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The brake disk and friction material parameters were taken as design variables, with the negative damping ratio of the unstable mode as the optimization target. The central composite design method was employed to obtain suitable data sample points. A neural network response surface model was constructed to predict the real part values of the unstable mode. Structural optimization design was then conducted using a screening method to derive optimized parameters for the brake disk structure and physical parameters such as density, elastic modulus, and Poisson's ratio of the friction material. The optimized coefficient of the negative damping ratio of the brake system's unstable mode was enhanced, thereby reducing the likelihood of brake squeal. Harmonic response analysis showed a significant optimization effect on the curve of brake disk amplitude fluctuations with frequency. These findings offer valuable insights for improving the stability of disk brake systems. [ABSTRACT FROM AUTHOR]

The article analyses the results of an experimental study devoted to the impact of the mutual overlap coefficient on the friction factor of the model brake lining and brake disk in a disk brake.The mass ratio of the brake lining and brake disc models is 1:200 (the brake lining mass is 8 grams and the brake disk mass is 1,600 grams). The load level has been 0.2–0.5 N. This mass ratio and load level ensure an effective heat removal from the friction zone. The brake disk model is made of 35GS steel. The brake linings are made of two friction materials, i.e. CSiC and SCh25 cast iron. The mutual overlap coefficients for the experiments have been 0.25, 0.5, 0.75, and 1.0. It has been shown that when the mutual overlap coefficient rises from 0.25 to 1.0, there is a tendency for the friction factor to increase in the ‘SCh25 cast iron – 35GS steel’ and ‘CSiC- 35GS steel’ friction units. An increase in the friction factor by approximately 10–12% is observed for the ‘SCh25 cast iron – 35GS steel’ friction pair. An increase in the friction factor is 8–10% for the ‘CSiC- 35GS steel’ friction pair.With effective heat dissipation, the increase in the coefficient of friction occurs due to the reduction in mechanical pressures in the contact area and the increase in the number of micro-irregularities involved in the friction process. [ABSTRACT FROM AUTHOR]

The tribological performance of C/C–SiC paired semi-metallic brake pads suitable for automobiles was investigated in this study. Factors on tribological properties of semi-metallic brake pads such as the contents of phenolic resin, copper fibers, steel fibers and MoS 2 were tested by the orthogonal experimental. According to the SAE-J2522 test procedure, an optimized compositional formulation was derived based on the brake test results combined with fuzzy comprehensive evaluation. The wear mechanism of brake pairs was discussed, and the compositional formulation of the brake pad was further optimized after the analysis of the friction surface morphology before and after braking. The results showed that copper fibers had the greatest effect on the friction performance of brake pads. Copper fibers contributed to stabilization of the coefficient of friction (COF) and effectively improved the wear resistance. However, at higher braking speeds (≥120 km/h), the copper fibers were converted from fibrous to flaky and softened, acting as a solid lubricant on the friction surface, resulting in a low COF of brake pads. The tribological performance of brake pads could be improved by reducing the content of copper fiber and increasing the content of hard particles. [ABSTRACT FROM AUTHOR]

The braking systems in cars convert the kinetic energy of the vehicle into heat energy in order to slow it down. The brake pad must quickly absorb heat without wearing out fast. A disc and brake pad if properly matched has a significant effect on these variables. As a result of new technology, it is now feasible to create materials that differ in their quantities and composition and combine them in regulated processes. The characteristics of the friction material have a crucial impact on brake performance. In this study, two distinct materials were selected and their usefulness for tribological features were observed and compared. [ABSTRACT FROM AUTHOR]

The study of the tribological behavior of the braking system in auto vehicles requires knowing the characteristics of the material in contact and, in the work process, the friction pair brake disc pads. Material structural analysis is necessary because the wear process depends both on the friction-pair chemical composition (brake disc pads) and on the work process parameters (pressing force, rotational speed, traffic conditions, etc.). The material of the brake discs is generally the same, gray cast iron, and the brake pads can be semimetallic (particles of steel, copper, brass, and graphite, all united with a special resin), organic materials (particles of rubber, glass, and Kevlar, all joined with the help of a resin), composite materials that contain different constituents, and ceramic materials (rarely have small copper particles). Therefore, the purpose of this paper is to analyze the crystalline structure, tribological behavior (at friction and wear), and the mechanical properties of the materials of the brake disc–pad friction pair specific to the field through study and analysis. [ABSTRACT FROM AUTHOR]

