Effects Of Bearing Features On Lubricant Distributions And Lubrication Behaviors

Most of the experimental studies on elastohydrodynamic lubrication are conducted on optical ball-on-disc film thickness measurement apparatus.Using this model device,the bearing lubrication mechanisms can be explored by measuring film thickness and oil reservoir patterns.However,the results are hard to reflect the real bearing performance due to the absence of bearing features e.g.,the dynamic loading,the cage,and the contact geometry.To overcome these limitations,some modifications are made to introduce the bearing features.A reciprocating mechanical unit is used to introduce cyclic loading.Two types of cages are used to match the single driving and dual driving mode respectively.The feature of contact geometry is introduced by using the arcshaped ball support and grooved glass disc.To study the synergy effect of these features on the bearing performance,a new optical full bearing was developed.The lubrication properties of the bearing under different speeds and load conditions were observed.The main studies include:(1)Under cyclic loading conditions,the variations of the oil distributions around the contact were observed with the oil amount,speed,and loading period.The results show that a close oil reservoir pattern is formed at low speeds.The dimensionless inlet distance and the side width of the oil reservoir reduce with load increase,suggesting a poor oil supply condition.At elevated speeds,the rear oil reservoir will rupture with load increase and loading period decrease.The rear reservoir will be combined again during the loading decrease.A full starvation state is obtained under high speeds and the overlap of the rolling track will improve the lubricant replenishment and lubrication state.(2)By introducing the cage to the ball-on-disc device,the cage effect on the oil reservoir pattern and oil film thickness was observed.The results show that compared to the cases without cages,the lubricant replenishment and inlet lubricant supply were obviously enhanced.The lubrication transits from starvation to a fully flooded state.The grooved cage was helpful to lubricant migration.(3)The contact geometry was introduced by using the arc-shaped ball support and grooved glass disc.The oil reservoir patterns and film thickness were observed.The influences of the arc-shaped ball support and V-shaped ball support on the lubricant distributions and the film formations were analyzed.The results show that if arc-shaped ball support was used,a slip will occur between the ball and the support,resulting in a decrease in entrainment speed and the film thickness.(4)Using an optical full-bearing device,the variations of friction torque with speed and viscosity were measured.The results show that the friction torque increases with speed and then decreases.The higher the viscosity,the larger the friction torque.The increase in contact angle will cause a decrease in lubricant replenishment and an increase in friction torque.The friction torque will increase with the lubricant supply amount in a given range.