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  • 151. Lewis, R.
    et al.
    Olofsson, Ulf
    KTH, Superseded Departments, Machine Design.
    Mapping rail wear regimes and transitions2004In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 257, no 08-jul, p. 721-729Article in journal (Refereed)
    Abstract [en]

    This paper outlines work carried out to produce maps of rail material wear coefficients taken from laboratory tests run on twin disc and pin-on-disc machines as well as those derived from measurements taken in the field. Wear regimes and transitions are identified using the maps and defined in terms of slip and contact pressure. Wear regimes are related to expected wheel/rail contact conditions and contact points (rail head/wheel tread and rail gauge/wheel flange). Surface morphologies are discussed and comparisons are made between field and laboratory data.

  • 152. Lewis, S. R.
    et al.
    Lewis, R.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    An alternative method for the assessment of railhead traction2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, no 1-2, p. 62-70Article in journal (Refereed)
    Abstract [en]

    Work has been carried out to develop a fast test method for the determining of railhead traction levels. Current methods used in the field are time consuming and offer relatively little control of external or test parameters. A pendulum rig has been used for this investigation and adapted to measure railhead friction levels under various states of contamination. The rig consists of an aluminium tubular pendulum; on the end of which is a spring mounted, rubber pad (slider pad). The rig functions on the same principles as used in a Charpy impact test, i.e. energy is lost as the slider pad comes into contact with a surface (in this case the rail head). This loss in kinetic energy is measured and can be translated into a friction coefficient. Tests have been carried out to validate the placing of the contaminants on the rail prior to testing and also to determine the setup of the rig. High speed video has also been used to determine the speed of the slider. The pendulum was also tested in the field and showed good correlation in comparison with a hand pushed Tribometer. Pendulum results have been compared to those from twin disk simulations of the wheel/rail contact and good correlation can also be found.

  • 153.
    Li, M.
    et al.
    Department of Mechanical and Industrial Engineering, Louisiana State University.
    Lingesten, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    McCarthy, D.M.C.
    Volvo CE.
    Lundin, Joakim
    Volvo Construction Equipment , Volvo CE.
    Model validation and uncertainty analysis in the wear prediction of a wet clutch2016In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 364-365, p. 112-121Article in journal (Refereed)
    Abstract [en]

    An uncertainty quantification analysis is performed to further investigate the nature of the “two-stage” wear process of the paper-based friction lining in a wet clutch. In this approach, the results of a computerized wear prediction model are examined through sensitivity analysis and a model validation that utilizes the Monte Carlo (MC) method. Extensive computational results that take into account the uncertainty and variability in the input data are presented to gain insight into the evolution of temperature and wear during the engagement process.

  • 154.
    Li, Xinmin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sosa, Mario
    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.), Machine Design (Div.).
    A pin-on-disc study of the tribology characteristics of sintered versus standard steel gear materials2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Though powder metallurgy (PM) allows manufacturing of complex components, including gears, we lack knowledge of the tribological performance of PM versus standard steel gear materials. Using a pin-on-disc machine, we simulate the sliding part of gear tooth contact in boundary and mixed lubricated regions, comparing the tribological characteristics of two sintered gear materials with those of a standard gear material. The comparison considered damage mechanisms, wear, and friction between these materials in different configurations (i.e., standard versus standard, sintered versus sintered, and sintered versus standard). The results indicate that, for pairings of the same gear materials, i.e., RS–RS (16MnCr5), AQ–AQ (Distaloy AQ+0.2% C), and Mo–Mo (Astaloy 85Mo+0.2% C), RS has a lower friction coefficient. For PM and RS combinations, both PM pins have lower friction coefficients with RS disc material than do RS pins with PM disc materials. For the wear coefficient, at low and high speeds, RS pins always display better wear resistance than do AQ or Mo pins because of their high hardness and compacted microstructure. For RS–PM combinations, Mo pins display higher wear resistance than do AQ pins because their larger and more numerous pores enable good lubrication. Pins in the Mo–RS combination displayed the highest wear resistance, mainly because the pores in Mo discs hold lubricant, lubricating the contact surface and preventing adhesive wear. For the RS pin in the Mo–RS combination and the AQ pin in RS–AQ, the damage mechanism is slight adhesive wear and scuffing. For pins in the PM–PM, RS–PM, AQ–RS, and RS–RS combinations, the damage mechanism is a heavier scuffing-type adhesive wear.

  • 155.
    Lindholm, Per
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Svahn, Fredrik
    Method and surface roughness aspects for the design of DLC coatings2006In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 261, no 1, p. 107-111Article in journal (Refereed)
    Abstract [en]

    The design of coatings for highly loaded component contacts, such as bearings, gears and valve train components involves several important factors, including load, friction, lubrication, surface characteristics and material parameters. This paper presents an investigation of the influence of the material, coating thickness and surface roughness on tensional stress levels for coatings that are more compliant than the substrate material. Specifically the effect of multiple asperity contact is studied in three dimensions. The simulation is based on a finite element model where the load is applied as several interacting Hertzian pressure distributions. The results show that the surface structure, in combination with the elastic properties of the coating, has a large influence on the tensional stress level in the coating. The highest tensional stress level in the coating occurs when contact spots almost overlap neighbouring cells and at the same time the size of the contact spots is in the same order of magnitude as the coating thickness.

  • 156.
    Lindholm, Per
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Svahn, Fredrik
    Study of thickness dependence of sputtered-carbon coating for low friction valve lifters2006In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 261, no 3-4, p. 241-250Article in journal (Refereed)
    Abstract [en]

    This paper presents test and stress calculation results of two thicknesses (0.7 and 1.7 mu m) of amorphous a-C:Cr-coated standard rollers for a cam roller follower valve train mechanism in a diesel truck engine. The coated rollers were tested for 100 h on equipment simulating near-normal engine running conditions. For the thicker coating, the results show mainly polishing wear and low wear on the cam surface. The thinner coating delaminates and the cam shows higher wear. The delamination may be the product of high tensional stresses in the thinner coating, as determined by finite element calculations. These tensions allow surface cracks to propagate down to the chromium interlayer and vice versa.

  • 157. Lindholm, Per
    et al.
    Svahn, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Study of thickness dependence of sputtered-carbon coating for low friction valve lifters2006In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 261, no 3-4, p. 241-250Article in journal (Refereed)
    Abstract [en]

    This paper presents test and stress calculation results of two thicknesses (0.7 and 1.7 mu m) of amorphous a-C:Cr-coated standard rollers for a cam roller follower valve train mechanism in a diesel truck engine. The coated rollers were tested for 100 h on equipment simulating near-normal engine running conditions. For the thicker coating, the results show mainly polishing wear and low wear on the cam surface. The thinner coating delaminates and the cam shows higher wear. The delamination may be the product of high tensional stresses in the thinner coating, as determined by finite element calculations. These tensions allow surface cracks to propagate down to the chromium interlayer and vice versa.

