滚动轴承和滚珠丝扛中润滑油脂的外溅性

滚动轴承或直线运动轴承中的润滑油脂,可能飞溅出颗粒,粘附在液晶制品或硬盘上,导致设备失效。所以,这种设备轴承所使用的润滑油脂尽可能降低飞溅性。但低飞溅性的润滑油脂可能带来耐磨性、噪声、阻力矩等问题。因此,我们需要一种油脂,它既具有低飞溅性,又有较高的性能和使用寿命。为了开发低飞溅性的油脂,作者研究了油脂成分和飞溅性的关系。一些数据下面会提到。飞溅颗粒的多少和基油成分有很大关系,例如,润滑油脂基油是矿物油或合成碳化氢油,它们极性低,飞溅颗粒少;相反,如果是酯油,它的极性高,飞溅性也高。飞溅颗粒的多少也取决于增稠剂的类型和含量,例如浓的润滑油脂的飞溅数量少。作者证实了飞溅出来的颗粒不仅有基油颗粒,而且有细小的油脂颗粒,油脂颗粒的直径范围在０．１１ 到０．２μｍ 。     

Microstructure Characterization of Degraded Grease in Axle Roller Bearings

Abstract

Aged mineral-oil-based, lithium-hydroxystearate-thickened grease was collected from used axle spherical roller bearings, which were used for urban commuter trains. Three types of aged grease were categorized based on the total distance that the bearing had traveled, as early life (<0.05 million km [M.km]), medium (0.3–0.6 M.km), and heavily used (1.82 and 2.0 M.km). The microstructure of degraded grease from 20 bearings was characterized in this project using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Base oil of each grease sample was released by a centrifugation method and the oxidation of bled oil was measured by infrared analysis. A notable change in grease microstructure was observed by AFM and SEM. The thickener morphology changed from an entangled helical fibril structure to particle-like nanofragments. The variation in thickener microstructure was observed in the early life grease, which suggested grease can experience an inconsistent aging process in the real-life bearings. Overall, 70.5?±?1.37?wt% base oil bled from the fresh grease, 68.2?±?0.73?wt% from the early life grease, 58.1?±?2.33?wt% from the medium used grease, and 60.0?±?6.35?wt% from the heavily used grease. The results suggest that the densely packed microstructure observed in the aged grease affects the capability of base oil bleeding from the grease. The retardation of base oil flow due to degraded grease may result in the lubricating ability of grease becoming compromised and hence result in an increased wear rate of the bearings.     

分子荧光光谱在原油分析中的应用概述

原油中富含各类芳烃,而分子荧光光谱对芳烃成分非常敏感,因此它是原油定量及定性分析的常用手段,具有灵敏度高、检测限低、操作简单、分析速度快捷等优点。本文以不同荧光光谱分析模式进行分类,通过介绍常规分子荧光光谱、同步荧光、时间分辨荧光等分析手段,对分子荧光光谱在原油分析中的应用做一概述,并对其发展趋势做了展望。     

飞轮储能系统中径向永磁轴承的设计研究

为解决飞轮系统中因轴承摩擦导致的能量损耗问题,设计了一种可以应用于飞轮系统的径向永磁轴承.分别利用Yonnet简化数学模型和有限元分析软件ANSYS Workbench,对轴承中的磁环进行了承载能力的计算和分析.结果表明,磁环所受径向力随磁环厚度、径向偏移量增加而增加,但其增加关系有所不同;另外,随着轴向偏移的增大,径向力逐渐减小、轴向力迅速增大.     

Rotordynamic Analysis of a Shaft Using Magnetorheological and Nanomagnetorheological Fluid Journal Bearings

The rotordynamic behavior of a system supported by journal bearings is critical to its reliability. A suitable method of control of the orbital motion of a shaft in a journal bearing is the use of smart lubricants, in effect fluids with controllable physical properties. There are various categories of smart lubricants. One class of smart lubricants, magnetorheological fluids, are produced as a dispersion of magnetic particles in a carrier fluid, which is usually a conventional lubricant. These particles form chains under the influence of a magnetic field, which hinder the lubricant flow, thus changing its apparent viscosity. Magnetorheological fluids (MRFs) exhibit high yield stress, low delay of response, and relatively low friction while not in their active state. A subcategory of MRFs, nanomagnetorheological fluids (NMRFs) with particle size on the nanometer scale, exhibits lower yield stress than MRFs but display high viscosity. The effect of the MRFs and NMRFs on the rotordynamic behavior of a shaft is calculated through a combined finite element and computational fluid dynamics analysis. Though the MRF with the specific geometrical configuration of the bearing is not sufficiently activated and therefore does not improve the performance of the magnetorheological journal bearing, the NMRF has the ability of limiting up to 82% the amplitude of the vibrations of the shaft.     

