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  • 1.
    Andersson, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    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 study of the influence of gear surface roughness and immersion depth on gear efficiency and temperature2014In: Proceedings of the 16th Nordic Symposium on Tribology - NORDTRIB 2014, 2014, p. A 1-A 6Conference paper (Refereed)
  • 2.
    Andersson, Sören
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Björklund, Stefan
    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.
    Frictions models for sliding dry, boundary and mixed lubricated contacts2007In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, p. 580-587Article in journal (Refereed)
    Abstract [en]

    Friction, lubrication, and wear have a strong influence on the performance and behavior of mechanical systems. This paper deals with different friction models for sliding contacts running under different conditions. The models presented are suited to different situations, depending on the type of contact, running conditions, and the behavior of interest. The models will be discussed from simulation and tribological points of view. The different types of friction models considered are:

    center dot friction models for transient sliding under dry, boundary and mixed lubrication conditions,

    center dot friction models for micro-displacements of engineering surfaces subjected to transient sliding,

    center dot friction models often used in the simulation and control of technical systems,

    center dot combined friction models that represent physical behaviors fairly well but are also suitable for use in simulating systems,

    center dot friction models that take into account the stochastic nature of interacting surface asperities

  • 3.
    Andersson, Sören
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Söderberg, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Friction models for dry, boundary and mixed lubricated contacts2004Conference paper (Other academic)
  • 4.
    Bergseth, Ellen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Logarithmical Crowning for Spur Gears2010In: Strojniski vestnik, ISSN 0039-2480, Vol. 56, no 4, p. 239-244Article in journal (Refereed)
    Abstract [en]

    Gear tooth modifications, such as lead crowning, are often recommended to compensate for misalignment (e.g. assembly deviations). Lead crowning means that the tooth centre is slightly thicker than the tooth edges and is usually described as a circular arc profile. The use of crowning shifts the peak load from the tooth flank edges and, therefore, reduces the risk for high contact pressures at the edges, which can otherwise result in a shortened service life. In this study a logarithmical lead profile was compared with traditional lead profile modifications for gears. The profiles were applied on a spur gear pair and a numerical method for contact analysis was used to calculate the contact pressure distribution at the pitch diameter. All lead profiles were optimised with respect to low contact pressure at a specific normal load, a specified maximum misalignment in the plane of action and a tooth flank edge contact criteria. The results show that the logarithmical profile responds differently to misalignments compared to the traditional lead profile modifications. The logarithmical profile resulted in lower maximum contact pressures for small misalignments and is, therefore, of further interest in terms of achieving a robust gear design. (C) 2010 Journal of Mechanical Engineering. All rights reserved.

  • 5.
    Bergseth, Ellen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Sjöberg, Sören
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Influence of real surface topography on the contact area ratio in differently manufactured spur gears2012In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 56, p. 72-80Article in journal (Refereed)
    Abstract [en]

    Surface topography measurements from spur gears produced using four different manufacturing methods were used as input to a contact analysis programme. All test gears were case-hardened, two gears were machined in the hardened state using honing and grinding respectively, and two gears were machined in the non-hardened state using hobbing and hobbing followed by green-shaving respectively. The results show that the surface topography caused by the manufacturing methods has a large influence on the real contact area in the early life of the gear. The green-shaved gear surfaces and the honed gear surfaces have the highest contact area ratio after manufacturing (as-manufactured), which could be advantageous for future gear life with respect to e.g. the running-in process.

  • 6.
    Björklund, Stefan
    KTH, Superseded Departments, Machine Design.
    The influence of surface roughness in elliptical contacts2001In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 34, no 12, p. 841-845Article in journal (Refereed)
    Abstract [en]

    The influence of surface roughness on contact behaviour is of great importance in many tribological situations. In the last decade several methods to calculate the pressure distribution and the real contact area in contacts between rough surfaces have been described. A problem arising for slender elliptical contacts, such as between gear teeth, roller and raceway, cam and follower, etc., is that the size of the contact is much greater than the size of the asperities. Accordingly the number of contact nodes necessary for an accurate solution to the problem becomes excessively large. This paper describes a method to calculate the influence of three-dimensional surface roughness in contacts that are very long in one direction. The method is based on restricting the calculations to a subpart of the real contact area, while the rest of the contact is taken into account by mirroring techniques. The results show that the real contact area is very sensitive to the amplitude of the roughness, while the waviness is less important. An equation is suggested from which the real area can be calculated if the smooth case contact parameters and two roughness parameters are known.

