Concepedia

Adhesion of Contacting Rough Surfaces in the Presence of Sub-Boundary Lubrication

Journal of Tribology · 1990 · 114 citations · 9 references

TL;DR

Sub‑boundary lubrication refers to the regime of extremely thin lubricant layers on contacting rough solid surfaces. The study examines how surface topography and lubricant film thickness influence adhesion and pull‑off forces. An enhanced DMT adhesion model combined with an elastoplastic contact model is employed to analyze adhesion of rough solids coated with highly adsorbing, ultra‑thin lubricant layers. The analysis predicts a roughness‑dependent critical thickness: very rough surfaces show low adhesion over a wide range of film thicknesses, whereas smooth surfaces exhibit markedly increased adhesion even for films thinner than the surface height standard deviation, potentially causing catastrophic sticking in sensitive tribological systems.

Abstract

An improved DMT adhesion model is used in conjunction with an elastoplastic contact model to analyze the adhesion of contacting rough solid surfaces covered with extremely thin layers of a lubricant having a very high affinity for the surfaces. This we call sub-boundary lubrication. The paper investigates the effects of the solid surface topography and the film thickness of the lubricant on the adhesion and pull-off forces. A roughness-dependent critical thickness phenomenon is predicted: very rough surfaces may exhibit low adhesion for a wide range of lubricant thicknesses, while for smooth surfaces adhesion may increase dramatically even for a film thickness t below the standard deviation of surface heights σ. The increased adhesion could cause the surfaces to stick together to the extent that sensitive tribological systems may be damaged.