Dynamic analysis of rotor's radial rub-impact in full degrees of freedom accounting for turborotor's non-linear clearance-excitation force

Dynamic behaviours of rotor's radial rub-impact in the presence of turborotor's non-linear clearance-excitation force are analysed by numerical simulations in all the six degrees of freedom of a rotor, which represent all the three kinds of vibrations: lateral, axial, and torsional vibrations. Results are displayed by bifurcation diagrams, waveforms, frequency spectrums, orbits, Poincare maps, and frequency waterfalls. Much more complicated dynamic behaviours are represented in these results. Compared with the case of pure rub-impact that does not involve any other non-linear elements, the stable motion regime is largely reduced, correspondingly the rotating speed threshold of rub-impact is also reduced slightly, and the complicated motion patterns appear in the early stage of rub-impact. Thick superharmonics and subharmonics emerge in axial and torsional vibrations, respectively, which are the typical characteristics of a chaotic motion. This indicates that the main motion pattern of the system is chaos. In the full range of investigated speed, the lateral vibrations nearly take on a sole synchronous component, and the axial vibration shows very rich superharmonic components, which mainly scatter in three thick superharmonic bands that approach to three fixed frequency components with their amplitudes growing as the rotating speed increases. The torsional vibration demonstrates rich subharmonics near half-time-frequency components, and the amplitudes of which increase with rotating speed. These conclusions are of great significance to the rotordynamic design and fault diagnostics of turborotor systems.