| 1. |
- Bergseth, Ellen, 1979-
(författare)
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On tribological design in gear tooth contacts
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The correct tribological design will have a considerable effect on a gear’s service life and efficiency. The purpose of this thesis is to clarify the impact of variation in the gear tooth flank tribological system on the gear contact load capacity – to increase the understanding of how surface topography and lubricant interact.In this thesis the variation in surface topography inherent in the manufacturing method has been shown, by experimental work and computer simulations, to be an important factor for the contact condition in the early life of gears. Surface analysis revealed that the formation and composition of surface boundary layers depends strongly on the chemical composition of the lubricant, but also on pre-existing surface boundary layers. Additionally, surface boundary layers play a major role in frictional behaviour, wear and in allowing the lubricant to react properly with the surfaces.Paper A presents the current ISO 6336 calculation of surface durability. A robust design approach was used to investigate the extent to which the current standard for calculation of surface durability allows for manufacturing variations and the choice of lubricant.Paper B investigates the extent to which a logarithmical profile modification can increase gear contact pressure robustness compared to traditional lead profiles for gears.Paper C compares different gear manufacturing methods and their as-manufactured (fresh unworn) surface topographies, using measured surface topographies as input to a contact simulation program.Paper D examines surface boundary layer formation and the corresponding wear in relation to different anti-wear additives in an environmentally adapted base oil.Papers E and F make use of specimens with surface topographies imitating two gear manufacturing methods (grinding and superfinishing) to be used in a twin-disc and barrel-on-disc machine respectively. The contacts are analysed by friction measurements and simulations combined with methods for surface analysis.
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| 2. |
- Abbasi, Saeed, 1973-, et al.
(författare)
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Temperature and Thermoelastic Instability at Tread Braking Using Cast Iron Friction Material
- 2013
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 314:1–2, s. 171-180
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Tidskriftsartikel (refereegranskat)abstract
- Braking events in railway traffic often induce high frictional heating and thermoelastic instability (TEI) at the interfacing surfaces. In the present paper, two approaches are adopted to analyse the thermomechanical interaction in a pin-on-disc experimental study of railway braking materials. In a first part, the thermal problem is studied to find the heat partitioning between pin and disc motivated by the fact that wear mechanisms can be explained with a better understanding of the prevailing thermal conditions. The numerical model is calibrated using the experimental results. In a second part, the frictionally induced thermoelastic instabilities at the pin-disc contact are studied using a numerical method and comparing them with the phenomena observed in the experiments. The effects of temperature on material properties and on material wear are considered. It is found from the thermal analysis that the pin temperature and the heat flux to the pin increase with increasing disc temperatures up to a transition stage. This agrees with the behaviour found in the experiments. Furthermore, the thermoelastic analysis displays calculated pressure and the temperature distributions at the contact interface that are in agreement with the hot spot behaviour observed in the experiments.
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| 3. |
- Vernersson, Tore V, 1968, et al.
(författare)
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Wear of Railway brake block materials at elevated temperatures : pin-on-disc experiments
- 2012
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Ingår i: Proceedings of Eurobrake 2012. - FISITA.
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Konferensbidrag (refereegranskat)abstract
- An experimental study on a pin-on-disc rig is presented where the wear of some brake block materials at controlled elevated disc temperatures are reported. It is found for the three studied organic composite materials that the (specific) wear rate increases radically at a temperature of about 500 oC. For temperatures below 500 oC, the wear rate is found to increase with temperature. The cast iron material shows an increase of the wear rate up to 500 oC, after which a transition in the wear mechanism occurs and the wear rate is decreasing with increasing temperature. The studied sinter material shows a weak dependence of the wear rate with temperature.
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| 4. |
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| 5. |
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| 6. |
- Bergseth, Ellen, 1979-, et al.
(författare)
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Investigation of pitting resistance in ultra clean IQ-Steel vs commonly used conventional steel; 158Q vs 16MnCr5 : Back-to-back pitting tests
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- KTH Machine Design has conducted pitting tests on gears made out of two different types of steel in a standard back-to-back pitting test rig (FZG). The tested gears were produced from Ovako’s IQ-Steel in grade 158Q and compared to the behaviour of a reference steel, commonly used conventional steel in grade 16MnCr5 (reference steel, RS). The test method is a mechanical test procedure generally used to determine the pitting load capacity of gear transmission lubricants, but in this study the purpose was to compare the pitting load capacity of the two steel types. The report is based on the test procedure described in FVA – Information sheet Research Project No. 371 (Practice Relevant Pitting Test) with minor changes. Time to failure and photographs of the fatigue damages are presented in this report. One gear tooth from each steel type was analysed using SEM. The results, which are based on six tests in total (three gear pairs IQ-Steel and three RS-steel), indicate that the IQ-Steel has better surface durability than the reference steel. To better understand the mechanisms involved, further tests are suggested.
