制动条件下石墨对铜基摩擦材料瞬时摩擦性能的影响

为研究石墨对铜基摩擦材料瞬时摩擦性能的影响,采用粉末冶金技术制备铜-SiO2和铜-石墨-SiO2烧结材料,通过干摩擦惯性试验,在始末速度不同的制动区间,测试材料的瞬时摩擦因数、瞬时磨损率,并观察摩擦表面形貌的变化。结果表明:在高速度制动区间,石墨的存在使得铜基摩擦材料摩擦因数的稳定性明显提高,磨损率降低,原因在于铜-石墨-SiO2材料剥落石墨颗粒的分隔和保护作用,减弱冲击波动,从而提高瞬时摩擦因数稳定性并降低磨损;但较低制动速度时,石墨的存在反而提高了磨损率,原因在于摩擦层对颗粒的包裹度和基体强度降低。     

磁场条件下钢轨材料的摩擦磨损性能试验研究

基于HSR-2M高速往复摩擦磨损试验机,试验研究在永磁体磁场条件下,法向载荷、往复速度等参数对钢轨材料摩擦性能的影响,通过磨痕形貌分析其磨损机制,并与无磁场条件下的结果进行对比。试验结果表明:磁场的引入可以在一定程度上减小钢轨材料的摩擦因数、磨损率;增大滑动速度对摩擦因数和磨损率均有减小作用,增大载荷能够降低摩擦因数,但磨损率增加;磁场能够提高钢轨材料在摩擦过程中的磨损性能。无磁场时,钢轨材料磨损形式为典型的磨粒磨损,摩擦系统的磨损率和摩擦因数较大;有磁场时,磨损形式主要为黏着磨损,摩擦因数和磨损率较小。     

不同条件下SA533Gr.B合金钢与石墨摩擦副的摩擦磨损性能

分别将石墨化度和抗压强度不同的2种石墨与SA533 Gr.B合金钢组成摩擦副，用环块摩擦试验机测试不同润滑方式下的摩擦磨损性能，对磨损形貌进行观察。结果表明：在干摩擦稳定阶段，合金钢与石墨化度高且抗压强度低的石墨配副时摩擦副的摩擦因数大于与石墨化度低且抗压强度高的石墨配副，同时石墨化度低且抗压强度高的石墨的磨损率较低；在硼酸溶液中湿摩擦条件下，合金钢与不同石墨配副时摩擦副的摩擦因数差异不大，呈波动变化趋势，石墨的磨损率均高于干摩擦条件下；在剪切应力下，石墨化度低且抗压强度高的石墨在合金钢表面形成的转移膜较薄，且与钢基体结合紧密；石墨在干摩擦和硼酸溶液中湿摩擦条件下的磨损机制均以磨粒磨损为主。     

钢纤维和氧化铁粉含量对半金属摩擦材料摩擦磨损性能的影响

半金属摩擦材料中的钢纤维、氧化铁粉是重要的增强组分和调节剂。研究钢纤维含量和氧化铁粉含量对半金属摩擦材料摩擦磨损性能的影响,以获得较佳的配比。研究结果表明:随钢纤维含量增加,摩擦因数增加,且摩擦因数的稳定性和抗热衰退能力提高;但随钢纤维含量的增加,磨损率也随之增加;当钢纤维质量分数为20%时,摩擦材料的摩擦因数较平稳,350℃时几乎没有明显的热衰退,磨损率也较低。氧化铁粉的含量对摩擦因数影响不大,但可改善摩擦材料的自润滑性和抗高温热衰退性;但过多的氧化铁粉含量,导致磨损率增大,特别是高温时更为明显,从摩擦因数的稳定性与磨损率两方面综合考虑,氧化铁粉质量分数为5%时摩擦材料具有较好的摩擦磨损性能。     

