油润滑条件下有机物修饰纳米铜颗粒改善铁基摩擦副摩擦磨损的研究

在球盘式摩擦磨损试验机上考察了有机物修饰的纳米铜颗粒作为50CC润滑油添加剂的摩擦学性能;采用SEM和EDS分析了磨损表面形貌和表面膜元素组成。探讨了纳米铜颗粒的摩擦学作用机制：结果表明：有机物修饰的纳米铜颗粒作为添加剂能显著改善50CC润滑油的抗磨减摩性能,含0．05％纳米铜油样润滑下的摩擦因数与磨损量同基础油润滑下相比分别降低了27．6％与60％。分析后认为,纳米铜颗粒通过对摩擦表面进行修复及在摩擦表面成膜两种作用有效地改善了摩擦磨损性能。     

含硫化铜纳米粒子润滑脂的微动磨损性能研究

在微动磨损试验机上考察了含有硫化铜纳米粒子脲基脂的微动磨损性能。结果表明:硫化铜纳米粒子能显著降低微动磨损体积,随着纳米粒子含量增加,微动磨损量降低;在微动磨损后期纳米粒子的存在还能降低摩擦因数。低负荷下,润滑脂中硫化铜纳米粒子有利于降低微动磨损量;但在高负荷条件下,磨损量迅速增大,说明高负荷下微动磨损方式发生了变化。XPS分析表明,微动磨斑表面膜含有Cu、FeS等物质,说明硫化铜纳米粒子能显著降低微动磨损的原因在于纳米粒子化学性质非常活泼,在微动过程中容易与摩擦表面发生化学反应,形成具有保护性的沉积物膜和化学反应膜。     

Theoretical surface temperatures generated from sliding contact of pure metallic elements

Surface temperatures and thermal effects produced in tribological processes are important not only in influencing possible mechanisms of friction, wear, and lubricant film failure but also in initiating protective film-formation. As part of a continuing combined theoretical and experimental study of surface temperatures generated by friction, the fundamental Green's function approach has been applied to a number of pure metallic elements to compare and discuss their predicted behavior in A-on-A sliding contact. Assuming a single area of real contact, calculated ratios of surface temperature rise to coefficient of friction plotted against area of contact, velocity and load on a logarithmic scale are presented and summarized for several pure metallic elements in the first transition series of the Periodic Table (e.g., Ti, V, Cr, Mn, Fe, Co, Ni) as well as members in connecting groups, e.g., Cr, Mo, and W in Group VIa and Cu, Ag, and Au in Group Ib. These include metals which are tribologically difficult to machine and use (e.g., Ti), common elements in bearing steels (e.g., Fe, Cr), and metals useful in reducing friction or wear when applied as thin surface coatings (e.g., Ag, Au). The results of this comparison are interesting and surprising. They may add to our understanding of why some metals are very “difficult” in a tribological sense while others provide benefits in controlling friction and/or wear.     

干摩擦条件下表面成膜添加剂的应用研究

本文以制动摩擦副为例，讨论了在摩阻材料中添加含氟、硫或铜元素的化合物时，与金属对偶件在干摩擦条件下其表面膜的形成机理，探讨了不同成膜添加剂对摩阻材料的摩擦磨损特性的影响。试验表明：含硫的成膜剂，可减少对偶件表面的磨损，但不利于稳定摩擦系数；而添加含氟和铜化合物的成膜剂，既利于减少对偶件表面的磨损，又可提高摩擦的稳定性。文中提出了在干摩擦条件下，在摩阻材料中添加表面成膜剂是控制或稳定摩擦系数及减少磨损的重要途径，并在实践中得到了验证。     

Dynamical Evolution of Wear Particles in Nanocontacts

Nanoscale surface modification, by the interaction of sliding surfaces and mobile nanoparticles, is a critical parameter for controlling friction, wear and failure of surface structures. Here we demonstrate how nanoparticles form and interact in real-time at moving nanocontacts, with reciprocating wear tests imaged in situ at the nanoscale over >300 cycles in a transmission electron microscope. Between sliding surfaces, friction-formed nanoparticles are observed with rolling, sliding and spinning motions, dependant on localised contact conditions and particle geometry. Over periods of many scratch cycles, nanoparticles dynamically agglomerate into elongated clusters, and dissociate into smaller particulates. We also show that the onset of rolling motion of these particles accompanies a reduction in measured friction. Introduction of nanoparticles with optimum shape and property can thus be used to control friction and wear in microdevices.     

