Fluid-Structure Interaction Analysis On The Static Characteristics Of Aerostatic Spindle Of Ultra-Precision Machine Tool

Single point diamond turning technology is critical to realize the processing of large-aperture and high-precision potassium dihydrogen phosphate (KDP) crystal. Excellent dynamic and static characteristics of the spindle are the cores to achieve the processing precision of machine tool. High-precision and high-stiffness aerostatic bearing is generally used in the spindle of ultra-precision machine tool. Considering the interaction between structure and fluid, how to obtain accurate static characteristics of aerostatic bearing in the design has a great significance not only to the design of the gas spindle but also to the dynamics analysis and the desigh of the whole machine tool.Ultra-precision machine tool for KDP crystals is the research object of this paper. Firstly,the theoretical formulas on the static characteristics of aerostatic thrust bearing are derived with the basic equations of fluid dynamics and the stiffness of the thrust bearing under the working pressure is calculated with the theoretical formulas. And the factors that affect the capacity and stiffness of the aerostatic thrust bearing are analyzed.Secondly,the fluid-structure interaction analysis finite element model of the aerostatic thrust bearing in the ultra-precision machine tool for KDP crystals is established. And the sequential coupling algorithmis is proposed to realize the fluid-structure interaction analysis of the aerostatic thrust bearing. The structural deformation of the spindle under working conditions is calculated and the influence of the elastic deformation of thrust plate on the stiffness of the aerostatic thrust bearing is analyzed. On this basis, the influence law of the number and diameter of the screws between the thrust plate and the spindle on the elastic deformation of the spindle structure is analyzed, it directs the optimization of joint structure.Thirdly, the experimental research on the deformation and the stiffness characteristics of the gas spindle under different working pressure is carried out. The results of theoretical formulas calculation, finite element analysis and experiment are compared and their errors are analyzed.Finally, the whole mechanical structure model of the ultra-precision machine tool for KDP crystals is established. The stiffness characteristics of the aerostatic thrust bearings is converted to spring element, and then it is added to the whole machine tool. Static and dynamic analysis on the whole machine tool is made. The structural strength is checked. The influence of the static characteristics of the aerostatic thrust bearing on the dynamic characteristics of the entire machine tool is analyzed.