Study on nonlinear dynamics of a rotor-bearing system with coupled faults of crack and rub-impact

A nonlinear dynamic model is established to analyze the complicated dynamic behaviors of a rotor-bearing system with coupled faults in this paper, where the time-varying crack stiffness, rub-impact force and nonlinear oil-film force are taken into consideration. The numerical simulation focuses on the effects of crack depth on the onset of instability and nonlinear vibration responses of the rotor-bearing system by using bifurcation diagrams, largest Lyapunov exponent (LLE) and frequency spectrum. The results reveal that crack depth affects the vibration response and instability of the system within varied rotating speed. And the motion of the system with coupled faults shows strong nonlinearity and instability in high speed region. Moreover, the formation of oil-whirl is interfered by crack depth, thus, making the oil-whirl appear later. There also exists interaction among coupled multiple faults. The research discloses the worthy energy exchange phenomenon of multi-fault system, and contributes to fault diagnosis and vibration control of real rotor-bearing systems.