Effects of reinforcing fibers on airborne particle emissions from brake pads

Song, Wansu; Park, Jong‐Sung; Choi, Jinsoo; Lee, Jung Ju; Jang, Hae‐Dong

doi:10.1016/j.wear.2021.203996

Cited by 20 publications

(9 citation statements)

References 31 publications

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“…Song et al [12] have stated the strong, proportional relationship between the mass concentrations and the number of airborne PM with the wear rate of brake pads and discs. Nogueira et al [13] demonstrated that the PM emissions mainly consist of the disrupted friction layer that is dynamically forming during the testing duration from the compaction of the wear debris, with a substantial contribution from the cast iron counterface disc.…”

Section: Introductionmentioning

confidence: 99%

Dry Sliding Behavior and Particulate Emissions of a SiC-graphite Composite Friction Material Paired with HVOF-Coated Counterface

et al. 2022

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Dry sliding wear tests and corresponding particulate matter (PM) analysis were conducted on a newly developed SiC-graphite-based composite friction material, paired with two types of HVOF counterface/discs: WC-CoCr and WC-FeCrAlY coatings, with a conventional martensitic stainless steel counterface as a reference. The trials were conducted on a pin-on-disc testing equipment at room temperature and a constant sliding velocity and contact pressure of 7 m/s and 0.5 MPa, respectively. The coefficient of friction (CoF) curves with the uncoated disc exhibited considerable fluctuations. On the other hand, the coated discs featured an increase in the CoF at the beginning of the tests, followed by either a continuous reduction until the end of the testing duration or the attainment of a steady state regime. The pin wear and emissions with both coatings were appreciably lower when compared to the trials with the uncoated disc. The evaluation of the friction layer observed a significant contribution of the counterface for all the pairings. The PM analysis was conducted on the particles that were lying in the range of 10 μm and 2.5 μm on a scanning electron microscope (SEM), and particles from 2.5 μm and 1 μm on transmission electron microscope (TEM), with an emphasis on the particles that were detached from the pin surface and friction layer to explain the wear mechanisms for each pairing. Through this, the need for the proper selection of both friction material and counterface to avoid the emission of harmful compounds in the environment was highlighted.

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Section: Introductionmentioning

confidence: 99%

Dry Sliding Behavior and Particulate Emissions of a SiC-graphite Composite Friction Material Paired with HVOF-Coated Counterface

et al. 2022

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“…The use of steel fibers is known to improve the performance of several aspect of brake pads such as helping to remove heat from the contact interface [5,6] and creating primary contact plateaus [7,8]. Although several studies have reported that introducing steel fibers or increasing their content led to high wear of the contact [9][10][11], other studies have shown mixed results regarding this matter [6,12,13]. Non-metal NAO formulations are often limited to low or moderate temperature use, due to the degradation of the organic resin matrix and aramid fibers which happens between 200 and 600 • C [14][15][16][17].…”

mentioning

confidence: 99%

Differences in Wear and Material Integrity of NAO and Low-Steel Brake Pads under Severe Conditions

et al. 2021

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In this study, through severe reduced-scale braking tests, we investigate the wear and integrity of organic matrix brake pads against gray cast iron (GCI) discs. Two prototype pad materials are designed with the aim of representing a typical non-metal NAO and a low-steel (LS) formulation. The worn surfaces are observed with SEM. The toughness of the pad materials is tested at the raw state and after a heat treatment. During braking, the LS-GCI disc configuration produces heavy wear. The friction parts both keep their macroscopic integrity and wear appears to be homogeneous. The LS pad is mostly covered by a layer of solid oxidized steel. The NAO-GCI disc configuration wears dramatically and cannot reach the end of the test program. The NAO pad suffers many deep cracks. Compacted third body plateaus are scarce and the corresponding disc surface appears to be very heterogeneous. The pad materials both show similar strength at the raw state and similar weakening after heat treatment. However, the NAO material is much more brittle than the LS material in both states, which seems to favor the growth of cracks. The observations of crack faces suggest that long steel fibers in the LS material palliate the brittleness of the matrix, even after heat damage.

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“…1 A and B ) for this pad formulation. These differences in particle generation and charged aerosol properties between the two brake pad types are likely due to morphological differences on the brake pad surface ( 45 ) as well differences in composition, specifically in metals ( 46 ). Differences in the electronic work functions of the materials used in each brake pad could drive differences in the amount of charge that accumulates on the pad surface.…”

Section: Resultsmentioning

confidence: 99%

Automotive braking is a source of highly charged aerosol particles

Thomas,

Bauer,

Dam

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

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Although the last several decades have seen a dramatic reduction in emissions from vehicular exhaust, nonexhaust emissions (e.g., brake and tire wear) represent an increasingly significant class of traffic-related particulate pollution. Aerosol particles emitted from the wear of automotive brake pads contribute roughly half of the particle mass attributed to nonexhaust sources, while their relative contribution to urban air pollution overall will almost certainly grow coinciding with vehicle fleet electrification and the transition to alternative fuels. To better understand the implications of this growing prominence, a more thorough understanding of the physicochemical properties of brake wear particles (BWPs) is needed. Here, we investigate the electrical properties of BWPs as emitted from ceramic and semi-metallic brake pads. We show that up to 80% of BWPs emitted are electrically charged and that this fraction is strongly dependent on the specific brake pad material used. A dependence of the number of charges per particle on charge polarity and particle size is also demonstrated. We find that brake wear produces both positive and negative charged particles that can hold in excess of 30 elementary charges and show evidence that more negative charges are produced than positive. Our results will provide insights into the currently limited understanding of BWPs and their charging mechanisms, which potentially have significant implications on their atmospheric lifetimes and thus their relevance to climate and air quality. In addition, our study will inform future efforts to remove BWP emissions before entering the atmosphere by taking advantage of their electric charge.

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Effects of reinforcing fibers on airborne particle emissions from brake pads

Cited by 20 publications

References 31 publications

Dry Sliding Behavior and Particulate Emissions of a SiC-graphite Composite Friction Material Paired with HVOF-Coated Counterface

Dry Sliding Behavior and Particulate Emissions of a SiC-graphite Composite Friction Material Paired with HVOF-Coated Counterface

Differences in Wear and Material Integrity of NAO and Low-Steel Brake Pads under Severe Conditions

Automotive braking is a source of highly charged aerosol particles

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