载流条件下铬青铜/纯铜摩擦副摩擦磨损性能研究

在自制的销盘摩擦磨损试验机上,对铬青铜/纯铜摩擦副进行载流条件下的干滑动模拟试验,研究了电流、速度、载荷对铬青铜/纯铜摩擦磨损性能的影响规律。试验结果表明:电流是影响摩擦副摩擦磨损性能最显著的因素,摩擦因数和磨损率都随着电流的增大而增大;速度和载荷对摩擦因数和磨损率也有显著影响;电流的存在,摩擦副间产生了比无电流时更严重的粘着磨损和塑性变形,同时增加了电化学腐蚀,使磨损更加严重。     

载流条件下铬青铜/3D碳/碳复合材料摩擦副的摩擦磨损性能

以3D碳/碳复合材料为销试样、铬青铜QCr0.5为盘试样进行了载流条件下的干滑动摩擦磨损试验。通过对有、无电流条件下销试样磨损量大小和摩擦因数影响度的比较,以及对销试样摩擦表面进行的微观形貌分析,结果表明,电流对铬青铜/3D碳/碳复合材料摩擦副的干摩擦行为具有显著的影响,并且由于电场、摩擦热、电弧热的共同作用,在销试样表层发生了磨粒磨损和氧化磨损。     

紫铜/铬青铜摩擦副在干摩擦和水雾条件下的载流摩擦磨损性能研究

在HST-100载流高速摩擦磨损试验机上,对比考察了紫铜/铬青铜摩擦副在干摩擦和水雾2种状态下的载流摩擦磨损性能,采用扫描电镜(SEM)对磨损表面形貌进行了观测。结果表明:水雾条件下销试样载流摩擦磨损时,其摩擦因数及磨损率均低于纯载流状态下;该试样在纯载流条件下的磨损机制主要为粘着磨损和电气磨损,在水雾条件下主要为电弧侵蚀、塑性变形和轻微的粘着磨损。这是因为水有利于降低摩擦副接触表面的温度,有效地抑制了铜的转移,阻止了粘着磨损的发生。水因素的介入也导致了电弧发生频率的增多,但在综合影响下,水可以有效地改善该试样的磨损性能。     

铜-二硫化钼粉末冶金材料的载流摩擦磨损性能研究

将MoS2粉末与铜粉、镍粉、铁粉、铅粉均匀混合后冷压并经880℃烧结,制备了Cu-10%MoS2和Cu-20%MoS22种销试样。以铬青铜QCr0.5为盘试样,采用自制的载流摩擦磨损试验机,研究了铜-二硫化钼粉末冶金材料的载流摩擦磨损性能。研究结果表明:在有电流条件下,加入MoS2可显著降低铜基粉末冶金/铬青铜配副的摩擦因数和铜基粉末冶金材料磨损率,10%和20%MoS2含量的粉末冶金试样的磨损率相差不显著,20%MoS2含量的摩擦因数在高速时有所增加。     

电流对黄铜/Al2O3弥散强化铜合金摩擦副摩擦磨损性能的影响

根据列车受电弓系统的实际工况条件,在自制的销-盘式载流摩擦磨损试验机上研究了Al2O3弥散强化铜合金销试样和黄铜（H62）盘试样摩擦副在载流条件下的滑动摩擦磨损性能,试验条件为速度20m/s、载荷0.63MPa、电流25-75A。试验结果表明,电流对黄铜/Al2O3弥散强化铜合金摩擦副的滑动干摩擦行为具有显著影响。随电流的增加,销试样的磨损率增加,摩擦因数增大,试样表层发生了磨粒磨损和粘着磨损。     

铜基粉末冶金材料/铬青铜摩擦副中的电弧侵蚀机制

以铜基粉末冶金材料/铬青铜为摩擦副,在销-盘式摩擦磨损试验机上进行载流摩擦学特性研究。在多种条件下试验,探讨载流条件下铜基粉末冶金/铬青铜摩擦副中的电弧侵蚀机制。结果表明:载流摩擦下销试样磨损形式主要以机械磨损、电流和机械综合作用下的磨损、电弧侵蚀为主;电弧对铜基粉末冶金材料的侵蚀主要是熔融材料的黏着磨损、磨粒磨损,电弧作用下材料表层的疏松化、材料的蒸发与转移、材料的熔融积瘤。     

铜基粉末冶金载流摩擦磨损微观形貌分析

对铜基粉末冶金材料进行载流摩擦磨损实验,对磨损后的微观组织进行了观察与分析.结果表明,铜基粉末冶金材料在载流条件下,销试样表面不断发生氧化,电流为40和60 A时,摩擦表面覆盖着一层Fe的氧化物;电流为80和100 A时试样由于表面温度更高,形成Cu的氧化物.产生氧化物的不同,电弧产生烧损的严重程度不同,是导致不同电流下磨损机制不同、磨损率相差大的原因.电流较大时电烧蚀严重,加快了磨损进程.     

