Replenishment Differences in EHL Contact Lubricated by New and In-bearings-aged Grease

In-contact replenishment differences between new and aged grease are studied using ball-on-disc optical fluorescence. Three different greases were aged in rolling bearings for 30 – 50 % of their predicted life. A considerable effort is focused on fluorescence calibration, so that differences in lubricant volume can be quantified. No changes in replenishment between new and aged samples were found in one grease. The other two greases were contaminated by metal particles and iron oxide powder. Grease fluorescence was quenched by contaminants and linear relation between intensity values and film thickness did not apply for samples with heaviest contamination. Nevertheless, strong link between the degree of contamination and lubricant replenishment was found.