Non-linear characteristics of a cracked rotor-journal bearing system
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A model rotor-journal bearing system incorporating translational and rotational inertia, bending stiffness, gyroscopic moment, shear deformation, and disc imbalance is developed for investigating the various rotor-dynamic instabilities induced by the simultaneous exertion of crack breathing and bearing fluid film forces. Rich and complex non-linear behaviours displayed at different rotor speeds, relative flexibility (embodying the extent of surface crack development), and film clearances are studied employing the fundamental concept of instantaneous frequency. Acquired results show that the model system responds differently to two sources of non-linearity than to only one. The presence of surface fatigue cracks generates various prominent effects at low speeds and dominates non-linear instability response at high speeds. In addition, smaller bearing clearances are seen not only to induce smaller rotor vibration amplitude subject to cracking opening but also to bring about more bifurcations. © IMechE 2005.
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