Study On The Theory And Experiment Of The Porous Material's Permeability

Aerostatic bearings are widely used in precision machinery and precision measuring instruments because of its high precision, high speed and high resolution, etc. Porous air bearings show great prospects for its excellent load capacity, stiffness and stability. The permeability is the main factor effect on the performance of porous air bearing. The research on the theory and experiments of porous materials permeability are carried out in this article. These works are as follow:A square tortuous capillary model was established through mathematical modeling, theoretical analysis and experimental verification. The images of porous material surface pore were captured and processed, which demonstrate the existence of the power law relationship between the number of pores of the porous material and a pore size distribution. And the method to get the value of porous material tortuosity fractal dimension was determined.A fractal model of the porous material permeability considering slip flow was established combined square tortuous capillary model. And the model was verified by comparing experimental data with theoretical data.The surface pores of porous material were observed in different processing states such as turning, grinding, dilute nitric acid corrosion and polishing. The changing rules of permeability in different processing states were summarized. At last, the machining process and static performance testing methods of porous air bearings were detailed.A partial fractal dimension distribution spectral was obtained by calculating the number of same partial fractal dimension. It is convenient to evaluate the distribution of partial permeability of porous material. A vector was put forward to evaluate the uniform of permeability distribution. Then, the experiment equipment and process were introduced. The experiments verify the reliability of the evaluating method.The content of this paper provides a theoretical and experimental basis for the researching and manufacture of porous gas bearings, at the same time it lays foundation for the study of the permeability of porous media and its distribution.