Research On Dynamic Characteristics Of Rolling Bearing Rotor System Considering Time-varying Stiffness And Raceway Defects

As the supporting unit of rotating machinery,rolling bearings are required to have low resistance to the motion of the rotor and maintain the precise positioning and high rotation accuracy of the system.With the widespread application of rolling bearings in various fields,the influence of its time-varying stiffness and raceway defects on the dynamic performance and reliability of the rotor system is still unclear in high-end equipment.This paper takes the rolling bearing rotor system as the research object,establishes a rolling bearing dynamic model considering the time-varying stiffness and raceway defects,and analyzes the dynamic performance law of the rotor system.The main research work and conclusions are as follows:1)The time-varying stiffness model of rolling bearing considering clearance and rolling element revolution is established,and the average stiffness and stiffness amplitude change rate are used to characterize the time-varying characteristics of stiffness;the influence of the radial clearance,the number of rolling elements and the load on the time-varying stiffness of the deep groove ball bearing and the different types of bearing stiffness are analyzed.The results show that as the clearance increases,the stiffness decreases and the time-varying characteristics increase;when the number of equivalent bearing rollers is an integer,the time-varying characteristics of the bearing stiffness are most obvious.In order to reduce the time-varying characteristics of bearing stiffness,reasonable bearing structure parameters should be selected according to load and other working conditions.2)The rolling bearing stiffness model considering the time-varying stiffness and raceway defects is established,and the additional displacement caused by the defects in the bearing contact deformation is introduced.The influence of the size and location of the raceway defects on the time-varying stiffness of the bearing is analyzed.The results show that the bearing stiffness has no effect when the defect is located in the non-load-bearing area;When the defect is located in the load-bearing area,the bearing stiffness when the rolling elements pass through the defect is reduced;when the position of the defect changes from the bottom end to the non-load-bearing area,the impact on the bearing stiffness increase first and then decrease.3)Taking a rolling bearing rotor system test bench as an example,the time-varying stiffness function of the bearing is fitted by Fourier expansion,and the nonlinear dynamic model of the rolling bearing rotor system is established.Through theoretical calculations,the effects of time-varying bearing stiffness and raceway defects on the vibration response of the rolling bearing rotor system are obtained.At the same time,the dynamic performance of the rolling bearing rotor system such as modal,critical speed,unbalanced response and stability are analyzed by COMSOL Multiphysics software.The results show that the time-varying stiffness make the amplitude of the system increases significantly.The horizontal direction excites almost all frequency multiplications of the rotation frequency,and the vertical direction excites the passing frequency of the rolling elements;the raceway defect causes the amplitude and acceleration of the system to change suddenly when passing through the defect,vibration and shock are generated which affect the stability and accuracy of the system,and the defect stimulates the frequency multiplication of the defect frequency of bearing raceway.The bearing rotor system of the case has a certain stability margin,and the rated working speed is much smaller than the critical speed,which is stable and reliable when running under working conditions.4)The dynamic performance test bench for rolling bearings with combined dynamic and static loading is designed and developed,which can meet the requirements of rolling bearing performance testing under various working conditions.The vibration signals of the bearing rotor system with defective raceways are obtained by test,the results show that the fault frequency obtained by analysis is close to the theoretical value,and the vibration impact is the largest at one time fault frequency.The vibration signal of the system can be monitored to determine whether there are defects in the bearing raceway and provide data support for predictive maintenance of the rolling bearing rotor system.