  • 7.
    Häggström, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Scania CV AB, Sweden.
    Nyman, Pär
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Predicting friction in synchronizer systems2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 97, p. 89-96Article in journal (Refereed)
    Abstract [en]

    The coefficient of friction in synchronizers is important from both a performance and a functional point of view. The synchronization process is highly transient, and the parameters affecting the coefficient of friction have strong mutual dependences, making analysis highly complex. A new friction model for a lubricated molybdenum-steel contact has been developed based on integrating results from physical rig tests and FEM simulations. A simplified thermal model has also been developed, with the purpose to quickly assess the coefficient of friction based on transient force and synchronizer dimensions. The results show good correlation with measured data except at very low sliding speed.

  • 8.
    Häggström, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Evaluation of synchronizer loading parameters and their ability to predict failure2018In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 232, no 9, p. 1093-1104Article in journal (Refereed)
    Abstract [en]

    Molybdenum coated gearbox synchronizers are tested in a mu-comp test rig under varying loading conditions until failure. Four different parameters used to describe the thermomechanical load are evaluated just before failure to compare their ability to predict failure. The parameters evaluated are the synchronized kinetic energy, the synchronization power, and the focal as well as the average surface temperature increase. The focal surface temperature increase as well as the average surface temperature increase is found to predict failure with relatively good accuracy. It is shown that there exists a threshold which divides the synchronizer into either a very long or a very short service life. Additionally, a method to determine the average surface temperature in the gearbox management system is proposed.

  • 9.
    Häggström, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Optimization of synchronizer cone angle with regards tomanufacturing tolerances of cone roundness and cone angleManuscript (preprint) (Other academic)
    Abstract [en]

    The effects from manufacturing tolerances on the maximum focal temperature has been investigated by transient thermomechanical simulations. Both relative cone angle and cone out-of-roundness for molybdenum and carbon fiber reinforced polymer (CFRP) synchronizers were evaluated. It was shown that cone out-of-roundness significantly increase the focal contact temperature for that specific cone, but has little impact on the opposing cone. Two populations of measured synchronizers were evaluated, and it was shown that the maximum focal surface temperature can be decreased in almost all tolerance cases by introducing a relative angle between the cones.

  • 10.
    Häggström, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Scania CV AB, Sweden.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Björklund, Stefan
    Robust pre-synchronization in heavy truck transmissions2014In: International Gear Conference 2014: 26th–28th August 2014, Lyon, Woodhead Publishing Limited, 2014, p. 914-923Conference paper (Refereed)
    Abstract [en]

    Transmission performance directly influences vehicle behaviour, energy efficiency, and perceived quality. A modern transmission is an aggregate of interacting sub-systems, e. g. gears, bearings, synchronisers and other shifting elements. New transmission trends ask for increased shift performance with higher loads for the synchronising components. Synchroniser development has traditionally required exhaustive physical testing and few analytical methods exist. A numerical method for assessing pre-synchronisation performance, using a multi-physics FEM software, is presented. Simulations show that grooves in the synchroniser surface have a positive effect on pre-synchronisation, and that the presence of grooves seems to be more important than the groove design.

  • 11.
    Häggström, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    The effect of manufacturing tolerances on the thermomechanical load of gearbox synchronizers2018Conference paper (Refereed)
    Abstract [en]

    Transmission performance is crucial for heavy trucks and connected vehicles in general and for platooning of trucks in particular. Gearbox synchronizers are highly loaded conical friction brakes used during gear shifts. Service life and, thus, the gear shifting reliability, of the synchronizer depend on the local thermomechanical loading of the contact surface. To achieve a robust and cost-efficient system, more knowledge is needed of how manufacturing tolerances affect the local thermomechanical loading and therefore service life and reliability of a synchronizer. The effects from angle deviations between the mating cones and cone out-of-roundness on focal maximum temperature during a synchronization sequence have been studied with transient thermomechanical simulations. It is shown that thermomechanical effects will significantly magnify the nominal effects on synchronization performance caused by shape deviations given by the specified manufacturing tolerances.

