【作者】 陈英俊；

【导师】 黄平；

【作者基本信息】 华南理工大学 ， 机械设计及理论， 2014， 博士

【摘要】 润滑是降低摩擦、减少磨损的主要手段。大概有80%以上的滚动轴承和20%的滑动轴承是脂润滑的。润滑脂的主要作用就是在轴承的摩擦界面间提供一层润滑膜，防止摩擦界面直接接触。因润滑膜变薄或破裂而导致的摩擦系数增大或摩擦磨损，是导致机械零件和设备失效的主要原因。润滑膜的厚度直接反映了脂润滑的润滑性能，所以人们通过各种方法，包括理论计算和实验测试等方法，对油润滑的润滑膜厚度及润滑性能研究。润滑脂有极其复杂的流变性能，表现出强烈的非牛顿流体性质。脂润滑的弹流润滑动压理论的实际工程计算比油润滑要复杂得多。润滑现象常常发生在毫米级的微小区域内，润滑膜的厚度常为微米级甚至纳米级，要对这么微小的区域内的复杂润滑现象进行测试，技术上是相当困难的。本课题的目的就是要在前期研究的基础上，对脂润滑理论及润滑测试技术的某些不足加以改进和完善。本文具体进行了以下几个方面的研究工作：1.研制了脂润滑弹流试验台。对油润滑的弹流试验台的机械传动装置、图像采集装置、供油及加载装置等进行了改造设计，研制出脂润滑弹流试验台，传动稳定性得到了提高，控制更加方便，采集到的图像清晰稳定，静态测量结果与理论计算结果相符合，改造与设计结果符合预期。2.对基于相对光强原理的光干涉膜厚测量法，当光干涉级次超过零级的时候，提出了一个普适的膜厚计算公式，讨论了双光束干涉应用的条件，和基于双光束干涉的真实光强——膜厚干涉曲线改进了相对光强法的测量精度，并讨论了基于数字式高速工业相机和基于交流伺服电机的膜厚动态测量技术；基于动态测量技术确定了光干涉的级次，测量了基础油的润滑膜厚度，基于普适公式计算出完整的膜厚形状。3.提出了一种无需动态标定干涉级次的多波长干涉测量润滑膜膜厚的方法，测量中只需要静态和目标工况稳定运行的的图像，能综合利用不同波长单色光在同一膜厚有不同光强分辨率的特点，提高膜厚测量精度；指出技术的关键是光强——膜厚曲线的标定和拟合。4.比较了实验测量结果与理论计算结果。实验中观察到随着卷吸速度的增大，膜厚是明显增加的，同时最小膜厚处向接触中心移动，这与点接触弹流润滑的理论计算是一致的。对比证明测量方法有较好的测量精度和稳定性，改进之后的相对光强法及动态测量的技术是可行的。将实验结果与Hamrock-Dowson膜厚公式的计算结果对比，也发现变化规律是一致的，低速时的中心膜厚和整个速度范围最小膜厚吻合得很好，说明了Hamrock-Dowson膜厚公式在轻载高速工况时候的应用局限性。对比基础油的三波长光干涉实验结果与动态测量结果，两者有很好的一致性。实验结果证明三波长光干涉法有其独特之处，方法是可行的。5.对轮毂轴承的脂润滑进行了数值分析和实验研究。汽车轮毂轴承的脂润滑因基础粘度大、非牛顿特性强烈、当量接触曲率半径小，其弹性流体动力润滑计算有很大困难。本文把球轴承形式的轮毂轴承接触类型近似线接触来求解，建立了脂润滑弹流润滑的Reynolds方程、膜厚方程及粘压方程等，并对这些方程进行无量纲化和差分数值求解。求得了轮毂轴承脂润滑弹流润滑的数值解，得到了润滑膜的压力分布和膜厚形状。结果表明：轮毂轴承脂润滑弹流润滑膜具有与油润滑类似的二次压力峰和出口膜厚颈缩现象；较小的载荷、较高的速度或较大的流变指数会形成较厚的润滑膜，相应的二次压力峰也更加明显；滚珠与滚道间的润滑状态实际处于弹流润滑和边界润滑交替变换状态。轮毂轴承润滑脂的流变性能实验结果说明它们都有明显的剪切稀化和非牛顿流体性质，而且不同稠化剂的润滑脂有不同的高温润滑性能，这主要归咎于稠化剂纤维在温度变化时不同表现和其对润滑的作用机理。更多还原