纤维状坡缕石等混合增强酚醛树脂基制动摩擦材料的制备

选用纤维状坡缕石、针状硅灰石、Kevlar纤维、钢纤维混杂作为增强组分,制备出酚醛树脂基制动摩擦材料,对其摩擦因数、磨损率和冲击强度等进行了研究。结果表明：该材料摩擦因数适宜,一般保持在0．35～0．50之间,且随温度的变化波动较小;其耐磨性能较好,特别是在高温条件下磨损率小;其冲击强度满足国标GBn257—1986的要求。     

自润滑Cu-10Mn-10Al/石墨复合材料的摩擦磨损性能研究

采用粉末冶金技术,以石墨作为固体润滑组元制备Cu-10Mn-10Al/石墨复合材料,研究不同石墨含量下该材料的组织结构、摩擦磨损性能。结果表明:在烧结过程中,部分石墨会形成连续网状,其余部分则相互聚集形成片状整体。随着石墨含量的增加,材料的密度降低,孔隙度先增大后保持不变;同时摩擦因数和磨损率随石墨含量增加呈现先迅速降低后缓慢增加的趋势,在石墨含量为1%时,材料的摩擦因数和磨损率最小。     

纤维取向对飞龙材料摩擦磨损行为的影响

在MRH-03型环-块摩擦试验机上,在不同转速、载荷下对不同纤维取向的"飞龙"材料以及饱和吸水后的材料在纯水和人工海水下的摩擦性能进行研究。结果表明:不同纤维取向的"飞龙"材料具有不同的摩擦特性,摩擦方向垂直于单张纤维布时摩擦因数最大,而磨损率最低,摩擦位于单张纤维布上时摩擦因数最小而磨损率最大;随着转速增加,摩擦因数和磨损率均有所降低;随着载荷增加,纯水润滑时磨损率增大,海水润滑时磨损率无明显变化;饱和吸水后,材料的摩擦因数和磨损率,纯水润滑条件下降低,海水润滑条件下增大。SEM形貌分析表明,飞龙材料的磨损行为受到纤维对基体材料的支撑作用和基体材料对纤维的保护作用协同影响。     

减摩剂及其协同效应对树脂基摩擦材料性能影响

采用焦炭、MoS₂和石墨作为减摩剂制备树脂基摩擦材料,通过正交试验和极差分析法,研究3种减摩剂对材料摩擦磨损性能的影响及其协同作用规律。结果表明:在实验用量范围内,焦炭能够提高材料整体摩擦因数,降低材料总磨损率;MoS₂能够降低材料中低温摩擦因数,提高高温摩擦因数,但材料的总磨损上升;石墨能够降低材料整体摩擦因数,对材料总磨损率影响不明显。以材料摩擦因数标准差为实验指标时,发现3种减摩剂之间存在强烈的协同作用,且作用程度随着温度的升高而加强,其中焦炭和石墨的协同作用最为强烈;以材料总磨损率为实验指标时,发现3种减摩剂之间的协同作用在中低温下变化趋势一致,在高温下变化趋势不同。     

锡对粉末冶金铜基摩擦材料摩擦磨损性能的影响

采用粉末冶金的方法制备铜基摩擦材料,利用GF150D型定速摩擦试验机,研究摩擦速度为200~3 000 r/min、制动压力为0.38~0.63 MPa条件下,锡的质量分数在0~14%范围内材料的摩擦学行为。结果表明,材料中添加锡可明显提高材料的摩擦因数,其中锡质量分数为12%左右时材料的摩擦因数达到最高值,这是因为低锡含量时材料的强度不高使摩擦因数偏低,而锡含量过高时润滑作用增强,导致材料的摩擦因数降低;锡的质量分数在8%~12%范围对降低高速摩擦条件下的磨损率作用明显,这缘于合理的锡含量提高了材料的强度使材料的耐磨性提高;在低摩擦速度下,摩擦因数随着制动压力的增加而增加,而在高摩擦速度下,摩擦因数随压力增加而降低;在高速高压摩擦中,由于摩擦温度高以及第三体数量和基体软化程度与流动性的增加,导致摩擦因数降低。     