In this study, the effect of rolling of 1.25Cr-1Mo-0.5V-0.3C American Iron and Steel Institute 4340 modified steel for highspeed railway brake discs on the microstructure and mechanical properties was investigated. The materials were hot-rolled at 0%, 51%, and 66% reduction ratios, and then analyzed by optical microscopy, scanning electron microscopy, and electron backscattering diffraction (EBSD). needle-shaped ferrite block morphology in bainite varied with the rolling ratio. EBSD analysis reveals dynamic recovery and dynamic recrystallization, affected ferrite block boundaries and dislocation densities during rolling. Mechanical tests showed that hardness, toughness and elongation increase at higher rolling reduction ratio, while strength remained relatively constant. In particular, the impact toughness increased almost twice from the level of 70 J in S1 (0% reduction) to the level of 130 J in S3 (66% reduction). These results showed that the hot rolling can significantly improve the strength and toughness combination of cast brake discs material. [ABSTRACT FROM AUTHOR]

A comprehensive modeling strategy for studying the thermomechanical tribological behaviors is proposed in this work. The wear degradation considering the influence of temperature (T) is predicted by Archard wear model with the help of the UMESHMOTION subroutine and arbitrary Lagrangian–Eulerian (ALE) remeshing technique. Adopting the proposed method, the thermomechanical tribological behaviors of railway vehicle disc brake system composed of forged steel brake disc and Cu-based powder metallurgy (PM) friction block are studied systematically. The effectiveness of the proposed methodology is validated by experimental test on a self-designed scaled brake test bench from the perspectives of interface temperature, wear degradation, friction noise and vibration, and contact status evolution. This work can provide an effective way for the investigation of thermomechanical tribological behaviors in the engineering field. [ABSTRACT FROM AUTHOR]

In this work, we evaluated the impact of disc rotors of gray cast iron (GCI), nitrocarburized (NC), and superhard ceramic-coated (SCC) GCI on the brake wear PM emissions of passenger vehicles using dynamometric measurements. The brake emission factor (BEF) of the SCC was greatly reduced by more than a factor of 1/5 compared with those for the GCI and NC for both low-steel and non-steel friction materials. Surface topological and microstructural analyses confirmed that more severe wear was pronounced for the NC rotor compared with the SCC, as evidenced by large concave pits in the wear tracks. Analysis of the size-classified airborne PM suggests that reduced micron-sized particles, which originated from the GCI disc, were responsible for the lower BEF due to the increased hardness of the SCC. [ABSTRACT FROM AUTHOR]

Braking is one of the most critical systems for ensuring the safe driving performance of motor vehicles. Among the components that constitute the braking system, the disc is the one with the highest risk of wear. When the braking system is engaged, the physical contact between the brake pad and the disc leads to the generation of high pressure and high temperature. This released heat shortens the material's lifespan. The wearing or fracturing of the brake disc can result in a significant safety vulnerability. Therefore, it is desired for the discs to have better heat dissipation to increase their longevity. In this study, two different designs of brake discs were first examined thermally using the computational fluid dynamics (CFD) method. Subsequently, numerical analyses were conducted under the same boundary conditions by selecting the disc geometry with superior heat dissipation performance and using different materials. The results obtained from the analyses were compared and interpreted. The materials utilized in the study were grey cast iron, carbon steel, stainless steel, and carbon-carbon composite. As a result, it was observed that the carbon-carbon composite exhibited higher resistance to elevated temperatures. [ABSTRACT FROM AUTHOR]

The study of the tribological behavior of the braking system in auto vehicles requires knowing the characteristics of the materials in contact with the friction pair, brake disc–pads, in the work process. Analysis of the materials is necessary because the wear process depends on the friction pair, and brake disk–pads, respectively on the parameters of the work process (rotational speed, pressing force, traffic conditions, etc.). The material of the brake discs is generally the same gray cast iron, but the brake pads can be semi–metallic (combination of metallic and non–metallic materials, all bonded with a special resin), organic materials (non–metallic components such as glass, rubber, and kevlar all joined with the help of a resin) and ceramic (they have only ceramic material as a composition, rarely have small copper particles). The purpose of the work is to know the crystalline structure and the mechanical properties of the brake pad materials, through specific analyses, with important implications on the friction and wear behavior. [ABSTRACT FROM AUTHOR]

Brakes are an important safety feature of vehicles. The materials of which the friction elements are made pose some risk to the environment. This can be a case during manufacture, operation and disposal. Any step to improve the ecology deserves thorough examination and possible introduction into production. For this reason, it has been decided to investigate whether it is possible to replace aramid with another material that is already present in its composition. The choice fell on copper, which was used in prepared samples in the form of both powder and fibers. [ABSTRACT FROM AUTHOR]

