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1.
This article deals with the rubber-based friction materials (RBFMs) which can be used in brake system. The physico-mechanical
and tribological properties of a series of fiber filled RBFMs containing steel wool and aramid pulp at different concentrations
along with a fiber-free reference material were characterized. Rubber–glass transition induced at higher sliding velocities
was identified based on the friction fade behavior of the RBFMs. The rubber–glass transition which is inherently originated
by viscoelastic response of polymeric binder was found to be influential on the tribological properties of the RBFMs. It was
revealed that steel wool increased coefficient of friction (COF) and improved friction recovery behavior at low volume percent
(7.5 vol.%) but it aggravated the COF at high concentration of steel wool (15 vol.%) and severe sliding conditions because
of harsh abrasive mechanism. Aramid pulp improved the fade behavior at high sliding velocities and increased COF due to formation
of sticky contact patches. It was revealed that steel wool increased the wear rate while aramid pulp did not affect the wear
rate significantly, contrary to the increase in the friction coefficient of RBFM. SEM analysis was proved to be useful in
correlating the wear rates of composites to the topographical changes on the worn surfaces. 相似文献
2.
Yasushi Kojima Masayuki Shima Tomohiro Motoda Tatsuhiro Jibiki Takashi Sugawara 《Tribology International》2007,40(10-12):1479
The paper describes a method for estimating the coefficient of friction (COF) between sliding surfaces by an indentation of an acute-angled indenter. The COF estimated by the method is compared with the COF measured by a friction tester. The conical indenter, which is made of WC and has an apex angle of 45°, is used for the experiments. A micro-Vickers hardness tester is used for the indentation tests. The friction tester used is one of Bowden–Leben type. A copper and a 0.45% carbon steel are used for the indentation and sliding specimens. The estimation of the COF is based on the equilibrium equation of indentation, which takes the friction between the contacting surfaces of the indenter and the specimen into consideration. The results show that the estimated COF is approximately equal to the measured one. Based on the results, the validity of this method is discussed. 相似文献
3.
A study was made of the friction of nylon fiber (monofilament fishing line) rubbing against spinning aluminum and nylon capstans (cylinders), in the presence of various lubricants. Use of variable speed drives with appropriate gear reducers allowed variation of sliding speed over four orders of magnitude and monitoring of the entire Stribeck curves, from boundary through mixed to hydrodynamic sliding, for these systems. The effects on friction of seven system variables—cylinder material, sliding speed, system elasticity, input tension, lubricant viscosity, lubricant additives and cylinder surface roughness—were investigated. Special attention was given to the effects of elasticity on friction and the character of sliding. Factors which determine the critical speed where stick–slip sliding just appears or disappears are defined. 相似文献
4.
This study investigated the effect of various parameters of the friction–velocity relationship on the friction-induced vibration of simulated instrument panel components. The effect of subsystem stiffness and damping on the system response was also studied. A simple discretized model was utilized with subsystem properties that were intended to realistically model values of low, medium, and high stiffness components. Specifically, the metric of mean squared velocity was used as an indicator of the noise generated during the stick–slip process. It was found that the difference between the static and the asymptotic kinetic value of friction was the most important friction parameter in determining the resulting behavior. As stiffness and damping are increased, the mean squared velocity decreases. Additionally, results from single excursion tests on a variety of instrument panel material pairs showed good correlation between mean squared velocity and the difference in static and kinetic friction. 相似文献
5.
We investigate the sliding dynamics of atomic-scale friction at different time scales. Depending on the dynamic inertia and sliding velocity of a cantilever, different dynamic behaviors are observed from both conventional molecular dynamics (MD) simulation and temporally hybrid molecular simulation methods. The mechanism of friction dissipation is also investigated. For either smooth sliding or stick–slip, a non-zero work of friction is obtained, while surface forces are no longer conservative. 相似文献
6.
Yingxi Zhu Hiroko Ohtani Michael L. Greenfield Marina Ruths Steve Granick 《Tribology Letters》2003,15(2):127-134
The molecular-level function of model and commercial friction modifier additives in lubricants of the type used at the wet clutch interface in automatic transmissions has been studied using a surface forces apparatus (SFA) modified for oscillatory shear. The nanorheological properties of tetradecane with and without a model friction modifier additive (1-hexadecylamine) were examined in the boundary lubrication regime and compared to a fully-formulated automatic transmission fluid (ATF). 1-Hexadecylamine adsorbed as a single layer on the sliding surfaces, reduced the static frictional force and the limiting shear stress, and eliminated the stick–slip transition that exists in pure tetradecane. The ATF, which contains commercial-grade friction modifiers, showed nanorheological properties similar to those observed for tetradecane containing 0.1–0.2 wt% 1-hexadecylamine. 相似文献
7.
