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Wahlström, Jens, PhD/DocentORCID iD iconorcid.org/0000-0003-0696-7506
Alternative names
Publications (10 of 50) Show all publications
Lyu, Y., Leonardi, M., Wahlström, J., Gialanella, S. & Olofsson, U. (2020). Friction, wear and airborne particle emission from Cu-free brake materials. Tribology International, 141, Article ID 105959.
Open this publication in new window or tab >>Friction, wear and airborne particle emission from Cu-free brake materials
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2020 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 141, article id 105959Article in journal (Refereed) Published
Abstract [en]

Cu is required to be abated in brake pads due to its toxicity. There are on the market several Cu-free brake pads. These Cu-free brake pads are only evaluated regarding their friction and wear performance, whereas, their airborne particle emissions are not considered. A pin-on-disc tribometer is used to evaluate the friction, wear and airborne particle emission from two Cu-free commercial brake pads used in the Europe. Moreover, a commercial brake pad containing Cu is evaluated as a reference. The results indicate that Cu-free brake pads yield comparable coefficient of friction as the Cu-contained brake pad. All three brake materials result in similar wear to the mating brake rotor. Cu-free brake pads generate more airborne particles than Cu-contained brake pad.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-261640 (URN)10.1016/j.triboint.2019.105959 (DOI)2-s2.0-85072165886 (Scopus ID)
Note

QC 20191011

Available from: 2019-10-09 Created: 2019-10-09 Last updated: 2019-10-16Bibliographically approved
Riva, G., Perricone, G. & Wahlström, J. (2019). A Multi-Scale Simulation Approach to Investigate Local Contact Temperatures for Commercial Cu-Full and Cu-Free Brake Pads. Lubricants, 7(9)
Open this publication in new window or tab >>A Multi-Scale Simulation Approach to Investigate Local Contact Temperatures for Commercial Cu-Full and Cu-Free Brake Pads
2019 (English)In: Lubricants, E-ISSN 2075-4442, Vol. 7, no 9Article in journal (Refereed) Published
Abstract [en]

Copper from vehicles disc brakes is one main contributor of the total copper found in the environment. Therefore, the U.S. Environmental Protection Agency (EPA) and the automotive industries started the Copper-Free Brake Initiative. The pad friction material is essentially composed of a binder, fillers, reinforcing fibres and frictional additives. Copper and brass fibres are the most commonly used fibres in brake pads. There is a need to understand how the contact temperature distribution will change if copper-based fibres are changed to steel fibres. The aim of this work is, therefore, to investigate how this change could influence the local contact temperatures. This is done by developing a multi-scale simulation approach which combines cellular automaton, finite element analysis (FEA) and computational fluid dynamics (CFD) approaches with outputs from inertia brake dyno bench tests of Cu-full and Cu-free pads. FEA and thermal-CFD are used to set the pressure and the temperature boundary conditions of the cellular automaton. The outputs of dyno tests are used to calibrate FEA and CFD simulations. The results of the study show lower peaks in contact temperature and a more uniform temperature distribution for the Cu-free pad friction material.

Place, publisher, year, edition, pages
Basel: MDPI, 2019
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-257956 (URN)10.3390/lubricants7090080 (DOI)000487636200006 ()
Projects
EIT Raw Materials project ECOPADS
Funder
EU, Horizon 2020, 17182
Note

QC 20190918

Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2019-10-11Bibliographically approved
Lyu, Y., Leonardi, M., Ma, J., Wahlström, J., Gialanella, S. & Olofsson, U. (2019). A PIN-ON-DISC STUDY ON THE FRICTION, WEAR AND AIRBORNE PARTICLE EMISSION FROM RECYCLED BRAKE PAD MATERIAL. In: : . Paper presented at Eurobrake 2019.
Open this publication in new window or tab >>A PIN-ON-DISC STUDY ON THE FRICTION, WEAR AND AIRBORNE PARTICLE EMISSION FROM RECYCLED BRAKE PAD MATERIAL
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2019 (English)Conference paper, Published paper (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-254058 (URN)
Conference
Eurobrake 2019
Funder
EU, Horizon 2020, 17182
Note

QC 20190624

Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-06-24Bibliographically approved
Lyu, Y., Bergseth, E., Wahlström, J. & Olofsson, U. (2019). A pin-on-disc study on the tribology of cast iron, sinter and composite railway brake blocks at low temperatures. Wear, 48-52
Open this publication in new window or tab >>A pin-on-disc study on the tribology of cast iron, sinter and composite railway brake blocks at low temperatures
2019 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, p. 48-52Article in journal (Refereed) Published
Abstract [en]

