Some Problems Of Nonlinear Dynamic On The Rotor System With Multi-Faults

With the rapid development of modern industry, the role of the rotating machinery is becoming important. As a key component of the rotating machinery, the rotor system emerges all kinds of faults frequently, such as crack, rub, looseness of pedestal and so on. Because of the influence of nonlinear gas film force, crack, rub and many other reasons, great tragedy may occur if the vibration is violent enough. So studying rotor system with multi-faults with modern nonlinear dynamic theory and rotor dynamic theory becomes one of the most popular research problems at home and abroad.This paper based on modern nonlinear dynamic theory and gas film force of the short journal bearing, Nonlinear dynamical behaviors of rotor system caused by gas film force and crack fault were studied through numerical simulations based on the combination of thought of Shooting method and Runge-Kutta method. The motion characteristics are analyzed by bifurcation diagram, phase diagram, Poincare maps and spectrum analysis. The results show that many abundant nonlinear phenomena appear in the response of the system along with the increase of rotor speed; system dynamic behaviors are more complex and appear chaos motions, and period-5 window becomes wilder along with the increase of eccentric quantum; system has emerge period-5 window in high-speed zone and becomes wider gradually with the deepening of the crack.Secondly, built the dynamic model of rotor system with the coupling faults of cracking and rub-impact and provided the equations of motion. In this model, the nonlinear gas film force, the crack and the rub impacting are considered. See about the nonlinear dynamic characteristics along with the change of rotation speed, stator stiffness and eccentric mass, and find that rotor-bearing system with coupling faults of crack and rub-impact has the similar dynamic behavior with the rotor with a single rub impacting fault at the critical speed, as a result of the force of colliding and rubbing, the stability of the system response drops, and dynamic behaviors are more abundant than those singular crack fault at the high rotation speed. When the system has coupling faults of crack and rub-impact, with crack expanding ,period-4 window becomes narrow, almost periodic and chaos region increase, system response from multi-periodic enter chaos move directly. Results show that dynamic behaviors induced by coupled faults are more complex than those singular fault, and nonlinear questions are more serious.Thirdly, based on a finite element formulation in the time domain, this method transforms the non- linear differential equations governing the dynamic behavior of rotor-bearing system into a set of non- linear algebraic equations that can be reduced and calculated by the characteristic set of Wu elimination method. The effect of stator stiffness and friction coefficient on response for rub-impact rotor system with gas film force is comprehensively analyzed.Finally, the primary work of this text has been concluded, and the problem existed and the development trend of future work has been pointed out.