热轧粗轧主电机轴弯曲分析及其轴承油隙测试新方法

大型常规薄板热轧生产线主电机的支撑轴承多采用静压滑动轴承型式。所谓静压滑动轴承是相对于动压滑动轴承而言,是指滑动轴承下轴瓦底部引入一路高压润滑油,进而在电机静止状态下建立一个静压油隙。电机各轴承的高压润滑油油隙的测试与调整,是检测轴承功能精度、保证电机轴承可靠稳定运行必不可少的工作,通过对直联轴传动模式的粗轧电机转轴的受力分析,提出了此传动模式下电机转轴的弯曲概念,进而提出了电机轴承油隙测试的新方法。     

Surface roughness effect on the dynamic stiffness and damping characteristics of compensated hydrostatic thrust bearings

On the basis of Christensen's stochastic model of rough surfaces, this study theoretically analyzes the effect of surface roughness on the dynamic stiffness and damping characteristics of compensated hydrostatic circular step thrust bearings. Both the stochastic Reynolds equation with rotational inertia effect and the recess flow continuity equation with recess volume fluid compressibility effect are derived to take into account the presence of roughness on the bearing surfaces. Using a small perturbation method, the dynamic coefficients of bearings are evaluated. According to the results, the mean stiffness and damping behaviours are significantly affected by the roughness pattern and the height of roughness. The effect of circumferential roughness provides an increase in the mean bearing stiffness and damping characteristics as compared to the smooth-bearing case. However, these trends are reversed for the bearing having radial roughness structure. An illustration of a design example is also included for industrial practice.     

Modeling and analysis of journal bearings lubricated with molten zinc for galvanizing process

The production speed of the steel sheet galvanizing process is limited by several factors; the dynamic behavior of the guiding rollers submerged in a molten zinc bath is among the crucial ones. These guiding rollers are supported on journal bearings operating on molten zinc, which acts as the lubricant of the bearings. This article addresses the modeling of journal bearings of this type as a two degrees of freedom system. The molten zinc film thickness is treated as a set of the classical hydrodynamic coefficients (stiffness and damping elements) to study the bearing dynamics and vibration stability, as well as the minimum film thickness formation. Computer- simulated test cases of the bearing geometry, zinc alloy viscosities at different temperatures, and operating conditions demonstrate the stable bearing performance at a desired galvanizing production speed.     

不同工作参数下水轴承的空化程度及微形貌特征对减阻效果的影响

目的为了提高水轴承高速下的减阻效果以及预测水轴承的空蚀区域,研究了高速水静压轴承的空化与减阻性能。方法基于低雷诺数Launder-Sharma模型和空化气泡的动力学模型,分析了不同工作参数下水轴承的空化程度研究及微形貌特征对减阻效果的影响。结果空化气泡主要出现在静压轴承水腔之间的负压封水面及小孔节流器附近,空化气泡溃灭时容易造成轴承材料的空蚀破坏。高速小偏心率时,相比流向和展向微形貌,凸柱微形貌特征表面具有较好的减阻效果,且减阻效果受轴颈线速度的影响较大。结论转速、供水压力和偏心率等物理参数影响水静压轴承空化气泡分布和静态性能,微形貌界面的速度滑移有利于提高减阻效果。     

高速球轴承生热量的理论及试验研究

结合高速球轴承的拟动力学模型,分析轴承各零件在接触点处的切向摩擦力和相对滑动速度。利用局部分析法建立轴承生热量计算模型。研究转速、载荷和轴承几何结构参数对轴承各单元间的局部生热量和总生热量的影响。搭建轴承试验台,监测轴承生热量随工况的变化规律;将相同条件下的理论计算结果和试验结果进行对比,验证理论模型的正确性。结果表明:轴承在稳定运行时,转速和外加轴向载荷是造成轴承总生热量的主要因素;在球径一定的情况下,内、外圈沟曲率半径系数存在一个使轴承生热量最小的最优值;分析轴承生热量变化规律,有利于轴承的温度场计算、润滑油油量的选取等。研究结果为轴承结构的优化设计提供参考。     

煤磨机动压轴承改静压轴承的设计及应用

简要介绍了煤磨机轴承改造的原因、要求及动静压轴承的特点，重点阐述了动静压轴承的主要技术参数和供油系统的设计计算。     

超精密定位工作台静压导轨静态特性及流场仿真分析

研究超精密液体静压定位工作台中的液体静压导轨静态特性问题。根据流体润滑理论及雷诺方程,构建了导轨油膜压力的数学物理模型,运用有限元方法求解静压导轨的各项静态特性参数,如导轨的承载能力、静刚度、流量等。运用三维造型软件Solid Works和CFD软件FLUENT,从结构三维造型设计和内部三维流动综合分析液体静压导轨,获得油膜压力的分布云图、曲线和油腔液压油流速分布云图,并分析不同结构设计参数和环境参数对液体静压导轨静态特性的影响。本文研究将对实际的静压导轨系统设计具有指导意义。     

