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Estimating the film thickness in a grease lubricated bearing in the post-churning phase is complex because of the prevalent starved lubrication conditions. In our earlier work, we showed that the relative film thickness ( h g / h f f ) in an axially loaded 6209 deep groove ball bearing (DGBB) depends on the product of viscosity, load and linear speed (η b u). In this article, we present the results of experiments performed using bearings of different sizes – 6204, 6206, 6209 – and show that the relative film thickness maintains a power-law relationship with η b u , independent of the bearing size. • Level of starvation in grease-lubricated DGBBs correlate well with η b u. • The η b u concept is independent of bearing size. • Lubricant replenishment is a local phenomenon. • Starvation reduces film thickness dependency on speed. • Starvation increases film thickness dependency on load. [ABSTRACT FROM AUTHOR]

Understanding the relevance and significance of the various replenishment mechanisms in grease-lubricated bearings is very important in choosing the appropriate lubrication strategy. This study shows that the lubricant film thickness in the ball-ring contacts of a deep groove ball bearing may increase by 10%–25% due to vibrations. The possible mechanisms behind this film thickness increase are discussed. Of the proposed contact replenishment mechanisms, the micro-lateral motion of the contact edge across the tracks caused by in-operation vibrations appears crucial. Results show that in the starved contacts, vibration plays a vital role in determining the film thickness. • Film thickness in grease-lubricated DGBB increases due to vibrations. • A model to predict the vibrations-induced film thickness increase is proposed. • Film replenishment appears to be due to a reciprocating curvilinear displacement. • Vibrations-induced film thickness increase depends on the contact size. [ABSTRACT FROM AUTHOR]