling relations explain why adhesive interactions have little effect unless the surfaces are extremely smooth or soft. The traditional Fuller-Tabor model for adhesion of rough surfaces is shown to be qualitatively inconsistent with the simulations. The effect of atomic scale plasticity on contact and adhesion is surprisingly small. The talk will conclude by considering how forces in the contact area give rise to friction at larger scales.