  • 158.
    Lindquist, Mattias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wilhelmsson, Ola
    Jansson, Ulf
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tribofilm formation and tribological properties of TiC and nanocomposite TiAlC coatings2009In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 266, no 3-4, p. 379-387Article in journal (Refereed)
    Abstract [en]

    In a recent work a concept for self lubricating low friction TiC and nanocomposite TiAlC coatings was developed. Here we further investigate the mechanical and tribological properties of these coatings. Under identical deposition conditions, the addition of Al initiates the formation of a nanocomposite consisting of (Ti,Al)C grains in an amorphous carbon matrix. The coefficient of friction is lowered from 0.2 to below 0.1 in a pin-on-disc test against steel with unaffected coating wear rate. The lower friction is attributed to a more extensive formation of amorphous carbon and graphitisation on both the counter surface and in the coating wear track. The addition of Al also reduces coating hardness, Young's modulus and the residual stress, which can be explained by the weak carbide-forming ability of Al and the formation of a nanocomposite microstructure.

  • 159.
    Lindquist, Mattias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tribofilm formation from TiC and nanocomposite TiAlC coatings, studied with Focused Ion Beam and Transmission Electron Microscopy2009In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 266, no 9-10, p. 988-994Article in journal (Refereed)
    Abstract [en]

    This work demonstrate how two different carbide coatings respond very differently to tribological stress and their very different ability to provide low friction tribofilms in dry sliding against steel. Both coatings, TiC and TiAlC, were deposited by DC-magnetron sputtering, but while the TiC is a thermodynamically stable coating, the TiAlC is made metastable with the addition of Al, and therefore releases carbon upon tribological testing. Thus, the TiAlC coating is shown to be self-lubricating on the atomic scale which makes very low friction   achievable. The primary interest in this study is the differences in the tribofilms formed on the steel balls that have been sliding against  the two coatings. Cross-section samples for transmission electron  microscopy were extracted from the ball tribofilms using a focused ion beam instrument. X-ray photoelectron spectroscopy and Raman analysis were employed to provide information on the chemical and structural  characteristics of the tribofilms. It was shown that tribofilms on steel balls largely inherit the structure and composition that evolve   in the coating wear tracks, that the tribofilm microstructure greatly affects the friction level. It was also shown that tribofilm delamination, occurring with tribofilm growth, was initiated in weak ribbon like regions inside the tribofilm.

  • 160.
    Lingesten, Niklas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lund, Martin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lundin, Joakim
    Volvo Construction Equipment.
    Mäki, Rikard
    Volvo Construction Equipment.
    Apparatus for continuous wear measurements during wet clutch durability tests2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 288, p. 54-61Article in journal (Refereed)
    Abstract [en]

    Wet clutches are used in many applications today such as automatic transmissions and limited slip differentials in cars as well as in heavy duty equipment such as wheel loaders. The present study is concerned with the wear and engagement behavior of wet clutches in the latter type of application. A test rig is developed in which the wet clutch engagement is monitored during an arbitrary number of test cycles.This rig has many similarities with the SAE #2 test rig in that they are both inertia type test rigs. However, the test rig presented here has several original parts from heavy duty equipment in production incorporated into it. The data collection includes a continuous measurement of the position of the piston used to apply force on the clutch pack in addition to the separator disc temperatures, hydraulic actuating pressure and torque transfer characteristics. The measurements of the piston position can then be related to the clutch wear during a long test series.

  • 161.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lubrication of a rotating ball in normal approach1989In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 130, no 1, p. 203-212Article in journal (Refereed)
    Abstract [en]

    An experimental study has been made of the degree of lubrication, which is defined as the number of interacting asperities, when a rotating spherical body approaches a plane during rotation. The normal velocity was varied between 0.1 and 0.5 m s-1 and the sliding velocity between 0 and 9.2 m s-1. The experiments show that the oil viscosity is the most important lubricant parameter. The degree of lubrication is not affected by either the normal velocity, the pressure viscosity coefficient or the shear strength proportionality constant. An increase in the sliding velocity gives a decrease in lubrication of between 25% and 65% depending on the surface roughness and type of lubricant. The surface roughness is also a most important factor impeding good lubrication. To avoid wear one has to increase the viscosity from 8 to 145 mm2 s-1 if the mean surface roughness Ra is increased from 0.01 to 0.14.

  • 162.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lubrication of machine elements during combined squeeze and sliding motion1993In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 169, no 2, p. 161-166Article in journal (Refereed)
    Abstract [en]

    The motion when two parts in a machine come into contact can be a normal, sliding or rolling approach, or a combination of the three. The case of combined normal and sliding motion can be very unfavourable from the point of view of lubrication. Nevertheless, this situation does occur, for example in a gear mesh and in heavily loaded rolling-element bearings.The following factors in the case of lubrication of machine elements during combined normal and sliding motion were studied experimentally: oil viscosity, surface texture, shear strength of oil and maximum pressure. The pressure also involves the parameters normal force, Young's modulus, Poisson's ratio and surface curvature.Based on the experimental results, an equation has been deduced which describes how the above-mentioned factors influence the permissible limiting sliding velocity Vsl without oil film breakdown: Vsl=0.127×10-6(v0.1-1.575)(ψ-13.1-1.707)(3840-pmax)This equation agrees well with results from experiments carried out by other authors, and is valid if combined sliding and impact between the machine elements, resulting in a limited contact time, are present.

  • 163.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Viscosity dependence of squeeze/sliding lubrication1992In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 155, no 1, p. 31-36Article in journal (Refereed)
    Abstract [en]

    It has been found experimentally that increased lubricant viscosity will increase the permissible sliding speed without leading to breakdown of the lubricant film while the normal velocity is held at a constant level. The dependence approaches a square root function. It is also apparent that with a squeeze velocity present, increased sliding velocity will decrease the oil-film thickness. An initial attempt at an explanation is given in terms of a combination of Reynolds' equation and further experimental results.

  • 164.
    Lundberg, Jan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics. Division of Operation and Maintenance, Luleå University of Technology.
    Rantatalo, Matti
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics. Division of Operation and Maintenance, Luleå University of Technology.
    Wanhainen, Christina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Division of Geosciences and Environmental Engineering, Luleå University of Technology.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics. Division of Fluid and Experimental Mechanics, Luleå University of Technology.
    Measurements of friction coefficients between rails lubricated with a friction modifier and the wheels of an IORE locomotive during real working conditions2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 324-325, p. 109-117Article in journal (Refereed)
    Abstract [en]

    The real friction coefficients between the rails and the wheels on a 360. t and 10,800. kW IORE locomotive were measured using the locomotive[U+05F3]s in-built traction force measurement system. The locomotive consisted of two pair-connected locomotives had a CoCo+CoCo bogie configuration, and hauled a fully loaded set of 68 ore wagons (120. t/wagon). The measurements were performed both on rails in a dry condition and on rails lubricated with a water-based top-of-rail (ToR) friction modifier on the Iron Ore Line between the cities of Kiruna and Narvik in Northern Sweden and Norway, respectively. Since full-scale measurements like these are costly, the friction coefficients were also measured at the same time and place using a conventional hand-operated tribometer, with and without the ToR friction modifier. The most important results are that the real friction coefficient is definitely not constant and is surprisingly low (0.10-0.25) when the ToR friction modifier is used, and that it is also significantly dependent on the amount of ToR friction modifier. A large amount will reduce the friction coefficient. Furthermore, it is concluded that the real friction coefficients are in general lower than the friction coefficients measured with the hand-operated tribometer. A final remark is thus that the use of a water-based ToR friction modifier can give excessively low friction, which can result in unacceptably long braking distances.

