Friction and energy dissipation at the atomic scale: A review

Discussions of energy dissipation during friction processes have captured the attention of engineers and scientists for over 300 years. Why then do we know so little about either dissipation or friction processes? A simple answer is that we can not see what is taking place at the interface during sliding. Recently, however, devices such as the atomic force microscope have been used to perform friction measurements, characterize contact conditions and even describe the “worn surface.” Following these and other experimental developments, friction modelling at the atomic level - particularly molecular dynamics simulations – has brought scientists a step closer to “seeing” what takes place during sliding contact. With these investigations have come some answers and new questions about the modes and mechanisms of energy dissipation at the sliding interface. This paper will review recent results of 1) molecular dynamics and other theoretical studies that have identified modes of energy dissipation during friction processes and 2) friction experiments that have added to our understanding of dissipation processes and friction behavior. Finally, several approaches for addressing the questions of dissipation mechanisms will be presented.