A high-temperature ball-on-flat tribometer was used to investigate dry and oil-lubricated friction and wear of sintered Si3N4 and Si3N4/hexagonal boron nitride (H-BN) fibrous monoliths. The friction coefficients of base Si3N4 flats sliding against Si3N4 balls were in the range of 0.6–0.8 for dry and 0.03–0.15 for lubricated sliding, and the average wear rates of Si3N4 were 10–5 mm3 N–1 m–1 for dry sliding and 10–10–10–8 mm3 N –1m–1 for lubricated sliding. The friction coefficients of Si3N4 balls against composite fibrous monoliths were 0.7 for dry sliding and 0.01–0.08 for lubricated sliding. The average specific wear rates of the pairs were of the same order as those measured for the conventional Si3N4 pairs. However, the fibrous monoliths, in combination with sprayed dry boron nitride, resulted in reduction in the lubricated friction coefficients of the test pairs and significant reduction in their wear rates. The most striking result of this study was that the coefficients of friction of the Si3N4/H-BN fibrous monolith test pair were 70–80 lower than those of either roughened or polished Si3N4 when tests were performed under oil-lubricated sliding conditions over long distances (up to 5000 m). The results indicated that Si3N4/H-BN fibrous monoliths have good wear resistance and can be used to reduce friction under lubricated sliding conditions. 相似文献
8.
Hot wear properties of ceramic and basalt fiber reinforced hybrid friction materials 总被引:3,自引:0,他引:3
In the present study, hybrid friction materials were manufactured using ceramic and basalt fibers. Ceramic fiber content was kept constant at 10 vol% and basalt fiber content was changed between 0 to 40 vol%. Mechanical properties and friction and wear characteristics of friction materials were determined using a pin-on-disc type apparatus against a cast iron counterface in the sliding speeds of 3.2–12.8 m/s, disc temperature of 100–350 °C and applied loads of 312.5–625 N. The worn surfaces of the specimens were examined by SEM. Experiments show that fiber content has a significant influence on the mechanical and tribological properties of the composites. The friction coefficient of the hybrid friction materials was increased with increasing additional basalt fiber content. But the specific wear rates of the composites decreased up to 30 vol% fiber content and then increased again above this value. The wear tests showed that the coefficient of friction decreases with increasing load and speed but increases with increasing disc temperature up to 300 °C. The most important factor effecting wear rate was the disc temperature followed by sliding speed. The materials showing higher specific wear rates gave relatively coarser wear particles. XRD studies showed that Fe and Fe2O3 were present in wear debris at severe wear conditions which is indicating the disc wear. 相似文献
9.
Friction-induced vibration of oscillating multi-degree of freedom polymeric sliding systems 总被引:1,自引:0,他引:1
The purpose of this study is to investigate friction-induced vibration of oscillating systems. Special attention is focused on modeling polymer-on-metal systems. Past experimental and analytical friction results from non-oscillating or unidirectional translational sliding modes are extended into the oscillating sliding mode. Specifically, this refers to the incorporation of a representative functional shape of the friction–velocity relationships estimated from experimental results. Dependent on the relative sliding velocity between the frictionally coupled subsystems, the modeled system exhibits behavior such as a single stick–slip at the beginning of oscillatory motion, a single stick–slip at each motion reversal, or multiple stick-slip events during each half cycle of motion. Additionally, the boundary of incipient friction-induced vibration was identified via a rigorous definition of friction-induced vibration. 相似文献
10.
