A Nonlinear Dynamics Of Rolling Bearing Rotor System With Fault

In the related research of rotating machinery,the dynamics of rolling bearing-rotor system has become an important research direction of rotor dynamics.The analysis and research of its vibration characteristics have important significance in the optimization design of system related components and the reduction of bad motion state.Rolling bearing is an important supporting part of rotating machinery.The monitoring of its motion status is the key to ensure the smooth operation of mechanical equipment.Using the vibration response of rolling bearings for system fault diagnosis is the main indicator to check the running status of bearing and predict the remaining service life.It plays an important role in reducing the maintenance cost,ensuring the safety of system operation and improving the utilization rate of equipment.In this paper,six degree of freedom rolling bearing-rotor system is taken as the research object.Through the dynamic simulation of the system under different parameters,according to the bifurcation diagram,phase portraits,Poincaré map and basin of attraction,the dynamic characteristics of rolling bearing rotor system with unbalanced force and bearing failure,which provides theoretical basis for the optimal design and stable operation of rotating machinery.The main research work includes the following aspects.Firstly,taking the rolling bearing as the research object,the geometric structure and the motion relationship between the components are introduced in detail.Based on the Hertz contact theory,all solutions of two elastic bodies point contact problem are expounded,and the Hertz contact stiffness of rolling bearing is derived.Secondly,the dynamic model of the unbalanced rotor system supported by rolling bearings is considered.The variable step size Runge Kutta method is used for numerical integration to obtain the dynamic response of the rotor system.The dynamic characteristics of the system at different speeds are analyzed in detail,and the bifurcation process and chaotic evolution form of the system varying with the speed are discussed.Two key parameters of the system,bearing clearance γ and eccentricity e,are studied.Numerical simulation is carried out by using the control variable method,and the influence of each parameter change on the vibration response and safe operation of the system is analyzed.Based on the analysis of the bifurcation diagram of the system under two different conditions of growth and deceleration,the phenomena of attractor coexistence in Hopf bifurcation,jump bifurcation and doubling bifurcation are studied.By comparing the phase diagram and Poincaré map when the system parameters change,the transition process and bifurcation process of the coexisting attractor in the investigated region are studied,and the evolution law of the basin of attraction with the change of system parameters is revealed.Finally,considering the dynamic model of rolling bearing-rotor system with fault,the fatigue pitting problem of rolling bearing during service is studied.Based on Hertz contact theory,the rolling bearing model with single inner ring and outer ring fault is coupled in the original system dynamic model,and the dynamic simulation analysis is carried out according to the time history diagram to verify the bearing fault The correctness and validity of the model show that the bearing fault is an important factor to cause the vibration impact of the system,and it is also the main culprit to destroy the stable operation of the system.The study compares the effect of fault size on the system dynamics,calculates the Hertz contact force under different defects,and discusses the law of the effect of defect size on the system dynamics characteristics by analyzing the time course diagram,phase diagram and Poincaré mapping diagram.