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A study of airborne wear particles from automotive disc brakes
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.ORCID iD: 0000-0003-0696-7506
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During braking, both the disc and pads in disc brakes are worn. Since disc brakes are not sealed,some of the wear particles generated can become airborne. Several studies have found anassociation between adverse health effects and the concentration of particles in the atmosphere,so it is of interest to improve our knowledge of the airborne wear particles generated by discbrakes.

This thesis deals with experimental and computational methods focusing on airborne wearparticles from disc brakes. The eight appended papers discuss the possibility to both measure andnumerically determine the concentration and size distribution of airborne wear particles thatoriginate from the pad-to-disc contact. The objective is to increase the scientific knowledge ofairborne wear particles generated from disc brakes.

Papers A, B and C describe tests of disc brake materials conducted in a modified pin-on-discmachine. The results show that the test set-up can be used to measure and rank disc brakematerials with respect to the concentration of airborne particles generated. Ultrafine (nanosized),fine and coarse airborne wear particles that contain metals such as iron, copper and tin werefound.

Papers D and E describe a novel disc brake assembly test stand and tests of disc brake materialsconducted in it. The results show that the test set-up can be used to measure the concentrationand size distribution of airborne wear particles generated from disc brake materials. The resultsalso indicate an ability to rank different pad/disc combinations with respect to the concentrationof airborne wear particles. Furthermore, the results suggest that this test stand can be used tostudy rust layer removal from the disc and that airborne particles are generated even at low brakepressures, such as used to remove dirt from the disc.

Paper F compares measurements made in passenger car field tests with measurements made in adisc brake assembly test stand and in a pin-on-disc machine. A promising correlation between thethree different test methods is found.

Paper G presents and discusses a simulation methodology that numerically determines theconcentration and size distribution of airborne wear particles generated from the pad-to-disccontact in disc brakes by using general-purpose finite element software.

Paper H discusses a cellular automaton model that describes the microscopic contact situationbetween the pad and disc in disc brakes. This model is used to numerically determine the amountof wear that leaves the contact. The results correlate qualitatively with experimental observationsfound in the literature.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 20 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2011:04
Keyword [en]
Disc brakes, Airborne wear particles, Nanoparticles, Cellular automaton
Identifiers
URN: urn:nbn:se:kth:diva-31152ISBN: 978-91-7415-871-7OAI: oai:DiVA.org:kth-31152DiVA: diva2:402912
Public defence
2011-05-27, F3 (Flodissalen), Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110317Available from: 2011-03-17 Created: 2011-03-10 Last updated: 2011-05-24Bibliographically approved
List of papers
1. A pin-on-disc simulation of airborne wear particles from disc brakes
Open this publication in new window or tab >>A pin-on-disc simulation of airborne wear particles from disc brakes
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2010 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 268, no 5-6, 763-769 p.Article in journal (Refereed) Published
Abstract [en]

A novel test method was used to study the concentration and size distribution of airborne wearparticles from disc brake materials. A pin-on-disc tribometer equipped with particle countinginstruments was used as test equipment. Material from four different non-asbestos organic(NAO) pads and four different low metallic (LM) pads were tested against material from greycast iron rotors. The results indicate that the low metallic pads cause more wear to the rotormaterial than the NAO pads, resulting in higher concentrations of airborne wear particles.Although there are differences in the measured particle concentrations, similar size distributionswere obtained. Independent of pad material, the characteristic particle number distributions ofairborne brake wear particles have maxima around 100, 280, 350, and 550 nm.

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
wear, airborne particles, disc brake, pin-on-disc
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-11042 (URN)10.1016/j.wear.2009.11.014 (DOI)000275158000017 ()2-s2.0-74649084522 (ScopusID)
Note

QC 20100824 Uppdaterad från submitted till published (20100824)

