Search Results (10)

Micro-hole aerostatic bearings have emerged as critical components in ultra-precision machining systems, offering a superior load capacity, stiffness, and stability compared to traditional orifice-based designs. These enhancements are primarily attributed to the high-density configurations of micro-holes and the reduction in hole diameter. However, research on the design and analysis of micro-hole aerostatic bearings for high-rotational-speed applications remains limited. In this study, the finite element method (FEM) was employed to solve the Reynolds equation, thereby conducting a systematic evaluation of the static and high-speed performance characteristics of micro-hole aerostatic thrust bearings. The effects of restrictor types, micro-hole layouts, structural parameters, and centrifugal deformation under high-rotational-speed conditions on bearing performance have been comprehensively examined. The objective of this study is to provide a basis for the design of micro-hole high-speed aerostatic spindles. Full article

In this study, in order to reveal the influence mechanism of bearing parameters on pneumatic hammering, an aerostatic bearing with a multi-orifice-type restrictor is analyzed. Firstly, the flow field is investigated, and the vortex-induced excitation is discussed in both the frequency and time domains. Then, the frequency-related displacement impedance is analyzed, and the effects of vortex-induced excitation on pneumatic hammering are discussed. Experiments are also conducted for verification. Moreover, the influence of damping on pneumatic hammering is identified. The results show that with larger damping, the risk of pneumatic hammering can be reduced. Finally, the impacts of design parameters on the damping are discussed in detail using an approximate model. Design optimization is considered to achieve the maximum damping, i.e., the minimum risk of pneumatic hammering. The results show that both the air supply pressure and the pocket volume should be minimized. The analysis process provides a reference for the design of bearings to reduce pneumatic hammering. Full article

Aerostatic bearings are crucial support components in ultra−precision manufacturing equipment. However, improvements in the load−carrying capability (LCC) of aerostatic bearings often lead to higher intensity nano−vibrations. This paper introduces a novel primary and secondary orifice restrictor (PSOR) designed to simultaneously enhance the LCC and mitigate nano−vibrations in aerostatic bearings. The static performance of complex turbulent flows occurring within the chamber of aerostatic bearings with PSORs was investigated. The dynamic performance of the turbulent flows was analyzed through 3D transient numerical simulation using the large eddy simulation method. The LCC and nano−vibration acceleration were measured experimentally, and the results indicated that the design of the secondary orifice diameter could enhance LCC and mitigate nano−vibrations, consistent with theoretical predictions. The accuracy of the proposed model was validated, confirming the effectiveness of PSOR. In the experiments, an aerostatic bearing with a secondary orifice diameter of 0.1 mm exhibited the lowest LCC and largest nano−vibration. Conversely, an aerostatic bearing with a secondary orifice diameter of 0.26 mm exhibited the highest LCC and weakest nano−vibration. This study provides insights into the formation mechanism of turbulent vortex and interaction mechanism among the primary orifice and secondary orifices in aerostatic bearings with a PSOR. Full article

A simplified calculation method is evaluated to calculate the static performance of an aerostatic journal bearing with multiple orifice-type restrictors. This method adopts a one-dimension flow assumption and is a fast calculation method to design journal bearings in engineering by directly linking the structural parameters and performance parameters affecting radial bearings with nonlinear equations. In addition, this method is verified with computational fluid dynamics by two actual case studies, and it is found that the LCC difference between those two methods is less than 5% for a 200 mm diameter spindle, and less than 10% for a 100 mm diameter spindle. Subsequently, the influence of a key parameter${\mathsf{\zeta }}_i$on the static performance of journal bearings is explained theoretically. This method is much easier and more intuitive compared with numerical computational methods. Furthermore, it promotes the application of aerostatic journal bearings. Full article

Aerostatic bearings are widely used in ultra-precision manufacturing equipment as a crucial support component. However, turbulent vortices in the recess can induce micro-vibration of the aerostatic bearing, which can severely affect stability. To further suppress the formation of turbulent vortices and reduce the micro-vibration, an aerostatic bearing with a square micro-hole arrayed restrictor (SMAR) was designed and the influences of structural parameters of the SMAR on its static and dynamic performance were investigated using numerical simulations and experiments. The transient flow characteristics of aerostatic bearings with different numbers and spacing of micro-holes were studied using 3D large eddy simulation (LES), and the formation mechanism of turbulent vortices and the law of turbulent interaction between adjacent micro-holes were analyzed. The static performance and micro-vibration of the aerostatic bearing were measured experimentally to verify the effectiveness of the SMAR. The results show that the formation of turbulent vortices and micro-vibrations can be effectively reduced by the optimized design of the SMAR, while the static performance of the bearing is basically unchanged. The micro-vibration decreases rapidly with the number of micro-holes ranging from 1 to 36 and remains steady with the number of micro-holes ranging from 36 to 100. The micro-vibration decreases rapidly with the spacing of micro-holes ranging from 2 d_n to 8 d_n and remains steady with the spacing of micro-holes ranging from 8 d_n to 10 d_n. This study contributes to further understanding the mechanism of turbulent vortex formation in aerostatic bearings with a SMAR. Full article

