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  • 1. Houghton, A.
    et al.
    Lewis, R.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Sundh, Jon
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Characterising and reducing seizure wear of inconel and incoloy superalloys in a sliding contact2011Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, nr 9-10, s. 1671-1680Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Superalloys, such as Inconels and Incoloys, are extensively used where high strength is a requirement. However, where these materials are required to slide against one another, particularly with poor or no lubrication, high friction levels and seizure are commonly seen to occur, which can cause component failure. In this work seizure characteristics of three superalloys (Inconel 718 and Incoloys 945 and 945X) were investigated, uncoated, coated with Armoloy (a hard, thin, dense chrome coating with a micro-nodular surface texture) and plasma nitrided in dry sliding conditions. A rig purpose built for initiating seizure was used. It involves sliding a ball against a disc at constant speed while the load is increased. Tests are designed to last less than one rotation so that the wear scar can be analysed, along with friction data, to establish at which load seizure occurred. Balls made from Inconel 718 were used along with sliding velocities ranging between 0.1 and 0.25 m/s with a load range of 0-1400 N. Tests were repeated twice. Repeatable behaviour was achieved in the tests and from the results obtained, zones/points corresponding to "seizing", "seizure" and "seized" were identified based on previous definition from the literature. Friction coefficients behaviour was also characterised. It was found that Inconel 718 and Incoloy 945 performed better than Incoloy 945X. Applying an Armoloy coating increased the seizure load and led to lower friction rates. The application of plasma nitriding led to a more consistent (although high) friction coefficient, but less surface damage occurring.

  • 2. Jansson, Anders
    et al.
    Olander, Lars
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Installationsteknik (bytt namn till Installations- och energisystem 2012-03-01).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Sundh, Jon
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Söderberg, Anders
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Wahlström, Jens
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Ultrafine Particle Formation from Wear2010Inngår i: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 9, nr 1, s. 83-88Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Much attention is given to the consequences of airborne particles on human health and well-being. Wear is one source of airborne particles and contributions in the urban environments from wheel-to-rail contacts and disc brakes cannot be neglected. Traditionally, mechanical wear has been associated with the generation of particles of diameters of some microns. However, the research described has found ultrafine particle generation from wear processes. Particle generation from wear was measured under controlled laboratory conditions. The wear was created through sliding contact in a tribometer (type "pin-on-disc") with different materials and with different sliding velocities and pressures, to represent rail traffic and automobile disc braking. Particle concentrations and size distributions in the air were determined for particle diameters from 10 nm up to more than 10 mu m. For most materials and conditions three particle size modes were found: one at 50-100 nm, one at a few hundred nm and one at a few mu m particle diameter.

  • 3.
    Jon, Sundh
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    On wear transitions in the wheel-rail contact2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Wear transitions in the wheel–rail contact are of increasing interest since the general trend in railway traffic is toward increased velocities and axle loads. Curving increases the risk of flanging, causing the contact to change from an almost pure rolling wheel tread–rail head contact to more of a sliding wheel flange–rail gauge contact on the high rail in curves.

    Under wheel flange–rail gauge contact conditions, wear transitions to severe or catastrophic wear will occur if the contact is improperly lubricated. Such a transition is the most undesirable transition in the wheel–rail contact, as it represents a very expensive operating condition for railway companies. The contact conditions responsible for this transition are very severe as regards sliding velocity and contact pressure, and thus place high demands on both the lubricant and the wheel and rail materials.

    The focus of this thesis is on the transitions between different wear regimes in a wheel–rail contact. Wear is discussed both in traditional tribological terms and in terms of the categories used in the railway business, namely mild, severe and catastrophic wear. Most of the work was experimental and was performed at the Royal Institute of Technology (KTH), Department of Machine Design.

    The effects of contact pressure, sliding velocity, and type of lubricant have been investigated, producing results that resemble those of other studies presented in the literature. The absence of research relating to the wheel flange–rail gauge contact is addressed, and it is concluded that a lubricant film must be present on rails in curves to prevent severe or catastrophic wear. The formulation of this lubricant can further increase its wear- and seizure-preventing properties. To obtain a deeper understanding of wear transitions, methods such as airborne particle measurement and electron microscopy have been used.

    Paper A presents the test methodology used to detect seizure and discusses the wear-reducing influence of free carbon in highly loaded contacts.

    Paper B presents the testing of seizure-initiating conditions for a range of environmentally adapted lubricants applied to wheel and rail materials; a transient pin-on-disc test methodology was used for the testing.

