Abstract: Based on a nonlinear continuum model of the flexible rotor-bearing system with rub-impact, considering some important influencing factors, the bifurcation and stability of the system periodic motion are studied by using continuation-shooting algorithm combined with the Newmark method. The change-law of the instability speed is centered on with the changes of the eccentricity of the rotor, clearance between rotor and stator, friction coefficient and the rub-impact stiffness. The results show that under small eccentricity the system loses its stability through Hopf-bifurcation, while under large eccentricity the system loses its stability through period-doubling bifurcation. The stability can be improved by reducing the clearance between rotor and stator, increasing the friction coefficient, increasing the rub-impact stiffness, because of the destruction of the formation condition of oil whirl. In addition, for the slight rub-impact, the system maintains its motion characteristics, on the contrary, the instability method and the instability speed changes markedly. The conclusions provide a theoretical reference for fault diagnoses, vibration control and stability design of the rotor-bearing system.

Key words: Bifurcation, Continuum model, Dimensionality reduction, Rub-impact, Stability, Rotor system, Stiffness varying mechanism, Vibration absorber, Vibration suppression, Permanent magnet