Laser cladding is a method to deposit a particular material on another surface. It enables materials to be deposited precisely, selectively, and with as minimal heat input as possible into the underlying substrate. This process improves a part's surface quality and wear resistance and allows for repairing damaged or worn surfaces. It is an eminent and effective process of repair manufacturing to create novel low friction materials for dry sliding. This technique is used in various industries, including automotive, medical, and manufacturing. Based on the powder injection technique, it benefits rapid production, parts repair, and surface coating, which often have low dilution, low porosity, and good surface homogeneity. Laser cladded brake discs are now well accepted in the automotive industry for their stable coefficient of friction (CoF), low wear of brake components, and minimum wear particle emissions. The future of next generation automotive brake discs lies with laser cladding surface modification, which imparts lower wear particle emissions with minimal deviation in the friction behaviour. This prolongs the brake disc's lifetime and prevents premature failure. The optimum CoF and lower wear rate would be the essential factors in selecting a coating material for producing stable friction layers in tribological research for brake discs. This paper delivers a broad understanding of the present state-of-the-art laser cladding process, mainly focusing on its application in the automotive brake disc industry. With the current research focused on next generation electric vehicles with zero emissions, this surface modification technique could be extensively used for coating automotive brake discs with powders such as TiB2, TiC, WC, WC-Co, and other Fe and cermet or metal-ceramic alloys. [ABSTRACT FROM AUTHOR]

The paper studies new materials for brake disks used in car manufacturing. The materials used in the manufacturing of the brake disc must adapt and correlate with the challenges of current society. There is a tremendous interest in the development of a material that has high strength, good heat transfer, corrosion resistance and low density, in order to withstand high-breaking forces, high heat and various adverse environment. Low-density materials improve fuel efficiency and environmental impact. Complex concentrated alloys (CCA) are metallic element mixtures with multi-principal elements, which can respond promisingly to this challenge with their variety of properties. Several compositions were studied through thermodynamic criteria calculations (entropy of mixing, enthalpy of mixing, lambda coefficient, etc.) and CALPHAD modeling, in order to determine appropriate structures. The selected compositions were obtained in an induction furnace with a protective atmosphere and then subjected to an annealing process. Alloy samples presented uniform phase distribution, a high-melting temperature (over 1000 °C), high hardness (1000–1400 HV), good corrosion resistance in 3.5 wt.% NaCl solution (under 0.2 mm/year) and a low density (under 6 g/cm3). [ABSTRACT FROM AUTHOR]

In this article, considering the coupled interaction of heat, stress, material wear, and wheel–rail force transmission in the disc-braking process, a complex multifield coupled method was proposed to study thermal mechanical properties and contact state of brake discs. First, a coupled dynamic model of train, track, and brake gear was established to analyze the force transmission between brake friction pairs and wheel–rail system. Based on the coupled dynamics simulation results, a thermomechanical wear coupled model of the friction pair was established. It is found that the track irregularity results in vertical relative displacements with a range of (–2.6 mm, 2.8 mm) and makes the maximum brake force increase to 24.1 kN. As a comparison, brake bench tests without wheel–rail interaction were carried out. This showed that there was no vertical relative displacement between the friction pair, and the braking force had a stable value of 22.5 kN. The simulation results of the brake disc temperature distribution, and the friction pair contact state are consistent with the bench test results. In addition, different thermal simulation methods of the brake disc were used to verify the validity of the complex multifield coupled simulation results. [ABSTRACT FROM AUTHOR]

The influence of braking sequence on railway brake disc's radial crack propagation behavior is analyzed considering the effect of crack geometry features, material elastoplasticity, and crack closure. The results show that when the residual stress generated in the initial braking is low, the peak stress in the subsequent braking will be low, and the average response state is more inclined to compression. The influences of the braking sequence are mainly reflected in the mid‐late stage of crack growth. In the early stage, the radial cracks almost synchronously expand inward and outward. While in the mid‐late stage, the cracks mainly expand inward. When the initial braking is relatively mild, the brake disc's stress–strain response and crack propagation behavior can be improved. It is beneficial to extend the brake disc's service life by designing a suitable prefabricated working condition or introducing an appropriate residual stress field through surface treatment. Highlights: The influence of crack closure on brake discs' crack propagation behavior is considered.The variation of crack propagation behavior in different service stages is discussed.The effect of braking sequence on brake discs' crack propagation behavior is studied.The proposal for the service life improvement of the railway brake discs is presented. [ABSTRACT FROM AUTHOR]