【Abstract】 Lubrication is the most popular method to reduce friction and avoid wear. About80%rolling bearings and sliding bearings are lubricated by grease. The proposed grease is mainlyto provide a layer of lubricating film between the friction interfaces of bearing so as to avoiddirect contact from friction interfaces. The friction coefficent becomes higher while thelubricating film becomes thinner or broken, which will evently cause failure of mechnismparts and devices probably. And because the thickness of lubricating film reflects thelubrication performance directly, many people study the film thickness and performance ofgrease lubrication by many means, including the theoretical and experimental methods.However, the rheological properties of grease are extremely complex and grease showsstrong non-newtonian fluid properties. These result in the complexity calculation of greaseelastohydrodynamic lubrication in engineering rather than oil lubrication. Lubricationphenomena often occurr in the millimeter of tiny area and the thickness of the lubricating filmare often micron-scale even nanoscale. Therefore, it is difficult to carry out measurement ofthe complex phenomena of lubrication in such a small area. The main purpose of this researchproject is to improve and perfect some deficiencies in the theory of grease lubrication and itsmeasurement techniques.The detailed work accomplished in this dissertation is as follows.Firstly, a grease EHL tester is developed. By the design and improvement of themechanical transmission, image acquisition device, fuel feeding and loading device, thegrease EHL tester is developed. The transmission stability is improved, the control becomesconvenient, and the captured images are clear and stable. At last, the stationary test resultsshow good consistency with the theoretical results. The design and improvement results meetthe purposed requiement.Secondly, a pervasive formula for relative optical interference intensity technique (ROII)is proposed when the interference order beyonds zero. The conditions which can apply ROIIare discussed. And based on the actual intensity-thickness curve, the measurement accuracyof ROII is improved. Through dynamic measuremnt technique, the interference order can bedetermined. The lubricating film thickness of base oil is measured, and the whole shape offilm thickness is calcalated by the pervasive formula.Thirdly, a measuement method of film thickness called multi-wavelength interferometryis proposed. In this method, it is not necessary to determine the interference order, while theonly requirements are the images which captured in stationary and poposed conditions. This method can utilize the feature that monochromatic light with different wavelengths havedifferent intensity resolution at the same fim thickness, so as to achive higher measurementaccuracy. The key problem of this technique is to the caliberation and fitting ofintensity-thickness curve.Fourthly, the comparision between the film thickness in experiments and theory isaccomplished. In experiments, the film thickness is obvious getting thicker when theentrainment speed becomes higher. At the same time. the position of the minium thickness isgetting closer to the contact center. These phenomna show consistency with theory. Thecomparisions show the measuring methods have good accuray and stability. The improvedROII and dynamic measurent techque is feasible. When comparing experimental results withthose of calculated by Hamrock-Dowson film thickness formula, there are also the samechange rule. Good consistency exists in low speed area for central film thickness and wholespeed area for the minimum film thickness, while application limitations are proved under thelow load and high speed conditions for the Hamrock-Dowson formula. When camparingthose results in three-wavelength interferometry and dynamic measurement, they have goodconsistency. The experimental results show that the three-wavelength interferometry isspecial and feasible.Finally, numerical analysis of grease lubrication under specific conditions is performed.Due to the high initial viscosity, obvious non-Newtonian property and small equivalent radiusin the grease lubrication of automotive wheel hub bearing, great difficulties arise in thecorresponding EHL calculation. By approximating the line contact type of wheel hub bearingin ball bearing form, the Reynolds equation, film thickness equation and viscosity-pressureequation are established and solved dimessionlessly and differential numerically. Finnally thedistribution of pressure and the shape of film thickness are obtained. The results show that1)in greased and lubricated wheel hub bearings, there exist a second pressure peak andthickness necking similar to those under oil lubricated condition;2) light load, high velocityand large rheological exponent all help to form thicker lubricating film with a more obvioussecond pressure peak; and3) the lubrication between the rolling ball and the rolling cave isactually in an alternate state of EHL and boundary lubrication. The experiments aboutrheological properties show obvious shear thinning and non-newtonian fluid properties. What’more, different soaps result in different high tempreture performance, this is because of thedifferent behaviour of soap fibers at high tempture and the lubricating mechanism.更多还原