Development of fly ash-based automotive brake lining

Coal-fired power plants all over the world generate huge amounts of fly ash each year, 70 million tons of which are produced in the United States alone. Only 40% of all fly ashes generated in the USA find beneficial applications and rest have to be disposed off, which is burden for the generation industry. Fly ash particles possess certain characteristics that make them suitable for use in friction composites as a filler material. An attempt has been made through this research to incorporate more than 50 wt% of fly ash particles in automotive brake lining friction composites. This paper presents the research carried out on development of friction composites, using fly ash obtained from a specific power plant in Illinois. Ingredients such as phenolic resin, aramid pulp, glass fiber, potassium titanate, graphite, aluminum fiber and copper powder were used in the composite development phase, in addition to the fly ash. The developed brake lining composites have exhibited consistent coefficients of friction in the range of 0.35–0.4, and wear rates lower than 12 wt%.     

Tribological study of gray cast iron with automotive brake linings: The effect of rotor microstructure

Experimental studies of friction characteristics were conducted using gray cast iron and automotive brake linings. The gray iron samples were manufactured to have different microstructures by changing the carbon equivalent and cooling speeds of melts and two different types of non-commercial brake linings (non-steel and steel-containing linings) were used as a counter material. Friction tests were performed on a pad-on-disk type tribotester and particular emphases were given to the effect of graphite flakes and ferrite in the gray iron disks on fade phenomena and the level of the coefficient of friction. Results showed that the coefficient of friction increased with the amount of graphite flakes on the gray iron and the effect was more pronounced in the case of using steel-containing linings. The amount of ferrite phase on the disk surface showed little influence on the coefficient of friction. Fade resistance of non-steel linings was improved with the increase of graphite flakes on the disk surface and steel-containing linings showed good fade resistance regardless of graphite contents in the gray iron disks.     

Tribological properties of some phenolic composites suggested for automotive brakes

Brake linings used in automotive disk brakes are usually made of various components such as phenolic resin, Cu powder, BaSO₄, Al₂O₃, etc. In this study, 20 specimens with different compositions of the components were manufactured and a pad-on-disc-type wear tester was used. Friction and wear characteristics of the specimens next to a disk made of cast iron were studied. In addition, micro-structural characterisation of braking pads was carried out using SEM and also the effect of temperature on behaviour of the pads was investigated at the temperatures of 50–400 °C and pressure of 1050 and 3000 kPa. Finally, the effect of environment on the pads was investigated in water, salty water, oil and braking liquid media.     

The effect of Al2O3 on the friction performance of automotive brake friction materials

This study consists of two stages. In the first stage, bronze-based break linings were produced and friction-wear properties of them were investigated. In the second stage, 0.5%, 1%, 2% and 4% alumina (Al₂O₃) powders were added to the bronze-based powders and Al₂O₃ reinforced bronze-based break linings were produced. Friction–wear properties of the Al₂O₃ reinforced samples were aslo investigated and compared to those of plain bronze-based ones. For this purpose, friction coefficient and wear behaviour of the samples were tested on the grey cast iron disc. The hardness and density of the samples were also determined. Microstructures of the samples before and after the sintering and the worn surfaces of the wear specimens were examined using a scanning electron microscope (SEM). The sample compacted at 350 MPa and sintered at 820 °C exhibited the optimum friction–wear behaviour. With increase in friction surface temperature, a reduction in the friction coefficient of the samples was observed. The lowest reduction in the friction coefficient with increasing temperature was for the 2% and 4% Al₂O₃ reinforced samples. The SEM images of the sample indicated that increase in Al₂O₃ content resulted in adhesive wear. With increase in Al₂O₃ content, a reduction in mass loss of the samples was also observed. Overall, the samples reinforced with 2% and 4% Al₂O₃ exhibited the best results.     