  • 12.
    Häggström, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Thermomechanical performance of CFRP synchronizer friction linersManuscript (preprint) (Other academic)
    Abstract [en]

    To improve the ability of a thermomechanical simulation model for CFRP lined synchronizers to predict synchronization performance and reliability, temperature dependent material data for the specific CFRP lining is needed. The compressive modulus, coefficient of thermal expansion, specific heat and thermal conductivity are determined experimentally. The effect of each material property on the focal surface temperature is analyzed, and it is shown that the compressive modulus has the largest influence for all analyzed load cases. Physical tests show that surface hot spots begin to appear at a simulated focal surface temperature of 200 °C, while performance degradation occurs at a simulated focal surface temperature of 230 °C-250 °C.

  • 13.
    Häggström, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Scania CV AB, Sweden.
    Stenström, Wiktor
    FS Dynamics, Stockholm, Sweden.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    A Verified and Validated Model for Simulation-Driven Design of Heavy Duty Truck Synchronizers2015In: ASME Proceedings | ASME 2015 Power Transmission and Gearing Conference, ASME Press, 2015, Vol. 10, article id V010T11A045Conference paper (Refereed)
    Abstract [en]

    The strong market trend toward lower fuel consumption for heavy road transports requires more frequent gear shifting and increased gear shift performance, i.e. shorter shift time. Increased shift performance means higher loads for the synchronizer which brings component and shifting process optimization more into focus.

    Traditionally, synchronizer development has relied on physical testing of complete synchronizers in general gearbox test rigs or in specialized synchronization test rigs leaving much of the causes of the observed effects unclear. This paper presents a generalized FE-based thermomechanical simulation model to be used for model-based synchronizer analysis and design. The model is targeted for studies of how different external loads and the values of different synchronizer design parameters affect the temperature transient in the friction lining. Recommendations of how major modeling complications should be treated are presented. The developed simulation model is verified and validated with a combination of analytical means and transient temperature measurements of bulk and surface temperatures. The applicability of the presented model, as well as its limitations, are discussed and exemplified with different design cases.

  • 14.
    Häggström, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Scania CV AB, Sweden.
    Stenström, Wiktor
    FS Dynamics, Stockholm, Sweden.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Parameter study of the thermomechanical performance of heavy duty synchronizers2015In: 15th International VDI Congress, 2015Conference paper (Refereed)
  • 15.
    Iwnicki, Simon
    et al.
    Manchester Metropolitan University.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Enblom, Roger
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Railway Technology.
    Wheel-rail contact mechanics2009In: Wheel-rail interface handbook / [ed] Roger Lewis, Ulf Olofsson, Cambridge, UK: Woodhead Publishing Ltd , 2009, p. 58-92Chapter in book (Refereed)
  • 16.
    Lindholm, Per
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Calvo Cortes, Miguel
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Characterization of wear on a cam follower system in a diesel engine2003In: Wear 254, p. 1199-1207Article in journal (Refereed)
    Abstract [en]

    This paper presents an investigation of the running in of the most important contact surfaces of a modern diesel cam follower system. The test equipment used consists of a commercially available cylinder head with an overhead camshaft and valve train system for six cylinders. The load on the contacting surfaces is varied by controlling the fuel injector pumps. The running in is investigated by analysing the changes in topography of the roller, pin and rocker arm of the fuel injector arm. Seven test series were conducted for 1, 10 and 100 h with a variation of the load and speed between a high and low level. The test time was not long enough to be able to see any changes in the surface topography of the roller or pin surfaces. However the wear on the roller bearing surface and the rocker arm bearing surface was significant. Here the surface peak heights are worn off and the surfaces are smoothed out. The observed changes in surface topography are related to the current lubrication regime and the wear is discussed in terms of the λ -value.

  • 17.
    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.).
    Sundvall, C.
    Test equipment for a cam follower system in a diesel engine2001Conference paper (Other academic)
  • 18.
    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.

