A Master Curve for the Shear Degradation of Lubricating Greases with a Fibrous Structure

In this article, the mechanical aging behavior of lubricating greases with a fibrous structure is studied by aging fresh samples at controlled shear rates and temperatures in an in-house-made Couette aging machine. The rheological properties of fresh and aged samples were evaluated in a plate–plate rheometer. In the absence of oxygen, no chemical reactions occurred. The results showed that shear degradation is accelerated by increasing the temperature. This thermal effect can be described by an Arrhenius law. A grease aging master curve was created to describe the influence of shear and temperature on the mechanical aging of fibrous structured grease. Next, the model was validated using a conventional grease worker test. Finally, the model was applied to full ball bearings using an R0F?+?bearing test rig. The master curve forms an important contribution to the development of grease life models.     

The Impact of Water on the Yield Stress and Startup Torque of Lubricating Greases

Water is one of the most common contaminants in grease lubrication. There are numerous applications where bearings are susceptible to water ingresses such as in the steel, food, and pulp and paper industries. A grease can absorb water to different degrees depending upon the type of grease. The ability of a grease to either absorb or reject water can influence the service life of rolling bearings. Two parameters that determine the performance of a grease at very low temperature are the yield stress and startup torque. Water was found to influence the yield stress and startup torque depending on the operating temperature, grease type, and percentage water in the grease.     

Film Forming Behavior of Greases Under Starved and Fully Flooded EHL Conditions

Improving knowledge on the film forming behavior of greases is essential to be able to develop efficient greases. This article examines how operating conditions (e.g., temperature, lubrication condition [fully flooded/starved]) and base oil viscosity influence the film forming properties of greases by comparing the behavior of two lithium-based greases and their respective base oils in rolling point contact. It is found that the onset and degree of starvation is controlled by speed (u) × viscosity (ν)/load (W) factor (uν/W) and temperature and that low uν/W values promote entrainment of thickener into contact. Thus, grease with low base oil viscosity shows significant thickener entrainment in the low speed region compared to the one with high base oil viscosity, which leads to the formation of thickener-rich viscous material during extended running with the low base oil viscosity grease. The results suggest that the shape of the film thickness versus speed curve is viscosity and uν/W range dependent. Furthermore, for the test conditions used in this study, grease-lubricated contacts appear to shift from the initial fully flooded condition to starved condition over a prolonged running of 2 h. The results from this study concur with those reported in the literature that fully flooded oil elastohydrodynamic lubrication (EHL) theory or film thickness cannot be directly applied or taken as a guideline in grease-lubricated contacts.     

The Microstructure of Calcium Sulfonate Complex Lubricating Grease and Its Change in the Presence of Water

ABSTRACT

Calcium sulfonate complex grease is often selected for rolling bearing lubrication if there is a risk for water ingress, because it is reported throughout literature that it can absorb large quantities of water. In this article, atomic force microscopy (AFM) measurements have been performed on a commercially available grease with and without water to investigate the microstructural change under the influence of water. From the results it is clear that the formation of large (inverted) micelles, which can be up to a few micrometers in diameter, is the main mechanism responsible for the absorption water. These results can be used to explain the earlier reported effect of water on the rheological and lubricating properties of these grease types. It is shown here that the size distribution of the micelle structure is a function of the amount of water mixed into the bulk grease.     

The Effect of the Electric Double Layer on a Very Thin Water Lubricating Film

This paper discusses the effect of the electric double layer on a very thin water lubricating film with and without consideration of the elastic deformation of the opposing surfaces. A modified Reynolds equation that considers the electric double layer is used in a numerical analysis. The effect of zeta potential on the film thickness and pressure is numerically calculated. For both hydrodynamic and elastohydrodynamic cases, the electric double layer significantly increases the lubricating film thickness. The pressure is also marginally increased, as illustrated in the hydrodynamic analysis. However, the effect on pressure is almost unnoticeable in the elastohydrodynamic analysis. Overall, the electric-double-layer effect is only significant for a water-film thickness of less than approximately 100 nanometers.     

