表面凹坑对点接触脂润滑油膜特性的影响

通过数值计算方法,研究了点接触脂润滑摩擦副表面存在凹坑时油膜厚度和油膜压力的分布规律,并与光滑表面条件下的油膜特性进行了对比。研究结果表明:点接触脂润滑摩擦副表面存在凹坑时,在凹坑边缘位置会出现油膜压力峰,而在凹坑中心周围油膜压力值较低;靠近入口处一侧凹坑边缘位置油膜厚度出现"凹陷"现象,润滑脂流经凹坑时油膜厚度则会"跃升";凹坑引起油膜压力和油膜厚度分布的变化会随着凹坑位置的变化而相应的变化;表面凹坑不利于点接触脂润滑摩擦副的润滑。     

Film-forming Characteristics of Grease in Point Contact under Swaying Motions

The technique of relative optical interference intensity (ROII) and simple numerical calculations were used to investigate the lubricating behavior of grease lubricant films in the rolling direction under swaying motions (acceleration/deceleration). Experimental results indicate that at a same entrainment velocity of the inlet, the central film thickness under deceleration is larger than that under acceleration. The minimum central film thickness in one swaying cycle does not occur at the moment of zero entrainment, but at the initial period of acceleration. At the moment of zero entrainment, the central film is thicker than its peripheries, and the value of the central film thickness increases with increases in the changing rate of the entrainment velocity. It is thought that the transient behaviors of the grease lubricant film deviate from those in steady state conditions. The profiles of the transient film thickness and the approximate thicknesses of elastohydrodynamic contact in the rolling direction calculated by using a simple numerical method are supported by the experimental results. The numerical method can also be used to explain the behavior of the grease lubricating film under non-steady state conditions. An erratum to this article can be found at     

Effects of Slide/Roll Ratio on the Behaviours of Grease Reservoir and Film Thickness of Point Contact

The film formation mechanism of lithium complex grease under starved condition was proposed based on the analysis of the relationship between grease reservoir and the finger-shaped lubricant along the rolling track using a laboratory built ball-on-disc test rig. Film thicknesses with rolling time at different slide/roll ratios were measured and discussed in detail. Experimental results showed that starvation occurred soon after the operation under pure rolling condition. In contrast, the contact remained fully flooded under slide–roll condition. The measurement of grease fingers proved that slide/roll ratio contributed to replenishing the contact by transferring more grease to the vicinity of the contact to form a lager lubricant reservoir. The volume of grease fingers, the inlet lubricant supply and the film thickness at different slide/roll ratios were found to be in good agreement.     

Lubricant Film Thickness and Wear in Rolling Point Contact

Lubricant film thickness in the partial elastohydrodynamic range was measured as a function of rolling speed in a rolling 4-ball configuration, for four mineral oils, two esters and a polyphenylether covering a viscosity range of 8–360 cs. Film thickness is shown to vary with speed as a power function. At the point where a full elastohydrodynamic film is formed, the product of viscosity and speed is constant for most lubricants.

Wear rate w after run-in follows a simple wear law w = Ka where a is the total area of asperity contact and K is a constant characteristic of the lubricant, of the order of 1 μg/inch³ for compounded ester type lubricants rating these as best, and 4 μg/inch³ for ester base stock, 6 μg/inch³ for polyphenylether and 13 μg/inch³ for mineral oil base stock, rating these lubricants progressively poorer in the order given, regarding their wear-preventing ability.

A hypothesis regarding size and shape of wear particles is derived, suggesting platelet shaped particles. Limited data appear to confirm an exponential distribution of wear particle diameters with a mean of the order of 10^?4 inch.     

硼酸盐在聚脲润滑脂中摩擦学性能的研究

使用脂肪胺和芳香胺的混合胺制备聚脲润滑脂,并对稠化剂相同而基础油不同的2种聚脲润滑脂的基本理化性能及微观结构进行对比分析。通过四球摩擦磨损试验机,考察硼酸盐对聚脲润滑脂摩擦学性能的影响,采用SEM与XPS表征在添加硼酸盐极压抗磨剂的聚脲脂润滑下的钢球磨损表面的形貌和化学元素状态,并对其极压抗磨机制进行分析研究。结果表明:硼酸盐能显著提高聚脲润滑脂的极压性能,同时具有良好的抗磨损性能,其中,用合成油制备的聚脲润滑脂的极压抗磨性能优于矿物油制备的聚脲润滑脂。     

基于点接触的凸轮机构润滑油膜分析

将几种常用弹流润滑最小油膜厚度公式进行了比较,并在点接触模型的基础上给出了新的计算方法.对油膜几个重要参数的影响进行了分析,计算了从动件不同运动规律下凸轮机构的最小油膜厚度.结果表明:凸轮的基圆半径和转速对于最小油膜厚度有较大影响,基圆半径越大、转速越高,则油膜越厚,因此设计时应尽量采用较大的基圆半径.     

