Paper 14: The Effect of Pressure and Temperature on Some Properties of Fluids of Importance in Elastohydrodynamic Lubrication

Recent advances in the theory of elastohydrodynamic lubrication have greatly increased the demand for information on the physical properties of lubricants at high pressures. Specifically, the viscosity and density and their variation with temperature and pressure enter directly into calculations of the behaviour of lubricants in loaded contacts, whilst for some experimental techniques the dielectric constant at the appropriate conditions is also required.

This paper presents measured values of viscosity at pressures up to 15 000 lb/in² at 30°, 60° and 100°C, and of density and dielectric constant at pressures up to 50 000 lb/in² at 20° and 100°C for a series of lubricants including mineral, vegetable and synthetic oils.

The use of the Clausius-Mosotti relationship to predict dielectric constants at high pressures is shown to be unsatisfactory, and this is demonstrated by application to capacitance measurements obtained in a disc machine.