牵引传动中乏油问题的研究

从弹流润滑到干摩擦状态将润滑条件分为8个阶段对润滑油油量对牵引传动的影响进行了研究，试验中采用Daphne7074牵引油。在低压情况下，牵引曲线上升斜率随着牵引油数量的减少而增大，并且在高压情况下其值接近于干摩擦状态下的值。在低压情况下，最大牵引系数也随着牵引油数量的减少而增大，并且在高压情况下其值接近于干摩擦状态下的值。即使在乏油的情况下(拧干油布润滑)，也能满足牵引传动的要求。     

乏油问题对牵引曲线上升斜率的影响

从弹流润滑到干摩擦状态将润滑条件分为8个阶段对润滑油油量对牵引传动的影响进行了研究，试验中采用Daphne7074牵引油。在低压情况下，牵引曲线上升斜率随着牵引油数量的减少而增大．并且在高压情况下其值接近于于摩擦状态下的值。乏油运转后，最大牵引系数的变化不明显。即使住乏油的情况下(拧干油布润滑)．也能满足小结构牵引传动的要求。     

稀土化合物改性复合材料在油润滑下的摩擦学性能

以竹纤维为增强相,通过稀土化合物改性制备一种树脂基复合材料;采用环块式摩擦磨损实验,研究稀土化合物改性复合材料在油润滑状态下载荷、转速对试样摩擦学性能的影响,以及稀土化合物改性对复合材料试样摩擦学性能的影响;比较干摩擦状态和油润滑状态下复合材料的摩擦学性能,观察和分析试样磨损表面形貌,探讨其磨损机制。实验结果表明:油润滑条件下,稀土化合物改性复合材料的摩擦因数和磨损率都随着载荷的增大而增加;较高载荷下摩擦因数随着转速的增大先增加后减小,而磨损率则呈现逐步增加的趋势;稀土化合物的改性使竹纤维和基体界面结合更为紧密,提高摩擦因数的同时降低了磨损率;在油润滑作用下,试样磨损由干摩擦时的磨粒磨损和疲劳磨损转变成为轻微的疲劳磨损;在油润滑状态下,复合材料处于边界润滑状态,故摩擦因数和磨损率均低于干摩擦。     

干摩擦状态滑动螺旋传动耐磨性分析

滑动螺旋传动在油润滑状态下,耐磨性能可以满足,在某些不能使用油润滑的干摩擦状态下,往往会发生严重的粘着。分析了干摩擦状态的材料表面和材料硬度,进行了耐磨性校核和摩擦转矩的计算,从理论上解释了干摩擦状态耐磨性能不足的原因。针对螺旋副的耐磨、润滑要求,从干膜润滑、表面强化等方面提出了提高耐磨性措施。干膜润滑、化学镀镍、类金刚石涂层和双线螺纹都可提高滑动螺旋传动的耐磨性,结合使用工况合理选择,可提高材料的抗粘接和"咬死"的能力。     

汽车电动轮牵引传动减速器滑动特性分析

为分析汽车电动轮牵引传动减速器的滑动特性,在研究了该减速器工作机理的基础之上,结合弹流润滑理论建立了精确计算其滑动特性的数学模型和分析方法,揭示了滑动率和传动功率的关系,探讨了压紧力和摩擦副长度对滑动特性的影响。研究结果表明,在相同滑动率下,增大压紧力有利于增大牵引油黏度和极限剪应力,从而提高输入输出功率;在相同压紧力下,随着滑动率不断增大,输入输出功率先逐渐增大,最终输入功率趋于稳定,而输出功率在达到峰值后出现减小的趋势;在相同压紧力和滑动率下,随着内或外摩擦副长度不断减小,输入输出功率先逐渐增大,最终各自趋向一个稳定值。     

