冲击载荷条件下线接触往复运动的弹流润滑特性

考虑到在工程实际中机械要素常受到冲击载荷的作用,研究在稳态加载、正弦波加载及三角波加载条件下线接触往复运动工况的热弹性流体动力润滑特性,并探讨在正弦波加载方式下,不同的冲程长度对热弹性流体动力润滑特性的影响。结果表明:冲击加载条件对油膜的压力、膜厚、温度都有较大的影响,随着载荷的增加,油膜中压力增大,膜厚降低,温度升高;在相同的加载方式下,冲程长度越长,一个周期相同瞬时的卷吸速度就越大,因此油膜厚度越厚,温升也越明显,而摩擦因数则明显降低。     

基于齿形链销轴-链板接触副的热混合润滑分析

为研究齿形链销轴-链板副的混合润滑性能,分析齿形链中销轴-链板接触副的几何关系及其运动特性,基于平均流量模型,建立销轴-链板副的热混合润滑模型,讨论综合曲率半径、表面粗糙度及载荷对非牛顿热混合润滑的影响。结果表明：随着综合曲率半径的增加,膜厚比增加,润滑状态由混合润滑转变为全膜润滑状态,油膜压力增加,粗糙峰接触压力减小,摩擦因数与摩擦热均降低,有效地提升了销轴-链板副的润滑性能;由于销轴与链板孔径尺寸偏差的存在,导致综合曲率半径在一定范围内变化,故其对销轴-链板接触副润滑性能的影响是变化的;随着表面粗糙度或载荷的增加,膜厚比减小,摩擦热升高,润滑状态由全膜润滑转变为混合润滑,增加了销轴-链板副的磨损风险。     

往复运动条件下润滑油膜特性的实验观察

采用多光束干涉技术观察往复运动条件下润滑油膜的滑移及黏弹特性,研究振幅和频率对往复动态润滑弹流油膜的影响。结果表明:往复运动过程中,在特定时刻气穴的出现使油膜厚度逐渐减小,削弱了滑移程度;因润滑油的黏弹性而引起的运动滞后导致了油膜的非对称性;频率增大时,正行程末端时膜厚明显增大,油膜输送速度也随着增大;而负行程末端油膜受气穴的影响膜厚增大较慢;振幅(输入位移)增大时,正行程末端时油膜整体平移,而负行程末端入口凹陷呈现先变明显而后消失的现象。     

计入薄壁构件挠度变形的线接触弹流润滑分析

由于薄壁构件在受力情况下产生挠度变形,对弹流润滑有一定影响,导致原来的弹流润滑计算存在较大误差,经典的接触模型已不再适用。提出一种考虑薄壁平板挠度变形的弹流润滑线接触模型,该模型能够确切反映薄壁平板的挠度变形对弹流润滑的影响;采用有限元仿真软件建立薄壁平板的挠度变形模型,在挠度变形的基础上,分析速度参数及载荷参数对线接触弹流润滑性能的影响。研究结果表明:挠度变形对薄壁件润滑的影响十分明显,油膜压力减小,中心膜厚分布范围增大,膜厚值减小;随着速度及载荷参数发生变化,油膜压力及膜厚也相应地发生改变;当其他条件不变时,中心油膜厚度随速度的增加而增大,且中心油膜区域逐渐增加,速度参数对油膜压力影响较大,油膜压力随着速度的增加而升高,颈缩现象逐渐出现;油膜压力随着载荷的增大而升高,同时油膜厚度逐渐减小。     