Friction and wear of sintered metallic brake linings on a C/C-SiC composite brake disc

The friction and wear of sintered metallic brake linings on a C/C-SiC composite brake disc were studied. This paper reports on the friction and wear properties of sintered metallic (MMC) brake linings, which appear to combine well with a C/C-SiC brake disc. The friction characteristics were examined with a dynamometer on two different commercial motorcycle brake systems, differing in terms of the brake caliper and the dimensions of the disc. The influence of the components, such as graphite, and the abrasives in the metallic matrix on the formation of the friction layer was investigated using a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The friction layer formed on the pad's sliding surface by oxidation wear, which consisted mostly of iron and copper oxides, was confirmed. The friction properties of the sintered metallic brake pads were determined and related to the composition and structure of the brake lining. This investigation of the friction characteristics of a brake couple comprising (MMC) brake linings and a C/C-SiC composite disc will increase our understanding of this material, which works in a completely different way to classical brakes based on metallic discs.     

Effects of ZrSiO4 in non-metallic brake friction materials on friction performance

The effects of ZrSiO₄ (zirconium silicate or zircon) as an abrasive on brake friction performance and friction layers of non-metallic brake friction materials were evaluated. The experimental results indicated that ZrSiO₄ enhances friction coefficient, but depresses wear rate. However, ZrSiO₄ can improve the negative wear rate of the friction materials. The formation and development of friction layers are complex so that the friction layers formed during friction process were carefully characterized using scanning electron microscopy (SEM), light microscopy (LM), and X-ray diffraction (XRD) methods. Following characteristics of friction layers were identified—(1) dynamic behavior: the structure of friction layers changes at the different surfacial positions and across sample's thickness; (2) friction condition dependence: formation of friction layers depends upon temperatures, time, and thermal history such as fade and recovery; and (3) compositional dependence: the compositions of friction surface and bulk differ, nevertheless the bulk's composition determine the friction layers. The phenomena as baryte films, altered layers, iron patches, and zircon loose areas formed on the friction surfaces were observed. Baryte films were detected on the friction surfaces of Zr-0 (sample without zircon). Baryte films have positive effect on wear property, but the films disappear in the presence of ZrSiO₄. The amount of carbonaceous materials decreases with the increase in ZrSiO₄. Only negligible thickness of altered layers was found on the friction surfaces of Zr-0 sample, while samples containing zircon show out relatively thick altered layers. Both iron-patches and zircon loose areas increase with the ZrSiO₄ contents. The relationships among formulation, friction performance, and friction surfaces were summarized.     

Low temperature investigations on frictional behaviour and wear resistance of solid lubricant coatings

The tribological characteristics of polymer-based solid lubricant coatings under frictional stressing in vacuum at 293, 120 or 77 K were studied. Vacuum-friction apparatus with cryogenic pumps and low-temperature tribometer designed at SR&DB of ILTP&E was used for sliding tests. It was found that the coefficient of friction is somewhat higher at low than at room temperatures. The effect of temperature decrease on the wear life of solid lubricant coatings is ambiguous and determined by the direction of changes in physical and mechanical characteristics of a solid lubricant coating under cooling and by the rate of the process of a binder tribodestruction.     

汽车制动器摩擦材料的研究现状和发展

介绍汽车制动器摩擦材料的研究现状。探讨半金属基摩擦材料、非石棉有机摩擦材料和粉末冶金摩擦材料的优缺点。提出汽车制动摩擦材料研究的发展趋势。     

Effect of reinforcement volume fraction and size distribution on the tribological behavior of Al-composite/brake pad tribo-couple

Tribological behavior of aluminium matrix composite (AMC)/brake pad tribo-couple under dry sliding conditions was studied using Pin-on-Disc machine. Brake pad material was used as pins while the AMC formed the rotating disc. Series of experiments were performed to characterize the tribological nature of the tribo-couple. Load and sliding speeds were varied over a range to represent actual braking conditions in passenger cars. Effect of volume fraction and size distribution of reinforcement on wear and friction coefficient has been studied. It was observed that a heterogeneous tribo-layer was formed over the worn surfaces during the wear tests. Presence of tribo-layer was believed to cause two effects: acting as a lubricant layer and acting as a source of wear debris. Morphology and topography of worn surfaces and debris were studied using scanning electron microscope (SEM), electron probe micro analyzer (EPMA), and X-ray diffraction (XRD) techniques. When the reinforcement in the matrix has wide size distribution, wear rate and friction coefficients are found to be higher compared to composite containing mono-size reinforcement.     

