超高速充液旋压时全膜润滑临界条件研究

采用电阻法对超高速充液旋压内螺旋翅片铜管时全膜润滑临界条件进行了研究，利用旋压接触面之间的电阻变化，确定了形成全膜润滑的临界条件，同时对影响全膜润滑油膜形成的因素进行了分析，试验结果表明，全膜润滑油膜形成主要取决于旋压速度和润滑油特性，其中旋压度是影响全膜油滑油膜能滞形成的关键条件，全膜润滑形成对轴向拉力，扭转偏角和表面粗糙度值均有一定的影响，尤其对扭转偏角和表面粗糙度值的影响更大。     

内螺旋翅片铜管充液旋压成形加工的研究

对内螺旋翅片铜管的充液旋压成形加工进行了系统研究，着重分析了充液旋压过程中形成动压油膜的条件和特点，并建立了数学模型。实验结果表明：随着旋速和润滑油粘度的提高，流体动压润滑作用逐渐明显，被加工管的拉拔力减小，且加工后管外表面粗糙度值减小。     

润滑接触摩擦力的往复式实验研究

在往复式试验机上研究实际加工表面球-盘式接触混合润滑摩擦特性,比较采用不同黏度润滑油光滑接触摩擦力的大小。针对表面粗糙度幅值和纹理对摩擦行为的影响进行研究,结果表明,混合润滑时较高黏度润滑油的摩擦力较小;表面粗糙度幅值在混合润滑时对摩擦力影响较大,且随速度增加而增强,边界润滑时影响很小。与纵向纹理相比,横向纹理表面的摩擦力较小且稳定,低速时这种差别更加明显。     

三叉杆滑移式万向联轴器油膜刚度的分析

基于等温线接触弹流润滑理论,在考虑表面粗糙度的同时,建立三叉杆滑移式万向联轴器的油膜刚度计算模型,分析载荷、润滑油卷吸速度及黏度、表面粗糙度波长及幅值对润滑油膜刚度的影响。结果表明：润滑油膜刚度随着载荷及黏度的增大而增大,随着卷吸速度的增大而减小;相比较于载荷和卷吸速度,黏度对油膜刚度的影响相对较小。在远离接触区中心位置,油膜刚度变换幅度较小,在中心位置附近变换幅度最大。随着表面粗糙度波长与幅值的增大,油膜刚度呈非线性变化,且油膜刚度的振荡频率及幅度变小,油膜刚度的最大峰值靠近接触区中心。     

蜗杆传动的弹性流体动力润滑

从弹性流体动力润滑理论和蜗杆传动的特点出发，分析了有关文献对蜗杆传动弹性流体动力润滑条件分析中的不足，指出了滚动速度是建立润滑油膜和油压的重要条件，论证了滑动速度对润滑油膜和油压的形成也有较大影响。采用Dowson公式计算油膜厚度时，为了考虑滑动速度的影响可引入滑动速度系数Ks予以修正。     

硬脂酸界面修饰对油膜润滑影响的试验研究

研究了有限量供油条件下,硬脂酸界面修饰对滑块-玻璃盘面接触条件下油膜润滑的影响。利用面接触润滑油膜测量系统,作者测量了PAO10、甲基硅油基础油以及添加了0.1%硬脂酸的同种基础油产生的润滑油膜厚度随速度的变化曲线,理论计算了连续双侧脊薄油层和离散液滴供油条件下的油膜厚度,并对硬脂酸在盘表面的吸附进行了表征。结果表明,硬脂酸吸附层使润滑轨道表面能降低,其上润滑油发生“反润湿”呈现液滴状分布,该分布能够增高润滑膜厚;硬脂酸吸附使固体表面产生致密膜,表面粗糙度降低;离散油滴经接触区被压塌成为连续油层分布,再次恢复到离散态需要一定时间,这与固体表面吸附层密切相关;此外,二甲基硅油能够促进硬脂酸吸附,增大玻璃盘基体改性程度和润滑油膜厚度。     

粗糙度各向异性对润滑接触面摩擦的影响

齿轮、轴承、凸轮等重载接触副的性能受表面粗糙度的显著影响。高负载情况下的摩擦因数与润滑接触面粗糙度的各向异性相关。测量的表面粗糙度可以分解为一系列具有不同波长、幅值的正弦表面粗糙度,因此,考虑各向异性正弦表面粗糙度,构建粗糙表面点接触瞬态弹性流体动力润滑(TEHL)模型,提出基于多重网格算法的粗网格构造新方法,提高粗糙表面润滑问题求解的稳健性。研究表面粗糙度各向异性对高负载情况下摩擦因数的影响规律。结果表明,粗糙度的各向异性影响接触面压力、油膜厚度分布、粗糙度形变量,从而影响摩擦因数。提出一个组合函数来量化粗糙度各向异性对摩擦因数的影响,表明全膜润滑到混合润滑的过渡不仅与载荷、速度等工况参数相关,还与粗糙度各向异性相关。     

