A study on nonlinear frequency response analysis of hydrodynamic journal bearings with external disturbances

The nonlinear vibration characteristics of hydrodynamic journal bearings with a circumferential groove are analyzed numerically in case that external sinusoidal disturbances are given to the rotor-bearing system. The cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film. The comparison of the steady state journal orbits using linear dynamic coefficients with the transient motion calculated from nonlinear analysis is performed. The frequency response functions obtained by linear and nonlinear analysis are also presented. When an external sinusoidal disturbance is applied to the bearing, the ran ge of the full film region varies periodically and it becomes smaller than that of static equilibrium state. The difference between linear and nonlinear analysis increases as the excitation amplitude or the frequency of the external disturbance increases.