    Paper C presents the use of pin-on-disc methodology to study the wear-reducing effects of a wide range of lubricants. The best performing lubricant was a mineral oil containing EP and AW additives.

    Paper D relates wear rates and transitions to airborne particles generated by an experimentally simulated wheel–rail contact. The airborne particles generated varied in size distribution and amount with wear rate and mechanism.

    Paper E relates additional analysis techniques, such as FIB sectioning, ESCA analysis, airborne particle measurements, and SEM imaging of airborne wear particles, to the contact temperature.

     

    Fulltekst (pdf)
    FULLTEXT01
  • 4.
    Olofsson, Ulf
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Sundh, Jon
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Bik, Ulf
    Nilsson, Ricard
    The influence of snow on the tread braking performance of a train: A pin-on-disc simulation performed in a climate chamber2016Inngår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 230, nr 6, s. 1521-1530Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In trains with tread brakes, the coefficient of friction between the brake block and the railway wheel determines the stopping distance. The blocks have traditionally been manufactured from cast iron. Although these blocks have good braking capacity, their use is often restricted due to the squealing noise they emit. Tests of alternative composite block materials have been successful under summer conditions; however, in regions with snowy winters the use of such materials has been limited due to problems with braking capacity under snowy conditions. This research aims to develop a laboratory-scale test methodology for evaluating the braking capacity of tread brake materials under winter and snowy conditions. A pin-on-disc machine placed in a climate chamber was used for testing, and a block of standard cast iron was compared with blocks of standard composite materials. The results indicated that the blocks of standard composite materials generate a much smoother surface on the counter wheel and a significantly lower friction coefficient under snowy conditions. A second test series evaluated blocks of alternative composite materials, and a candidate material with low noise and a sufficiently high sliding friction coefficient was selected for further study. A third test series examining geometrical changes in the contact surface in terms of milled parallel tracks was performed; it revealed that the braking capacity under winter conditions can be increased by milling actions if the parallel tracks are properly oriented - in this case, at an angle of 45 degrees to the sliding direction.

  • 5.
    Sjöberg, Sören
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Sundh, Jon
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Scuffing resistance of gear surfaces: influence of manganese phosphate and lubricants2009Inngår i: Proceedings of 2nd European Conference on Tribology: ECOTRIB 2009, 2009Konferansepaper (Fagfellevurdert)
  • 6.
    Sjöberg, Sören
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Sundh, Jon
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Scuffing resistance of gear surfaces: influence of manganese phosphate and lubricantsManuskript (preprint) (Annet vitenskapelig)
  • 7.
    Sundh, Jon
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    An experimental study on wear transitons in the wheel-rail contact2007Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 8.
    Sundh, Jon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    af Sätra, Ulf Skytte
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Influence of surface topography and surface modifications on seizure initiation in lean lubricated sliding contacts2007Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 262, s. 986-995Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Seizure initiation in lean-lubricated contacts was experimentally studied using a transient test method of ball-on-disc type at two different sliding velocities, 2 and 3.8 m/s. Four different nodular cast iron surfaces were tested against a bearing ball of 100Cr6 steel: a fine-milled and roller-burnished surface, a ground and lapped surface, a ground and lapped laser-melted surface, and finally a ground surface. The results show that the ground surface, even though it is smoother than the fine-milled and roller-burn i shed surface, shows indications of seizure at a lower load. No graphite nodules from the nodular cast iron were visible in the surfaces on inspection with an optical light microscope. In contrast, the ground and lapped surface suffered no initial or total seizure in these tests. In this case, many graphite nodules were visible in the surface, and these nodules became detached in the contact zone, where they probably acted as a solid lubricant. Many graphite nodules were also visible in the ground and laser-melted surface, though in this case the graphite nodules did not become detached. This surface topography initiated seizure under a low normal load, and increased sliding velocity lowered the total seizure load significantly.

  • 9.
    Sundh, Jon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Relating contact temperature and wear transitions in a wheel-rail contact2011Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, nr 1-2, s. 78-85Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Earlier in an ongoing research project, we identified wear transitions, mechanisms, and regimes by experimentally testing the sliding part of a wheel-rail contact. Going further, the present study investigates the effects of elevated contact temperature and severe contact conditions corresponding to those of a wheel flange-gauge corner contact.

    Prior studies discussed wear in terms of contact pressure, amount and type of lubricant, sliding velocity, generated airborne particles, wear depth, coefficient of friction, and topographical measurements. This study shifts the focus to contact temperature, elemental and morphological analysis of the airborne particles, and surface-layer microstructure of test specimens by using several analytical techniques (i.e., SEM, FIB, ESCA, and energy mapping).

