Investigate The Performances Of High-speed Cylindrical Roller Bearing Based On Bearing Elements' Dynamic Unbalance

High-speed cylindrical roller bearings are used as the radial support bearings of engines such as space flight,aviation,spaceflight.In a certain extent,the performances of the engine are decided by the behaviors of the main bearings,even affect the performances of the whole machine.With the rapid progress of engine technology,the speed and the reliability requirements of shaft are increasing.The thrust-weight ratio and the service life the rolling bearings are required higher and higher,which put forward the higher requirements for the bearing's design and manufacture.The failure modes of engine spindle bearings are mostly like high-speed light load skidding and cage fracture,which cannot be effectively solved only by improving the machining accuracy of the bearing such as the roundness of bearing elements,the waviness of raceway and the surface roughness of the bearing element.The influence of the dynamic unbalance produced by bearing elements on the bearing dynamic characteristics cannot be neglected.In this paper,the high-speed cylindrical roller bearings used as the main bearing of aero engine spindle are regarded as research object,the performances of the high-speed cylindrical roller bearings based on the bearing elements' dynamic unbalance are investigated under the support of the national twelfth five-year key projects of china(JPPT-ZCGX1-1)and national natural science foundation of China(U1404514).The main contents and results in this dessertation are as following:1.The nonlinear dynamic mathematical analysis model of high-speed cylindrical roller bearings based on the bearing element' dynamic unbalance is proposed in this paper.Aiming at the roundness of the elements' dynamic unbalance in practice,the elements' dynamic unbalance is quantitatively described by a function of distance and mass.On this foundation,considering the influence of the mounting and the fitting of the bearing,the roller' convexity and the lubrication properties,the dynamic analysis model of high-speed cylindrical roller bearing considering the impact of the elements' dynamic unbalance are established,and the numerical algorithm is used to solve the nonlinear dynamic differential equations.And then,quantitative analysis of the influence of the elements' dynamic unbalance on the performances of high-speed cylindrical roller bearings is realized.2.The relationship between the bearing elements' dynamic unbalance and the performances of the high-speed cylindrical roller bearings are investigated.(1)Based on the dynamic model of high-speed cylindrical roller bearings built in this paper,the influence of roller dynamic unbalance on roller skew angle and tilt angle is analyzed,the results show that the roller's skew and tilt angle increase with the increase of the roller dynamic unbalance.(2)The effect of roller dynamic unbalance on the stability of cage are studied by means of the cage orbits and its Poincaré maps and the speed deviation ratio of the cage.The results show that when the roller dynamic unbalance exceeds a threshold,the cage motion state changes from quasi-periodic into chaotic state and the cage instability increases.Roller dynamic unbalance changes on the angular direction of the roller axis have the most serious impact on the cage stability,followed by the radial direction and the axial direction The mathematic models describing the cage vibration of the high-speed cylindrical roller bearings are proposed which on the base of the nonlinear dynamic analysis model of cylindrical roller bearing.And then,the relationships between roller dynamic unbalance,the radial clearance of bearing,the pocket clearance of cage,the guiding land clearance,the bearing speed,the radial load and the cage vibration are investigated,respectively.The results show the roller dynamic unbalance causes the cage generate some high frequency vibration components in the frequency spectrum of the cage,and as the value of the roller dynamic unbalance increases,the high frequency amplitude increases as well.The researches provide theoretical basis for improving the stability of cage and decreasing the noise of bearings.(3)The influence of cage dynamic unbalance only in radial direction of cage and the axial excursion of cage dynamic unbalance on the stability of cage,the cage slipping ratio,the skew degree of cage is studied,respectively.The previous results calculated by the computer program ADORE are used to demonstrate the accuracy of the cage dynamic unbalance analysis model built in this paper.It is can be concluded that the cage dynamic unbalance analysis model established in this paper is accurate and reliable.The analytical method and model can be applied by the bearing engineering designers.3.The relationship between roller dynamic unbalance and the mechanical properties of the bearing are studied.(1)The influence of roller dynamic unbalance on the instantaneous contact stress distribution between the roller and the raceway are analyzed.The results show that the edge effect of the raceway stress distribution increases with the increase of the roller dynamic unbalance.(2)The finite element analysis model of the roller and cage is established,and then the effect of roller dynamic unbalance on the cage stress distribution are studied.Meanwhile,comparing and analyzing the cage maximum stress when the roller regards as an ideal structure and with unbalance under different bearing geometric parameters and working conditions.It is pointed out that the roller dynamic unbalance changes the contact form between the roller and the cage,and then causes the cage stress increase.This results can provide theoretical support for the evaluation of the cage life.4.A mothed of static-pressure-air flotation for measuring the small-sized cylindrical roller dynamic unbalance is proposed.Accurate detection of the unbalance value of the small-sized cylindrical roller by the measuring device for the high-speed cylindrical roller bearing of the aero engine main shaft bearings set up.And then the problem of non-destructive testing of the roller dynamic unbalance is solved.5.The influence of the roller dynamic unbalance on the dynamic characteristics of cage are tested on a high-speed cylindrical roller bearing cage dynamic test rig.The reliability of the dynamic analysis model established in this paper is verified by comparing the theoretical results with the experimental results of the cage orbits and its frequency spectrum.In theory,the theoretical analysis methods for the influence of the bearing elements' dynamic unbalance on the performances of high-speed cylindrical roller bearing are presented and verified by experiments in this paper,which can provide the theoretical basis for the design and manufacture of high-speed cylindrical roller bearings.In application,the research results amend the dynamic analysis of high-speed cylindrical roller bearings and make it to play a more important role in solving the key technology of high-speed cylindrical roller bearings for the aero engine spindle.