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Lyu, Y., Bergseth, E., Tu, M. & Olofsson, U. (2018). Effect of humidity on the tribological behaviour and airborne particle emissions of railway brake block materials. Tribology International, 118, 360-367.
Open this publication in new window or tab >>Effect of humidity on the tribological behaviour and airborne particle emissions of railway brake block materials
2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 118, 360-367 p.Article in journal (Refereed) Published
Abstract [en]

A pin-on-disc tribometer placed in a one-way ventilated chamber was used to investigate the effect of relative humidity on the tribology and airborne particle emission of three commercial railway brake block materials (grey cast iron, organic composite, and sintered). Cast iron showed the highest friction coefficient, particle emission and wear loss and organic composite exhibited the lowest. The generation of oxide layers on the worn cast iron surface resulted in a decrease in friction, particle emission and wear. Moisture adsorption by the organic composite leads to decreased friction coefficient and particle emission with increasing humidity. Relative humidity does not affect the friction coefficient of the sintered brake block, whose particle emission and wear loss significantly decline with increasing relative humidity.

Place, publisher, year, edition, pages
Elsevier, 2018
Keyword
Airborne particles, Brake block, Humidity, Pin-on-disc
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-218916 (URN)10.1016/j.triboint.2017.10.011 (DOI)2-s2.0-85032008346 (Scopus ID)
Note

QC 20171201

Available from: 2017-12-01 Created: 2017-12-01 Last updated: 2018-01-13Bibliographically approved
Li, X. & Olofsson, U. (2017). A study on friction and wear reduction due to porosity in powder metallurgic gear materials. Tribology International, 110, 86-95.
Open this publication in new window or tab >>A study on friction and wear reduction due to porosity in powder metallurgic gear materials
2017 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 110, 86-95 p.Article in journal (Refereed) Published
Abstract [en]

It has been widely acknowledged that controlled texturing on a surface can contribute to friction and wear reduction at lubricated sliding contact interfaces. This paper investigates the influence on friction and wear of different pore size distributions of powder metallurgy gear materials. The pore sizes are controlled by different densities of the powder metallurgic materials. Two different kinds of powder metallurgy (PM) gear materials were applied and a standard gear material are used as a reference. The friction and wear coefficients of PM materials sliding on PM materials increase with increasing pore size. The friction and wear coefficients of regular steel sliding on PM materials decrease with increasing pore size. No matter what the material of the disc, peeling is one of the main damage mechanisms of powder metallurgy pins with the biggest porosity.

Place, publisher, year, edition, pages
Elsevier, 2017
Keyword
Powder metallurgy gear material, Pore size, Friction, Wear
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-206671 (URN)10.1016/j.triboint.2017.02.008 (DOI)000398871700010 ()2-s2.0-85013213277 (Scopus ID)
Note

QC 20170510

Available from: 2017-05-10 Created: 2017-05-10 Last updated: 2017-05-10Bibliographically approved
Andersson, M., Sosa, M. & Olofsson, U. (2017). Efficiency and temperature of spur gears using spray lubrication compared to dip lubrication. Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, 231(11), 1390-1396.
Open this publication in new window or tab >>Efficiency and temperature of spur gears using spray lubrication compared to dip lubrication
2017 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 231, no 11, 1390-1396 p.Article in journal (Refereed) Published
Abstract [en]

Increased machine efficiency is a requirement in today's world and geared transmissions are no exception. A back-to-back gear test rig was used to compare dip lubrication with spray lubrication regarding gearbox efficiency, mesh efficiency, gear temperature and surface roughness. Gears lubricated at the inlet of the mesh show a lower measured temperature when compared to spray lubrication at the outlet of the mesh. Spray lubrication, when compared to dip lubrication, yields the same efficiency for both rotating directions at the tested speeds of 0.5 to 20 m/s. Spray lubrication shows a significantly higher total gearbox efficiency at higher speeds, higher measured tooth temperature and no measurable change in surface roughness.

Place, publisher, year, edition, pages
SAGE PUBLICATIONS LTD, 2017
Keyword
Spray lubrication, gear efficiency, gear temperature, surface roughness
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-217940 (URN)10.1177/1350650117695709 (DOI)000414663700002 ()2-s2.0-85033232258 (Scopus ID)
Note

QC 20171121

Available from: 2017-11-21 Created: 2017-11-21 Last updated: 2017-11-24Bibliographically approved
Nosko, O., Vanhanen, J. & Olofsson, U. (2017). Emission of 1.3–10 nm airborne particles from brake materials. Aerosol Science and Technology, 51(1), 91-96.
Open this publication in new window or tab >>Emission of 1.3–10 nm airborne particles from brake materials
2017 (English)In: Aerosol Science and Technology, ISSN 0278-6826, E-ISSN 1521-7388, Vol. 51, no 1, 91-96 p.Article in journal (Refereed) Published
Abstract [en]

