NONLINEAR VIBRATIONS AND STABILITY OF A ROTOR-BEARING SYSTEM WITH NONSYMMETRIC CLEARANCES

The nonlinear vibrations of a rotordynamic system that is subjected to nonsymmetric bearing clearance effects are considered. Particular att ention is paid to the nonstationary response that occurs during passag e through resonance. Based on an extended Jeffcott rotor model that in cludes the effects of nonsymmetric bearing clearances, the steady-stat e oscillations and their stability are also analyzed. The ''normal-loo se'' rotor stiffness condition that occurs due to the bearing clearanc e effects is modeled through a discontinuous radial stiffness model. E xpressions for the amplitude and phase-modulating functions are obtain ed. Frequency-amplitude relationships are derived. The effects of ''no rmal-loose'' rotor stiffness condition on the modulation of both the a mplitude and phase of the near-resonance vibrations, as well as the st ability of the rotor system, are systematically brought out. The effec ts of high-speed acceleration during run-up of the rotor are both qual ified and quantified. Similarly, the case of nln-down is analyzed.