变速点、线接触副弹流润滑油膜的观测

应用光干涉方法,在自制的光弹流试验机上分别对纯滚动条件下点接触和线接触形成的弹流油膜进行变卷吸速度实验,并进行油膜测量。结果表明,在卷吸速度为零时都有封油现象的出现。随着卷吸速度的增加,油膜厚度增加,点接触形成的弹流油膜具有典型的马蹄形特征,线接触形成的弹流油膜在接触区端部有类似点接触的马蹄形收缩。要达到同样的最大赫兹接触压力,施加在线接触实验上的载荷要比施加在点接触实验上的载荷大40倍左右。     

Grease Lubrication of Ultra-High Speed Rolling Contact Bearings

The failure mechanisms of grease lubricated ball bearings operating in the DN range from 1.0 × 10⁶ to 2.0 × 10⁶ was studied. A new rig capable of controlled operation of 20 and 25 mm ball bearings at speeds up to 100,000 rpm is described. Ball separator design seems to be a very important factor and a lightweight single piece machines outer ring controlled ball separator appeared to give the best results. In general, mechanical factors such as vibration, bearing design, bearing fit and tolerances, dynamic balance, load alignment, etc., have more influence on the performance of the bearings studied than gross grease variables. Under ideal conditions it is indicated that adequate lubrication with grease is possible for periods over 100 hours. However, under the test conditions generally in existence in the ultra high speed rigs grease lubrication was only adequate for very short periods.

Grease compositional factors leading to better performance are smooth texture and hard consistency. At the temperature investigated diester type oil was slightly superior to mineral oil and greatly superior to silicone oil.     

几种金属纳米粒子作润滑脂添加剂的试验研究

用Falex四球摩擦磨损试验机考察了镍、钴、铬、钼、铁-钴及铁-镍合金纳米粒子作为添加剂加入润滑脂的摩擦学行为。结果表明：添加纳米粒子的润滑剂均具有较好的减摩抗磨性能和较高的承载能力(PB值)，合金纳米粒子比金属单体纳米粒子的添加效果好，纳米粒子质量分数在3％左右时润滑脂具有较佳的摩擦学性能。     

表面粗糙对乏油条件下非牛顿点接触热薄膜润滑的影响

假设运动表面为光滑表面,静止表面上有一个垂直于卷吸速度方向的横向划痕,采用Ree-Eying本构关系求解表面单一粗糙对纯滑动点接触热薄膜润滑的影响,分析处于接触区中心的表面划痕在不同的乏油程度下对油膜压力、膜厚及温度的影响。结果表明:在乏油条件下,处于静止表面上接触中心的横向划痕前后的压力和温度都有尖锐的升高,且这种升高幅度随乏油程度的严重而增加;在乏油条件下,表面粗糙的存在更不利于润滑,易于造成润滑失效。     

间歇运动条件下润滑脂膜厚分布的实验研究*

采用光干涉技术在球-盘点接触试验台上进行间歇运动条件下的润滑脂膜厚分布研究,测量卷吸速度和停歇时间影响下的中心膜厚和最小膜厚的变化。使用Centoplex3润滑脂,在充分供脂的情况进行不同停歇时间和不同卷吸速度下的对比实验研究。研究发现,增稠剂纤维团存在于减速阶段末期及停歇阶段和加速阶段前期,对膜厚造成一定程度的波动;随着停歇时间的增加,纤维团聚集程度降低并且尺寸减小,但始终有纤维团存在于接触区;在非停歇阶段的相同瞬时,卷吸速度越大,中心膜厚和最小膜厚就越大,而在停歇阶段的中心膜厚与最小膜厚变化则不遵循此规律;增稠剂纤维团的随机存在会在一定程度上增大中心膜厚与最小膜厚,间歇运动中采用脂润滑方式比油润滑更为有利。     

