An experimental/theoretical approach to modelling the viscous behaviour of liquid lubricants in elastohydrodynamic lubrication contacts

This paper presents an experimental/theoretical approach to modelling the viscous behaviour 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 fitted into an Eyring-based rheological model, and the model parameters are determined by minimizing the error vector associated with the curve-fitting procedures. The modelling approach is evaluated both theoretically and experimentally. The theoretical evaluation suggests that the method of modelling 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 behaviour of synthetic lubricants with various molecular structures.