铜基粉末冶金/铬青铜摩擦副载流摩擦磨损的电弧侵蚀特性研究

在销/盘式载流摩擦磨损试验机上,对铜基粉末冶金/铬青铜摩擦副载流摩擦磨损的电弧侵蚀特性进行了研究,探讨了电弧对铜基粉末冶金材料的载流摩擦学特性的影响.利用方差分析表,采用F检验法对电流、载荷、速度3种因素进行了显著性检验.结果显示电流对电弧能量的大小有影响,载荷、速度对电弧能量有显著影响;随着速度的增加,电弧的强度和发生频率均增大;低速下,主要是磨粒磨损和粘着磨损,高速下,主要是电弧侵蚀和粘着磨损.     

不同润状态下炭纤维对锡青铜摩擦磨损性能的影响

短碳纤维增强锡青铜（碳／锡青铜）复合材料分别在干摩擦和有油滑状态下与钢进行了滑动对磨试验，研究了试验条件及碳纤维含量等因素对复合材料摩擦磨损性能的影响。试验结果表明，碳纤维对锡青铜摩擦磨损性能的影响行为与润滑状态有关，干摩擦时碳纤维的加入可以明显提高锡青铜的摩擦磨损性能，而有油润滑时碳纤维对锡青铜的摩擦磨损性能不仅没有改善，还会带来损害。     

表面粗糙度对黄铜/铬青铜摩擦副载流摩擦磨损性能影响的研究

以黄铜/铬青铜为摩擦副,在销-盘式摩擦磨损试验机上进行了载流摩擦学特性研究,探讨了载流条件下摩擦副的表面粗糙度对摩擦学特性的影响.结果表明:摩擦副表面粗糙度存在一个最佳值,使质量磨损率最小,载流效率、载流稳定性也较好;摩擦因数先随表面粗糙度的降低而升高,当表面粗糙度降低到一定程度以后摩擦因数的变化趋于平稳.质量磨损率随着表面粗糙度的降低先减小后增大;载流导致质量磨损率增大,且随着电流密度的增大,这种影响更加显著.     

Influence of Cu Grain Size on Running-in Related Phenomena

We used a single-asperity microscopic tribosystem diamond sphere/Cu sheet to investigate the relevant phenomena affecting the dynamics of friction and wear in a macroscopic system. The influence of the average grain size of the softer of two tribopartners on friction and wear was investigated in particular. The observed tribosystem experienced a natural transition during the running time, from severe plastic flow to predominating boundary lubrication. This fact was used to study the influence of poly-α-olefine base oil and fully formulated engine oil Fuchs Titan SAE 5W45 on friction and wear during severe deformation and the boundary lubrication regime. It is shown that the initial grain size has a crucial influence on wear and friction only during first sliding interactions. During the initial sliding, the grain size rapidly decreases due to plastic deformation. The grains then become uniformly equal in size in every initial situation after approximately 30 cycles. Initially larger grains result in increased friction and wear as well as higher sensitivity to the kind of lubrication.     

Wear Behavior of Bronze Hybrid MMCs Coatings Produced by Current Sintering on Steel Substrates

In this work, a bronze matrix (90 wt% Cu + 10 wt% Sn) was reinforced with SiC and graphite particulates using mechanical alloying and a subsequent current sintering technique. The mechanically ball-milled bronze hybrid matrix composite powders reinforced with 5.0 wt% SiC and 5.0 wt% graphite were cold-compacted on a 1040 steel substrate under a pressure of 300 MPa. The compacted structure was sintered at atmospheric conditions to nearly a full density within 10 min using current sintering, in which the powders were heated by a low voltage and high current and compressed simultaneously. The samples were sintered at three different applied currents (1,500, 1,700, and 1,900 A) to provide dense and well-bonded coatings on steel substrates. Microhardness testing and optical and scanning electron microscopes (SEM) were used for microstructural characterization of the hybrid composites. The tribological characterization of the resulting composites was tested by a block-on-disk method for determination of the wear loss and friction coefficient behaviors against a steel disk. It was pointed out that increasing applied current during the sintering/coating process resulted in obtaining high-hardness and wear-resistant hybrid composite coatings.     

About Joint Deformations of Asperities and the Destruction of Rough Surfaces During Friction

The mechanics of the deformations and the destruction of the asperities of rough surfaces has been considered, taking into account the mutual influence of the elastic constants of the materials participating in the friction couple.

The case when the destruction is taking place inside of the contact layer is assumed to have the highest probability. The tight bear of the peaks of one body against the valleys of the other and the adhesion phenomena are leading to a mutual deformation of the prevailing number of asperities of both surfaces. This allows one to consider the contact layer as a composite body consisting of two solid phases and voids.