  • 19.
    Lindholm, Per
    et al.
    KTH, Superseded Departments, Machine Design.
    Spiegelberg, Christer
    KTH, Superseded Departments, Machine Design.
    Andersson, Sören
    Björklund, Stefan
    KTH, Superseded Departments, Machine Design.
    Contact conditions in a cam and roller contact2001In: Proceedings of World Tribology Congress WT2001, Wien: Österreichische Tribologishe Gesellshaft , 2001Conference paper (Other academic)
  • 20.
    Lundberg, Oskar
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Pärssinen, M.
    Lopez Arteaga, Ines
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    A nonlinear state-dependent model for vibrations excited by roughness in rolling contacts2015In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 345, no 9, p. 197-213Article in journal (Refereed)
    Abstract [en]

    A state-dependent method to model contact nonlinearities in rolling contacts is proposed. By pre-calculation of contact stiffness and contact filters as functions of vertical relative displacement, a computationally efficient modelling approach based on a moving point force description is developed. Simulations using the state-dependent model have been analysed by comparison with measurements. Results from the investigated case consisting of a steel ball rolling over a steel beam having two different degrees of roughness - show good agreement between nonlinear simulations and measured beam vibrations. The promising results obtained with the proposed method are potentially applicable to wheel rail interaction and rolling element bearings.

  • 21.
    Lundberg, Oskar
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Lopez Arteaga, Ines
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Non-linear contact forces for beam/ball-interaction and its influence on the dynamic response of the beam2013In: 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life, OAL-Osterreichischer Arbeitsring fur Larmbekampfung , 2013, p. 238-247Conference paper (Refereed)
    Abstract [en]

    A well-defined rolling contact problem is studied with the intention to cover interesting aspects of tyre-road contact modeling and rolling contact in general. More specifically, the dynamic response in a steel beam caused by a steel ball rolling over it is studied by theoretical modeling of the beam- And ball dynamics as well as the contact forces. Validation of the dynamic response simulations is achieved by comparison with measurements. The contact model is shown to be greatly dependent on an accurate estimate of the real contact stiffness. A method to estimate the contact stiffness which leads to good accuracy in dynamic response simulations is presented. Although the contact stiffness is significantly lower for rubber- Asphalt interaction than for steel-steel contact, the results give useful insight for tyre-road contact modeling.

  • 22.
    Lundberg, Oskar
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Lopez Arteaga, Ines
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Non-linear contact stiffness and dynamic contact filter for rolling contacts2014In: FISITA 2014 World Automotive Congress - Proceedings, FISITA , 2014Conference paper (Refereed)
    Abstract [en]

    Rolling contacts present in passenger cars such as in bearings and transmission elements are sources of noise and vibration, principally for interior comfort concerns. Moreover, tyre/road noise is the main source of road traffic noise which in turn leads to sleep disturbance and annoyance. In order to simulate friction losses as well as generated noise and vibrations in any rolling contact, it is crucial to have a correct description of the dynamic excitation caused by the roughness of the surfaces in contact. In this paper, a state-dependent modelling approach previously proposed by the authors is applied to a well-defined steel-steel rolling contact. A parametric study investigating the influence of rolling speed on contact conditions is performed, indicating the limits for the use of linear point force expressions for the rolling contact investigated. The state-dependent method is based on pre-calculation of contact stiffness and contact filtering as functions of vertical relative displacement. This leads to a computationally efficient way to include the influence of surface roughness and shape of the contacting bodies in a point force expression. Only vertical contact forces are studied within the scope of this work. Tangential friction forces are likely to affect the resulting vibrations and should therefore be further studied. 

  • 23.
    Lyu, Yezhe
    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.).
    Bergseth, Ellen
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Nilsson, R.
    Lindgren, A.
    Höjer, M.
    Development of a noise related track maintenance tool2015In: 22nd International Congress on Sound and Vibration, ICSV 2015, International Institute of Acoustics and Vibrations , 2015Conference paper (Refereed)
    Abstract [en]

    The purpose of this work-package within the Quiet-track, FP7, is to develop a noise related track maintenance tool, in the form of an on-board measurement system. As a first step, lab scale tests using a pin-on-disc tribometer were used in order to distinguish how noise changes when the wear mechanism in a sliding contact shifts from normal wear to severe and catastrophic wear. Once the potential for using sound as an indication of severe wear transitions was established, full scale tests were carried out with a rapid transit (metro) train, type C20. The train was equipped with microphones that continuously measured the sound pressure near the wheel rail contact. In order to provoke severe/catastrophic wear, the test train was run in a curve with small radius, and the rails and wheels were carefully cleaned before the tests. The same kind of transfer from mild to severe/catastrophic wear was identified on the full scale test as in the laboratory scale test, confirmed by studying the surface topography and the morphology of the wear particles. Moreover, the full scale test results showed that the sound pressure changed significantly when transferring from mild to severe wear in agreement with the pin-on-disc test results. By comparing noise from the inner wheel/rail contact to noise form the outer wheel/rail contact a wear indication value for the outer wheel/rail contact is suggested in this study. This value can be seen as an advanced parameter from which the probability of severe wear, in the wheel flange/rail gauge face contact of the outer contact, can be estimated. At present, a real time condition monitoring system is set up in Stockholm (Metro line 1) in order to validate the results.

