An experimental/theoretical approach to modeling the viscous behavior of liquid lubricants under EHL conditions

This paper presents an experimental/theoretical approach to modeling the viscous behavior of liquid lubricants under elastohydrodynamic lubrication (EHL) conditions. The main feature of the approach is that the rheological variables at a single point in the EHL contact are used rather than their global averages. The local rheological variables are calculated using first-principle theories in conjunction with experimental traction data. They are then curve-fit into an Eyring-based rheological model, and the model parameters are determined by minimizing the error vector associated with the curve-fitting procedures. The modeling approach is evaluated both theoretically and experimentally. The theoretical evaluation suggests that the method of modeling is meaningful for median-to-high loading conditions of a Hertz peak pressure above 0.8 GPa. The experimental evaluation demonstrates that the approach may be used to study the rheological behavior of synthetic lubricants with various molecular structures.