Research On The Effect Of Grease On Service Performance Of Bearing Under Multiple Working Conditions

High reliability and high precision advanced bearings have become the bottleneck restricting the improvement of research and development level in advanced equipment manufacturing industry in China.The properties of the grease under various working conditions play a decisive role in the vibration,high temperature and mute properties of the bearing.It is one of the most urgent problems in bearing lubrication that how detailed study the lubricating properties of bearing grease under different working conditions,and how to reveal the service performance of bearing more effectively in order to reduce the friction of bearing and achieve the anti-vibration effect,and improve the service life of bearing and the safety and reliability of equipment.However,it has theoretical and practical significance to study the characteristics under extreme working conditions to improve the service performance of bearings.Therefore,this study intends to carry out research on the effect of grease on service performance of bearings under multiple working conditions from the following aspects.The effect of grease on bearing vibration performance caused by short ?time high?temperature exposure is studied.The physical and chemical properties of lithium grease and white grease are compared and heated for a short time.Then,the bearing vibration performance is tested on a BVT-1A bearing vibration meter.At the same time,the deoiling technology of the Soxhlet extractor and scanning electron microscope were used to observe the structure of different stages of grease.The recovery performance of grease under high temperature in a short time is analyzed.Based on the limit temperature of grease,the principle of morphological change of soap fiber after short time heating is deeply studied,and combining with the theories of rheological and thixotropic of grease.The motion of base oil,soap fiber and impurity molecules are revealed.The results of bearing vibration test show that the vibration of white grease has significant changes due to the destruction of soap fiber structure and the loss of base oil,while the vibration of lithium grease has no obvious fluctuation.The infiltration of a small amount of water or oil accelerates the oxidation of white grease,and obvious flocculation and agglomeration appear.The effect of different load on bearing service performance under different recovery temperature is analyzed.Based on the theory of rolling contact and elastohydrodynamic lubrication,the lubrication model of ball bearing grease is established.The results of bearing vibration test show that before and after heating,the vibration velocities in middle frequency band of rolling bearings with lithium grease and white grease increase with the increase of preload.The effect of nano-particle modified grease on service performance of bearing is studied.Three kinds of grease with different thickener structures were prepared.Nano-CuO is used as additive to prepare the grease containing nano-particles by ultrasonic dispersion technology,and the physical and chemical properties such as cone penetration and NLGI are tested.The experimental research and mechanism of CuO nanoparticles on the friction and wear properties of three greases are discussed.According to the distribution of CuO nanoparticles in the thickener structure,considering the Hertz contact sliding model and the theory of elastohydrodynamic lubrication,the mechanism and process of the interaction between nanoparticles and thickener structure in the lubrication region under the coupling effect are reveal.The effect of nanoparticle grease on bearing vibration performance is analyzed.The analysis model of transient contact between ball bearing rolling and raceway is established,and the synergistic effect of nanoparticles and molecular groups is analyzed from the molecular level based on the lubrication state of Hertz contact zone.Finally,from the spectrum analysis of bearing vibration signal,the performance of vibration suppression characteristics in three frequency bands is analyzed.