新型静压支承结构液压缸力学性能分析与实验

传统液压缸多采用导向环和密封圈组合密封的方式,普遍存在内耗高、响应速度慢、抗偏载力差等问题。在静压支承理论的基础上,提出一种新型椭圆形静压支承结构液压缸及其设计方法。采用理论计算和模拟仿真相结合的方式,对比分析了传统型、矩形静压腔和椭圆形静压腔液压缸的抗偏载力、摩擦力的大小及其主要影响因素。仿真结果表明：静压支承式液压缸的抗偏载能力和摩擦力性能均明显优于传统结构液压缸,且椭圆形静压腔结构具有明显优势。最后,设计实验测试平台,通过实验验证了上述计算模型和仿真模拟的正确性。     

Virtual Design and Optimization of Machine Tool Spindles

An integrated digital model of spindle, tool holder, tool and cutting process is presented. The spindle is modeled using an in-house developed Finite Element system. The preload on the bearings and the influence of gyroscopic and centrifugal forces from all rotating parts due to speed are considered. The bearing stiffness, mode shapes, Frequency Response Function at any point on the spindle can be predicted. The static and dynamic deflections along the spindle shaft as well as contact forces on the bearings can be predicted with simulated cutting forces before physically building and testing the spindles. The spacing of the bearings are optimized to achieve either maximum dynamics stiffness or maximum chatter free depth of cut at the desired speed region for a given cutter geometry and work-piece material. It is possible to add constraints to model mounting of the spindle on the machine tool, as well as defining local springs and damping elements at any nodal point on the spindle. The model is verified experimentally.     

Thermo-mechanical model of spindles

This paper presents a Finite-Element-method-based thermo-mechanical model of spindles with rolling bearings. The heat generated in the bearings and the motor is transferred to the ambient air, the motor coolant and the spindle structure, and causes thermal expansion of spindle parts. The experimentally validated thermo-mechanical spindle model predicts temperature distribution and thermal growth, as well as bearing stiffness and contact loads, under specified operating conditions. Transient changes in temperatures, deformations, viscosity of the lubricant, and bearing stiffness are considered in the solution. The predicted bearing properties are used to estimate the changes in the dynamic behavior of spindles.     

A Novel Single Cathode Plasma Column Design for Process Stability and Long Component Life

This paper investigates a novel single cathode plasma column design consisting of a patented arc constrictor and its impact on process stability, versatility, and component life. The design aims to minimize the re-strike of arc, increase the arc length enabling high voltage and low amp operation as well as the use of ternary gas combination to increase the enthalpy. The arc unsteadiness and dynamic behavior are investigated through the fluctuations of electrical signals. Further, the particle velocity and temperature have been characterized by commercial diagnostics systems. The takeover/steady mode appears to be the typical operational mode of the plasma jet in this design. Low amplitude and high frequency fluctuations resulted in steady particle characteristics. Further, the design allowed the gun to operate at very high plasma velocities reaching the characteristics of an HVOF jet. The significance of the design is demonstrated through operational flexibility and stability.     

基于MATLAB GUI的角接触球轴承接触疲劳寿命计算系统设计

滚动轴承是机器中广泛应用的零件之一,依靠滚动体和滚道间的滚动接触来支承转动零件,轴承的使用寿命是轴承质量的重要衡量指标。针对滚动轴承失效形式主要是疲劳点蚀,往往采用接触疲劳寿命来反映轴承寿命,它综合考虑了轴承材料、接触特性等因素,更符合实际工况。采用MATLAB GUI软件平台完成角接触球轴承接触疲劳寿命计算系统设计,该系统使用方便,只需输入相关参数,便可计算出接触疲劳寿命、最大接触载荷和最大接触应力等参数,结果可在系统界面显示或输出txt文件和excel表格。该系统大大缩短了轴承寿命计算周期,提高轴承设计效率和精度。通过多次工程设计验证,该系统高效可靠,为工程设计中其他复杂计算系统的开发提供了参考。     

Accurate Tool Height Control by Bearing Gap Adjustment

Face turning of optical surfaces on precision lathes needs high precision tool height adjustment, which may be a difficult and time-consuming task. In this paper we present a new tool adjustment mechanism based on varying the bearing gap height of the hydrostatic bearings present in precision lathe slides. Slide height variation is realised by influencing the flow to the bearing chambers. This is obtained by adding adjustable restrictions into the oil supply tubes. The bearing stiffness change is limited and stays high in comparison with other machine elements. The realised system has a fine adjustment range of 20 urn, a resolution better than 0.1 μm and a repeatability error lower than 0.1 μm.     

