Waviness Deformation in Starved EHL Circular Contacts

Abstract

By means of numerical simulations the deformation of transverse and isotropic harmonic waviness in EHL circular contacts under pure rolling has been studied in relation to the lubricant supply to the contact. In earlier work the deformation of waviness under pure rolling in a fully flooded contact was shown to depend on a single non-dimensional wavelength parameter. In terms of this parameter short wavelengths deform very little. In this paper the effect of starvation on this behavior is shown. First, the steady state smooth surface problem is discussed as an introduction and as a reference problem. It is illustrated in detail how the entire film thickness level decreases with decreasing lubricant supply. Subsequently, results are presented for the time dependent problem with waviness moving through the contact under pure rolling. The relative deformed amplitude of the waviness inside the contact is shown to depend on the same non-dimensional wavelength parameter as before, but also on the degree of starvation. A smaller lubricant supply leads to a larger reduction of the waviness amplitude inside the contact. Finally, it is shown that to an acceptable accuracy the relative deformed amplitude of the starved problem can be predicted by the formula for the fully flooded problem if the generalized wavelength parameter is modified using the reduction factor of the central film thickness for the starved steady state smooth contact. For this reduction factor an accurate formula is available and as a result also for starved contacts by means of a component wise approach a crude estimate of the deformed surface micro-geometry (roughness) inside a contact can be obtained quite easily now.