Exhaust regulations and improved exhaust gas treatment systems have already initiated the trend that brings emissions from brakes and tires to the forefront of traffic-induced particulate matter. The health and environmental relevance of particulate matter has resulted in regulators, industry, and research institutions prioritising the mitigation of non-exhaust particle emissions. To this end, under the umbrella of the United Nations Economic Commission for Europe World Forum for Harmonisation of Vehicle Regulations (UNECE WP.29), the Working Party on Pollution and Energy (GRPE) mandated the Particle Measurement Programme Informal Working Group (PMP-IWG) to develop a Global Technical Regulation (GTR) for measuring brake dust. The standards and procedures defined within the GTR should eventually form the basis for the introduction of a Euro 7 limit value for brake emissions. The purpose of this measurement campaign is to provide an exemplary overview of the emission behaviour of wheel brakes and friction pairings currently available on the market and to identify possible reduction potential with regard to particulate emissions. All measurements were carried out taking into account the draft GTR valid at the time of execution. For the investigations, brakes were selected using the example of different vehicle classes, brake concepts (disc and drum brake), vehicle axles (front and rear axle), and alternative friction materials (brake disc and pads/shoes). Thus, the use of wear-resistant discs and improved brake pad compositions are able to achieve significantly lower emissions. In addition, the measurement of brake dust emissions from vehicles with different levels of electrification was considered. Electrical braking was modelled and applied to the Worldwide Harmonised Light-Duty Vehicles Test Procedure (WLTP) Brake Cycle, which has demonstrated high emission reduction potentials depending on the electrification level. [ABSTRACT FROM AUTHOR]

In this paper, an automobile brake lining made of wood ceramic is proposed, and a 3D model of a disc brake of a wood ceramic brake lining is established to simulate the thermoelastic coupling characteristics of the disc brake under the action of the wood ceramic brake lining under various braking conditions. Based on the Archard wear model and the UMESHMOTION subroutine in the ABAQUS software, the numerical simulation of the wear depth of the wood ceramic brake lining is realized. The results show that, when wood ceramic is used as the friction material of automobile braking, the peak temperature of the brake disc during the braking process is 254.25°C, which is 9.91°C lower than that of the traditional metal brake lining, and the stress distribution is uniform. It is beneficial to reduce the generation of thermal cracks in the brake disc, and at the same time reduce the influence of the " thermal decay " effect of the brake disc on the stability of the braking performance of the vehicle. The temperature of the wood ceramic brake lining can reach a maximum of 281.41°C during the braking process, which is far lower than the thermal decomposition temperature of the wood ceramic material, and has good reliability. With wood ceramic as the friction material of the brake lining, the maximum wear depth of a single high-speed emergency braking does not exceed 2.11 µm, which has good wear resistance. [ABSTRACT FROM AUTHOR]

• 3D friction maps were used for thermally coupled braking simulations. • The calculated velocity and coefficient of friction agree with the experimental data. • The accuracy of the solution depends on the temperature field determination. • The proposed approach allows for a comprehensive analysis of the given friction pair. The coefficient of friction during braking is not constant. Determining its variability requires measurements in real conditions. This paper presents a methodology of conversion of the measured time profiles of the sliding velocity V eq , contact temperature T , and coefficient of friction f , into analytical formulation of two variables z = f(x,y). This was executed in the following steps: 1) creating a three-column table V eq , T , f from experimental measurements; 2) interpolation using Kriging; 3) creating a contour map of the coefficient of friction dependent on the sliding velocity and temperature, 4) import of a grey scale image of the friction map into the finite element (FE) software, and 5) definition of a function z = f(x,y). The studies were carried out for five composite organic friction materials and cast-iron brake disc of a railway vehicle. The developed five friction maps for each friction pair were based the data from the full-scale bench tests during braking from the initial vehicle velocity of 80 km h−1, 120 km h−1, 140 km h−1, 160 km h−1, 200 km h−1 to a stop. In the second part of the study the initial-value problem for the equation of motion combined with the heat conduction problem were formulated and solved numerically using special functionalities of the FE software, e.g. Deformed Geometry, Mathematics. Changes in the vehicle velocity and time profiles of the coefficient of friction were determined from the solution of the coupled thermal problem. The computational FE model was verified by comparing the measured and calculated changes in the vehicle velocity, coefficient of friction and evolutions of the brake disc temperature during single braking. The maximum calculated temperature 1 mm under the contact surface of the brake disc, during braking from initial vehicle velocity of 80 km h−1, was obtained for the base friction material and was equal to T 1 , 3 , 5 Num. = 72 °C. The corresponding experimental value was T 1 - 6 Exp. = 66.1 °C. When braking from 140 km h−1, for the same material it was T 1 , 3 , 5 Num. = 129.7 °C and T 1 - 6 Exp. = 130.7 °C. The obtained differences in braking times calculated and measured did not exceed 1.7 %. The corresponding temperature differences of the disc at the stopping time were lower than 5.5 %. [ABSTRACT FROM AUTHOR]

