A field test study of airborne wear particles from a running regional train

Abbasi, S.; Olander, L.; Larsson, C.; Olofsson, U.; Jansson, A.; Sellgren, U.
2012 | Proc Inst Mech Eng G J Aerosp Eng | 226 (95-109)

Inhalable airborne particles have inverse health effects. In railways, mechanical brakes, the wheel–rail contact, current collectors, ballast, sleepers, and masonry structures yield particulate matter. Field tests examined a Swedish track using a train instrumented with particle measurement devices, brake pad temperature sensors, and speed and brake sensors. The main objective of this field test was to study the characteristics of particles generated from disc brakes on a running train with an on-board measuring set-up. Two airborne particle sampling points were designated, one near a pad–rotor disc brake contact and a second under the frame, not near a mechanical brake or the wheel–rail contact; the numbers and size distributions of the particles detected were registered and evaluated under various conditions (e.g. activating/deactivating electrical brakes or negotiating curves). During braking, three speed/temperature-dependent particle peaks were identified in the fine region, representing particles 280, 350, and 600 nm in diameter. In the coarse region, a peak was discerned for particles 3–6 µm in diameter. Effects of brake pad temperature on particle size distribution were also investigated. Results indicate that the 280-nm peak increased with increasing temperature, and that electrical braking significantly reduced airborne particle numbers. Field emission scanning electron microscope images captured particles sizing down to 50 nm. The inductively coupled plasma mass spectrometry results indicated that Fe, Cu, Zn, Al, Ca, and Mg were the main elements constituting the particles.

A pin-on-disc study of the rate of airborne wear particle emissions from railway braking materials

Abbasi, S.; Jansson, A.; Olander, L.; Olofsson, U.; Sellgren, U.
2012 | Wear | 284-285 (18-29)

The current study investigates the characteristics of particles generated from the wear of braking materials, and provides an applicable index for measuring and comparing wear particle emissions. A pin-on-disc tribometer equipped with particle measurement instruments was used. The number concentration, size, morphology, and mass concentration of generated particles were investigated and reported for particles 10 nm–32 μm in diameter. The particles were also collected on filters and investigated using EDS and SEM. The effects of wear mechanisms on particle morphology and changes in particle concentration are discussed. A new index, the airborne wear particle emission rate (AWPER), is suggested that could be used in legislation to control non-exhaust emissions from transport modes, particularly rail transport.

Ultrafine Particle Formation from Wear

Jansson, A.; Olander, L.; Olofsson, U.; Sund, J.; Söderberg, A.; Wahlström, J.
2010 | Int. J. Vent. | 9 (1) (83-88)

Much attention is given to the consequences of airborne particles on human health and wellbeing. 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 μm. 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 μm
particle diameter.

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

Wahlström, J.; Söderberg, A.; Olander, L.; Olofsson, U.; Jansson, A.

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 be 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 μ m, respectively.

A pin-on-disc simulation of airborne wear particles from disc brakes

Wahlström, J.; Söderberg, A.; Olander, L.; Jansson, A.; Olofsson, U.;
2010 | Wear | 268 (763-769)

A novel test method was used to study the concentration and size distribution of airborne wear particles from disc brake materials. A pin-on-disc tribometer equipped with particle counting instruments 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 grey cast iron rotors. The results indicate that the low metallic pads cause more wear to the rotor material than the NAO pads, resulting in higher concentrations of airborne wear particles. Although there are differences in the measured particle concentrations, similar size distributions were obtained. Independent of pad material, the characteristic particle number distributions of airborne brake wear particles have maxima around 100, 280, 350, and 550 nm.

Ultrafeine Partikelbildung durch mechanische Abnutzung

Jansson, A.; Olander, L.; Olofsson, U.

Institutetreffen 2009 | September 18, 2019

Towards a model for the number of airborne particles generated from a sliding contact

Olofsson, U.; Olander, L.; Jansson, A.
2009 | Wear

Wear rate testing in relation to airborne particles generated in a wheel-rail contact

Sundh, J.; Olofsson, U.; Olander, L.; Jansson, A.

A Study of Airborne Wear Particles Generated From a Sliding Contact

Olofsson, U.; Olander, L.; Jansson, A.

Recently, much attention has been paid to the influence of airborne particles in the atmosphere on human health. Sliding contacts are a significant source of airborne particles in urban environments. In this study airborne particles generated from a sliding steel-on-steel combination are studied using a pin-on-disk tribometer equipped with airborne-particle counting instrumentation. The instrumentation measured particles in size intervals from 0.01 mu m to 32 mu m. The result shows three particle size regimes with distinct number peaks: ultrafine particles with a size distribution peak around 0.08 mu m, fine particles with a peak around 0.35 mu m, and coarse particles with a peak around 2 or 4 mu m. Both the particle generation rate and the wear rate increase with increasing sliding velocity and contact pressure.

Ultrafine particle formation from wear.

Jansson, A.; Olander, L.; Olofsson, U.; Sund, J.; Söderberg, A.; Wahlström, J.
2009 | Report No: 1038

Airborne particle generation at metal wear

Jansson, A.; Olander, L.; Olofsson, U.; Sund, J.; Söderberg, A.; Wahlström, J.

NOSA 2009 | September 18, 2019

Airborne Wear Particles from Disc Brakes: a Comparison of Measurements from Cars, Test Stands and Material Tests

Olofsson, U.; Wahlström, J.; Söderberg, A.; Olander, L.; Jansson, A.

IMechE Tribology 2008 | September 18, 2019

  • Page 1 of 2
  • 1
  • 2

Contact information

Visiting addresses:

Geovetenskapens Hus,
Svante Arrhenius väg 8, Stockholm

Arrheniuslaboratoriet, Svante Arrhenius väg 16, Stockholm (Unit for Analytical and Toxicological Chemistry)

Mailing address:
Department of Environmental Science and Analytical Chemistry (ACES)
Stockholm University
106 91 Stockholm

Press enquiries should be directed to:

Stella Papadopoulou
Science Communicator
Phone +46 (0)8 674 70 11