【作者】 侯志泉；

【导师】 熊万里；

【作者基本信息】 湖南大学 ， 机械制造及其自动化， 2013， 博士

【摘要】 精密超精密机床是国防工业、航空航天工业和民用光学工业中精密超精密零件的关键加工装备,是事关国防安全的战略性装备。液体静压主轴是精密超精密机床的核心部件,其回转精度对于机床的加工精度具有决定性影响。虽然国内外已有液体静压主轴的成功应用案例,但迄今尚缺乏针对回转精度形成机理的专门研究成果,现有工作不能有效揭示主轴旋转形成回转误差的动态发展过程,不能定量解释静压轴承均化效应和揭示提升静压主轴回转精度的物理本质,难以为静压主轴回转精度的工程设计和预测提供系统深入的理论支持。本文着眼于轴心运动轨迹的动态发展过程,建立了静压主轴回转精度的流固耦合动力学模型,提出了基于CFD动网格模型的求解新方法,实现了主轴形成回转精度时轴心运动轨迹的定量仿真,揭示了静压主轴回转误差的物理机理；系统研究了工作参数和结构参数以及静压轴承摩擦副形状误差对回转精度的影响规律；建立了液体静压主轴回转精度测试平台,对比研究了理论计算和实验测试的主轴误差轨迹和回转精度。本文主要研究工作包括：(1)建立了基于N-S润滑方程和主轴动力学方程的静压主轴流固耦合动力学模型,提出了基于CFD动网格模型的实现回转精度动态过渡过程的求解新方法。该方法将主轴旋转和平动方程嵌入CFD并求解N-S方程,计算瞬态油膜压力,将轴颈旋旋转动边界转换为静边界,利用弹簧光顺模型更新主轴位移引起的油膜网格变形,界定了主轴在油膜中运动速度的取值范围。通过对比分析理论计算与实验测试典型静压主轴的四个油膜刚度,证实了静压主轴回转精度的流固耦合动力学模型及求解方法是可行和有效的。(2)定量计算了主轴由轴颈与轴承同心位置开始过渡到稳态回转运动轨迹的动态发展过程,揭示了静压主轴形成回转精度的物理机理。采用全程动网格方法、平衡位置动网格方法和油膜刚度阻尼公式三种方式,定量计算和仿真了主轴由轴颈与轴承的同心初始位置到形成回转误差的运动轨迹,研究揭示了静压主轴形成平均回转中心和回转误差时主轴合力、轴承流量和轴心位置的动态发展规律以及扰动因素与主轴合力、轴承流量和轴心位置之间内在联系。通过对比三种方法计算的平均回转中心和回转精度,结果表明采用动网格与油膜刚度阻尼公式相结合方法计算主轴回转精度可兼顾计算效率和仿真精度。(3)系统研究揭示了静压主轴结构参数和工作参数对回转精度的影响规律。采用动网格方法定量研究了工作参数(包括工作转速和供油压力)和结构参数(包括长径比、节流孔径和轴承间隙)对平均回转中心和油膜刚度阻尼的影响规律；采用简化公式计算了动不平衡激励下主轴的回转误差,研究揭示了工作参数和结构参数对主轴回转精度的影响规律。结果表明：增加供油压力和长径比,可提高主轴回转精度；增大节流孔径、工作转速和轴承间隙,将降低主轴回转精度。(4)研究揭示了轴承形状误差对主轴回转精度的影响规律。定量计算并分析了轴承形状误差影响下主轴平均回转中心位置和油膜刚度阻尼的变化规律；通过对比分析误差轴承与理想轴承的平均回转中心位置和油膜刚度阻尼,发现了轴承形状误差是影响平均回转中心位置和油膜刚度阻尼的根本原因,研究揭示了轴承形状误差对静压主轴回转精度的影响规律。结果表明：光滑轴颈条件下,轴承本身的形状误差虽然不会使主轴发生位置变动而产生回转误差,但通过影响主轴平均回转中心位置及其油膜刚度阻尼,影响主轴的回转误差。(5)研究揭示了轴颈形状误差对主轴回转精度的影响规律。定量计算并分析了轴颈圆度误差和圆柱度误差对主轴平衡位置和油膜刚度阻尼的影响规律,重点分析了主轴旋转时轴颈圆度误差峰谷交替变化对主轴轴心位置产生的影响,揭示了静压轴承对轴颈形状误差的均化机理。结果表明：光滑轴承条件下,轴颈圆度误差使主轴发生位置变动,形成回转误差,回转误差大小与轴颈圆度误差的幅值和频率有关；轴颈圆柱度误差虽然不会使主轴产生位置变动而产生回转误差,但通过影响主轴平均回转中心及其油膜刚度阻尼,影响主轴的回转误差。(6)建立了液体静压主轴试验台,测试了静压主轴的误差轨迹和回转精度,验证了理论计算误差轨迹和回转精度的部分结果。测试了静压主轴的三维运动形态,分析了磨床主轴倾角运动简化为径向运动的科学依据；对比研究了理论计算与实验测试的误差轨迹和回转精度,结果表明：理论计算与实验测试的误差轨迹均呈椭圆形状,理论计算椭圆长轴约为实验值的78.8%；理论计算与实验测试的回转精度值之比约为75.6%。理论计算结果与实验测试结果一致性好。本研究提出的静压主轴回转精度的流固耦合动力学模型及其动网格求解新方法,发展了回转精度的分析方法；研究揭示了静压主轴形成回转误差的物理机理；理论阐释了静压轴承对轴颈误差的均化效应；建立并发展了静压主轴回转精度的理论体系,研究成果为超精密液体静压主轴开发提供有力的理论指导和技术支撑。更多还原

【Abstract】 The precision&ultra-precision machine becomes vital processing equipment for ultra-precision parts in national defense industry, aerospace, industrial and civil optical industry, also strategic equipment for national defense security. Machine spindle is the core part of ultra-precision machine, and the rotational accuracy of hydrostatic spindle plays a determinative influence on the machine’s processing precision. Currently, there is successful application for ultra-precision hydrostatic spindle. However, specialized research on the mechanism of rotary accuracy is still lacking, the physical origin of rotation error caused by the spindle rotation is not effectively revealed, the transitional process of rotary accuracy is not quantitatively explained, and systematically guidance and prediction cannot be provided for engineering design.Focused on the dynamic development process, the dynamic model of the fluid-structure interaction for hydrostatic spindle rotary accuracy is constructed in this paper, and its new solution based on CFD dynamic mesh model is proposed. The trajectory of the axis of spindle during spindle forming rotary accuracy is quantitatively simulated, meanwhile the physical origin of rotary error caused