周期性载荷作用下的滚珠丝杠相邻滚珠间热弹流数值计算

滚珠丝杠相邻滚珠之间存在零卷吸速度接触,与常见的纯滚动或滚滑接触相比工况更恶劣,周期性载荷作用下相邻滚珠之间的接触则更为复杂。建立零卷吸工况下正弦波载荷作用的滚珠丝杠相邻滚珠间热弹流数值计算模型,采用多重网格法求解压力,多重网格积分法求解弹性变形,逐列扫描技术求解温度场,实现对线接触热弹流润滑的数值模拟。并以R100-25Y2型滚珠丝杠为研究对象,分析其油膜特性以及载荷幅值和表面波纹度对油膜特性的影响,结果表明：在加载过程中,由于挤压效应增强,“温度-黏度楔”效应增强,油膜凹陷深度及中心膜厚增大,最小膜厚减小,接触区最大温升增大,摩擦系数减小,卸载过程则相反;由于载荷变化的时变效应,油膜变化相比载荷变化存在一定的滞后性,而载荷波动幅值的增大进一步增强了该滞后性;表面波纹度的存在造成油膜压力和膜厚曲线的波动,特定的波纹度长度可导致中心膜厚和最大温升增大,而最小膜厚和摩擦系数减小。     

表面波纹度对工业链套筒-销轴铰链副热弹流润滑的影响

运用弹流润滑理论,针对工业链中套筒和销轴之间的接触,采用无限长线接触热弹流模型研究表面波纹度对不同型号链条接触区的油膜厚度、压力及温度的影响。结果表明:表面波纹度会引起油膜压力、膜厚和温升的显著波动;对于小的当量曲率半径,膜厚波动的振幅同表面波纹度的差距很大,接近100%,但是随着当量曲率半径的不断增大,膜厚波动的振幅逐渐降低,最后表面波纹度已不发生弹性变形;膜厚的波纹度振幅变化还与波纹度的波长有关,波长越长,波纹度振幅变化的速度越慢;在某些特定接触条件下,波纹度表面可以形成比光滑表面更厚的油膜。     

限制空间中的弹性流体动压润滑

在经典的弹性流体动力润滑理论分析中,油膜压力的计算要满足载荷平衡条件,而这一条件并不适用于发生在限制空间中的弹流润滑,当弹流润滑发生在限制间隙中,油膜的承载力会随工作参数的变化而变化。对限制间隙条件下等温线接触弹流润滑问题进行数值分析,研究油膜厚度及压力的变化规律。结果表明:在限制间隙等温线接触弹流润滑条件下,油膜厚度及压力随速度参数以及材料参数的增加而增加,而限制间隙增加时,膜厚增加,压力减小。根据数值分析结果,拟合出限制间隙条件下的膜厚计算公式,该公式有较小的计算误差。     

摆线针轮传动接触乏油润滑特性分析

摆线针轮行星传动啮合过程中供油量变化影响传动效率和接触疲劳特性。引入部分油膜厚度比例,以入口油膜厚度来表征乏油程度,建立摆线针轮有限长线接触乏油润滑数值模型,研究在齿宽方向上入口油膜厚度不均匀分布对压力和膜厚分布的影响。结果表明:乏油条件下,随着入口供油量增加,入口油膜厚度的不均匀分布对齿宽方向上的压力和膜厚分布的影响减小;随着速度的增加,齿宽方向压力和膜厚分布受入口油膜厚度不均匀分布的影响增加;随着载荷的增加,齿宽方向压力和膜厚分布受入口油膜厚度不均匀分布的影响程度减小。     

限制空间中的弹性流体动压润滑分析

在经典的弹性流体动力润滑理论分析中,油膜压力的计算要满足载荷平衡条件,而这一条件并不适用于发生在限制空间中的弹流润滑,当弹流润滑发生在限制间隙中,油膜的承载力会随工作参数的变化而变化。对限制间隙条件下等温线接触弹流润滑问题进行数值分析,研究油膜厚度及压力的变化规律。结果表明:在限制间隙等温线接触弹流润滑条件下,油膜厚度及压力随速度参数以及材料参数的增加而增加,而限制间隙增加时,膜厚增加,压力减小。根据数值分析结果,拟合出限制间隙条件下的膜厚计算公式,该公式有较小的计算误差。     

