| 1. |
- Bergseth, Ellen, 1979-, et al.
(författare)
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A Wear Detection Parameter for the Wheel–Rail Contact Based on Emitted Noise
- 2019
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Ingår i: Tribology Transactions. - : Informa UK Limited. - 1040-2004 .- 1547-397X. ; 62:3, s. 496-503
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Tidskriftsartikel (refereegranskat)abstract
- This article describes how a wheel–rail wear detection parameter based on noise was developed by running a rapid transit train instrumented with microphones in a depot with a small curve radius. This full-scale test made use of previous knowledge gained from lab-scale tests. The lab- and full-scale tests showed that noise could be used as an indicator of wear transition, when normal wear turns into severe or catastrophic wear. This transition was accompanied by a significant increase in sound pressure and a broader sound pressure amplitude spectrum; that is, a narrow initial amplitude distribution in the normal wear regime and a broader distribution in the severe wear regime. The measured noise from the inner/low and outer/high rails was analyzed in conjunction with the wear from the outer wheel and comparisons were made between cleaned (exposed to severe wear) and lubricated (no wear) rail. Based on those analyses, a wear detection parameter criterion was developed for this specific train. This wear parameter has been implemented in a real-time condition monitoring system so that warnings of the risk for severe wear could be sent to the maintenance department. Validation of the wear parameter and challenges linked to open system conditions are discussed in this article.
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| 2. |
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| 3. |
- Dizdar, Senad, et al.
(författare)
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Grey Cast Iron Brake Discs Laser Cladded with Nickel-Tungsten Carbide-Friction, Wear and Airborne Wear Particle Emission
- 2020
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Ingår i: Atmosphere. - Basel : MDPI. - 2073-4433. ; 11:6
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Tidskriftsartikel (refereegranskat)abstract
- Airborne wear particle emission has been investigated in a pin-on-disc tribometer equipped with particle analysis equipment. The pins are cut out from commercial powder metallurgy automotive brake pads as with and without copper content. The discs are cut out from a commercial grey cast iron automotive brake disc as cut out and as in addition to a laser cladded with a powder mix of Ni-self fluxing alloy + 60% spheroidized fused tungsten carbide and then fine-ground. Dry sliding wear testing runs under a contact pressure of 0.6 MPa, sliding velocity of 2 m/s and a total sliding distance of 14,400 m. The test results show both wear and particle emission improvement by using laser cladded discs. The laser cladded discs in comparison to the reference grey cast iron discs do not alter pin wear substantially but achieves halved mass loss and quartered specific wear. Comparing in the same way, the friction coefficient increases from 0.5 to 0.6, and the particle number concentration decreases from over 100 to some 70 (1/cm(3)) and the partition of particles below 7 mu m is approximately halved.
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| 4. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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A Friction, Wear and Emission Tribometer Study of Non-Asbestos Organic Pins Sliding Against AlSiC MMC Discs
- 2018
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Ingår i: Tribology in Industry. - : Faculty of Engineering, University of Kragujevac. - 0354-8996 .- 2217-7965. ; 40:2, s. 274-282
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Tidskriftsartikel (refereegranskat)abstract
- The friction, wear and particle emission from an AlSiC MMC brake disc/non-asbestos organic brake pad system is studied using a pin-on-disc tribometer. The results show that this unconventional AlSiC MMC brake disc system presents friction performance as good as a conventional cast iron brake disc system. During braking, brake pad materials are transferred to the brake disc surface to form a protective third body tribo-layer, resulting in a negative specific wear rate of the brake disc. A higher contact load is likely to make it easier to generate the tribo-layer. The tribo-layer also seems to depend on the disc surface grinding features and the contact temperature during braking. By reusing an AlSiC MMC disc where the tribo-layer is already formed, the airborne emission in terms of mass is about 50% lower and in terms of number about the same as the conventional brake contact pair under a similar braking condition. Further full-scale studies are suggested to determine the validity of the findings.
