| 1. |
- Alemani, Mattia, et al.
(författare)
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A study on emission of airborne wear particles from car brake friction pairs
- 2015
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Ingår i: SAE International Journal of Materials & Manufacturing. - : SAE International. - 1946-3979 .- 1946-3987. ; 9:1, s. 147-157
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Tidskriftsartikel (refereegranskat)abstract
- The emission of airborne wear particles from friction material / cast iron pairs used in car brakes was investigated, paying special attention to the influence of temperature. Five low-metallic materials and one non-asbestos organic material were tested using a pin-on-disc machine. The machine was placed in a sealed chamber to allow airborne particle collection. The concentration and size distribution of 0.0056 to 10 μm particles were obtained by a fast mobility particle sizer and an optical particle sizer. The temperature was measured by a thermocouple installed in the disc. The experiments show that as the temperature increases from 100 to 300 °C the emission of ultrafine particles intensifies while that of coarse particles decreases. There is a critical temperature at which the ultrafine particle emission rate rises stepwise by 4 to 6 orders of magnitude. For the friction pairs investigated, the critical temperature was found to be between 165 and 190 °C. Below the critical temperature, fine particles outnumber coarse and ultrafine particles, although coarse particles make up the bulk of the particulate matter mass. The friction pairs differ in the ultrafine particle emission rate by 1 to 2 orders of magnitude. Above the critical temperature, ultrafine particles constitute almost 100% of the total particle number and their relative mass contribution can exceed 50%. Analysis of the particle size distributions revealed peaks at 0.19-0.29, 0.9 and 1.7 μm. Above the critical temperature, one more peak appears in the ultrafine particle range at 0.011-0.034 μm.
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| 2. |
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| 3. |
- Alemani, Mattia, et al.
(författare)
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Dry sliding of a low steel friction material against cast iron at different loads : Characterization of the friction layer and wear debris
- 2017
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 376-377, s. 1450-1459
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Tidskriftsartikel (refereegranskat)abstract
- Pin-on-disc testing was used to investigate the sliding behavior and the wear products of a low-steel friction material against a cast iron disc at different applied loads, to investigate the effect of the temperature rise induced by frictional heating. The testing rig was operated in a clean chamber with a purified incoming air flux. The outgoing flux carries the wear particles to an impactor that counted and sorted them by average diameter and weight. At increasing applied loads, corresponding to a proportional increase of the pin-disc contact temperature, the coverage of both the pin and disc surface by a friction layer was found to increase too. The relevant X-Ray diffraction patterns revealed the presence of a large amount of graphite and different compounds originating from the friction material and from the counterface disc, mainly iron oxides, as concerns this latter. After the test at the lowest investigated load, i.e., 1 kg, the disc worn surface exhibited abrasive grooves and a discontinuous friction layer mainly made of compacted iron oxide particles. After the test at higher loads, i.e., 5 and 7 kg, the disc surface was covered by a compact friction layer. As concerns the friction layer on the pins, most of the ingredients from the friction material were detected, in association with the iron oxides from the disc. These results can be interpreted in terms of the temperature stability range of the phenolic resin used as a binder of the friction material. The characterization of the collected airborne wear debris showed that the particles produced by the low temperature (i.e., low load) test were mostly equiaxed; whereas those produced by the high temperature (i.e., high loads) tests, predominantly displayed a plate-like morphology. The mechanisms of their formation in relation to the characteristics of the friction layers are illustrated and discussed.
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| 4. |
- Alemani, Mattia, et al.