钢/铜混杂纤维增强摩擦材料摩擦学性能研究

以丁腈橡胶改性酚醛树脂为树脂基体,钢纤维-铜纤维混杂纤维作为变量,经热压烧结制备一种摩擦材料,在干摩擦条件下通过摩擦磨损试验机考察其摩擦学性能,并用扫描电镜(SEM)对摩擦材料的表面磨损微观形貌进行观察分析,以研究钢/铜纤维混杂对摩擦材料摩擦学性能的影响。实验表明:随滑动速率的增大,材料的摩擦系数、磨损率呈现减小趋势;轻载时,材料的摩擦系数、磨损率较高,重载时,摩擦系数、磨损率则相对较低。摩擦过程中,添加钢/铜混杂纤维的材料磨损形式为塑性变形和磨粒磨损;未添加混杂纤维的材料磨损形式主要为粘着磨损。由此可见,钢/铜混杂纤维的加入可以有效提高材料的摩擦系数,降低其磨损率,明显改善材料的摩擦学性能。     

Anisotrpic friction behavior of charcoal and the influence of humidity

Tribo-tests were carried out on pyrolyted wood derived charcoal specimen in the directions of “flat-face” and “curved-face”. In former direction, an ultra-low friction coefficient 0.03 was measured in a high humid condition with 75% relative humidity. Eventually, the friction coefficient becomes 0.45 when the humidity level decreased to 10%. However, under similar tribo-test condition, the friction coefficient is high 0.1 in the “curved-face” of charcoal specimen at 75% humidity. This value further increased to 0.8 at humidity level of 10%. Large amount of polar functional groups, oxygen complexes and water molecules was observed on the “flat-face” due to the presence of microscopic pores which act as a reservoir to lubricate the sliding surfaces.     

Sb2S3和MoS2的协同作用对摩擦材料摩擦性能的影响

采用MPX-2000型磨损试验机和定速摩擦实验机分别测试不同载荷及不同温度下固体润滑剂Sb2 S3和MOS2对摩擦材料摩擦性能的影响,探讨2种固体润滑剂的协同作用;采用扫描电镜分析摩擦材料磨损后摩擦表面的微观形貌.结果表明,固体润滑剂Sb2 S3和MoS2具有良好的协同效应,可大大改善摩擦材料的摩擦性能,这是因为MOS2和Sb2 S3分别在制动过程中的低温段和高温段起到良好的润滑作用.当Sb2S3的体积分数为6%,MoS2的体积分数为3%时,摩擦材料的摩擦性能最佳.     

多因素影响的格莱圈材料摩擦磨损试验研究*

格莱圈由聚四氟乙烯(PTFE)矩形滑环和丁腈橡胶(NBR)O形圈组成。为了研究不同因素对于格莱圈密封材料摩擦磨损性能的影响,利用UMT-3多功能摩擦磨损试验机,通过改变往复频率、粗糙度、润滑状态研究格莱圈材料与45钢配副时的摩擦磨损性能,利用SEM对试块试验前后表面形貌进行观测,并对摩擦磨损机制进行分析。试验结果表明:在干摩擦和滴油润滑条件下PTFE材料相比NBR材料具有更为优异的摩擦磨损性能;NBR材料表面粗糙度过高或过低都会导致摩擦因数升高,表面粗糙度对具有自润滑性能的PTFE材料的摩擦因数影响不大;高往复频率会使NBR材料摩擦因数降低,过高或过低的往复频率都会使PTFE材料摩擦因数降低;NBR材料的磨损形式以磨粒磨损和黏着磨损为主,PTFE材料以黏着磨损和疲劳磨损为主。     

Structural investigations on green culms and charcoal of Bambusa multiplex

Green culms of Bambusa multiplex and the bamboo charcoal carbonized from the green culms at 700°C have been studied by means of X‐ray diffraction, X‐ray fluorescent element analysis, analytical scanning electron microscopy, and analytical scanning transmission electron microscopy (STEM), aiming at industrial applications as raw materials for functional devices and substances. It is revealed that the green culms and the charcoal contain a significant amount of Si, in particular, ～18 wt % in the skin. The green culms comprise amorphous and crystalline celluloses. The charcoal has a so‐called amorphous structure which is composed of randomly distributed carbon nanotubes and fibers. The growth of Ag‐doped activated charcoal powders that were produced by two different methods using this charcoal powder has also been studied.     