Available from: 2009-09-10 Created: 2009-09-10 Last updated: 2016-04-20Bibliographically approved
2. A pin-on-disc study of automotive disc brake materials focusing on airborne wear particles
Open this publication in new window or tab >>A pin-on-disc study of automotive disc brake materials focusing on airborne wear particles
2010 (English)In: Journal of tribology, ISSN 0742-4787Article in journal (Other academic) Submitted
Keyword
airborne wear, ultrafine particles, size distribution, pin-on-disc
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-31149 (URN)
Note
QS 20120316Available from: 2011-03-10 Created: 2011-03-10 Last updated: 2012-03-16Bibliographically approved
3. A pin-on-disc investigation of nanoporous composite-based and conventional brake padmaterials focusing on airborne wear particles
Open this publication in new window or tab >>A pin-on-disc investigation of nanoporous composite-based and conventional brake padmaterials focusing on airborne wear particles
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2011 (English)In: Tribology International, ISSN 0301-679XArticle in journal (Other academic) Submitted
Keyword
airborne wear particles, disc brakes, pin-on-disc
National Category
Mechanical Engineering Materials Engineering
Identifiers
urn:nbn:se:kth:diva-31148 (URN)
Note
QS 20120319Available from: 2011-03-10 Created: 2011-03-10 Last updated: 2012-03-19Bibliographically approved
4. A disc brake test stand for measurement of airborne wear particles
Open this publication in new window or tab >>A disc brake test stand for measurement of airborne wear particles
2009 (English)In: Lubrication Science, ISSN 0954-0075, Vol. 21, no 6, 241-252 p.Article in journal (Refereed) Published
Abstract [en]

During braking, there is wear on both the rotor and the pads. This process generates particles that may becomeairborne. In field tests, it is difficult to distinguish these particles from others in the surrounding environment.Therefore, a laboratory test stand has been designed which allows control of the cleanliness of the surroundingair. The test stand consists of a front right brake assembly mounted in a sealed chamber. A braking load is appliedby a pneumatic system and the rotor, which has been pre-conditioned with a rust layer to simulate a car standingparked overnight in a wet environment, is driven by an electric motor. The number and size of airborne wearparticles are then measured. This experimental set-up has been verified by an initial test series performed at lowbraking loads. The results suggest that this test stand can be used to study rust layer removal from the rotor.

Place, publisher, year, edition, pages
England: John Wiley & Sons, Inc., 2009
Keyword
wear, airborne particles, disc brake, test stand, rust layer
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-11040 (URN)10.1002/ls.87 (DOI)000268086900003 ()2-s2.0-67650841316 (ScopusID)
Note

QC 20100818

Available from: 2009-09-10 Created: 2009-09-10 Last updated: 2016-04-20Bibliographically approved
5. Size, Shape, and Elemental Composition of Airborne Wear Particles from Disc Brake Materials
Open this publication in new window or tab >>Size, Shape, and Elemental Composition of Airborne Wear Particles from Disc Brake Materials
2010 (English)In: Tribology letter, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 38, no 1, 15-24 p.Article in journal (Refereed) Published
Abstract [en]

During braking, both the rotor and pads experience wear, generating particles that may become airborne. In field tests, it is difficult to distinguish these particles from others in the surrounding environment, so it is preferable to use laboratory test stands to study the amount of airborne wear particles generated. The purpose of this work is to investigate the possibility of separate, capture, and analyze airborne wear particles generated by a disc brake in a disc brake assembly test stand. This test stand used allows the cleanliness of the air surrounding the test specimens to be controlled and thus the airborne portion of the wear particles to be studied separately. One pair each of low-metallic (LM) and non-asbestos organic (NAO) brake pads was tested against grey cast iron rotors. Before testing, the elemental contents of the brake materials were analyzed using glow discharge optical emission spectroscopy (GDOES). The concentration and size of airborne wear particles were measured online during testing. In addition, airborne wear particles were collected on filters during the tests and afterward analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The analyzed wear particles contained elements such as iron, titanium, zinc, barium, manganese, and copper. Both the low-metallic and non-asbestos organic type of brake pads tested display a bimodal size distribution with peaks at 280 and 350 nm. Most of the airborne particles generated have a diameter smaller than 2.5 mu m.

Keyword
Wear, Airborne particles, Disc brake, SEM, EDX, GDOES, particulate air-pollution, antimony sources, emission factors, european, cities, abrasion dusts, mortality, pm10, distributions, counters, tailpipe
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-19304 (URN)10.1007/s11249-009-9564-x (DOI)000275463200002 ()2-s2.0-77952672272 (ScopusID)
Note
QC 20110114Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-12-15Bibliographically approved
6. Airborne wear particles from passenger car disc brakes: a comparison of measurements from field tests, a disc brake assembly test stand, and a pin-on-disc machine
Open this publication in new window or tab >>Airborne wear particles from passenger car disc brakes: a comparison of measurements from field tests, a disc brake assembly test stand, and a pin-on-disc machine
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2010 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 224, no J2, 179-188 p.Article in journal (Refereed) Published
Abstract [en]