On the influence of contact tribology on brake squeal

This contribution aims at introducing tribological contact properties into the stability analysis of macroscopic structural systems with focus on brake-squeal applications.First, the surfaces of several brake pads at different states of wear are analyzed experimentally. Based on these data a statistical contact model as well as a numerical simulation are presented. Using these models two constitutive contact laws are derived, which link contact pressure and stiffness.Second, a simple brake model incorporating these contact models is developed. Results of stability analyses are presented and the influence of the contact models on the steady state stability is discussed.     

A study on the tribological characteristics of graphite nano lubricants

Many researchers have tried to improve the tribological characteristics of lubricants to decrease friction coefficients and wear rates. One approach is simply the use of additives in the base lubricant to change its properties. Recently, nanoparticles have emerged as a new kind of additive because of their size, shape and other properties. A nano lubricant is a new kind of engineering lubricant made of nanoparticles, dispersant, and base lubricant. In this study, graphite nanoparticles were used to fabricate nano lubricants with enhanced tribological properties and lubrication characteristics. The base lubricant used was industrial gear oil, which has a kinematic viscosity of 220 cSt at 40°C. To investigate the physical and tribological properties of nano lubricants, friction coefficients and temperatures were measured by a disk-on-disk tribotester. The surfaces of the fixed plates were observed by a scanning electron microscope and an atomic force microscope to analyze the characteristics of the friction surfaces. The results show that when comparing fixed plates coated with raw and nano lubricants, the plate coated with a nano lubricant containing graphite nanoparticles had a lower friction coefficient and less wear. These results indicate that graphite nanoparticle additives improve the lubrication properties of regular lubricants.     

Application of Solid Lubricants in Grinding: Investigations on Graphite Sandwiched Grinding Wheels

The intense heat generated in grinding process, if not controlled, will lead to major quality defects. Conventional liquid coolants, employed in flood form, have many limitations from technical, environmental and economic angles. Minimization or possible elimination of cutting fluids by substituting their functions by some other means is emerging as a thrust area of research in grinding. The authors have reported the feasibility of application of solid lubricants in grinding. This paper deals with the detailed investigations on solid lubricant integrated grinding wheels, by providing peripheral graphite sandwiching. Improvement in process results has been observed with this concept.     

制动器位置在电动绞车中的合理确定

制动器是绞车中一个重要的安全装置。计算表明,制动器在绞车中所处位置不同,其制动力矩亦不同,为制动器位置的合理确定提供了理论依据。     

Influence of lubricants on the performance of journal bearings – a review

ABSTRACT

The lubricant properties have a significant influence on the static and dynamic performance characteristics of journal bearing such as load-carrying capability, minimum fluid film thickness, maximum pressure, lubricant flow rate, damping coefficients, stiffness coefficients, etc. The present document reviews the behaviour of various lubricants such as power-law lubricants, couple stress lubricants, micropolar lubricants, ionic liquid lubricants and space lubricants. The influence of these lubricants on the performance of hydrostatic, hydrodynamic and hybrid journal bearings is discussed. An effort is made to develop the understanding to choose the suitable lubricant for journal bearings for different journal bearing configurations. Journal bearings operated with non-Newtonian lubricants have shown better performance compared to Newtonian lubricants. Ionic liquid lubricants have shown high potential in vacuum applications and extreme temperature environment such as in bearings of spacecraft moving mechanical assemblies.     