表面速度异向下的点接触润滑油膜试验机研制及膜厚测量

弹流润滑领域中,润滑油膜的形态、厚度、摩擦力是研究接触区润滑状态,探究润滑机制极为重要的信息。研制表面速度异向下的点接触润滑油膜试验机,该试验机以多光束干涉法作为测量手段,结合弧形轨道实现接触副表面速度夹角的变化;使用旋转系统将接触副系统摩擦力转变为压力,利用高精度压力传感器及摩擦力合力公式,实现表面速度异向下的点接触摩擦力测量和计算。在限量供油条件下对表面速度异向的点接触润滑油膜形态与膜厚进行了观测,探究速度夹角对乏油状态改善及油膜形态变化的影响。结果表明：改变接触副表面速度方向,入口油池得到改善,中心膜厚增加。     

滑动速度对油润滑表面胶合磨损的影响

在油润滑条件下,钢对钢摩擦副的胶合摩损不仅取决于润滑油膜是否破裂,而且取决于在摩擦表面上化学反应膜的形成情况。本文研究了在油润滑条件下滑动速度对钢摩擦副胶合的影响。在低滑动速度下摩擦表面易于形成反应膜,油膜破裂后并不直接发生胶合。胶合发生在高温、高摩擦系数的恶劣条件下。在高滑动速度下油膜破裂后很容易发生胶合,发生胶合前的表面温度和摩擦系数都比较低。     

考虑热弹性变形和表面粗糙度的圆柱滚子轴承热弹流润滑分析

运用线接触热弹性流体动压润滑理论,考虑了润滑油膜温升变化引起的圆柱滚子轴承中滚子和内圈接触表面的径向热弹性变形和表面粗糙度的影响,提出了一种计入热弹性变形和粗糙度影响的圆柱滚子轴承线接触热弹性流体动压润滑分析方法。该方法通过将热弹性变形进行热力转换,得到了滚子和内圈接触表面的材料线热膨胀系数,计算修正了滚子和轴承内圈因油膜温度场变化引起的径向热弹性变形,求得了计入热弹性变形和表面粗糙度后的油膜压力、油膜厚度、油膜温升以及径向热弹性变形量等主要润滑特性,研究了载荷、卷吸速度和滑滚比的变化对最小油膜厚度、最大油膜压力和最大油膜温升的影响规律,结果表明,热弹性变形量与最小油膜厚度处在同一量级,热弹性变形和粗糙度会对润滑特性产生明显的影响。     

润滑状态及其转化过程的测试方法

通过对多种润滑状态测试方法的比较研究，提出了用R－C阻容振荡法来监测滚动轴承的润滑状态。将电容法与电阻法的优点结合起来，且阻容振荡法能实现对全膜润滑，混合润滑与边界润滑状态及其转化过程的监测，并通过实验对滚动轴承的润滑状态及其转化进行了测试研究。     

自旋对弹流油膜影响的试验研究

利用自制的旋滑式光干涉弹流薄膜测量系统,对带有自旋的钢球—玻璃盘接触副形成的弹流油膜形状和厚度进行试验研究。采用新的方法来获得自旋,即通过调节接触副与玻璃盘旋转中心的距离改变自旋分量的大小。试验结果表明,自旋导致油膜厚度降低,油膜形状也失去了经典的马蹄形相对卷吸中心线的对称性。当卷吸速度增加时,油膜厚度增加,油膜形状的非对称性增强;载荷增加,油膜厚度减小,油膜形状的非对称性增强;偏心距增加,油膜整体厚度增加,两侧油膜厚度差别减小,油膜形状的对称程度增加。     

椭圆接触纯自旋问题的弹流润滑数值分析

研究了椭圆接触纯自旋问题的等温弹流润滑,用多重网格法求得了完全数值解,研究了速度、载荷、椭圆比和计算区域对压力和膜厚的影响。结果表明,在轻载、高速、大椭圆比条件下,椭圆接触的纯自旋运动可产生润滑膜,油膜的形状和压力分布都和经典弹流润滑截然不同;椭球的自旋速度、载荷、椭圆比以及承载域的大小都对压力和膜厚有很大的影响。     

Influence of spinning on the rolling EHL films

Spinning cannot be ignored in some elastohydrodynamically lubricated contacts. In this paper, spinning is incorporated into an elastohydrodynamic lubrication (EHL) contact of pure rolling and its influences on EHL films are studied. Results show that with increase in spinning, the symmetry of the film shape gets lost, and the minimum film thicknesses, located respectively at the two side-lobes, decrease and show more dependence on loads. The speed indices of the film thickness at the side lobes are higher than those of the classical EHL theory predicted. Numerical work has also been carried out to clarify the experiment measurements.     