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| 5. |
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| 6. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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A pin-on-disc study on the tribology of cast iron, sinter and composite railway brake blocks at low temperatures
- 2019
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; , s. 48-52
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Lyu, Yezhe, 1987-
(författare)
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Abrasive Wear of Compacted Graphite Cast Iron with Added Tin
- 2019
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Ingår i: Metallography, Microstructure, and Analysis. - : Springer. - 2192-9262 .- 2192-9270. ; 8:1, s. 67-71
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Tidskriftsartikel (refereegranskat)abstract
- The abrasive wear behavior of traditional compacted graphite cast iron (CGI) and compacted graphite cast iron with 0.1% tin addition (CGI-Sn) is studied using a pin-on-disk tribometer. The microstructures of these two CGIs were observed by optical microscopy and scanning electron microscopy. The results show that Sn reduces the average size of vermicular graphite and promotes the generation of pearlite. Sn narrows the average lamellar spacing of pearlite. In the wear tests, CGI-Sn yields a decreased wear loss by 16.5% compared with CGI. Both CGI and CGI-Sn show typical abrasive worn morphology, while CGI presents a more severe wear condition in which large fragmentations can be seen. Under the current test condition, Sn is likely to improve the abrasive wear resistance of compacted graphite iron. Further studies of the specific working conditions are needed, such as testing against frictional material in braking systems, to check the validity of the findings.
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| 8. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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Characterization of ultrafine particles from hardfacing coated brake rotors
- 2023
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Ingår i: Friction. - : Tsinghua University. - 2223-7690 .- 2223-7704. ; 11:1, s. 125-140
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Tidskriftsartikel (refereegranskat)abstract
- Automotive brake rotors are commonly made from gray cast iron (GCI). During usage, brake rotors are gradually worn off and periodically replaced. Currently, replaced brake rotors are mostly remelted to produce brand-new cast iron products, resulting in a relatively high energy consumption and carbon footprint into the environment. In addition, automotive brakes emit airborne particles. Some of the emitted particles are categorized as ultrafine, which are sized below 100 nm, leading to a series of health and environmental impacts. In this study, two surface treatment techniques are applied, i.e., high-velocity oxygen fuel (HVOF) and laser cladding (LC), to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting procedure. The two coating materials are evaluated in terms of their coefficient of friction (CoF), wear, and ultrafine particle emissions, by comparing them with a typical GCI brake rotor. The results show that the CoF of the HVOF disc is higher than those of the GCI and LC discs. Meanwhile, HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad material. The LC disc yields a similar wear rate as the GCI disc. The ultrafine particles from the GCI and LC discs appeared primarily in round, chunky, and flake shapes. The HVOF disc emits unique needle-shaped particles. In the ultrafine particle range, the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady state. Meanwhile, the LC disc emitted particles that are primarily ∼200 nm in the entire test run.
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| 9. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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Effect of humidity on the tribological behaviour and airborne particle emissions of railway brake block materials
- 2018
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Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 118, s. 360-367
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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Effect of Tin on Microstructure and Mechanical Properties of Compacted Graphite Iron
- 2015
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Ingår i: International Journal of Cast Metals Research. - : Maney Publishing. - 1364-0461 .- 1743-1336. ; 28:5, s. 263-268
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Tidskriftsartikel (refereegranskat)abstract
- This experiment investigated the effect of tin in an amount up to 0.121 wt.% on the microstructure and mechanical properties of compacted graphite iron (CGI). Graphite and matrix evolution was emphasized with the help of scanning electron microscopy. The results indicate that Sn in experimental range reduces graphite size. Pearlite quantity would increase with the increasing Sn and reaches over 95% when Sn is greater than 0.057 wt.%. Sn helps to narrow the lamellar spacing of pearlite from sorbitic pearlite (320 nm) to troostitic pearlite (83 nm) when Sn increases from 0.003 wt.% to 0.057 wt.%. Appropriate Sn addition promotes the tensile strength and impact toughness and the samples containing 0.057 wt.% Sn perform the highest values of 410.7 MPa and 9.11 J/cm2, respectively. Elongation declines with increasing Sn content because of the emergence of more pearlite. Samples containing excessive Sn experience sharply deterioration in mechanical properties due brittle cementite.
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