Experimental Investigation of Lubrication Film Starvation of Polyalphaolefin Oil at High Speeds

The lubrication behavior of starved elastohydrodynamic contacts at high speeds was investigated in this study. A new ball-on-disc test rig with the ability to measure traction force at high speeds up to 100 m/s and lubrication film thickness at speeds up to 42 m/s was built. The relative optical interference intensity technique was used to measure the film thickness. The experimental results show that the film thickness decreased rapidly and asymmetrically when the speed exceeded a critical speed under the starved lubrication condition. Starvation is governed by the amount of lubricant available both in the inlet region and on the side of the oil reservoir. The shape of the oil reservoir becomes asymmetric and the amount of oil gradually reduces against the speed at high speeds because of the centrifugal effects, under which the oil on the outer side of the oil reservoir will be thrown away and the oil on the inner side of the oil reservoir will be compressed. The balance of oil supply and oil loss due to centrifugal force determines the starvation behavior.     

Experimental Investigation of Lubrication Properties at High Contact Pressure

A new test rig with an ability to obtain clear interference images at high pressure contacts has been developed. The technique of relative optical interference intensity has been used to obtain film thickness profiles and then lubrication properties of some base oils including six kinds of polyalphaolefin and four kinds of silicone oil have been studied at different pressures ranging from 1 to 3 GPa. The results show that viscosities of these lubricants have notable effect on slopes of film thickness curves (speed versus film thickness in log–log form), and the observed phenomenon is attributed to fluidity and molecular structure. A comparison of experimental central film thicknesses with computational work shows that at high loads the relationship between load and film thickness usually go against prediction given by Hamrock and Dowson. In addition, when more pressure is applied, the profiles of film thickness become more and more flat while rolling speed do little to change the shape of profiles.     

Solid Film Lubrication at High Temperature

The behavior of several solid film lubricants has been experimentally established as a function of temperature. These films are formed of a suspension of lubricant particles (graphite, molybdenum disulfide) in a thermosetting resin baked onto a hard surface. The test consists of heating such a layer and continually observing the friction coefficient until failure. Sliding conditions of high unit loading and low rubbing velocity were chosen to provide a comparison between the films. They were evaluated as to the highest temperature for which the friction coefficient remained low and subsequently as to the number of load cycles sustained at temperature before an abrupt increase in friction. Results for all films were similar in that failure was caused by a breakdown of the binder rather than the lubricating particles and that the minimum friction coefficient (～ 0.03) was observed just before the film failure at temperatures as high as 1200° F.     

润滑油膜电磁损伤故障的机理及防治方法

以PWM变频凋速高速电主轴为研究背景，建立了诱发润滑油膜电磁损伤故障的共模电压的物理模型，分析了润滑油膜在共模电压作用下发生放电导致油膜劣化的物理化学机理，系统地提出了抑制润滑油膜电磁损伤故障的方法和途径。     

变黏度静压滑动轴承高速时油膜动态润滑特性

静压滑动轴承转台直径大（D=4.5 m）,高转速运行时产生线速度值很大,其内部润滑油膜受压及剪切发热导致油膜变薄进而影响到机床加工精度和运行可靠性。针对新型Q1-205双矩形腔静压推力轴承,采用动网格技术探索变黏度条件静压轴承高速时的油膜动态润滑特性。建立该静压轴承的流量、承载力、油膜温升等理论模型,自定义用于控制边界层网格运动及变黏度的UDF程序,选取外载荷12 t,转速为80~200 r/min（线速度18~48 m/s）高速下的工况条件参数进行动态润滑特性数值模拟,并进行相同工况参数下的试验验证,揭示出高速时油膜厚度变化对油膜温度、油腔压力、封油边处流量的影响规律。研究发现,该型号轴承在承载12 t时,随着膜厚的减小,油膜剪切发热严重,温升加剧,且高速下受润滑油黏度变化影响造成压力损失严重,研究数据为工程上静压轴承可靠运行提供理论依据。     

高分子添加剂的润滑性能实验研究

以机械油为基础油,采用摩擦磨损试验机,对多种高分子添加剂对润滑油润滑性能的作用进行实验研究。结果表明,少量的高分子添加剂对增加润滑油的黏度作用不明显,而润滑油的承载能力及抗磨性能有一定的提高;高分子添加剂分子量越大其摩擦因数降低相对明显,且在低速条件下比高速条件效果明显。     