Friction Behavior of Human Skin Rubbing against Different Textured Polymeric Materials Obtained by a 3D Printing Microfabrication Technique

Understanding friction behavior of human skin is indispensable in order to optimize surfaces and materials in contact with the skin. The coefficient of friction (COF) for different materials contacting against the skin is mainly influenced by the nature of the materials, mechanical contact parameters, and physiological skin conditions. The aim of the present research work was to study the grip effect of two different polymeric materials by producing different textured patterns using a 3D printing microfabrication technique and a replication technique. It was found that under the same contact conditions, a difference in the friction amplitude exists between the two different polymeric materials and that positive texturing, which consists of high relief or protrusions, showed higher COFs than negative texturing, consisting of low relief, holes, or dimples, which showed a decrease in friction as the textured pattern area density increased.     

惯性制动条件对铜-石墨材料摩擦性能及第三体的影响

采用粉末冶金技术制备铜-10%石墨烧结材料,通过GF150D型摩擦试验机,在干摩擦状态及制动压力为0.51 MPa的条件下,研究不同制动方式对材料摩擦磨损性能的影响。结果表明,采用从高速到低速分段制动方式(摩擦方式A)时,随着制动速度降低,摩擦表面形成的致密第三体破碎、剥落,机械啮合力增加,摩擦因数提高;同时,摩擦表面温度下降,基体强度提高,磨损率降低。采用从高速到低速连续制动方式(摩擦方式B)的摩擦因数和磨损量均大于摩擦方式A。     

The effect of gamma radiation on the tribological behavior of polyethylene terephthalate-based antifrictional material

Tribological behavior and strength characteristics of radiated polyethylene terephthalate materials filled by fine dispersed graphite and polytetrafluoroethylene powders are studied. The composite material treated by 150 kGr-dosed gamma radiation shows a low coefficient of friction and high wear resistance. It is recommended for usage as antifrictional material in friction units operating under increased radiation.     

Testing of metal-fluoroplastic sheet antifriction materials at up to 3 mps sliding velocities

The results of comparative tribotests of DU materials and developed netted sheet antifriction polytetrafluoroethylene-based materials during dry friction against a steel counterbody are discussed. It is shown that the netted sheet antifriction material is capable of long operation under the aforementioned conditions at up to 3 mps sliding velocities. IR spectroscopy and thermogravimetry of wear debris show a great amount of low-melting polytetrafluoroethylene destruction products that cause a decrease in friction temperature after the specimen run-in. The sheet material having a low wear rate, designed for operation in dry friction at high sliding velocities, can only be produced with a large volumetric share of polytetrafluoroethylene, which is the main condition for the formation of the antifriction layer. The Sharpy rule for sheet material friction at low wear rate is observed when the share of solid inclusions on the friction surface, the bronze frame in our case, is an order of magnitude lower that that of the softer and pliant matrix.     

On the nature of tribological contact in automotive brakes

The tribological contact in automotive brakes involves dry sliding contact at high speeds and high contact forces. The commonly used organic binder-type brake pad friction materials are extremely inhomogeneous and exhibit very low bulk strengths. Despite the low strength, the specific contact surfaces that form during the use render the pads very good friction and wear characteristics. This paper gives a general view of the contact situation of organic binder brake friction materials against cast iron discs, with special emphasis on many mechanisms for contact surface variations and the corresponding variations of the coefficient of friction.