高载荷条件下石墨-石墨摩擦副的摩擦学特性研究

利用研制的高载荷条件下摩擦因数测试装置,研究了石墨/石墨摩擦副在空气、水和油介质中的摩擦学特性。结果表明在4~15MPa范围内,随着载荷的增加,摩擦副在空气、水和油介质中的摩擦因数都逐渐降低;在油介质中摩擦副的摩擦因数最小,在水介质中摩擦因数变化最平稳,在空气中摩擦因数最大,且随载荷的增加变化幅度最大。磨损表面原始形貌对比分析表明,在空气中,摩擦副表面处于边界润滑状态,主要磨损机制是粘着磨损和犁削;水润滑条件下为轻微犁削;油润滑条件下,摩擦副表面处于为边界润滑和流体润滑状态,油中的减摩剂对试样表面有抛光作用。     

一种新型摩擦材料在水润滑下的摩擦学性能研究

采用环块式摩擦磨损实验研究了一种新型摩擦材料在水润滑状态下不同载荷与转速对试样摩擦学性能的影响,并对比干摩擦条件下的摩擦学性能变化,借助磨损表面形貌观察分析其磨损机理。实验结果表明:水润滑条件下,摩擦系数随着载荷的增大而减小,随着转速的提高先增加后减小;磨损率随着载荷与转速的提高都减小。相同载荷与转速下,干摩擦时磨损机理以磨粒磨损和黏着磨损为主,而水润滑条件下水形成边界润滑,磨损机理以磨粒磨损和轻微的黏着磨损为主;水润滑条件下摩擦系数和磨损率均低于干摩擦,主要是由于水起到了润滑和冷却的作用,阻止了转移膜的形成,并在材料表面形成水膜起到了边界润滑的作用。     

锌铝金（ZA27）润滑时摩擦损特性研究

本研究ＺＡ２７合金在润滑下的摩擦磨损特性。提出在油润滑下ＺＡ２７合金同材质摩擦时，磨损特点是边界润滑摩擦；其与４５钠配副摩擦时，摩擦特点主要的犁削。根据损失重分析得出；ＺＡ２７合金的润滑工况下是一种良好的减摩材料。     

二种锌铝合金润滑时摩擦磨损特性的研究

对二种锌铝合金ＺＡ－ＳｉＴ ＨＤＺＡ在２０号机油润滑条件下的摩擦磨损特性进行了研究。研究发现：该摩擦－润滑系统以边界润滑为主，且伴随有断续的、短暂的混合润滑或弹性流体润滑；磨擦磨损过程中存在着磨粒磨损、接触疲劳和粘着磨损３个磨损机制；二种锌合金在一定条件下具有优良的耐磨性能和减摩性能。研究结果还初步解释了这些试验现象。     

基于不同摩擦副条件下的边界润滑抗磨效果研究

通过不同实验对比，从磨损角度出发分析了不同条件下零件表面的边界润滑状况，提出了选用适当的热处理工艺，恰当的摩擦副接触类型及高性能的润滑液，可明显改善边界润滑效果，提高材料的耐磨性。     

干摩擦和水润滑条件下单晶硅的摩擦磨损性能研究

在UMT-2微摩擦试验机上,对单晶硅片进行了干摩擦和水润滑两种状态下的摩擦磨损试验,分析讨论了载荷和滑动速度对单晶硅片的摩擦因数和磨损率的影响规律;运用扫描电子显微镜,观察和分析了其磨损表面形貌。结果表明:干摩擦条件下的磨损机理主要表现为黏着磨损,水润滑条件下的磨损机理主要表现为机械控制化学作用下的原子/分子去除过程;水润滑条件下的摩擦因数和磨损量均较小,最小磨损率仅为10μm3/s;在水润滑条件下,载荷和滑动速度达到一定值时,硅片表面将发生摩擦化学反应,生成具有润滑作用的Si(OH)4膜,即机械作用在一定条件下对化学反应具有促进作用。     

青铜-石墨热喷涂层在干摩擦和水润滑条件下的摩擦磨损性能

在MM-200摩擦磨损试验机上研究了青铜-石墨热喷涂层在干摩擦和水润滑条件下的摩擦磨损性能,采用扫描电镜(SEM)对磨损表面形貌进行了观测和采用X射线能谱分析(XPS)分析了涂层成分。结果表明,在水润滑条件下涂层摩擦因数和磨损率均低于干摩擦条件下;在水润滑条件下磨损机制为轻微磨粒磨损和犁削磨损,在干摩擦下主要是较为严重的粘着磨损和犁削。这是由于水润滑降低了摩擦副界面温度,提高了石墨润滑膜的韧性,改善了润滑效果,从而阻止了粘着磨损的发生,水还促进了钢偶件表面致密氧化膜的形成,从而减轻磨损。因此水润滑对涂层磨损性能有较大影响。     

