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  • 251.
    Sundh, Jon
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    af Sätra, Ulf Skytte
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Influence of surface topography and surface modifications on seizure initiation in lean lubricated sliding contacts2007In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 262, p. 986-995Article in journal (Refereed)
    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.

  • 252.
    Sundh, Jon
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Relating contact temperature and wear transitions in a wheel-rail contact2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, no 1-2, p. 78-85Article in journal (Refereed)
    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.

  • 253.
    Sundh, Jon
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Sundvall, Krister
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Seizure and wear rate testing of wheel–rail contacts under lubricated conditions using pin-on-disc methodology2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, p. 1425-1430Article in journal (Refereed)
    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.

  • 254.
    Svahn, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Kassman Rudolphi, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Wallén, Erik
    The influence of surface roughness on friction and wear of machine element coatings2003In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 254, no 11, p. 1092-1098Article in journal (Refereed)
    Abstract [en]

    The use of low frictioncoatings like amorphous carbon or metal-doped carbon coatings on machineelements is constantly increasing. Most often, a surface treatment, e.g. grinding and polishing or honing, is required for optimal performance of the coated machineelement. This can be time consuming and costly.

    In this study, the effect of surfaceroughness on friction and sliding wear of two different coatings, one tungsten containing and one chromium containing coating, were examined using a ball-on-disc test. Ball bearing steel plates were grinded to different surfaceroughnesses and coated with the two different coatings.

    The friction was found to depend on surfaceroughness where the rougher surfaces gave higher friction coefficients. The wear rate for the a-C:W coating was found to be independent of the roughness, whereas the roughness had a strong influence on the wear rate for the a-C:Cr coating. This could partly be explained by a difference in wear mechanism, where fatigue wear was observed for the a-C:Cr coating but not for the a-C:W coating.

  • 255.
    Svahn, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Kassman-Rudolphi, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    On the effect of surface topography and humidity on lubricated running-in of a carbon based coating2006In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 261, no 11-12, p. 1237-1246Article in journal (Refereed)
    Abstract [en]

    The running-in behaviour of an amorphous carbon coating has been evaluated with respect to the substrate surface topography and the humidity of the surrounding environment. Four different surface treatments: polishing, grinding, wet-sandblasting and sandblasting, were employed prior to coating deposition. Sliding ball-on-disc tests were made in dry and humid air with four different oils: one PAO, one ester, one paraffinic mineral oil (all non-additivated) and one fully formulated mineral based engine oil. It was found that wet-blasted surfaces, having an Rq-value of 0.2 μm but much sharper asperities than typically ground surfaces, gave the coatings a better running-in ability compared with the other surfaces. The friction reduced rapidly from typical boundary lubricated values (0.09) to typical values of mixed boundary and EHL lubrication (0.04-0.045), without excessive wear of the steel counter body. No coating delamination was observed for coatings on this surface, and the mild wear was a fine polishing. This running-in behaviour was only observed in dry environments and only with non-additivated and non-polar oils, with PAO giving the lowest friction. In air of 50-60% relative humidity, no transition from boundary to EHL or mixed lubrication could be observed. For all oils and all surface topographies, the friction was always constant at levels typical for boundary lubrication. In dry air a thick tribo-layer composed of oxide was formed on the steel counter body but not in humid air. This oxide, along with a fine polishing of the surfaces and a macroscopic pressure reduction due to wear of the counter body, is believed to be important for the running-in ability.

  • 256.
    Sveen, Susanne
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. Dalarna University, Falun, Sweden.
    Andersson, J. M.
    Seco Tools AB, Fagersta, Sweden.
    Saoubi, Rachid M.
    Seco Tools AB, Fagersta, Sweden.
    Olsson, Mikael
    Dalarna University, Falun, Sweden.
    Scratch adhesion characteristics of PVD TiAlN deposited on high speed steel, cemented carbide and PCBN substrates2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 308, no 1-2, p. 133-141Article in journal (Refereed)
    Abstract [en]

    Modern tool materials, ranging from powder metallurgical high speed steel to super hard materials such as polycrystalline cubic boron nitride and diamond, are used as cutting tools in the metal cutting industry. In order to further improve the cutting performance, these tools are frequently coated by thin, hard PVD coatings such as TiN, TiAlN, AlCrO3, etc. In order to develop and design new PVD coatings it is important to characterize the mechanical properties of the coatings and understand the coating/ substrate deformation mechanisms in a tribological contact, e.g. metal cutting. For example, it is important to be aware that the mechanical properties of the substrate (tool material) have a significant impact on the practical coating adhesion and the coating failure mechanisms.

    In the present study scratch testing has been used in order to evaluate to increase the understanding of the mechanical response and potential coating failure modes of cathodic arc evaporated TiAlN deposited on high speed steel, cemented carbide and polycrystalline cubic boron nitride. Post-test characterization of the scratched samples using optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy were performed and the cohesive and adhesive surface failure mechanisms are described and related to the substrate material properties. The results clearly show that, although all substrate materials can be regarded as hard, they result in completely different coating failure mechanisms at the normal load corresponding to substrate exposure. Also, coating failure resulting in substrate exposure does not necessarily correspond to interfacial cracking resulting in adhesive fracture along the coating–substrate interface.

  • 257.
    Sveen, Susanne
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology. Linköping University, SE-581 83 Linköping, Sweden.
    Andersson, J
    Seco Tools.
    M’Sauobi, R
    Seco Tools.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Scratch adhesion characteristics of PVD TiAlN deposited on high speed steel, cemented carbide and PCBN substrates2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 308, no 1-2, p. 133-141Article in journal (Refereed)
    Abstract [en]

    Modern tool materials, ranging from powder metallurgical high speed steel to super hard materials such as polycrystalline cubic boron nitride and diamond, are used as cutting tools in the metal cutting industry. In order to further improve the cutting performance, these tools are frequently coated by thin, hard PVD coatings such as TiN, TiAlN, AlCrO3, etc. In order to develop and design new PVD coatings it is important to characterize the mechanical properties of the coatings and understand the coating/substrate deformation mechanisms in a tribological contact, e.g. metal cutting. For example, it is important to be aware that the mechanical properties of the substrate (tool material) have a significant impact on the practical coating adhesion and the coating failure mechanisms.

