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.