Dynamic Modeling And Nonlinear Vibration Characteristic Of Rolling Ball Bearing With Multiple Defects On Raceways

The rolling element bearings remain the kernel of the industrial rotating machines,which could lessen the rear and tear and ensure safe operation of these machines during daily operation.The interactions between bearing components are relative motion,contact and friction,thus the pits,cracks and localized defects are easy to occur on raceway surface.Moreover,the defects would produce violent vibration and abnormal noise of the machines,even uncountable economical loss.Therefore,the research on vibration characteristic of the rotor-bearing-pedestal system and vibration mechanism of rolling bearing with localized defects on raceway surface could provide theoretical guidance for condition monitoring,procedural maintenance and fault diagnosis of mechanical equipment.In this thesis,a dynamic model for rolling ball bearing with multiple defects on raceways under EHL is established,and the mathematic relationship between vibration responses and parameters of defects are analyzed,and the nonlinear vibration characteristic of faulty rolling ball bearing are studied.The main content and summary of this thesis are listed below:（1）A dynamic model for rolling ball bearing with multiple defects on raceways under EHL was established.The rotor-bearing-pedestal system was simplified by using mass-spring-damping system to describe the contact between bearing components.The comprehensive stiffness and damping coefficient and total time-varying displacement were all considered.The total time-varying displacement caused by multiple defects was derived.The friction force in load zone was computed.The dynamic equations were solved by Runge-Kutta method.The model was verified by experimental results on Machinery Fault Simulator（MFS）.（2）The functional relationships between parameters of localized defects and vibration signals were studied.The functional relationships of time interval between vibration signals in time domain and angle between defects due to multiple defects were formulated.The mathematic relationship between fault characteristic frequency and the number of defects,angle between defects were studied and mathematic function provided.The variation tendency of f _BPFO and f _BPFI of rolling ball bearing was simulated when the number of defects and angle between defects varies within a certain range.Numerical fitting of the values was utilized to derive the mathematic formulae between fault characteristic frequency and angle between defect,and the vibration mechanism of rolling ball bearing system is discussed.（3）The nonlinear vibration characteristic of faulty rolling ball bearing was studied.A nonlinear dynamic model for rolling ball bearing with localized defects was built by considering centrifugal force under high speed,unbalance force of rotor,radial clearance and nonlinear Hertz contact force.The dynamic equations are solved by numerical method.The nonlinear vibration characteristic of rolling ball bearing with and without localized defects are studied via trajectory diagram,phase diagram and Poincarémap.The results show that as the rotating speed rises,there are rich dynamic behaviors of rolling bearing system.