    In the present study scratch testing has been used in order to evaluate to increase the understanding of the mechanical response and potential coating failure modes of cathodic arc evaporated TiAlN deposited on high speed steel, cemented carbide and polycrystalline cubic boron nitride. Post-test characterization of the scratched samples using optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy were performed and the cohesive and adhesive surface failure mechanisms are described and related to the substrate material properties. The results clearly show that, although all substrate materials can be regarded as hard, they result in completely different coating failure mechanisms at the normal load corresponding to substrate exposure. Also, coating failure resulting in substrate exposure does not necessarily correspond to interfacial cracking resulting in adhesive fracture along the coating-substrate interface.

  • 258.
    Söderberg, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Andersson, Sören
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Simulation of wear and contact pressure distribution at the pad-to-rotor interface in a disc brake using general purpose finite element analysis software2009In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 267, no 12, p. 2243-2251Article in journal (Refereed)
    Abstract [en]

    Passenger car disc brakes are safety-critical components whose performance depends strongly on contact conditions at the pad-to-rotor interface. The interface can be classified as a conformal dry sliding contact. During braking both brake pad and rotor surfaces are worn, affecting the useful life of the brake as well as its behavior. This paper discusses how wear of the pad-to-rotor interface can be predicted using general purpose finite element analysis software. A three-dimensional finite element model of the brake pad and the rotor is developed to calculate the pressure distribution in the pad-to-rotor contact. A wear simulation procedure based on a generalized form of Archard's wear law and explicit Euler integration is used to simulate the wear of the brake pad under steady-state drag conditions.

  • 259.
    Tamil Alagan, Nageswaran
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Hoier, Philipp
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Zeman, Pavel
    Department of Production Machines and Equipment, Faculty of Mechanica lEngineering, Center of Advanced AerospaceTechnology, CzechTechnical University in Prague, Czech Republic.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Swede.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wretland, Anders
    GKN Aerospace Engine Systems AB,Trollhättan, Sweden.
    Effects of high pressure cooling in the flank and rake faces of WC tool on the tool wear mechanism and process conditions in turning of alloy 7182019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 434-435, article id 102922Article in journal (Refereed)
    Abstract [en]

    The exceptional properties of Heat Resistant Super Alloys (HRSA) justify the search for advanced technologiesthat can improve the capability of machining these materials. One such advanced technology is the applicationof a coolant at high pressure while machining, a strategic solution known for at least six decades. The aim is toachieve extended tool life, better chip control and improved surface finish. Another aim is to control the temperature in the workpiece/tool interface targeting for optimum cutting conditions. In most of the existing applications with high-pressure coolant media, the nozzles are positioned on the rake face side of the insert andthey are directed towards the cutting edge (the high-temperature area). The coolant is applied at high-pressureto improve the penetration of the cooling media along the cutting edge in the interface between the insert andworkpiece material (chip) as well as to increase chip breakability. However, the corresponding infusion ofcoolant media in the interface between the flank face of the insert and the work material (tertiary shear zone) hasbeen previously only scarcely addressed, as is the combined effect of coolant applications on rake and clearancesides of the insert. The present work addresses the influence of different pressure conditions in (flank: 0, 4 and8 MPa; rake: 8 and 16 MPa) on maximum flank wear, flank wear area, tool wear mechanism, and overall processperformance. Round uncoated inserts are used in a set of face turning experiments, conducted on the widely usedHRSA "Alloy 718" and run in two condition tests with respect to cutting speed (45 (low) and 90 (high) m/min).The results show that an increase in rake pressure from 8 to 16 MPa has certainly a positive impact on tool life.Furthermore, at higher vc of 90 m/min, cutting edge deterioration: due to an extensive abrasion and crack in thewear zone were the dominant wear mechanism. Nevertheless, the increase in coolant pressure condition to16 MPa reduced the amount of abrasion on the tool compared to 8 MPa. At the lower cutting speed, no crack orplastic deformation or extensive abrasion were found. When using 8 MPa pressure of coolant media on the flank,the wear was reduced by 20% compared to flood cooling conditions. Application of high-pressure cooling on theflank face has a positive effect on tool life and overall machining performance of Alloy 718.

  • 260.
    Telliskivi, Tanel
    KTH, Superseded Departments, Machine Design.
    Simulation of wear in a rolling-sliding contact by a semi-Winkler model and the Archard's wear law2004In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 256, no 7-8, p. 817-831Article in journal (Refereed)
    Abstract [en]

    The purpose of this work is to develop a method of controlling the friction and wear affecting the contact pair in rolling-sliding contact. The scope is in small-scale tribology by which mechanism of wear would be clarified on first hand by Archard's law. The prerequisite for using Archard's wear law in a simulation is proper piecewise linear modelling of contact at the substructural level, including prediction of deformations and relative motions for every part of the contact. The deformation level at the real contact depends on such parameters as normal forces. relative motions, geometry, surface tractions, etc. There is a need for a simulation tool that explains the role of these parameters. The present work simulates the well-known disc-on-disc test for dry wear. The deformation field due to normal load is solved by the Winkler mattress method. The tangential stress field is subsequently calculated knowing the normal pressure field, the penetration and the general rigid body movement for every subregion. The influence functions from potential theory are used to model the tangential traction and displacement field in the contact. The special computing excludes the need for the creep constants that depend on the Poisson's ratio and the result is not dependent on the shape of the contact area. Every rectangular cell is tested whether it is subject to sliding. The sliding distance is calculated by subtracting elastic displacements from the relative motion of the rigid body. The elastic deflections are reversible and exist both under the sticking region in contact and also in the sliding region. A comparison of the results of a simulation and a disc-on-disc test is presented. Good agreement was found for both wear and rolling friction at different load and creep levels.