  • 165.
    Lundberg, Jan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Östensen, Jan Ove
    Luleå tekniska universitet.
    Åström, Henrik
    Luleå tekniska universitet.
    High-speed video photographs of lubrication breakdown in squeeze-sliding contact1992In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 157, no 2, p. 427-433Article in journal (Refereed)
    Abstract [en]

    Using photographs from a high-speed video camera it was confirmed that the main part of breakdown of a lubricating film will appear at the end of the contact time for a contact simultaneously subjected to squeeze and sliding motion. This corresponds with earlier findings using totally different equipment for electric detection of the asperity contact. The present investigation used glass and steel as the lubricated surfaces, instead of steel and steel as was the case in the earlier investigation. In combination with far less stiff equipment, the new materials gave longer contact time and larger elastic deformations of the contact bodies. It was also verified that increased surface roughness, increased sliding velocity and decreased viscosity increase the risk of oil film breakdown

  • 166.
    Lundgren, Sarah M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Persson, Karin
    Clarke, Jim
    Brewer, Mark
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Friction and wear of unsaturated fatty acids in alkane solution under boundary conditions2007In: Wear, ISSN 0043-1648, E-ISSN 1873-2577Article in journal (Other academic)
  • 167. Lundén, Roger
    et al.
    Ekberg, Anders
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Grassie, Stuart
    Special edition of "Wear" to contain CM2015 proceedings2016In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 366, p. 1-2Article in journal (Refereed)
  • 168.
    Lyphout, Christophe
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Bolelli, Giovanni
    University of Modena and Reggio Emilia, Italy.
    Smazalova, Eva
    University of West Bohemia, Czech Republic.
    Sato, Kazuto
    Fujimi Incorp, Japan.
    Yamada, Junya
    Fujimi Incorp, Japan.
    Houdkova, Sarka
    University of West Bohemia, Czech Republic.
    Lusvarghi, Luca
    University of Modena and Reggio Emilia, Italy.
    Manfredini, Tiziano
    University of Modena and Reggio Emilia, Italy.
    Influence of hardmetal feedstock powder on the sliding wear and impact resistance of High Velocity Air-Fuel (HVAF)sprayed coatings2019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 430-431, p. 340-354Article in journal (Refereed)
    Abstract [en]

    The present work aimed to clarify how the characteristics of WC-CoCr hardmetal feedstock powders, namely the grain size of the WC carbides and of the binder and the compressive strength of the sintered aggregates, affect the dry sliding wear and impact resistance of coatings deposited by High Velocity Air-Fuel (HVAF)spraying. Ball-on-Disc tests, which mimic a sliding wear process in the presence of hard asperities as it may occur e.g. in hydraulic seal joints or papermaking components, resulted in mild wear through near-surface microscale plastic flow, the exact nature of which was significantly affected by WC size. Finite element simulations of a single-asperity sliding process indeed showed that large WC grains concentrate contact stresses, thus undergoing very localised deformation. It is experimentally seen that repeated deformation of the carbide grains resulted in their cracking and pull-out. Uniformly distributed, fine carbides allowed the matrix to take on some stress, thus undergoing more homogeneous plastic flow. Block-on-Ring tests elicited adhesive wear as it may happen e.g. in metal-to-metal contacts (e.g. petrochemical valves). This could be effectively restrained by low matrix mean free path. Cyclic impact resistance of coarse-grained coatings was better than that of fine-grained ones, because of better large-scale cohesive strength.

  • 169.
    Lyu, Yezhe
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Bergseth, Ellen
    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.
    Lindgren, Anders
    Tyréns AB, Stockholm, Sweden.
    Höjer, Martin
    Tyréns AB, Sweden.
    On the relationships among wheel–rail surface topography, interface noise and tribological transitions2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 338-339, p. 36-46Article in journal (Refereed)
    Abstract [en]

    Noise from the wheel-rail interface is a troublesome side effect when railway vehicles negotiate rail curves and straight tracks. A laboratory study using two pin-on-disc tribometers to simulate the pure sliding process in a wheel-rail contact investigated the relationships between surface topographies, tribological aspects and emitted noise. The influence of five different initial surface topographies manufactured by polishing and grinding (transverse and circular) was studied. Polished samples yielded the highest friction coefficient and wear rate because of strong adhesion. Samples with manufacturing traces vertical to the sliding direction produced the lowest friction coefficient and wear rate, and were dominated by ploughing and abrasion. Samples with manufacturing marks parallel to the sliding direction exhibited a medium level in both fiction coefficient and wear rate; the wear mechanism was combined ploughing-adhesion. Noise emission followed the same pattern as the friction coefficients: the highest sound pressure levels occurred for the polished samples and the lowest for the samples with transverse manufacturing marks. Wear transitions from mild to severe wear were always accompanied by an increase in sound pressure of about 10 dB. The transitions also changed the sound pressure amplitude distribution from a narrow banded to a broader banded. 

  • 170.
    Lyu, Yezhe
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Bergseth, Ellen
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Wahlström, Jens
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A pin-on-disc study on the tribology of cast iron, sinter and composite railway brake blocks at low temperatures2019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, p. 48-52Article in journal (Refereed)
    Abstract [en]

    Most freight wagons in the EU use cast iron brake blocks. Cast iron brake blocks have a stable braking capability in different environmental conditions, but wear down the wheel tread quickly. Therefore, there is a need to understand the tribology of other brake block materials. A pin-on-disc tribometer placed in a temperature-controlled chamber is used to investigate the tribology of cast iron, sinter and composite railway brake blocks at low ambient temperatures. Pins made from different brake blocks are tested with discs made from steel wheels. Both friction coefficient and wear are evaluated at five different temperatures from + 10 to − 30 °C. The cast iron block demonstrated the greatest wear at − 10 and − 20 °C, due to the ductile-to-brittle transition at low temperatures. The worn graphite from cast iron is likely to become a solid lubricant, reducing the friction at − 10 and − 20 °C. For the composite brake block, a gradual decrease in friction with decreasing temperature was found. The sinter brake block was not sensitive to changes in ambient temperature. The sliding speed in the current study is relatively low and further study at higher speed is suggested in order to evaluate the tribological performance of different brake blocks.

  • 171.
    Lyu, Yezhe
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Zhu, Yi
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Zhejiang University, China.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Wear between wheel and rail:A pin-on-disc study of environmental conditions and iron oxides2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 328-329, p. 277-285Article in journal (Refereed)
    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.