Operation of transport vehicle brakes makes a significant contribution to airborne particulate matter in urban areas, which is subject of numerous studies due to the environmental concerns. We investigated the presence and number fractions of 1.3–10 nm airborne particles emitted from a low-metallic car brake material (LM), a non-asbestos organic car brake material (NAO) and a train brake cast iron against a cast iron. Particles were generated by a pin-on-disc machine in a sealed chamber and analyzed using a nano condensation nucleus counter, a CPC, and an FMPS. It was found that 1.3–4.4 nm particles are emitted during the friction. For the pairs with the LM and NAO, 1.3–4.4 nm particles predominate in number at temperatures above 160°C. The emission of the 1.3–4.4 nm particles precedes the emission of above 4.4 nm particles. For the cast iron pair, the number of 1.3–4.4 nm particles is smaller than the number of 4.4–10 nm particles. The findings suggest that brake materials produce a significant number of 1.3–4.4 nm airborne particles, and these particles should not be neglected in environmental and tribological studies.

Place, publisher, year, edition, pages
Taylor & Francis, 2017
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-199591 (URN)10.1080/02786826.2016.1255713 (DOI)000394660100008 ()2-s2.0-84997703721 (Scopus ID)
Projects
Rebrake Project
Note

QC 20170112

Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2018-01-13Bibliographically approved
Nosko, O., Borrajo-Pelaez, R., Hedström, P. & Olofsson, U. (2017). Porosity and shape of airborne wear microparticles generated by sliding contact between a low-metallic friction material and a cast iron. Journal of Aerosol Science, 113, 130-140.
Open this publication in new window or tab >>Porosity and shape of airborne wear microparticles generated by sliding contact between a low-metallic friction material and a cast iron
2017 (English)In: Journal of Aerosol Science, ISSN 0021-8502, E-ISSN 1879-1964, Vol. 113, 130-140 p.Article in journal (Refereed) Published
Abstract [en]

The wear of brakes in transport vehicles is one of the main anthropogenic sources of airborne particulate matter in urban environments. The present study deals with the characterisation of airborne wear microparticles from a low-metallic friction material / cast iron pair used in car brakes. Particles were generated by a pin-on-disc machine in a sealed chamber at sliding velocity of 1.3 m/s and contact pressure of 1.5 MPa. They were collected on filters in an electrical low pressure impactor, and an investigation was conducted to quantify their shape and porosity. Scanning electron microscopy revealed that most of the 0.1−0.9 µm particles are flakes and have a breadth-to-length aspect ratio of 0.7 ± 0.2. Particle porosity was determined by milling particles with a focused ion beam and subsequent analysis of the exposed particle cross-sections. Most of the 0.3–6.2 µm particles were revealed to have porosity of 9 ± 6%. Analysis of the relationship between effective particle density, particle material density, dynamic shape factor and porosity showed that the shape factor has a stronger influence on the effective density of airborne wear particles than the porosity factor. The obtained results are useful for accurate prediction of particle behaviour in the atmosphere and in the human respiratory system.

Place, publisher, year, edition, pages
Elsevier Ltd, 2017
Keyword
Aerosol measurement, Airborne wear particles, Dynamic shape factor, Particle porosity, Particle shape, Pin-on-disc, Aspect ratio, Cast iron, Characterization, Friction, Friction materials, Ion beams, Respiratory system, Scanning electron microscopy, Urban transportation, Airborne wears, Pin on disc, Shape factor, Porosity
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-218639 (URN)10.1016/j.jaerosci.2017.07.015 (DOI)2-s2.0-85028439645 (Scopus ID)
Note

QC 20171129

Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2018-01-13Bibliographically approved
Höjer, M., Bergseth, E., Olofsson, U., Nilsson, R. & Lyu, Y. (2016). A noise related track maintenance tool for severe wear detection of wheel-rail contact. Civil-Comp Proceedings, 110.
Open this publication in new window or tab >>A noise related track maintenance tool for severe wear detection of wheel-rail contact
Show others...
2016 (English)In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 110Article in journal (Refereed) Published
Abstract [en]

