Effect of lubricant selection on EHL performance of involute spur gears

As the gear oils usually undergo shear-thinning even in the inlet zone, an accurate EHL analysis requires realistic rheological models. This is necessary for gear oil selection so as to prevent scuffing failure. This paper demonstrates the effect of rheology on the EHL characteristics of spur gears using full transient thermal EHL simulations with Carreau shear-thinning model and Doolittleʹs free volume based pressure-viscosity relationship. The PDMS oil considered here is found to exhibit severe film thinning with 74% thinner EHL film as compared to a moderately shear-thinning PAO oil which, on the other hand, undergoes a larger thermal reduction.