Inertia Effects in a Curved Non-Newtonian Squeeze Film

Abstract

In recent years, hydrodynamically lubricated bearings are used under increasingly severe conditions of high speed and heavy load. Owing to the friction, the temperature of the lubricating film rises under such operations and the viscosity of the lubricating oil decreases. Lubricating oils often contain sufficient additives of high molecular-weight polymers as a viscosity index improver in order to prevent viscosity variation with temperature change. Experimental evidence of rheological characteristics of polymer-thickened oils indicates that such lubricants behave as non-Newtonian viscous fluids such as pseudo-plastic fluids when the amount of additives is small. It has been confirmed that the non-Newtonian viscous behavior of polymer-thickened oils may be approximated by a cubic equation model relating the shear stress and the rate of shear (1). In the cubic equation model, the shear rate γ̇ is expressed in terms of the shear stress τ as μγ̇=τ+kτ3, where k>0 characterizes the pseudo-plastic fluid; k=0, the Newtonian fluid and k<0, the dilatant fluid, the initial viscosity μ is equal to the viscosity of the Newtonian fluid.