(författare)
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Dry sliding of a low steel friction material against cast iron at different loads: characterization of the friction layer and wear debris
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Pin-on-disc testing was used to investigate the sliding behavior and the wear products of a low-steel friction material against a cast iron disc at different applied loads, to investigate the effect of the temperature rise induced by frictional heating. The testing rig was operated in a clean chamber with a purified incoming air flux. The outgoing flux carries the wear particles to an impactor that counted and sorted them by average diameter and weight. At increasing applied loads, corresponding to a proportional increase of the pin-disc contact temperature, the coverage of both the pin and disc surface by a friction layer was found to increase too. The relevant X-Ray diffraction patterns revealed the presence of a large amount of graphite and different compounds originating from the friction material and from the counterface disc, mainly iron oxides, as concerns this latter. After the test at the lowest investigated load, i.e., 1 kg, the disc worn surface exhibited abrasive grooves and a discontinuous friction layer mainly made of compacted iron oxide particles. After the test at higher loads, i.e., 5 and 7 kg, the disc surface was covered by a compact friction layer. As concerns the friction layer on the pins, most of the ingredients from the friction material were detected, in association with the iron oxides from the disc. These results can be interpreted in terms of the temperature stability range of the phenolic resin used as a binder of the friction material. The characterization of the collected airborne wear debris showed that the particles produced by the low temperature (i.e., low load) test were mostly equiaxed; whereas those produced by the high temperature (i.e., high loads) tests, predominantly displayed a plate-like morphology. The mechanisms of their formation in relation to the characteristics of the friction layers are illustrated and discussed.
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| 5. |
- Alemani, Mattia, et al.
(författare)
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ON THE INFLUENCE OF CAR BRAKE SYSTEM PARAMETERS ON PARTICULATE MATTER EMISSIONS
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The influence of car brake system parameters on particulate matter emissions was investigated using a pin-on-disc tribometer. Samples from a low-steel friction material and a cast iron disc were tested for different sliding velocities, nominal contact pressures and frictional powers. Disc temperatures were also measured. Their impact on total concentration, size distribution, particle coefficient and transition temperature was analysed. Results show that frictional power is the most significant brake system parameter. However, temperature, as a response parameter, is the most influential, inducing a shift towards the ultrafine particulate fraction and raising emissions. A transition temperature, independent of the system parameters, was identified.
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| 6. |
- Alemani, Mattia, et al.
(författare)
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On the influence of car brake system parameters on particulate matter emissions
- 2018
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Ingår i: Wear. - : ELSEVIER SCIENCE SA. - 0043-1648 .- 1873-2577. ; 396, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- The influence of car brake system parameters on particulate matter emissions was investigated using a pin-on-disc tribometer. Samples from a low-steel friction material and a cast iron disc were tested for different sliding velocities, nominal contact pressures and frictional powers. Disc temperatures were also measured. Their impact on total concentration, size distribution, particle coefficient and transition temperature was analysed. Results show that frictional power is the most significant brake system parameter. However, temperature, as a response parameter, is the most influential, inducing a shift towards the ultrafine particulate fraction and raising emissions. A transition temperature, independent of the system parameters, was identified.
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| 7. |
- Alemani, Mattia
(författare)
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On the scaling effects of measuring disc brake airborne particulate matter emissions – a comparison of a pin-on-disc tribometer and an inertia dynamometer bench under dragging conditions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- An important contributor to non-exhaust emissions in urban areas is airborne particulate matter originating from brake systems. A well-established way to test such systems in industry is to use Inertia dynamometer benches; although they are quite expensive to run. Pin-on-disc tribometers, on the other hand, are relatively cheap to run, but simplify the real system. The literature indicates promising correlations between these two test stands with regard to measured airborne number distribution. Recent studies also show a strong dependency between the airborne number concentration and the disc temperature. However, a direct comparison that also takes into account temperature effects is missing. The aim of this paper is, therefore, to investigate how the transition temperature is affected by the different test scales, under dragging conditions, and the effects on total concentration and size distribution. New and used low-steel pins/pads were tested against cast iron discs/rotors on both the aforementioned test stands, appositely designed for particulate emission studies. A constant normal load and constant rotational velocity were imposed in both test stands. Results show that a transition temperature can always be identified. However, it is influenced by the test scale and the frictional pair status. Nevertheless, emissions are assessed similarly when an equivalent frictional pair status is analysed (e.g. run-in). Further investigations for fully run-in samples on the pin-on-disc should be performed in order to finally assess the possibility of using the tribometers for the initial assessment of different friction materials.