An analytical model of frictional heating in a railway disc brake system during a multiple braking process is proposed. It considers the thermal sensitivity of the friction coefficient and the thermophysical properties of the materials. The developed model accounts for convective cooling of the brake disc only during the intervals between consecutive braking applications. The theoretical outcomes were compared with experimental data obtained from simulation on a full-scale inertia dynamometer for a friction node consisting of a cast iron railway brake disc combined with a composite friction material. An increase in temperature (by 30–50 °C) at each subsequent braking, accompanied by a simultaneous decrease in the friction coefficient, was observed. The analysis indicated that the relative difference between the maximum temperature values at each braking stage, derived from the model and the data recorded by the thermocouple system during testing, was less than 5 %. The good agreement of the theoretical results with the experimental data confirms the validity of the proposed model, which can be used to estimate the temperature of a disc brake operating in multiple braking modes with non-uniform cycles. Previously, such schemes have only been developed and validated for single and repetitive short-term braking modes. [ABSTRACT FROM AUTHOR]

Phenolic resins are the most commonly used binders in brake pads for automotive disc brake systems owing to their affordability and thermal properties. However, they also show some limitations related to their crosslinking mechanism. Benzoxazine resins present themselves as possible alternatives for this application by providing enhanced thermal properties as well as other industrially attractive characteristics such as lower moisture absorption and unlimited shelf life. This study investigates the thermal properties of two different benzoxazine resins, with the aim of assessing their capabilities as binder for brake pad and of understanding how to process them in order to actually employ them as such. DSC, TGA, hardness and tribological analyses were carried out on neat resin samples and on friction materials containing them as binder. The presence of several concurring reactions was detected during the crosslinking reaction of benzoxazine resins. The benzoxazine resins showed lower mass loss respect to a phenolic resin in the temperature range of interest for commercial brake pads application. Friction material containing benzoxazine resin binder showed promising tribological results. [ABSTRACT FROM AUTHOR]

Copyright of Rolling Stock (1002-7602) is the property of Rolling Stock Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The pin on the disc friction tester was used to conduct the intermittent braking testing of train brake materials with a low-temperature environment simulation device at temperatures 20 °C, 0 °C, −10 °C, −20 °C, and −30 °C. The results show that intermittent braking presents different wear characteristics of braking materials at low temperatures. Under different ambient temperature conditions, the most volatile friction coefficient caused by intermittent braking happens at 0 °C, and the wear rate of brake materials reaches its maximum at 0 °C. The wear surface morphology of the brake pad material mainly includes scratches, furrows, adhesions, and abscission pits, while the surface of the brake disc material was dominated by scratches, furrows, and adhesions. With the decrease in temperature, the adhesion damage of the brake pad/disc material increases. At 0 °C, the brake pad material has crack damage. [ABSTRACT FROM AUTHOR]

The article presents finite element models of the 2xBgu type tread brake for the simulation of extended repeated frictional heating carried out on a full-scale inertia dynamometer. The numerical calculations were conducted for the brake blocks made of two organic composite materials newly developed specifically for this study. The transient temperature changes obtained from the 2D axisymmetric and 3D finite element analyses and experimental data agreed well during continuous process of about 1200 s. Simulation of such a long period of braking sequence required introducing simplifications in the boundary conditions in the contact area, convection cooling, arrangement of the model (2D axisymmetric, 3D). The focus was laid on representation of variation of the coefficient of friction and the temperature dependence of the properties of the friction materials during braking. The carried out research indicates limitations in the finite element analysis and directions of necessary improvements in modelling as well as measurements with the use of embedded thermocouples. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to clarify the relationship of friction material type and brake disc temperature through braking experiment. Design/methodology/approach: The braking performances of resin materials (RM), semimetallic materials (SM) and copper-based powder metallurgy materials (PM) friction blocks mating with forged steel brake disc were examined based on TM-I-type reduced-scale inertial braking dynamometer. The brake disc surface temperature was recorded by infrared thermal camera during braking. Findings: Experimental results indicate that the thermal wear resistance of three friction materials differs with mental content, resulting in the deviation of pad-disc system contact state during braking, thus forming different temperature distribution on the brake disc surface. The peak temperature on the disc face of RM (190°C) is 36.6% and 45.4% lower than that of PM (300°C) and SM (348°C) at 160 km/h. The maximum radial temperature deviation of PM (35°C) is approximately three times than that of RM (12°C) and 40% higher than that of SM (25°C) at 50 km/h, whereas the maximum temperature deviation of SM (97°C) is six times than that of RM (16°C) and 31% higher than that of PM (74°C) at 160 km/h. Originality/value: The effect of friction material type on the disc surface temperature distribution is revealed, which provides a meaningful reference for the design of brake friction pairs and choice of brake pad materials. [ABSTRACT FROM AUTHOR]