  • 24. Marshall, M. B.
    et al.
    Lewis, R.
    Dwyer-Joyce, R. S.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Experimental characterization of wheel-rail contact patch evolution2006In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 128, no 3, p. 493-504Article in journal (Refereed)
    Abstract [en]

    The contact area and pressure distribution in a wheel/rail contact is essential information required in any fatigue or wear calculations to determine design life, re-grinding, and maintenance schedules. As wheel or rail wear or surface damage takes place the contact patch size and shape will change. This leads to a redistribution of the contact stresses. The aim of this work was to use ultrasound to nondestructively quantify the stress distribution in new, worn, and damaged wheel-rail contacts. The response of a wheel/rail interface to an ultrasonic wave can be modeled as a spring. If the contact pressure is high the interface is very stiff, with few air gaps, and allows the transmission of an ultrasonic sound wave. If the pressure is low, interfacial stiffness is lower and almost all the ultrasound is reflected. A quasistatic spring model was used to determine maps of contact stiffness from wheel/rail ultrasonic reflection data. Pressure was then determined using a parallel calibration experiment. Three different contacts were investigated; those resulting from unused, worn, and sand damaged wheel and rail specimens. Measured contact pressure distributions are compared to those determined using elastic analytical and numerical elastic-plastic solutions. Unused as-machined contact surfaces had similar contact areas to predicted elastic Hertzian solutions. However, within the contact patch, the numerical models better reproduced the stress distribution, as they incorporated real surface roughness effects. The worn surfaces were smoother and more conformal, resulting in a larger contact patch and lower contact stress. Sand damaged surfaces were extremely rough and resulted in highly fragmented contact regions and high local contact stress.

  • 25. Marshall, M. B.
    et al.
    Lewis, R.
    Dwyer-Joyce, R. S.
    Olofsson, Ulf
    KTH, Superseded Departments, Machine Design.
    Björklund, Stefan
    KTH, Superseded Departments, Machine Design.
    Ultrasonic characterisation of a wheel/rail contact2004In: Transient Processes in Tribology, 2004, Vol. 43, p. 151-158Conference paper (Refereed)
    Abstract [en]

    A quantification of stress in a wheel/rail contact is essential information required in fatigue and wear calculations for determining design life, regrinding and maintenance schedules. The aim of this work was to use ultrasound to non-destructively determine wheel/rail contact pressures. A wheel/rail interface behaves like a spring. If the pressure is high there are few air gaps; so it is very stiff and allows transmission of an ultrasonic wave. If the pressure is low then interface stiffness is lower and most ultrasound is reflected. A spring model was used to determine maps of contact stiffness from wheel/rail contact ultrasonic reflection data. A calibration procedure was then used to determine the pressure. Measured contact pressure contours are compared with those predicted by various contact theories.

  • 26.
    Olofsson, Ulf
    et al.
    KTH, Superseded Departments, Machine Design.
    Andersson, S.
    Björklund, Stefan
    KTH, Superseded Departments, Machine Design.
    Simulation of mild wear in boundary lubricated spherical roller thrust bearings2000In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 241, no 2, p. 180-185Article in journal (Refereed)
    Abstract [en]

    Owing to the curved contact surfaces in a spherical roller thrust beating, the rollers will undergo sliding. For an unskewed roller there will be two points along each contact where the sliding velocity is zero. At all other points along the contact, sliding is present. Under boundary lubricated conditions the sliding can give rise to mild wear. Experimental results show that this wear can cause a significant change in the surface profile outside the zero sliding points. The mild wear in the contact was simulated using Archard's wear law. An iterative wear model is described in which the normal load distribution, the tangential tractions and the sliding distances are repeatedly calculated to simulate the changes in surface geometry due to wear. Good qualitative agreement was achieved between the simulation results and the previously presented experimental results.