玻璃微珠改性热塑性聚酰亚胺摩擦磨损性能

采用MPX2000型摩擦磨损试验机测定5μm和20μm实心玻璃微珠填充热塑性聚酰亚胺复合材料在干摩擦和水润滑两种工况下的摩擦磨损性能，考察了填料含量及尺度的影响。结合扫描电子显微镜（SEM）观察磨损表面形貌分析磨损机制。结果表明：在干摩擦条件下，玻璃微珠在磨损表面富集，起到了良好的承载作用，并以其优异的导热性能和耐高温性能强化了摩擦热的移出，材料磨损率下降1个数量级；大尺寸填料，其单位个体与基体的界面面积和结合强度大于小尺寸填料，其磨损率比小尺度填料填充材料低。在水润滑条件下，水起到冷却及边界润滑作用，材料磨损率较干摩擦条件下降低1个数量级，以疲劳磨损为主；同时，球形颗粒出现应力集中产生疲劳裂纹的程度随颗粒尺度增大而提高，表现为20μm玻璃微珠填充材料磨损率较大。     

原油介质中FKM/NBR混炼胶磨损行为研究

在MPV-600型磨粒磨损试验机上研究相同硬度的氟橡胶和丁腈橡胶及其配比为5∶5和2∶8的混炼胶试样在原油介质润滑条件下的磨损行为,分析在不同载荷、转速下混炼橡胶与金属摩擦副的动态摩擦磨损特性,以期得到性能优异的FKM/NBR混炼胶用于螺杆泵定子。利用体式显微镜观察橡胶试样的磨损形貌,初步分析其磨损机制。结果表明:在原油润滑条件下配比为2∶8的混炼胶具有较低的磨损量和较小的稳态摩擦因数,其磨损量略高于氟橡胶;在原油润滑条件下丁腈橡胶的磨损机制是以磨粒磨损为主,而混炼胶和氟橡胶则以疲劳磨损为主。     

氧化铝陶瓷在海水润滑下的摩擦学行为研究

采用UMT-3摩擦实验机研究氧化铝陶瓷在海水润滑条件下的摩擦学行为,并与其在干摩擦和纯水润滑条件下的摩擦学行为进行比较。利用扫描电子显微镜和X-射线光电子能谱观察并分析氧化铝陶瓷磨损表面形貌以及磨损表面主要元素的化学状态,探讨氧化铝陶瓷在海水中的摩擦化学特性。结果表明,氧化铝陶瓷在干摩擦时具有最大的摩擦因数和最小的磨损率,在海水润滑条件下具有最小的摩擦因数和最大的磨损率,这是氧化铝在海水中发生了摩擦化学反应的结果。氧化铝陶瓷在干摩擦时的磨损主要表现为轻微的脆性剥落,在纯水润滑条件下表现为严重的脆性剥落,而在海水润滑条件下表现为摩擦化学磨损以及极轻微的脆性剥落。     

Experimental characterization and analysis of wet belt friction and the vibro-acoustic behavior

The robustness and noise warranty costs of rubber belts used for power transmission are directly affected by the frictional properties under varying environmental conditions. This paper presents an experimental characterization and analysis of the friction and vibro-acoustic behavior of automotive ribbed rubber belts under wet conditions. The experimental results show that the static friction under wet condition is higher than the corresponding kinetic friction by 40%-1040% for different belts; and the wet static friction is also much higher than the dry static friction. The wet kinetic friction is lower than the dry kinetic friction by about 30-40%. The occurrence of wet static friction is associated with the strong noise of the belt system. The spectrogram analysis of recorded sound demonstrates that the sound exhibits an impulsive sound pattern with broadband frequency extending to 20 kHz. In this study, the belt vibration is also measured and the spectrum results correlated with those of the sound measurement. The capillary effect, dry adhesive effect and the boundary lubrication effect are discussed based on adhesion models, which are used to correlate with experimental results and to interpret the effects of relevant parameters. The presented results are based on the start-up running of a newly developed belt-pulley test rig, which are different from some published results based on SAE Standard J2432. The test rig based on SAE Standard J2432 is actually operated as water lubricated coast-down, which is not applicable to characterizing the friction properties of belt in wet start-up running.     

