外加电压对边界润滑下钢/铜摩擦副摩擦磨损的影响

利用球盘式摩擦试验机，针对150SN油润滑下的GCr15/ZCu10Fe3摩擦副，研究了不同极性的外加直流电压对其摩擦系数和磨损状态的影响，并结合磨痕的能谱分析，探讨了外加电压对其摩擦磨损性能的作用机理。     

混合型轴承摩擦机理的研究

采用Timken摩擦试验机在空气中,水、润滑油及合成油脂润滑状态下对M50钢、热静等压氮化硅陶瓷轴承元件的摩擦机理进行了研究.对各种参数包括速度、滑动距离和润滑剂进行了比较.     

Friction and Wear Characteristics Due to Stick-Slip under Fretting Conditions

Friction and wear characteristics between two steel surfaces under fretting conditions are investigated experimentally. The fretting damage caused by low-amplitude oscillatory sliding can be classified into three regimes of gross-slip, mixed-slip, and partial-slip due to the stick-slip phenomenon. One of the most important characteristics of fretting wear is the transition from gross-slip to mixed-slip. Several criteria have been introduced for a quantitative determination of the transition between mixed-slip and gross-slip. However, the transition criteria have some problems in determining the regimes because parameters are difficult to calculate or depend on the system. To introduce new transition criteria in this study, the phase difference between friction force and relative displacement is used to determine the transition and predict the fretting wear. It is found that the phase difference with a range of 0° to 90° can predict the onset of fretting conditions.     

硅油润滑对莫来石基陶瓷摩擦磨损性能的影响研究

莫来石基陶瓷具有一系列优异的性能,其在摩擦学领域中的应用越来越广泛。本文研究了硅油润滑对该类陶瓷摩擦磨损性能的影响规律。研究结果表明,硅油可明显地降低莫来石基陶瓷的摩擦系数和磨损率,但却使摩擦系数在稳定阶段的波动幅度增加。硅油润滑条件下,莫来石基陶瓷的磨损机理主要是微观断裂和磨料磨损。     

润滑油添加剂对聚合物材料摩擦磨损性能的影响研究

利用MM－200型磨损试验机考察了ZDDP对聚合物材料（PTFE、PI及MCPA）－GCr15轴承钢摩擦副摩擦磨损性能的影响。研究发现，液体石蜡及含ZDDP的液体石蜡润滑均可大幅度改善聚合物材料的摩擦磨损性能，且使其摩擦系数比干摩擦时降低一个数量级，摩擦副表面的ZDDP吸附膜均在不同程度上提高聚合物材料的耐磨性，但其对聚合物材料的摩擦性能影响不大。     

Ni—P—Si3N4复合镀层的磨损特性

本文通过Ｘ射线衍射分析、电子探针分析和摩擦磨损试验，分析了电沉积Ｎｉ－Ｐ－Ｓｉ３Ｎ４复合镀层的结构性能和磨损特性，并比较了不同弥散微粒的影响。结果表明，在油润滑条件下，复合镀层中的Ｓｉ３Ｎ４微粒在支承载荷的同时，有利于边界润滑膜的形成，避免粘着磨损。同时由于Ｓｉ３Ｎ４微粒本身具有的结构特征，提高了复合镀层的耐磨性能。     

Acoustic Emission and Its Relationship with Friction and Wear for Sliding Contact

Further investigation of the relationships between friction and wear properties and the characteristics of acoustic emission was conducted in the case of dry and grease-lubricated sliding contact using a ball-on-cylinder testing apparatus. The effect of contamination simulated by the inclusion of glass bead particles was also explored. Experiments were performed at sliding speeds ranging from 0.09 m/s to 1.47 m/s, while maintaining a fixed load and duration. As a first observation and contrary to what could be expected, the higher speed did not contribute to the decrease in friction interpreted by a worsening of the starved regime that had a consequence of increasing wear. However, the results revealed a good correlation between the friction coefficient and acoustic emission (AE) rms voltage for dry sliding. Such a relationship may allow the prediction of a reasonable friction coefficient μ from an AE signal. It was also determined that the friction work correlated well with the corresponding integrated AE voltage over time, intRMS. The detection of the sliding speed threshold beyond which accelerated wear would occur was possible from the intRMS variation. Proportionality between the theoretically determined grease film thickness and the intRMS was observed.     

