Lubricant oils additivated with polymers in EHD contacts: Part 2. Tests using a four‐ball machine

A mineral oil of low viscosity was additivated with different concentrations of low‐density polyethylene. The wear behaviour of the additivated samples and the base oil was evaluated using a four‐ball wear tester at constant speed and variable load. Steel and ceramic (silicon nitride) were chosen for the balls. The scuffing resistance of the ceramic balls was higher than that of the steel balls. No scuffing appeared in the case of an upper steel ball in contact with lower ceramic balls. As far as the minimum wear‐scar diameter on the lower balls was concerned, an optimum concentration of polymer added to the base oil was found from the experimental data, for both types of ball. For the systems investigated, the optimum concentration was about 1.0% polyethylene.     

圆锥滚子轴承有效壁厚计算程序的开发

轴承套圈有效壁厚其选材和热处理工艺的制定具有重要意义。而类似于圆锥滚子轴承之有效壁厚往往不能一目了然,对于此问题可使用部分程序软件使其计算过程程序化,以达输入部分参数,瞬间即可得其结果之效,从而提高工作效率。     

基于弹流润滑的圆锥滚子球基面曲率半径优化设计

根据圆锥滚子轴承的运动学原理,建立圆锥滚子球基面-内圈大挡边的运动学模型,得到圆锥滚子的自转速度、公转速度和圆锥滚子球基面-内圈大挡边接触区域的卷吸速度分布;建立圆锥滚子球基面-内圈大挡边弹流润滑的数学模型,计算分析在不同载荷和卷吸速度作用下,圆锥滚子球基面曲率半径对油膜厚度和摩擦因数的影响规律,并得到载荷与速度对圆锥滚子球基面最优化曲率半径的影响规律,即当其他工况条件不变时,圆锥滚子球基面所承受的载荷越大,其最优化的曲率半径就越大;速度越高,最优化的曲率半径则越小。     

Performance of synthetic oils in the hydrodynamic regime ‐ II. Generalisation

In Parti I the results of an extensive experimental investigation of the performance of environmentally adapted oils in the hydrodynamic regime were reported. Four oils were tested in a tilting‐pad thrust bearing for different combinations of load, shaft speed, and supply oil temperature. In this second part, details of a generalisation procedure are described. A number of parameters representing the physical properties of an oil, such as viscosity and viscosity‐temperature coefficient, are adopted. The influence of each of these parameters on minimum oil film thickness, maximum temperature rise, and bearing power loss is then analysed. It is shown that viscosity measured at the supply oil temperature is the most important parameter. The effects of the viscosity‐temperature coefficient and oil thermal conductivity are less pronounced and yet significant. It is also shown that it is not possible to select an optimum oil that yields maximised oil film thickness, minimised temperature rise, and minimised power loss at the same time.     

汽车驱动桥主减速器圆锥滚子轴承滚子接触应力分析

对汽车驱动桥主减速器圆锥滚子轴承进行弹性流体动力润滑分析,根据润滑油的物理参数和滚子承受的载荷,求出了油膜压力和摩擦因数。然后利用有限元软件对受载荷最大的滚子进行了有限元分析,得出了滚子在外部载荷和惯性力作用下的接触应力分布,得出驱动桥主减速器工作时的惯性力对圆锥滚子轴承的影响是必须考虑的因素。     

Lubricant oils additivated with polymers in EHD contacts: Part 1. Rheological behaviour

This paper reports on the influence of a polymer additive on the traction behaviour of a mineral oil investigated using a two‐disc machine at different temperatures and contact pressures. A semi‐empirical approach was used for determining the effective lubricant rheological parameters ‐ the elastic shear modulus, the viscosity of the lubricant, and the limiting and Eyring stresses ‐ in elastohydrodynamic contacts. Using this approach, the effect of polymer concentration on the rheological parameters that appear in both the Johnson‐Tevaarwerk and Bair‐Winer models was quantified. The influence of operating conditions, such as pressure, oil temperature, and polymer concentration, on the traction coefficient, limiting shear stress (from the Bair‐Winer model), Eyring stress (from the Johnson‐Tevaarwerk model), shear modulus, and apparent viscosity was also investigated.     

