Dynamic Modeling And Vibration Characteristics Of Rolling Bearings With Local Defect Under Isothermal Elasto-hydrodynamic Lubrication

Rolling bearing is an important part of mechanical equipment to transmit motion and bear load.It is widely used because of its low friction property,high efficiency of transmitting energy and complete range.The surface defects of bearing parts greatly reduce the behavior in service of bearings and even affect the reliability of equipment.Therefore,speeding up the coupling research of tribology and dynamics of defective bearing can reveal the vibration response characteristics of bearing,and provide important theoretical basis for fault diagnosis and life prediction.In this thesis,the deep groove ball bearing is taken as the research object.Based on the analysis of the coupling mechanism of tribology and dynamics,the dynamic model of the defective bearing is established under the elasto-hydrodynamic lubrication(EHL),the vibration response characteristics under different working conditions are studied,and the rule and mechanism of vibration response of bearing under EHL are revealed.The main research contents and work are summarized as follows:(1)The mathematical relationships of the internal excitation factors of bearing vibration are explained.The failure types and causes of rolling bearings are introduced.The reasons why rolling elements are easy to slide under EHL condition are analyzed.The position of rolling element during the defect area and the changing characteristics of contact force are systematically described.And the mathematical relationships of internal coupling factors are established,such as time-varying displacement,nonlinear Hertz contact force and sliding friction force.(2)The analysis model of bearing stiffness and damping based on tribology and dynamics is established.The stiffness and damping model of bearing system between the rolling element,the lubricating oil film and the inner and outer raceways under EHL is simplified.The variation laws of the oil film stiffness,the comprehensive stiffness,the oil film damping and the comprehensive damping of the rolling bearing under different rotating speeds and loads are studied.The characteristics of the variation parameters of the bearing lubricating oil film under different working conditions are revealed,and the variation characteristics of the comprehensive stiffness and the comprehensive damping are analyzed.(3)The dynamic model of defective bearing under EHL is established.The excitation factors are considered,such as time-varying displacement,radial clearance,comprehensive stiffness,comprehensive damping and sliding friction.And a five degree of freedom(DOF)dynamic model of bearing with local defect under isothermal EHL is established.The dynamic equations are solved by fourth order Runge-Kutta method,and the result of model is verified by the experimental data.(4)The vibration response characteristics of bearing under different working conditions with or without friction force are studied.The influence of different speed and load of defective bearing dynamic model is studied,and the characteristics and rules of the vibration response signal under different working conditions are discussed.The internal and external excitation mechanisms of vibration response of defective bearing are revealed.And the results show that speed,load and friction force are the important coupling excitation factors which can strength the vibration response signal.