The accuracy of nanopositioning is to a large extent limited by the friction-caused errors, particularly in vacuum environments. An investigation of the friction behaviour of sp2-bonds dominating diamond like carbon (DLC) coatings and WC1−x/DLC, WC(N)/DLC multilayer coatings, which are considered to be used in nanopositioning in vacuum, have been performed by a vacuum microtribometer. By using an atomically smooth Si sphere as a counterface, the reciprocating sliding friction was measured at a normal load <5 mN, and running speed at a 1–100 μm/s in ambient air and in ultra high vacuum (UHV) at 10−7 Pa, and correlated with microstructures and properties of the coatings. When tested in UHV, the coefficient of friction (COF) for pure DLC coatings (thickness: 700 nm) changes significantly between 0.2 and 0.4. Once the thickness of DLC layers is limited to 5 nm by formation of multilayer coatings, the COF in UHV decreases by nearly one order to 0.02–0.05. We suggest that the deformation of DLC films and the transfer films determines COF. Thick DLC coatings can induce more plastic deformation and consumes more energy in sliding resulting in a high COF. Thickening of the transfer film in running leads to a continuous decrease of COF since the deformation of the transfer films turns easier. The low COF of multilayer coatings is mainly due to their confinement of the thickness of DLC films. A consistent velocity-strengthening frictional behaviour of both WC1−x/DLC and WC(N)/DLC coatings in UHV indicates that the transfer films acting as a thin layer of granular material. Further study of the friction behaviour with the presence of such granular materials might be interesting for the further development of tribological coatings for vacuum applications. 相似文献
11.
Atomic-scale friction between self-assembled monolayers (SAMs) on Au (1 1 1) has been studied through molecular dynamics simulations, with emphasis on the mechanism of energy dissipation. Results show that the shear stress and chain angle on commensurate SAMs exhibit a clean periodic pattern and atomic stick–slip friction, which manifests a gradual storage and sudden release of energy. Using a simple model of two atoms, analysis shows that the atomic stick–slip originates from the dynamic instability of molecule motion. Energy has been built up during the stick, followed by a sudden separation as the equilibrium becomes unstable, and most energy dissipates at the time of slip. Moreover, the simulations reveal that more energy is stored and released in commensurate sliding, resulting in much higher friction than that in incommensurate cases. The contradictory frictional behavior can be traced to the difference in the number and strength of the Van der Waals bonds, formed in the two types of contacts. 相似文献
12.
The present contribution reports the tribological properties of Ni–WC composite coatings, electrodeposited on steel substrate. Commercial WC particles with an average size of 5 μm were codeposited with Ni on a mild steel substrate using a Watts bath at 50°C. The effect of plating variables on deposition behavior was studied. The amount of WC in the deposited layer decreased and plating efficiency increased with an increase in current density from 0.1 to 0.3 A/cm2. The tribological properties of the coatings were studied using a small amplitude reciprocating friction wear tester. The addition of WC in Ni increases the microhardness of the electrodeposited coatings. An important result is that the presence of embedded WC particles in the electrodeposited coatings results in a much lower coefficient of friction (COF) of 0.34, when compared with pure Ni (COF 0.62) and mild steel (COF 0.54). 相似文献
13.
Chii-Rong Yang Associate Researcher Yuang-Cherng Chiou Professor Rong-Tsong Lee Professor 《Tribology International》1999,32(8):443
The dynamic friction and wear behaviors are investigated in reciprocating friction drive system using a 0.45% carbon steel pair. The effects of various operating parameters on the traction force, stick and slip time, and friction modes are examined under the lubricated contacts. Moreover, the critical operating conditions in classifying three friction modes are also established. Results show that the fluid friction induced by the shearing of lubricant dominates the variation of traction force and produces the positive slope γ at the first period of slip in the traction force–relative sliding velocity curve. The γ value decreases at higher driver speed during stick-slip motion due to the thicker fluid film and shear thinning effect. The γ value increases due to the asperity interactions as the friction region is transferred from stick-slip to sticking with normal load from 196 to 980 N. Furthermore, it is also found that the static friction force is independent of stick time for the tangential loading rate ranged from 1.12 to 16.8 s−1. The transition region produces the severest wear under the different driver speeds, but the wear is insensitive to the friction regions and the severe wear only occurs at higher normal load due to the action of Hertzian contact. 相似文献
14.
15.
