As an important part of rotating machinery, heat generation due to friction is inevitable during the rotating process of bearings. A large amount of heat causes the temperature of lubricating oil to increase, viscosity of lubricating oil to decrease, and lubricating performance decreases. Addressing the issue of inadequate lubrication between the rolling element and raceway due to increased lubricating oil temperature, this study focuses on full-ceramic ball bearings. It examines the impact of temperature fluctuations on the bearing's lubrication condition and investigates the vibration characteristics of the full-ceramic bearing. The variation in the viscosity of lubricating oil with respect to temperature is measured via a rotary viscometer. A dynamic model of the silicon nitride full-ceramic ball bearing, which considers the effects of elastohydrodynamic lubrication, is established. The impacts of changes in lubricating oil viscosity due to different temperatures on oil film pressure, oil film thickness, and bearing vibration are analyzed and then compared with experimental data. It is observed that under conditions of constant load and speed, the film thickness of the lubricating oil decreases as the viscosity decreases. Additionally, the second peak value of oil film pressure is reduced with the declining viscosity of the lubricating oil. As the viscosity decreases, the vibration of the bearing increases. The amplitude discrepancy between the simulated vibration signal and experimental vibration signal of the full-ceramic bearing is found to be less than 10%, verifying the validity of the dynamic model.

PurposePreparing CrAlN coatings on the surface of silicon nitride bearings can improve their service life in oil-free lubrication. This paper aims to match the optimal process parameters for preparing CrAlN coatings on silicon nitride surfaces, and reveal the microscopic mechanism of process parameter influence on coating wear resistance.Design/methodology/approachThis study used molecular dynamics to analyze how process parameters affected the nucleation density, micromorphology, densification and internal stress of CrAlN coatings. An orthogonal test method was used to examine how deposition time, substrate temperature, nitrogen-argon flow rate and sputtering power impacted the wear resistance of CrAlN coatings under dry friction conditions.FindingsNucleation density, micromorphology, densification and internal stress have a significant influence on the surface morphology and wear resistance of CrAlN coatings. The process parameters for better wear resistance of the CrAlN coatings were at a deposition time of 120 min, a substrate temperature of 573 K, a nitrogen-argon flow rate of 1:1 and a sputtering power of 160 W.Originality/valueSimulation analysis and experimental results of this paper can provide data to assist in setting process parameters for applying CrAlN coatings to silicon nitride bearings.

Full-ceramic ball bearings are widely used in aerospace, gas engines, and extreme working conditions. The research on vibration characteristics of full-ceramic ball bearings under different pre-tightening forces and oil supply rates is relatively rare. In this paper, silicon nitride 6206 full-ceramic deep groove ball bearing is taken as the research object, the experiment of lubrication vibration characteristics of full-ceramic bearings is carried out on a bearing vibrometer by changing different pre-tightening forces and lubricating oil supply rates with the control variable method, the dynamic model of full-ceramic deep groove ball bearing under lubrication condition is established, and the influence of factors such as lubricating oil drag force, lubricating oil film thickness, rolling friction force, and pre-tightening force on bearing vibration are analyzed in essence. The experimental results show that the large vibration ratio of the bearing in the state of lack of oil is caused by insufficient oil supply, and when the oil supply rate is too high, the rolling body is dragged by too much drag force, which leads to an obvious increase in bearing vibration. The similarity between the solution signal and the measured signal of the dynamic model of full-ceramic bearing considering the drag force of the rolling body under different lubrication conditions is over 95%, which proves the reliability and accuracy of the dynamic model.

全陶瓷球轴承广泛应用在航天航空领域、燃气发动机和极端工况下,然而针对全陶瓷轴承油润滑特性的研究比较少见.以氮化硅6206全陶瓷深沟球轴承作为研究对象,在轴承测振仪上开展陶瓷轴承润滑特性实验研究,采用拟静力学和最小油膜厚度理论通过MatLab的牛顿迭代法得到比较精确的数值解,分析陶瓷轴承的接触载荷、轴向载荷、离心力、最小油膜厚度之间的关系,并通过改变供油量和轴向载荷得到陶瓷轴承在不同工况下的振动规律.实验结果表明:在轴向载荷相同条件下球与外圈之间的接触载荷比球与内圈之间的接触载荷大,轴向位移随着轴向载荷增加呈递增趋势;在轴向载荷一定时,存在一个最佳供油量使轴承振动最小,在干摩擦条件下轴承振动随着轴向载荷增加呈先减少后增大的趋势.

Bearing as the core components of high-grade CNC machine tools, with the constant change of internal clearance of bearing wear increasingly aggravated, spindle rotation accuracy reduced. In this paper, the idea of control variable method is used to explore the dynamic change of bearing clearance from different speeds and different radial loads. Starting with the dynamic model of bearing vibration, the theoretical model of rolling bearing with five degrees of freedom is established in this paper. The interaction force between steel shaft and ceramic bearing inner ring is calculated by Runge-Kutta method with elastic wall thickness ring theory, and the reduction of radial clearance of bearing is obtained. Therefore, a dynamic model of ceramic bearing considering the extrusion force of ceramic bearing inner ring is proposed. At the same time, the vibration test of steel shaft-all-ceramic bearing is designed and carried out. The test results show that under the same load, the higher the rotating speed, the shorter the time for the bearing-rotor system to reach temperature stability, and the root mean square of ceramic bearing-rotor system is obviously reduced. At the same speed, the greater the load, the more obvious the root mean square increase of the bearing-rotor system.