  • 172.
    Malakizadi, Amir
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Ghasemi, Rohollah
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Behring, Carsten
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Olofsson, Jakob
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Nyborg, Lars
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Krajnik, Peter
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Effects of workpiece microstructure, mechanical properties and machining conditions on tool wear when milling compacted graphite iron2018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 410-411, p. 190-201Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to investigate the tool performance when machining compacted graphite iron (CGI) alloys. A comparison was made between solid solution strengthened CGI including various amounts of silicon (Si-CGI) and the pearlitic-ferritic CGI as a reference material. The emphasis was on examining the influence of microstructure and mechanical properties of the material on tool wear in face milling process. Machining experiments were performed on the engine-like test pieces comprised of solid solution strengthened CGI with three different silicon contents and the reference CGI alloy. The results showed up-to 50% lower flank wear when machining Si-CGI alloys, although with comparable hardness and tensile properties. In-depth analysis of the worn tool surfaces showed that the abrasion and adhesion were the dominant wear mechanisms for all investigated alloys. However, the better tool performance when machining Si-CGI alloys was mainly due to a lower amount of abrasive carbo-nitride particles and the suppression of pearlite formation in the investigated solid solution strengthened alloys.

  • 173.
    Mann, B. S.
    et al.
    BHEL, Corporate R&D Division, Vikasnagar, Hyderabad.
    Prakash, Braham
    High temperature friction and wear characteristics of various coating materials for steam valve spindle application2000In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 240, no 1-2, p. 223-230Article in journal (Refereed)
    Abstract [en]

    Various coatings such as chromium carbide (deposited by plasma spraying and detonation gun techniques), chromium oxide, chromium oxide + titania + silica, NiCrAlY, and Al2O3 + Ni all deposited by plasma spraying; stelliting, and surface nitriding have been applied on X20CrMo V121 steel. This steel is used for high temperature applications such as steam turbine valve spindle. Friction and wear behavior of the surface coated and treated materials have been studied at an elevated temperature of 550°C while rubbing against graphite-filled stellited steel. These studies have been carried out on SRV optimol reciprocating tribometer. Test parameters for tribological studies have been selected with a view to simulate operating conditions encountered in operation. Additionally, the structure, porosity, hardness, bond strength, and thermal cycling behaviour of these surface coated/treated materials have been characterised. Based on these laboratory investigations, chromium carbide coating deposited by plasma spraying technique has been identified as the most suitable coating for steam turbine valve spindle application. Process parameters have been established for deposition of chromium carbide coating by plasma spraying technique on actual valve spindles. The field results obtained are found to be commensurate with the laboratory findings.

  • 174.
    Moghaddam, Pouria Valizadeh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Vuorinen, Esa
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The role of retained austenite in dry rolling/sliding wear of nanostructured carbide-free bainitic steels2019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 428-429, p. 193-204Article in journal (Refereed)
    Abstract [en]

    The dry rolling/sliding wear of nanostructured bainite has been investigated and compared with that of a conventional quenched and tempered bearing steel. In order to elucidate the role of retained austenite on the wear performance, high silicon hypereutectoid bearing steel with an identical alloy composition was heat treated to obtain different microstructures with similar hardness and different amounts of retained austenite. The results indicate that the nanostructured bainite can meet the minimum hardness requirements for bearing applications. Moreover, the nanostructured bainite outperformed the tempered martensitic steel in terms of wear resistance. The work hardening capacity and thus wear resistance increases due to the transformation of retained austenite into martensite. The results of XRD analyses show that the higher stability of retained austenite and strength of bainitic ferrite leads to better wear performance. It is demonstrated that the stability of retained austenite outweigh the influence of retained austenite content on wear resistance. Adhesion and oxidation were identified as the main wear mechanisms. In addition to microstructure, surface oxidation also plays a prominent role in determining the wear resistance. 

  • 175.
    Moreno, Silvia Suñer
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Bladen, Catherine L.
    Institute of Medical and Biological Engineering, University of Leeds.
    Gowland, Nicholas
    Institute of Medical and Biological Engineering, University of Leeds.
    Tipper, Joanne L.
    Institute of Medical and Biological Engineering, University of Leeds.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Investigation of wear and wear Particles from a UHMWPE/multi-walled carbon nanotube nanocomposite for total joint replacements2014In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 317, no 1-2, p. 163-169Article in journal (Refereed)
    Abstract [en]

    Ultra high molecular weight polyethylene (UHMWPE) has been extensively used as a bearing surface in joint prostheses. However, wear debris generated from this material has been associated with osteolysis and implant loosening. Alternative materials, such as polymer composites, have been investigated due to their exceptional mechanical properties. The goal of the present work was to investigate the wear rate, size and volume distributions, bioactivity and biocompatibility of the wear debris generated from a UHMWPE/Multi-walled carbon nanotube (MWCNT) nanocomposite material compared with conventional UHMWPE. The results showed that the addition of MWCNTs led to a significant reduction in wear rate. Specific biological activity and functional biological activity predictions showed that wear particles from the UHMWPE/MWCNT nanocomposite had a reduced osteolytic potential compared to those produced from the conventional polyethylene. In addition, clinically relevant UHMWPE/MWCNT wear particles did not show any adverse effects on the L929 fibroblast cell viability at any of the concentrations tested over time. These findings suggest that UHMWPE/MWCNT nanocomposites represent an attractive alternative for orthopaedic applications.

  • 176.
    MSaoubi, R.
    et al.
    Seco Tools AB, Sweden.
    Alm, O.
    Seco Tools AB, Sweden.
    Andersson, J. M.
    Seco Tools AB, Sweden.
    Engstrom, H.
    Seco Tools AB, Sweden.
    Larsson, T.
    Seco Tools AB, Sweden.
    Johansson-Joesaar, M. P.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Seco Tools AB, Sweden.
    Schwind, M.
    Seco Tools AB, Sweden.
    Microstructure and wear mechanisms of texture-controlled CVD alpha-Al2O3 coatings2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 376, p. 1766-1778Article in journal (Refereed)
    Abstract [en]

    In the present study, the microstructure and wear mechanisms of texture controlled CVD alpha-Al2O3 layers with (001), (012) and (100) growth textures were investigated in single point turning of C45 carbon steel at low and high cutting speeds. The experimental coatings were investigated by FEG-SEM, EBSD and a combination of FIB and analytical TEM techniques prior to and after machining. Significant texture effects on wear performance of the alpha-Al2O3 coating layers were observed, confirming results from previous wear studies in the context of machining AISI 4140 carbon steel. The wear mechanisms of the coating layers were further interpreted in the light of thermal, mechanical and frictional conditions occurring at the tool chip contact interface. Possible deformation mechanisms of the alpha-Al2O3 layers under the conditions of high pressure and temperatures acting on the tool surface are discussed. The high dislocation density revealed by the TEM observations in the subsurface alpha-Al2O3 layers was attributed to the activation of a basal slip deformation mechanism resulting from the combined action of the shear stress field and high temperature acting on the tool surface. It is suggested that the enhanced and more uniform near surface deformation capability of (001) alpha-Al2O3 is responsible for the improved machining performance. (C) 2017 Elsevier B.V. All rights reserved.

