Dynamic characteristics of rotor-ball bearing system with multi coupling faults

To further study the mechanism of the rotor-ball bearing system with multi coupling faults，the effects of torsional stress，shear stress，gyroscopic and moment of inertia on rotating components were fully considered，Timoshenko beam elements and disk elements were used to model the finite element of a rotor system.By assembling the dynamic model of ball bearing and fault models of unbalance，misalignment，rubbing，crack and pedestal looseness，the dynamic equations of the rotor-ball bearing system with multi coupling faults were obtained.The displacement response of the rotor-ball bearing system was obtained using Runge Kutta method with variable step length，and response was analyzed using bifurcation diagrams and poincaré maps with mass speed and time-domain waveform，axis orbits，phase diagrams and frequency spectrum at the fault areas.Fault features and dynamic characteristics of the system were studied and explored.As a result，abundant nonlinear phenomena such as periodic motion，quasi-periodic motion and complex quasi-chaotic motion were found.Additionally，characteristics of faults such as unbalance，misalignment，rubbing，crack and pedestal looseness were indicated during each nonlinear behavior.