Theoretical Analysis and Numerical Simulation of Dynamic Characteristics of Hydrostatic Guides for Heavy NC Machine Tool
Based on analysis of hydrostatic bearing with circular pocket, equations of static pressure, volvme pressure and squeezing pressure which influence dynamic characteristics of hydrostatic guides with rectangle pocket have been deduced. The function and their influencing factors of the three kinds pressure mentioned above are clarified. The amplitude-phase-frequency characteristics of the hydrostatic guides system have been analyzed qualitatively and quantitatively, it is indicated that the sensitive oil volume has greater effect on the stability of the guide, the volume should be reduced as small as possible while the hydrostatic guides meet the needs of the field working situation. To increasing the oil visosity properly is also helpful to improve the dynamic performance of hydrostatic guides.
FEA on the Oil Film of the Hydrostatic Slider
The design of hydrostatic slider was introduced.The pressure distribution of oil film in a hydrostatic slider was investigated.The mathematical equations of oil film pressure were deduced according to the hydro-lubrication theory and Reynolds equations.The analysis and calculating methods of the stiffness and the load capacity of oil film were presented by adopting the methods of finite element analysis(FEA).A practical sample was simulated with Marc.The contour band,curves of the pressure distribution with the load capacity and the stiffness of oil film were achieved.The numerical results indicate that it is accurate enough to meet the demand of the design.
Experimental Test Results for Four High-Speed, High-Pressure, Orifice-Compensated Hybrid Bearings
In this study, four hybrid bearings having different geometric configurations were experimentally tested for their static and dynamic characteristics, including flowrate, load capacity, rotordynamic coefficients, and whirl frequency ratio. The four bearings included a square-recess, smooth-land, radial-orifice bearing (baseline), a circular-recess bearing, a triangular-recess bearing, and an angled-orifice bearing. Each bearing had the same orifice diameter rather than the same pressure ratio. Unique to these test results is the measurement of the added mass terms, which became significant in the present tests because of high operating Reynolds numbers. Comparisons of the results were made between bearings to determine which bearing had the best performance