  • 177.
    M'Saoubi, R
    et al.
    Seco Tools AB, Sweden .
    Johansson, M. P.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. Seco Tools AB, Sweden .
    Andersson, J. M.
    Seco Tools AB, Sweden .
    Wear mechanisms of PVD-coated PCBN cutting tools2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2, p. 1219-1229Article in journal (Refereed)
    Abstract [en]

    The wear characteristics of PVD coated (TiN, TiSiN, TiAlN, and AlCrN) polycrystalline cubic boron nitride (PCBN) cutting tools were compared to those of uncoated PCBN during single point turning of case hardened steel 16MnCr5. Post-cutting observations of the worn inserts were performed using high resolution field emission gun scanning electron microscope (FEG-SEM) in combination with focus ion beam (FIB) and analytical transmission electron microscopy (TEM). Substantial differences in the wear behaviour of the different coating materials could therefore be observed. In particular, a remarkable tendency for TiN to exhibit plastic deformation was revealed while TiSiN exhibited a more brittle behaviour evidenced by adhesive wear and microchipping. TiAlN and AlCrN on the other hand exhibited less workpiece adhesion. The wear mechanisms of the above thin coating layers are discussed and interpreted in light of thermal, mechanical, and frictional conditions occurring at the tool-chip contact.

  • 178.
    Nilsson, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of different surface modification technologies on friction of conformal tribopair in mixed and boundary lubrication regimes2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 273, no 1, p. 75-81Article in journal (Refereed)
    Abstract [en]

    Moving machine assemblies are generally designed to operate in full film lubrication regime to ensure high efficiency and durability of components. However, it is not always possible to ensure this owing to changes in operating conditions such as load, speed, temperature etc. The overall frictional losses in machines are dependent on the operating lubrication regimes (boundary, mixed or full-film). The present work is thus aimed at investigating the role of different surface modification technologies on friction of a sliding bearing/roller tribopair both in boundary and mixed lubrication regimes. A special test rig comprising of two bearings was built for the experimental studies. Tribological tests were conducted in a wide speed range to enable studies in boundary and mixed lubrication regimes. The influence of application of different surface modification technologies on both the sliding bearing and the roller surfaces on friction has been studied. The rollers used in these studies were provided with five different coatings (hard DLCs and a soft self-lubricating coating). Additionally, two uncoated rollers having different surface roughness were also studied. Uncoated bearings were used in all tribopairs except two. These two bearings were coated with DLC and phosphate coatings respectively and uncoated rollers were the mating counterparts. Friction measurements were made on the new as well as the previously run-in surfaces. It was found that the rollers with self-lubricating coating resulted in lowest boundary friction closely followed by the rollers with the hardest DLC coatings. The DLC coating applied on to the bearing showed lower boundary friction after running-in. Mixed friction has been found to be mainly dependent on the surface topography characteristics of both the original and the run-in surfaces of bearings and rollers. The harder DLC coatings and the phosphated bearing showed the lowest mixed friction due to an efficient running-in of the bearing surface.

  • 179.
    Nilsson, M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Olsson, M
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Microstructure and mechanical properties of materials for the finishing stands of the hot strip mill for steel rollingIn: Wear, ISSN 0043-1648, E-ISSN 1873-2577Article in journal (Refereed)
  • 180.
    Nilsson, Malin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Olsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Microstructural, mechanical and tribological characterisation of roll materials for the finishing stands of the hot strip mill for steel rolling2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 307, no 1-2, p. 209-217Article in journal (Refereed)
    Abstract [en]

    The microstructure, mechanical and tribological properties for three different materials, high speed steel, high chromium iron and indefinite chill iron, used for hot strip mill work rolls have been evaluated. Microstructural characterisation was performed using light optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The mechanical and tribological properties were evaluated using micro-Vickers indentation and scratch testing in combination with post-test microscopy. The microstructures of the investigated materials were found to be rather complex with a number of secondary phases and also materials with similar nominal composition display significant differences with respect to distribution, size and morphology of carbides. Scratch testing, including detection of friction coefficient, acoustic emission and penetration depth, gives valuable information concerning the mechanical and tribological response on a microscopic level of the investigated materials. Type, amount, distribution, size and morphology of the secondary phases in the materials have a strong impact on the surface deformation and wear mechanisms during scratching. Cracking and chipping are frequently observed in connection to the ridges surrounding the scratches. However, cross-sectional analyses of the scratched microstructures reveal that cracking of the brittle carbide phases may extend to significant depths > 100 gm, reducing the mechanical strength of the material. Based on the results, it is believed that a more isotropic microstructure, e.g., obtained via a powder metallurgy process, with finer carbides would result in improved properties and performance in a hot rolling application.

  • 181.
    Nilsson, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology. Tribomaterials group, The Ångström Laboratory, Uppsala University, Sweden.
    Microstructural, mechanical and tribological characterisation of roll materials for the finishing stands of the hot strip mill for steel rolling2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 307, no 1-2, p. 209-217Article in journal (Refereed)
    Abstract [en]

    The microstructure, mechanical and tribologicalproperties for three different materials, High Speed Steel, High Chromium ironand Indefinite Chill iron, used for hot strip mill work rolls have beenevaluated. Microstructural characterisation was performed using light opticalmicroscopy, scanning electron microscopy and energy dispersive X-rayspectroscopy. The mechanical and tribological properties were evaluated usingmicro Vickers indentation and scratch testing in combination with post-testmicroscopy. The microstructures of the investigated materials were found to berather complex with a number of secondary phases andalso materials with similar nominal composition display significant differenceswith respect to distribution, size and morphology of carbides. Scratch testing,including detection of friction coefficient, acoustic emission and penetrationdepth, gives valuable information concerning the mechanical and tribologicalresponse on a microscopic level of the investigated materials. Type,amount, distribution, size and morphology of the secondary phases in thematerials have a strong impact on the surface deformation and wear mechanismsduring scratching. Cracking and chipping are frequently observed in connectionto the ridges surrounding the scratches. However, cross-sectional analyses ofthe scratched microstructures reveal that cracking of the brittle carbidephases may extend to significant depths, >100 µm, reducing the mechanicalstrength of the material. Based on the results, it is believed that a moreisotropic microstructure, e.g. obtained via a powder metallurgy process, withfiner carbides would result in improved properties and performance in a hotrolling application.

  • 182.
    Nilsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Olsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tribological testing of some potential PVD and CVD coatings for steel wire drawing dies2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 273, no 1, p. 55-59Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the possibility to replace cemented carbide wire drawing dies with CVD or PVD coated steel dies. Material pick-up tendency, friction and wear characteristics of four different commercial coatings - CVD TiC and PVD (Ti,Al)N, CrN and CrC/C - in sliding contact with ASTM 52100 bearing steel were evaluated using pin-on-disc testing. The load bearing capacity of the coating/substrate composites was evaluated using scratch testing. The results show that the friction characteristics and material pick-up tendency of the coatings to a large extent is controlled by the surface topography of the as-deposited coatings which should be improved by a polishing post-treatment in order to obtain a smooth surface. Based on the results obtained in this study, three different coatings - CrC/C, TiC and dual-layer TiC/CrC/C - are recommended to be evaluated in wire drawing field tests. CrC/C and TiC are recommended due to their intrinsic low friction properties and material pick-up tendency in sliding contact with steel. The dual-layer is recommended in order to combine the good properties of the two coatings CrC/C (low shear strength) and TiC (high hardness). 