Most freight wagons in the EU use cast iron brake blocks. Cast iron brake blocks have a stable braking capability in different environmental conditions, but wear down the wheel tread quickly. Therefore, there is a need to understand the tribology of other brake block materials. A pin-on-disc tribometer placed in a temperature-controlled chamber is used to investigate the tribology of cast iron, sinter and composite railway brake blocks at low ambient temperatures. Pins made from different brake blocks are tested with discs made from steel wheels. Both friction coefficient and wear are evaluated at five different temperatures from + 10 to − 30 °C. The cast iron block demonstrated the greatest wear at − 10 and − 20 °C, due to the ductile-to-brittle transition at low temperatures. The worn graphite from cast iron is likely to become a solid lubricant, reducing the friction at − 10 and − 20 °C. For the composite brake block, a gradual decrease in friction with decreasing temperature was found. The sinter brake block was not sensitive to changes in ambient temperature. The sliding speed in the current study is relatively low and further study at higher speed is suggested in order to evaluate the tribological performance of different brake blocks.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Brake blocks, Composite, Pin-on-disc, Railway, Temperature, Tribology
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-246451 (URN)10.1016/j.wear.2019.01.110 (DOI)000464582200006 ()2-s2.0-85061381732 (Scopus ID)
Note

QC 20190320

Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2019-05-14Bibliographically approved
Perricone, G., Alemani, M., Wahlström, J. & Olofsson, U. (2019). A proposed driving cycle for brake emissions investigation for test stand. Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering
Open this publication in new window or tab >>A proposed driving cycle for brake emissions investigation for test stand
2019 (English)In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991Article in journal (Refereed) Published
Abstract [en]

Particulate matter emission factors from vehicle brakes are difficult to assess directly from the field. Moreover, there is a lack of a standardized cycle and test stand for evaluating brake emissions. For these reasons, a test cycle was developed from real driving data collected from a car. This new test cycle was implemented on an inertia disc brake dynamometer appositely designed for brake particle emission studies. Results reveal that, for the brake system used as an example, the obtained emission factors for the urban driving conditions studied are comparable to EURO 6 regulations in terms of particle number and comparable to EURO 4 levels in terms of mass with brake emission factors equal to 4.37–6.46 × 1011 particles/km and 44–48 mg/km, respectively.

Place, publisher, year, edition, pages
Sage Publications, 2019
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-254158 (URN)10.1177/0954407019841222 (DOI)2-s2.0-85064091423 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, 324385
Note

QC 20190624

Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-06-24Bibliographically approved
Perricone, G., Matĕjka, V., Alemani, M., Wahlström, J. & Olofsson, U. (2019). A Test Stand Study on the Volatile Emissions of a Passenger Car Brake Assembly. Atmosphere, 10(5), Article ID 263.
Open this publication in new window or tab >>A Test Stand Study on the Volatile Emissions of a Passenger Car Brake Assembly
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2019 (English)In: Atmosphere, ISSN 2073-4433, E-ISSN 2073-4433, Vol. 10, no 5, article id 263Article in journal (Refereed) Published
Abstract [en]

Brake-related airborne particulate matter contributes to urban emissions in the transport sector. Recent research demonstrated a clear dependence of the number of ultra-fine particles on the disc brake temperature. Above the so-called transition temperature, the number of ultra-fine particles increases dramatically (several magnitudes). As for exhaust emissions, part of the emissions released during braking can be in the volatile fraction. For this reason, a disc brake test stand specifically designed for aerosol research was equipped with three different aerosol sampling instruments: (i) a standard cascade impactor, (ii) a cascade impactor operating at high temperature with a heated sampling line, and (iii) a standard cascade impactor with a thermodenuder. Tests with a brake assembly representative of European passenger vehicles were executed, and the concentration of released airborne particles was determined. The results showed a decrease by several magnitudes in the concentration (in the size range of below 200 nm) using the cascade impactor operating at 180 °C with the sampling line heated to 200 °C. A further decrease in the concentration of airborne particles with size fractions below 200 nm was measured using a standard cascade impactor with a thermodenuder heated to 300 °C.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-254155 (URN)10.3390/atmos10050263 (DOI)000472677600037 ()
Funder
EU, FP7, Seventh Framework Programme, 324385
Note

QC 20190624

Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-07-29Bibliographically approved
Riva, G., Valota, G., Perricone, G. & Wahlström, J. (2019). An FEA approach to simulate disc brake wear and airborne particle emissions. Tribology International, 138, 90-98
Open this publication in new window or tab >>An FEA approach to simulate disc brake wear and airborne particle emissions
2019 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 138, p. 90-98Article in journal (Refereed) Published
Abstract [en]