  • 261.
    Telliskivi, Tanel
    et al.
    KTH, Superseded Departments, Machine Design.
    Olofsson, Ulf
    KTH, Superseded Departments, Machine Design.
    Wheel-rail wear simulation2004In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 257, no 11, p. 1145-1153Article in journal (Refereed)
    Abstract [en]

    This paper declares the method for the computation of the wheel-rail surface degradation in a curve where the major surface degradation phenomenon is a combination of wear and plastic deformation. Simulating the form change of the wheel-rail contacts help to identify the risk of severe or catastrophic wear resulting from increased train speeds and axle loads and can help in determining more efficient maintenance schedules for track and rolling stock. The method was previously used to simulate the form change in a two-roller contact. The progress is made in the terms of general geometry modelling, which makes differences in the various contact configurations. The normal contact problem is analysed using the modified Winkler method and calibrated using the results from FEM modelling of the wheel-rail contact with elastic-plastic material model. A piecewise approach and stick-slip analysis of the rolling-sliding contact solves the tangential problem. A linear wear law is used in the wear computation. The form change for a typical two-point contact in a low radius curve was analysed and discussed.

  • 262.
    Thomas, T. R.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK).
    Kenneth J. Stout 1941-2006: a memorial2009In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 266, no 5-6, p. 490-497Article in journal (Refereed)
    Abstract [en]

    Kenneth J. Stout was an important figure in the development of surface metrology, and in particular of roughness measurement and characterisation, during the last decades of the twentieth century. He made substantial contributions to the statistical characterisation of rough surfaces and the application of this work to tribological measurements. Later he was instrumental in developing and popularising practical techniques for three-dimensional description of surface roughness, including the well known "Birmingham 14" set of roughness parameters. Finally he was one of the first to promote the application of wavelet transforms to surface metrology. This memorial discusses his personal contribution to the subject and attempts to set it in the context of historical developments in the field. It includes what is hoped to be a definitive bibliography of his journal publications and those of his co-workers.

  • 263.
    Thomas, Tom R.
    et al.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Rosén, Bengt - Göran
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Zahouani, Hassan
    Laboratoire de Tribologie et Dynamique des Systèmes, ENIS, St. Etienne, France.
    Blunt, Liam
    Centre for Precision Technologies, Huddersfield University, Huddersfield, UK.
    El Mansori, Mohamed
    Laboratoire de Mécanique et de Procédés de Fabrication, Arts et Métiers ParisTech, Châlons en Champagne, France.
    Traceology, quantifying finishing machining and function: A tool and wear mark characterisation study2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, no 3-4, p. 553-558Article in journal (Refereed)
    Abstract [en]

    Traceology is defined as the study of wear marks and its history in criminology and archaeology is briefly described. It is proposed that the concept of traceology can be extended to machined surfaces, particularly those produced by abrasive techniques. A taxonomy of wear marks is outlined which would encompass both pits and scratches. Taxonomic implementations such as the morphology rose and the morphological tree are introduced. The general principles of traceology are illustrated by case studies from criminology, archaeology and abrasive machining processes.

  • 264.
    Toller, Lisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Norgren, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Sandvik Coromant R&D, Stockholm, Sweden..
    Life time of cemented carbide inserts with Ni-Fe binder in steel turning2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 376, p. 1822-1829Article in journal (Refereed)
    Abstract [en]

    Health concerns associated with cobalt powder are a strong motivator for conducting research on alternative binders for cemented carbides. It has previously been shown possible to make cemented carbides with alternative binders, which offer good hardness and toughness. However, it is not fully known if these cemented carbides can be successfully used as metal cutting tools. In this study we have tested turning inserts from cemented carbide with a nickel-iron binder and compared these with cobalt based reference inserts in dry face turning of steel in a pairwise comparison. To facilitate relevant comparisons, both the alternative binder and the reference cemented carbide are gradient sintered and coated in the same way as commercial turning grades. It is found that the life time in this dry face turning test is only approximately 15% shorter with the nickel-iron binder than with the cobalt reference, which motivates further studies with this alternative binder. Flaking of the coating and thus less coating adhesion was identified as one reason for the shorter life time.

  • 265.
    Torres, Hector
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. AC2T research GmbH.
    Vuchkov, Todor
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Slawik, Sebastian
    Saarland University, Department of Materials Science and Engineering.
    Gachot, Carsten
    Technische Universität Wien, Department of Engineering Design and Logistics Engineering, Vienna.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rodríguez Ripoll, Manel
    AC2T research GmbH.
    Self-lubricating laser claddings for reducing friction and wear from room temperature to 600 °C2018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 408-409, p. 22-33Article in journal (Refereed)
    Abstract [en]

    In this work, laser cladding has been employed for the preparation of nickel-based self-lubricating coatings featuring the addition of different combinations of soft metal solid lubricants such as Ag and Cu. Transition metal dichalcogenides (WS2, MoS2) were evaluated as precursors for encapsulating and uniformly distributing the soft metals throughout the microstructure. The tribological behaviour of the resulting claddings was evaluated under high temperature reciprocating sliding conditions, including two different counter body geometries that lead to very different ranges of contact pressures during testing. An improved tribological behaviour was observed for the self-lubricating claddings compared to the unmodified nickel-based alloy up to 600 °C, attributed to the presence of silver and the formation of lubricous sulfides during sample preparation due to the thermal degradation of the transition metal dichalcogenides precursors. Additionally, the role of the contact conditions observed when testing the self-lubricating claddings against flat pins instead of spherical counter bodies are discussed in terms of frictional and wear microstructural mechanisms.

  • 266. van der Heide, E.
    et al.
    Stam, E. D.
    Giraud, H.
    Lovato, G.
    Akdut, N.
    Clarysse, F.
    Caenen, P.
    Heikillä, I.
    Wear of aluminium bronze in sliding contact with lubricated stainless steel sheet material2006In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 261, no 1, p. 68-73Article in journal (Refereed)
    Abstract [en]

    Aluminium bronze, well known for its good sliding properties, is frequently applied as tool material in sheet metal forming (SMF) of stainless steel, e.g. for the production of washing, refrigeration and cooking equipment. The limited hardness of the material makes it, however, sensitive to tool wear that is: volumetric wear of the tool due to sliding contact with the sheet material. Conventional wear tests like the rubber wheel abrasion test or the Taber abrader test cannot be used to simulate the interaction of the tooling with lubricated sheet material. Dedicated tribo tests are therefore conducted with the slider-on-sheet test. The aim of the research is to measure the specific wear rate of aluminium bronze at SMF-like conditions. Experimental results showed a pronounced influence of lubricant selection and sheet material selection. The measured specific wear rate varied from 10(-8) mm(3)/N m for a smooth stainless steel sheet quality to 10(-6) mm(3)/N m for a rough surface quality.