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| 8. |
- Alemani, Mattia
(författare)
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Particle emissions from car brakes : The influence of contact conditions on the pad-to-rotor interface
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to their adverse health effects emissions have been regulated for over three decades. Brake wear particulate matter is the most important non-exhaust source, however current knowledge is mainly limited to observational studies. This thesis aims to investigate relations between the brake system contact conditions and the related emissions on a model scale; validate the results on a component level; and understand to what extent they are significant on a full-scale.Paper A investigates the influence of nominal contact pressure on a model scale. Results show that higher pressure corresponds to higher emissionsPaper B investigates the influence of the nominal contact pressure, for different friction materials, on a model scale. A temperature threshold, responsible for a relevant emission increase, is identified.Paper C investigates particle characteristics and wear mechanisms for different nominal contact pressures, on a model scale. Results show an enhanced tribo-layer at higher pressure levels.Paper D investigates the influence of brake system conditions on emissions, on a model scale. Results show that frictional power is the most important parameter. A transition temperature independent of the contact condition is identified.Paper E investigates similarities occurring on a component scale and a model scale in terms of emissions. Results show a promising correlation, and the possibility of using a pin-on-disc tribometer for R&D activities.Paper F investigates analogies occurring on a component scale and a model scale, in terms of friction performance, fictional surface and chemical composition. Results show similar phenomena occurring for the two test stands.Paper G analyses real brake system working conditions in a urban environment defining, by means of an inertia dyno bench, the related emissions. Results reveal emission factors compliant to EURO6 and EURO2 regulations, in terms of number and mass, respectively.
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| 9. |
- Alemani, Mattia, et al.
(författare)
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Scaling effects of measuring disc brake airborne particulate matter emissions – A comparison of a pin-on-disc tribometer and an inertia dynamometer bench under dragging conditions
- 2018
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Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : Sage Publications. - 1350-6501 .- 2041-305X. ; 232:12, s. 1538-1547
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Tidskriftsartikel (refereegranskat)abstract
- An important contributor to non-exhaust emissions in urban areas is airborne particulate matter originating from brake systems. A well-established way to test such systems in industry is to use inertia dynamometer benches; although they are quite expensive to run. Pin-on-disc tribometers, on the other hand, are relatively cheap to run, but simplify the real system. The literature indicates promising correlations between these two test stands with regard to measured airborne number distribution. Recent studies also show a strong dependency between the airborne number concentration and the disc temperature. However, a direct comparison that also takes into account temperature effects is missing. The aim of this paper is, therefore, to investigate how the transition temperature is affected by the different test scales, under dragging conditions, and the effects on total concentration and size distribution. New and used low-steel pins/pads were tested against cast iron discs/rotors on both the aforementioned test stands, appositely designed for particulate emission studies. A constant normal load and constant rotational velocity were imposed in both test stands. Results show that a transition temperature can always be identified. However, it is influenced by the test scale and the frictional pair status. Nevertheless, emissions are assessed similarly when an equivalent frictional pair status is analysed (e.g. run-in). Further investigations for fully run-in samples on the pin-on-disc should be performed in order to finally assess the possibility of using the tribometers for the initial assessment of different friction materials.
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| 10. |
- Matějka, Vlastimil, et al.
(författare)
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Dependency of PM10 particle emission on stability of friction coefficient and character of friction surface
- 2016
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Konferensbidrag (refereegranskat)abstract
- Two pairs of low-metallic brake pads (BP1 and BP2) with different chemical composition as measured using wave dispersive X-ray fluorescence spectroscopy were selected for this study. The brake pads were tested with inertia brake dynamometer adapted for isokinetic sampling of PM10 wear particles. Modified SAE J2707 (part B) testing procedure was used for both test. PM10 particles released during the brake stops were captured under isokinetic conditions on 47mm quartz filter, the particles bigger than 10 micron were removed by PM10 cyclone. The character of the friction surface of brake pads was studied using scanning electron microscopy. It was observed that COF of sample BP1 grows during the individual brake events from approx. 0.4 to 0.7; while the COF obtained for BP2 shows stable value approx. 0.4 during individual brake stops. The average PM10 concentration in given experimental set-up reached value 1.47 and 0.56 mg/m3 for sample BP1 and BP2, respectively.
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