Chaotic And Fractal Behavior Of Rotor With Faults Of Crack And Rub-impact

With the modernization of science technology and industrial development, Rotating machinery is moving in large, continuous, high-speed, light-based, centralized, automated and high-power, large load direction. Rotor system as the core of rotating machinery components, its dynamic characteristics and mechanism of failure has important theoretical and practical significance. At present, after considering several non-linear factors (non-steady-state oil-film force, non-linear rubbing force, crack, rub-impact), the dynamic behavior of rotor system is very complex and nonlinear dynamics are also more abundant.Their theoretical study of chaotic behavior can provide a strong basis for rotor fault diagnosis. In this paper, Jeffcott rotor system dynamics model with rubbing nonlinear and non-steady-state oil-film force for rotor rub-impact and crack faults is set up. To do nonlinear dynamics study for single crack fault, single rub-impact fault and their coupled fault. Considering the composite parameters'influence such as the crack depth, speed ratio, eccentricity, as well as a combination of lubricating oil viscosity, rotor weight, bearing clearance and wide-diameter ratio. The dynamic equation was solved by four-step Runge-Kutta method. The motion characteristics of the rotor system is determined according to the bifurcation diagram, the time-domain waveform, the fractal dimension of Poincare map, the trajectory of the shaft center and frequency spectrum at certain speed and axis locus. In the crack rotor system, with the increase of crack depth, quasi-periodic area is decreased but chaos and period area is increased, period-two window is advanced and widened,eccentricity has a greater influence to nonlinear rotor dynamics behavior, when it in 0.2~0.5, it has lots of chaos and fractal motion, but if it less than 0.2 and greater than 0.5, the motion become more simple, the characteristics also reflected in rub-impact rotor, as well as in crack coupled rub-impact rotor system. In rub-impact rotor system, with the speed of the impact factor increased, the increasing impact of non-linear friction, that is, the effect of rubbing strength increased, and makes periodic-three window and chaotic motion region widened significantly. Composite parameters have little effect on supports for symmetrical rub rotor system when it increased. There are obvious periodic-three window in crack rotor than crack coupled rub-impact rotor system. The results brought in theoretical references for the fault diagnosis of rotor-bearing system and safe operation of rotor system.