  • 267.
    Venkatesh, L.
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India. .
    Pitchuka, Suresh Babu
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Sivakumar, G.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Gundakaram, Ravi C.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Samajdar, I.
    Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076, India.
    Microstructural response of various chromium carbide based coatings to erosion and nano impact testing2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 386-387, p. 72-79Article in journal (Refereed)
    Abstract [en]

    In this study, we demonstrate the microstructure dependency of erosion behaviour of laser clad, detonation sprayed and atmospheric plasma sprayed chromium carbide based coatings. The final chromium carbide content in all the coatings was a strong function of rapid solidification rate associated with the processes. In the laser clad coating majority of the chromium carbides re-solidified while in the thermally sprayed coatings chromium carbide re-solidification was hindered to a large extent. Hence, the final chromium carbide content in the thermally sprayed coating decreased with increased extent of particle melting during spraying. Decarburisation and oxidation during thermal spraying lead to the formation of chromium carbides with lower carbon content and chromium oxide(s). Laser clad and detonation sprayed coatings, with higher chromium carbide content, showed lower erosion rates and exhibited fewer brittle erosion events. Embrittlement due to excessive dissolution of chromium carbides into the matrix and poor splat bonding were found to be the reasons for higher erosion rate of the plasma sprayed coating. Scanning electron microscopy and quantification of single erodent impact events clearly established ductile material removal in the laser clad and detonation sprayed coating and brittle material removal in the plasma sprayed coating as the dominant mechanism(s). A good agreement was found between solid particle erosion testing and nano impact testing results.

  • 268.
    Venkatesh, Lakshmi Narayanan
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India; Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076, India.
    Venkataraman, B.
    Defence Metallurgical Research Laboratory (DMRL), Kanchanbagh, Hyderabad 500058, India.
    Tak, Manish
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Sivakumar, Ganapathy S.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Gundakaram, Ravi C.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Samajdar, Indradev S.
    Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076, India.
    Room temperature and 600 °C erosion behaviour of various chromium carbide composite coatings2019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 422-423, p. 44-53Article in journal (Refereed)
    Abstract [en]

    In this study, the erosion behaviour of laser clad chromium carbide-Ni rich alloy composite coatings with a wide range of carbide contents at room temperature and 600 °C were investigated. The variation in carbide content of the coatings was due to dilution from the substrate and the high cooling rate in the laser cladding process preventing re-solidification of the molten carbides. Erosion rate was observed to be a function of carbide content alone and was significantly higher at 600 °C as compared to room temperature. Erosion wear ratio (E90/E30) was also dependent on carbide content but decreased at higher temperature and higher carbide contents. A comparison of erosion behaviour with detonation and plasma sprayed counterparts showed the superior performance of laser clad coatings at 600 °C. The poor erosion performance of the detonation and plasma sprayed coatings was due to weak splat bonding. Thick oxide layer formed on the steel substrate after pre-oxidation resulted in its poor erosion performance.

  • 269.
    Wahlström, Jens
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Towards a cellular automaton to simulate friction, wear, and particle emission of disc brakes2014In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 313, no 1-2, p. 75-82Article in journal (Refereed)
    Abstract [en]

    Particle emissions originating from the sliding disc brake contact in disc brakes are a main contributor to PM10 in Europe. The macroscopic friction and wear behaviour can be explained, at the mesoscopic scale level, by the growth and destruction of contact plateaus. This paper further develops a cellular automaton that describes the mesoscopic contact situation by implementing friction, wear, and particle emission models based on data found in the literature. Three simulations at different load levels were conducted to investigate how contact pressure and temperature affect friction, wear, and particle emissions. The simulated behaviour correlates qualitatively with experimental observations found in the literature, but further work is necessary to obtain a quantitative correlation.

  • 270.
    Wahlström, Jens
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Lyu, Yezhe
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Matjeka, V.
    Söderberg, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics.
    A pin-on-disc tribometer study of disc brake contact pairs with respect to wear and airborne particle emissions2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 384-385, p. 124-130Article in journal (Refereed)
    Abstract [en]

    In the EU, PM10 from the wear of disc brakes can contribute up to 50% of the total non-exhaust emissions from road transport. The wear originates from the contact surfaces of the friction material and the disc. One possible way to decrease PM10 emissions is to change the materials of the contact pair in terms of composition and coatings. The wear and particle emissions of three novel friction material formulations, one novel disc formulation, one disc WC/CoCr coating realized with the HVOF technique, and one disc surface treatment realized by a nitriding process, were investigated. Pin-on-disc tests were run to rank the novel materials in terms of specific wear rate and particle number and mass rate. The results show that it is possible to achieve a reduction in particle emissions of up to 50% by changing the materials of the contact pair.

  • 271.
    Wahlström, Jens
    et al.
    KTH.
    Söderberg, Anders
    KTH.
    Olander, Lars
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Jansson, Anders
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Olofsson, Ulf
    KTH.
    A pin-on-disc simulation of airborne wear particles from disc brakes2010In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 268, no 5-6, p. 763-769Article in journal (Refereed)
    Abstract [en]

    A novel test method was used to study the concentration and size distribution of airborne wear particles from disc brake materials. A pin-on-disc tribometer equipped with particle counting instruments was used as test equipment. Material from four different non-asbestos organic (NAO) pads and four different low metallic (LM) pads were tested against material from grey cast iron rotors. The results indicate that the low metallic pads cause more wear to the rotor material than the NAO pads, resulting in higher concentrations of airborne wear particles. Although there are differences in the measured particle concentrations, similar size distributions were obtained. Independent of pad material, the characteristic particle number distributions of airborne brake wear particles have maxima around 100, 280, 350, and 550 nm.