  • 27.
    Pärssinen, Mikael
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Dynamic response caused by rolling contact of rough surfacesArticle in journal (Other academic)
    Abstract [en]

    A new general linear contact-interaction model is derived for treating the dynamic excitation that is due to the rolling contact of rough surfaces. It is shown that the relative-displacement and blocked-force models are special cases of this model. A numerical contact-computation program is utilised to compute the parameters of the contact-interaction model. This program accounts for the detailed surface geometry within the contact region. Furthermore, since contact between rough surfaces is accompanied by locally high stresses, an approximate method for treating plasticity is integrated in to the contact-computation program. The non-stationary response of the contacting bodies is accounted for by a state-space formulation, utilising a modal representation of the dynamic response of the two structures, respectively. As a consequence, the parameters of the contact-interaction model have to be time-dependent. This is dealt with by employing a Monte-Carlo procedure that generates representative time-dependent parameters.

  • 28. Sellgren, U.
    et al.
    Björklund, Stefan
    KTH, Superseded Departments, Machine Design.
    Andersson, S.
    A finite element-based model of normal contact between rough surfaces2003In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 254, no 11, p. 1180-1188Article in journal (Refereed)
    Abstract [en]

    Engineering surfaces can be characterized as more or less randomly rough. Contact between engineering surfaces is thus discontinuous and the real area of contact is a small fraction of the nominal contact area. The stiffness of a rough surface layer thus influences the contact state as well as the behavior of the surrounding system. A contact model that takes the properties of engineering surfaces into account has been developed and implemented using finite element software. The results obtained with the model have been verified by comparison with results from an independent numerical method. The results show that the height distribution of the topography has a significant influence on the contact stiffness but that the curvature of the roughness is of minor importance. The contact model that was developed for determining the apparent contact area and the distribution of the mean contact pressure could thus be based on a limited set of height parameters that describe the surface topography. By operating on the calculated apparent pressure distribution with a transformation function that is based on both height and curvature parameters, the real contact area can be estimated when the apparent contact state is known. The model presented is also valid for cases with local plastic flow in the bulk material.

  • 29.
    Sellgren, Ulf
    et al.
    KTH, Superseded Departments, Machine Design.
    Björklund, Stefan
    KTH, Superseded Departments, Machine Design.
    Andersson, Sören
    KTH, Superseded Departments, Machine Design.
    A Contact Model for Rough Surfaces1999In: NAFEMS World Congress, April 25-28 1999, Newport, Rhode Island,USA, 1999Conference paper (Other academic)
    Abstract [en]

    Engineering surfaces can be characterized as more or less randomly rough. Contact between engineering surfaces is thus discontinuous and the real area of contact is a small fraction of the nominal contact area. The stiffness of a rough surface layer will thus have an influence on the contact state as well as on the behavior of the surrounding system. A contact model that takes the properties of engineering surfaces into account has been developed and implemented in a commercial FE software. Results obtained with the model have been compared and verified with results from an independent numerical method. Results have shown that the height distribution of the topography has a significant influence on the contact stiffness but that the curvature of the roughness is of minor importance. The contact model that was developed for determining the apparent contact area and the distribution of the mean contact pressure could thus be based on a limited set of height parameters that describe the surface topography. By operating on the calculated apparent pressure distribution with a transformation function that is based on both height and curvature parameters, the real contact area can be estimated in a post processing step.

     

  • 30.
    Sjöberg, Sören
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Bergseth, Ellen
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Influence of real surface topography on the contact area ratio in differently manufactured spur gears2008In: Proceedings of Tribology 2008: Surface Engineering of Automotive Powertrains for Environmentally Friendly Transport, 2008Conference paper (Refereed)
  • 31.
    Sjöberg, Sören
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Björklund, Stefan
    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.
    The influence of manufacturing method on the running-in of gears2011In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 225, no 10, p. 999-1012Article in journal (Refereed)
    Abstract [en]