润滑状态转化过程中固体转移膜的试验研究

本文探寻高速齿轮在干摩擦条件下能形成转移润滑膜的材料，并用实验方法测试了各种转移润滑膜的摩擦学特性及耐久性，为高速齿轮在干摩擦条件下正常运转提供依据。     

The Behavior of Surface Roughness in EHL Contacts Under Small Slide to Roll Ratios

The amplitude attenuation theory represents a possible way how to predict the tribological performance of a surface having general roughness. There are applications of this theory for pure rolling and rolling?Csliding conditions having different governing parameters. Obviously, pure rolling case is much simpler and it was already experimentally verified. Conversely, rolling?Csliding conditions represent much complex case and its solution is still under development. Nevertheless, a lot of machine components operate under the conditions where only small slide to roll ratios are present. This study was carried out to find the reasonable validity of the pure rolling model for the applications where small amount of sliding is present. The behavior of roughness was observed under conditions of small sliding speed using optical tribometer for film thickness mapping. The results were analyzed and compared with the predictions according the amplitude attenuation theory for both pure rolling and rolling?Csliding cases. The influence of slide to roll ratio on roughness profile shape was studied and differences to the pure rolling profile were evaluated. It was concluded that the pure rolling model can be applied with reasonable precision within the range of slide to roll ratios from ?0.15 to 0.1. The correlation coefficients are better than 0.85, the RMS value changes are less than 3?%, and bearing area curves are almost unaffected.     

飞机滑油系统故障分析

在分析飞机滑油系统工作原理的基础上，对某型飞机滑油系统中存在的一些故障，包括滑油变色或混有金属屑、滑油消耗量超过规定、系统漏油外部漏油、滑油箱油量增多、滑油箱油量减少等进行了分析，并相应提出了在使用和维护中应注意的问题，为航空机务维护实践提供有益的借鉴。     

Experimental Investigation of Elastohydrodynamic (EHD) Film Thickness Behavior at High Speeds

At very high speeds, elastohydrodynamic (EHD) films may be considerably thinner than is predicted by classical isothermal regression equations such as that due to Dowson and Hamrock. This may arise because of viscous dissipation, shear thinning, frictional heating or starvation.

In this article, the contact between a steel ball and a glass disc over an entrainment speed ranging from 0.05 m s^?1 to 20 m s^?1 was studied. Two sets of tests were performed. In the preliminary testing, the disc was driven at speeds of up to 20 m s^?1 and the ball was driven by tractive rolling against the disc, its speed being determined using a magnetic method. After all possible explanations for the reduction in film thickness at high speeds were considered, it was shown that the results, which fall well below classical predictions, are consistent with inlet shear heating at the observed sliding speeds.

Another set of tests was then performed, with both disc and ball driven separately, so that the accuracy of the shear heating theory for different types of oils and at different sliding conditions could be assessed. It was found that the thermal correction factor predicts the trend of film thickness behavior well for the oils tested and is particularly accurate at certain slide–roll ratios (depending on the type of oil). Experimental data were also used to obtain improved coefficients for the correction factor for different types of oil to achieve better prediction of film thickness at high speed throughout the whole range of slide–roll ratios.     

液体静压导轨油膜厚度的控制方案

介绍了液体静压导轨的工作原理,提出了基于直流调速和矢量变频调速的两种油膜厚度控制方案,并比较了两种方案的优缺点。研究结果表明：采用矢量变频调速的油膜厚度控制方案。在保证控制精度的同时,可以使系统的成本降低,系统的可维护性和节能效果更好。     

液体静压导轨油膜厚度的控制方案

为了保证在不同栽荷条件下,机床静压导轨具有良好的运动精度和低速平稳性,必须对液体静压导轨的油膜厚度进行有效的控制.在介绍了液体静压导轨的工作原理后,提出了基于直流调速和矢量变频调速的两种油膜厚度控制方案,并比较了两种方案的优缺点.研究结果表明:采用矢量变频调速的油膜厚度控制方案,在保证控制精度的同时,可以使系统的成本降低,系统的可维护性和节能效果更好.     