An on-board measurement system has been developed that in real time identifies the probability for occurrence and also the exact location of severe wear in the wheelrail contact. Noise generated by the wheel-rail contact is a troublesome side effect both when railway vehicles negotiate curves and run on straight tracks. The concept behind this project is to use this noise as an indicator of the transition from the mild wear regime to the severe/catastrophic wear regime that implies high maintenance cost. At first tribometers were used in a laboratory study to investigate the relationships between wear and the emitted noise. Wear transitions from mild to severe wear were always accompanied by an increase in sound pressure of about 10 dB. The transitions also changed the sound pressure amplitude distribution from a narrow banded to a broader banded distribution. Secondly a full scale test in a small radius curve in a depot was carried out using a metro train, type C20. In agreement with the laboratory tests, the same kind of transfer from mild to severe wear was identified on the full scale tests in the depot. In addition, the sound pressure changed significantly, both in amplitude and in distribution, when transferring from mild to severe wear. By comparing the noise from the inner wheel-rail contact to noise from the outer wheel-rail contact a wear detection parameter for the outer wheel-rail contact is suggested. The third part of this project involves validation of the maintenance tool by operating the instrumented train in normal metro traffic, while at the same time collecting wear particles and making replicate casts of the rail at critical locations in the metro. Further comparison with weather data and a maintenance log has also been performed. © Civil-Comp Press, 2016.

Keyword
Maintenance, Noise, Wear, Wheel-rail contact, Acoustic noise, Firing (of materials), Wear of materials, Wheels, Critical location, Full scale tests, Laboratory studies, Maintenance tools, On-board measurements, Track maintenance, Wheel-rail contacts, Vehicle wheels
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-186741 (URN)2-s2.0-84964334415 (Scopus ID)
Note

QC 20160527

Available from: 2016-05-27 Created: 2016-05-13 Last updated: 2017-11-30Bibliographically approved
Liu, H., Olofsson, U., Jonsson, L. T. & Jönsson, P. G. (2016). A pin-on-disc study of airborne wear particles from dry sliding wheel-rail contacts. Civil-Comp Proceedings, 110.
Open this publication in new window or tab >>A pin-on-disc study of airborne wear particles from dry sliding wheel-rail contacts
2016 (English)In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 110Article in journal (Refereed) Published
Abstract [en]

Pin-on-disc laboratory tests were carried out to identify the generation of airborne wear particles in wheel-rail contacts under different sliding velocities. The results show that the sliding velocity significantly influences both the number and size distribution of airborne wear particles. A comparison of the contact temperature was obtained during tests. For tests with high sliding velocities (1.2 and 3.4 m/s), the particle number concentration level was related to the elevated contact temperature in selected time intervals. Moreover, morphological and elemental analyses of collected particles and pin worn surfaces were studied by using a scanning electron microscope and field emission-scanning electron microscope. The data suggests that the oxide layers were detected within the pin's worn surfaces and an abundant presence of iron-oxide containing particles was observed. Therefore, it can be concluded that abundant fine and ultrafine airborne particles are more likely to be produced from an oxidative wear process in a wheel-rail contact under high sliding velocities.

Place, publisher, year, edition, pages
Civil-comp press, 2016
Keyword
Airborne wear particles, Contact temperature, Iron oxide containing particles, Oxidative wear, Particle number concentration, Scanning electron microscope, Wheel-rail contact, Electron emission, Plastics fillers, Scanning, Scanning electron microscopy, Vehicle wheels, Velocity, Wheels, Airborne wears, Wheel-rail contacts, Iron oxides
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-186745 (URN)2-s2.0-84964374728 (Scopus ID)
External cooperation:
Note

QC 20160530

Available from: 2016-05-30 Created: 2016-05-13 Last updated: 2017-11-30Bibliographically approved
Liu, H., Jonsson, L. T., Olofsson, U. & Jönsson, P. G. (2016). A Simulation Study of Particles Generated from Pellet Wear Contacts during a Laboratory Test. ISIJ INTERNATIONAL, 56(11), 1910-1919.
Open this publication in new window or tab >>A Simulation Study of Particles Generated from Pellet Wear Contacts during a Laboratory Test
2016 (English)In: ISIJ INTERNATIONAL, ISSN 0915-1559, Vol. 56, no 11, 1910-1919 p.Article in journal (Refereed) Published
Abstract [en]

In the blast furnace process, material losses occur due to mechanical wear between charged iron ore pellets and are exhausted in the form of dust in the off-gases. A redesigned tribometer combined with a ventilation chamber was developed to identify the dust emission from the mechanical wear contact of pellets. In order to obtain a better understanding of the measurement results, a coupled drift flux with a unified Eulerian deposition model was adopted to investigate particle dispersion and deposition during tests. Two influential factors, namely the air condition (5-20 L/min) and particle size (1-20 mu m) were examined. The predicted results were presented by introducing two parameters, namely the measurable fraction and the deposition fraction. For each air condition, the measurable fraction declines while the deposition fraction rises as particle size grows. The critical size of the particles that becomes airborne and captured at the outlet was identified to be around 20 mu m. In addition, a high airflow rate supplied at the inlet was observed to be favorable for improving the measurable fraction. Nevertheless, the results show that nearly 50% of emitted particles (1-20 mu m) that failed to be captured during tests. Thus it could be expected that these generated particles would be transported deeply in a blast furnace if they are not efficiently removed from the off-gas. As a consequence, they may influence the quality of the products. Furthermore, the validation of the simulation results against the experimental data was achieved by using the predicted measurable fraction.

