A theoretical and experimental study on the stiffness of aerostatic thrust bearings with vacuum preloading

Gong

Proceedings of the Institution of Mechanical Engineers, Part J:

et al. 2020

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This paper puts forward a simplified FEM based on MATLAB PDE tool to investigate the static performance of aerostatic journal bearings. The pressure distribution equation is transformed into a standard elliptic equation, the boundary conditions and coefficients of the transformed equation are also confirmed by contrasting it with the standard elliptic equation. Then the effects of bearings structural parameters and external supply pressure on the film pressure distribution, load capacity and static stiffness are studied. The film pressure distribution changes significantly with the eccentricity ratio, and an eccentricity range corresponding to the optimal stiffness is also confirmed. Finally, an experimental platform with reversal structure is applied to reduce the measurement error, the maximum relative error between the results of simulation and experimental result is 11.54%.

Section: Introductionmentioning

confidence: 93%

A simplified FEM analysis on the static performance of aerostatic journal bearings with orifice restrictor

Gong

Proceedings of the Institution of Mechanical Engineers, Part J:

et al. 2020

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“…Aerostatic bearings have advantages of near-zero friction, high motion accuracy and low heat generation. 1,2 The orifice compensated aerostatic bearing, as an important type of aerostatic bearing, is widespread used in ultra-precision machine tools and ultra-precision measuring instruments. 3–6 Especially, because of its cleanroom compatibility, the orifice compensated aerostatic bearings are very suitable for optical ultra-precision cutting machines, such as ultra-precision diamond turning machines and ultra-precision fly cutting machines.…”

Section: Introductionmentioning

confidence: 99%

Improving the stiffness of the aerostatic thrust bearing by using a restrictor with multi-orifice series

Yang

Proceedings of the Institution of Mechanical Engineers, Part J:

et al. 2020

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To improve the stiffness of the orifice-type aerostatic bearing, a new construction of orifice restrictor with multiple orifices in series was proposed to enhance the restriction effect. The restriction effects of the restrictors with multiple orifices in series were studied numerically. Based on a circular aerostatic thrust bearing with a central feedhole, the effect of the bearing stiffness improved by the restrictors with multiple orifices in series was studied. The results show that the aerostatic bearing with the restrictors with multiple sub-orifices in series shows higher maximal bearing stiffness than the bearing with traditional simple orifice restrictor. For example, the maximal stiffness for aerostatic bearing with the restrictor of four sub-orifices in series is 57 N/µm, which is ∼11% larger than that of the bearing with simple orifice. With this construction, the restriction effect of the orifice restrictor can be enhanced by increasing the number of the sub-orifices, instead of decreasing the aperture of the orifice. This approach avoids the difficulty of manufacturing the orifice restrictor with too small aperture for achieving a high restriction effect. The feasibility of the restrictor with multiple sub-orifices in series proposed in this paper was verified with experimental studies.

“…Aerostatic bearings have been widely applied in ultraprecision machine tools due to their advantages of near-zero friction, high precision and cleanroom compatibility. [1][2][3][4] High stiffness is required for the aerostatic bearings used in ultra-precision machine tools. However, it is well known that aerostatic bearings usually suffer from pneumatic instability problem for increasing their stiffness.…”

Section: Introductionmentioning

confidence: 99%

Pneumatic stability analysis of single-pad aerostatic thrust bearing with pocketed orifice

Yang

Proceedings of the Institution of Mechanical Engineers, Part J:

et al. 2019

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The pneumatic hammer phenomenon and pneumatic stability of a single-pad aerostatic thrust bearing with pocked orifice were investigated numerically. A time-dependent dynamic model for pneumatic stability analysis of the bearing was established with taking the pocket volume and the mass flow difference between the pocket inlet and outlet into account. The numerical prediction indicates that the delay effect is an important reason for the pneumatic hammer phenomenon. With considering the delay effect, an in-depth explanation for the pneumatic hammer phenomenon is proposed in this paper. The air compressibility combined with the volume effect in the aerostatic bearing could lead to the delay of pocket pressure change, then resulting in the delay of bearing force change at larger film thickness region. The delay of the bearing force change at larger film thickness region causes the bearing damping to become negative at larger film thickness. The negative damping provides some energy into the aerostatic bearing system at larger film thickness and maintains vibration, which leads to the pneumatic hammer phenomenon.