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  • 1.
    Abbasi, Saeed
    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.), Maskinelement.
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Sellgren, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Pin-on-disc study of the effects of railway friction modifiers on airborne wear particles from wheel-rail contact2013Ingår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 60, s. 136-139Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowledge of wheel–rail interaction is crucial to wheel and rail maintenance. In this interaction, some of theworn-off material is transformed into airborne particles. Although such wear is well understood, few studiestreat the particles generated. We investigated friction modifiers' effects on airborne particles characteristicsgenerated in wheel-rail contacts in laboratory conditions. Pin-on-disc machine testing with a round-head pinloaded by a dead weight load 40 N simulated maximum contact pressure over 550 MPa. Airborne particlecharacteristics were investigated in dry contacts and in ones lubricated with biodegradable rail grease andwater- and oil-based friction modifiers. The number of particles declined with the grease; the number ofultrafine particles increased with the water-based friction modifier, mainly due to water vaporization.

    Ladda ner fulltext (pdf)
    peerreviewad version
  • 2.
    Bergseth, Ellen
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Söderberg, Anders
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Study of surface roughness and surface orientation on friction in rolling/sliding contacts: barrel-on-disc versus twin-disc2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Gears are one of the most important means of mechanical power transmission. Even though the efficiency is high for a gear pair today, further decrease in friction can contribute to lower the fuel consumption. A barrel-on-disc machine (same setup as ball-on-disc) to simulate a rolling/sliding gear contact was used to study the impact of manufacturing method, grinding and superfinishing, on friction. To evaluate the extent to which friction and wear can be diminished by reducing surface roughness and changing surface orientation. Measurement results showed that the change of lubricant had an impact on friction in the mixed to boundary lubrication regimes similar to that of the change of main surface orientation. The results were compared with those from a parallel study involving a twin-disc machine, also used to simulate rolling/sliding contacts (see Figure). Measurements and simulations showed that the barrel-on-disc and twin-disc setups reflected the same friction trends. However, the friction coefficient using the barrel-on-disc setup was almost twice as large as that found using the twin-disc machine. The wear mechanisms also differed: micropits occurred on discs used in the twin-disc set-up whereas normal or no wear was found on the barrel-on-disc specimens. The difference in contact geometry is believed to be the main reason for the higher friction level in the barrel-on-disc machine. A computer contact analysis was used to clarify the differences using perfectly smooth and computer-generated textured surfaces.

  • 3.
    Bergseth, Ellen
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Study of surface roughness and surface orientation onfriction in rolling/sliding contacts: barrel-on-disc versustwin-discManuskript (preprint) (Övrigt vetenskapligt)
  • 4.
    Lewis, Roger
    et al.
    Department of Mechanical Engineering, University of Sheffield.
    Lewis, S.
    Department of Mechanical Engineering, University of Sheffield.
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Abbasi, Saeed
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    The Modification of a Slip Resistance Meter for Measurement of Railhead Adhesion2013Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 227, nr F2, s. 196-200Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this work was to find a quick, flexible and localised method for determining railhead adhesion. The proposed method is a pendulum rig, which has a rubber pad at the base of a swinging arm. The arm is released and as the rubber pad slides across the contact surface, energy is lost. This loss can be translated into a friction coefficient. Tests have been performed under dry and contaminated conditions, including water, oil and leaf layers both in the laboratory on extracted rail and in the field on live rail. Friction modifiers were also tested. The results of these tests are compared with data obtained using a hand-pushed tribometer. The performed study shows that the pendulum is a viable way to test adhesion levels in the field.

  • 5.
    Lyu, Yezhe
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.). Zhejiang University, China.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Wear between wheel and rail:A pin-on-disc study of environmental conditions and iron oxides2015Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 328-329, s. 277-285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Railways operate in an open environment where temperature, humidity, and the oxidation conditions are subjected to change. An experimental investigation used a pin-on-disc machine to examine the influence of environmental conditions and iron oxides on the wear performance of the wheel-rail contact. The wear mechanisms were analyzed using scanning electron microscopy and found to be highly dependent on the environmental conditions. On clean contacts, adhesive wear is predominant under low-moisture conditions, becoming more serious with decreasing temperature. With high moisture and at room temperature (i.e., 20. °C and 10. °C) oxide flakes would self-produce and protect the pins from severe wear, as oxidative wear is the main wear mechanism. Samples experienced a transformation of the wear mechanism from adhesive to oxidative with increasing humidity on clean contacts. Complex three-body wear in abrasion form has been determined to dominate oxidized contacts. Under dry conditions, pins underwent severe wear appearing as delamination at 20. °C and crushed wear debris at 3. °C. Raising the moisture level helps the pins to avoid severe wear.

