Friction behavior of grease-lubricated rolling contact and its dependence on grease film under starvation

Owing to the widespread use of grease-lubricated rolling bearings, friction losses remain a significant concern. When evaluating friction behavior, ball-on-disk tribometer tests are typically conducted under fully flooded conditions, whereas the grease supplied to the contacts in a rolling bearing is often starved. This study aims to determine whether grease supply conditions affect friction behavior and to clarify the correlation between friction behavior and the grease film under starved conditions. To achieve this aim, two tribometers are used to measure friction behavior and film thickness, respectively. The results show that the friction behavior under fully flooded conditions is not representative of that under starved conditions, due to variations in film formation. Under starved conditions, the traction coefficient is more sensitive to operating conditions and depends on the thickness and both components of the grease film. • Effect of grease supply on friction is comprehensively studied • Two components in grease film are measured • Correlations between friction and grease film are clarified