Wear properties of Saffil/Al,Saffil/Al2O3/Al and Saffil/SiC/Al hybrid metal matrix composites

The purpose of this study is to investigate the wear properties of Saffil/Al, Saffil/Al₂O₃/Al and Saffil/SiC/Al hybrid metal matrix composites (MMCs) fabricated by squeeze casting method. Wear tests were done on a pin-on-disk friction and wear tester under both dry and lubricated conditions. The wear properties of the three composites were evaluated in many respects. The effects of Saffil fibers, Al₂O₃ particles and SiC particles on the wear behavior of the composites were elucidated. Wear mechanisms were analyzed by observing the worn surfaces of the composites. The variation of coefficient of friction (COF) during the wear process was recorded by using a computer. Under dry sliding condition, Saffil/SiC/Al showed the best wear resistance under high temperature and high load, while the wear resistances of Saffil/Al and Saffil/Al₂O₃/Al were very similar. Under dry sliding condition, the dominant wear mechanism was abrasive wear under mild load and room temperature, and the dominant wear mechanism changed to adhesive wear as load or temperature increased. Molten wear occurred at high temperature. Compared with the dry sliding condition, all three composites showed excellent wear resistance when lubricated by liquid paraffin. Under lubricated condition, Saffil/Al showed the best wear resistance among them, and its COF value was the smallest. The dominant wear mechanism of the composites under lubricated condition was microploughing, but microcracking also occurred to them to different extents.     

Effect of rubber on tribological behaviors of polyamide 66 under dry and water lubricated sliding

The friction and wear behaviors of polyamide 66 (PA 66) and rubber-filled PA 66 (PA 66/SEBS-g-MA) composites were investigated on a block-on-wheel model friction and wear tester under dry sliding and water lubricating conditions. In order to further understand the wear mechanisms, the worn surfaces and scraps of samples were analyzed by scanning electron microscopy (SEM) and differential scanning calorimeter (DSC). The experimental results indicated that the wear mass loss and the friction coefficient of PA 66 decreased with the addition of rubber particles. The friction coefficients of PA 66 and PA 66/SEBS-g-MA composites under water lubricating condition are lower than those under dry sliding condition, but the wear mass losses are higher than those under dry sliding condition. The main wear mechanisms under dry sliding condition are the plastic deformation and mechanical microploughing. Whereas the main wear mechanisms under water lubricating condition are the mechanical microploughing and abrasive wear.     

Friction and wear behaviour of Thordon XL and LgSn80 in sliding against plasma-sprayed Cr2O3 coatings

This paper studies the friction and wear behaviour of two important bearing materials, Thordon XL and LgSn80, in dry and lubricated sliding vs. plasma-sprayed Cr₂O₃ coatings. As a reference, AISI 1043 steel is also studied under the same conditions. SEM, EDS and surface topography were employed to study the wear mechanisms. The results indicate that the Thordon XL/Cr₂O₃ coating pair gives the lowest dry friction coefficient (0.16) under a normal load of 45.3 N (pressure 0.453 MPa) at a velocity of 1 m/s. The dry friction coefficient of Thordon XL/Cr₂O₃ coating increases to 0.38 under a normal load of 88.5 N (pressure 0.885 MPa). The dry friction coefficients of the LgSn80/Cr₂O₃ coating are in the range of 0.31–0.46. Secondly, both dry wear rate under low normal load (45.3 N) and lubricated wear rate under a load of 680 N for Thordon XL are lower than those of LgSn80 in sliding against plasma-sprayed Cr₂O₃ coatings at a speed of 1 m/s. However, under a normal load of 88.5 N the dry wear rate of Thordon XL is much higher than that of LgSn80. Thirdly, a high viscosity lubricant (SAE 140) leads to lower wear for Thordon XL and LgSn80 than a low viscosity lubricant (SAE 30). Finally, the dominating wear mechanism for Thordon XL is shear fracture when against the plasma-sprayed Cr₂O₃ ceramic coating. For LgSn80 against plasma-sprayed Cr₂O₃ ceramic coating, abrasive wear is the governing failure mechanism.     

Assessment and application of TiB2 coating in sliding pair under lubrication conditions

The aim of the present work is to determine the influence of TiB₂ coating on the friction parameters in sliding pairs under lubricated friction conditions. The TiB₂ coating deposited on modified surface layers of ring specimens made of AISI 5045 steel was matched under test conditions with counterparts made from SAE-783 and SAE-48 bearing alloys. Tested sliding pairs were lubricated with 5 W/40 Lotos synthetic engine oil. Tribological properties of the TiB₂ coating were measured using a block-on-ring tribometer. The applied modification technology of the surface layer of steel allowed for obtaining construction material with pre-determined tribological characteristics required for the elements of sliding pairs in lubricated contact. The results showed differences in the wear of bearing alloys, as a result of the interaction between co-operating surface layers and of the physiochemical changes of their surfaces, induced by external forces. Friction resistance and temperature in the friction area in the pair with TiB₂ coating and the SAE-783 bearing alloy are considerably higher than in the pair with the SAE-48 bearing alloy. The SAE-48 bearing alloy is subjected to more intensive wear processes in contact with the TiB₂ coating than the SAE-783 bearing alloy.     