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.     

In Situ Tribological Evaluation of Greases and Solid Lubricants in a Simulated Atomic Oxygen Environment

Four greases and nine solid lubricants have been applied lo 440C steel surfaces and subjected to in situ tribo-testing in a simulaled-atomic-oxygen (SAO) environment. The test apparatus, procedures and results are described. The discussion addresses the calibration of the SAO tribometer using Kapton H film, the effect of SAO on wear and friction characteristics of unlubricaied 440C steel, and the screening test results for all the lubricants wider SAO conditions. Endurance test results of selected greases and solid lubricants, such as a PEPE-type grease and MoS₂ coatings, are also presented. The results of this research should facilitate selection of effective solid lubricants and greases and hence lead to improved lifetimes for mechanisms that must, operate in the atomic-oxygen environment of low-Earth orbits.     

影响血液润滑性能的主要因素分析

血液润滑人工器官具有其它润滑剂不可比拟的优越性,但由于血液的特殊性,其润滑性能受到诸多因素的影响,对影响血液润滑性能的主要因素进行了分析探讨。指出血液的组分变化、剪切率、血细胞的聚集、变形、温度等因素的改变会引起血液粘度的变化,影响血液的流动性,进而影响到血液的润滑性能;摩擦界面的材料表面特性会影响到吸附膜的组成,从而影响到血液润滑状态。     

Experimental Study of Lubricating Grease Flow inside the Gap of a Labyrinth Seal Using Microparticle Image Velocimetry

In this study, the flow of lubricating greases in a labyrinth seal geometry is studied using microparticle image velocimetry (µPIV). The aim is to evaluate the grease velocity distribution inside the gap of a labyrinth seal and to find a relationship between the grease consistency and the transferred speed from the rotating ring in order to choose the correct grease as a sealing medium. In addition, the grease flow characteristics are important for the understanding of fracture due to grease layer displacement. For these purposes, four greases with different rheological properties were used in µPIV experiments. It was found that the grease consistency plays a crucial role in speed development as well as the grease composition and presence of a slip effect at the grease–rotating wall interface.     

润滑脂后处理脱气工艺及设备研究

本文阐述了润滑脂产品脱气的必要性与合理性,介绍了真空薄膜脱气的设备、工艺流程、脱气效果和影响脱气效果的主要因素.     

高碱值磺酸钙对润滑脂性能的影响

高碱值磺酸盐是生产复合磺酸钙基润滑脂的重要原料,其质量是决定复合磺酸钙基润滑脂产品品质的关键因素之一.为选择合适的高碱值磺酸盐,考察不同高碱值磺酸盐从无定型碳酸钙转化为方解石型碳酸钙的转相时间、稠化能力,以及不同高碱值磺酸盐制备的润滑脂的滴点、锥入度、钢网分油和滚筒安定性能;筛选出的高碱值磺酸盐制备的复合磺酸钙基润滑脂...     

滚动轴承中润滑脂流失量的分析与实验研究

滚动轴承中润滑脂的流失是影响其工作性能的关键性问题之一,本文在流变理论的基础上,给出了滚动轴承中润滑脂流失量计算式,并介绍了脂流失实验的结果,分析了影响流失量的主要因素,为润滑脂的选用提供了理论依据。     

磷酸酯离子液体润滑脂的摩擦学性能研究

用腐蚀性较低、简单易合成的磷酸酯离子液体为基础油,聚四氟乙烯微粉为稠化剂制备一种新型的离子液体润滑脂,在Optimol SRV摩擦试验机上考察其对钢/钢摩擦副的摩擦学性能。结果表明,磷酸酯离子液体润滑脂在室温和高温(100℃)下都表现出优异的减摩抗磨性,并且其减摩抗磨性与离子液体阳离子和阴离子的烷基链长密切相关。磨斑表面扫描电镜和XPS的分析结果表明:摩擦表面既存在离子液体润滑脂与摩擦表面发生摩擦化学反应生成的含有Fe F2、Fe PO4和氮的氧化物的化学反应膜,又存在稠化剂聚四氟乙烯的物理吸附膜。     