by the spindle rotation is revealed. On such basis, the effect of working parameter, structure parameter and manufacturing error of hydrostatic spindle friction pair on the rotary accuracy is systematically studied in this paper, and the hydrostatic spindle rotary accuracy test platform is constructed, the spindle error trajectory and rotary accuracy obtained by the theoretically calculated and experimentally tested are comparatively studied, which confirms the correctness and validity of the research. The research work and key result of this paper is listed as follows:(1) The dynamic model of the fluid-structure interaction for hydrostatic spindle rotary accuracy based on Navier-stokes equation and spindle dynamics equation is constructed, and its new solution based on CFD moving mesh model is proposed. This solution inserts the spindle rotational and translational equation into CFD software and solves the N-S equation, calculates the transient oil film pressure, the spindle mesh rotational boundary is transformed into static boundary, the influence of speed disturbance and displacement disturbance on the oil film force is compared, which determined the numerical range of spindle speed effect. The theoretical calculation and experimental test on hydrostatic spindle’s stiffness is compared and analysed, which ensures the validity and feasibility of the hydrostatic spindle rotary accuracy model and solving method.(2) The trajectory of the axis of spindle is quantitatively simulated, and the physical mechanism of hydrostatic spindle forming rotary accuracy is revealed. Three types of method, which is full moving mesh, equilibrium position and moving mesh, and equilibrium position and simplified formula, are applied to calculate and simulate the trajectory of spindle from concentric position to form rotary error. While the hydrostatic spindle forming rotary centre and rotary error, the dynamic development of total force, flow and spindle position are comparatively analysed. Through comparatively studying the influence of these three calculation methods on the rotary centre position and rotary error of hydrostatic spindle, the physical reason of the difference of output among the three methods is found, which shows that combining the moving mesh method and simplified formula to calculate the rotary accuracy of hydrostatic spindle is feasible and valid.(3) The effect of the spindle structure parameters and working parameters on the spindle rotary accuracy is revealed. The operating parameter (including operating rotation speed and oil supply pressure) and the structure parameter (including length to diameter ratio, orifice diameter and bearing clearance) on the rotary centre and oil film dynamic characteristics are quantitatively calculated, and the mechanical reasons of attitude angle, eccentricity, stiffness and damping is analysed, and then the working parameter and structure parameter’s influence on the spindle rotational precision under the condition of the dynamic imbalance excitation is revealed. The result show that when increasing the oil supply pressure and the length to diameter ratio, the rotary accuracy will increase. When increasing the orifice diameter, rotational speed and bearing clearance, the rotary accuracy will decrease.