Effect of Friction Modifier on Rolling Contact Fatigue and Wear of Wheel and Rail Materials

In this study, the effects of a friction modifier (FM) on wear and rolling contact fatigue were investigated by twin-disc testing under various conditions. It was found that the contact fatigue damage occurred on the rail specimen under the FM condition and the water condition. The test under FM condition was performed under three different spraying times: 0.2, 0.5, and 1.0 s. The progress of contact fatigue damage severely increases at a spraying time of 0.2 s. Contact fatigue damage under the FM condition occurred faster than that under the water condition. Results show that the friction modifier induced a mixed condition that exists at the same time as the wet condition and the dry condition. Cracks were initiated by the traction force due to the friction of the dry condition and the crack growth rate became faster due to the fluid entrapment mechanism under the wet condition. Therefore, the amount of FM should be evaluted to avoid severe contact fatigue damage.     

等离子喷涂陶瓷涂层在高温（450℃）下的摩擦磨损机理分析

本文用SEM观察分析了等离子喷涂陶瓷涂层（Metco136F,Metco80NS,Metco102,Metco105,Metco202NS,国产Al 2O 3）在高温无油和有油润滑下的摩擦磨损机理。发现陶瓷涂层仍会象金属摩擦副那样出现疲劳脱落、塑性形变、粘着撕裂。450℃时的干摩擦系数比有油润滑的摩擦系数高得多,且磨损表面形貌和磨损机理与有油润滑时大为不同。干磨擦是较易出现粘着磨损,而有润滑时则较难出现。     

湿滑状态下轮胎路面摩擦特性的数值分析方法

为研究湿滑状态下轮胎路面的摩擦特性,以胎面橡胶和沥青路面作为研究对象,利用谐波叠加法建立三维粗糙路面模型,采用“伪”流体动力轴承作用等效反映路面水膜“密封”作用,综合使用有限元软件ABAQUS和计算流体动力学软件Fluent得到湿滑状态下橡胶与路面滑动接触时的橡胶接触压力、滞后摩擦力及路面水膜承载力,由此形成了综合兼顾橡胶材料、接触压力、滑动速度、路面形貌和路面水膜等多因素的轮胎与湿路面摩擦特性的仿真方法。通过橡胶与干-湿路面摩擦特性的变化与公开的试验对比,证明本方法的合理性和可行性,并进一步分析滑动速度、接触压力和路面特征对湿滑状态下轮胎路面摩擦特性的影响规律。研究结果为轮胎和路面的抗湿滑性设计及优化提供理论依据。     

水凝胶/热塑性聚氨酯复合材料在水润滑条件下的摩擦学性能

为提高水润滑轴承的承载能力，利用水凝胶在水润滑条件下的水合作用来改善热塑性聚氨酯（TPU）轴承材料的摩擦学性能。利用聚乙烯醇、海藻酸钠、壳聚糖等材料制备水凝胶颗粒，并通过熔融共混法制备水凝胶/TPU复合材料；在0.3和0.5 MPa的载荷下测试复合材料的摩擦磨损性能，利用激光干涉表面轮廓仪和扫描电子显微镜观察其磨损表面形貌，分析其磨损机制。结果表明：水凝胶微粒可以通过水合润滑改善摩擦副的润滑条件，从而降低摩擦因数和磨损量，提高复合材料的摩擦性能；水凝胶质量分数4%时复合材料具有最佳的摩擦磨损性能，其在0.3和0.5 MPa工况下相对于TPU试样的平均摩擦因数减少率分别为52.31%和43.94%。研究结果为开发高性能水润滑轴承材料提供了一种方法。     

橡胶滑块与镀镍钢环的水润滑机理分析

对水润滑橡胶轴承在完全水润滑条件下的标准实验模型进行了弹流理论建模,应用多重网格技术对理论模型进行了数值计算和结果分析。结果表明:完全水润滑条件下,在高速轻载时形成了弹流润滑,而在低速重载时,即使在完全水润滑条件下橡胶滑块与镀镍钢环之间也较难形成稳定的弹流润滑。计算结果与实验结果基本一致。