Fretting wear behavior of nanocrystalline surface layer of copper under dry condition

Unlubricated fretting tests were performed with a nanocrystalline surface layer of a 99.99 wt.% copper fabricated by means of surface mechanical attrition treatment (SMAT), in comparison with a coarse-grained (CG) copper. The measured friction and wear data show that the fretting wear resistance is markedly enhanced with the nanocrystalline surface layer relative to the CG counterpart. The friction coefficient and wear volume of the SMAT Cu are lower than that of the CG Cu. For both samples, the friction coefficients and wear volumes increase with an increasing applied load and fretting frequency. A rapid increase of the friction coefficient and wear volume under an applied load above a critical value (30 N for the SMAT Cu and 20 N for the CG Cu) is noticed, corresponding to the formation of a continuous oxide layer between two contact surfaces. Also two sharp increases of the friction coefficient and wear volume at fretting frequencies of 50 Hz and 175 Hz were observed for the SMAT and the CG Cu. The former is correlated with the formation of a continuous oxide layer, while the latter corresponds to wearing away of the oxide layer.     

Stribeck Curve Under Friction of Copper Samples in the Steady Friction State

The friction and wear of a pure copper block (99.98 wt% Cu) against a hardened steel disc were studied. The effect of sliding velocity and load on the friction coefficient and wear rate of Cu samples during steady tests was studied. Elasto-hydrodynamic (EHL), mixed (ML) and boundary lubrication (BL) regions were analyzed using the Stribeck curve. The lubrication number of Schipper, Z, was used in the analysis of the Stribeck curve. The transitions from one lubrication region to another are discussed. The mixed EHL region is characterized by stable low values of the friction coefficient, wear rate and temperature. Straight asperity contact is the dominant mechanism under friction of Cu–steel pair in the BL region. High-friction coefficients and wear rates, thin lubricant films and large wear grooves indicate straight asperity contact between rubbed surfaces in the BL region. Although the dominant mechanisms in the mixed EHL and BL regions are different in principle, a steady friction state is preserved in both cases. It is expected that the steady friction state in the BL and mixed EHL regions is associated with deformation and fracture of surface layers but these process occur at different scale levels. It was shown that under friction of Cu–steel pair, two types of ML regions are observed. The first is the stable steady friction of mixed EHL with low values of the friction coefficient and wear rate. The second type of the ML region is the region of unstable friction and wear when a decrease of lubricant film leads to a change of external (roughness, temperature, friction and wear) and internal (strain and stress) parameters. It was found out that a transition to the unstable ML region occurs within a narrow range of Z parameter under definite values of the load and sliding velocity.     

不同转速下弹性环滚动载流摩擦性能和损伤分析

采用内滚道、外滚道和弹性环组成滚动载流摩擦副，通过载流摩擦试验研究了其在不同转速下的载流摩擦学性能和材料损伤。结果表明：随着转速从240 r/min增加到600 r/min,摩擦副稳态运行期间的摩擦力升高，接触电阻下降；摩擦前期材料损伤形式主要以接触表面金属塑性变形为主，摩擦平稳期以材料剥落为主；在相同的初始接触条件下，高转速促进表面疲劳和材料磨损，试验后弹性环磨痕宽度明显变宽，磨损量逐渐增大，表面氧化程度下降，O和Cu原子个数比降低；磨痕宽度增幅相近的条件下，同等转速下的摩擦力增幅小于变速条件下的摩擦力增幅；转速增加引起的摩擦力增大与高转速下弹性环滑滚增加也有关系。     

7075铝合金和QRO90模具钢在热成形工况下的摩擦磨损行为

铝合金在热成形制造过程中存在严重的模具磨损,不但缩短模具使用寿命,还造成工件表面拉毛和成形偏差。为模拟模具钢与7系铝合金在热成形工况下的摩擦过程,搭建单向高温摩擦磨损试验平台,对热成形工况下的摩擦磨损行为展开研究,并通过光学轮廓仪和扫描电镜分析模具钢与铝合金磨损表面形貌。结果发现,热成形过程中黏结磨损和磨粒磨损同时存在,磨损颗粒在粗糙表面上被压实和堆积,对后续的摩擦磨损行为有显著影响。对单向高温摩擦试验的接触副局部进行有限元建模,分析粗糙接触表面上的局部接触条件,探讨其对后续摩擦学行为的作用。分析表明,摩擦过程中存在黏滑现象,局部接触压力受表面形貌影响,显著大于名义载荷,最大等效应力出现在表面之下。这对进一步分析磨损行为、提出合适的表面工程方案提供了基础。     

IF-MoSe_2纳米材料在液体石蜡中的摩擦学性能研究

将采用化学气相沉积反应法制备的IF-MoSe2纳米材料和片层状MoS2分别添加到液体石蜡中,用Span80作为分散剂分散后在UMT-2摩擦实验机上进行摩擦试验,采用扫描电镜观测磨痕形貌和纳米在摩擦表面的分布,通过测量接触表面油膜的电阻和接触点沿法向的坐标分析摩擦过程的变化.结果显示,IF-MoSe2纳米材料作为润滑油添加剂具有比片层状MoS2更加优越的减摩抗磨性能;通过测量油膜电阻可以监测摩擦表面的成膜状况;接触点法向坐标反映磨痕的形貌,并且在边界润滑状态下,摩擦因数曲线的变化直接受接触点法向坐标的影响.     

