Molecular Scale Slip Effects on Film Thickness and Friction in EHL Contacts
Abstract
The modern trends in lubrication aim at reducing the oil quantity in tribological applications. As a consequence, the film thickness in the contact zone can reach the order of magnitude of a few nanometers. Atomistic simulations based on the Molecular Dynamics method are used to analyze the local behavior of these severely confined films. A particular attention is paid to the occurrence of wall slip: predictive models and analytical laws are formulate d to quantify and predict this phenomenon as a function of the surface-lubricant pair or the local operating conditions in a contact interface. Then, the coupling between Molecular Dynamics simulations and macroscopic mode ls is explored. The classical lubrication theory is modified to include slip effects characterized previously. This approach is employed to study an entire contact featuring a nano-confined lubricant in its center, showing a severe modification of the film thickness and friction.