空气静压止推轴承静态性能测试装置设计

根据空气静压止推轴承静态性能测试要求,设计了一套基于气体静压轴承负载自动平衡原理的测试装置,实现了对空气静压止推轴承承载力、不同负载下气膜厚度以及气膜间隙内压力分布的测量.实验结果与理论分析结果取得较好的一致性,说明本套实验装置的设计是合理的.     

非球面超精密机床静压轴承温度场的分布

利用ANSYS CFX流体力学分析软件建立了不同油膜厚度下的液体静压轴承流体模型,研究了非球面超精密加工机床液体静压推力轴承的温度场分布。对静压推力轴承进行了试验研究,获得了工作台上不加负载、加300kg负载、加500kg负载3种情况下主轴性能各参数。仿真结果表明:油腔区域初始温度为20℃,从封油边开始温度逐渐升高,其中外侧的温度要比内侧温度稍高;当油膜厚度为33μm时,最高温度为20.29℃,当油膜厚度为23μm时,最高温度为21.72℃,油膜厚度越薄,温度越高。试验计算值与仿真值分别相差3.33%、8.33%、1.32%,证实了液体静压推力轴承设计和数值计算的正确性。     

Nanosys-1000机床静压止推轴承流场分布规律及承载特性

为了提高Nanosys-1000非球面曲面光学零件超精密加工机床加工精度,研究了机床核心部件静压止推轴承内流场分布规律,进而揭示其承载特性。利用ANSYS/Fluent软件建立对称结构静压止推轴承扇形油垫的仿真模型,采用层流模式对进油压力为1.3~1.9 MPa、油膜厚度为20~36 μm的油垫流场分布规律与承载特性进行分析。研究结果表明：油垫内压力在油腔区域比较均匀,沿封油边呈线性下降;油膜承载力随油腔压力线性增长,且在同一进油压力下,油膜厚度越小,油膜承载力越大,进油压力为1.5 MPa时,油膜厚度从36 μm减小到20 μm,油腔压力从3.05×10⁵ Pa增加到8.02×10⁵ Pa,油膜承载力相应地从880 N增加到2 109 N;同一负载即油膜承载力下,进油压力越高,油膜厚度越大,油膜承载力为1 320 N时,进油压力从1.3 MPa增加到1.9 MPa,油膜厚度从26 μm增加到30 μm;同一油膜厚度下,进油压力越高,润滑油流量越大,油膜厚度为28 μm时,进油压力从1.3 MPa增加到1.9 MPa,润滑油流量从0.179 L/min增加到0.231 L/min。相关研究结果在研制的Nanosys-1000非球面曲面超精密加工机床静压止推轴承上得到了验证。     

精密机床电主轴静压轴承制造误差对性能的影响

分析了精密机床主轴静压轴承节流器孔径d₀、轴承半径间隙h₀、油腔长度L和油腔宽度B等参数的制造误差,选取了制造误差影响较大的节流孔径d₀和半径间隙h₀作为分析的对象;建立了考虑节流孔径误差ε_d和半径间隙误差ε_h的静压轴承性能计算模型,计算分析了ε_d和ε_h影响下的轴承刚度J和回转精度e,并通过试验对理论分析结果进行了验证。研究结果表明：制造误差ε_d和εh对J的影响随载荷W的增加而增大,W为600 N、εd为0.05 mm时的J值是εd为-0.05 mm时的1.34倍,εh为10μm时的J值仅为εh为-10μm时的29.9%;对于e,εd会带来1μm左右的影响,ε_h会带来2μm左右的影响。     

空气静压导轨静态性能的解析计算及分析

空气静压导轨是空气静压止推轴承的一种，在直线气浮导轨中被广泛采用。本文利用线性气源假设，将气膜中气体的二维流动化为一维流动，使雷诺方程得到简单的解析解，推导出空气静压导轨的解析计算公式，并利用该计算公式分析导轨参数对其静态性能的影响，从而为空气静压导轨找到了一种快捷方便的设计方法。     

高效精密磨床砂轮主轴深浅腔动静压轴承静特性分析

阐述用于高效精密磨床砂轮主轴的HSDB-R深浅腔动静压轴承的原理;建立基于Navier-Stokes方程的轴承油膜流体力学控制方程,采用基于有限体积法的三维流体力学仿真软件FLUENT分析轴承工作参数和结构参数对轴承承载能力、刚度、温升等性能的影响;对比"一"字和"匡"字2种油腔结构形式对于轴承刚度及温度分布的影响。结果表明:"一"字油腔结构能够提高轴承承载力和刚度,"匡"字油腔结构有助于降低轴承温升。     

空气静压立式主轴静态性能分析

介绍空气静压主轴静态性能仿真分析原理,构建静态性能的测试平台,测量立式空气静压径推联合轴承的静态性能,并分析测量过程中的误差影响。实验结果与数值仿真结果基本一致,表明数值仿真的计算结果比较理想而且稳定,证明将该方法应用在空气静压主轴静态性能预测的可行性。     

Zero-compliance aerostatic bearing for an ultra-precision machine

A new type of active air film restrictor is proposed for obtaining a zero-compliance aerostatic thrust bearing. The moving member in the active retrictor is sopported elastically. This active restrictor can therefore be called an aerostatically controlled-restrictor (ACR). Experiments show that the compliance of the thrust bearing with the ACR can be less than 1 nm N⁻¹ when the frequency of the applied load is less than 2 Hz. Pneumatic hammer does nor occur during the experiments.     