Optimization of Extreme Load and Break-in Period in Plain ZDDP Oil with FeF3 Catalyst Using Design of Experiment and Fundamental Study under Different Speeds

The mechanism of tribofilm formation and breakdown was carefully followed and studied in 0.1 P% (percentage phosphorus content) plain zinc dialkyldithiophosphate (ZDDP) oil in the presence of iron fluoride (FeF₃) catalyst under extreme Hertzian contact pressure (3.0 GPa) and two different rotational speeds or variable speed with break in period (100 rpm for the first 5,000 revolutions and a 700 rpm until failure or 100,000 revolutions, whichever comes first). At the onset of large frictional fluctuations, the contact surface temperature increased significantly and reached 90°C ± 5°C. The present article describes an innovative method of reducing the surface temperature by using a break in period of 2 or 3 min and rerunning the test until failure. The two different rotational speeds or variable speed will be compared to a steady-state speed of 700 rpm.

Thermal decomposition of ZDDP is examined in the presence of powder and dispersed FeF₃ using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Surface analyses were carried out using scanning electron microscopy (SEM) coupled with X-ray of the wear tracks, transmission electron microscopy (TEM), and auger electron spectroscopy (AES). Results showed that submicrometer dispersed FeF₃ provided excellent wear protection when combined with ZDDP in the variable-speed test with break-in by forming a tribofilm that is amorphous in nature and rich in phosphorus, which was shown by the TEM and X-ray analyses.     

湿煤粉条件下丁腈橡胶摩擦磨损规律的研究

国内外对橡胶材料在煤粉条件下的摩擦磨损特性尚缺乏研究,因而对丁腈橡胶在湿煤粉条件下的磨料磨损进行了研究,发现其磨损机理为疲劳磨损,磨损率随着法向载荷的增大而增大,随着放置速度的增大而减小;而摩擦系数则与法向载荷和旋转速度大致无关,其中水份在丁腈橡胶磨料磨损中主要起着三个作用：⑴对煤粉的粘结作用;⑵水膜的润滑作用;⑶降低瓣工作温度。     

Wear and Friction Characteristics of a Selected Stainless Steel

Dry sliding wear tests were performed for 3Cr13 steel with various tempered states at 25–400°C; wear and friction characteristics as well as the wear mechanism were explored. With an increase in test temperature, the wear rate decreased accompanied by an increase in tribo-oxides. The fluctuation of friction coefficient was slight at 25–200°C but became violent at 400°C. At 25–200°C, adhesive wear prevailed due to trace or less tribo-oxides; at 400°C, oxidative wear prevailed with the predominant tribo-oxides of Fe₃O₄ and Fe₂O₃. It can be suggested that the antioxidation of the stainless steel postponed the occurrence of oxidative wear to a higher test temperature. For adhesive wear, the wear resistance, roughly following Archard's rule, was directly proportional to hardness besides the specimen tempered at 500°C with grain boundary brittleness. But for elevated-temperature wear, a better wear resistance required thermal stability and an appropriate combination of hardness and toughness.     

Friction and Wear of Refractory Compounds

The sliding characteristics of the borides, carbides, nitrides, and silicides and oxides of several metals were investigated in air at temperatures up to 2000 F. Tests were of the crossed-cylinder type and friction and wear effects measured under repetitive sliding conditions.

Correlation of the friction and wear characteristics with known or predicted solid solubility was only fair. High hardness coupled with low fracture strength and excessive brittleness of these materials produced fracturing of asperities and abrasive wear before a true measure of the adhesion could be obtained. Oxidation products were found to provide some lubrication at elevated temperatures, particularly the formation of B₂O₃ on boron carbide. However, none was effective at room temperature.     

