Abstract
The misalignment of the coupling device is one of the most common typical faults in rotating machinery. It is noted that the misalignment of the coupling is the origin of the nonlinear vibration of the rotor system,which is further exacerbated by the combined effects of misalignment and rub-impact. This paper aims to reveal the nonlinear dynamic behavior of the misalignment-rub-impact combined rotor(MRCR) system. The equilibrium equation of MRCR system is derived by Newton’s second law, and the 4th-order Runge-Kutta method is used to solve the nonlinear equation. Moreover, the vibration mode and distribution region of the system presented in the (u,v)-two-parameter plane are obtained, which directly reflects the correlation between the vibration response of the system and the continuous change of important parameters. Furthermore, the maximum rub-impact force and duty cycle 3D cloud maps are employed to characterize the system impact’s intensity and duration ratio. The response characteristics of the system and the evolution process of the bifurcation are analyzed in detail by using two kinds of one-parameter bifurcation diagram, axis orbits, time-domain waveform, FFT spectrum diagram, Poincaré maps section and flow chart. The results indicate that the MRCR system presents complex nonlinear characteristics.In space,the rotor and stator can be in three positions: no contact, intermittent contact and full contact.The grazing bifurcation cause the number of rotor and staor impacts to increase.The misalignment fault has small effect on the dynamic behavior of the rotor system at low rotation speed. The magnitude of the misalignment change the frequency component of the system at medium and high ration speeds, significantly influencing the nonlinear dynamic behavior of the rotor system. This research will be beneficial to the fault diagnosis and design of the system in engineering.