The Effect of Lubricant Elasticity on Journal Bearing Performance under Static Load

This paper presents experimental measurements of oil film thickness for a statically loaded journal bearing with single-grade, polymer-free engine oils and SAE 10W40 polymer-containing engine oils under hydrodynamic lubrication conditions.

Measured minimum film thickness was correlated with a bearing Sommerfeld number based on actual high shear rate viscosities with no significant difference being observed between polymer-free and polymer-containing oils. However, a significant decrease in bearing attitude angle was observed for a number of polymer-containing oils compared with polymer-free oils at the same Sommerfeld number.

Using measured values for eccentricity, attitude angle and high shear rate viscosities, the total friction couple was calculated at various Sommerfeld numbers with no difference being found between polymer-containing and polymer-free oils. This was expected since theoretically the contribution to friction due to attitude angle is small compared with that due to viscosity.