Silicon Nitride Boundary Lubrication: Effect of Oxygenates

A ball-on-three-flat (BTF) wear tester was used to investigate the boundary lubricating characteristics of oxygenates on a commercial silicon nitride. A wide variety of oxygen-containing compounds were tested neat and/or at 1% by weight in a paraffin oil. Compounds containing hydroxyl functional groups were more effective compared to a base case of neat paraffin oil. Decreases of up to 58% in friction coefficient, and 95% in wear were obtained. In most cases, films were observed in and around the wear scar, suggesting chemical reactions had taken place in the contact.

Additional wear tests, conducted using neat shorter-chain linear primary alcohols, i.e., 6–10 carbons, demonstrated boundary lubrication protection, with longer chain length providing better antiwear performance. A study of several C₈ compounds with specific oxygen-containing functional groups (primary alcohol, secondary alcohols, acid, aldehyde, and ketone) demonstrated that the primary alcohol had the strongest boundary lubricating effect. Varying the amount of water in the alcohols had little effect on friction and wear, suggesting that the boundary lubrication effects observed were not merely due to dissolved water in these fluids, but some characteristic chemical interaction with the hydroxyl functional group of the alcohols and acids.     

Evaluation of Ball-Bearing Performance in Liquid Hydrogen at DN Values to 1.6 Million

Experimental data were obtained in liquid hydrogen (?423 F) on two series of 40-mm-bore ball bearings utilizing various retainer materials. Effects of diametral clearance and retainer material on limiting DN value (product of bearing bore in mm and shaft speed in rpm) were investigated at thrust loads to 500 lb and at speeds to 41,200 rpm. An analysis was made to determine the effect of ball size and race curvatures on the heat generated in bearings of both series as a result of ball spin. The results, supported experimentally, indicate that higher limiting DN values at a specific thrust load could be obtained with an extremely light series (1908) bearing with open-race curvatures than with a light series (108) bearing. Successful operation to a DN value of 1.6 million was obtained with 1908 bearings (at 110 lb thrust load) using two different retainer materials. The glass-fiber-filled PTFE (polytetrafluoroethylene) retainer exhibited much less wear than the MoS₂-filled phenolic retainer at these test conditions.     

磁流体密封摩擦功耗的研究

随着磁流体密封应用范围不断扩大,在密封区域因磁流体摩擦功率损失而引起的温升,已经引起设计人员重视,并成为密封形式选择的重要参数之一。本文在分析密封区域磁流体运动速度分布的基础上,给出摩擦功率损失的计算式,通过对多种工况进行计算,与实验结果相差甚小,可供设计时使用。     

基于Bingham模型的磁流变阻尼器的优化设计

利用磁流变液这种智能材料设计制作阻尼耗能器件在近些年得到了广泛重视,但多数采用经验公式决定结构尺寸的方法具有片面性。本文利用Bingham轴对称模型并根据具体使用要求优化设计了阻尼器的结构参数,并编程进行了计算。根据计算结果制作的磁流变阻尼器经测试其性能达到了预期的要求,表明优化设计方法是正确可行的。     

Influence of Lubricant Additive and Surface Texture on the Sliding Friction Characteristics of Steel under Varying Speeds Ranging from Ultralow to Moderate

A newly developed tribometer that undergoes significant changes in sliding speed, ranging from ultralow (5 μm/s) to moderate (17 cm/s), was used to study the lubricated friction characteristic of steel. In this study, the friction characteristics of stearic acid-formulated oil were studied to clarify the effects of surface roughness or surface roughness texture on friction. Several kinds of specimens having isotropic and anisotropic surface roughness with different textures were used. For an isotropic surface, a rougher surface resulted in low friction under low-speed conditions. The same surface produced high friction under high-speed conditions, where macroscopic hydrodynamic action was predominant. Remarkably less friction was observed in the transverse than in the longitudinal direction when the specimen had anisotropic roughness. This difference was particularly notable under ultra-low-speed conditions. Two other parameters of skewness and kurtosis of roughness distributions show that low friction was obtained when surface roughness distribution approached normal. It appears that the low friction observed with a rough surface or a transverse roughness direction could be explained by the microscopic hydrodynamic action of fluid together with the lubricity of the adsorbed molecular layer.     

