Pressure-Viscosity Relationships for Elastohydrodynamics

The numerical simulation of elastohydrodynamic lubrication has evolved in terms of solution detail, speed and robustness. However, if EHL is to begin to solve practical quantitative problems involving differences among lubricants, practitioners must begin to utilize pressure-viscosity relationships in their numerical schemes that can describe real liquid response. The authors begin with the simple empiricisms that can be used to describe the pressure-viscosity response piecewise over the entire range from ambient to glass transition. Then various free volume formulations are introduced and compared. Finally, empirical expressions that can describe some essential features over the entire pressure range are presented. An example of the utility of one empirical equation is offered.