  • 272.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Söderberg, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering (name changed to Building Service and Energy Systems 2012-03-01).
    Jansson, Anders
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    A pin-on-disc simulation of airborne wear particles from disc brakes2010In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 268, no 5-6, p. 763-769Article in journal (Refereed)
    Abstract [en]

    A novel test method was used to study the concentration and size distribution of airborne wearparticles from disc brake materials. A pin-on-disc tribometer equipped with particle countinginstruments was used as test equipment. Material from four different non-asbestos organic(NAO) pads and four different low metallic (LM) pads were tested against material from greycast iron rotors. The results indicate that the low metallic pads cause more wear to the rotormaterial than the NAO pads, resulting in higher concentrations of airborne wear particles.Although there are differences in the measured particle concentrations, similar size distributionswere obtained. Independent of pad material, the characteristic particle number distributions ofairborne brake wear particles have maxima around 100, 280, 350, and 550 nm.

  • 273. Wang, Lixin
    et al.
    Johannesson, Carl Michael
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Zhou, Qiang
    Effect of surface roughness on attachment ability of locust Locusta migratoria manilensis2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 332, p. 694-701Article in journal (Refereed)
    Abstract [en]

    To explore how surface roughness affects locust's attachment ability, friction force of locust Locusta migratoria manilensis on substrates with variable roughness was measured with an insect micro-force measurement system. Extensive values of the friction force were acquired, respectively exhibiting the trends of inverted parabola variation, linear pattern growth and saturation period with the increased surface roughness. Obviously small values of the friction force were generated by locusts on substrates possessing a particular roughness range. The morphology and structure of locust attachment organ were examined and quantitively analyzed with a scanning electron microscope. Based on the acquired structure information, a schematic was proposed to explain the interaction between the attachment organ and the surface irregularity, also a mechanical analysis was conducted to present the effect of surface asperity on locust's claw tip. Results demonstrated that surface roughness with appropriate values can considerably reduce locust's attachment ability via simultaneously restricting the generation of mechanical interlock and adhesive attachment. The achieved conclusion gives a further interpretation to friction behavior of insect on variable substrates, also provides theory for biomimetic designing a slippery plate utilized for trapping plague locusts.

  • 274.
    Wentzel, Henrik
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Olsson, Mårten
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Mechanisms of dissipation in frictional joints: influence of sharp contact edges and plastic deformaiton2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 265, no 11-12, p. 1814-1819Article in journal (Refereed)
    Abstract [en]

    In the present study frictional and plastic dissipation in joints are investigated by means of the finite element method. The Coulomb friction model is used in simulations and the results are compared to experimental measurements. Some of the contacts considered contain numerous internal sharp edges that are localized inside the overall contact region. For joints with sharp contact edges an elastic material model with Coulomb friction is inappropriate because of the sliding-over-edge that occurs in such joints. Here, the sliding-over-edge phenomenon is studied with an elastic-plastic material model in some detail. The phenomenon involves very high plastic strains locally, material build-up in front of the edge and large plastic dissipation. A summation technique for the total dissipation in joints is presented, where each local sliding-over-edge contribution is taken into account. The results are compared to experiments. It is shown that plastic deformation is an important contributing factor to the total dissipation in joints with highly non-conformal surfaces.

  • 275.
    Wiest, Martina
    et al.
    University of Leoben.
    Gebretsadik, Elias Kassa
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Daves, Werner
    University of Leoben.
    Nielsen, Jens
    Chalmers University of technology.
    Ossberger, Heinz
    VAE.
    Assessment of methods for calculating contact pressure in wheel-rail/switch contact2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 265, no 9, p. 1439-1445Article in journal (Refereed)
    Abstract [en]

     Two models for wheel-rail rolling contact that are based on the half-space assumption are compared in this paper: Hertz and the non-Hertzian method implemented in the computer program CONTACT. These two models are further restricted by the assumption of linear-elastic material behaviour. Moreover, one elastic and one elastic-plastic finite element model of the contact are investigated with the commercial code ABAQUS. The finite element method is not limited by the half-space assumption or applicable to a linear-elastic material model only. The objective is to assess the four methods based on calculated contact pressure, contact patch size and penetration depth. Contact loads and contact locations, used as input data in the analysis, are taken from a vehicle dynamics simulation in the software GENSYS. The comparison is performed at a given cross-section in the crossing panel of a selected turnout design. To fulfil the requirements of the half-space assumption, the dimensions of the contact area must be small compared to the radii of curvature of the bodies in contact. On the selected cross-section, however, the half-space assumption does not hold since the smallest radius of rail curvature at the contact point is 13 mm, which is comparable to the largest semi-axis of the contact area. Nevertheless, it is found that the contact pressure distributions calculated using Hertz and CONTACT correlate well with those results obtained from the finite element method as long as no plastification of the material occurs.

  • 276.
    Wiklund, Daniel
    et al.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK).
    Rosén, Bengt-Göran
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK).
    Gunnarsson, Lars
    KIMAB, Corrosion and Metals Research Institute AB, S-114 28 Stockholm, Sweden.
    Frictional mechanisms in mixed lubricated regime in steel sheet metal forming2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 264, no 5-6, p. 474-479Article in journal (Refereed)
    Abstract [en]

    The friction is of critical importance to sheet metal forming operations. It affects the flow of material in the tool and thereby the scrap rate and final quality of products. In the experimental work the frictional response was measured in a bending under tension (BUT) test under mixed lubricated conditions. The study includes stainless steel, but previous research on carbon steels, coated and uncoated, are discussed also. The experimental results could be explained by the theory of pad bearings. The frictional response showed a correlation to the surface topography, e.g. the amplitude parameter (Sq) and texture aspect ratio parameter (Str). When predicting the frictional response of surfaces with multi-component distributions, the standard deviation of the distribution above the mean line could be used.