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| 7. |
- Larsson, Tara, 1993-, et al.
(författare)
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Undiluted Measurement of sub 10 nm Non-Volatile and Volatile Particle Emissions from a DISI Engine Fueled with Gasoline and Ethanol
- 2021
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Ingår i: Undiluted Measurement of sub 10 nm Non-Volatile and Volatile Particle Emissions from a DISI Engine Fueled with Gasoline and Ethanol. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- In this paper, a High-Temperature Electrical Low-Pressure Impactor (HT-ELPI+) was used to measure particles from a light-duty direct injected spark ignited (DISI) engine fueled with gasoline and ethanol. The HT-ELPI+ measured volatile and non-volatile particle emissions down to 6 nm without the need for dilution. Particle emissions were measured at four operating points while sweeping the end of injection, and at idle operation. The total particle number (PN) and particle size distribution (number and mass) for both non-volatile and volatile emissions were measured with the HT-ELPI+ and compared to the measured PN using two 71.4 times diluted Condensation Particle Counters (CPCs) with two different cut-off sizes, with 23 nm and 7 nm cut-off, respectively. The results show an increase in particle emissions in terms of particle mass and total particle number for ethanol compared to gasoline. The difference in soot mass emissions is small between the fuels. However, PN shows a significant increase for ethanol, especially at low engine speed due to a deterioration in the evaporation, mixture formation and air entrainment of ethanol. A majority of the emitted particles exhibit particle sizes below 23 nm, wherein the highest numbers occurred below 10 nm. At steady-state operation, no clear difference was observed between the diluted and undiluted measurements. On the contrary, a significant difference is detected between the undiluted and diluted measurements of ethanol at idle. These observations could indicate a greater significance of dilution at lower exhaust gas temperatures and mass flow rates or when a large number of nucleation mode particles are emitted from the engine.
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| 8. |
- Abbasi, Saeed, 1973-, et al.
(författare)
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Particle emission from rail vehicles : A literature review
- 2012
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F. - Stirlingshire, UK : Sage Publications. ; 98
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Konferensbidrag (refereegranskat)abstract
- Emission of airborne particles is a side effect from rail transport. This work reviews recent research on particle emissions from rail vehicles. Both exhaust and non-exhaust particle emissions are characterized by size, morphology, composition, and size distribution. Current legislation, knowledge of adverse health effects, and available and proposed solutions for emission reductions are also treated. There has been much focus on exhaust emissions, but only a few limited studies have investigated non-exhaust particle emissions, which contain a significant amount of metallic materials. A new method for measuring the airborne wear particle emission rate (AWPER) is proposed as a first step to guide new legislations and to focus further research on non-exhaust airborne emission, i.e., research on the generation mechanisms for particle emissions and their adverse health effects.
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| 9. |
- Duvefelt, Kenneth, et al.
(författare)
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Model for contact between finger and sinusoidal plane to evaluate adhesion and deformation component of friction
- 2016
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Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 96, s. 389-394
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Tidskriftsartikel (refereegranskat)abstract
- One of the main parameters affecting finger friction, friction-induced vibrations in the finger, and consequently tactility is surface topography. Recently Skedung et al. performed finger friction measurements on fine controlled surfaces. These surfaces were sinusoidal with wavelengths from 0.27 to 8.8 mu m and amplitudes from 0.007 to 6 mu m. Building on those tests an analytical model for the contact was developed to explain the differences in friction coefficient. The contact was modelled as trapezoids in a circular pattern pressed against a sinusoidal plane. Results showed that the calculated contact area and therefore friction coefficient corresponded well with the measurements. This model can be used to see how the different surface parameters influence friction.
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| 10. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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Recycling of worn out brake pads impact on tribology and environment
- 2020
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Disc brake systems are widely used on commercial vehicles for braking. The brake pads are usually replaced by new ones before being totally worn out. Current methods to deal with the replaced brake pads include landfill and combustion, resulting in a huge waste of resources and increase of CO2 footprint. From a sustainable point of view, this study aims to evaluate the feasibility of recycling replaced brake pads by addressing a protocol recycling procedure. The results show that the recycled brake pads yield similar friction, wear and airborne particle emission to virgin brake pads. A streamlined life cycle assessment is conducted to compare the environmental impacts between producing virgin brake pads and recycling replaced brake pads. Energy consumption and CO2 footprint of the recycled brake pads are 36% and 34% less than virgin brake pads, indicating that recycling could be a promising method of handling replaced brake pads.
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