Dependence of the dynamic properties of elastohydrodynamic liquids on temperature and pressure (volume)

Abstract

Shear viscosity is an essential property of elastohydrodynamic lubrication (EHL) liquids. Relaxation times that govern shear dependence of viscosity, time-dependent shear response, and time-dependent bulk behaviour all scale with temperature and pressure in the same way as does the low-shear viscosity. An accurate description of the temperature, pressure, and shear dependence of viscosity has, however, been missing from EHL analysis since the very beginning of the field resulting in many invalid conclusions. In this article, a generalized version of the Stickel plot is introduced and many empirical models are placed in their relevant region of the temperature and pressure domains by showing where they belong on the Stickel plot. The models that are capable of predicting both temperature and pressure responses are discussed in terms of scaling parameters and an example of a mineral oil from the 1953 ASME viscosity report is used to demonstrate the utility of the scaling parameter models. The Stickel analysis is shown to be extremely useful in identifying the appropriate scaling function.