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Puliang Yu,Xuedong Chen,Xiaoli Wang,Wei Jiang 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
The dynamic characteristics of aerostatic bearings are critical to the performances of ultra-precision manufacturing equipment. Dynamic characteristics have recently been recognized to be significant to the dynamic stiffness of aerostatic bearings, and related research has seldom been reported up till now. In this paper, numerical simulations and experiments are carried out to investigate the influence of perturbations on the dynamic stiffness of aerostatic bearings. The thrust bearings of an aerostatic bearing spindle are selected for simulations and experiments, while the journal bearing is used as frictionless guide way. Dynamic mesh method is adopted to simulate the variation of gas film, and numerical simulations are performed by using ANSYS-Fluent-software based on the perturbation theory. Perturbations are generated via voice coil motor under different conditions in experiments. Simulations and experimental results reveal that the dynamic stiffness is much more sensitive to the perturbation frequency rather than the nanoscale perturbation amplitude. For the same amplitude of displacement perturbations, the axial stiffness coefficient increases whereas the axial damping coefficient decreases with the increase of perturbation frequency. It indicates that the dynamic stiffness of aerostatic bearings can be significantly improved by using active control of the gas film to generate perturbations with high frequency.
MULTISCALE HYDRODYNAMIC JOURNAL BEARING WITH ULTRA LOW SURFACE SEPARATION
Shaojin Shao,Yongbin Zhang,Long Chen,Xuedong Jiang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.6
When the hydrodynamic journal bearing works under excessively heavy loads, there will be the mixed hydrodynamic regime. In the local area, due to the ultra low surface separation, there is only the physically adsorbed boundary layer lubrication; in the other areas, the hydrodynamic is multiscale contributed by both the adsorbed boundary layer non-continuum flows and the intermediate continuum fluid flow. The present study first gives different governing equations respectively for different flow regimes, and then derives the film pressure and carried load of the bearing. The calculations show that in the condition of ultra low surface clearances, the boundary adsorbed layer effect normally very significantly increases the film pressure and the load-carrying capacity of the bearing, and this increase can be more than 3 orders when the fluid-bearing surface interaction is strong.