  • 6.
    Olofsson, Ulf
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Zhu, Yi
    KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG. KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Abbasi, Saeed
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Lewis, Roger
    Lewis, Steve
    Tribology of the wheel rail contact: aspects of wear, particle emission and adhesion2013Ingår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 51, nr 7, s. 1091-1120Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The wheel−rail contact is a safety critical interface. Wear, particle emission and adhesion are all wheel−rail contact phenomena and are discussed here. All three phenomena are material and system parameters and are linked together. Different countermeasures to one phenomenon such as adhesion enhancement with a friction modifier can increase the wear in the contacting bodies. The wear of railway wheel and rail is linked to the number of airborne particles generated, but the exact number and size distribution of the aerosols particles are unknown. The main objective of this study is to review recent work in this field and to discuss future trends.

    Ladda ner fulltext (pdf)
    fulltext
  • 7.
    Olofsson, Ulf
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Löfving, S.
    Casselgren, J.
    Mayer, L.
    Nilsson, R.
    An optical sensor for the identification of low adhesion in the wheel rail contact2012Ingår i: 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, CM 2012, Southwest Jiaotong University , 2012, s. 318-323Konferensbidrag (Refereegranskat)
    Abstract [en]

    Low adhesion between railway wheel and rail, which is usually induced by contaminants such as water, oil, leaves etc., affects railway operation in terms of performance and safety. This study uses an optical sensor to identify different surface layers which cause low adhesion. A laboratory set up and field tests under various conditions were subject to the surface layer identification by the optical sensor. In addition, the friction coefficient was measured on the same surface layers. The results show that the sensor can distinguish between different surface layers. This information further linked to the levels of the friction coefficient, which can be used in the prediction system for the railway operator.

  • 8.
    Olofsson, Ulf
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Löving, S
    Casselgren, J
    Mayer, L
    Nilsson, R
    An optical sensor for the identification of low adhesion in the wheel/rail contact2012Ingår i: The international Journal of railway technology, ISSN 2049-5358, E-ISSN 2053-602X, nr 3, s. 97-110Artikel i tidskrift (Refereegranskat)
  • 9.
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Adhesion in the wheel-rail contact2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    To attract more customers and compete with other modes of transportation, railway transport needs to ensure safety, punctuality, high comfort, and low cost; wheel–rail adhesion, i.e., the transmitted tangential force in the longitudinal direction during driving and braking, plays an important role in all these aspects. Adhesion needs to be kept at a certain level for railway operation and maintenance. However, wheel−rail contact is an open system contact. Different contaminants can present between the wheel and rail surfaces, forming a third-body layer that affects the adhesion. Prediction of wheel–rail adhesion is important for railway operations and research into vehicle dynamics; however, this prediction is difficult because of the presence of contaminants.

    This thesis deals with wheel–rail adhesion from a tribological perspective. The five appended papers discuss wheel–rail adhesion in terms of dry conditions, lubricated conditions, leaf contamination, iron oxides, and environmental conditions. The research methodologies used are numerical modelling, scaled laboratory experiments, and field tests. The research objective is to understand the mechanisms of the adhesion loss phenomenon. 

    A numerical model was developed to predict wheel–rail adhesion based on real measured 3D surfaces. Computer simulation indicates that surface topography has a larger impact on lubricated than on dry contacts. Plastic deformation in asperities is found to be very important in the model. Ball-on-disc tests indicate that water can give an extremely low adhesion coefficient on smooth surfaces, possibly due to surface oxidation. Investigation of lubricated contacts at low speed indicates that oil reduces the adhesion coefficient by carrying a normal load, while adhesion loss due to water depends on the surface topography, water temperature, and surface oxidation. A field investigation indicates that leaves reduce the friction coefficient because of the chemical reaction between leaves and bulk materials. The thickness of the surface oxide layer was found to be an essential factor determining adhesion reduction. Pin-on-disc experiments found a transition in the friction coefficient with regard to the relative humidity, due to a trade-off between the water molecule film and the hematite on the surface. 