均压槽尺寸对空气静压导轨静态性能的影响

引入有限体积法,采用理想气体等温条件下的k—ε模型封闭流动控制方程组,对均压槽尺寸改变条件下空气静压导轨润滑气膜流场分布进行数值模拟,得到导轨工作面压力分布图及承载力、刚度变化曲线,数值模拟结果表明：导轨承载力及气膜刚度随均压槽尺寸的增大而先增大后减小,存在一个最佳值;随均压槽尺寸增大,导轨工作面压强分布趋于均匀;但当均压槽大于一定尺寸时,气膜湍动随机性引发导轨工作面压强不规则分布,易造成偏载、导致导轨性能不稳。该结论为空气静压导轨均压槽设计及导轨系统静态性能的提高提供依据。     

超精密五轴机床的几何误差建模和灵敏度分析

基于设计出超精密机床的目的,研究了机床的几何误差建模和误差的灵敏度分析。基于刚体运动学和齐次变换矩阵(Homogeneous Transformation Matrix,HTM)建立了RTTTR配置的超精密五轴机床的几何误差模型,模型涉及37个误差分量。分别对37个误差分量进行了几何误差的灵敏度分析,分析结果将应用于超精密五轴机床的设计与制造上。     

可变节流高度气浮支承结构设计及静态性能分析

为研究节流高度的变化对气浮支承性能的影响,设计一种可变节流高度的气浮支承。建立气浮支承CFD模型,分析节流口直径、节流高度、均压腔深度和供气压力的变化对气浮支承静态性能的影响。研究结果表明:气浮支承的承载能力随节流口直径、节流高度、均压腔深度和供气压力增大而增大;节流高度、均压腔深度、供气压力的增大能提高气浮支承刚度,而节流口直径的增大会导致刚度的降低;气浮支承的体积流量随节流口直径、节流高度、均压腔深度和供气压力增大而增大。     

变截面节流器对空气静压轴承承载性能的影响

为了分析可变截面节流器对空气静压轴承性能的影响,提出了变截面节流器的空气静压轴承模型,通过轴承承载表面弹性薄板的挠度变形实现节流器截面形状的动态变化。建立固体薄板变形和气体润滑的耦合偏微分方程,采用有限差分法和超松弛迭代法对耦合方程进行离散和数值求解。计算结果表明:节流器的截面形状直接决定了数值计算过程中喷嘴系数的大小,与刚性节流器的空气静压轴承相比,变截面节流器的空气静压轴承刚度提高了15%,在较高承载力的情况下能够获得更大的刚度。实验测试结果和理论分析基本一致,变截面节流器的设计方法能够有效提高空气静压轴承的静特性。     

Improvement of static characteristics of an aerostatic journal bearing using the elastic deformation of an O-ring

A new type of aerostatic journal bearing in which the elastic deformation of an O-ring is used to improve its static characteristics is proposed. The static characteristics of this bearing are determined theoretically by both the finite difference method and the small perturbation method. Effects of parameters on the static characteristics are shown, and the optimum design method for the static characteristics is discussed. Further, theoretical results are compared with experimental results to confirm the validity of theoretical predictions. It is consequently found that the new type of bearing possesses higher static stiffness and greater load capacity than conventional point source bearings with inherently compensated feeding holes.     

超精密平面飞切机床关键技术研究

研制了一种用于KDP晶体加工的平面飞切机床,该机床直线轴基于直线电动机驱动、液体静压导轨支承;刀具旋转轴采用高刚度气浮主轴+高刚度主轴旋转机构。基于高精度分辨率位置反馈+线性驱动器+PID控制算法,直线轴获得了1 mm/min速度下,0.018 mm/min的低速波动以及±0.01μm的位置精度;刀具微进给装置采用差动螺纹进给来实现,最终获得了进给分辨率1μm、锁紧后位置移动量小于1μm高精度进给。在优化工艺参数后,金刚石飞切机床加工100 mm×100 mm×10mm的KDP晶体后获得表面粗糙度Rq优于2 nm高精度指标;加工400 mm×400 mm×30 mm的铝镜后获得面形PV值优于3μm的高精度指标。     

Static tilt characteristics of aerostatic rectangular double-pad thrust bearings with compound restrictors

Aerostatic rectangular thrust bearings with compound restrictors have often been used in ultra-precision machine tools and precision measuring equipment because high bearing stiffness is easily achieved. Compound restrictors combine a feed-hole restrictor with a groove compensation restrictor. This paper investigates, theoretically and experimentally, the static tilt characteristics of aerostatic rectangular double-pad thrust bearings with compound restrictors, when coupled loads or offset loads are applied. Furthermore, the usefulness of aerostatic thrust bearings with compound restrictors is clarified by comparison with the characteristics of conventional aerostatic thrust bearing with feedhole restrictors.     

Accuracy prediction model of an orifice-compensated aerostatic bearing

In order to reduce the synchronous radial error motion of the orifice-compensated aerostatic bearing, an accuracy prediction model was built to discuss the direct relationship among the synchronous radial error motion, the roundness error, and the nozzle number. It was found that increasing the nozzle number delayed the appearance of the obvious peak of the averaging coefficient and roughly reduced the synchronous error motion. The optimized nozzle number was n_p = 2 × 3 × 5 × 7 × …, which was equal to the product of the prime numbers within the prime sequence. The existence of axial grooves and the increase in the nozzle row number didn't reduce the synchronous error motion, but it might cause an increase in the synchronous error motion. The accuracy prediction model gave a simple method for predicting the synchronous radial error motion of the orifice-compensated aerostatic bearing.