Research On Permeability And Deformation Characteristics Of Material For Porous Aerostatic Bearings

Compared with the traditional mechanical contact bearings,aerostatic bearings are widely used in the fields of ultra-precision machining and precision measurement due to their advantages of high accuracy,low vibration,no pollution and long life.porous aerostatic bearing has high rigidity,high load-bearing capacity,and high stability as a new type of bearing in aerostatic bearings,so it is regarded as the most promising aerostatic bearing.However,there have been few studies on porous materials of restrictor so far,and the effect of porous material parameters on porous bearings is not clear,limiting the development of porous bearings.First of all,the paper studies the theoretical calculation method of the permeability coefficient of the material,optimizes the experimental measurement method of the permeability coefficient based on the material flow theory,and finally analyzes the effect of material deformation on the bearing,and provides a theoretical basis for the material selection and performance analysis of the porous bearing.The main work of the paper is summarized as follows:(1)The theoretical calculation model of permeability coefficient was established based on fractal theory.The effect of image processing on the fractal dimension is analyzed,and the selection of image size and multiples is given.The calculation methods of hole size,tortuosity and uniformity of material were proposed.Finally,the mathematical model of the permeability coefficient and the fractal dimension,the hole size and the tortuosity was established based on the fractal theory,and the permeability coefficients of four different materials were calculated.(2)The experimental calculation method for the permeability coefficient of porous materials was studied.The internal flow state of the material is analyzed based on the viscous flow and inertial flow equations of porous materials,,and a method for judging the flow state within the material is proposed.Finally,the method of experimental calculation of the permeability coefficient of the material is improved,and the validity of the theoretical calculation was verified by comparison with the calculation results of the fractal theory.(3)The influence of the material deformation on the static performance of the bearing under the flow field is studied.In this paper,the flow field and deformation field of the bearing were established based on ANSYS Workbench,the deformation of porous materials was numerically simulated under different working conditions,and the influence of material deformation on the static performance of the bearing was analyzed.In order to reduce the material deformation,this paper proposes the use of double-layer porous material as restrictor,and discusses the influence of the material thickness ratio of each layer on the bearing performance.Finally,the accuracy of numerical simulation is verified by bearing static bearing experiments.This paper provides the theoretical basis for the optimization of porous materials,performance analysis and development of porous bearings.