20CrMnTi钢齿轮磨削表面的摩擦磨损试验研究

为了研究不同粗糙度表面、载荷与摩擦频率对20CrMnTi钢齿轮磨削表面的摩擦磨损性能影响规律和机理,分别在干接触状态与润滑接触状态下开展了往复滑动摩擦磨损试验。研究结果表明:摩擦系数随着接触表面粗糙度和载荷的增大而增大,但随着摩擦频率的增大而减小;磨损深度随着表面粗糙度、载荷和摩擦频率的增大而增大。因此,在干接触与润滑接触两种状态下,不同粗糙度表面、载荷与摩擦频率对摩擦学特性的影响机制均存在显著的差异。     

聚酰亚胺对聚四氟乙烯基自润滑复合材料摩擦磨损性能的影响

研究了不同聚酰亚胺(PI)含量的聚四氟乙烯(PTFE)基自润滑复合材料的摩擦磨损性能,并分析了干摩擦和预浸油润滑两种条件下的磨损表面形貌和磨损机理.研究表明:PI的加入在于摩擦状态下能显著提高复合材料的减摩性能,并且随着含量的增加效果更加明显;但其抗磨损作用并不明显,其磨损量取决于复合材料的协同作用,而玻璃纤维和MoS2减磨作用明显;在预浸油润滑条件下,由于油润滑占主导地位,复合材料基体减摩效果不能充分体现.     

半金属基粉末摩擦片摩擦磨损性能研究

在不同工况下研究半金属基粉末摩擦片与淬火45#钢配副时,载荷和转速对其摩擦磨损性能的影响,并分析其磨损机制。结果表明,在油润滑和水润滑下,半金属基摩擦片高速下的磨损量要明显低于低速下的磨损量,而干摩擦下其高载高速下的磨损要高于高载低速时的磨损量。油润滑下随载荷的增大,半金属基摩擦片的摩擦因数逐渐升高;水润滑下随载荷的增大,高速时摩擦因数先增大后减小,低速时则逐渐降低;干摩擦下随载荷的增大,高速时摩擦因数呈现出先升高后降低再升高的趋势,低速时则先升高后降低。干摩擦时摩擦面十分粗糙,有比较明显的沟状磨痕和硬质颗粒脱落后残留的凹坑;而水润滑和油润滑时摩擦面较为光滑。     

离子渗硫层在油润滑条件下的转动微动摩擦磨损性能

利用低温离子渗硫技术在LZ50钢表面制备渗硫层,在干摩擦和油润滑条件下开展不同角位移幅值的渗硫层转动微动磨损试验,并利用扫描电子显微镜、能谱仪和轮廓仪对磨斑进行微观分析。试验结果表明:与干摩擦相比,油润滑条件下离子渗硫层呈现出不同的微动运行工况图,部分滑移区和滑移区的界限向左移动,滑移区的运行范围增大;在部分滑移区,渗硫层在油润滑条件下的摩擦因数几乎不变,且明显低于干摩擦,损伤十分轻微;在滑移区,渗硫层在油润滑条件下的摩擦因数仍低于干摩擦,呈现"初始-爬升-稳定"3个阶段,其磨损机制为磨粒磨损和剥层。     

冲击滑动条件下MoS2固体润滑薄膜的磨损

为了减少和避免滚动轴承保持架与套圈接触表面的冲击滑动磨损,Mo S2等固体润滑膜被广泛用于轴承保持架表面和套圈引导面的润滑改性。为研究冲击滑动条件下Mo S2固体润滑薄膜的摩擦磨损特性,在自制的冲击滑动磨损试验装置上,在干摩擦及油润滑条件下对9Cr18轴承钢表面制备的Mo S2固体润滑膜进行不同冲击频率、冲击力和滑动速度下的摩擦磨损试验。结果表明,Mo S2固体润滑膜的失效模式主要受润滑状态和冲击力的影响,随着冲击力及冲击频率的增加,Mo S2固体润滑膜表面摩擦力矩增大,且油润滑比干摩擦下摩擦力矩显著减小;黏结工艺加工的冲击试样表面失效以疲劳裂纹及剥落为主,喷涂工艺加工的回转试样则展现出稳定的表面磨损。     

