The article presents a fully coupled 3D thermomechanical model of a railway vehicle disc brake for calculations of temperature, stress, contact pressure and wear distributions. Five specially ...designed composite organic friction materials associated with a cast-iron ventilated brake disc were analyzed. The performed computer simulations correspond to the operational parameters of braking carried out on a full scale dynamometer test stand at constant braking power and constant vehicle velocity. These conditions were obtained by correcting the clamping force in relation to changes in the coefficient of friction. In the finite element (FE) model of the disc brake, the pad wear depth distribution was determined on the basis of the Archard's law taking into account the specific wear rate, contact pressure and sliding velocity. To create the numerical model with the geometry deformation allowing for friction material loss due to wear, advanced techniques were adapted. The geometric model of the brake includes the complex shapes of the brake pad holder, brake pad and ventilated disc. The wear constants of the tested friction material were obtained by means of the FE simulation and the measurement of the pad weight loss before and after the test on a full scale dynamometer test stand. The distributions of temperature, stresses, contact pressure and accumulated wear depth, obtained from the finite element analysis, in combination with the measured changes in the clamping force and coefficient of friction during braking, enabled to establish relationships between the properties of materials, operational parameters of braking and geometrical features of the brake components.
•Thermomechanical coupled model of a brake enables predicting wear depth.•Slight differences in materials properties affect thermal behavior of the brake.•High thermal expansion coefficient leads to non-uniform contact pressure.•Coefficient of friction fluctuations do not vary deformations of the pad.•Convergence of the finite element solution depends on many factors.
The present paper addresses the tribological behaviour of new eco-friendly brake friction materials with rice husk (RH). Three formulations with different RH content (0%, 6% and 12%) were developed ...and subjected to the SAE J2522 test procedure, plus an extra high-temperature section, through a laboratory-scaled braking tribometer. At 300 °C, RH acted holding wear debris and improving wear resistance due to the formation of large contact plateaus. At 550 °C, RH's organic compounds degraded, leading to a greater material fade. Formulation 6% RH outperformed the others, showing the lowest wear. In this case, the effect of the hard and temperature resistant silica outweighed the degradation of the organic compounds.
•Eco-friendly brake materials were developed with different amounts of rice husk.•Increasing the amount of rice husk increases wear resistance at low temperatures.•At high temperatures, the increase in rice husk led to a lower fade resistance.•At high temperatures, medium amounts of rice husk improved wear resistance.•Rice husk shows great potential as reinforcement in brake materials.
Traffic-related emissions include gas and particles that can alter air quality and affect human and environmental health. Limited studies have demonstrated that particulate debris thrown off from ...brakes are toxic to higher plants. The acute phytotoxicity of brake pad wear debris (BPWD) investigated using cress seeds grown in soil contaminated with increasing concentrations of debris. Two types of pads were used: a commercially available phenol based pad and an innovative cement-based pad developed within of the LIFE+ COBRA project. The results suggested that even through the BPWD generated by the two pads were similar in and morphology, debris from traditional pads were more phytotoxic than that from cementitious pads, causing significant alterations in terms of root elongation and loss of plasma membrane integrity.
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•Phytotoxicity of brake pads-derived debris was studied integrating different approaches.•Debris generated by two different pads were analyzed.•FE-SEM and SPES analyses were used to characterize the debris.•Effects on seed germination, root elongation and plasma membrane integrity were evaluated.•Debris from traditional pads are generally more toxic than those from the innovative pads.
High temperature is one of the most basic challenges faced by copper-based brake pads in emergency braking of high-speed railway train. Here, a novel copper-based brake pad was prepared and its ...tribological properties in the temperature ranging of 400–800 °C were studied by pin-on-disc tribometer equipped with heating chamber. The results show that compared with commercial copper-based brake pad, self-designed copper-based brake pad exhibits higher mean friction coefficient and smaller fluctuation of friction coefficient under all test conditions. The friction coefficient of self-designed copper-based brake pad is in the range of 0.35–0.45 at the temperatures up to 600 °C. At 800 °C, the failure mechanism of copper-based brake pad is related to the properties of graphite and copper. Graphite on the friction surface disappears after severe oxidation, resulting in the loss of lubrication of friction interface. Copper undergoes oxidation and softening. Oxidation makes copper unable to promote the formation of stable tribo-film, and the low-strength copper matrix after softening cannot effectively support the friction surface. Therefore, one of the key principles to design high-performance copper-based brake pad is to increase the oxidation resistance of graphite and the high temperature strength of copper matrix.
•A copper-based brake pad with excellent elevated-temperature friction performance was prepared.•The friction performance of copper-based brake pad material fails at 800 °C.•The main failure mechanisms at high temperature include softening and oxidation of copper matrix and oxidation of graphite.
