| AVS 61st International Symposium & Exhibition | |
| Tribology Focus Topic | Thursday Sessions |
| Session TR+NS-ThM |
| Session: | Bridging Scales in Tribology |
| Presenter: | Tristan Sharp, Johns Hopkins University |
| Authors: | T. Sharp, Johns Hopkins University L. Pastewka, Fraunhofer Institute for Mechanics of Materials IWM, Germany M.O. Robbins, Johns Hopkins University |
| Correspondent: | Click to Email |
Simulations are used to examine the static friction in model single-asperity contacts between a rigid sphere and a flat elastic substrate. The sphere radius R and the contact radius a are varied from nanometers to micrometers. First the case of commensurate contact between identical aligned surfaces with repulsive interactions is considered. For small contacts all contacting atoms move coherently and the friction coefficient µ is independent of contact radius and load. In larger contacts, interfacial slip is mediated by localized dislocations. At first µ decreases with increasing contact radius: µ ~(Ra0)1/2/a, where a0 is the nearest-neighbor spacing. At even larger contact sizes, μ begins to drop more slowly. The results are in sharp contrast to Cattaneo-Mindlin continuum theory where μ is independent of contact size. Separate simulations are performed to connect the results to the dislocation-based models of contact-size effects due to Hurtado and Kim, and Gao, which assume adhesive interactions between surfaces and find μ~(a0/a)1/2. The talk will conclude with discussions of the effect of changes in the relative alignment of crystalline axes.