  • 277.
    Wiklund, Daniel
    et al.
    Chalmers University of Technology.
    Wihlborg, Anders
    Halmstad University, School of Business, Engineering and Science, Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Rosén, Bengt-Göran
    Halmstad University, School of Business, Engineering and Science, Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Evaluation of surface topography parameters for friction prediction in stamping2004In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 257, no 12, p. 1296-1300Article in journal (Refereed)
    Abstract [en]

    The continued globalisation of the automotive industry, leading to increasing demands for competitiveness and escalating legislative requirements, is the main driving force of research activities of steel sheet surfaces. Recent studies on the stamping process have been carried out among others within AUTOsurf, a project funded by the European Community, and by Wihlborg and Crafoord. The purpose of this study was to evaluate the viability of the proposed parameters for friction prediction. Seventeen different surface topographies were investigated. The sheet materials were either, hot-dip galvanised, electrogalvanised or galvannealed, and electron beam or electric discharged textures. The frictional response was measured in a bending under tension (BUT) test under mixed lubricated conditions. This BUT test simulates the conditions of the die radius in a stamping tool. The laboratory test differs from the experimental work performed in AUTOsurf which simulated the conditions of the holding-down plate. In spite of the differences in test equipments in AUTOsurf, e.g. the rotational friction tester (RTF), on a comparison the correlation of frictional response was significant. But neither of the proposed parameters could predict the frictional response with sufficient accuracy in this study. In addition, the friction model in AUTOsurf describes peak lubrication as a dragging phenomenon on sliding surfaces. The movement eased friction in inverse proportion to the average peak area. However, the trend in this study showed the opposite, movement eased friction proportionally to the average peak area. The result indicates a switch of dominant friction mechanism when the sliding velocity is increased, i.e. from a dragging phenomenon at low velocities to micro-hydrodynamic wedge effects at high velocities.

  • 278.
    Wiklund, U
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gunnars, J
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Hogmark, S
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Influence of residual stresses on fracture and delamination of thin hard coatings1999In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 232, no 2, p. 262-269Article in journal (Other academic)
    Abstract [en]

    The risk of fracture and delamination of residually stressed coating systems is examined. Stress concentrations are generated at the interface of coated systems where the substrate deviates from bring perfectly smooth, flat and infinitely large. Using fin

  • 279.
    Wiklund, U.
    et al.
    Department and Division of Materials Science, Uppsala University.
    Gunnars, Jens
    Luleå tekniska universitet.
    Högmark, S
    Department and Division of Materials Science, Uppsala University.
    Influence of residual stresses on fracture and delamination of thin hard coatings1999In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 232, no 2, p. 262-269Article in journal (Refereed)
    Abstract [en]

    The risk of fracture and delamination of residually stressed coating system is examined. Stress concentrations are generated at the interface of coated systems where the substrate deviates from being perfectly smooth, flat and infinitely large. Using finite element calculations, such stresses induced at pores, edges or scratches are analysed for a number of representative coatings/substrate systems. The effect of the interface topography, coating thickness and elastic mismatch on the interfacial stresses are investigated. Generally, thin coatings compared to the interface topography are less sensitive to residual stress induced failure. At a critical coating thickness, normal stress across the interface of a magnitude comparable to that of the residual stress level is induced, which may initiate coating delamination. The interface stress state becomes independent of the coating thickness if the coating is thicker than about three times the amplitude of the interface roughness. The interface stress scales approximately linearly with the maximum inclination of the surface profile. It is demonstrated experimentally that the high residual stress in ceramic coatings may cause local coating fracture and delamination at, e.g., the tip of an edge or at rough substrate when the coating is thick relative to the edge radius or the surface topography, respectively.

  • 280.
    Wiklund, Urban
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Casas, B
    Stavlid, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Evaporated vanadium nitride as a friction material in dry sliding against stainless steel2006In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 261, no 1, p. 2-8Article in journal (Refereed)
    Abstract [en]

    High friction coefficients and severe galling have always hampered machining of stainless steel. Lubricants and special procedures in cutting and forming operations are common practice. Coatings deposited on tools in order to alter the adhesive nature of the stainless steel is an appealing idea and it has long been proposed as a solution to the problem. However, to date no coating, which is also capable of enduring the temperatures encountered during machining has successfully fulfilled that prophecy. Despite being one of the first PVD tool coatings commercially produced, titanium nitride (TiN) is still also one of the most widely used. A vast number of coatings have indeed joined TiN for tooling applications but none of these has excelled in contact with stainless steel. Using quantum calculations vanadium nitride (VN), a ceramic compound closely related to TiN, has recently been suggested to be much less prone to adhesive cladding to iron alloys than TiN. Experimental verification of those results is the focus of this work. Reactive electron beam evaporation is regarded as the premier method for producing TiN. Using that very method, VN and TiN coatings were produced for this work and tested in sliding in contact with stainless steel and other selected materials. In these tests VN is shown to be less prone to galling as compared to TiN, especially against stainless steel. [All rights reserved Elsevier]

  • 281.
    Wikström, Victoria
    et al.
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Wear of bearing liners at low speed rotation of shafts with contaminated oil1993In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 162-164, no 2, p. 996-1001Article in journal (Refereed)
    Abstract [en]

    An experimental and theoretical investigation was carried out to investigate the relationship between wear of bearing liners and low shaft speed, contamination, oil temperature, bearing load and time. Experimentally, it was found that oil with no external debris added produced only slight polishing of the liners. When the oil was contaminated with 0.02 wt.% iron or quartz particles of a known distribution (less than 32 μm diameter), increased wear was detected. Also, comparison of the results of the clean and iron-contaminated tests with those for quartz-contaminated oil show that the character of the worn liner area has changed from evenly rubbed zones to equally divided polished stripes in the circumferential direction. During the tests, the bearing friction was measured. In no test did the friction rise drastically, as would have been the case if severe wear and scoring had appeared. In actual applications, though, this sometimes occurs. This may be explained by severe contamination in industrial lubricating systems, with larger particles and higher debris concentration. A clean lubricating system is thus crucial in order to avoid heavy wear at low speeds. The experimental results were then compared with those indicated theoretically for film thickness at low speed. The theoretical minimum film thickness at low speed was much smaller than the size of the debris. The results indicate that if So-1 <=340, B/D >=0.73 and C>=0.18 mm, no severe wear will occur.

