| 1. |
- Houghton, A., et al.
(författare)
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Characterising and reducing seizure wear of inconel and incoloy superalloys in a sliding contact
- 2011
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 271:9-10, s. 1671-1680
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Jansson, Anders, et al.
(författare)
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Ultrafine Particle Formation from Wear
- 2010
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Ingår i: The International Journal of Ventilation. - : Informa UK Limited. - 1473-3315 .- 2044-4044. ; 9:1, s. 83-88
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Jansson, Anders, 1947-, et al.
(författare)
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Ultrafine particle formation from wear
- 2009
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Ingår i: Proceedings of Ventilation 2009, the 9th International Conference on Industrial Ventilation.
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Konferensbidrag (refereegranskat)abstract
- 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 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 μm. However, we have also 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 μm. 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 μm particle diameter.
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| 4. |
- Johansson, Lena, 1972, et al.
(författare)
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Decreased physical health-related quality of life—a persisting state for older women with clinical vertebral fracture
- 2019
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Ingår i: Osteoporosis International. - London : Springer London. - 0937-941X .- 1433-2965. ; 30:10, s. 1961-1971
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Tidskriftsartikel (refereegranskat)abstract
- In a population-based study of older Swedish women, we investigated if clinical vertebral fracture was associated with lower health-related quality of life (HRQoL) and determined whether the association remained over time. Clinical vertebral fracture was associated with lower HRQoL and the effect persisted for up to 18.9 years.IntroductionVertebral fractures are often associated with back pain and reduced physical function, which might result in isolation and depression. As a result, women with vertebral fractures often have lower health-related quality of life (HRQoL), but during what time frame the decrease lingers is unclear. Therefore, the aim of this study was to investigate if clinical vertebral fracture and hip fracture were associated with lower HRQoL and to determine whether the associations remained over time.MethodsVertebral fracture assessments (VFA) were performed using dual-energy X-ray absorptiometry. Data regarding prior fractures, medications, medical history, and physical activity was collected using a questionnaire. Self-rated physical HRQoL was assessed using the 12-Item Short-Form Health Survey (SF-12). Women with clinical vertebral fractures were divided into tertiles according to time since fracture onset and their HRQoL was compared with non-fractured women.ResultsIn a population-based cross-sectional study of 3028 women aged 77.8 ± 1.63 (mean ± SD), a total of 130 (4.3%) women reported at least one clinical vertebral fracture. Women with a clinical vertebral fracture, divided into tertiles (T1–T3) depending on time since the fracture occurred, had lower HRQoL (T1: 36.3 ± 10.8; T2: 41.0 ± 9.94; and T3:41.6 ± 11.4) than women without fracture (46.2 ± 10.6; p < 0.001). Using linear regression analysis, clinical vertebral fracture was associated with reduced physical HRQoL for up to 18.9 years, independently of covariates (age, height, weight, smoking, prior stroke, mental HRQoL, grip strength, and lumbar spine BMD).ConclusionsClinical vertebral fracture was associated with lower self-rated physical HRQoL, for up to 18.9 years after time of fracture. © 2019, The Author(s).
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| 5. |
- Jon, Sundh, 1978-
(författare)
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On wear transitions in the wheel-rail contact
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 6. |
- Nilsson, Rickard, et al.
(författare)
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Utredning och provning av kostnadseffektiva metoder för bullerminimering av spårfordon
- 2013
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Ingår i: Transportforum 2013. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 122-135
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Konferensbidrag (refereegranskat)abstract
- Den här artikeln avser att för ett befintligt spårtrafiksystem översiktligt beskriva olika bullerreducerande åtgärders effekt, deras ekonomiska aspekter samt indirekt inverkan på systemet och dess omgivning. SL (AB Storstockholms Lokaltrafik) arbetar aktivt för att minska tågtrafikens störning till omgivningen, med den långsiktiga strävan att hela SLs spårsystem ska innehålla riktvärden för ny- och ombyggd järnväg enligt infrastrukturpropositionen. Ett viktigt medel för att nå denna ambition är succesivt byte av fordonsparken till nya och tystare fordon, detta kommer dock inte ge tillräcklig bullerreduktion, ytterligare åtgärder kommer att krävas. Beroende på problembilden kan det innebära att en enstaka åtgärd eller flera åtgärder i kombination behöver tas till. För att kartlägga, utvärdera och skapa kunskap om olika åtgärdsalternativ har SL därför arbetat långsiktigt och systematiskt med att utvärdera ett antal olika metoder. En viktig aspekt i sammanhanget är att då SLs spår till stor del går mycket nära bostäder är det önskvärt att hitta effektiva bullerskyddsåtgärder med så liten påverkan som möjligt avseende landskapsbild och barriäreffekt. Med hänsyn till ägardirektivet om ekonomi i balans är det även viktigt att se till total nytta relativt total kostnad vid val av åtgärd.
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| 7. |
- Olofsson, Ulf, et al.
(författare)
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The influence of snow on the tread braking performance of a train : A pin-on-disc simulation performed in a climate chamber
- 2016
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : Sage Publications. - 0954-4097 .- 2041-3017. ; 230:6, s. 1521-1530
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Sundh, Jon, 1978-, et al.
(författare)
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Influence of surface topography and surface modifications on seizure initiation in lean lubricated sliding contacts
- 2007
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 262, s. 986-995
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 12. |
- Sundh, Jon, et al.
(författare)
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Relating contact temperature and wear transitions in a wheel-rail contact
- 2011
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 271:1-2, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 13. |
- Sundh, Jon, et al.
(författare)
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Seizure and wear rate testing of wheel–rail contacts under lubricated conditions using pin-on-disc methodology
- 2008
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; , s. 1425-1430
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 14. |
- Sundh, Jon, et al.
(författare)
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Seizure mechanisms of wheel–rail contacts under lubricated conditions using a transient ball-on-disc test method
- 2008
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 41, s. 867-874
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 15. |
- Sundh, Jon, et al.
(författare)
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Wear rate testing in relation to airborne particles generated in a wheel-rail contact
- 2009
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 21:4, s. 135-150
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 16. |
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| 17. |
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