A static friction model for contact between rough rubber and metal surfaces is developed. This model is based on the contact of a viscoelastic–rigid asperity couple. Single asperity contact is modelled in such a way that the asperities stick together in a central region and slip over an annulus at the edge of the contact. The slip area increases with increasing tangential load. Consequently, the static friction force is the force when the slip area is equal to the contact area. Using the model, the traction distributions, contact area, tangential and normal displacement of two contacting asperities are calculated. The single asperity model is then extended to multi-asperity contact, suitable for rough surfaces. This model allows calculation of the above-mentioned parameters for two rough surfaces (a rubber and a metal one) subjected to normal and tangential loads. A parametric study will be presented. The results are qualitatively in good agreement with those found in literature. 相似文献
16.
Tribological studies were performed on the friction and wear behaviour of polymers under conditions of dry sliding. The investigations were carried out with thermoplastics suitable for practical applications, eg HDPE, PP, PTFE, PA 6, PA 66, POM, PETP, PBTP, PI, as well as with some filled and reinforced polymers and composite materials. For polymer-polymer sliding pairs, the experimentally determined friction values could be related to the surface energies of the material pairings. In the case of polymer-metal sliding pairs, a relationship between the combined interfacial stresses and the rupture strength of the polymers was found. In addition to the review of correlations between the tribological behaviour of thermoplastics and material properties, the dependency of wear and friction on surface roughness, sliding velocity and contact pressure for various filled polymers is described. 相似文献
17.
Experimental determination of the frictional properties of a microsized fiber wrapped around a cylinder has been of long-standing interest to the academic community. The purpose of the current experiments was to explore the diameter dependence of such microsized fibers in nonlubricated friction using a highly accurate tribometer. For this work, NbTi superconducting material was used for the fibers and polyvinyl chloride (PVC) was used as the cylinder material. Significant effects were observed in the kinetic friction coefficient for different fiber diameters, normal forces, and sliding speeds. Moreover, the effects of fiber diameter on the frictional stability were measured. Smaller fiber diameters and low sliding speeds both produced poor frictional stability. The most likely explanation for the observed stick–slip phenomena is hypothesized to be a combination of creep mechanics and plastic deformation of the junctions on the contacting surfaces. 相似文献
18.
高载荷条件下石墨-石墨摩擦副的摩擦学特性研究 总被引:1,自引:0,他引:1
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。 相似文献
19.
Ag膜在干摩擦、油和脂润滑下的摩擦学性能研究 总被引:1,自引:0,他引:1
精密运转部件表面沉积一层软金属银和银基固体薄膜可以有效地降低摩擦、减小磨损。通过钢球/镀Ag膜摩擦盘在干摩擦、4122油和L252脂润滑条件下的球-盘摩擦学试验,研究Ag膜在油和脂复合润滑下的摩擦学性能,分析润滑条件、载荷、速度对Ag膜摩擦因数的影响。试验结果表明:在4 N法向载荷和油、脂润滑下,与干摩擦相比,镀Ag膜摩擦副的最大静摩擦因数分别减小了10.7%和6.1%;在0~2 000 r/min转速范围内,Ag膜摩擦因数随转速增加而减小,与干摩擦相比,油润滑下Ag膜摩擦因数减小9%~48%,脂润滑下Ag膜摩擦因数减小17%~52%。Ag膜在干摩擦、4122润滑油和L252润滑脂复合润滑下,摩擦因数均随载荷增加而降低;Ag膜摩擦副/钢球在油、脂复合润滑下启动摩擦力矩小,摩擦副在宽转速范围内摩擦因数变化小,运转平稳。 相似文献
20.
Influence of Ultrasonic In-Plane Oscillations on Static and Sliding Friction and Intrinsic Length Scale of Dry Friction Processes 总被引:1,自引:0,他引:1
The force of friction between plates of different materials (steel, brass, copper, titanium, glass, aluminum, rubber, and
Teflon, among others) and a steel sample oscillating in the sliding plane at a frequency of 40–70 kHz has been studied. The
measured friction coefficient as a function of sliding velocity and velocity oscillation amplitude fits well with theoretical
predictions based on the simple Coulomb friction law at sliding velocities larger than the actuation velocity. However, the
friction coefficient tends to a finite value at small sliding velocities, which is contrary to the theoretical prediction.
The static limit has been studied in detail. A strong decrease in the static friction force takes place at oscillation amplitudes
of 20–60 nm. Such amplitudes are enough to control the friction coefficient. The experimental data for both static and sliding
friction are interpreted within the framework of a microscopic model and a phenomenological macroscopic model. The notion
of intrinsic friction slip length is introduced. 相似文献