轴瓦的力学性能对水润滑塑料轴承润滑性能的影响

在线接触热弹流润滑的基础上,对水润滑塑料轴承的热弹流模型进行计算,研究轴瓦的力学性能对水润滑塑料轴承润滑性能的影响,分析不同弹性模量下的压力、膜厚、最高温升曲线和温度分布。结果表明:在载荷等满足要求时,应选择弹性模量小的材料;载荷很大时,应选择弹性模量大的材料;弹性模量很大的材料,材料改性重点是增加自润滑性能和增加热传导系数。     

莲湖坝水电站水导轴承润滑系统的改造

介绍了莲湖坝水电站水导轴承润滑系统存在的问题及改造思路和方法,改造后从根本上解决了机组水导轴承油润滑渗水及轴承温升问题,效果良好。     

脂润滑斜置滚子滑动离合器力矩与温升实验研究

在脂润滑条件下对斜置滚子滑动离合器进行了系统的实验研究,获得了有关该滑动离合器的力矩与温升等基本性能的实验结果,明确了其与轴向力、转速和几何设计参数之间的关系,并研究了此元件在不同转速和轴向力下工作时的力矩波动性,为在脂润滑条件下使用该滑动离合器奠定了基础。     

Influence of grease composition on rolling contact wear: Experimental study

This paper presents an experimental study on the influence of grease composition on rolling contact wear (RCW). Experimental tests for three greases and correspondent base oils were carried out on a twin-disc machine under pure rolling conditions. The following parameters were varied: base-oil viscosity, percentage of soap concentration and the presence of additives. The second aim of these tests is to analyse the use of artificial dents as a technique to evaluate RCW: prior to the tests, artificial dents were printed on one of the contacting surfaces. These dents were used to calculate the wear volume that is removed from the surfaces, based on the assumption that when the material is removed, the diameter of these dents diminishes. For each stop, images obtained using video-microscopy were analysed and the diameter of the dents, at a given number of cycles, was calculated. It was found that tests with different lubricants resulted in different damaged areas around the dents. Based on this, a comparison of this area growth throughout the fatigue cycles was used as a way to compare the influence of grease composition on RCW.     

润滑脂的溶解及铁谱分析试验研究

针对润滑脂由于流动性差而无法直接采用铁谱技术进行磨粒分析的问题,探讨适合溶解不同润滑脂的有机溶剂。选择锂基、钙基和铝基3种目前设备润滑常用的润滑脂,通过水浴加热与超声波震荡的溶解方法,对比研究8种有机溶剂对润滑脂的溶解效果;通过摩擦试验制备带有磨粒的润滑脂试样,通过旋转式铁谱仪进行制谱试验,并结合显微镜分析谱片磨粒沉积效果。结果表明:正己烷溶液、体积分数30%二甲苯和70%正己烷混合溶液适合溶解锂基润滑脂,二甲苯和四氯乙烯适合溶解钙基润滑脂和铝基润滑脂;将润滑脂试样溶液的黏度稀释到4 mm~2/s以下时,在旋转式铁谱仪上能够获得良好的制谱效果。     

锂基润滑脂流变性及摩擦学性能相关性研究

以锂基润滑脂为例,通过 R／S 锥板式流变仪和四球摩擦磨损试验机,对其流变性能及摩擦磨损性能进行研究,探讨润滑脂流变性能与摩擦磨损性能的相关性。结果表明：润滑脂表观黏度随剪切速率的增大逐渐减小,随锥板间隙的增大逐渐增大,随温度的升高逐渐下降,最后均趋于稳定值。润滑脂的平均摩擦因数和磨斑直径随速度的增大先增大后减小,随载荷的增大逐渐增大,随温度的升高先增大后减小。润滑脂的流变性能和摩擦磨损性能随速度、载荷、温度变化的趋势大体一致,表明锂基润滑脂流变性能与其摩擦磨损性能有一定的相关性,为进一步研究润滑脂流变性能与使用性能之间的关系打下了基础。