The effect of surface grooves on film breakdowns in point contacts

• Reduction of film thickness caused by grooves in point EHL contact was studied.
• Thickness reduction depends on speed by logarithmic power forming “lift-off” curve.
• Lubricant ambient viscosity has equivalent effect to speed; load has minor effect.
• Analytical description of geometry effect on “lift-off” curve was presented.
• Provided data enables rapid estimate of film breakdown caused by a groove.

Surface roughness plays an important role in transition from full to mixed elastohydrodynamic regime. One kind of features appearing on a real rough surface are grooves longer than contact diameter. It has already been reported that these grooves cause a local film reduction or a complete collapse. In this study, a ball-on-disc optical tribometer was used to quantitatively study the effect of grooves on film thickness in a point contact. It was observed that the main dependence on speed, the so-called lift-off curve, generally follows the logarithm function. The effects of build-up material, load, slide/roll ratio and groove geometry are presented. These results were fitted to the analytical description, which enables the estimation of groove effects on point contact lubrication.

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