An exploration of the elastohydrodynamic— hydrodynamic transition through film thickness measurements in rolling point contacts

Abstract

The numerical solution of the elastohydrodynamic lubrication (EHL) problem is often presented in charts where dimensionless parameters and asymptotic relationships are used. Among them, the so-called isoviscous rigid asymptote is especially interesting because it defines the transition between elastohydrodynamic and hydrodynamic regimes, or between piezoviscous—elastic and isoviscous—rigid problems, respectively. In other respects, the combination of moderate contact pressures (i.e. moderate piezoviscosity, low normal load, and/or large radii of curvature) and high viscosity and speeds (i.e. high hydrodynamic effect) is quite often found in working mechanisms, for instance in most flange contacts in roller bearings. Surprisingly, only a few papers have analysed and discussed these operating conditions. Based on experimental results obtained in the range of the Moes parameters 15< L<50 and 2< M<160 for pure rolling circular point contacts, the aim of this work is first to show how film thickness distributions are affected when the piezoviscous elastic to isoviscous rigid transition is approached. In this context, the relative values taken by the central and minimum film thicknesses will be particularly studied. The second objective is to compare our results with those predicted by elastohydrodynamic and hydrodynamic solutions for non-conformal contacts found in the literature. Finally, the exploration of mild EHL is dealt with and a former publication in which electrohydrodynamic very thin films and highly loaded thick film regimes were studied is completed.