Static characteristics of aerostatic porous journal bearings with a surface-restricted layer

2003 ◽  
Vol 217 (2) ◽  
pp. 125-132 ◽  
Author(s):  
S Yoshimoto ◽  
H Tozuka ◽  
S Dambara
Keyword(s):  
Porous Material ◽  
Porous Materials ◽  
Porous Metal ◽  
Journal Bearings ◽  
Static Characteristics ◽  
Aerostatic Bearing ◽  
Bearing Surface ◽  
Pneumatic Hammer ◽  
Lower Permeability ◽  
Aerostatic Bearings

Graphite porous materials have been successfully used in an aerostatic bearing. This is because graphite porous materials have a lower permeability than porous metal, which makes it possible to achieve a higher stiffness in aerostatic bearings. However, aerostatic porous bearings have a disadvantage in that they are prone to cause pneumatic hammer instability. Therefore, a restricted layer which has a permeability lower than the bulk of the porous material is usually formed on the bearing surface to avoid this instability. In this paper, the static characteristics of aerostatic porous journal bearings with a surface-restricted layer are investigated theoretically and experimentally. In addition, the effects of a surface-restricted layer on the static characteristics are discussed for two types of loads, symmetrical and coupled.

Dynamic Characteristics of Aerostatic Porous Journal Bearings With a Surface-Restricted Layer

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Yuta Otsu ◽  
Masaaki Miyatake ◽  
Shigeka Yoshimoto
Keyword(s):  
Porous Material ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Dynamic Stiffness ◽  
Porous Metal ◽  
Journal Bearings ◽  
Low Permeability ◽  
Bearing Surface ◽  
Permeability Surface ◽  
Stiffness And Damping

Aerostatic porous bearings have been successfully applied to various precision devices such as machine tools and measuring equipment to achieve a higher accuracy of motion. However, aerostatic porous bearings have a disadvantage in that they are prone to cause pneumatic hammer instability. Therefore, to avoid this instability, a surface-restricted layer that has permeability smaller than the bulk of the porous material is usually formed on the bearing surface. In this paper, the dynamic characteristics of aerostatic porous journal bearings that have a surface-restricted layer are investigated numerically and experimentally. The effects of permeability in bulk porous materials and of a surface-restricted layer on the bearing characteristics are discussed using two kinds of porous material: graphite and metal. It was confirmed that aerostatic porous metal bearings with relatively large permeability could achieve large values of dynamic stiffness and damping coefficients using a low permeability, surface-restricted layer.

Static and Dynamic Characteristics of Aerostatic Circular Porous Thrust Bearings (Effect of the Shape of the Air Supply Area)

2000 ◽  
Vol 123 (3) ◽  
pp. 501-508 ◽  
Author(s):  
S. Yoshimoto ◽  
K. Kohno
Keyword(s):  
Porous Material ◽  
Dynamic Characteristics ◽  
Thrust Bearing ◽  
Aerostatic Bearing ◽  
Bearing Surface ◽  
Static And Dynamic Characteristics ◽  
Thrust Bearings ◽  
Porous Bearing ◽  
Air Supply ◽  
Bearing Design

Recently, graphite porous material has been used successfully in an aerostatic bearing. In actual bearing design, it is often necessary to reduce the thickness of porous material to make the bearing smaller. However, a reduction in thickness results in a reduction in the strength of the porous material. In particular, when the diameter of porous material is large, it is difficult to supply the air through the full pad area of porous material because it deforms. Therefore, in this paper, two types of air supply method (the annular groove supply and the hole supply) in a circular aerostatic porous thrust bearing are proposed to avoid the deflection of the bearing surface. The static and dynamic characteristics of aerostatic porous bearing with these air supply methods are investigated theoretically and experimentally. In addition, the effects of a surface restricted layer on the characteristics are clarified.

Static Characteristics of Aerostatic Thrust Bearings With Multiple Porous Inlet Ports

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Takako Hosokawa ◽  
Kei Somaya ◽  
Masaaki Miyatake ◽  
Shigeka Yoshimoto
Keyword(s):  
Porous Material ◽  
Thrust Bearing ◽  
Liquid Crystal Display ◽  
Manufacturing Cost ◽  
Static Characteristics ◽  
Bearing Surface ◽  
Thrust Bearings ◽  
Precision Measuring ◽  
Essential Components ◽  
Precision Machine Tools

