Effect of surface dents on contact pressure in elastohydrodynamic contacts

Abstract

Nowadays film thickness measurement techniques can provide precise data for the detailed studies of the behaviour of lubricated contacts including transient operational conditions. Contact pressure is in relation with deformation of rubbing surfaces, which can be derived from experimentally evaluated film thickness. Even though the pressure distribution evaluated from measured film thickness is very sensitive to its accuracy, this approach represents a powerful tool for elastohydrodynamic pressure determination; thanks to the relative wide availability of film thickness measurement techniques. Chromatic interferograms can be captured within a few microseconds so that this approach seems to be promising in obtaining relevant pressure data even within non-smooth lubricated contacts. This article presents the results of the effort to extend the applicability of the pressure-film thickness evaluation approach to the non-smooth surfaces. It was found that the main problem is to obtain the film thickness distribution within the whole contact including the inside portion of the deep surface features (e.g. dents). That is why the combination of film thickness data and undeformed dent topography was suggested to overcome these limitations. This approach was validated through the comparison with numerical solution using dented surface and was tested on selected dented contacts operated under thin film and very thin film lubrication conditions.