The Theoretical And Experimental Research Of Porous Air Bearings

Air bearings are widely used in the aeronautics and astronautics, ultra-precisionmachinery and measuring instruments. Comparing with other kinds of air bearings,porous air bearings have much higher load capacity and stiffness and superiordamping characteristics. Therefore, the porous air bearing has been an attractiveresearch area. In this paper, the porous air bearings manufactured by porous brass areintroduced and the load capacity and stiffness of porous air bearings has also beenstudied. Besides, the gas percolation of porous brass has been calculated for studyingthe characteristics of porous air bearings. The works have been done are as following.The gas percolation is an important parameter in the porous air bearings.Therefore, it is necessary to calculate the material percolation. According to thematerials used in this paper, we studied the possibility of using fractal theory tocalculate material percolation. The three dimension profile of porous materialsprovides basic information for studying the micron structure of porous materials. Also,the fractal dimension of porous materials and tortuosity dimension of pores withinmaterials have been calculated. Based on the fractal dimension and tortuositydimension, we calculated the material percolation theoretically. Finally, we comparedthe experimental and theoretical results of porous material percolation.In order to get a better understanding about the micro structure of porousmaterials, we proposed an algorithm for the porous brass since the porous brass wasconstructed by massive brass particles which were compacted after those particleswere pulled into a cylindrical vessel. We used the Matlab to simulate the structure ofparticle brass packed in the cylindrical vessel and calculated the density of porousbrass with considering the boundary and balance conditions. Analyzing the simulateresults could provide a better understanding about the porous brass.We measured the percolation of porous materials and compared the percolationafter porous materials been manufactured. By this way, we investigated the influenceof processing technology on the percolation of porous materials.The test system used to measure the load capacity of porous air bearings hasbeen developed. The working performance of porous air bearings with differentpercolation has also been studied. We used the test system to measure the load capacity of porous air bearings after grinding the surface of porous materials andinvestigated the vibration phenomenon of porous air bearings. The percolationuniformity of porous materials has significant influence on the performance of porousair bearings. Therefore, we divided two porous brass materials into small cube withthe same size, measured the percolation in the three directions of porous brass andfitted the whole percolation.The work we have done could not only provides theoretical and experimentalinformation on the application and manufacture of porous air bearings, but also bebeneficial to study and calculate the percolation and fractal dimension of porousmaterials similar to that we used in this work.