小模数,多齿数行星齿轮传动及其在采煤机械中的应用

作者提出与以往齿轮设计配齿原则不同的按小模数、多齿数设计行星齿轮传动的观点。分析了该设计法优点及应用条件，并指出确定模数、齿数的方法。最后，结合ＭＧ３００－ＡＷ１采煤机例子，介绍了实际应用效果。     

Effect of deformation of the contact surface on wear and friction—a study on clarification of the mechanism of abrasive wear

The cutting action due to a protuberance between the rubbing surfaces in abrasive wear might be susceptible to adhesion at the rake surface in the direction of sliding.

In the present paper we discuss an approach to clarify the abrasive wear mechanism, which is dominated by the effect of the difference in the contact deformation between both surfaces on wear and friction related with abrasive wear, on the basis of experiments conducted under ultrahigh vacuum.

Although in practice it is generally very difficult to obtain a characteristic surface during sliding, we carried out experiments on surfaces that were as clean as possible to investigate the effect of the size of the deformed contact surface on the abrasive wear.

Consequently, we were able to confirm that the friction differs according to which of the test pieces is the harder and, if the friction pair is composed of the same material, because the contact surface is deformed differently in each case.     

内燃机活塞环-缸套摩擦热力学系统的分析

活塞环与缸套相互接触并发生相对滑动，则出现摩擦，导致两摩擦表面的材料不断损失。即磨损，同时也使材料表面的温度升高。因此，摩擦、磨损和温升往往是同时出现的。研究三者的关系，对于减少活塞环与缸套的摩擦、控制其磨损、降低接触部位的温升是十分有用的。从热力学第一定律出发，建立了上述三者的定量关系，并分析了不同摩擦状态下各个量的相互影响。     

轮轨接触界面摩擦管理研究进展

列车向着高速与重载方向迅速发展,显著加剧了轮轨接触界面间的损伤。通过在轮轨接触界面进行摩擦管理能够有效地降低轮轨之间的磨损、显著提高列车的运行安全性以及降低运营成本。对轮轨接触界面摩擦管理研究现状进行综述,并介绍轮轨界面摩擦控制对轮轨作用力、黏着、磨耗、滚动接触疲劳以及振动与噪声影响的研究进展;展望了轮轨接触界面摩擦管理未来研究方向,即应针对不同应用环境和接触部位,研发合理的摩擦控制材料,以克服摩擦管理过程中对轮轨损伤及使用局限性等问题;应探究车轮踏面/轨顶面和轮缘/轨距面摩擦控制方式,严格控制摩擦材料喷涂量使两接触面不相互干扰,优化改进轮轨接触界面摩擦管理的最佳应用参数;应研发环境友好型的轮缘/轨距面润滑剂与车轮踏面/轨顶面摩擦控制剂,稳定调控轮轨接触界面的黏着特性。     

Fretting wear behavior of nanocrystalline surface layer of pure copper under oil lubrication

Lubricated fretting tests in mineral oil were performed with a nanocrystalline surface layer on a pure bulk Cu prepared by surface mechanical attrition treatment (SMAT) against a WC-Co ball. It was found that the nanocrystalline surface layer exhibited a markedly enhanced fretting wear resistance and higher friction coefficient relative to the coarse-grained (CG) form. The wear volume of the SMAT Cu is one order of magnitude lower than that of the CG Cu. The friction coefficient of the SMAT Cu increases with an increasing load and frequency, while for the CG Cu, the friction coefficient increases with an increasing fretting frequency up to 100 Hz and thereafter decreases. The higher hardness of the SMAT Cu is suggested to be the main factor causing its improved wear resistance and higher friction coefficient. A discontinuous metal transfer layer can be found on the WC-Co ball only after fretting against the SMAT Cu, which may partly account for the higher wear resistance of the SMAT Cu in comparison with the CG Cu.     