基于套圈变形的柔性轴承弹流润滑分析

以柔性轴承为研究对象,基于赫兹接触理论和弹性薄壁圆环理论,建立柔性轴承等温椭圆点接触弹流润滑模型,对滚珠及内外圈滚道的接触区受载荷最大位置处进行弹流润滑数值分析;计算危险点的曲率半径、速度及载荷,分析载荷及速度变化对该位置润滑性能的影响。研究结果表明:套圈变形使得润滑接触区峰值压力增大、膜厚减小;柔性轴承弹流润滑油膜最小膜厚及中心膜厚均随载荷的增大而减小,油膜压力随载荷的增大而变大,表明载荷增大对柔性轴承的承载有一定影响;随转速的增大最小膜厚及中心膜厚均增大,表明在一定范围内,适当提高转速能够改善润滑性能。     

Numerical analysis of TEHL line contact problem under reciprocating motion

This paper presents a full numerical analysis to simulate the thermal elastohydrodynamic lubrication (TEHL) of steel–steel line contact problem under reciprocating motion. The equation system is solved using multigrid techniques. General tribological behaviors of TEHL under reciprocating motion are explained. Comparison between thermal and isothermal results reveals the importance of thermal effect in prediction of the traction coefficient and film thickness. The influences of frequency, stroke length, and applied load on the variations of film thickness, pressure and traction coefficient during one working cycle are discussed. Furthermore, the influence of slide–roll ratio on tribo-characteristics of oil film under same entraining velocity is revealed.     

Pure rolling elastohydrodynamic lubrication of short stroke reciprocating motion

The behavior of point contact elastohydrodynamic lubrication (EHL) films under pure rolling short stroke reciprocating motion is investigated using both optical interferometry technique and theoretical analysis. The EHL films are recorded with a high-speed color camera and simulated with multigrid techniques. General variation of oil film under point contact reciprocating motion is explained by a comparison between a fully flooded simulation and an experiment with a frequency of 7.78 Hz. Influence of starvation is considered by another simulation under a higher working frequency of 14.4 Hz and the simulated results are compared with experimental results. Both simulations show good agreements quantitatively with experiments. In addition, general tribo-characteristics of EHL under fully flooded and starved conditions are discussed.     

自旋对角接触球轴承弹流润滑与油膜刚度的影响

根据角接触球轴承自旋运动特征，同时考虑弹流润滑效应，建立角接触球轴承考虑自旋运动的弹流润滑模型；采用多重网格法求解弹性变形，利用有限差分法迭代求解雷诺方程，得到较为精确的数值解；分析不同赫兹接触压力、滚道表面粗糙度下自旋对角接触球轴承弹流润滑和油膜刚度的影响。结果表明：考虑自旋时随着Hertz接触压力、自旋角速度增大，油膜厚度减小，油膜压力增大，油膜承压区域呈细长状，并向接触中心靠近；随着滚道表面粗糙度幅值增大，油膜压力和膜厚均出现了波动，且考虑自旋运动时，轴承油膜厚度明显减小，油膜局部压力峰值更大；随着卷吸速度、润滑油黏度增大，油膜刚度减小，而考虑自旋运动时油膜刚度值更大；随着自旋角速度增大，油膜刚度逐渐增大。     

零卷吸往复运动下的弹流润滑实验研究

使用常规球-盘光干涉试验机,研究零卷吸往复运动中油膜的变化情况。实验采用伺服电机驱动钢球与蓝宝石盘,以三角波的形式进行往复运动,两者速度相同但是方向相反。实验过程中采用光干涉技术测量球-盘之间的膜厚,实验后使用双光干涉法测量接触区中截面油膜厚度。实验发现,往复条件下的油膜凹陷小于对应的稳态油膜凹陷,而且接触区发生了速度滑移,导致所产生的油膜凹陷形状和位置区别于零卷吸凹陷;乏油的发生导致接触区中出现大面积的干接触和混合润滑接触。     

EHL under cyclic squeeze motion

A time-dependent EHL problem of a ball impacting a plate by a cyclic approach–separation motion has been solved. Previous experimental findings by some of the authors have been numerically confirmed, i.e., the nearly constant central film thickness during the load-sustaining stage, and the linear relationship between this constant film thickness and the frequency in a log–log scale. The numerical results show a constriction in the trace of central film thickness versus time. Similar to the experiments, numerical results give a dimple film shape, which is caused by the high pressure induced within the contact region. However, the present Newtonian model overestimates the central film thickness and the squeezing contact forces. The influences of the frequency, the static contact load, the amplitude and the pressure–viscosity coefficient on the film thickness and the film pressure have also been investigated.     

