Friction behavior of Radial Shaft Sealing Ring subjected to unsteady motion.

• Hysteresis effect of the friction force in unsteady motion is analyzed. • The Effects of acceleration sign-changes in hydrodynamic regime are examined. • Solution of the unsteady Navier-Stokes equation in the hydrodynamic regime is provided. • An improved friction model subjected to acceleration sign-changes is presented. A friction model for evaluating friction force of a Radial Shaft Sealing Ring (RSSR) in contact with the rotating shaft subjected to unsteady motion is presented. The model takes both the magnitude and the acceleration sign-changes from positive to negative into account and removes the shortcoming of the existing friction models in the sliding domain. It is shown that acceleration has a pronounced influence on the hydrodynamic regime. The results signify that hysteresis behavior exists in the boundary, mixed lubrication and hydrodynamic regimes as well as the pre-sliding domain, making the conventional Stribeck friction model unsuitable for characterization of friction behavior. To account for the hysteresis effect in the hydrodynamic regime, the model incorporates the solution of the unsteady Navier-Stokes equation that accommodates the magnitude as well as the sign change in the acceleration (and, hence, the viscous friction). In addition to the hysteresis, the results show a frictional lag when the motion starts from stick to slip. Test results are presented at low speed, and unknown parameters of the friction model are determined using an experimental test rig. [ABSTRACT FROM AUTHOR]