Effect of electrical current on the tribological behavior of the Cu-WS2-G composites in air and vacuum

As the traditional graphite-based composites cannot meet the requirement of rapid developing modern industry, novel sliding electrical contact materials with high self-lubricating performance in multiple environments are eagerly required. Herein a copper-based composite with WS2 and graphite as solid lubricant are fabricated by powder metallurgy hot-pressed method. The friction and wear behaviors of the composites with and without current are investigated under the condition with sliding velocity of 10 m/s and normal load of 2.5N/cm 2 in both air and vacuum. Morphologies of the worn surfaces are observed by optical microscope and compositions of the lubricating films are analyzed by XPS. Surface profile curves and roughness of the worn surfaces are obtained by 2205 surface profiler. The results of wear tests show that the friction coefficient and wear volume loss of the composites with current are greater than that without current in both air and vacuum due to the adverse effects of electrical current which damaged the lubricating film partially and roughed the worn surfaces. XPS results demonstrate that the lubricating film formed in air is composed of oxides of Cu, WS2 , elemental S and graphite, while the lubricating film formed in vacuum is composed of Cu, WS2 and graphite. Because of the synergetic lubricating action of oxides of Cu, WS2 and graphite, the composites show low friction coefficient and wear volume loss in air condition. Owing to the fact that graphite loses its lubricity which makes WS2 become the only lubricant, severe adhesive and abrasive wear occur and result in a high value of wear rate in vacuum condition. The formation of the lubricating film on the contact interface between the brush and ring is one of the factors which can greatly affect the wear performance of the brushes. The low contact voltage drop of the composites in vacuum condition is attributed to the high content of Cu in the surface film. This study fabricated a kind of new sliding electrical contact self-lubricating composite with dual-lubricant which can work well in both air and vacuum environments and provides a comprehensive analysis on the lubrication mechanisms of the composite.     

柱塞泵配流副滑摩界面摩擦磨损及热力耦合分析

针对轴向柱塞泵配流副滑摩过程中由摩擦温升所引起的摩擦磨损问题,建立配流副轴对称非稳态热传导方程,利用ABAQUS有限元软件进行配流副摩擦磨损及热力耦合特性分析,并利用端面摩擦磨损试验机进行试验验证。结果表明:在滑摩初期,相比于中低压力,高压力工况更易发生磨粒磨损;随着滑摩进行,材料表面粗糙峰被磨平,加之温度上升,材料强度下降,高转速取代高压力成为接触面温度和摩擦系数增大的主要影响因素,此时的磨损机制主要为黏着磨损;在滑摩过程中,外径出现了应力集中现象,且接触压力高于内径;转速及压力对配流副摩擦温升及磨损特性的影响是非线性的,在相同PV值下,转速比压力的影响更为显著。     

表面粗糙度对滑动电接触磨损率的影响

在电气化铁路弓网系统中,磨损率是衡量列车运行状态与接触导线使用状态的重要指标。为了充分模拟弓网系统中磨损率情况,利用自行搭建的滑动电接触摩擦磨损试验机对滑板和接触导线进行摩擦磨损试验,分析滑板表面粗糙度、法向压力、接触电流与运行速度对磨损率的影响。得出结论:滑板磨损率随滑板初始表面粗糙度、接触电流、法向压力、运行速度的增加而增加,而高载荷下粗糙度对于磨损率的影响降低;滑板摩擦从磨合期进入稳定摩擦期存在一个临界表面粗糙度,当滑板初始表面粗糙度值等于临界粗糙度值时,其磨损率最低;不同初始表面粗糙度的滑板在跑合期内磨损过程不同,在稳定摩擦期内磨损过程趋于一致,且摩擦试验后滑板表面粗糙度也接近。     

油溶性CuO纳米颗粒的抗磨性能研究

利用四球摩擦磨损实验机考察了油酸铜修饰CuO纳米颗粒作为润滑油添加剂的抗磨性能,并用扫描电子显微镜（SEM）和X-射线光电子能谱（XPS）等对钢球磨损表面进行了分析。摩擦磨损试验结果表明,当添加质量分数仅为0.025%时,油酸铜修饰CuO纳米颗粒作为润滑油添加剂即能够明显提高基础油的抗磨能力。SEM及XPS分析结果表明,油酸铜修饰CuO纳米颗粒作为润滑油添加剂在摩擦过程中形成了一层富含Cu2O和Fe2O3的化学反应膜,正是这层膜的存在使得其表现出良好的抗磨性能。     

Friction and wear of CuZn alloys against stainless steel

The friction and wear of CuZn alloys containing 8–57% Zn against an 18% Cr stainless-steel disc were studied by electron microscopy and Auger electron spectroscopy. The behavior of Zn in the surface played an important role in controlling the wear and friction properties of the alloys. With increasing zinc oxide the coefficient of friction decreased but the wear rate increased.Information is given about the concentration changes of Zn in the α-,β- and γ-phases with frictional contact and the changes are discussed in relation to the diffusion rate of Zn in the matrix.