| Summary: | 博士 === 國立臺灣大學 === 機械工程學研究所 === 88 === The objective of this research is to investigate the nonlinear vibration of rotors subject to friction forces, in hopes that comprehension of the complex vibration due to rotor rubbing may provide important imformation for preventive maintenance. Through proper prevention measures, potential danger due to rotor rubbing may be avoided.
For the case of a rigid rotor subject to friction forces, four equations of motion are derived for the DOF. After a parameter normalization step, numerical iterative integration is performed. By adjusting various system parameters including the size and application point of the eccentric force, the pian-sien-ghu-bi, the ratio of the rotor/stator stiffnesses, damping factors, friction coefficients, and point of friction contact, changes to the system response may be observed. Dynamic characteristics of the rotor may be analyzed by observing the time, gwei-ghi plots, power spectrum, spectrum waterfall, phase space, Poincare graphs, embedded phase-space graphs, and the fractal dimension.
The amplitude of the subharmonic resonance is larger than that of synchronous resonance.Such large amplitude subharmonic resonance zchwang-tan(hit and bounce) phenomenon is a major reason for rotor muo-schwen, often resulting in machine breakdown. Yet for certain system parameters, the rotor whirl exhibits chaotic properties, and the two dimensional Poincare section is a fractal strange attractor. Such chaotic vibration is an exclusive nonlinear characteristic of the rotor rotation with existing friction between rotor and stator. Experiments are performed to validate the derived theoretical model. It is discovered that the rotor exhibits 1/2x subharmonic vibration due to rubbing, and when the rotation speed is in a certain range, rotor vibration becomes chaotic. Lastly, practical suggestions regarding rotor friction diagnosis are offered.
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