Most modern passenger cars have disc brakes on the front wheels.Unlike drumbrakes,disc brakes are not sealed off from the ambient air. During braking, both the rotor and the padswear, and this wear process generates particles that may become airborne. In field tests it isdifficult to distinguish these particles from others in the environment. It is thus preferable toconduct tests using laboratory test stands where the cleanness of the surrounding air can becontrolled.However, the validity of results fromthese test stands should be verifiedbycomparisonwith field tests. This article presents a comparison of the number and volume distributions ofairborne wear particles as measured online in field tests, in a disc brake assembly test stand,and in a pin-on-disc machine. In all cases, grey cast iron rotors and low metallic pads weretested. A promising correlation between the three different test methods is shown. The numberandvolume-weighted mean particle diameter for all test methods is about 0.4 and 2–3μm,respectively.

Place, publisher, year, edition, pages
England: Professional Engineering Publishing, 2010
Keyword
wear, airborne particles, disc brake, test stand, field test
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-11041 (URN)10.1243/13506501JET633 (DOI)000275650100006 ()2-s2.0-77249128420 (ScopusID)
Note

QC 20100827

Available from: 2009-09-10 Created: 2009-09-10 Last updated: 2016-04-19Bibliographically approved
7. Simulation of airborne wear particles from disc brakes
Open this publication in new window or tab >>Simulation of airborne wear particles from disc brakes
2009 (English)In: SAE Technical Paper 2009-01-3040, USA: SAE , 2009Conference paper (Refereed)
Abstract [en]

During braking, both the rotor and the pads are worn in disc brakes. This wear process generates particles which may become airborne. In passenger car field tests it is difficult to distinguish these particles from others in the surrounding environment. It may therefore be preferable to use laboratory test stands and/or simulation models to study the amount of airborne wear particles generated. This paper discusses the possibility of predicting the number distribution of airborne wear particles generated from the pad to rotor contact in disc brakes by using general purpose finite element software. A simulation methodology is proposed where the particle coefficient is established by testing at material level. This coefficient is then used in numerical wear simulation at component level. The simulated number distribution is compared to experimental measurements at component level. The result indicates that the proposed methodology may be used to predict the number and distribution of airborne particles generated from the pad to rotor contact.

Place, publisher, year, edition, pages
USA: SAE, 2009
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-11043 (URN)10.4271/2009-01-3040 (DOI)2-s2.0-84877467840 (ScopusID)
Conference
SAE 2009 Brake Colloquium and Exhibition, BRAKE 2009; Tampa, FL; United States; 11 October 2009 through 11 October 2009
Note

QC 20150708

Available from: 2009-09-10 Created: 2009-09-10 Last updated: 2015-07-08Bibliographically approved
8. A cellular automaton approach to numerically simulate the contact situation in disc brakes
Open this publication in new window or tab >>A cellular automaton approach to numerically simulate the contact situation in disc brakes
2011 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 42, no 3, 253-262 p.Article in journal (Refereed) Published
Abstract [en]

Since brake wear is an important contributor to the concentration of airborne particles in urban atmospheres, it is important to increase our understanding of the origin of these particles. The contact situation between the pad and disc is complicated. Metal fibres in the pad (or other hard materials) form stable contact plateaus, which carry the main part of the load. A flow of wear particles in the boundary layer between the pad and disc partially stack up against these plateaus (and increase their area), and some will escape from the contact and become airborne. The purpose of this article is to investigate the possibility to numerically simulate the contact situation in the boundary layer between the pad and disc and the amount of wear that leaves the contact using a cellular automaton approach. To do so, the contact pressure, pad temperature and wear are determined in that order. Based on these results, the creation, growth and destruction of contact plateaus are simulated using a cellular automaton model. Finally, the amount of wear that leaves the contact is determined. The simulated behaviour of the contact situation correlates qualitatively with experimental observations found in the literature.

Keyword
Wear, Disc brake, Cellular automaton
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-31151 (URN)10.1007/s11249-011-9772-z (DOI)000290033400001 ()2-s2.0-79957485953 (ScopusID)
Note

QC 20110317

Available from: 2011-03-10 Created: 2011-03-10 Last updated: 2016-04-19Bibliographically approved

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