微波消解-原子荧光光谱法同时测定中成药中的砷和汞

采用高压密闭微波消解及最新的聚焦微波消解技术消解中成药样品 ,再利用原子荧光光谱法同时测定As和Hg,并与传统的电热板消解方法进行比较 ,结果表明 ,微波消解法RSD % <3% ,回收率 95 .2 %～ 10 2 .0 % ,明显优于电热板法 ,且方法简便、快速、具有良好的过程可控性 ,结果可靠     

基于推力球轴承的点接触弹流润滑分析

研究了推力球轴承的钢球与滚道间形成的椭圆接触等温弹流润滑问题。据此问题建立的数学模型既有沿接触椭圆短轴方向的卷吸速度分量，又有沿其长轴方向的卷吸速度分量，且速度值处处各异。运用多重网格法求得了几组参数下的完全数值解，并分析了转动速度、中心距、椭圆比等参数对结果的影响。     

基于正交试验的静压径向气体轴承数值分析*

以气动涡轮支承结构静压径向气体轴承为研究对象,建立静压径向气体轴承的微分模型,利用工程数值方法计算轴承承载力、刚度和气体质量流量,运用正交试验法研究节流器参数对轴承性能的影响,以及不同优化方向下轴承的综合性能。结果表明：不同的优化方向节流器参数的敏感性不同,以气体质量流量为优化方向明显不符合设计需要,以承载力为优化方向得到的轴承综合性能最好;平均气膜厚度、节流孔直径和数量是影响轴承承载特性的主要因素,节流孔直径越小承载性能越好。     

基于Matlab计算滚动轴承滚滑接触内部应力分布

滚动轴承服役过程中,因滚滑现象和残余应力的存在,使赫兹接触应力不能反映材料真实的受力状态,应力分布与实验现象存在一定的偏差,因此滚滑接触下材料的内部应力计算显得尤为重要。研究一种快速、简单的材料滚滑接触内部应力的计算方法,以替代耗时长的有限元法。以现有公式为基础,通过Matlab编程计算滚滑接触下材料内部的应力场;对比不同摩擦因数下2D、3D滚滑接触内部应力场的差别。结果表明:摩擦因数越大,最大剪切应力越大,位置越接近表面,与滚动方向的夹角越小;切向摩擦力使接触点两侧最大正交切应力大小及位置发生变化;随着摩擦因数增大,一侧应力值上升,位置靠近表面,另一侧反之。提出的计算方法简单、方便,其结果为解析解,便于与残余应力或其他应力结合求出真实应力场。通过实例分析发现,真实应力场能够更好地解释实验现象,对于轴承材料组织演变的研究有重要意义。     

基于滚动蠕滑理论的球轴承摩擦力矩计算方法

基于滚动接触蠕滑理论将球轴承滚动体与滚道的接触问题分解为法向赫兹接触子问题和切向粘滑子问题,提出了基于滚动接触蠕滑理论的球轴承摩擦力矩计算方法,揭示了球轴承滚动体相对内外滚道的滚滑粘着运动特性,解决了球轴承滚动体运动姿态难以确定的问题,为固体润滑/干接触条件下球轴承摩擦力矩的准确计算提供了理论依据。在轴向载荷作用下对采用PTFE保持架全陶瓷Si₃N₄/GCr15/不锈钢球轴承进行摩擦力矩试验,试验结果与计算结果对比表明,球轴承蠕滑分析模型能够得到比较准确的摩擦力矩计算结果,比不考虑滚动接触区粘滑效应的切片离散化模型更准确。     

基于子小波布置和系数融合的轴承故障诊断

针对滚动轴承早期微弱故障特征难以提取的问题,提出一种基于子小波布置策略和小波系数融合的故障诊断方法。首先,布置子小波并进行小波变换;然后,根据峰度指标对多尺度小波系数进行融合集成;最后,运用自相关谱抑制噪声,突出故障信息。通过仿真信号和实际信号对该方法进行了验证,结果表明,该方法能够提取出微弱的故障特征,实现滚动轴承的早期故障诊断。     

基于LabVIEW的磁悬浮轴承的静态刚度测量系统

磁悬浮轴承主要利用电磁力使转子悬浮于定子中,其刚度特性是磁悬浮轴承的重要技术指标,因此磁悬浮轴承的刚度测量是检验磁悬浮轴承性能的必要环节。文中建立了适用于混合控制的磁悬浮轴承在开环控制下的静态刚度测量系统。该系统利用LabVIEW软件开发测量平台,由X-Y-Z电控精密位移台、六自由度力传感器、激光位移传感器及高分辨率电流表等设备组成,并由工控机统一控制各测量单元,实现自动测量、自动采集与数据存储等功能,具有自动化程度高的优点。     

