Thermal interactions in rolling bearings

Abstract

Rolling bearing dynamics model, based on classical differential equations of motion of bearing elements coupled with thermal interactions, is presented. While churning and drag effects are based on classical laminar and turbulent flow theories, independently measured lubricant rheology, including shear dependence of viscosity, is used to model lubricant traction. The energy equation is integrated through the lubricant film to first compute Newtonian traction with thermal effects. Viscosity dependence on shear stress is then applied to model “shear-thinning” effects. At very high contact pressure and very low slide-to-roll ratios material creep effects, where the behavior of lubricated and dry contacts is similar, are implemented, while a shear stress limit is applied at very high slide-to-roll ratios. Traction predictions for a typical contact in a traction rig show good agreement with experimental traction data. Transient heat generations are time-averaged over thermal time step to compute time-varying temperature fields in the bearing, which alter properties of bearing materials, operating bearing geometry, and rheology of the lubricant. As the transient solutions converge to stable operating temperatures, bearing heat generation approaches the expected steady-state value. Heat generation predictions for both ball and rolling bearings are in good agreement with measured experimental data.