| An ultra-high speed aerostatic motorized spindle is one of the main parts that are employed for the high precision and high efficient cutting and is a key functional part of the high-value manufacturing machine tool. The spindle is characterized by using aerostatic bearings and electromagnetically actuated direct drive, and the comprehensive performances are thus greatly affected by multi-physics interactions such as electric-magnetic field, gas-solid-thermal interactions. This paper aims to address the immediate great challenges in developing the key part of micro-cutting manufacturing machines. This paper focuses on the following two key scientific challenges, i.e.1) the working mechanism and performance enhancement measures of the ultra-high speed air bearings and 2) the effects of multi-physics coupling interactions on the steady state characteristics of the aerostatic motorized spindle system. Therefore, this paper will carry out interdisciplinary research covering the analysis methodologies and key enabling techniques. Furthermore, this paper will analyze the comprehensive behaviors of the aerostatic bearing with an ultra-high speed operating condition and reveal the effects of the herringbone groove microstructures on the performance of the gas journal bearing. Besides, this paper will investigate the effects of multi-physics coupling interactions on the steady state performance behaviors of the motorized spindle system. Research achievements of this paper will provide basic theories and key technical supports to develop the key enabling components of the high-value manufacturing machines.To meet the requirements of high speed, high precision and stability for the ultra-high speed aerostatic motorized spindle, this paper analyzes the key enabling techniques of the motorized spindle system and proposes the basic design principles of the ultra-high speed aerostatic motorized spindle. Furthermore, the design schemes of the ultra-high speed aerostatic motorized spindle and its key components are established. Besides, the nonlinear compressible Reynolds equation is numerically solved by the finite element method. The finite element form of the Reynolds equation that includes the velocity item is deduced and the improved method is proposed for solving the finite element form of the Reynolds equation. What’s more, the performance characteristics analysis method of the microstructures for the ultra-high speed air bearing is proposed based on the computational fluid dynamics (CFD) method, and the multi-physics integrated simulation approach of the air bearing motorized spindle system is firstly proposed, providing the theoretical foundation for the performance analysis of the ultra-high speed aerostatic motorized spindle.To investigate the working mechanism of the aerostatic bearing under conditions of various rotational speeds and eccentricities, the performance analysis computational programs of the aerostatic journal bearing and the thrust bearing are developed based on the numerical mathematical model of the gas lubricated Reynolds equation. The influences of the aerostatic effect, aerodynamic effect and hybrid effect on the ultra-high speed aerostatic journal bearings are analyzed, and the effects of the geometry parameters of the aerostatic journal bearings and aerostatic thrust bearings on the bearing performances are investigated. Furthermore, the CFD simulation model of the air bearing is established, and the effects of the microstructures such as orifice chamber shapes and uniform pressure grooves on the performance behaviors of the aerostatic bearings are identified with ultra-high speed operating conditions. Besides, this paper presents a new structural configuration of the aerostatic thrust bearing-conical aerostatic thrust bearing. The fluidic characteristics of the conical aerostatic thrust bearing are investigated, and thus the performance characteristics are obtained. Compared with the plain aerostatic thrust bearing, the comprehensive performance specifications of the aerostatic thrust bearing are improved by the conical shape. Finally, the CFD models of the air bearing are validated by experiments.To investigate the effects of the herringbone groove microstructures on the performance characteristics of the ultra-high speed air journal bearing, this paper firstly elucidates the functional mechanism of the herringbone groove microstructure for the air journal bearing. Then, the design principles of the herringbone groove microstructure are proposed. Secondly, the mathematical model is established based on the Reynolds equation numerically solved by the finite element method to investigate the effects of geometry parameters of the herringbone groove microstructure on the performance characteristics of the aerodynamic journal bearing and the hybrid journal bearing with different operating conditions. Thirdly, the sensitive analyses are conducted based on the design of experiments established by orthogonality arrays to investigate the influences of the geometry parameters of the herringbone groove microstructure on the load capacity of the aerodynamic journal bearing and the hybrid journal bearing. Finally, experimental studies are done to investigate the effects of the eleven groups of herringbone groove microstructures on the radial runout of the motorized spindle system with various rotational speeds, and the experimental results depict that the herringbone groove microstructure can effectively decrease the radial runout of the motorized spindle system.To investigate the steady state performance characteristics of the ultra-high speed aerostatic motorized spindle system under conditions of the multi-physics coupling interactions, the interaction mechanisms among different fields are identified. The multi-physics integrated simulation model of the ultra-high speed aerostatic motorized spindle system constituted with electromagnetic model, thermal model, fluidic model, and structural model is constructed based on the Isight software. Then, the steady state temperature field, the structural thermal deformation, air bearing fluidic behaviors and the shaft rotordynamics are analyzed under conditions of multi-physics coupling interactions. Furthermore, the experimental studies are done to investigate the temperature behaviors, structural thermal deformations, air consumptions, shaft free modal and vibration of the spindle system under the steady state operating conditions, and the multi-physics integrated simulation model is validated by the experimental results. |
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