  • 183.
    Nilsson, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribological testing of some potential PVD and CVD coatings for steel wire drawing dies2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 273, no 1, p. 55-59Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the possibility to replace cemented carbide wire drawing dies with CVD or PVD coated steel dies. Material pick-up tendency, friction and wear characteristics of four different commercial coatings – CVD TiC and PVD (Ti,Al)N, CrN and CrC/C – in sliding contact with ASTM 52100 bearing steel were evaluated using pin-on-disc testing. The load bearing capacity of the coating/substrate composites was evaluated using scratch testing. The results show that the friction characteristics and material pick-up tendency of the coatings to a large extent is controlled by the surface topography of the as-deposited coatings which should be improved by a polishing post-treatment in order to obtain a smooth surface. Based on the results obtained in this study, three different coatings – CrC/C, TiC and dual-layer TiC/CrC/C – are recommended to be evaluated in wire drawing field tests. CrC/C and TiC are recommended due to their intrinsic low friction properties and material pick-up tendency in sliding contact with steel. The dual-layer is recommended in order to combine the good properties of the two coatings CrC/C (low shear strength) and TiC (high hardness).

  • 184.
    Nilsson, Rickard
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Svahn, F.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Relating contact conditions to abrasive wear2006In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 261, no 1, p. 74-78Article in journal (Refereed)
    Abstract [en]

    Damage caused by particles within rolling/sliding contacts can severely reduce the operational life of machinery such as roller bearings, gears and pumps. Abrasive wear of spherical roller thrust bearings has been studied using a stylus apparatus and scanning electron microscopy (SEM). Both a standard bearing and a bearing with rollers coated with metal mixed amorphous carbon (Me-C:H) were studied. The SEM measurements were performed systematically across the contact surfaces so that surfaces with gradually different contact situations could be examined. These measurements were compared to the measured wear depth of the components of the roller bearing. Also, the calculated contact conditions in terms of creep, contact size and surface separation have been related to the observed wear pattern at various locations. To attempt to understand the wear behaviour of the bearing with coated rollers, the coating as well as the material content of the surfaces were examined using both SEM and energy dispersive X-ray spectrometry (EDS). This revealed that the coating did not flake off but rather was scratched off. It is possible to link the abrasive wear behaviour to the contact conditions. It is crucial to understand this relationship when building a simulation model of abrasive wear.

  • 185.
    Nosko, Oleksii
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Quantification of ultrafine airborne particulate matter generated by the wear of car brake materials2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 374-375, p. 92-96Article in journal (Refereed)
    Abstract [en]

    The wear of car brakes is one of the main sources of airborne particulate matter in urban environments. Ultrafine wear particles are of special environmental interest since they can easily penetrate the human body through inhalation and cause various diseases. In the present study, the contribution of ultrafine particles to airborne particulate matter emitted from car brake materials was investigated under different friction conditions. Particles were generated using a pin-on-disc machine located in a sealed chamber and analysed in terms of number, volume and mass concentrations. It was found that temperature has a strong influence on the size distribution of the emitted particles. At temperatures below 200 °C, the ultrafine particles make no measurable contribution to the mass concentration of airborne particles with diameters smaller than 10 µm (PM10). However, at temperatures above 200 °C, the mass fraction of the ultrafine particles in PM10 reaches tens of percent. In general, this fraction increases with the temperature and decreases with the sliding duration. The mass contribution of ultrafine wear particles to PM10 is substantial, and it should not be neglected in environmental and tribological studies.

  • 186.
    Nyberg, Harald
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Alfredsson, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    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.
    The asymmetrical friction mechanism that puts the curl in the curling stone2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 301, no 1-2, p. 583-589Article in journal (Refereed)
    Abstract [en]

    Curling is an Olympic winter sport in which two teams slide stones across a sheet of ice towards a target area, some 28 m away from the release line. The sport has its name from the fact that the trajectory of a rotating stone becomes slightly curled, a fact used to reach open spots or take out opponent stones behind hindering “guarding” stones, etc. By slowly turning the stone clockwise when it is released, it will curl to the right, and vice versa. The resulting sideward deviation is typically slightly more than a metre. This intriguing tribological phenomenon has so far lacked a satisfactory explanation, although many attempts have been presented. In many of them, the curling motion has been attributed to an asymmetrical distribution of the friction force acting on the sliding stone, such that the friction on the rear of the stone (as seen in the direction of motion) is higher than that on the front. In a recent paper, we could show that no such redistribution of the friction, no matter how extreme, can explain the magnitude of the observed motion of a real curling stone. The present work presents an alternative asymmetrical mechanism that actually is strong enough to account for the observed motion. Further, in contrast to previous models, it satisfies other observed phenomena, including the independence of rotational speed of the stone and the strong dependence of the roughness of the stone. The model is backed up by experimental evidence and is based on the specific tribological conditions presented by the contact between a scratched curling stone and a pebbled ice sheet.

  • 187.
    Nyberg, Harald
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Alfredsson, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    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.
    The asymmetrical friction mechanism that puts the curl in the curling stone2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 301, no 1-2, p. 583-589Article in journal (Refereed)
    Abstract [en]

    Curling is an Olympic winter sport in which two teams slide stones across a sheet of ice towards a target area, some 28 m away from the release line. The sport has its name from the fact that the trajectory of a rotating stone becomes slightly curled, a fact used to reach open spots or take out opponent stones behind hindering “guarding” stones, etc. By slowly turning the stone clockwise when it is released, it will curl to the right, and vice versa. The resulting sideward deviation is typically slightly more than a metre. This intriguing tribological phenomenon has so far lacked a satisfactory explanation, although many attempts have been presented. In many of them, the curling motion has been attributed to an asymmetrical distribution of the friction force acting on the sliding stone, such that the friction on the rear of the stone (as seen in the direction of motion) is higher than that on the front. In a recent paper, we could show that no such redistribution of the friction, no matter how extreme, can explain the magnitude of the observed motion of a real curling stone. The present work presents an alternative asymmetrical mechanism that actually is strong enough to account for the observed motion. Further, in contrast to previous models, it satisfies other observed phenomena, including the independence of rotational speed of the stone and the strong dependence of the roughness of the stone. The model is backed up by experimental evidence and is based on the specific tribological conditions presented by the contact between a scratched curling stone and a pebbled ice sheet.

