Reconstruction of a New Shearing Hypothesis of Liquid Film by Reverse Establishing Based on Experimental Study

doi:10.3901/JME.2022.09.107

Abstract

Abstract: Hydrostatic bearing has been widely used in precision and ultra-precision machine tool spindles due to its advantages of high precision, high stiffness, perfect vibration reduction and no wear. However, the traditional design theory of hydrostatic bearing based on the Newton shearing hypothesis of liquid film is significantly different from the real test results, so it is difficult to meet the requirements of accurate and quantitative design of hydrostatic spindle. During studying the hydrostatic spindle and keeping track of their practical application for a long time, it is found that the theoretical throttling clearance of bearings and the flow of hydrostatic spindles, which are designed according to the principle of optimal throttling ratio, are often conspicuously different from the actual adopted parameters or tested ones, and even in some cases, the difference reaches more than 40%. In order to establish a more accurate design theory of hydrostatic bearing, it is necessary to re-study its basic assumption, the Newton shear model of liquid film. The motorized spindle and the hydrostatic bearing are used as the power source and the test objects respectively, and the experimental setup of the hydrostatic bearing with 4 cavity for oil return is set up by which the bearing flow rate and other parameters are tested under different liquid film clearances, different journal surface roughness, different speeds and different oil supply pressures, then the deviation principle between the theoretical design value and the actual test value under different parameters are found. On this basis, the liquid film pressure-flow model of hydrostatic bearing with high agreement with the test results is reconstructed in reverse, and then a new model of liquid film shear of hydrostatic bearing with mathematically possible form is obtained with reverse method. Furthermore, the liquid film shear model with sliding on journal surface is selected and confirmed by interpreting the physical meanings of various new models. The work in this study has laid a model foundation for the further establishment of a new theory which can accurately design hydrostatic bearings.

Key words: hydrostatic bearing, shearing hypothesis of liquid film, model reconstruction, ultra-high precision spindle

CLC Number:

XIONG Wanli, YUAN Shuai, WU Shuang, ZHANG Hanqian, YE Ying, TANG Xiuqing. Reconstruction of a New Shearing Hypothesis of Liquid Film by Reverse Establishing Based on Experimental Study[J]. Journal of Mechanical Engineering, 2022, 58(9): 107-118.

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