Aerostatic porous bearings have been applied successfully to various precision devices, such as precision machine tools and precision measuring equipment, to achieve higher accuracy of motion. Recently, large aerostatic porous thrust bearings have been used as essential components in a lithography machine for large liquid crystal display (LCD) glasses. Conventional aerostatic porous bearings are made of porous material that covers the whole of the bearing surface area, requiring a large piece of such material for large bearings. However, making large pieces of porous material requires the use of a large electric furnace, which is a very expensive part of the bearing's manufacturing cost. To overcome this problem, this paper proposes an aerostatic thrust bearing with multiple porous inlet ports. The proposed bearing has a number of small porous inlet ports on the bearing surface, thereby avoiding the need for large electric furnaces. The static characteristics of the proposed bearings are investigated numerically and experimentally. The results show that the proposed aerostatic thrust bearing is potentially very useful for the manufacture of large aerostatic thrust bearings, where it would have advantages over conventional aerostatic porous thrust bearings.

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

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Zhi-wei Lu ◽  
Jun-an Zhang ◽  
Bo Liu
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Bearing Capacity ◽  
Static Characteristics ◽  
Aerostatic Bearing ◽  
Balance Principle ◽  
Flow Balance ◽  
Bearing Stiffness ◽  
The Finite Difference Method ◽  
Aerostatic Bearings

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.

scholarly journals Dynamic Quality of an Aerostatic Thrust Bearing with a Microgroove and Support Center on Elastic Suspension

Mathematics ◽  
2021 ◽  
Vol 9 (13) ◽  
pp. 1492
Author(s):  
Vladimir Kodnyanko ◽  
Stanislav Shatokhin ◽  
Andrey Kurzakov ◽  
Lilia Strok ◽  
Yuri Pikalov ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Negative Impact ◽  
Aerostatic Bearing ◽  
Elastic Suspension ◽  
Variable Parameters ◽  
Aerostatic Bearings ◽  
Improved Design ◽  
Dynamic Quality ◽  
Bearing Layer

The disadvantage of aerostatic bearings is their low dynamic quality. The negative impact on the dynamic characteristics of the bearing is exerted by the volume of air contained in the bearing gap, pockets, and microgrooves located at the outlet of the feeding diaphragms. Reducing the volume of air in the flow path is a resource for increasing the dynamic quality of the aerostatic bearing. This article presents an improved design of an axial aerostatic bearing with simple diaphragms, an annular microgroove, and an elastic suspension of the movable center of the supporting disk. A mathematical model is presented and a methodology for calculating the static characteristics of a bearing and dynamic quality indicators is described. The calculations were carried out using dimensionless quantities, which made it possible to reduce the number of variable parameters. A new method for solving linearized and Laplace-transformed boundary value problems for transformants of air pressure dynamic functions in the bearing layer was applied, which made it possible to obtain a numerical solution of problems sufficient for practice accuracy. The optimization of the criteria for the dynamic quality of the bearing was carried out. It is shown that the use of an elastic suspension of the support center improves its dynamic characteristics by reducing the volume of compressed air in the bearing layer and choosing the optimal volume of the microgroove.

scholarly journals Diffuse Sound Absorptive Properties of Parallel-Arranged Perforated Plates with Extended Tubes and Porous Materials

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1091 ◽  
Author(s):  
Dengke Li ◽  
Daoqing Chang ◽  
Bilong Liu
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Porous Materials ◽  
Sound Absorption ◽  
Azimuthal Angle ◽  
Octave Band ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Perforated Plates ◽  
Absorption Performance

The diffuse sound absorption was investigated theoretically and experimentally for a periodically arranged sound absorber composed of perforated plates with extended tubes (PPETs) and porous materials. The calculation formulae related to the boundary condition are derived for the periodic absorbers, and then the equations are solved numerically. The influences of the incidence and azimuthal angle, and the period of absorber arrangement are investigated on the sound absorption. The sound-absorption coefficients are tested in a standard reverberation room for a periodic absorber composed of units of three parallel-arranged PPETs and porous material. The measured 1/3-octave band sound-absorption coefficients agree well with the theoretical prediction. Both theoretical and measured results suggest that the periodic PPET absorbers have good sound-absorption performance in the low- to mid-frequency range in diffuse field.