    Striving for higher gear transmission efficiency by using a low-viscosity transmission lubricant affects the lubricant film thickness. To keep the K-ratio (the ratio between the film thickness and the surface roughness) intact, more effort must be put on the surface topography. This paper presents a study of how running-in affects the dry elastic contact area ratio in spur gears using real surface topographies from three common manufacturing methods (green-shaving, honing, and grinding). The test gears were manufactured in case-hardened steel, similar to 20MnCrS5. Surface topography measurements were used as input to a contact analysis boundary element software program. An important hypothesis used in this work is that the dry elastic contact area ratio, i.e. the ratio between real and nominal contact area, can be used as a measure of the contact conditions in gears. It is concluded that running-in differs significantly for the studied manufacturing methods and that the dry elastic contact area ratio gives a consistent description of these changes. The shaved gears have the highest dry elastic contact area ratio after running in, where the ground gears have the lowest dry elastic contact area ratio. The increase in dry elastic contact area ratio is about 30 per cent for the shaved gears, 12 per cent for the honed gears and less than 5 per cent for the ground gears. Extreme value parameters, such as R(p) and R(z), showed relatively good correlation to dry elastic contact area ratio. However no genuine correlation could be found between dry elastic contact area ratio and two-dimensional (2D) surface roughness parameters. Furthermore, traditional gear metrology form parameters do not serve as a good measure on the changes occurring during the running-in.

  • 32.
    Sosa, Mario
    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.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Gear Web Design with focus on Powder Metal - Sound characteristics and web design: Sound characteristics  and web design2013In: International Conference on Gears: Europe invites the world : time and venue: October 7th to 9th, 2013, Technical University of Munich (TUM), Garching (near Munich), Germany, VDI Verlag , 2013, Vol. 2, p. 1199-1208Conference paper (Refereed)
    Abstract [en]

    The presented work focuses on gear web design using powder metal (PM) by utilizing the finite element method (FEM) to reduce weight and inertia taking into account root bending strength and tooth deflection.A topological optimization is used to determine feasible candidates for different web designs which have as objective to reduce volume. Similar geometric topologies were shown during different loading conditions; and hence, this topology was chosen as a suitable candidate. This candidate was further developed into a parametric model which incorporated the same overall shape shown in the topological optimization. A shape optimization procedure was used utilizing the parametric model having as state variables root bending strength and tooth deflection; and as objective the decrease in inertia, and in consequence weight, of the gear. To analyze a gear which is thoroughly studied, a similar gear to the FZG C type gear is used.Another aspect studied in this paper is the damping properties of three different gears, wrought, conventional PM and double density. Their damping properties are measured using their reverberation time and their frequency response function.Sound characteristics results show that a significant increase in dampening can be observed in PM gears when compared to conventional wrought gears. Finally results from the shape optimizations show how gears can be designed with PM to reduce weight and inertia, with marginal effects on strength and stiffness.

  • 33.
    Sosa, Mario
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    In situ surface characterization of running-in of involute gears2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 340-341, p. 41-46Article in journal (Refereed)
    Abstract [en]

    Gear life and operation are largely determined by the properties of the contacting surfaces, which inevitably change over the gear life. The initial topography transformation, a characteristic effect of running-in, is very important. This paper focuses on how the running-in of the surface topography can be characterized and what methodology can be used for this purpose. To characterize running-in, gears were run in an FZG back-to-back test rig and the changes in surface topography were measured in situ using a Form Talysurf Intra. This enables the same gear tooth surface to be measured with enough precision to follow its development through the different stages of running-in. Gear tooth surfaces as manufactured were measured on three occasions: in initial manufactured condition, after a standard running-in procedure, and after an efficiency test. Running-in was characterized both qualitatively by plotting roughness profiles and quantitatively by analyzing a selected set of roughness parameters. This paper demonstrates that: the asperity peaks were worn off in the initial running-in stage; roughness, waviness, and form can be separated using a carefully chosen polynomial fit and the Gaussian filter; surface topography can be examined initially, after running-in, and after operation in situ; and complete wear of the initial surface can be observed in specific circumstances.

  • 34.
    Sosa, Mario
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). System- O Komponentdesign.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). System- O Komponentdesign.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). System- O Komponentdesign.
    In situ running-in analysis of ground gears2016In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 352-353, p. 122-129Article in journal (Refereed)
    Abstract [en]

    The initial contact state between two interacting gears proves of interest due to empirical evidence indicating difference in life and efficiency in the long term due to the initial operation. Presented here is an analysis of the initial contact state of spur gears, made of case carburized 16MnCr5 steel, by the use of in situ surface measurements and friction measurements in a back-to-back test rig during the running-in cycles. Furthermore a method to estimate wear during running-in is proposed. Results show that the most significant changes in roughness and friction occurred during the first initial cycles at high load.