Evidence of lubricant slip on steel surface in EHL contact

The limiting traction provided by typical elastohydrodynamically lubricated (EHL) contacts leads to the postulation that liquid lubricants are subject to limiting shear stress, which is generally accepted as an intrinsic property of the lubricants. The results of recent optical EHL research show that lubricant at EHL contacts may slip on the Cr-coated glass surface under certain circumstances. This paper presents further evidence that high pressure EHL film can slip on a steel surface. Because the steel/steel contacts are common in typical traction drives and the interfaces are therefore oil/steel, the deduction of the limiting shear stress of lubricants from the measured limiting traction may simply reflect a property of the system should boundary slippage occur.     

极限剪切状态下的线接触Reynolds方程

本文导出了考虑极限剪切状态的线接触流变热弹流Reynolds方程,该方程以Evans—Johnson流变模型为基础,可用于求解线接触流变热弹流润滑问题的油膜厚度、压力分布、剪应力分布和牵曳系数曲线。计算实例表明,润滑油的流变特性对弹流润滑的油膜形状和压力分布影响不大,但对Hertz接触区的剪应力分布有显著影响。     

Experimental and computational investigation of the traction coefficient of a ball traction drive device

Traction drive is a new kind of drive manner in which the power is transmitted by a thin oil film between transmission elements. This paper describes a ball traction drive device. The quasi-dynamics analysis was carried out for the transmission components of the ball traction drive device. The traction coefficients of oils Ub2 and HH-20 were calculated respectively with different rheological models. The elastohydrodynamic lubrication (EHL) film thickness and the traction coefficient between traction drive elements were measured. The results of the calculations are consistent with experiments.     

A non-averaging method of determining the rheological properties of traction fluids

Traction machines have been frequently used to study the rheological responses of lubricants in elastohydrodynamic lubrication (EHL) contacts. Fundamental properties are inferred from EHL traction measurements based on the average pressures and temperatures in the contact. This average approach leads to uncertainty in the accuracy of the results due to the highly nonlinear resonse of the fluid such as viscosity to both pressure and temperature. A non-averaging method is developed in this paper to study the elastic and plastic properties of traction fluids operating in EHL contacts at small slide-to-roll ratios. A precision line-contact traction rig is used to measure the EHL traction at a given oil temperature and Hertz pressure. By choosing a sensible pressure-property expression, the parameters of the expression can be determined through the initial slope and peak traction coefficient of the traction measurements. The elastic shear modulus and the limiting shear stress of the lubricant corresponding to a single pressure can then be calculated for a range of pressures and temperatures of practical interest. Two high-traction fluids are studied, and their elastic moduli and limiting shear stresses presented.     

Stress Analysis on Layered Materials in Point Elastohydrodynamic-Lubricated Contacts

For multilayered or coated substrates in elastohydrodynamic-lubricated (EHL) contacts, the subsurface stress distributions under a normal load combined with shear traction have been analyzed in this article through computer simulations. The Papkovich-Neuber potentials and Fourier transform are adopted to deduce the pressure–displacement, pressure–stress, and shear traction–stress response functions in frequency domain for the coated substrates, and to calculate distributions of pressure and subsurface stress. The results from the analysis of EHL contacts on coated substrates are compared with those from dry contact model in which shear traction is assumed to obey Coulomb’s law. Effects of the Young’s modulus of coatings, the properties of lubricants, and the magnitude of traction are discussed. Similar to the results in dry contacts, hard coatings in lubricated cases tend to increase the von Mises stress, whereas soft coatings decrease the stress. Shear traction makes the max von Mises stress increasing and moving closer to surface. However, the changes in subsurface stress due to shear traction are less obvious in lubricated contacts. Comparison between EHL and dry contact models reveals that lubrication can reduce the von Mises stress in the coating layer due to smaller shear traction. The analyses show that pressure, film thickness, and subsurface stress distributions are influenced by surface coatings, sliding velocity, rheological models, and pressure–viscosity behaviors.     