Microbubble Phenomenon in the Grease Lubricating Film Induced by Micro-Oscillation

A microbubble phenomenon induced by micro-oscillation in the grease lubricating film confined within a nanogap between a highly polished steel ball and a smooth glass disc has been observed with an interferometer. Experimental results show that when the micro-oscillation frequency is a constant value, the microbubble number increases with the micro-oscillation amplitude. When the micro-oscillation amplitude is a constant value, the microbubble number increases with the micro-oscillation frequency when the latter is lower than the critical value and decreases with the micro-oscillation frequency when it is higher than the critical value. Theoretical models and analyses have been used to discuss the bubble formation and describe the characteristics of bubble movement.     

几种金属氧化物纳米粒子作润滑脂添加剂的试验研究

用Falex四球摩擦磨损试验机考察了金红石相与锐钛矿相TiO2、α-Al2O3和γ-Al2O3、钇稳四方相和单斜相ZrO2纳米粒子作为润滑脂添加剂的摩擦学行为。试验结果表明，这些纳米粒子均具有较好的减摩抗磨性能和较高的承载能力(pB值)，其润滑性能与纳米粒子的结构和大小都有一定的关系，而且在添加浓度3％左右时具有最佳的效果。     

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。     

球盘接触脂润滑试验台的运动控制研究

润滑脂有强烈的非牛顿流体性质和触变性,使得其润滑性能测试结果具有不确定性。为了实现润滑脂性能的有效测试,研究球盘接触脂润滑试验台的运动控制方法;设计试验台高旋转精度的主轴结构,研究基于PLC的交流伺服电机的运动控制方法,并基于光干涉原理测量润滑脂的润滑膜厚度。试验表明,该方法能准确控制球盘接触脂润滑试验台的摩擦副运动,实现了所需运动规律;设计试验台能方便准确地测量出润滑脂在不同工况下的润滑膜厚度。     

薄膜涂层摩擦学性能的灰色分析与预测

运用灰色系统理论，采用GM(1，1)直接建模预测法，对离子镀(Ti，Cr)N、TiN、CrN膜层的摩擦学性能进行了分析和预测。结果表明，对膜层摩擦学性能采用灰色理论进行分析与预测，可预测不同影响因素下膜层的摩擦系数和磨损率，其误差较小；能为膜层设计和工程实际使用提供指导依据。     

Film Thickness of Mechanically Worked Lubricating Grease at Very Low Speeds

Several different types of commercially available greases, aged in a roll stability tester, have been tested in a ball-on-disc machine where the film thickness was measured using the interferometry method. The grease film thickness at very low speed is thicker than the base oil film thickness due to the contribution of the thickener in this regime, which practically vanishes at higher speeds. The (mechanical) aging process reduces the thickener material, decreasing the grease film thickness at very low speeds (entrainment speed less than 0.01 m/s) with aging time, whereas no significant difference was found at higher speeds where the grease film thickness still approached the calculated base oil film thickness.     

A Generalized Differential Colorimetric Interferometry Method: Extension to the Film Thickness Measurement of Any Point Contact Geometry

Whereas industrial elastohydrodynamic (EHD) contacts are generally noncircular, most experimental observations are made on sphere-on-plane conjunctions. The circular case is indeed a specific elliptical case, and it was widely investigated. The differential colorimetric interferometry (DCI) technique was often used to perform precise film thickness measurements in circular EHD contacts. From a single picture of the dynamic contact, it enables mapping the film thickness of the full conjunction, and postprocessing can be applied afterwards. Moreover, it is possible to record sequences at relatively high-frequency sampling. However, until now, the method could not be directly applied to noncircular conjunctions. In the present article, a generalized DCI method is proposed and assessed by several static and EHD validation cases for elliptical and torus-on-plane contact geometries. This new method no longer necessitates particular requirements on the contact shape while retaining the advantages of the original DCI method. It allows precise film thickness measurements in realistic industrial EHD contacts and opens the way for new experimental observations.     

点接触齿面取不同坐标系求解过程的研究

本文系统地阐述了点接触齿面啮合理论中求解接触点的完整过程，并导出了在取不同坐标系时求解接触点的同一计算公式。在啮合传动中，根据具体问题选取不同的坐标系，可应用同一计算公式进行啮合分析与计算。