| Due to the development of science and technology,aerospace engines,precision intelligent robots,large-scale high-end CNC machine tools,high-speed railways,rail transit and other large-scale equipment,the demands of bearing increased rapidly,which makes the design,manufacture and usage of bearings more and more demanding.The running status of rolling bearings are important to the entire mechanical equipment operating system.The quality of performance directly determines whether the entire equipment can run safely.Therefore,research and analysis of bearing performance and dynamic characteristics can provide suitable maintenance strategies and plans before mechanical equipments failure,which greatly reduces the probability of catastrophic accidents.Performance degradation and dynamics of rolling bearing were studied,which focuses on the mechanisms and trends of bearing performance degradation.The main research contents are as follows:(1)The operation rules and performance degradation mechanism of rolling bearings are studied.The stiffness,friction torque and minimum oil film thickness of rolling bearings are analyzed and calculated.The common failure modes of rolling bearings are given.Combined with the characteristics of bearing performance degradation,the degradation mechanism and operation rules of rolling bearings are revealed.(2)A monitoring model for the degradation process of rolling bearing vibration performance is studied.Firstly,obtaining bearing vibration data through normal healthy bearings,and analyze and process the data robustly to obtain eigen samples under ideal conditions.Qualitatively analyze the fuzzy equivalence coefficient between each sample data and intrinsic sample data;then the maximum entropy method is used to solve the probability density function of eigen samples.According to the Poisson counting process,the "3σ criterion" is used to obtain the frequency and probability of mutations that fall outside the eigen sample interval.Probability of variation,through quantitative analysis of the variation probability of vibration performance degradation of rolling bearings.The vibration performance variation monitoring of similar bearings can be realized by this modle so as to analyze and predict degradation trend of rolling bearing vibration performance.It’s useful for rolling bearings to arrange intervention measures and appropriate maintenance measures before bearing performance deteriorates.(3)The dynamic model of the internal impact caused by the lubrication effect and bearing defects is established.Starting from the motion state of the rolling element,the additional displacement introduced by the peeling defect of outer race of the rolling bearing and the impact of the rolling element through the peeling area are fully considered in order to obtain time-varying displacement excitation function caused by spalling.An impact force formula including the ratio between the length of the spalling area and the rolling element diameter is given.The driving force for the spalling defect and lubrication effect of the ball bearing outer raceway considering the impact force is established,and the simulation signal of the fault is compared with the measured signal of the outer ring fault,which verifies that the dynamic model considering the internal defect impact force and lubrication effect is correct and accurately reveal the mechanism of vibration response and make up for the shortcomings of related theories of bearing dynamic model.(4)The dynamic characteristics of a high-end CNC machine tool spindle support bearing are analyzed.ANSYS/LS-DYNA software was used to simulate the entire process of healthy bearing and outer race defect bearing from beginning to normal operation.Equivalent stress contours and stress change curves of two types of rolling bearing bearings at different moments were obtained,and the simulated speed signal and acceleration signal of the spindle support bearing are extracted.From the stress change curves of the components of the two types of bearings,we can see that the defective bearing of the outer race defect will change the stress distribution of the bearing,and fatigue damage will easily occur at the bearing defect.The dynamic characteristics of normal healthy bearings and bearings with outer race defect are analyzed separately.The results show that the dynamic characteristics of normal bearings fluctuate less,and the vibration acceleration shows a periodic change,and finally stabilizes gradually,while the defective bearing acceleration curve fluctuates greatly.with running time increaseing gradually,the acceleration fluctuations increase,the vibrations intensify,and rolling the speed of the body changes abruptly at the defect and is accompanied by slippage. |
