Bifurcation and stability analysis by tracking energy trajectory of a bolted rotor-bearing system under multi-nonlinearity coupled effect

The rotor system is a core component of various critical machinery. When nonlinear factors such as nonlinear contact stiffness, oil-film forces, and rub-impact forces are taken into account, the rotor system exhibits considerably complex bifurcation phenomena, complicating its dynamic characteristics and stability conditions. Traditional research methods for rotor systems also have limitations in real-time monitoring of bifurcation phenomena. This paper investigates the bifurcation phenomena and stability issues of the rotor system from an energy perspective. A dynamic equation for the rotor system that considers nonlinear contact stiffness, oil-film forces, and rub-impact forces is established. The steady-state response of the rotor system is obtained using numerical analysis methods, and the relationship between bifurcation and energy transfer is analyzed. Based on theoretical analysis and experimental results, the relationships between three-dimensional energy trajectories, two-dimensional energy trajectories, and the bifurcation forms and stability of the rotor are studied. Experimental tests are conducted on a rotor test bench. The collected data is analyzed to validate the practical effectiveness and applicability of the proposed energy trajectory method in identifying actual bifurcation types in a physical system. The results demonstrate that the energy curve exhibits more detailed fluctuations compared to the smooth displacement curve during the speed-up process, confirming its capability in capturing transient dynamic behaviors. The research indicates that, compared to traditional methods, monitoring the energy transfer in the rotor system can accurately determine its bifurcation phenomena and unstable motions. These findings can be applied to condition monitoring and stability prediction of rotor systems, marking significant progress in the translation of rotor system theory into engineering applications.