Nonlinear dynamic response of a rub-impact rod fastening rotor considering nonlinear contact characteristic

Abstract

The nonlinear dynamic characteristics of a rub-impact rod fastening rotor have been investigated in this paper. A model of the rod fastening rotor bearing system under rub-impact condition is proposed considering nonlinear contact characteristic between disks, nonlinear oil-film force, unbalance mass, etc. The equation of motion of the system has been derived by D’Alembert principle. The contact effects between disks are modeled as a flexural spring with nonlinear stiffness. The dynamic equations of motion are solved using fourth-order Runge–Kutta method. Bifurcation diagram, vibration waveform, frequency spectrum, shaft orbit and Poincare map are used to illustrate the rich diversity of the system response with complicated dynamics. The studies indicate that it is unsuitable to take the rod fastening rotor as an integral rotor in analyzing the rub-impact dynamic response of the system. The subharmonic periodic motion, multiple periodic motion, quasi-periodic motion and chaotic motion are observed in this study. Larger radial stiffness of stator will simplify the system motion and make the oil whirl weaker or even disappear at a certain rotating speed. The corresponding results can provide the guidance for the fault diagnosis of a rub-impact rod fastening rotor; meanwhile, the study may contribute to the further understanding of the nonlinear dynamic characteristics of a rub-impact rod fastening rotor.