  • 282.
    Wredenberg, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Scratch testing of metals and polymers: Experiments and numerics2009In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 266, no 1-2, p. 76-83Article in journal (Refereed)
    Abstract [en]

    An experimental and numerical study of the scratch test performed on metals and polymers was conducted. The materials tested, being both metallic and polymeric, were related to the well known Johnson's parameter, often used to correlate indentation experiments. The aim was to determine whether it was possible to use the numerical approach presented by Wredenberg and Larsson [F. Wredenberg, P.-L Larsson, On the numerics and correlation of scratch testing, journal of Mechanics of Materials and Structures 2 (2006) 573-594] to describe the scratch mechanism and of course also to investigate whether or not important scratch quantities can be determined with sufficient accuracy from standard scratch experiments.

  • 283.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Application of an inclined, spinning ball-on-rotating disc apparatus to simulate railway wheel and rail contact problems2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 374-375, p. 46-53Article in journal (Refereed)
    Abstract [en]

    Railway wheel-rail contacts involve various combinations of slip, rolling, and creepage. Traditionally, a twin-disc apparatus is used to simulate such problems. However, there are out of plane forces and motions involved in the actual situation. Therefore, the possibility of using a commercially-made, inclined-axis spinning ball-on-disc test rig was investigated to better simulate wheel and rail contact problems. By setting two angle parameters both the lateral and spin creepage can easily be applied to the contact. Traction measurements were conducted, and good agreement was found by comparing the present results with other available experimental data. The effects of the spin creepage on wear were studied in particular. An asymmetrical wear pattern was obtained from cases that applied a low longitudinal creepage and a spin creepage, corresponding to a rail running on a curved track. To the best of the authors' knowledge, this work is the first of its kind to be done using a laboratory-scale tribometer.

  • 284.
    Xiao, Li
    et al.
    Department of Production Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Rosén, Bengt-Göran
    Halmstad University, School of Business, Engineering and Science, Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Amini, Naser
    Volvo Car Corporation, Gothenburg, Sweden.
    Surface lay effect on rough friction in roller contact2004In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 257, no 12, p. 1301-1307Article in journal (Refereed)
    Abstract [en]

    Surface lay describes the direction of the predominant surface pattern. A properly designed surface texture configuration has been recognised as a vital issue affecting lubrication and sliding in machinery applications in the literature. Gaining understanding of this tribological phenomenon is no doubt beneficial in facilitating the production of more efficient machine parts and thus reduces production cost. This paper describes an experimental method to investigate the effect of surface lay on lubricated rolling/sliding of ground roller surfaces. By using the rough friction test rig, different surface lay contacts can be simulated and the friction can be measured. Friction behaviour was interpreted in terms of Stribeck curves (friction coefficient as the function of Hersey parameter [ηv/p]). Results show that an optimal contact lay angle that provides a minimum friction value is achievable through rig testing. The relative sliding speed direction has a symmetrical effect on friction at the same lay orientation; for sliding speed angles less than about 80, the larger the angle, the lower the friction, and vice versa. © 2004 Elsevier B.V. All rights reserved.

  • 285.
    Xiao, Li
    et al.
    Department of Production Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Rosén, Bengt-Göran
    Halmstad University, School of Business, Engineering and Science, Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Amini, Naser
    Volvo Car Corporation, Gothenburg, Sweden.
    Nilsson, Per H.
    Volvo Technological Development, Gothenburg, Sweden.
    A study on the effect of surface topography on rough friction in roller contact2003In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 254, no 11, p. 1162-1169Article in journal (Refereed)
    Abstract [en]

    The friction behaviour of gear teeth in the context of tribology can have a strong effect on housing vibration, noise and efficiency. One of the parameters that greatly influences the friction under certain running conditions is surface roughness. In this work, rough friction was studied in lubricated sliding of roller surfaces, which were manufactured to simulate the real gear surfaces. By examining 3D surface topography of two mating bodies, both surface roughness and its effect on friction behaviour can be studied. In a previous study, a rough-friction test rig has been designed, constructed and initially verified. The types of surfaces involved in this study are ground, shot-peened, phosphated and electrochemically deburred. These rollers were subjected to the same friction testing procedures. Roller surfaces were then examined, and correlation between the topography and the frictional behaviour was analysed. Friction behaviour was interpreted in terms of Stribeck curves (friction coefficient as the function of Hersey parameter (ην/p)). The results showed that electrochemically deburred and certain phosphated surfaces provide lower friction coefficient values which are competitive to fine-ground surfaces in lubricated rolling/sliding contact. © 2003 Elsevier Science B.V. All rights reserved.

  • 286.
    Yang, Jing
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. University of Politecn Cataluna, Spain.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Johansson-Joesaar, Mats P.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. SECO Tools AB, Sweden.
    Llanes, L.
    University of Politecn Cataluna, Spain; University of Politecn Cataluna, Spain.
    Influence of substrate microstructure and surface finish on cracking and delamination response of TiN-coated cemented carbides2016In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 352-353, p. 102-111Article in journal (Refereed)
    Abstract [en]

    The cracking and delamination of TiN-coated hardmetals (WC-Co cemented carbides) when subjected to Brale indentation were studied. Experimental variables were substrate microstructure related to low (6 wt% Co) and medium (13 wt% Co) binder content, and surface finishes associated with grinding and polishing stages before film deposition. Brale indentation tests were conducted on both coated and uncoated hardmetals. Emphasis has been placed on assessing substrate microstructure and subsurface finish effects on load levels at which cracking and delamination phenomena emerge, the type of cracking pattern developed, and how fracture mechanisms evolve with increasing load. It is found that polished and coated hardmetals are more brittle (radial cracking) and the adhesion strength (coating delamination) diminishes with decreasing binder content. Such a response is discussed on the basis of the influence of intrinsic hardness/brittleness of the hardmetal substrate on both cracking at the subsurface level and effective stress state, particularly regarding changes in shear stress component. Grinding promotes delamination compared to the polished condition, but strongly inhibits radial cracking. This is a result of the interaction between elastic-plastic deformation imposed during indentation and several grinding-induced effects: remnant compressive stress field, pronounced surface texture and micro cracking within a thin altered subsurface layer. As a consequence, coating spallation prevails over radial cracking as the main mechanism for energy dissipation in ground and coated hardmetals. (C) 2016 Elsevier B.V. All rights reserved.

