Effect of Surface Texturing on Very Thin Film EHD Lubricated Contacts

Micro-dents of various depths and shapes have been produced on rubbing surfaces to find out whether there could be some operational conditions suitable for surface texturing applications in highly loaded non-conformal contacts. The significant effect of the size and shape of the micro-dents has been observed as a function of the slide-to-roll ratio. Shallow microfeatures within concentrated contact were found to increase the film thickness by supplying more lubricant to the contact under rolling/sliding conditions. However, in many cases this effect was accompanied with local film thickness reduction that even caused lubrication film breakdown under thin film lubrication conditions. Longitudinally and transversely oriented short grooves were found not to be completely suitable for the surface texturing applications from this point of view. Conversely, small circular micro-dents seem to be more promising as to their use to help to separate rubbing surfaces when a micro-textured surface is moving faster than a non-textured one and the lubrication films become very thin. Nevertheless, it would require a well-balanced design, taking into account many factors as the lubrication regime, the slide-to-roll ratio conditions, the rolling contact fatigue, the technology of surface texturing patterns creation, etc.