Oil Film Formation and Delamination Process on Nanostructured Surfaces in Boundary Lubrication: A Coarse-Grained Molecular Dynamics Study

Abstract

A series of coarse-grained molecular dynamics simulations was conducted to investigate the temporal evolution of frictional behaviors of lubricants between sliding nanostructured iron surfaces. Specific iron atoms were given a stronger interaction with the lubricant molecules to mimic the grain boundary surface structure. We varied the surface distance and interaction strength between grain boundary atoms and lubricants. It was found that, below the critical compressive stress, the oil film detached from the surface at first, then attached to it after some certain times due to the localized molecular rearrangement within lubricants and the enhancement of interaction between lubricants and iron surfaces. The transition times required for oil film formation and delamination both increased as it approached the critical compressive stress. Larger interaction strength increased the delamination time but barely affected the formation time.