旋滑条件下弹流润滑数值分析

建立旋滑条件下椭圆接触弹流润滑的数学模型,用多重网格法求得该条件下的完全数值解,研究速度、载荷、偏心距和椭圆比对油膜厚度、形状和压力的影响。结果表明,偏心距较小时,油膜厚度和形状都与普通弹流有明显的不同;速度、载荷和椭圆比增加及偏心距减小,均会导致接触区两侧最小膜厚的差值增大,油膜形状的非对称性增强;速度、椭圆比增加,油膜厚度增加,接触区压力减小,载荷增加或偏心距减小,油膜厚度减小,接触区压力增加。     

Effects of surface forces on pure squeeze thin film EHL motion of circular contacts

The pure squeeze thin film elastohydrodynamic lubrication (thin film EHL) motion of circular contacts with effects of surface forces taken into account is explored under constant load conditions. The difference between thin film EHL model and EHL model is apparent as the film thickness is thinner than 5 nm. The oscillation phenomena in pressure and film thickness come mainly from the action of solvation forces. The effects of surface forces become significant as the film thickness becomes thinner. Moreover, the viscosity is oscillatory due to its dependency on the hydrodynamic pressure which is affected by surface forces.     

The Prediction of Contact Pressure–Induced Film Thickness Decay in Starved Lubricated Rolling Bearings

Under starved conditions the thickness and distribution of the lubricant film in an elastohydrodynamically lubricated (EHL) contact is directly related to the distribution of lubricant on the track in the inlet to the contact. In starved lubricated rolling bearings this lubricant distribution is determined by many effects. The authors have developed a model to predict the oil lost from the track induced by EHL pressure with no replenishment. A complete bearing is modeled with multiple rolling element EHL contacts and with the applied load to the rolling elements varying along the circumference of the bearing. Results of the oil layer thickness on the track are presented for a ball bearing and a spherical roller bearing for different bearing loads and rotational speeds. The predicted layer thickness decay rate for a ball bearing is significantly larger than for a spherical roller bearing and the predicted effect of the bearing load on the decay rate is small compared to the effect of the rotational speed. The predicted decay periods due to the contact pressure effect are small compared to the observed (grease) life of bearings. The results show that a bearing cannot sustain an adequate layer of oil on the running track unless significant replenishment takes place.     

离心脱开型超越离合器弹流润滑分析

离心脱开型超越离合器是航空传动系统中的重要部件,具有低速楔合传动、高速离心脱开的特性,使离合器在不同工作模式下接触载荷与转速呈不同的关系,因此需针对不同工况下离心脱开型超越离合器弹流润滑性能进行分析.建立离心脱开型超越离合器弹流润滑模型,采用多重网格分析方法进行数值求解,分析进油温度与速度对超越离合器弹流润滑性能的影响...     

表面凹槽对滚子链套筒-销轴摩擦副热弹流润滑影响的数值模拟

以工业滚子链为工程背景,研究表面沟槽对套筒-销轴铰链副在充分供油条件下的热弹流润滑问题的影响。分析基于长椭圆接触假设,建立稳态热弹流润滑的数学模型,采用纵向和横向2种凹槽的表面织构形式。结果表明:在椭圆接触区长轴两端布置2个对称的纵向凹槽时,可以起到储油的作用,增加局部油膜厚度;在椭圆接触区长轴两端各布置3个对称的横向凹槽时,会引起油膜厚度、压力与温度的急剧变化,增加了动压效应。在接触区端部设置横向凹槽的效果要好于设置纵向凹槽。