Development and Experimental Performance Verification of a Magneto-Aerostatic Bearing for Cartridge of Dental Handpieces

2012 ◽  
Author(s):  
Guan-Chung Ting ◽  
Kuang-Yuh Huang ◽  
Keng-Ning Chang
Keyword(s):  
High Speed ◽  
Ball Bearings ◽  
Aerostatic Bearing ◽  
Operation Conditions ◽  
Air Inlet ◽  
Efficient Performance ◽  
Aerostatic Bearings ◽  
Repulsive Forces ◽  
Radial Loading ◽  
Air Film

Bearings for high-speed rotors are the key component of dental handpieces. The friction induced by conventional ball bearings restricts its speed and reduces its efficiency. In order to significantly improve the efficiency of dental handpieces, a mini-type cartridge that integrates a turbine and a spindle with radial aerostatic bearings and axial passive magnetic bearings has been ingeniously designed and realized. Around the rotating spindle, there is a high-pressured air film built up by a pair of radial aerostatic bearings, and magnet rings are applied to create repulsive forces to axially support the rotating spindle. The high-pressured air film comes from the specifically designed separable orifice restrictors, which can be easily and precisely manufactured. Frictionless bearing effect can be achieved by aerostatic principle, and the magnetic principle is applied to create large repulsive force against the axial working force. A tri-directional air inlet is designed to reduce radial loading force of a spindle during working. The modularized form of the magneto-aerostatic bearing allows it to be easily assembled and replaced in the very compact space of a mini-type cartridge. Through analytical simulations with fluid-dynamics software (CFD) and experiments, the magneto-aerostatic bearing is optimized to bring out efficient performance in its limited space. The experiments have verified that its noise level is 15dB lower than the conventional cartridge with ball bearings, and its startup air pressure is reduced from 0.4 bar to 0.1 bar. Under the same operation conditions, the newly developed cartridge with magneto-aerostatic bearings creates twice higher speed than that of the conventional one.

Hard Materials with Tunable Porosity

MRS Bulletin ◽  
2009 ◽  
Vol 34 (8) ◽  
pp. 561-568 ◽  
Author(s):  
Jonah Erlebacher ◽  
Ram Seshadri
Keyword(s):  
Porous Materials ◽  
Self Assembly ◽  
Porous Metal ◽  
Ceramic Materials ◽  
Equilibrium Temperature ◽  
Length Scale ◽  
Porous Metals ◽  
Hard Materials ◽  
Mesoporous Zeolites ◽  
Pattern Forming

AbstractPorous metals and ceramic materials are of critical importance in catalysis, sensing, and adsorption technologies and exhibit unusual mechanical, magnetic, electrical, and optical properties compared to nonporous bulk materials. Materials with nanoscale porosity often are formed through molecular self-assembly processes that lock in a particular length scale; consider, for instance, the assembly of crystalline mesoporous zeolites with a pore size of 2–50 nm or the evolution of structural domains in block copolymers. Of recent interest has been the identification of general kinetic pattern-forming principles that underlie the formation of mesoporous materials without a locked- in length scale. When materials are kinetically locked out of thermodynamic equilibrium, temperature or chemistry can be used as a “knob” to tune their microstructure and properties. In this issue of the MRS Bulletin, we explore new porous metal and ceramic materials, which we collectively refer to as “hard” materials, formed by pattern-forming instabilities, either in the bulk or at interfaces, and discuss how such nonequilibrium processing can be used to tune porosity and properties. The focus on hard materials here involves thermal, chemical, and electrochemical processing usually not compatible with soft (for example, polymeric) porous materials and generally adds to the rich variety of routes to fabricate porous materials.

Influence of Diameter and Number of Orifice on Static Characteristics of Radial-Thrust Aerostatic Bearing

2012 ◽  
Vol 497 ◽  
pp. 78-82
Author(s):  
Fei Hu Zhang ◽  
Sheng Fei Wang ◽  
Qiang Zhang ◽  
Peng Qiang Fu
Keyword(s):  
Machine Tool ◽  
Fluid Dynamic ◽  
Load Capacity ◽  
Large Diameter ◽  
Orifice Diameter ◽  
Static Characteristics ◽  
Aerostatic Bearing ◽  
Supporting System ◽  
Manufacturing Technologies ◽  
Radial Thrust

The working performance of the spindle system is the most important factor to embody the overall performance of the machine tool. To ensure the advanced capabilities, besides the high-precision manufacturing technologies, it is mainly depending on the bearing module and the forces on the spindle. In this paper, a new strategy of the vertical spindle supporting system is presented to meet the high stiffness requirement for the aerostatic bearing. Based on the computational fluid dynamics and finite volume method, a fluid dynamic model and structure model of the large diameter incorporate radial-thrust aerostatic bearing is developed and simulated to find out the pressure distribution laws of the spindle supporting system. The grid subdivision in the direction of film thickness is paid more attentions when establishing the grid of the whole gas film. Simulation results show that this special structure of bearing module can supply enough load capacity and stiffness for the machine tool. The results also indicate that the static characteristics of the bearing are improved as the supply pressure increases and as the supply orifice diameter decreases.

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