钢铜摩擦副摩擦磨损特性的试验研究

本文试验分析了ＺＱＡ１９－４和ＺＱＺｎ６－６－３两种铜合金材料在不同的表面粗糙度下对摩擦系数和出口区油温的影响，以及改变载荷和相对滑动速度时，摩擦系数的变化状况。结果表明；铜合金成分不同时具有不同的硬度。     

Comparative Study on Wear Characteristics between Flow Mode and Shear Mode Magnetorheological Dampers

This comparative study experimentally examines the wear characteristics of magnetorheological (MR) dampers operated in flow mode and shear mode. First, electromagnetic coil structures are designed for two different MR dampers to maximize the field-dependent damping force. Two MR dampers are also designed to have the same volume of MR fluid for reasonable comparison. After identifying the field-dependent damping force at the initial state, the two dampers are operated up to 60,000 cycles using a reciprocating-type wear durability tester. The field-dependent damping forces are then evaluated before and after operation. The wear properties of the MR fluid are investigated using scanning electron microscope (SEM) images that show the changes in the MR fluid particles' size and shape. The surface roughness of the MR damper's piston areas are also measured. In addition, the effects of the permeability of the piston sleeve materials on the wear properties are investigated by selecting three different sleeve materials that have different permeability values: 0.2% carbon steel (S20C), 0.45% carbon steel (S45C), and tool die casting steel (STD-11). The surface roughness of each case is tested and the atomic spectrum is investigated after long operation using energy-dispersive X-ray spectroscopy (EDS) inside the piston. The experimental results obtained from this work indicate that the motion of the operating mode significantly affects the wear characteristics of the MR fluid itself as well as the magnetic effective areas of the MR dampers.     

Friction and Wear Properties of TiAl-Ti3SiC2-MoS2 Composites Prepared by Spark Plasma Sintering

TiAl matrix self-lubricating composites (TMC) with various weight percentages of Ti₃SiC₂ and MoS₂ lubricants were prepared by spark plasma sintering (SPS). The dry sliding tribological behaviors of TMC against an Si₃N₄ ceramic ball at room temperature were investigated through the determination of friction coefficients and wear rates and the analysis of the morphologies and compositions of wear debris, worn surfaces of TMC, and the Si₃N₄ ceramic ball. The results indicated that TMC with 10 wt% (Ti₃SiC₂-MoS₂) lubricants had good tribological properties due to the unique stratification subsurface microstructure of the worn surface. The friction coefficient was about 0.57, and the wear rate was 4.22 × 10^?4 mm³ (Nm)^?1. The main wear mechanisms of TMC with 10 wt% (Ti₃SiC₂-MoS₂) lubricants were abrasive wear, oxidation wear, and delamination of the friction layer. However, the main wear mechanisms of TMC without Ti₃SiC₂ and MoS₂ lubricants were abrasive wear and oxidation wear. The continuous friction layer was not formed on the worn surfaces. The self-lubricating friction layer on the frictional surface, different phase compositions and hardness, as well as density of TMC contributed to the change in the friction coefficient and wear rate.     

The Friction and Wear Model of Steels and Their Probable Statistic Calculations

Based on a systematic analysis of steel wear surfaces by Scanning Electron Microscopy (SEM) and Auger Electron Microscopy (AES), a statistical model for friction and wear of steels is proposed. Three categories of contact are proposed; oxide-oxide, metal-metal, and metal-oxide. Each category of contact is related to a probability distribution on the real contact area. Using a new concept of nascently exposed metallic surfaces, this paper derived the mathematical expressions for the friction coefficient and wear rate by means of statistical methods. The calculated values are in good agreement with measured values.