高接触压力下齿轮油润滑特性

在重载条件下工作的润滑剂常常会受到高接触压力的影响,有时会导致润滑剂本身性质发生改变从而造成摩擦副失效,但目前对高接触压力条件下润滑剂性能的研究还不多。利用自制的新型膜厚测量仪测量GL-5型齿轮油在不同卷吸速度和接触压力下的干涉图像,并计算得到膜厚曲线进行成膜性能和润滑特性分析。结果表明,在低速重载的情况下GL-5齿轮油有较好的成膜能力;在高接触压力下,油膜形状呈平坦状分布,有助于减小压力峰值;随着接触压力的增加,由Hamrock-Dowson理论算得的膜厚值和实测值逐渐开始偏离,理论公式中卷吸速度和载荷的指数需要调整。     

Effects of Slide/Roll Ratio on the Behaviours of Grease Reservoir and Film Thickness of Point Contact

The film formation mechanism of lithium complex grease under starved condition was proposed based on the analysis of the relationship between grease reservoir and the finger-shaped lubricant along the rolling track using a laboratory built ball-on-disc test rig. Film thicknesses with rolling time at different slide/roll ratios were measured and discussed in detail. Experimental results showed that starvation occurred soon after the operation under pure rolling condition. In contrast, the contact remained fully flooded under slide–roll condition. The measurement of grease fingers proved that slide/roll ratio contributed to replenishing the contact by transferring more grease to the vicinity of the contact to form a lager lubricant reservoir. The volume of grease fingers, the inlet lubricant supply and the film thickness at different slide/roll ratios were found to be in good agreement.     

薄膜油润滑中电粘度效应影响研究

利用组合滑块油润滑试验考察了双电层的电粘度效应对薄膜润滑性能的影响，采用施加外加电场和添加添加剂两种方法以改变润滑剂中离子浓度进行试验研究。结果表明：双电层引起的电粘度效应对摩擦因数有明显影响，摩擦因数随着外加电场的增强而变大，当外电场增大到一定程度时摩擦因数开始减小；在离子浓度较小时，摩擦因数随着离子浓度的增加而增大，当离子浓度增大到一定程度时摩擦因数开始减小。     

机床液体静压导轨油膜厚度确定的研究

从功率损失、油膜刚度等方面,介绍了机床液体静压导轨最佳油膜厚度的确定方法,对实际油膜厚度的设计具有指导意义.     

动压油膜轴承润滑技术设计分析

简述油膜轴承润滑系统的工作原理及其设计原则.     

应用于主动控制油膜轴承的超磁致伸缩驱动器的实验研究

针对传统油膜轴承位置精度低和稳定性差的问题,研究开发了应用于主动控制油膜轴承的超磁致伸缩驱动器.设计并搭建了试验台,实测了驱动器的静态性能和动态性能.实验结果显示超磁致伸缩驱动器在常态磁场强度下可以产生与油膜厚度同一数量级的位移输出和较宽的静态调节范围;在2 000 Hz的激励电压作用下有良好的频响特性.说明所研制的超磁致伸缩驱动器能够用来控制油膜轴承的间隙,满足油膜轴承所支承转子的减振频率需要.     

齿轮润滑中PV曲线新特性及计算模型

大量资料表明,预测齿轮胶合常用的PV曲线在较宽的速度范围内具有抛物线型特征,过去还没有一种理论能对此作出合理的解释,本文根据齿轮润滑中不同的节线速度范围提出了反应膜的机械磨损和化学分解两种失效机理,进而对这两种机理作出了定量描述。在此基础上建立了一个综合计算模型,即胶合载荷与节线速度间是近似的二次函数关系,该综合模型与有关文献的试验结果相一致。本文为PV典线的高—低—高变化规律提供了合理的解释。     

油膜厚度对闭式液体静压导轨性能的影响

为了研究油膜厚度对静压支承的影响,以闭式液体静压导轨为研究对象,确定了导轨系统的初始参数;基于力平衡方程及流量方程,建立了功率损失、静态性能、动态性能的数学模型;将总功率损失、承载能力和静刚度、固有频率、调整时间和动刚度等参数作为导轨的性能指标,利用MATLAB软件定量分析了油膜厚度对导轨性能的影响。研究结果表明：增大油膜厚度,则液体静压导轨的总功率损失增大,调整时间变长,承载能力不变,静刚度、固有频率及动刚度减小。因此,减小油膜厚度,可降低导轨总功率损失,提高静态性能和动态性能。研究结果为工程实际中闭式液体静压导轨静压油膜的设计提供了理论依据。