Research On Measurement Techniques Of Key Mechanical Parameters For Reliability Assessment Of Rolling Element Bearings And Its Application

Rolling element bearings are key components of the drivetrain in the machinery.Effected by the speed,torque and internal or external excitation during the operation of the drivetrain,the fatigue failure of rolling element bearings may occur and seriously affect the safety and stability of machinery.Meanwhile,as for the high-performance rolling element bearing in the major machinery such as high-speed trains,wind turbines and advanced machine tools,China has not yet achieved a completely independent design and manufacturing.The key measurement technique required for the fatigue reliability assessment of rolling bearings is one of the weak links in the forward design and development of rolling bearings and monitoring of operating conditions in China.The technique aims to obtain the key mechanical parameters for reliability evaluation in actual service environment and to study the characteristics and mechanisms of these key parameters under different operating conditions.It is expected that the theoretical research on the fatigue reliability under complex excitation and the autonomy of rolling element bearings in China can be promoted by the technique.Therefore,how to measure the key mechanical parameters for the reliability evaluation of rolling element bearings in service has become a bottleneck problem that needs to be broken through.Focusing on the key mechanical parameters such as rolling-sliding behavior,radial and tangential contact load distribution,and friction torque,the development and application of measurement technique were studied in this dissertation.First,a series of measurement or determination methods for measuring these key mechanical parameters of the bearings in service were proposed.Some experiments were carried out to verify the effectiveness and accuracy of these methods.The developed measurement techniques include:(1)Aiming at the measurement of cage motion in rolling element bearing,a measurement technique based on strain response for cage slip ratio testing was proposed,which could be used to replace the traditional cage speed testing technique and realize the in-situ detection of cage slip ratio;(2)Focusing on the obtaining of raidial load distribution in rolling element bearings,a strain based measurement technique was developed,which realized the in-situ measurement of the radial load distribution in rolling element bearings and identified the contact load fluctuation caused by the geometric error of rollers with high accuracy.(3)Aiming at measuring friction torque of rolling element bearings under radial load,a tension wire method with multi force sensor parallel was developed,which could measure the friction torque of bearings under a wide range of applied radial load;(4)Aiming at the quantitative acquisition of tangential friction between roller and raceways,a prediction method of friction between roller and raceways based on data-model interaction was proposed.The parameters of elastohydrodynamic lubrication model were optimized by experimentally measured friction torque of rolling bearings and key mechanical parameters of reliability.It provided an effective technique for accurately and quantitatively obtaining tangential load distribution between roller and raceways in bearing components.As for the application of these measurement technique,this thesis carried out the application research of rolling element bearing component level and drivetrain system level respectively.Firstly,a comprehensive experiment system for key mechanical parameters of bearing reliability was developed.Experiment system integrated with the proposed measurement techniques for cage slip ratio,radial load distribution,friction torque and the method for determining tangential load distribution.In this way,these key reliability mechanical parameters of the bearing can be measured synchronously under various operating conditions.This comprehensive experiment system provides a new comprehensive technical platform for the comprehensive performance testing and evaluation of rolling element bearing components.Furthermore,the proposed methods were applied to measuring mechanical parameters of the bearing in high-speed train gearbox in this dissertation.The rolling-sliding behavior and contact load distribution were measured under different gear meshing conditions.The measured load spectrum of the rolling element bearing in high-speed train gearbox was compiled for the first time.Besides,the frictional force and torque between rollers and raceways in the gearbox bearing were predicted.Measurement results from the high-speed train gearbox rig test showed that:(1)The mechanical parameters of the gearbox bearing such as cage slip ratio,radial and tangential load distribution and frictional torque were affected by the gear meshing speed,torque,rotational direction and service temperature to varying degrees.(2)Three factors played significant roles in the variation of the contact load at the most loaded position within the bearing: modal vibration of the cage or shaft,radial geometrical differences among the rollers and vibration of the gearbox housing.(3)The mean value and bandwidth characteristics of the measured load spectrum of the gearbox bearing showed a non-monotonic trend varying with gear meshing speed and torque.(4)Compared with the bearing life predicted by the existing analytical model,the bearing life calculated based on the measured load spectrum was more conservative.In summary,research methods based on experiments and supplemented by simulation and theoretical models were adopted in this dissertation.In this way,the in-situ measurement methods and techniques of key mechanical parameters for the reliability evaluation of rolling element bearings in service were systematically studied.Then,the proposed techniques were successfully applied to a comprehensive experimental system of rolling bearing for multi-mechanical parameters synchronous testing and a high-speed train gearbox bearing bench test.Furthermore,the characteristics of the key mechanical parameters of rolling bearing in service were discussed comprehensively,and the influence of operating conditions such as rotational speed,external applied load and lubricant performance on the key mechanical parameters of rolling element bearing was analyzed.The relevant research results have considerable reference significance for the performance evaluation of rolling element bearings in components or drivetrains.In the future,the methods or techniques proposed by this dissertation can be applied not only to the mechanical parameters measurement of rolling element bearing products for the reliability evaluation,but also to operating state monitoring,fatigue life prediction and structural health management of the rolling element bearings in the drivetrain of major equipment.The dissertation contains a total of 122 figures,18 tables and 212 references(including the appendix part).