The porous aerostatic bearing is a new supporting structure that is widely used in precision and ultraprecision engineering and the aerospace and other fields. The aerostatic bearing has a good bearing capacity and static stiffness. In this work, the numerical and experimental research on the static characteristics of an aerostatic bearing based on a porous SiC ceramic membrane is presented. The porous ceramic membrane prepared by reactive sintering, with a porosity of 25.8% and a pore size of 20.55 μm, was used as the restrictor to fabricate the aerostatic bearing. It was found that the ceramics have good permeability, and the permeability coefficient reached 2.78 × 10⁻¹³ m² using permeability-test experiments. The effects of the gas-supply pressure and permeability coefficient on the static characteristics of the aerostatic bearing based on porous ceramics were analyzed using Fluent simulation calculation. When the gas-supply pressure was 0.5 MPa and the gas-film thickness was 6 μm, the static stiffness of the aerostatic bearing reached a maximum of 20.9 N/μm, while the bearing capacity was 632.5 N. The numerical results of the static characteristics of the aerostatic bearing are highly consistent with the experimental results, which verifies the accuracy of the Fluent simulation, and provides convenience for studying the static characteristics of aerostatic bearings. Full article

The definition of air resistance is nonuniform when analyzing the bearing capacity, stiffness, and stability of an orifice throttling aerostatic restrictor. In this study, a capillary tube similar to the inlet section of an aerostatic restrictor is used as the research object, and the Bernoulli equation under adiabatic conditions is established. Through an experiment, the pressure and temperature of the capillary tube inlet and outlet and the flow through the capillary tube are measured. Based on the air resistance definition, the empirical formula of the coefficient k is obtained, and the theoretical air resistance of the capillary path is calculated. The relative error between the theoretical air resistance and experimental air resistance is kept within 10%. The comparison results verify the accuracy of the air resistance theory and provide a basis for the subsequent establishment of a universal definition of air resistance. Subsequently, air resistance can be used to design aerostatic bearings and help improve their characteristics. Full article

Slide stability is key to the aerostatic guide in ultra-precise machines; thus, it has garnered plenty of attention. Macro-scale studies are commonplace, but micro- and nano-vibration issues require more attention. Microscope vibration is mainly caused by tiny changes in the fluid parameters of lubricating gas film, which is complex and has no verdict. In this case, slide-gas interaction should be considered. In this study, the widely used orifice-type restrictor was investigated for its nano-vibration performance. A Comsol finite-element-method fluid–structure interaction model was used to simulate and analyze an orifice-type restrictor, and orifice-restrictor vibration characteristics at the nanometer scale were inspected using a high-performance laser vibrometer. The results demonstrate that see-saw mode vibrations occur in the restrictors, growing stronger with increased air-supply pressure. The see-saw vibration’s axis is speculatively determined based on orifice and restrictor structures, and the vibration type is related to the number of orifices. The results also show that the vibration is random with natural frequencies at the kilohertz level. The newly provided research results are beneficial for better understanding the nano-vibrations of orifice-type restrictors. Full article

Even though the behavior of aerostatic bearings has for long been the topic of extensive research, there are still many aspects that require further investigation. Among these, the identification of the discharge coefficients is one the most crucial. This paper presents a hybrid method to identify the discharge coefficients of aerostatic bearing orifices. The method is termed as hybrid since it exploits experimental data and the equations of the analytical model of a circular and centrally fed aerostatic pad. The obtained results demonstrate the accuracy of the method. The proposed method further offers practical advantages compared to the conventional methods. Full article

The fluid–structure interaction (FSI) effect has a significant impact on the static and dynamic performance of aerostatic spindles, which should be fully considered when developing a new product. To enhance the overall performance of aerostatic spindles, a two-round optimization design method for aerostatic spindles considering the FSI effect is proposed in this article. An aerostatic spindle is optimized to elaborate the design procedure of the proposed method. In the first-round design, the geometrical parameters of the aerostatic bearing were optimized to improve its stiffness. Then, the key structural dimension of the aerostatic spindle is optimized in the second-round design to improve the natural frequency of the spindle. Finally, optimal design parameters are acquired and experimentally verified. This research guides the optimal design of aerostatic spindles considering the FSI effect. Full article