A Contact Model for Rough Surfaces Separated by Nano-Particle Laden Lubricants

Conference Name: International Joint Tribology Conference
Location: LA, CA
Date: 11/2011

List of Authors:

Hamed Ghaednia, Robert L. Jackson

Abstract

Recently, the potential application of nanoparticles (NP) as lubricants additives has been the topic of growing researches. In spite, not much proper efforts over the modeling of NP in contact are reported. The focus of the model in this paper is to develop a proper methodology to consider different mechanical aspects of NP lubricant in contact of rough surfaces. The model consists of two sub models; firstly a statistical contact model for two ideally smooth surfaces in contact with NP lubricant in between is developed. No hydrodynamic effect and non rough surfaces are considered in this sub model. Sub model has been developed considering a normal Gaussian distribution for NP size and also an elastic-plastic model for single NP in contact. Also scale dependent yield strength is considered according to strain gradient theory. Second sub model deals with characterization of rough surfaces in contact. An analytical fractal based rough surface contact model is used for this purpose. Assuming NP are in contact where asperities are in contact, one can treat real area of contact from second sub model as nominal area of contact for first sub model. Using two sub models one can find contribution of both asperities and NP in contact force. Using numerical method the model has been solved for different cases. Studies over effect of surface roughness and NP size and weight fraction are carried out.