The Pressure-Viscosity Coefficient for Newtonian EHL Film Thickness With General Piezoviscous Response

There has been a long-standing need for a piezoviscous parameter, α_film, that together with the ambient viscosity, μ₀, will completely quantify the Newtonian rheology so that the film thickness for liquids that do not shear-thin in the inlet may be calculated as h = h(μ₀, α_film, ...) regardless of the details of the pressure-viscosity response. It seems that Blok’s reciprocal asymptotic isoviscous pressure, α*, has certain advantages over the conventional pressure-viscosity coefficient that is poorly suited for this purpose. The first detailed review of piezoviscous models for low pressures is provided. A simulation code that is apparently stable for all realistic pressure-viscosity response was utilized with diverse piezoviscous models and model liquids to develop a satisfactory definition of α_film that reads In the case of μ = μ₀ exp(αp), α_film = α and formulas are provided for other models.