Gray cast iron (GCI) is a conventional material used in industrial applications and it is well known for its usage in brake disc fabrication. In the case of vehicles that serve passenger transport, one of the solutions to prolong the lifetimes of brake discs can be to laser clad their surface with harder and corrosion-resistant materials. This research aims to improve the mechanical properties of the brake discs using Inconel 718 (IN718) metallic powder to laser cladding the parts' surfaces by a direct energy deposition (DED) method. By using the proper process parameters, the interface between the substrate and the deposited material was uniform and adherent and forming a compact bonding of the two materials, without pores or cracks. It was found that the average hardness of the IN718 deposited material was twice higher than the one of the GCI substrates. By comparing the friction coefficient (CoF) of the IN718 coatings with that of the brake discs, a difference of 0.12 in favor of IN718 was assessed. The depth of the wear track was analyzed for both materials and showed that the pin trace on the GCI (−150 µm) surface was 3 times deeper than the trace produced on the surface coated with IN718 (−50 µm). The corrosion resistance of the IN718 coating was superior by four orders of magnitude to that of GCI substrate in 3.5 wt.% NaCl aqueous solution. [ABSTRACT FROM AUTHOR]

The stability and reliability of braking system are essential factors for the safe operation of high-speed trains. In the proposed work, tribological properties of a newly developed brake disc material namely BD-1 were studied considering the thermal-mechanical effects, as well as the evolutions of wear debris, were particularly examined. The tribological properties were also compared with an existing commercial brake disc material namely BD-2 in text. Friction and wear tests were carried out on BD-1 and BD-2 against a commercial brake pad material (BP) to simulate the real emergence braking conditions of a 350 km/h high-speed railway. The thermal-mechanical coupling effects of the friction velocity, wear mass, temperatures and the friction coefficient were investigated. Local wear track and wear debris were analyzed by using SEM and EDS. Results show that the shape and size of wear debris evolve as the dominant wear mechanism varies during braking tests. As the sliding speed increases from 250 to 1250 rpm, the debris may become fine particles, then into a mixture of lamellar shape and flake shape, and finally becomes fine particles again at high speed. The maximum size of wear debris is first from 20 μm to 65 μm, and then down to 10 μm. As the local area temperature increased by more than 400 °C, debris adhere to the surface forming an adhesive layer that may act as a lubricant. Debris may help to form an adhesive lubrication layer and undertake plastics defor-mation at the speed range of 500–1000 rpm. The local area temperatures prompted the wear debris adhesion and oxidation. After reaching a certain speed limit, a uniform third body appears to protect the material surface from high speed and high temperature. Results suggested that the BD-1 could be a good candidate braking material for high-speed railway applications. [ABSTRACT FROM AUTHOR]

For road safety, braking system performance has become a very important requirement for car vehicle manufacturers and passengers. To this end, vehicle designers must understand the characteristics of tribological behavior and the causes of their variation in properties. This paper analyzes the tribological behavior (at friction and wear) of the most recent material couples of the braking disk-pad system affected by their structural change through the implications on the braking system stability, reliability and suitable characterizations. Obtaining information to design a very efficient braking system and assessing the influence of the material's structural changes on its stability has become a necessity. This has been made possible by using several methods of testing a brake disk-pad couple on various devices intended for this purpose. The materials of the contact surface disk-brake pad with their tribological performance (friction, wear), especially the friction coefficient, present particular importance. Also, system components' reliability, heat transfer and the noise and vibration of the brake disk-pad couple are vital to the correct operation of the braking system and should be given special attention. The test results obtained define the friction patterns and the influence of structural changes and other environmental factors that can be used in computer analysis. [ABSTRACT FROM AUTHOR]

In this article, an intermittent braking strategy (IBS) was proposed to improve the thermal-mechanical performance of the brake system under emergency braking, and its feasibility was performed by the thermal-mechanical-wear coupling analysis model validated with experiment results. According to the simulation results, the maximum thermal stress of brake disk for the conventional continuous braking strategy is about 879 MPa at initial brake speed of 350 km/h, which has exceeded the material property limits, yet the intermittent braking strategies can alleviate it obviously with a decrease of 139 MPa. Furthermore, the maximum temperature and thermal stress of the optimal IBS can be decreased by 18% and 40%, respectively, which shows the significance and validity of the proposed IBS. [ABSTRACT FROM AUTHOR]