    Ladda ner fulltext (pdf)
    Dissertation
  • 10.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi. Zhejiang University, The State Key Lab of Fluid Power Transmission and Control, China .
    Lyu, Yezhe
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Mapping the friction between railway wheels and rails focusing on environmental conditions2015Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 324, s. 122-128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The coefficient of friction between railway wheels and rails is crucial to the railway adhesion, further greatly affecting railway operation and maintenance. Since the wheel-rail system is an open system, the coefficient of It is significantly influenced not only by various types of contaminants but also by environmental conditions. This paper conducted a set of pin-on-disc tests measuring the coefficient of friction focusing on the influence of environmental conditions (relative humidity and temperature). In addition, influences of iron oxides, leaves and glycol/water mixtures on the coefficient of friction were also studied. The friction results are shown in the form of friction maps. Results indicate that it oxides on the surfaces can prevent the samples from large friction reduction particularly at the low temperature. The friction mechanism is also discussed with the help of scanning electron microscopy photos. On the other hand, effects of leaves in reducing the coefficient of friction become limited with the presence of the glycol/water mixture.

  • 11.
    Zhu, Yi
    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.), Maskinelement.
    An adhesion model for wheel-rail contact at the micro level using measured 3d surfaces2012Ingår i: 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, CM 2012, Southwest Jiaotong University , 2012, s. 550-562Konferensbidrag (Refereegranskat)
    Abstract [en]

    Railway vehicles require a certain level of wheel-rail adhesion for efficient, reliable, and economical operation. A comprehensive wheel-rail contact model is useful for optimizing the adhesion, to simulatevehicle running conditions and to predict wear and rolling contact fatigue. A new contact model using measured 3D surfaces has been developed, comprising normal contact, rolling-sliding contact, flash temperature, and local friction coefficient models. This model can predict the local contact pressure, including the plasticity, local flash temperature, local tangential stress, local friction coefficient, and global adhesion coefficient. The influence of surface topography, creep, and speed on the adhesion coefficient, real contact area, and contact temperature is discussed. Results indicate that, due to increased contact area, the adhesion coefficient decreases with increased surface roughness, although the change is small. Furthermore, increasing speed reduces the adhesion coefficient due to the increasing contact temperature.

  • 12.
    Zhu, Yi
    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.), Maskinelement.
    An adhesion model for wheel-rail contact at the micro level using measured 3d surfaces2014Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 314, nr 1-2, s. 162-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Railway vehicles require a certain level of wheel-rail adhesion for efficient, reliable, and economical operation. A comprehensive wheel-rail contact model is useful for optimizing the adhesion, to simulate vehicle running conditions and to predict wear and rolling contact fatigue. A new contact model using measured 3D surfaces has been developed, comprising normal contact, rolling-sliding contact, flash temperature, and local friction coefficient models. This model can predict the local contact pressure, including the plasticity, local flash temperature, local tangential stress, local friction coefficient, and global adhesion coefficient. The influence of surface topography, creep, and speed on the adhesion coefficient, real contact area, and contact temperature is discussed. Results indicate that, due to increased contact area, the adhesion coefficient decreases with increased surface roughness, although the change is small. Furthermore, increasing speed reduces the adhesion coefficient due to the increasing contact temperature.

  • 13.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Chen, Hur
    Friction Between Wheel and Rail: A Pin-On-Disc Study of Environmental Conditions and Iron Oxides2013Ingår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 52, nr 2, s. 327-339Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The coefficient of friction between railway wheels and rails is crucial to railway operation and maintenance. Since the wheel-rail system is an open system, environmental conditions, such as humidity and temperature, affect the friction coefficient. Pin-on-disc testing was conducted to study the influence of environmental conditions and iron oxides on the coefficient of friction between the wheel and rail. The iron oxides were pre-created in a climate chamber. The surfaces of the tested samples were analysed using X-ray diffraction, scanning electron/focused ion beam microscopy, and Raman spectroscopy. Results indicate that the coefficient of friction decreases with increasing relative humidity (RH) up to a saturation level. Above this level, the coefficient of friction remains low and stable even when the RH increases. In particular, when the temperature is low, a small increase in the amount of water (i.e., absolute humidity) in the air can significantly reduce the coefficient of friction. At high humidity levels, a water molecule film can keep the generated haematite on the surfaces, counterbalancing the effect of rising humidity.

