FILM THICKNESS IN STARVED EHL POINT CONTACTS

This paper presents a numerical study of the effects of inlet supply s tarvation on film thickness in EHL point contacts. Generally this prob lem is treated using the position of the inlet meniscus as the governi ng parameter; however, it is difficult to measure this in real applica tions, Thus, in this paper an alternative approach is adopted whereby the amount of oil present on the surfaces is used to define the degree of starvation. It is this property which determines both meniscus pos ition and film thickness reduction. The effect of subsequent overrolli ngs on film thickness decay can also be evaluated. In the simplest cas e a constant lubrication inlet film thickness in the Y direction is as sumed and the film thickness distribution is computed as a function of the oil available. This yields an equation predicting tile film thick ness reduction, with respect to the flooded value, from the amount of lubricant initially available on the surface, as a function of the num ber of overrollings n. However, the constant inlet film thickness does not give a realistic description of starvation for all conditions. So me experimental studies show that the combination of side flow and rep lenishment action can generate large differences in local oil supply a nd that the side reservoirs play an important role in this replenishme nt mechanism, Thus the contact centre can be fully starved whilst the contact sides remain remain lubricated, in these cases, a complete ana lysis with a realistic inlet distribution has been carried out and the numerical results agree well with experimental findings.