  • 188.
    Nyberg, Harald
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Sundberg, Jill
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Särhammar, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jansson, Ulf
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Extreme friction reductions during inital running-in of W-S-C-Ti low-friction coatings2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2 SI, p. 987-997Article in journal (Refereed)
    Abstract [en]

    The disulphides of tungsten and molybdenum are known for their low friction properties when used as solid lubricants. Due to their low hardness, their load bearing capacity when used as thin films is poor. When carbon is added to a WS2 coating, both of these shortcomings are improved, and a structure consisting of nanocrystals of WS2, and possibly tungsten carbide, in a matrix of amorphous carbon is formed. In this study, an attempt is made for further increasing the hardness of such coatings, by addition of Ti, a strong carbide former. A number of W–S–C(–Ti) coatings were deposited using magnetron co-sputtering, and characterised with regard to chemical composition, structure and tribological properties. It was seen that addition of Ti significantly increased the hardness of the coatings, while maintaining their excellent low friction properties in dry atmosphere. However, the coatings with Ti showed extremely high initial friction, a feature not seen for the coatings without Ti. The mechanisms behind this running-in behaviour were investigated by studying surfaces at early stages of wear. It was observed that tribofilms formed during sliding for the coatings containing Ti consisted mainly of TiO2, with platelets of WS2 appearing in the contact only after prolonged sliding. For the pure W–S–C coatings, WS2 was observed in the sliding interface almost instantly at the onset of sliding.

  • 189.
    Nyman, Pär
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mäki, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Olsson, Richard
    Haldex Traction Systems AB.
    Ganemi, Bager
    Statoil Lubricants R&D.
    Influence of surface topography on friction characteristics in wet clutch applications2006In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 261, no 1, p. 46-52Article in journal (Refereed)
    Abstract [en]

    In heavily loaded wet clutches, such as in limited slip differentials, sintered friction materials are sometimes used due to their resilience at high loads and high temperatures as well as their competitive cost in comparison to alternative friction materials. During the lifetime of the clutch, changes in the friction materials' topography occur. These changes will influence the friction characteristics of the clutch, and therefore affect the anti-shudder performance of the transmission system. This paper investigates the influence of, and classifies, changes in the topography of the sintered friction material. The topography is measured by utilizing vertical scanning interferometry. Different parameters are investigated in order to find relevant parameters correlating to the wear of the material. Results show that changes in the topography of the friction material do indeed influence the friction characteristics of the clutch and that it is possible to calculate relevant topography parameters that describe the amount of wear the material has been subjected to.

  • 190.
    Odelros, S.
    et al.
    Sandvik Coromant R&D, Sweden.
    Kaplan, B.
    Sandvik Coromant R&D, Sweden.
    Kritikos, M.
    Sandvik Coromant R&D, Sweden.
    Johansson, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Norgren, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Sandvik Coromant R&D, Sweden.
    Experimental and theoretical study of the microscopic crater wear mechanism in titanium machining2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 376, p. 115-124Article in journal (Refereed)
    Abstract [en]

    Continuous turning of Ti6AI4V with uncoated WC-Co cutting tool inserts mainly results in crater wear on the rake face of the tool. The crater is located close to the cutting edge and increases in size with increased time in cut. The flank wear remains minor until the point when the crater reaches a critical size so that the edge deforms plastically and edge breakage occurs. To understand the crater wear degradation mechanisms, this study focuses on examining the worn tool at different stages, using both experimental and theoretical techniques, as well as under static and dynamic conditions. A layer of adhered work-piece material is observed in the crater. The present study shows both experimental and theoretical evidence of carbon depletion of the WC in the crater and formation of W (bcc) at the interface during wet continuous longitudinal turning of Ti6AI4V. This has been demonstrated for the first time. In addition, indications of a carbon rich compound, possibly MC, where M=Ti, V and W, are also observed. These observations are verified by simulation of the diffusion process. Furthermore, diffusion simulations indicate that a liquid may form at the tool/chip interface in the crater zone during machining. Turning is a dynamic process, however, to study the chemical driving forces in this system under static conditions, a means of verification of which phases will form is needed. Therefore, a diffusion couple consisting of the same materials is prepared and analyzed. Similar results are obtained for the diffusion couple as for the worn tool, indicating that the chemical wear is an important degradation parameter. The diffusion couple results are also compared to a numerical simulation of the diffusion process.

  • 191.
    Olander, Petra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Eskildsen, Svend S.
    Fogh, Jesper W.
    Hollman, Patrik
    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.
    Testing scuffing resistance of materials for marine 2-stroke engines: Difficulties with lab scale testing of a complex phenomenon2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 340-341, no SI, p. 9-18Article in journal (Refereed)
    Abstract [en]

    Optimising sliding materials of marine two-stroke diesel engine cylinders for reduced risk of scuffing is imperative because of the high costs associated with replacing the cylinder liner. But how can a complex and poorly understood phenomenon such as scuffing be tested? This study investigates the potential of material selection based on lab tests. Experience from ship operation is combined with analysis of lab scale scuffing tests to evaluate the possibilities of gaining applicable knowledge from scuffing testing. Two piston ring materials, a grey cast iron and a plasma sprayed cermet coating, both currently used in engines, were tested. Each of the materials was tested with two surface characters, achieved by run-in in a real engine and by fine grinding respectively. The ranking of the two materials proved to differ between the two surface characters. In the tests, scuffing could only be detected when all oil had become removed from the contact by being adsorbed by agglomerated wear debris and scraped away. This and other critical mechanisms behind scuffing in the tests are thoroughly discussed and compared to possible mechanisms taking place in the engine.

  • 192.
    Olander, Petra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Heinrichs, Jannica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Initiation and propagation of tool wear in turning of titanium alloys - Evaluated in successive sliding wear test2019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 426-427, no Part B, p. 1658-1666Article in journal (Refereed)
    Abstract [en]

    Titanium alloys are known to cause significant crater wear on the rake face of cutting inserts when exposed to the fresh chip during cuffing, limiting the lifetime of the tool. Previous studies have shown that wear surfaces on inserts has a crater filled with transferred titanium. The WC grains in the bottom of the crater are depleted of carbon, resulting in a top surface rich in tungsten. To further investigate the initiation of wear in the present study a sliding test, previously developed to imitate the conditions on the rake face during cuffing, was used. The test was performed in interrupted mode, allowing intermediate SEM studies of the tool surface, while successively increasing the sliding distance. A cemented carbide grade, H13A, commonly used for cutting titanium alloys, and titanium alloy Ti6Al4V were used as model materials. The results from the sliding tests showed that both transfer of titanium and wear of the cemented carbide composite occur simultaneously. The wear is shallow and occurs on a very small scale, which adds up to a large crater, which is continuously filled with a smooth layer of titanium.

  • 193.
    Olander, Petra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    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.
    Piston ring and cylinder liner wear aggravation caused by transition to greener ship transports: Comparison of samples from test rig and field2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2 SI, p. 1345-1350Article in journal (Refereed)
    Abstract [en]

    New and upcoming emission regulations for ships will push towards greener sea based transports. Changing the fuel, from heavy fuel oil to natural gas, is a promising approach to fulfil these regulations, but tribological problems are expected to appear when the sulphur-free gas replaces the sulphur-rich heavy fuel oil. The aim of this study was to investigate the role of sulphur for the high performance of current tribosystem in the cylinder. Field worn samples were examined and no tribofilm containing sulphur was detected, but grain refinement and plastic deformation was found below the sliding surfaces. A reciprocating test rig was used in order to simulate the tribological conditions for the piston rings and cylinder liner. Tests were run with fresh cylinder oil as well as with used cylinder oil, where the latter was used in order to simulate the chemical environment in the cylinder of an engine. Tribofilms were formed on the surfaces during these tests, and the tribofilms formed on samples run with used cylinder oil contained more sulphur than tribofilms formed on samples run with fresh cylinder oil. So far, we have not been able to see any beneficial effects of higher sulphur content in the oil.