High‐pressure short time behavior of traction fluids

The squeeze film formation ability of traction fluids is studied under impact load by dropping a steel ball‐bearing against a flat anvil made of mild steel. The effect of the pressure–viscosity coefficient and of the viscosity is investigated for plastic impact. The depth difference between the lubricated surface dent and the dry dent increases linearly with the product αη of the pressure–viscosity coefficient α and the viscosity η. The importance of the lubricant parameter αη is observed under the squeeze film formation ability from contact voltage or elastohydrodynamic lubrication central film thickness measurement at rolling condition. The intensity of each impact collision is measured by means of an acoustic emission (AE) sensor. The high‐pressure short‐time solidification of traction fluids was confirmed by dent analysis after the impact tests and AE analysis under impact loads. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of EHL Contact Conditions on the Behavior of Traction Fluids

New infinitely variable transmission (IVT) systems are under development for the automotive industry as a means to achieving significant fuel economy benefits. These systems rely on the lubricating fluid to transmit the drive train loads across the interface of the transmission components. This requires the development of new fluids that exhibit high traction properties under elastohydrodynamic lubrication (EHL) conditions. However, it has been reported recently that the traction performance of some fluids can reduce dramatically as temperature is reduced. This may place severe operational limits on IVT systems and suggests that the low-temperature traction properties of fluids for these systems should be studied in order to understand the mechanism for the observed reduction in traction.

The work reported here is an experimental study aimed at identifying whether low temperature traction reduction is related to a fundamental change in rheological behavior specific to the fluids tested or to more generic changes in the EHL contact conditions. A series of model experiments were performed using a mini traction machine (MTM) on three high-viscosity polybutene samples. The results have been mapped against previously reported non-dimensional parameters used to identify different EHL regimes. The results show that dramatic reductions in traction occur when the contact transitions from the rigid piezo-viscous (RP) toward the rigid iso-viscous (RI) region. Similar results were also found for two other high-viscosity fluids of different molecular structure and lower traction properties. The results support the hypothesis that the reduction in traction observed at low temperature is due to a change in EHL contact conditions rather than being solely due to a change in the rheological performance of the test fluids.     

对数母线滚子光弹流润滑的实验研究

为了研究对数母线滚子凸度量对滚子摩擦副润滑油膜的影响 ,本文在自制的有限长线接触光干涉弹流试验机上 ,测量了中载、富油润滑和纯滚动工况下对数修形圆锥滚子与玻璃盘之间的油膜形状与膜厚。实验结果表明对数母线轮廓滚子的凸度量对其端部的油膜厚度和膜形分布有较大的影响 ,在给定的工况条件下 ,存在一个使滚子轴向油膜厚度最为均匀的最佳凸度量 ,此最佳凸度量比在相同工况条件下用静弹性接触力学方法求得的最佳凸度量大     

链条套筒与销轴铰链副冲击载荷-往复运动的弹流润滑数值模拟

数值模拟链传动中销轴与套筒之间的定载荷和变载荷弹流润滑接触问题,套筒相对于销轴做纯滑动往复运动。定载荷是假定往复运动过程中载荷恒定不变;变载荷是假定链节在啮入和啮出链轮过程中存在的冲击载荷按正弦函数规律变化。比较在定载荷和变载荷加载条件下线接触往复运动工况的弹性润滑油膜变化情况,分析在动载荷加载条件下不同行程长度对弹性流体动力润滑特性的影响。研究发现,动载荷对油膜的压力、膜厚影响较大:随着动载荷的增加,油膜中压力急剧增大,膜厚减小;但加载方式对摩擦因数的影响不大;在相同的加载方式下,随着行程长度的增加,油膜压力减小,中心膜厚和最小膜厚显著增加。