| 1. |
- Jansson, Anders, et al.
(author)
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Ultrafine Particle Formation from Wear
- 2010
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In: The International Journal of Ventilation. - : Informa UK Limited. - 1473-3315 .- 2044-4044. ; 9:1, s. 83-88
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Journal article (peer-reviewed)abstract
- Much attention is given to the consequences of airborne particles on human health and well-being. Wear is one source of airborne particles and contributions in the urban environments from wheel-to-rail contacts and disc brakes cannot be neglected. Traditionally, mechanical wear has been associated with the generation of particles of diameters of some microns. However, the research described has found ultrafine particle generation from wear processes. Particle generation from wear was measured under controlled laboratory conditions. The wear was created through sliding contact in a tribometer (type "pin-on-disc") with different materials and with different sliding velocities and pressures, to represent rail traffic and automobile disc braking. Particle concentrations and size distributions in the air were determined for particle diameters from 10 nm up to more than 10 mu m. For most materials and conditions three particle size modes were found: one at 50-100 nm, one at a few hundred nm and one at a few mu m particle diameter.
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| 2. |
- Wahlström, Jens, et al.
(author)
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A pin-on-disc simulation of airborne wear particles from disc brakes
- 2010
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In: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 268:5-6, s. 763-769
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Wahlström, Jens, et al.
(author)
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A cellular automaton approach to numerically simulate the contact situation in disc brakes
- 2011
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In: Tribology letters. - : Springer Science and Business Media LLC. - 1023-8883 .- 1573-2711. ; 42:3, s. 253-262
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Journal article (peer-reviewed)abstract
- 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.
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| 4. |
- Wahlström, Jens, et al.
(author)
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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
- 2010
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In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - England : Professional Engineering Publishing. - 1350-6501 .- 2041-305X. ; 224:J2, s. 179-188
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Journal article (peer-reviewed)abstract
- Most modern passenger cars have disc brakes on the front wheels. Unlike drum brakes, disc brakes are not sealed off from the ambient air. During braking, both the rotor and the pads wear, and this wear process generates particles that may become airborne. In field tests it is difficult to distinguish these particles from others in the environment. It is thus preferable to conduct tests using laboratory test stands where the cleanness of the surrounding air can he controlled. However, the validity of results from these test stands Should be verified by comparison with field tests. This article presents a comparison of the number and Volume distributions of airborne 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 were tested. A promising correlation between the three different test methods is shown. The number- and volume-weighted mean particle diameter for all test methods is about 0.4 and 2-3 mu m, respectively.
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