(4) The effect of the shape errors of the bearing on the spindle rotary accuracy is revealed. The influence of the roundness error and the cylindrical error on the rotary centre and oil stiffness&damping were quantitatively calculated. After compared and analysed mechanical root of the structure difference between the error bearing and smooth bearing, the reason of the rotary centre and oil stiffness&damping influenced by the shape errors of the bearing is shown. The effect of the roundness error and the cylindrical error on rotary accuracy of hydrostatic was discussed, the result shows that the shape error of the bearing doesn’t form rotation error, but it affects rotational accuracy through the central position of spindle and the stiffness and damping of oil film. (5) The effect of the shape errors of the journal on the spindle rotary accuracy is revealed. The influence of the roundness error and the cylindrical error on the equilibrium position and oil stiffness&damping were quantitatively calculated. The change of equilibrium position affected by switching between peak and valley of the roundness error was emphatically analysed. Through comparatively analysis the rotary centre position and rotary accuracy affected by the error journal and smoothing journal, the averaging effect of the hydrostatic bearing on the shape error of the journal was discovered finally. The result shows that, the roundness error of the journal forms the rotation error, and the accuracy has relation with the roundness error’s amplitude and frequency. The cylindrical error of the journal doesn’t forms rotation error, but affects rotational accuracy through the central position of spindle and the stiffness and damping of oil film.(6) The trajectory and rotary accuracy of the spindle received by the theoretical calculation and experiments were comparatively studied. A hydrostatic spindle rotary accuracy experiment apparatus was developed, and three dimensional motion of the hydrostatic spindle was experimentally studied. For simplification inclination motion of grinder spindle as cylindrical motion, the scientific basis was found. The spindle trajectory and rotary accuracy obtained by theoretical calculation and experimental test were compared. The result shows that the trajectory of spindle of theoretical calculation and experimental test were ellipse, the theoretical calculated major axis of the ellipse is around78.8%of experimental result. The theoretical calculated rotary accuracy is around75.6%of the experimental result, with a high degree of consistency of theory and experiment.The dynamic model of fluid-structure interaction for hydrostatic spindle rotary accuracy and its new moving mesh method is proposed in this thesis, develops the theoretically analytical methods of rotary accuracy of hydrostatic spindle is developed, the mechanical mechanism of hydrostatic spindle forming rotational error is revealed, the average effect of hydrostatic bearing on the shape error of the journal is theoretical interpreted, the analyze theory of hydrostatic spindle rotation accuracy preliminarily is established and developed, theoretical guidance and technical support for the development of ultra-precision hydrostatic spindle is provided.更多还原