Amplitude reduction of small-amplitude waviness in transient elastohydrodynamically lubricated line contacts

Abstract

By means of numerical simulations the amplitude reduction of waviness in a transient elastohydrodynamically lubricated line contact is investigated as a function of slip, under conditions representative of a highly loaded (piezoviscous) situation. Firstly, the case of waviness on one of the surfaces is investigated. It is shown that the behaviour of the deformed amplitude as a function of the sliding velocity can be traced back to the variations in the mass flow induced by the waviness (which are forced by the squeeze term oscillations). The results are compared with recent theoretical work, showing excellent agreement. In particular, the peculiar effect of (significant) amplification of the amplitude (instead of reduction) for short wavelengths under conditions of sliding predicted in this work is confirmed by the presented results. However, for similar conditions it is almost absent if lubricant compressibility is taken into account. Secondly, waviness was assumed on both surfaces. The magnitude of the film oscillations in the centre of the contact has been monitored as a function of the sliding velocity and amplitude ratio. Again the behaviour can be traced back to the squeeze term and mass flow variations. Furthermore, it is shown that, for the conditions considered here, accurate predictions can be obtained on the basis of the results obtained for single-sided waviness. A simple formula is presented.