| Aerostatic spindle is driven by an aerostatic bearing and driven by a motor or a turbine.It can realize high-speed precision machining,and has the characteristics of high rotation precision,small vibration,high rotation speed,etc.,and has been widely used.Further reducing the vibration of the aerostatic spindle is of great significance for improving the machining accuracy and stability.The air film formed in the operation of the aerostatic bearing not only bears the external load,but also has the effect of reducing the friction,and the micro-vibration generated by the gas flowing inside the bearing and the dynamic characteristics of the gas film under the external disturbance action are on the static piezoelectric main shaft.Swing accuracy and vibration have an important impact.Therefore,this paper focuses on the research of aerostatic bearings from the aspects of numerical simulation analysis and stability analysis.The main contents are as follows:(1)The main key technologies of the aerostatic spindle are analyzed,and the overall design scheme of the air static piezoelectric main shaft and the design parameters of the core components are determined.By simulating different eccentricity rates and different rotational speeds,the dynamic pressure effect on the bearing gas is studied.The effect of the membrane flow field,as well as the influence of eccentricity and rotational speed on the bearing capacity and stiffness of the bearing,the results lay the foundation for subsequent dynamic analysis.(2)Based on the large vortex model,the instantaneous flow of airflow in different regions was simulated by Star-ccm+ software,and the generation and variation of cyclone in the flow field were studied.The mechanism of bearing microvibration is studied from the aspects of impulse principle and pressure change.The numerical analysis is used to compare the steady state and transient flow fields of the calculation domain under different gas supply pressures and different pressure chamber shapes.(3)Based on the fluid lubrication theory,the dynamic vibration equation of the air hammer vibration of the aerostatic bearing is established.The numerical analysis shows the system phase diagram and time domain diagram under different initial values,different film thicknesses and different gas supply pressures.The change.In addition,for the cause of the vibration of the air hammer,measures to reduce the vibration of the air hammer are proposed.(4)Using the dynamic mesh model to analyze the influence of different disturbance frequencies on the dynamic bearing capacity of the bearing,and modeling the theoretical analysis of the relationship between dynamic stiffness and dynamic damping with the disturbance frequency,and based on the variation curve combined with viscoelastic theory,the two types of analysis are derived.An equivalent gas film dynamic model of a three-element solid model.The analysis shows that the three-element model of viscoelastic theory can well express the dynamic stiffness and dynamic damping characteristics of the gas film.(5)Using the Fluent software to solve the air film stiffness of the aerostatic bearing under different air supply pressures,based on the simulation of the spring-damper unit(COMBIN14)and the bearing unit(COMBI214)in the finite element analysis software ANSYS Workbench The film stiffness is analyzed,and the dynamic response of different air supply pressures to the modal influence of the spindle system and the cyclic exciting force are analyzed. |
PDF Full Text Request