Stiffness Of Aerostatic Bearing Research Articles

Lubrication mechanism and characteristics of aerostatic bearing with close-spaced micro holes

Insufficient load capacity and stiffness of aerostatic bearings with traditional inherent orifices is limiting their applications. Recently, the aerostatic bearing with close-spaced micro holes (ABMH) shows the potential of performance improvement. However, its lubrication mechanism is still not clear and the static characteristics have not been comprehensively investigated. This paper applies numerical method and extends the pneumatic resistance theory from single orifice bearing to ABMH to reveal its lubrication mechanism. The results indicate that ABMH reduces the gas flow towards the high-pressure region of bearing center and impedes the pressure decrement in this area, thus resulting in the higher load capacity and stiffness. Additionally, bearing load capacity has positive relationships with total mass flow rate and exhibits similar varying trends.

Numerical and Experimental Investigation on the Performance of Backflow Channel Aerostatic Bearings with Shunt Injection

Simultaneously increasing the load capacity and stiffness of aerostatic bearings is highly significant for ultraprecision machining. To achieve this goal, this study presents a novel method of using backflow channels to divert high-pressure air from the feed pocket to the low-pressure region of the clearance. Different shunt injections are coupled at the end part of the backflow channels. The effects of distribution and structure of the shunt injections are systematically analyzed. Moreover, the experimental data are used to compare and validate the numerically predicted characteristics. Results show that the backflow channels simultaneously enlarge the high-pressure region and improve the load capacity and stiffness of the bearings. The pressure difference between the inherent orifice shunt injections is still evident, which is not beneficial in exploring the potentialities of backflow channels in terms of increasing the load capacity and stiffness of bearings. High-pressure air can be stored under the pocket orifice shunt injection to decrease the pressure difference. Slot shunt injections shaped similar to ramparts can surround the high-pressure air, resulting in a more apparent effect on decreasing the pressure difference. Finally, the load capacity, stiffness, and mass flow rate of the backflow channel bearings are evidently larger than those of pocket orifice bearings. Thus, the growing demand of mass flow rate must also be considered when using backflow channel bearings for their larger load capacity and higher stiffness.

Research and Analysis of the Static Characteristics of Aerostatic Bearings with a Multihole Integrated Restrictor

In order to further study the performance of aerostatic bearing, an aerostatic bearing with a multihole integrated restrictor was proposed in this paper. Based on the physical model of aerostatic bearings, the governing equation was established, deduced discretely, and solved numerically by the finite-difference method and flow balance principle in Cartesian coordinates. The bearing capacity and stiffness of aerostatic bearings have been analyzed, and the relevant experimental research has been carried out in this paper. The results showed that the number of orifices in the integrated restrictor had a significant effect on the bearing capacity, and the maximum bearing capacity of a nine-hole integrated throttling bearing was approximately 1.9 times greater than that of a single-hole bearing. The bearing stiffness was greatly affected by the diameter of the orifices, and the optimum bearing stiffness was determined. The corresponding gas film clearance also changed accordingly.

Design optimization of high-precision aerostatic equipment based on orifice restriction

The aerostatic lubrication model with orifice restriction is built based on finite difference method. The model is solved by combination of flux-error feedback and optimization of grids parameter. The stiffness of aerostatic bearing can be improved by reducing the diameter of the orifice, but the optimum working gas gap is reduced and the processing difficulty of surface throttle is improved. The experiments of load and stiffness are carried out on the slider (50 × 50 mm) with the diameter of orifice at 50 µm. The experimental results and theoretical calculation are in good agreement; thus, the model is verified. The structural parameter of two, three, and four orifice gas-bearings is optimized, respectively, based on the proposed model, and the optimum positions of the orifices are obtained. According to the results, the aerostatic bearing guideways, made up of optical material (K9), are manufactured by some optical ways, and the lubrication of the small gas gap is guaranteed; meanwhile, the straightness accuracy of the aerostatic bearing guideways is 0.1 µm/200 mm. The analysis result verifies that the calculation method and the aerostatic lubrication model are significant to the design of high-precision aerostatic equipment.

Numerical Simulation and Experimental Study on the Gas-Solid Coupling of the Aerostatic Thrust Bearing with Elastic Equalizing Pressure Groove

Aiming at the problem of low stiffness of aerostatic bearing, according to the principle of gas-solid coupling, this paper designs a kind of aerostatic thrust bearing with elastic equalizing pressure groove (EEPG) and investigates the effect of elastic equalizing pressure groove (EEPG) on the stiffness of aerostatic bearing. According to the physical model of the bearing, one deduces the deformation control equation of the elastic equalizing pressure groove and the control equation of gas lubrication, using finite difference method to derive the control equations and coupling calculation. The bearing capacity and stiffness of aerostatic bearing with EEPG in different gas film clearance are obtained. The calculation results show that the stiffness increased by 59%. The results of numerical calculation and experimental results have good consistency, proving the gas-solid coupling method can improve the bearing stiffness.