08.12.21 - Franziska Stief "Shear thinning in bulk liquid of lubricants"

Shear thinning in bulk liquid of lubricants

In mechanical processes, lubrication plays a key role to protect surfaces and reduce friction and wear. Due to smaller gaps with only few molecular layers of the lubricants basing on general approaches of down-sizing, the lubricants experience extreme conditions like severe pressures and extreme shear rates. These factors cause liquid lubricants to be in extreme non-equilibrium states. In this non-equilibrium region, shear thinning occurs, an established but not entirely understood effect, where the up to that point constant Newtonian viscosity decreases rapidly with higher shear rates.

With molecular dynamics simulations the behavior of lubricants’ bulk liquid for various temperatures and pressures was simulated for an extended range of shear rates from 10^-3 to 10² ns^-1. A comparison of the shear thinning curves and different fitting models was performed and the molecular extent quantitated in consideration of the hypothesis of alignment. The status of our investigation of the origins of shear thinning within these simulated bulk liquids will be presented.