  • 14.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Nilsson, R.
    Stockholm public transport AB, Stockholm, Sweden.
    A field test study of leaf contamination on railhead surfaces2014Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 228, nr 1, s. 71-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Leaves on railway tracks affect the level of adhesion between the wheel and rail, especially in autumn. When crushed by wheels, leaves form a tarnished, low level of adhesion layer that sticks to the railhead and often requires mechanical removal. A Stockholm local traffic track with a long history of adhesion problems was subjected to field tests on railhead contamination. On five occasions under different conditions, spaced over a year, the friction coefficient was measured using a tribometer and samples of the rail were taken. The techniques of electron spectroscopy for chemical analysis and glow discharge optical emission spectrometry were conducted to determine the composition of the top layer of rail contaminants and hardness was measured using the nano-indentation technique. The tarnished layer contains much higher contents of calcium, carbon and nitrogen than do leaf residue layers and uncontaminated samples. These high element contents are generated from the leaf material, which chemically reacts with the bulk material. The hardness of the tarnished layer is one-fifth that of the non-tarnished layer of the same running band. A chemical reaction occurs from the surface to a depth of several microns. The thickness of the friction-reducing oxide layer can be used to predict the friction coefficient and extent of leaf contamination.

  • 15.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Olofsson, Ulf
    KTH, Tidigare Institutioner (före 2005), Maskinkonstruktion.
    Nilsson, R.
    Stockholm Public Transport AB, Stockholm, Sweden.
    A field test study of leaf contamination on railhead surfaces2012Ingår i: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Leaves on train tracks cause low adhesion between wheels and rails, especially in the autumn. A Stockholm local traffic track with a long history of adhesion problems was subject to field tests of railhead contamination. Over a year, on five occasions under different conditions, the friction coefficient was measured using a hand-push tribometer and rail samples were taken. ESCA and GD-OES analyses were conducted to determine the composition of the top layer of rail contaminants. The blackish layer contains much higher contents of calcium, carbon, and nitrogen than other samples indicating a chemical reaction occurring from the surface to a depth of several microns. The thickness of the friction-reducing oxide layer predicts the friction coefficient and leaf contamination extent. 

  • 16.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Persson, Karin
    Institute for Surface Chemistry, Life Science and Chemical Industries Section, Stockholm, Sweden.
    Investigation of factors influencing wheel-rail adhesion using a mini-traction machine2012Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 292/293, s. 218-231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adhesion in the wheel-rail contact is a key factor determining stable running conditions and safety during train driving and braking. This paper presents an experiment performed in a mini-traction machine to simulate the problems of low adhesion in the wheel-rail contact. Tests were conducted under dry conditions and using water or oil as lubricants to study the influence of surface roughness on the adhesion coefficient. The results indicate that the adhesion coefficient can be reduced to as low as 0.02 for smooth surfaces lubricated with water. For rougher contact surfaces, the water-lubricated tests indicate a higher adhesion coefficient than do oil-lubricated ones, but also a clear dependence on water temperature. The oil-lubricated tests indicate a very slight dependence of the adhesion coefficient on variation in rolling speed, temperature, and surface roughness.

  • 17.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Söderberg, Anders
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Adhesion modeling in the wheel-rail contact under dry and lubricated conditions using measured 3D surfaces2013Ingår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 61, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adhesion between wheels and rails plays an essential role in the safe, efficient, and reliable operation of a railway network. Particularly under lubricated conditions, which can be a natural lubricant as water and an applied lubricant as rail oil, trains can experience adhesion loss. This paper presents an adhesion model constructed using the measured 3D wheel-rail surfaces. The numerical model comprises of three parts: a normally loaded contact model; an interfacial fluid model; and a rolling-sliding contact model. Simulation examples use the numerical model to investigate how water or oil contamination might affect wheel-rail adhesion in contacts with different surface roughness levels. Simulation indicates that adhesion peaks are almost at the same creep on different surfaces. The fluid load capacity is inversely proportional to the adhesion coefficient, both of which are clearly dependent on vehicle speed. Oil reduces adhesion coefficient more than water does. The adhesion coefficient on the low roughness surfaces is higher than that on the generated smooth surfaces under oil-lubricated conditions while it is the opposite for water-lubricated contact.

  • 18.
    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 maps2013Ingår i: The international Journal of railway technology, ISSN 2049-5358, E-ISSN 2053-602X, Vol. 2, nr 3, s. 79-91Artikel i tidskrift (Refereegranskat)
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