Viscosity–pressure–temperature behaviour of mineral and synthetic oils

A new high‐pressure viscometer that can measure viscosity at pressures up to 0.8 GPa has been developed in the authors' laboratory. The ‘modulus equation’ has been used to compare the behaviour of mineral and synthetic lubricants. Among the oils investigated there was one ester that biodegraded rapidly both before and after ageing in a long‐term test‐rig operation. To facilitate a comparison or application of the results to other oils, an analysis of the correlation between the viscosity—pressure coefficient and the kinematic viscosity measured at atmospheric pressure has been provided. A prediction of lubricant film thickness based on high‐pressure viscosity data is compared with film thickness measurements in a roller bearing.     

A study of the rheological behaviour of multigrade oils

The rheological behaviour of four blends of multigrade oils containing different commercial viscosity index improvers has been studied for increasing shear rate and temperature. Polyalkylmethacrylate has been found to demonstrate different behaviour to styrene-isoprene, styrene-butadiene and ethylene-propylene copolymers. Oil blends for all these hydrocarbon copolymers have shown non-Newtonian behaviour with increasing shear rate (0 to 35,000 s⁻¹) at low and moderate temperatures (−15 to 40°C), i.e. their viscosities were subject to a significant decrease, while the viscosity of the polyalkyl-methacrylate blend showed a limited decrease. With increasing shear rate at high temperature (100°C), all the formulated blends behaved as Newtonian fluids, i.e. with nearly constant viscosities. Increasing shear rate can also change the behaviour of some hydrocarbon copolymers from thickeners to viscosity index improvers.     

圆锥轴承内圈大挡边与滚子基面摩擦和噪声分析

通过对设计和设备的改进,内圈大挡边与滚子球基面之间的滑动摩擦及滑动摩擦部位的振动噪声都得到很大地改善。     

Rheological properties of high‐viscosity‐index mineral base oils for automotive engine lubricants

Viscosity‐pressure‐temperature relations for paraffinic mineral base oils at pressures up to 0.7 GPa and temperatures between 30 and 90°C were determined using a falling‐ball‐type viscometer. The oils used were solvent refined oils, hydrocracked oils, and an oil produced by a wax isomerisation process. The viscosity at pressures higher than those possible with the viscometer was then derived by applying a simplified solution to the traction curves determined using an elastohydrodynamic disc‐on‐ball tester. When the measured viscosity and the calculated viscosity were plotted against pressure, for the oils with a viscosity index higher than 120 the viscosity derived from traction measurements followed the curve extrapolated to the high‐pressure region using either the Yasutomi or Roelands equations (the parameters for which were obtained using the viscometer). However, the calculated viscosity for the lower‐viscosity‐index oils deviated upwards from the extrapolated curve.     

Correlation of structure and properties of groups I to III base oils

The understanding of the relationship between molecular structure and viscosity–temperature behaviour of a lubricant system is a subject of considerable importance. The quantitative distribution and types of different classes of hydrocarbons such as aromatics, paraffins (normal and iso) and naphthenes determine the physico‐chemical behaviour of a lubricant system. The study of molecular structure and molecular alignment of hydrocarbons constituting a lubricant helps in the development of lubricating oil with desired physico‐chemical properties. The present study highlights the application of nuclear magnetic resonance spectroscopic technique for deriving detailed hydrocarbon structural features present in API groups II and III base oils produced through catalytic hydrocracking/isodewaxing processes. The viscosity–temperature and viscosity–pressure properties, such as viscosity index, pour point, elastohydrodynamic film thickness and cold cranking simulator viscosity, were determined. The structural features of these base oils such as various methyl branched structures of isoparaffins and branching index, which are characteristics of high performance molecules, were correlated with the above‐mentioned properties to explain their physico‐chemical properties, particularly low temperature properties. The molecular dynamics parameters such as diffusion coefficient and T₁ relaxation times estimated from the nuclear magnetic resonance spectral studies have provided sufficient evidence for the dependence of these properties on these high performance molecules present in various types of methyl structures of isoparaffins of groups II and III base oils compared with conventional group I base oils. Results are explained on the basis of molecular structural differences of hydrocarbons present in these base oils and diffusion measurement studies. On the basis of the studies, molecular engineering concept for the designing of a high performance base oil molecule is proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