分流组合模挤压铝合金口琴管的数值模拟

采用刚粘塑性有限元法,在DEFORM-3D有限元商业软件上成功实现了铝合金口琴管分流组合模挤压过程的三维数值模拟,获得了分流组合模挤压过程中材料的流动规律,挤压力、应力场、应变场和温度场的分布,以及模具出口处金属流速的分布情况。通过数值模拟发现,型材出口流速不均匀,造成端面不齐,对此,提出了模具修改方案,通过调节模具工作带的长度,实现了型材挤压出口流速均匀的目的,从而保障了型材的产品质量。模拟结果为模具的优化设计及工艺参数的选取提供了理论参考。     

Evaluation of an internally spring preloaded four contact-points bearing for spindle units

In this paper, the concept of an internally spring preloaded four contact-points bearing for the use in high precision and high speed applications is investigated. It is designed as a compact self-contained fixed bearing unit that is free of play, easy to mount and resistant against temperature differences between the inner and outer ring. The concept of the bearing, its functionality and properties are introduced and the results of an experimental analysis of a first prototype are presented. The prototype bearing, which is based on a hybrid 7014 spindle bearing with an additional spring preload unit, was manufactured by hard turning. Its properties are compared to those of similar two and three contact-points spindle bearings. Typical requirements in modern high precision applications, e.g. machine tool spindle units, and limiting characteristics of bearings, such as displacement, stiffness, friction torque and operating temperature, are considered. Finally, the potential of the new bearing concept is discussed.     

基于CFD的静压转台油膜特性分析与油腔设计

针对静压转台回转运动精度不足的问题,以数控磨床的扇形液体静压转台为对象,对单个静压支承结构的位移率和设计间隙进行理论计算,得到油膜承载力与位移率和设计间隙之间的关系。对油腔内部流场进行仿真计算,得到不同油腔结构对油腔流场中承载性能产生的影响规律;根据仿真结果和转台的参数要求选取合适的油腔结构,设计了扇形静压转台;通过流固耦合分析,验证油腔设计的合理性;通过油膜刚度试验,验证了油腔设计的可行性。     

舵机动刚度加载系统设计与分析

动刚度是舵机不可忽视的一项动态性能,加载系统的性能直接影响动刚度的测试结果。分析系统的原理结构,从静压支承伺服作动器的计算设计、伺服阀的选型、回油系统与安全保护措施的设计等方面对加载系统进行了全面设计。该系统已经投入使用,性能表现良好。     

Frequency dependent stiffness and damping coefficients of orifice compensated multi-recess hydrostatic journal bearings

Frequency dependent stiffness and damping characteristics of an orifice compensated multi-recess hydrostatic journal bearing has been presented incorporating recess volume fluid compressibility effects into it. The theory is based on linearising the Reynolds' equation for finite bearings and the recess flow continuity equation using first order perturbations. A new dimensionless recess volume fluid compressibility parameter (γ) has been introduced. Results for stiffness and damping characteristics have been presented for various frequency of vibration or squeeze parameters (σ) and recess volume parameters (γ) in addition to the usual bearing design parameters.     

基于改进的动载荷分布方法的角接触球轴承磨损计算研究

针对固体润滑角接触球轴承的润滑磨损寿命无法精确预测问题,提出一种更为准确的基于动载荷分布的磨损寿命计算模型,并考虑内、外圈载荷同时作用下的动载荷分布。建立内、外圈和滚道之间的动载荷计算模型,更准确地表征角接触轴承运动接触特性,同时将轴承整个零部件的动载荷分段计算方法与磨损计算模型相结合,建立考虑轴承整体接触区动载荷分布下的磨损模型,为轴承承载运行下的磨损寿命机制分析提供参考。     

径向型超导轴承的计算和实验研究

针对应用于离心式氦气冷压机的径向型高温超导磁悬浮轴承,给出了永磁转子磁场计算和结构设计方法,并开展了轴承径向力和径向刚度的计算研究,搭建了超导轴承性能测量平台,开展了轴承转子空间磁场测量和轴承性能测试。计算和测试结果表明,磁场计算方法可行,且结果准确,在距离永磁转子外表面1 mm处的最大外磁场强度约为0.5 T。轴承径向力在场冷和零场冷条件下的计算结果均随转子偏心量的增大而增大,与测试结果在线性度和趋势上具有很好的一致性。本文实验轴承径向刚度测试值为362.4 N/mm,与场冷条件下的径向刚度计算结果334.594 N/mm接近。本文所述的径向轴承磁力计算方法可用于超导轴承径向刚度的定性计算和设计,对超导轴承的应用研究具有一定的指导意义。