基于ICA和小波变换的滚动轴承故障诊断方法研究

提出了结合独立分量分析(ICA)和小波变换进行滚动轴承故障诊断的方法。在设计的系统平台上,首先对冲击脉冲信号进行预处理,使信号较好地满足独立分量分析的前提条件。然后,应用独立分量快速算法分离故障轴承的冲击脉冲信号,通过小波快速算法完成信号重构,实现滚动轴承故障的识别。实验结果表明,利用独立分量分析方法提取的故障状态特征向量与小波快速算法相结合可以有效、准确地识别滚动轴承的故障信号。     

Tribological study of a mannich compound of 2-mercaptobenzimidazole in liquid paraffin

Tribological study on a 12.7 mm diameter steel ball bearing specimen has been carried out in a four-ball machine using a potentially active heterocyclic additive in liquid paraffin. The synthesis of 2-(di-n-butylaminomethyl) thiobenzimidazole is described. The 2-(di-n-butylaminomethyl) thiobenzimidazole has been found to be quite effective as a potential additive in liquid paraffin according to the results. Employing X-ray photoelectron spectroscopy, the film formed when the additive reacted with the metal was investigated.     

陶瓷球轴承在高速主轴单元中的应用研究

介绍了陶瓷球轴承的特点及其在数控机床高速主轴单元中的应用现状.通过实验研究,对比分析了两种类型主轴单元的温升、振动特性,为HIPSN陶瓷球轴承的实际应用提供了一定的技术依据.     

基于Halbach阵列的永磁轴承承载力解析模型及设计方法

基于Halbach阵列的永磁轴承能有效地增强永磁轴承的承载能力,具有广阔的应用前景。但目前关于Halbach阵列的永磁轴承的理论模型研究并不完善,缺少任意角度连续磁化的Halbach阵列永磁轴承的解析模型和设计方法,限制了其应用。研究针对Halbach阵列的永磁轴承,利用标量磁位的模型建立了永磁体阵列的磁场分布模型,在此基础上基于虚位移法建立了永磁轴承的承载力模型和支承刚度模型,并对永磁轴承的最大承载力和支承刚度特性展开了研究,给出了永磁轴承设计过程中的参考因素。最后利用有限元分析软件对所建立的理论模型和提出的结论进行了验证,取得了较好的效果。     

A Study on the Levitation Control of the Multi-degrees-of-Freedom Rotational Machine Supported by Magnetic Bearings Using Flux Feedback

This paper deals with an open-loop characteristic of a magnetically levitated system including flux feedback. In order to design a controller to obtain a good disturbance rejection and to be insensitive to parameter variations, it might be useful to employ a flux feedback loop. The air gap flux which can be sensed by a proper sensor has linear relationship with respect to the change of the current and the air gap. This linear property decreases the inherent nonlinearity of the magnetic suspension system that is caused by the coupling between the electrical actuator and the mechanical plant. Simulation results achieved from a multi-degree-of-freedom numerical model show that the flux feedback loop makes an improvement of the performance of the magnetic suspension system against the load variations.     

基于临界曲面的改进Paris定律球轴承疲劳寿命预测方法

通过场发射扫描电镜对球轴承疲劳故障点微观结构进行观察,发现裂纹总是沿着某个曲面进行萌生和扩展,扩展到一定程度后发生断裂形成近似椭圆形状的剥落点,随着球轴承的运转,不仅断裂后的裂纹发生二次剥落,而且剥落点将在新的曲面上发生多次剥落,形成断层形貌。基于此种现象,提出球轴承临界曲面的概念,假定裂纹的萌生和扩展均在此临界曲面上,将三维裂纹扩展问题转化为二维裂纹扩展问题进行分析。在临界曲面概念的基础上,提出改进的Paris疲劳寿命预测模型,将疲劳寿命分为裂纹扩展和剥落点增大两部分,分段采用改进的Paris定律预测球轴承的疲劳寿命。通过多套SKF 6205深沟球轴承疲劳寿命试验数据进行验证,与传统的SKF L-P公式预测结果相比,提出的方法能够较好地预测球轴承的疲劳寿命。     

Analysis of High-Speed Cylindrical Roller Bearings Using a Full Elastohydrodynamic Lubrication Model Part 2: Results

The kinematic and dynamic characteristics of high-speed cylindrical roller bearings are analyzed using the elastohydrodynamic (EHD) lubrication model developed in Part I of this two-part paper. The internal load distribution, bearing stiffness, running torque, and amount of roller skidding are calculated under various operating conditions. Effects of manufacturing imperfections are also analyzed in terms of outer-raceway waviness and roller diameter tolerance. Results obtained through case studies indicate that the behavior of the bearing can be significantly affected by EHD lubrication in the roller-raceway contacts.