Lubrification et frottement^*

¹ chargé de Recherche au CNRS
² Professeur Université de Poitiers, Laboratoire de Mécanique des solides, Unité de Recherche associée au CNRS

Résumé

Abstract

An important part of the Tribology is the lubrication which concerns contacts where a viscous film exists between surfaces of the bodies. For both low pressure contacts (journal or thrust bearings) and high pressure contacts (rolling bearings or gears), the different lubrication modes which can occur are presented using the Stribeck curve : three kinds of lubrication regimes may be distinguished. In the first zone, the boundary lubrication is defined as a lubrication mode in which the tribological behaviour is determined by the surface interactions between lubricant and solids (physical or chemical adsorption or chemical reaction). In the second zone, termed mixed lubrication, the load is carried out by both fluid film and mechanical contacts between the two-surfaces. In the third zone, a full fluid film separates completely the surfaces of machine elements : that regime is named hydrodynamic lubrication for the low pressure contact. The fluid film is formed by relatif motion of surfaces due to hydrodynamic effects like lubricant wedge or squeeze effect. For the high pressure contacts, that third zone is termed elastohydrodynamic lubrication : the behaviour of the thin film in concentred contact is largely dependant of the increase of viscosity with pressure and of the elastic deformations of the solids in the contact area.

The use and the preliminary selection of different kinds of lubricating systems are discussed and presented.