  • 194.
    Olander, Petra
    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.
    Scuffing resistance testing of piston ring materials for marine two-stroke diesel engines and mapping of the operating mechanisms2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 330, p. 42-48Article in journal (Refereed)
    Abstract [en]

    The incentive is strong for optimising sliding materials to reduce the risk for scuffing. In this study, scuffing tests were performed aiming towards finding new piston ring materials for greener marine diesel engines and also towards understanding scuffing mechanisms better. The tested ring materials where grey iron, Stellite 6, plasma sprayed cermet and high velocity oxy fuel (HVOF) cermet (both cermets with the same compounds: Cr-carbide, Ni, Cr, Mo). The Stellite 6 and HVOF cermet performed somewhat better than the other two materials. Microscopic and spectroscopic studies of failed sample surfaces revealed several characteristic features. It was clear that different mechanisms are active simultaneously, at different parts of the samples. Based on these results, we propose a hypothesis for a scuffing process involving several stages with distinctive mechanisms. Further studies are needed to strengthen this hypothesis and to relate these findings to actual deterioration mechanisms in the engine.

  • 195. Olofsson, J.
    et al.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Jacobson, S.
    Tribofilm formation of lightly loaded self mated alumina contacts2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 289, p. 39-45Article in journal (Refereed)
    Abstract [en]

    A tribofilm is formed on alumina surfaces that have been slid against alumina surfaces. The tribofilm is formed by alumina wear particles that have been ground, agglomerated and tribosintered to a film. The tribofilm smoothens out the surface topography and fills up cavities. Tribofilms on alumina surfaces have been investigated with respect to surface appearance, hardness and chemical composition. Surface preparation and surrounding humidity have shown to affect the character and lateral distribution of the tribofilm. The tribofilm that was formed in humid air was softer than the tribofilm formed in dry air. XPS analysis revealed the chemical shift of the Al 2p peak did not differ between the tribofilms that was formed in different humidity, nor the unworn reference surface, finding that no hydroxide was found on the alumina surfaces. Also, no tribochemical changes could be detected by ToF-SIMS analysis. (C) 2012 Elsevier B.V. All rights reserved.

  • 196.
    Olofsson, Johanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bexell, Ulf
    Dalarna University, Materialvetenskap, Borlänge.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tribofilm formation of lightly loaded self mated alumina contacts2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 289, p. 39-45Article in journal (Refereed)
    Abstract [en]

    A tribofilm is formed on alumina surfaces that have been slid against alumina surfaces. The tribofilm is formed by alumina wear particles that have been ground, agglomerated and tribosintered to a film. The tribofilm smoothens out the surface topography and fills up cavities. Tribofilms on alumina surfaces have been investigated with respect to surface appearance, hardness and chemical composition. Surface preparation and surrounding humidity have shown to affect the character and lateral distribution of the tribofilm. The tribofilm that was formed in humid air was softer than the tribofilm formed in dry air. XPS analysis revealed the chemical shift of the Al 2p peak did not differ between the tribofilms that was formed in different humidity, nor the unworn reference surface, finding that no hydroxide was found on the alumina surfaces. Also, no tribochemical changes could be detected by ToF-SIMS analysis.

  • 197.
    Olofsson, Johanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gerth, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    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.
    On the influence from micro topography of PVD coatings on friction behaviour, material transfer and tribofilm formation2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, no 9-10, p. 204-2057Article in journal (Refereed)
    Abstract [en]

    PVD coatings based on amorphous carbon with metal-carbides are currently gaining a high interest for use on machine elements due to their potential to give low friction and low wear of the counter surface. However, the performance varies significantly between the various types of such coatings and the causes of this are not clear. One factor is the micro topography of the coating surface. This topography may influence the friction in many ways; by changing the state of lubrication, by causing scratching of the counter surface, by modifying the topography of the counter surface the material transfer, the tribofilm formation, etc.

    TaC/a-C coatings, produced by co-sputtering of carbon and tantalum in an argon atmosphere, were deposited on high speed steel substrates exposed to varying degrees of etching to produce a range of surface roughnesses. Ball-on-disc experiments were used to evaluate the tribological properties of the coatings in dry condition against a ball bearing steel ball. The surfaces were analysed using various advanced techniques, including, SEM, XPS, Raman, EDS and AFM, all both prior to and after the testing.

    It was shown that the resulting surface topography of the coating is affected even by very small protrusions on the substrate. The coefficient of friction decreased during use to a stable level, due to a complex process including tribofilm build-up on the sliding ball. Surfaces with lower protrusions exhibited a faster friction decrease, i.e. a faster running in.

  • 198.
    Olofsson, Johanna
    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.
    The influence of grain size and surface treatment of the tribofilm formation on alumina components2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 292, p. 17-24Article in journal (Refereed)
  • 199.
    Olofsson, Johanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lindberg, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Johansson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. PiezoMotor AB.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On the role of tribofilm formation on the alumina drive components of an ultrasonic motor2009In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 267, no 5-8, p. 1295-1300Article in journal (Refereed)
    Abstract [en]

    Ultrasonic motors typically have a friction drive system to transfer the movement. The miniaturized motor type investigated here has a friction drive system consisting of two drive pads that transfer the high frequency oscillating movement of two piezoelectric elements to a linear drive rail. The pads and rail consist of alumina.

    Fiction tests were carried out to investigate how the coefficient of friction between the drive pads and the drive rail depends on the number of strokes of the rail. It was found to initially increase with the number of strokes and then stabilize.

    Scanning electron microscopy studies of the friction drive surfaces show how a tribofilm forms and develops with the number of strokes. Interestingly, the smooth tribofilm surface gives a higher coefficient of friction than the original rougher surface. To further investigate the nature of the tribofilm. cross section samples were produced with a focused ion beam instrument. The tribofilms show different characters and appear to form gradually by agglomeration and sintering of wear debris. Transmission electron microscopy showed the tribofilm to be amorphous and partly nano-crystal line. This high resolution investigation also clearly demonstrated that the tribofilm bonds very well to the underlying alumina grains.

    The processes of friction increase and tribofilm build-up stabilize early compared to the lifetime of the motor.

  • 200.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    A study of airborne wear particles generated from the train traffic-Block braking simulation in a pin-on-disc machine2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, no 1-2, p. 86-91Article in journal (Refereed)
    Abstract [en]

    Recently, much attention has been given to the influence of airborne particles in the atmosphere on human health. Sliding contacts are a significant source of airborne particles. In this study airborne particles from railway block brakes are studied using cast iron and composite block material on railway wheel steel. A pin-on-disc tribometer equipped with airborne particle counting instrumentation was used as experimental set-up. The result shows differences for the two tested block brake material combinations in particle size distribution, morphology and elemental content.

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