This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales. Among the main themes discussed were those of rough surface representations, the breakdown of continuum theories at the nano-and micro-scales, as well as multiscale and multiphysics aspects for analytical and computational models relevant to applications spanning a variety of sectors, from automotive to biotribology and nanotechnology. Significant effort is still required to account for complementary nonlinear effects of plasticity, adhesion, friction, wear, lubrication and surface chemistry in tribological models. For each topic, we propose some research directions.

Nonequilibrium molecular dynamics (NEMD) simulations have been used to examine the structure and friction of stearic acid films adsorbed on iron surfaces with nanoscale roughness. The effect of pressure, stearic acid coverage, and level of surface roughness were investigated. The direct contact of asperities was prevented under all of the conditions simulated due to strong adsorption, which prevented squeeze-out. An increased coverage generally resulted in lower lateral (friction) forces due to reductions in both the friction coefficient and Derjaguin offset. Rougher surfaces led to more liquidlike, disordered films; however, the friction coefficient and Derjaguin offset were only slightly increased. This suggests that stearic acid films are almost as effective on contact surfaces with nanoscale roughness as those which are atomically-smooth

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