    As contact severity increased, the bulk temperature of the contacting bodies increased rapidly; this can be related to elevated contact temperature by judging the size and shape of the ultrafine particles generated. After test runs, the contacting bodies were analysed, revealing microstructural surface layer changes and differences in the amount of oxide formed in the immediate surface.

    When the sliding part of the wheel-rail contact under severe contact conditions is experimentally simulated using pin-on-disc methodology, the discussion shifts from analyzing steady-state measurements, such as average wear rate, to more transient behaviours during running-in. Wear transitions occurring during running-in are decisive for the outcome of the rest of the test run, according to the present results.

  • 10.
    Sundh, Jon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Seizure mechanisms of wheel–rail contacts under lubricated conditions using a transient ball-on-disc test method2008Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, s. 867-874Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study focuses on the transition from mild to severe wear in the wheel and rail contact. Such a transition has been observed at increased loading (normal load, sliding velocity, or bulk temperature) which can be compared to a change from a wheel thread-rail head contact to a wheel flange-rail gauge contact. This transition was experimentally studied using a transient test method of ball-on-disc type at different sliding velocities, contact pressures, and lubricants. It can be seen in the results that different seizure mechanisms are active for different sliding velocities. Also the amount of applied lubricant clearly affects the transition to seizure.

  • 11.
    Sundh, Jon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olander, Lars
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Wear rate testing in relation to airborne particles generated in a wheel-rail contact2009Inngår i: Lubrication science, ISSN 0954-0075, Vol. 21, nr 4, s. 135-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study examines the relationship between generated airborne particles and wear rate in the wheel-rail contact. The wheel-rail contact is experimentally simulated by using pin-on-disc testing to determine the difference in wear rate between selected contact conditions.

    Wear is discussed both in tribological terms and by using the wear categories prevalent in the railway industry, namely, mild, severe and catastrophic wear. The discussion is based on wear depth, the coefficient of friction, topographical measurements and measurements of airborne particles generated in the contact.

    The tests were performed under selected loading conditions representative of different contact conditions in a real wheel-rail contact. The results indicate that wear rates vary with the contact conditions arising from different types of triggered wear transitions. This is emphasised by the number and size of the airborne particles generated.

  • 12.
    Sundh, Jon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Olander, Lars
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Installationsteknik (bytt namn till Installations- och energisystem 2012-03-01).
    Jansson, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Installationsteknik (bytt namn till Installations- och energisystem 2012-03-01).
    Wear rate testing in relation with airborne particles generated in a wheel-rail contact2008Konferansepaper (Annet vitenskapelig)
  • 13.
    Sundh, Jon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Sundvall, Krister
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Seizure and wear rate testing of wheel–rail contacts under lubricated conditions using pin-on-disc methodology2008Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, s. 1425-1430Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An increased wear rate and a shift of wear mechanism in the wheel-rail contact has been observed in tight curves, mainly due to the change from an almost pure rolling contact to more of a sliding contact. The wheel flange-rail gauge contact is commonly known to experience the toughest conditions of the overall wheel-rail contact in terms of contact pressure and sliding velocity. The wheel flange-rail gauge contact is preferably lubricated to reduce the wear rate and to minimise the risk of transition to severe wear or seizure. The amount and type of lubrication are therefore important parameters if one is to control the wear rate. In this study, a flange contact is experimentally simulated using pin-on-disc testing, to determine the difference in wear rate among a selection of lubricants under different contact conditions. The selection of lubricants consisted of environmentally adapted oils, mineral oils, and greases containing different amounts of EP and AW additives.The results of the pin-on-disc testing indicate that both the amount and type of lubrication applied is decisive for the wear rate and active wear mechanism. Tests have also been performed to simulate either on-board or wayside lubrication, by applying the lubricant at different intervals. A general observation is that under starved lubrication conditions a transition to severe wear is initiated and the wear rate increases rapidly, i.e., all tests indicate that the contact between wheel and rail must be lubricated to avoid high wear rates.

  • 14.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Sundh, Jon
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    A tribological view of wheel-rail wear maps2013Inngår i: The international Journal of railway technology, ISSN 2049-5358, E-ISSN 2053-602X, Vol. 2, nr 3, s. 79-91Artikkel i tidsskrift (Fagfellevurdert)
1 - 14 of 14
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  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
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