Brakes are one of the most important systems in each vehicle. For this reason, numerous studies are carried out in many scientific institutions that allow for better understanding of friction and wear phenomenon. Therefore, the correctness of the obtained results is of great importance. Hence, the choice of the research method is not without significance. In this paper, it was decided to check how the choice of the method will affect the quality of the obtained results. The chosen methods were Ball-cratering and Pinon-disc. Six groups of samples taken from three different types of pads were tested. The pads were both brand new and used. The analysis of the results was performed using the chi-square concordance test. It was established that at the significance level of 0.95, the choice of the research method was not statistically significant. Both methods provide similar high-quality results. [ABSTRACT FROM AUTHOR]

Copyright of Problems of Friction & Wear is the property of National Aviation University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, an investigation of the load-dependent wear behavior of copper-free semi-metallic brake material is presented. The experiments were conducted in ambient thermal settings with varying sliding velocities (3.141 m/s, 2.09 m/s, and 1.047 m/s), normal load (60 N, 50 N, and 40 N), and sliding distance (4500 m, 3000 m, and 1500 m). Taguchi's method was used in designing experiments to examine the output through an L9 orthogonal array. ANOVA was used to identify the consequence of interactions among different constraints. It also established the significant contribution of each process factor. The objective was set as the 'smaller is better' criterion to find minimum wear conditions. The impact of the normal load on the wear process was found to be maximum (71.02%), followed by sliding velocity (27.84%) and sliding distance (1.14%). The optimum condition for the minimum wear rate was found at 40 N normal load, 1500 m sliding distance, and 3.14 m/s sliding velocity. The results were confirmed with validatory friction experiment runs. The resulting error was within 10% error, which verified the experiment methods. The SEM investigation of worn surfaces of pin and disc confirmed abrasive wear and adhesive wear at 60 N and 40 N, respectively. [ABSTRACT FROM AUTHOR]

The coefficient of friction (COF) is one of the core factors in the evaluation of brake system performance. It is challenging to predict the COF, since it is strongly influenced by several parameters such as contact pressure (p), slip rate (v) and temperature (T) that depend on the driving conditions. There is a need for better models to describe how the brake friction varies under different driving conditions. The purpose of this research is to study the possibility of using 3D friction pvT-maps to estimate the COF of a disc brake system under different driving conditions. The 3D friction pvT-maps are created by filtering results of material tests conducted in a mini-dyno inertia bench. The COF measured under different driving cycles in an inertia dyno bench with the full brake system are compared with the COF estimated by the friction maps coming from the reduced scale dyno bench to investigate the validity of the simulation approach. This study shows that mini dyno bench is suitable to obtain a tribological characterization of the friction pad–disc rotor contact pair and is able to replace the full inertia dyno bench to investigate the brake system performance. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the wear of railway brake disc/pad in low-temperature environment and to explore the damage form of brake disc/pad materials and the law of temperature rise in braking process and its influence on friction pair material damage. Design/methodology/approach: The influence of ambient temperature on tribological properties of brake materials was studied by using low-temperature environment simulation device and MM-1000 high-speed brake testing machine. The law of temperature rise in the braking process was simulated by temperature field module of COMSOL. Findings: The damage of disc sample increases with the decrease of ambient temperature, and the main damage form is furrow. With the decrease of ambient temperature, pitting corrosion, wear, spalling and cracks appear successively. The maximum temperature of brake disc decreases linearly with the decrease of ambient temperature. However, when the ambient temperature is 0 in the experiment, the surface temperature of the disc will increase abnormally because of the increase of abrasive particles caused by the toughening and brittleness transformation of the material. Originality/value: In this paper, through the study of train braking in low-temperature environment, the damage mechanism and law of train braking pair in low-temperature environment are found, which provide some basis for the development of high-speed railway in low-temperature environment. [ABSTRACT FROM AUTHOR]

A binary C/C brake disc (i.e., the test brake disc) was prepared with a C/C (pyrolytic carbon/resin carbon) matrix using modified natural gas as the carbon source through the isothermal chemical vapor infiltration (ICVI) process with a directed flow and the pressure impregnation carbonization (PIC) process with liquid-phase furfural acetone resin. The microstructural, mechanical, thermal, friction and wear properties of the test brake disc were comprehensively analyzed and compared with commercial ones. The results showed that the production efficiency of the test brake disc was 36% higher than that of the commercial ones, which were manufactured through a thermal-gradient chemical vapor infiltration (TCVI) process. The favorable mechanical and thermal properties of the test brake disc were comparable to the commercial ones. While the test brake disc had a more consistently rough laminar microstructure on the worn surface of the brake disc than the commercial ones, this avoided the annular grinding grooves on the worn surface after the braking tests. In addition, the test brake disc had a stable friction coefficient with a low dispersion coefficient of 3.90%, which would improve the friction stability of C/C brake discs used in aircrafts. [ABSTRACT FROM AUTHOR]

