Effect of lubricant rheology on friction in coated elastohydrodynamic lubricated contacts

This work investigates the effect of lubricant rheology on friction in coated elastohydrodynamic contacts. Two lubricants with relatively different properties are selected and two coating configurations are considered. The first coating type consists of a soft material with a low thermal inertia while the second is a hard material with a high thermal inertia. The former is known to decrease friction while the latter increases it compared to uncoated contacts. The original expectation was that the lubricant with higher P–T dependence of viscosity would exhibit higher relative friction deviation from the uncoated case. It turned out that this is only true in the linear and thermoviscous friction regimes at low and high slide-to-roll ratios, respectively.

A Study of Combined Effects of Surface Roughness and Lubricant Rheology on the Hydrodynamic Contact Behavior Using the Homogenized Method

The combined effects of surface roughness and lubricant rheology on the performance characteristics of a hydrodynamic inclined slider bearing are investigated by means of the homogenized method. The pad surface is rough and stationary while the lower surface is assumed to be smooth and moving. The V. K. Stokes couple stress fluid model is adopted to describe the rheological behavior of the lubricant flowing between the two surfaces. The numerical simulations are performed by considering three roughness patterns (transverse, longitudinal and anisotropic), and various values of the couple stress parameter. It is found that the homogenization method is rigorous and efficient for the three roughness patterns considered. It is also found that the combined effects of the surface roughness as well as the couple stress due to the presence of polymer additives on the hydrodynamic performance characteristics such as load carrying capacity, friction factor are significant.