On a Criterion of Cutting Velocity in Metal Machining

The conventional model of orthogonal cutting with type 2 chip is modified to include the effect of deformation of the work-piece at the immediate vicinity of the tool-tip. The cutting velocity condition for optimal force of deformation is examined in the light of two alternate criteria: recrystallization temperature and melting temperature. It is shown that a critical cutting velocity exists. Furthermore, it is concluded, in part, that proper metallurgical treatment and/or preheating the work-piece (hot machining) will improve cutting.     

On the role of copper in brake friction materials

Copper is a major ingredient in friction materials used for automotive braking. The purpose of this study was to find out how copper contributes to good brake performance properties in addition to providing good thermal conductivity. Microstructural investigations of copper chips at the surfaces of brake pads revealed a zone of severe plastic deformation which provides high hardness, but there is also evidence of recrystallized copper nano-particles which are incorporated into friction layers as soft ingredient once detached from the pad surface. Thus copper seems to play a dual role, firstly as reinforcing element of the brake pad providing primary contact sites, and secondly as solid lubricant by contributing to the formation of a layer of granular material providing velocity accommodation between the rotating disc and fixed pad. Confirmation for this hypothesis was obtained by modelling contact sites on the nanometre scale with the method of movable cellular automata. Results show both, the similarity of steel fibres and copper macro-particles in respect to providing primary contact sites, as well as similar sliding behaviours of friction layers containing either copper or graphite as soft inclusions. Furthermore, it is shown that not only material properties, but also the concentration of solid lubricant particles in the friction layers, determine conditions for friction force stabilization and smooth sliding behaviour.     

半金属基提速客车盘形制动闸片摩擦特性的研究

介绍了一种适用于制造提速客车（v＝160km／h）盘形制动问片的半金属基摩擦材料的摩擦磨损特性。试验表明,研制的A配方半金属摩擦材料具有稳定的摩擦系数和较好的耐磨性及其抗热衰退性。实物惯性台某试验结果表明,研制的A配方问片具有较高的摩擦系数,制动距离较短,制动性能稳定,完全能满足提速客车运行的制动要求。     

CVT lubrication: The effect of lubricants on the frictional characteristics of the belt-pulley interface

Two tests for evaluating continuously variable transmission (CVT) lubricants have been developed using readily available test equipment and test parts. These tests have been designed to rank lubricants using a number of criteria relevant to the performance of the lubricant in a push-belt variator. These include overall level of friction, friction stability, temperature dependence of friction, and load dependence of friction. Testing lubricants of different types has shown the effect of lubricant chemistry on the parameters measured and indicates that some existing fluids, a CVT fluid and passenger car motor oil, as well as an experimental fluid, should give good performance in a continuously variable transmission using a push-belt variator.     

The origins of synthetic lubricants: The work of Hermann Zorn in Germany part 1 basic studies of lubricants and the polymerisation of olefins

This paper has been written to commemorate this January the 100th anniversary of the birth of Hermann Zorn, whose research led at the beginning of the 1930s to the first synthetic oils being produced in Germany. This development work, started in 1926 and pursued up until 1944, can be seen to have taken place in four successive stages:

• 1 basic research and synthesis of hydrocarbons in pursuit of an‘ideal’lubricant,
• 2 work to develop synthetic lubricants on the basis of olefins,
• 3 research on and development of additives to improve the performance of synthetic lubricants,
• 4 synthesis, research into structure, and process development of esters for special lubricants with advanced oxidative stability and good low-temperature behaviour.

The first part of this survey of his work describes his basic research on lubricants and his work on the polymerisation of olefins. The second part will look at his work on additives and ester oils and their application in aviation.     

调整臂上的制动蹄片磨损报警器的测量误差分析

围绕在调整臂上设计制动蹄片磨损报警装置,分析因磨损而产生的间接测量摩擦片厚度的误差,并对某S凸轮制动器报警设备进行了设计。