Efforts towards green friction materials Mahale, Vishal; Bijwe, Jayashree; Sinha, Sujeet
Tribology international,
August 2019, 2019-08-00, 20190801, Volume:
136
Journal Article
Peer reviewed
Copper is an outstanding ingredient of friction materials (FMs) due to its multi-functional performance. Despite all its various positive contributions in FMs, it has been recently reported as a ...hazard for an aquatic life and has become a focus of concern for the FM Industry.
Hence in the current work, group of novel ingredients was explored for Cu-replacement. Some conducting ingredients were added to compensate the conductivity of Cu. One more novel ingredient Promaxon-D was used as a theme ingredient.
The developed pads (metal-free) were characterized for tribological properties on the inertia dynamometer as per JASO-C-406 standards. It was concluded that Promaxon-D proved successful in Cu-replacement almost in all respects barring wear. With increase in an amount of Promaxon-D, most of the properties got improved.
•Successful efforts were made to replace Cu (environmental pollutant) in the brake-pads.•Metal-free brake-pads were developed to compete with Cu containing pads.•Hydrated calcium silicate (Promaxon D) proved successful to replace Cu.•Promaxon D outperformed all performance properties except wear.•Higher the amount (0, 5, 10 wt%), more were the benefits.
► NABP maintained stable friction performance as ABP when speed & pressure increased. ► NABP have greater wear resistance than ABP & CMBP materials. ► NABP has the potential braking characteristic ...for a brake pad material.
This work is aimed to study the tribological properties difference of potentially new designed non-commercial brake pad materials with and without asbestos under various speed and nominal contact pressure. The two fabricated non-commercial asbestos brake pad (ABP) and non-asbestos brake pad (NABP) materials were tested and compared with a selected commercial brake pad (CMBP) material using a pin-on-disc tribo-test-rig under dry contact condition. Results showed that friction coefficients for all materials were insensitive to increasing speed and pressure. NABP maintained stable frictional performance as ABP material when contact temperature elevated. Moreover, NABP proved to have greater wear resistance compared to ABP and CMBP materials. Furthermore, the SEM micrographs of brake pad surfaces showed craters which is due to disintegration of plateaus. Finally, the test results indicated that the NABP has the potential braking characteristic for a brake pad material.
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 MoS2 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.
Little is known about the relationship between traffic congestion and antimony (Sb) distribution in street dust, which is essential for Sb control and emission reduction in urban areas. Sb ...concentrations and mass load of the street dust collected in 19 cities of China were determined before investigating the mechanism of traffic influence on Sb distribution through diverse statistical means. The results showed that the Sb concentrations in each city were 1.10–4.76 times higher than the local background values. Sb concentrations in transportation areas were significantly higher than those in residential and industrial areas, and were significantly affected by road network density. The effect of congestion on Sb load of street dust was influenced by vehicle flowrate. Only when the vehicle flowrate was high, the traffic congestion would promote the increase of Sb load obviously. The improved accounting method showed that the Sb dissipation from brake wear in major Chinese cities were higher than that in Stockholm, Sweden, in 2005. The latent path analysis illustrated that a 1% increase in congestion index was correlated with a 0.886% increase in the Sb load. Compared with Switzerland, which has a typical industrialized Sb consumption pattern, China needs to recycle brake pads in addition to taking various measures to alleviate traffic congestion and reduce brake pad wear, despite the fact that the maximum health risk of Sb was far below the safety threshold. This study will provide valuable insights for urban traffic management and brake pad recycling.
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•The effect of congestion index on Sb load of street dust was influenced by vehicle flowrate.•Material flow analysis for Sb dissipation from brake wear was improved pursuant to congestion.•The latent path analysis quantified the relationship between traffic congestion and Sb load.
This research aims at producing and characterizing a low-wear friction lining material using a hybrid mixture of burnt vehicle tyres, pulverized palm kernel shell (PKS), pulverized coconut shell ...(CS), iron and brass filings obtained from the machine shop floor. The Taguchi method was used to determine the optimum parameter settings to obtain a friction lining with a low wear rate by exploring the signal-to-noise ratios (S/N) of the smaller-the-better. The developed friction lining was subjected to the scanning electron microscopy-energy dispersive spectroscopy (SEM-EDX) and X-ray fluorescence (XRF) to ascertain the functional groups present in the friction lining, their elemental composition and finally the morphology. The control factors used in the Taguchi analysis are the moulding temperature, cure time and heat treatment. The optimum parameter settings for a low wear rate were obtained as follows: moulding temperature of 175 °C, cure time of 8 min and heat treatment time of 3 h. The XRF spectroscopy indicated that the developed friction lining materials contained the following compounds in large proportions: CaO, SiO
2
, Al
2
O
3
and Fe
2
O
3
. The SEM-EDX results for the two image scans reported show that carbon and oxygen were the predominant elements observed in the micrograph.
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