  • 35.
    Sosa, Mario
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    In situ running-inanalysis of ground gearManuscript (preprint) (Other academic)
  • 36.
    Spiegelberg, Christer
    et al.
    KTH, Superseded Departments, Machine Design.
    Björklund, Stefan
    KTH, Superseded Departments, Machine Design.
    Andersson, Sören
    KTH, Superseded Departments, Machine Design.
    Simulation of transient friction of a cylinder between two planes2003In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 254, no 11, p. 1170-1179Article in journal (Refereed)
    Abstract [en]

    The need for good friction models for transient motions has increased as a consequence of the increased use of mechatronics and control engineering principles in precision mechanics. The machine elements in such equipment often involve rolling and sliding contacts. Most studies of friction in rolling and sliding contacts running under dry or boundary lubricated conditions have examined steady-state conditions. This paper describes simulations of the motion of a cylinder between two planes, first with a step change in velocity and then with an oscillating motion of the upper plane. The motion of the cylinder is determined by the friction in the contacts and the inertia. The friction in the rolling and sliding contacts is simulated with a brush model. The surfaces are assumed to be ideally smooth. For the step change in velocity, there is initially a period of complete sliding in the upper contact. During the sliding period, the friction force is the maximum possible, but it decreases as the complete sliding ends. The simulations show heavily damped oscillations, with frequencies corresponding to the natural translatory and torsional frequencies of the system. For the oscillating motions the sliding increases with the frequency of the motion, as expected.

  • 37.
    Spiegelberg, Christer
    et al.
    KTH, Superseded Departments, Machine Design.
    Lindholm, Per
    KTH, Superseded Departments, Machine Design.
    Björklund, Stefan
    KTH, Superseded Departments, Machine Design.
    Friction in spur gears and cam mechanisms using a brush model2001In: Proceedings of OST-01, 2001, p. 195-205Conference paper (Refereed)
  • 38.
    Söderberg, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Validation of a simple contact model and its applicability on rough surfaces2006In: Proceedings of 12th Nordic Symposium on Tribology NORDTRIB 2006, 2006Conference paper (Refereed)
  • 39.
    Söderberg, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Validation of a simplified numerical contact model2008In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, no 9-10, p. 926-933Article in journal (Refereed)
    Abstract [en]

    Surface roughness tends to have a significant effect on how loads are transmitted at the contact interface between solid bodies. Most numerical contact models for analyzing rough surface contacts are computational demanding and more computationally efficient contact models are required. Depending on the purpose of the simulation, simplified and less accurate models can be preferable to more accurate, but also more complex, models. This paper discusses a simplified contact model called the elastic foundation model and its applicability to rough surfaces. The advantage of the model is that it is fast to evaluate, but its disadvantage is that it only gives an approximate solution to the contact problem. It is studied how surface roughness influences the errors in the elastic foundation solution in terms of predicted pressure distribution, real contact area, and normal and tangential contact stiffness. The results can be used to estimate the extent of error in the elastic foundation model, depending on the degree of surface roughness. The conclusion is that the elastic foundation model is not accurate enough to give a correct prediction of the actual contact stresses and contact areas, but it might be good enough for simulations where contact stiffness are of interest.

  • 40. Xiao, L.
    et al.
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Rosen, B. G.
    The influence of surface roughness and the contact pressure distribution on friction in rolling/sliding contacts2007In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, no 4, p. 694-698Article in journal (Refereed)
    Abstract [en]

    A numerical contact model is used to study the influence of surface roughness and the pressure distribution on the frictional behaviour in rolling/sliding contacts. Double-crowned roller surfaces are measured and used as input for the contact analysis. The contact pressure distribution is calculated for dry static contacts and the results are compared with friction measurements in a lubricated rolling/sliding contact made with a rough friction test rig. The mean pressure is suggested as a parameter that can be used to predict the influence of surface roughness on the friction coefficient in such contacts. The results show two important properties of the friction coefficient for the friction regime studied in this paper: (1) there is a linear decrease in friction coefficient as a function of the slide-to-roll ratio, and (2) the friction coefficient increases linearly with increasing mean contact pressure up to a maximum limit above which the friction coefficient is constant. The absolute deviation of experimental results front the derived theory is for most cases within 0.005.

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