Aluminum alloys are well known light-weight alloys and very interesting materials to optimize the strength/weight ratio in order to reduce automotive vehicle weight, fuel consumption and CO 2 emissions; unfortunately, they are also relatively soft and therefore cannot be used for high wear applications. The aim of this work was to develop an aluminum alloy brake disc with wear-resistant SiC particle reinforced aluminum matrix composites (SiC/Al) joined on to its surface. Different approaches based on brazing or shrink fitting joining technologies were used to join SiC/Al to the aluminum alloy surface. A functional graded structure was built by brazing thin layers of aluminum matrix composites reinforced with progressively higher amount of SiC particles by using a Zn–Al based alloy as joining material. Several samples were prepared by shrink fitting and brazing: 40 mm x 40 mm x 10 mm samples and a 100 mm diameter brake disc with 68% SiC particle reinforced Al matrix surface and aluminum alloy A365 body. Tribological tests demonstrated that an aluminum alloy brake disc with wear-resistant SiC particle reinforced aluminum matrix composites (SiC/Al) brazed on its surface is a promising technical opportunity. [ABSTRACT FROM AUTHOR]

Tribological conditions of the brake components during operation have a dominant effect on brake wear. Tribological analysis is one of the most important mechanical fields in the industry. The tribological properties of two contact surfaces of engines and machines generally depend on factors such as load, speed, temperature, slip time, lubricant and additives. The individual friction mechanisms depend on the temperature, normal load and sliding speed, so the coefficient of friction is dependent on these parameters. High temperature values during braking cause brake degradation, premature wear, brake fluid vaporization, bearing failure, thermal cracking and thermal vibration. The ideal brake pads must ensure a uniform and stable friction in all working conditions, without causing brake degradation, regardless of temperature. Brake friction materials consist of at least 10 components, required to achieve the desired braking performance, including stable coefficients of friction, reduced wear and low noise, in a wide range of braking conditions. [ABSTRACT FROM AUTHOR]

In this paper, the refurbishing of worn-out brake discs by coating with powder via direct energy deposition (DED) is evaluated. A medium carbon steel powder was used to coat cast-iron discs. Deposition of this steel was carried out directly on the disc surface or, alternatively, after a previous deposition of a buffer layer made of stainless steel. It was seen that the use of a buffer layer ensured a good coating adhesion, despite the formation of cast microstructures at the interfaces between the disc and the two different coatings (buffer and outer layer). Coated discs were tested against two different Cu-free commercial friction materials to evaluate their tribological properties. Very similar friction coefficients, specific wear rates, and total emissions were measured for both friction materials sliding against the coated disc. These tribological data are slightly higher with respect to those obtained in the case of an uncoated disc, suggesting that improvement of the top coating composition and surface finishing is necessary in order to achieve better performances. [ABSTRACT FROM AUTHOR]

The coefficient of friction (COF) is an important parameter when evaluating brake system performance. It is complex to predict friction due to its dependence on parameters, such as sliding velocity, contact pressure, temperature, and friction material mixtures. The aim of this work is to evaluate the macroscopic COF of a disc brake system under specific braking conditions by a meso-scale approach, using a cellular automaton simulation where the friction material mixture is modelled starting from its basic components. The influence of the local components in contact is taken into account. Simulated COF values are in line with the experimental values. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to develop magnetic field-controlled friction braking technology, the preparation process of hard magnetic brake friction material was optimized and analyzed in this paper. Design/methodology/approach: NdFeB, a rigid magnetic material, was selected as additive. Magnetic field orientation, a part of material preparation, was added to the preparation process. Experiments investigated the tribological properties of each brake lining sample. The preparation process of the hard magnetic friction material was optimized based on fuzzy theory by using analytic hierarchy process (AHP) methods and SPSS software. The microscopic morphology and the distribution and content of elements of friction lining samples prepared with or without orientation excitation voltage were analyzed by scanning electron microscope and energy dispersive X-ray microanalysis. Findings: The results showed that the tribological properties of brake lining samples could be improved by process optimization and the oriented excitation voltage can effectively improve the properties of the brake lining. Originality/value: The magnetic field orientation was added into the traditional preparation process, and a set of process parameters with the best tribological properties were obtained through optimization. It is believed that this research will be of great theoretical and practical significance to develop both new brake materials and active control technology of the braking process in the future. [ABSTRACT FROM AUTHOR]