Higher Critical Speed Research Articles

Vibrations of rotors: The effect of lubricant damping

Amplitudes of linear vibrations of a slightly unbalanced shaft, rotating on lubricated bearings near one of its critical speeds, are determined, taking into account the damping action of lubricant forces and couples on the journal movement. The analysis (carried out on the lines of earlier work by Sternlicht, Warner and others) shows that the effect of lubricant couples is never relevant in the normal range of variability of parameters. The analysis puts instead in evidence the effect of the total damping action of the lubricant and hence the importance in design of forecasts of amplitude of vibration at running speed. The attention s often limited to forecasts of critical speeds; such procedure may be misleading particularly near higher critical speeds.