Influence of polymeric fluid additives in EHL rolling/sliding line contacts

The effect of polymeric fluid additives on EHL behavior of rolling/sliding line contacts is investigated numerically at low as well as high loads. The polymer-modified oil is represented by a homogeneous mixture of Newtonian base oil and power law fluid with varying concentration, viscosity ratio and power law index. The Reynolds equation incorporating the mixed rheological fluid model is derived using perturbation method. The EHL characteristics computed for polymer-modified oils are found to depend upon the effective viscosity of the lubricant mixture which is governed by the superposition of shear thinning behavior and piezo-thickening effect of the polymeric fluid additive. Since the reference viscosity of polymeric fluid additives is much higher than that of base oil, therefore, polymer-modified oils are shown to yield thicker fluid films in most of the cases. The results show a significant variation in maximum fluid pressure and minimum fluid film thickness with the volume fraction, reference viscosity ratio and power law index of the polymeric fluid additive.