Effect Of Gyroscopic Effect On The Nonlinear Dynamics Of Gravity Dominant Rotor With A Growing Crack

Large-scale rotating machinery is a gravity-dominated horizontal shaft breathing cracked rotor with strong nonlinear motion characteristic.During the movement of the rotor,with the continuous development of cracks,the asymmetry of the stiffness of the shaft is gradually obvious,which changes the dynamic characteristics of the rotor system.With the continuous development of rotating machinery,the research on the nonlinear characteristics of rotor systems has greatly increased the attention in nonlinear dynamics.This paper addresses the effects of the gyroscopic effect on the nonlinear dynamics of a breathing cracked rotor.For the gravity dominant rotor,the crack growth of the high-speed cracked rotor system is considered.Based on load analysis of cross section and stress distribution of the fracture mechanics,the cracks are classified into three types.The three-dimensional gyroscopic moment model and three-dimensional stiffness model of the corresponding cracked rotor system are formed according to different types of the crack.The coupling effects of mass eccentricity,unbalance angle and gyro moment on the stiffness of the heavy-duty rotor with damage evolution are studied respectively.The nonlinear dynamics of different types cracked rotor systems are analyzed by means of both nonlinear vibration theory and numerical method.In engineering practice,the method of judging the stability according to the logarithmic decay rate of the free vibration of the system is not applicable to the analysis of the nonlinear vibration stability of the cracked rotor.An efficient numerical approach of Lyapunov exponent,Local linearization numerical Lyapunov exponential quantization algorithm(LLNLEQA),is proposed to analyze the dynamic stability of the nonlinear rotor system with the developing breathing crack.The stiffness variation law,nonlinear dynamics and the stability analysis of the high-speed rotor with three different types of cracks under the coupling of three-dimensional gyro moment,mass eccentricity and unbalance angle are obtained.