Boundary lubrication with anti-wear additives: study of interface film formation by electrical contact resistance

It has been shown that a rapid measuring technique for electrical contact resistance (ecr) has potential applications in lubricant additives studies. In boundary lubrication of a metallic interface with zinc dialkyl dithiophosphate (DTPZn) or other anti-wear additives blended in the lubricant, anti-wear efficiency relies on interface film formation which acts also as an insulating barrier for electrical current. Investigations in the 1ω to 10 Mω range of resistance, with subsequent and appropriate ecr signal treatment and analysis, indicate that systematic use of ecr permits visualisation and study of interface film formation. This paper shows that two interface films can be detected, with two different levels of average ecr, 0–1 kω and 100k–10Mω. Discussion is based on an interface model and attempts to find what kind of further information on film formation may be obtained from ecr measurements     

Estimation of lubricant interlayer shear strength under conditions of imperfect boundary lubrication

This paper considers the use of contact electrical conductivity for investigations into molecular tribology. The shear strength of thin lubricant films has been studied at nominal point contact between two crossed cylindrical steel probes. The interface was simultaneously monitored using electrical contact resistance. It is shown that the binomial law of friction holds for the sliding path portions where electrical measurements point to a continuous lubricant film. The experimental data can be used to evaluate the molecular friction parameters. An algorithm and software with which to evaluate shear strength and its components under conditions of imperfect boundary lubrication have been formulated.     

纳米级润滑膜的粘度修正与薄膜润滑计算

根据纳米级润滑膜的试验测试结果提出薄膜润滑状态的粘度修正公式 ,并在此基础上建立了润滑膜厚度计算的数值计算方程。将该数值计算结果与弹流理论计算值和试验值进行对比表明 ,在薄膜润滑条件下 ,膜厚与速度和润滑油粘度的关系与弹流润滑计算结果相差较大 ,可明显看出弹流润滑向薄膜润滑的过渡 ,所提出的粘度修正式与试验结果则有较好的一致性     

Electrical Sliding Friction Lubricated with Ionic Liquids

Lubrication is one of the most important methods for maintaining and improving the reliability of electric contact components. In view of the conductivity, the lubrication performances of ionic liquids under electric contact have been investigated by using a reciprocating sliding tribometer. Compared with dry friction condition, ionic liquids present an excellent lubrication property. Meanwhile, under the low-load condition, the contact resistance as well as electrical power consumption decreased obviously when lubricated with ionic liquids. And the stronger current strength it is, the higher coefficient and lower contact resistance it shows. The reason could be ascribed to the current-induced fracture of the ion-adsorbed film, especially those in the asperities. And the transformation of the direct contacts, in turn, affects the friction coefficient and contact resistance.     

Asymptotic analysis of a lubricated heavily loaded spinning and rolling ball in a parabolic raceway

In the paper, the previously developed asymptotic approach to solution of the steady isothermal problem of elastohydrodynamic lubrication (EHL) for heavily loaded point contacts is applied to a lubricated point contact with rolling and spinning. It is shown that the whole contact region can be subdivided into three subregions. The central region can be subdivided into the Hertzian region and two adjacent boundary layers — the inlet and exit zones. The main results of the paper are threefold: (i) it is shown that in the central parts of the inlet and exit zones, the mechanisms and the equations controlling the behaviour of the lubrication contact parameters in heavily loaded point and line EHL contacts are identical, (ii) asymptotically precise formulas for the central and exit lubrication film thickness for pre‐critical and over‐critical starved and fully flooded lubrication regimes are analytically derived, and (iii) the inlet and exit zone asymptotically valid equations are uniform across all steady heavily loaded line and point EHL contacts for lubricants with the same rheology. These asymptotically valid equations were analysed and numerically solved in previously published work based on the stable methods utilising the specific regularisation approach developed for lubricated line contacts. Cases of pre‐critical and over‐critical lubrication regimes are considered. The formulas for the lubrication film thickness for pre‐critical and over‐critical starved and fully flooded lubrication regimes allow for simple analysis of the film thickness as a function of spinning angular speed, angle of the entrained lubricant and other pertinent contact characteristics. Copyright © 2013 John Wiley & Sons, Ltd.