  • 287.
    Zahouani, Hassan
    et al.
    Laboratoire de Tribologie et de Dynamique des Systèmes, Ecole Centrale de Lyon, Ecully, FRANCE; Ecole Nationale d'Ingénieurs, Saint-Etienne, France.
    Rosén, Bengt-Göran
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Thomas, Tom R.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    10th International Conference on Metrology & Properties of Engineering Surfaces: Guest editorial2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 264, no 5-6, p. 381-381Article in journal (Refereed)
  • 288. Zhu, Y
    et al.
    Olofsson, U
    Persson, Karin
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Investigation of factors influencing wheel-rail adhesion using a mini-traction machine2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 292-293, p. 218-231Article in journal (Refereed)
    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.

  • 289.
    Zhu, Yi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi. Zhejiang University, The State Key Lab of Fluid Power Transmission and Control, China .
    Lyu, Yezhe
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Mapping the friction between railway wheels and rails focusing on environmental conditions2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 324, p. 122-128Article in journal (Refereed)
    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.

  • 290.
    Zhu, Yi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    An adhesion model for wheel-rail contact at the micro level using measured 3d surfaces2014In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 314, no 1-2, p. 162-170Article in journal (Refereed)
    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.

  • 291.
    Zhu, Yi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), 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 machine2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 292/293, p. 218-231Article in journal (Refereed)
    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.

  • 292.
    Ånmark, Niclas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Björk, Thomas
    Swerea KIMAB.
    Ganea, Anna
    Sandvik Coromant.
    Ölund, Patrik
    Ovako Hofors.
    Hogmark, Sture
    Uppsala Unniversitet.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    The effect of inclusion composition on tool wear in hard part turning using PCBN cutting tools2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 334, p. 13-22Article in journal (Refereed)
    Abstract [en]

    This work reports on hard part turning of carburizing steels using a PCBN cutting tool in fine machining. Emphasis is on the link between composition of the inclusions in work material and wear mechanisms of the cutting tool. A Ca-treated machinability improved 20NiCrMo steel was included together with three other carburizing steels with different inclusion characteristics.

    Machining tests were conducted to examine cutting tool life and its balance between excessive flank wear or crater wear. The wear mechanisms were examined using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and a secondary electron (SE) detector.

    The longest tool life was obtained when cutting the Ca-treated steel. The improved machinability is linked to the deposition of complex (Mn,Ca)S and (Ca,Al)(O,S) protective slag layers that form on the rake face of the cutting tool during machining. Cutting in this steel also resulted in a typical ridge formation in the tool edge crater. Transfer of workpiece material to the rake face crater is characteristic in hard part turning of steel with high cleanliness. This is suggested to be related to the lack of the sulphides that lubricate conventional machinability treated steels, and that the crater wear of low-sulphur steel is more pronounced than for steels with higher sulphur content.

  • 293.
    Ånmark, Niclas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, KIMAB. KTH Royal Institute of Technology, Sweden.
    Björk, Thomas
    RISE - Research Institutes of Sweden, Materials and Production, KIMAB.
    Ganea, Anna
    Sandvik Coromant, Sweden.
    Ölund, Patrik
    Ovako, Sweden.
    Hogmark, Sture
    Uppsala University, Sweden.
    Karasev, Andrey
    KTH Royal Institute of Technology, Sweden.
    Jönsson, Pär Göran
    KTH Royal Institute of Technology, Sweden.
    The effect of inclusion composition on tool wear in hard part turning using PCBN cutting tools2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 334-335, p. 13-22Article in journal (Refereed)
    Abstract [en]

    This work reports on hard part turning of carburizing steels using a PCBN cutting tool in fine machining. Emphasis is on the link between composition of the inclusions in work material and wear mechanisms of the cutting tool. A Ca-treated machinability improved 20NiCrMo steel was included together with three other carburizing steels with different inclusion characteristics. Machining tests were conducted to examine cutting tool life and its balance between excessive flank wear and crater wear. The wear mechanisms were examined using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and a secondary electron (SE) detector.The longest tool life was obtained when cutting the Ca-treated steel. The improved machinability is linked to the deposition of complex (Mn,Ca)S and (Ca,Al)(O,S) protective slag layers that form on the rake face of the cutting tool during machining. Cutting in this steel also resulted in a typical ridge formation in the tool edge crater. Transfer of workpiece material to the rake face crater is characteristic in hard part turning of steel with high cleanliness. This is suggested to be related to the lack of the sulfides that lubricate conventional machinability treated steels, and that the crater wear of low-sulfur steel is more pronounced than for steels with higher sulfur content.

  • 294.
    Öqvist, Mona
    Luleå tekniska universitet.
    Numerical simulations of mild wear using updated geometry with different step size approaches2001In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 249, no 1, p. 6-11Article in journal (Refereed)
    Abstract [en]

    Wear of engineering components is often a critical factor influencing the product life. Prediction and simulation of wear is therefore an important matter in engineering. Numerical simulations of wear of a cylindrical steel roller oscillating against a steel plate are performed with a special version of the finite element program NIKE2D. The simulation was done in steps and the pressure and the sliding distance was recalculated as the surface geometry changed. The wear model used in the simulations is global. The global wear model gives an opportunity to predict the change in shape of the surfaces in a fast and efficient manner, it will however not incorporate information on how the wear occurs on molecular scale.Two different strategies in selecting the time step for the geometry update were used. In the first case a larger time step was used in the first wear steps and a smaller one in the final ones, and in the second a constant time step was used. To get information on the coefficient of friction an experiment was performed. This experiment was used to evaluate the simulation as well as give the proper input to the simulation. The simulated topography of the surfaces was compared with experimental results and the agreement was good. It can be concluded that allowing the time step to differ between the wear steps will speed up the wear simulation considerably. A large time step for the geometry update will cause some waviness of the cylindrical surface but when the smaller time steps have been used at the end of the computation this error will disappear.

  • 295.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Högmark, Sture
    Ångström Laboratory, Uppsala University.
    Selected papers from those presented at the 14th Nordic Symposium on Tribology (Nordtrib 2010) Storforsen, June 8-11, 20102011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 273, no 1, p. 1-Article in journal (Other academic)
3456 251 - 295 of 295
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