STRIBECK AND TRACTION CURVES FOR ELLIPTICAL CONTACTS: ISOTHERMAL FRICTION MODEL

Abstract

This paper deals with the prediction of the Stribeck and traction curves, by proposing a mixed lubrication model for highly loaded elliptical contacts. The model represents an extension on the mixed lubrication model of Gelinck and Schipper and comprehends both the asperity component or the so called boundary lubrication component (BL) and the elastohydrodynamic component (EHL). The asperity component is calculated from a fully deterministic contact perspective, where an equivalent rough surface is in contact with a smooth and rigid surface. In EHL regime, the film thickness is calculated according to Nijenbanning et al. and the separation for the asperity component is derived from Johnson, with a small adaptation, which was possible due to the deterministic contact model approach. In this way, the separation is calculated from the volume conservation theory of Johnson and even if this can be negative, the film thickness remains above zero permitting the calculation of highly loaded contacts. For the traction curve calculation, an elastic-plastic approximation for BL micro-contacts as proposed by Gelinck and Schipper for line contacts is used.