圆锥滚子轴承内圈滚道磨削和质量控制

圆锥滚子轴承内圈滚道存在凸滚道和直滚道两种磨削方式,内滚道的磨削加工要根据产品性能要求控制滚道有关尺寸、精度等各质量参数,对凸滚道要检查滚道凸出量、凸出形状和位置。     

Partial EHL analysis of rib-roller end contact in tapered roller bearings

A partial EHL analysis was performed for the tapered rib/spherical roller end contact in tapered roller bearings. The average Reynolds equation, the elasticity equation and the pressure-viscosity relation were solved simultaneously. The effects of the surface roughness as well as the peculiar geometrical and kinematics parameters of the rib-roller end contact on the friction torque and film thickness were investigated. The optimal ratios of radius of curvature of roller end to rib face were deduced, which confirm the previous finding with the theory of smooth surfaces. The significant range of surface roughness, and the optimal surface roughness for the roller big end were obtained. It was found that asperity contacts extend into the outlet zone. The results are significant for the design of rib faces and roller ends. The theoretical treatment is validated by its good correlation with the existing experimental data for smooth surface contact.     

Temperature rise of double-row tapered roller bearings analyzed with the thermal network method

Based on generalized Ohm׳s law, the thermal network model (TNM) is developed for double-row tapered roller bearing lubricated with grease, which is commonly used in high-speed railway. The load distribution and kinematic parameters in bearing are obtained by developing a quasi-static model. The temperature of bearing at different speeds, filling grease ratios and roller large end radius are investigated. The results show that large rotating speed and filling grease ratio result in high temperature rise, especially at roller large end/flange contacts. Besides, an optimal roller large end radius is presented and its mechanism has been explored.     

Effect of chemical structure on film‐forming properties of seed oils

The film thickness of seven seed oils and two petroleum‐based oils of varying chemical structure was investigated by the method of optical interferometry. The measured film thickness (h_meas) was then compared to that calculated using the Hamrock–Dowson (H‐D) equation. The result showed that the H‐D equation adequately and without exception predicted h_meas in the high entrainment speed region but not in the low entrainment speed region. In order to understand these deviations further, the chemical structural variabilities of the oils were quantified using empirical parameters, and its effect on film thickness in the low entrainment speed region was examined. The result of this examination indicated that, in the low entrainment speed region, the film thickness of seed oils (i) rarely correlates with viscosity as proposed by the H‐D equation, (ii) increases with decreasing polarity of the oil, and (iii) increases with decreasing degree of unsaturation of the oils. Published in 2008 by John Wiley and Sons, Ltd.     

发动机圆柱滚子轴承载荷分析及刚度计算

在发动机圆柱滚子轴承拟静力学分析的基础上,建立了基于轴承径向游隙和油膜厚度的圆柱滚子轴承刚度计算模型。研究了圆柱滚子轴承的刚度特性,分析了圆柱滚子轴承的载荷分布和受载变形情况,为发动机轴系有限元分析中边界条件的处理提供了依据。     

圆锥滚子轴承保持架压斜坡模具设计

采用保持架梁压斜坡形式,提高保持架强度,改善与滚动体的接触性能,延长轴承使用寿命,提高轴承质量。     

汽车轮毂用双列圆锥滚子轴承结构设计

通过对比分析国内外汽车轮毂用双列圆锥滚子轴承系列产品的结构特征和参考目前国内（单列）圆锥滚子轴承设计方法,分析并总结了汽车轮毂用双列圆锥滚子轴承结构设计方法及其思路。     

双列圆柱滚子轴承安装对轴承失效的影响

通过对双列锥孔圆柱滚子轴承的失效原因进行分析,解决装机、调试和试车过程中经常出现的因安装使用不当造成轴承早期失效的问题。     

线接触最小油膜厚度计算公式的简化及应用

将繁琐的线接触等温全膜弹流最小油膜厚度计算公式中的各参数,转化成与圆柱滚子轴承密切相关的参数,得出简化的、方便实用的圆柱滚子轴承最小油膜厚度计算公式,并将其应用于生产实践中。