Emissions from disc brake wear adversely affect the air quality in cities. Finite Element Analysis (FEA) approaches focussing on the macroscopic wear of pads and rotors can be found in the literature, but none of these take the wear and emission dependence of the local contact pressure and sliding speed into account. The aim of the present study is to further develop an FEA approach for simulation of macroscopic wear and airborne emission to include the dependences of local contact pressure and sliding speed by implementing wear and emission maps obtained by pin-on-disc tribometer tests. Results from a dyno bench test are compared with simulated results. The simulated rotor and pads wear, and airborne emissions are in line with the measured values.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-254153 (URN)10.1016/j.triboint.2019.05.035 (DOI)000484647200010 ()2-s2.0-85067925087 (Scopus ID)
Funder
EU, Horizon 2020, 636592
Note

QC 20190624

Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-10-01Bibliographically approved
Ma, J., Hedlund-Åström, A., Olofsson, U., Lyu, Y., Leonardi, M. & Wahlström, J. (2019). ECO DESIGN OF BRAKE PADS WITH RECYCLED FRICTION MATERIALS. In: : . Paper presented at Eurobrake 2019.
Open this publication in new window or tab >>ECO DESIGN OF BRAKE PADS WITH RECYCLED FRICTION MATERIALS
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2019 (English)Conference paper, Published paper (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-254061 (URN)
Conference
Eurobrake 2019
Funder
EU, Horizon 2020, 17182
Note

QC 20190624

Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-06-24Bibliographically approved
Riva, G., Perricone, G. & Wahlström, J. (2019). Simulation of Contact Area and Pressure Dependence of Initial Surface Roughness for Cermet-Coated Discs Used in Disc Brakes. Tribology in Industry
Open this publication in new window or tab >>Simulation of Contact Area and Pressure Dependence of Initial Surface Roughness for Cermet-Coated Discs Used in Disc Brakes
2019 (English)In: Tribology in Industry, ISSN 0354-8996Article in journal (Refereed) Published
Abstract [en]

Friction, wear, and emission performance strongly depend on the contact pressure and area at the interface of the pad and disc. The contact situation at the pad-to-disc interface can be explained by the formation and destruction of mesoscopic sized contact plateaus on the pad surface. Experimental studies report that the initial surface roughness of cermet-coated discs strongly affects friction, wear and emission performance. This is explained by the formation of secondary plateaus on the disc surface. The aim of this work is to extend an existing cellular automaton approach to include the formation of secondary plateaus on the disc surface in order to explain experimental results reported in the literature. First, to investigate the validity of the novel simulation approach, a cermet-coated cast iron disc is tested against a low-met pad material with a pin-on-disc tribometer. The same conditions are used as input in a simulation. Then, the initial disc roughness influence on contact pressure and area of the same cermet-coated disc is compared with results reported in the literature. The topographies of the measured and simulated disc surfaces are qualitatively in line. An initial rougher disc surface results in a considerably lower contact area than does a smother surface.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-254159 (URN)10.24874/ti.2019.41.01.01 (DOI)2-s2.0-85064138859 (Scopus ID)
Funder
EU, Horizon 2020, 636592
Note

QC 20190624

Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-06-24Bibliographically approved
Tu, M., Cha, Y., Wahlström, J. & Olofsson, U. (2019). Towards a two-part train traffic emissions factor model for airborne wear particles. Transportation Research Part D: Transport and Environment, 67, 67-76
Open this publication in new window or tab >>Towards a two-part train traffic emissions factor model for airborne wear particles
2019 (English)In: Transportation Research Part D: Transport and Environment, ISSN 1361-9209, E-ISSN 1879-2340, Vol. 67, p. 67-76Article in journal (Refereed) Published
Abstract [en]

In 2017 a new railway tunnel containing two stations opened in Stockholm, Sweden. A series of field measurements were carried out on the platforms in this tunnel before and after it was opened for normal traffic. These measurements were used to investigate the contribution of airborne particle emissions from wear processes to total train emissions. This field data was used to develop a two-part train traffic emission factor model for PM10. The two parts are the accumulative effect term (relating to operating distance such as wheel-rail contact and overhead electric line sliding contact) and a brake effect term (relating to the number of braking operations such as brake disc and brake pad contact). The results show that operating a single trial train at a higher than normal frequency on an otherwise empty platform increases the platform particulate concentration until the concentration reaches a steady value. The model suggests that brake emissions account for about 50% of the total emissions measured in the tunnels.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Airborne particle, Emission factor, Railway tunnel, Wear particle emission, Brakes, Electric lines, Railroads, Rails, Wear of materials, Emission factors, Field measurement, Overhead electric lines, Railway tunnels, Stockholm, Sweden, Wear particles, Wheel-rail contacts, Railroad tunnels, atmospheric pollution, concentration (composition), emission inventory, particulate matter, quantitative analysis, railway transport, traffic emission, wear, Stockholm [Stockholm (CNT)], Stockholm [Sweden], Sweden
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-248230 (URN)10.1016/j.trd.2018.11.006 (DOI)000464890900005 ()2-s2.0-85056898654 (Scopus ID)
Note

QC 20190411

Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2019-05-13Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0696-7506

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