Place, publisher, year, edition, pages
Iron and Steel Institute of Japan, 2016
Keyword
particle, pellet, off-gas, particle size, deposition, computational fluid dynamics, wear
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-200077 (URN)10.2355/isijinternational.ISIJINT-2016-328 (DOI)000388910500003 ()2-s2.0-84995403899 (Scopus ID)
Note

QC 20170125

Available from: 2017-01-25 Created: 2017-01-20 Last updated: 2017-06-29Bibliographically approved
Li, X., Sosa, M., Andersson, M. & Olofsson, U. (2016). A study of the efficiency of spur gears made of powder metallurgy materials - ground versus super-finished surfaces. Tribology International, 95(1), 211-220.
Open this publication in new window or tab >>A study of the efficiency of spur gears made of powder metallurgy materials - ground versus super-finished surfaces
2016 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 95, no 1, 211-220 p.Article in journal (Refereed) Published
Abstract [en]

Power loss is one of the main concerns in gear transmission systems. In this study a recirculating power back-to-back FZG test rig was used to investigate the efficiency of spur gears made of powder metallurgy (PM) material using two different surface manufacturing methods (ground and super-finished). The results were compared with previously presented results of standard gear material from the same test rig. The influence of the material (Wrought steel or PM) and surface roughness on the gear mesh efficiency and the total efficiency of the gearbox were analyzed in detail. The Young's modulus for PM materials is lower than for conventional gear steel. This may influence gear tooth bending and the efficiency of the gear transmission. Gear contact simulation results showed that the influence of gear tooth bending on PM gear transmission efficiency can be ignored in the FZG gear geometry. Higher surface energy combined with a smoother surface led to a lower transmission efficiency for the super-finished powder metallurgy gear combination compared to the standard gear material.

Place, publisher, year, edition, pages
Elsevier, 2016
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-179702 (URN)10.1016/j.triboint.2015.11.021 (DOI)000371103400024 ()2-s2.0-84949433501 (Scopus ID)
Note

QC 20160121

Available from: 2015-12-21 Created: 2015-12-21 Last updated: 2017-12-01Bibliographically approved
Cha, Y., Hedberg, Y., Mei, N. & Olofsson, U. (2016). Airborne Wear Particles Generated from Conductor Rail and Collector Shoe Contact: Influence of Sliding Velocity and Particle Size. Tribology letters, 64(3), Article ID 40.
Open this publication in new window or tab >>Airborne Wear Particles Generated from Conductor Rail and Collector Shoe Contact: Influence of Sliding Velocity and Particle Size
2016 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 64, no 3, 40Article in journal (Refereed) Published
Abstract [en]

The mechanical wear of train components is one of the main sources of airborne particles in subway air. A certain contribution is suspected to derive from third-rail systems due to the sliding of two metallic surfaces between conductor rail and collector shoe during operation. In this study, a pin-on-disc apparatus was used to simulate the friction between such two sliding partners (shoe-to-rail). Airborne particles generated from the sliding contact were measured by particle counters (a fast mobility particle sizer spectrometer and an optical particle sizer) and were collected by an electrical low-pressure impactor for physical and chemical analysis. Interface temperature for each test was measured by a thermocouple. The influence of sliding velocity and temperature on particulate number concentration, size distribution, and chemical composition was investigated. Atomic absorption spectroscopy, cyclic voltammetry, and energy-dispersive spectroscopy measurements were carried out to determine the chemical compositions. Results show that increasing sliding velocity results in a higher temperature at the frictional interface and a higher concentration of ultrafine particles. The ratio of manganese to iron surface oxides increased strongly with smaller particle size. A copper compound was observed in some particle samples, probably gerhardite (Cu2NO3(OH)(3)) formed due to high temperature.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2016
Keyword
Sliding wear, Third-rail tribology, Particle emissions, Airborne wear particle, Oxidative wear
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-199514 (URN)10.1007/s11249-016-0775-7 (DOI)000389604800008 ()2-s2.0-84993992738 (Scopus ID)
Note

QC 20170117

Available from: 2017-01-17 Created: 2017-01-09 Last updated: 2017-11-29Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2489-0688

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