The Study On Hydrostatic Bearing System Dynamic Performance

The Hydrostatic Bearing is a very important technology in modern industrialproduction, it has been widely applied to machinery manufacturing especially in thehigh-precision, high efficiency, heavy and super heavy-duty machine tools. The mainperformance indicators of Hydrostatic Bearing is the Film stiffness and Bearingcapacity, one of the core technologies of Hydrostatic Bearing Technology is theQuantitative Analysis and Calculation of the oil film bearing capacity, stiffness andstability. In order to ensure the great movement precision and low flatness ofhydrostatic guide way under different loadings, we need to control the hydrostaticbearing oil film, therefore it is very important to do research on the oil filmperformance, including the Theoretical Analysis, Numerical Simulation andExperimental Studies.In this paper we do some research on the analysis of the performance of theHydrostatic Bearing System under different static and dynamic loadings. At first, wededuce the controlling equations of the Hydrostatic Bearing flow field under staticloading from the basic equations of fluid mechanics, analyze the effects of thenonlinear terms in the flow field characteristics oil chamber, the pressure of the oilseal edges, bearing capacity and the Oil film stiffness, then we get the dynamicequations of the Hydrostatic Bearing System under the fluctuation loadings, finallywe analyze the flow field characteristics of the Hydrostatic Bearing System underdifferent static and dynamic loadings by numerical integrated simulation.(1) The analysis of the flow field of the Hydrostatic Bearing System under staticloading by the method of theoretical research. In the case of static loading, the trendof the bearing capacity and stiffness of the edge of the seal oil decreases as the filmthickness increases, and it is nonlinear; the nonlinear term shave some effects on theflow state of the entrance of the oil chamber, such as reduce the flow velocity andincrease the scope of the impact; the nonlinear terms always impede the decline of thepressure along the radial direction; the effect to the bearing capacity and stiffnessformula caused by the nonlinear terms is always opposite to the main terms; theproportion of the nonlinear terms in the bearing capacity and stiffness increases withthe increasing of the film thickness, it can’t be ignored as it reaches a certain extent,(2) The analysis of the Hydrostatic Bearing System under the fluctuationloadings by the method of theoretical research. In the case of the fluctuation loadings,it will change into the steady state response caused by the harmonic excitation afterseveral cycles of unstable state, the steady state response has a certain delay after thesinusoidal loading with a phase of.(3)The simulation of the Hydrostatic Bearing Flow Field under static loading by the numerical simulation method, it combined with the theoretical analysis. Thevelocity of the flow field entrance is very intense, but it has a small range of influence,the other parts including oil seal edges are smooth laminar flow; the pressure of theflow field entrance has a large change, but has a small range, the pressure of the oilcavity is almost the same, and the pressure at the oil seal edges is gradually reducing.The bearing capacity is mainly influenced by the pressure changing, so the flow in theoil cavity has little influence to the bearing capacity, and the pressure changing of theoil seal edges is the main factor to the bearing capacity.(4) The simulation of the Hydrostatic Bearing Flow Field under fluctuationloading by the numerical simulation method, and it compared with the static analysis.The fluctuation loading will generate vortex in the oil cavity, then it will have a badeffect to the stability of the oil film; the fluctuation loading can affect the velocitydistribution of the flow field in the oil cavity, but it doesn’t affect the stable velocitydistribution; the velocity at the oil seal edge will fluctuate around a constant valuewhen it reach stable state. The constant value is close to the velocity distributionunder static loading; the pressure changing is very large at the oil seal edges, but thepressure changing amplitude is reducing along with the time passing, then it willfluctuate around a constant value, and the constant value is less than the pressureunder static loading.(5)Simulate the changing of the oil film thickness under different frequencyfluctuation loading by the Numerical analysis, and it compared with the theoreticalanalysis. In the case of low frequency fluctuation loading, the oil film is stable, buthas a large fluctuation range, the oil film is thick, bearing capacity is small; but in thecase of high frequency fluctuation loading, the oil film is thin, bearing capacity islarge, it has a small fluctuation range when it is stable, but the stability is poor, andeven the oil film is overwhelmed.