It has been shown that such an approach does not exclude the possibility of shearing off only the soft material of the couple.

For the asperities subject to bending deformations, the mutual influence of the elastic constants is conditioned by the mutual angle of rotation of the cross sections.

In this case consideration of the tangential stresses in the destruction of the short bars (asperities) is essential.     

Formation of Friction Layers in Graphene-Reinforced TiAl Matrix Self-Lubricating Composites

The friction layer structure has been proved to be formed during severe plastic deformation and markedly improves the tribological properties of material. The dry friction and wear performance of graphene-reinforced TiAl matrix self-lubricating composites (GTMSC) at different sliding velocities are systematically researched. GTMSC show the best tribological properties and special friction layer structure containing a wear-induced layer and a grain refinement layer with a nanocrystalline (NC) structure under surface after sliding at a sliding speed of 1.1 m/s. Nanoindentation results show that the grain refinement layer has a higher hardness and elastic modulus than the wear-induced layer. This special microstructure of friction layers beneath the surface after sliding leads to a low coefficient of friction and high wear resistance of GTMSC. Moreover, it is deduced that the appearance of an NC structure results in hardening of the material. The formation mechanisms of friction layers are researched in detail. It can be concluded that the formation of a wear-induced layer results from frictional heat and fracture of the counterpart. The formation of a grain refinement layer is due to severe plastic deformation and dynamic recrystallization. Severe plastic deformation results in the formation of an NC structure and dynamic recrystallization leads to grain refinement.     

Effects of NBR Particle Size on Performance of Carbon Fiber–Reinforced Paper-Based Friction Material

In the present work, three different sized nitrile–butadiene rubber (NBR) particles were used to modify carbon fiber–reinforced paper-based friction material (CFRPF). The effects of NBR particle size on performance of CFRPF were studied. The microstructure and properties of the samples were investigated by scanning electron microscopy, thermal analysis, and wet friction performance testing. Experimental results indicated that there were four stages in the thermal degradation of NBR-modified CFRPF. NBR particle size had a great effect on the first degradation stage (100–300°C). The highest friction coefficient was obtained with the sample containing the finest NBR particles. The wear rate of the friction materials decreased with an increase in NBR particle size. However, NBR particle size had little influence on the wear rate of the couple plate. The sample containing coarse NBR particles showed excellent friction stability under oil-lubricated conditions.     

改进微静电马达的摩擦与磨损

在微观结构中,摩擦及磨损严重地影响着部件的力学性能和可能性不同材料的摩擦系数相差很大,多晶硅和多晶硅之间的静摩擦系数约４．９,多晶硅和单晶硅之间的静摩擦系数约０．４８￣０．２８,动摩擦系数约０．３５￣０．２０,材料表面的粗糙度对摩擦系数影响也很大。鉴于此,提出了一种单晶硅台面结构晃动微马达,取代多同机械工艺制作的多晶硅法兰盘。它具有机械强度高、摩擦系数、抗磨损、不塌陷等优点,马达的轴也加工成实心轴     

Evaluation of fretting wear based on the frictional work and cyclic saturation concepts

It is time consuming or even impossible to simulate the whole process of fretting wear, since it always involves millions of cyclic loadings. This paper focuses on the modeling and evaluation method of fretting wear for the typical bridge type fretting test with a flat pad. The frictional work on the contact interface is chosen as the parameter to evaluate the fretting wear. To verify the fretting wear model, the predicted wear profile is compared with that obtained by the experimental results. Fretting wear always includes plastic deformations due to the edge stress singularity. The effect of cumulative plastic deformation is also taken into account in the wear model. The role of the coefficient of friction at the contact interface on the fretting wear has also been discussed.     

Hydrodynamic Behavior of Viscoelastic Liquids in a Simulated Journal Bearing

The hydrodynamic effect of viscoelasticity in bearing performance was investigated experimentally by measuring the pressure distribution of viscoelastic liquids and Newtonian liquids in a simulated plain journal bearing. The pressure distribution of the viscoelastic liquids was somewhat different from that of the Newtonian liquids, showing a flattening of the pressure profile and a shift of the circumferential position of the peak pressure. Such a difference contributes to a small recovery of the loss of the load-carrying capacity due to the non-Newtonian viscosity for viscoelastic liquids. It may also contribute to a further reduction of friction beyond the effect of shear thinning. The difference of cavitation on the divergent region of the bearing for these two different kinds of liquid was evident. The viscoelastic liquids showed less extent of cavitation. The experimental conditions conform closely to those used in the classical hydrodynamic lubrication theory. The experimental data indicate that the full fluid film occupies half a bearing starting at 0° and ending at 180°, and the subatmospheric pressure in the divergent region is leveled off at a certain negative pressure. Based on this boundary condition, a computer solution in solving the Reynolds equation for a finite bearing gives very good agreement with experiment.