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  • 1.
    Abbasi, Saeed
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Zhu, Yi
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Pin-on-disc study of the effects of railway friction modifiers on airborne wear particles from wheel-rail contact2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 60, p. 136-139Article in journal (Refereed)
    Abstract [en]

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

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  • 2. Almqvist, Andreas
    et al.
    Sahlin, Fredrik
    Larsson, Roland
    Glavatskikh, Sergei
    Luleå University of Technology, Division of Machine Elements.
    On the dry elasto-plastic contact of nominally flat surfaces2007In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, no 4, p. 574-579Article in journal (Refereed)
    Abstract [en]

    A model to be used for numerical simulation of the contact of linear elastic perfectly plastic rough surfaces was developed. Energy dissipation due to plastic deformation is taken into account. Spectral theory and an FFT-techique are used to facilitate the numerical solution process. Results of simulations using four two-dimensional profiles with different topographies in contact with a rigid plane for a number loads are reported. From the results it is clear that the real area of contact (Ar) changes almost linearly with load and is only slightly affected by the difference in topography. A plasticity index is defined as the ratio of plastically deformed area (Ap) and Ar. Plastic deformation occurs even at low loads and there is a significant difference in plasticity index between the surface profiles considered. An investigation on how the spectral content of the surface profile influences the results presented is also performed. This is to ensure that the metrological limitations of the optical profilerused to measure the surfaces do not have a significant influence. It is concluded that the highest frequencies of the measured profile have a negligible influence on the real area of contact.

  • 3.
    Andersson, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    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.).
    The effect of running-in on the efficiency of superfinished gears2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 93, p. 71-77Article in journal (Refereed)
    Abstract [en]

    Reduced gear contact losses are necessary to keep operating temperatures, as well as fuel consumption low. In this work, an FZG gear test rig was used to investigate the effect of running-in on superfinished gears with respect to efficiency. This was compared to ground gears where a higher contact pressure yielded higher efficiency. No difference was found between the two running-in procedures when analysing superfinished gears. The effect of running-in on gears decreased when the initial surface roughness was reduced, which initially had an Ra, Rz and Rpk value of 0.08, 0.75 and 0.08 μm respectively. Superfinished gears showed an overall higher efficiency; however, a distinctly lower efficiency was present below 2 m/s when compared to ground gears.

  • 4.
    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

  • 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.
    Bergstedt, Edwin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Lin, Jiachun
    Beijing Univ Technol, Dept Instrument Sci & Technol, Fac Mat & Mfg, Beijing, Peoples R China..
    Andersson, Michael
    Hoganas AB, R&D, SE-26383 Hoganas, Sweden..
    Bergseth, Ellen
    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.).
    Gear micropitting initiation of ground and superfinished gears: Wrought versus pressed and sintered steel2021In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 160, article id 107062Article in journal (Refereed)
    Abstract [en]

    This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with CPT gears. The materials are wrought steel (16MnCr5) and a commercial powder metallurgical material (AstaloyTM Mo). Two finishing methods were studied: grinding and superfinishing. Experimental results show that the superfinishing prevented micropitting, but led to premature failure due to cracks in the root caused by tip-to-root interference. Micropitting was initiated at a higher load stage for the powder metallurgical steel compared to the ground wrought steel. The failure mechanisms were similar between materials with the same surface finish. The powder metallurgical steel showed subsurface initiated fatigue compared to the wrought ground steel having surface-initiated fatigue. Testing new finishing methods and materials, one has to be aware of the influence of the gear micro geometry.

  • 7.
    Bergstedt, Edwin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Lin, Jiachun
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Michael
    Höganäs AB.
    Bergseth, Ellen
    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.).
    Gear Micropitting Initiation of Ground and Superfinished Gears: Wrought versus Pressed and Sintered SteelIn: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464Article in journal (Refereed)
    Abstract [en]

    This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with C-PT gears. The materials are wrought steel (16MnCr5) and a commercialpowder metallurgical material (AstaloyTM Mo). Two finishing methods were studied: grinding andsuperfinishing. Experimental results show that the superfinishing prevented micropitting, but ledto premature failure due to cracks in the root caused by tip-to-root interference. Micropitting wasinitiated at load stage 8, and 9 for the ground wrought, and powder metallurgical steel respectively.The failure mechanisms were similar between materials with the same surface finish. The powdermetallurgical steel showed subsurface initiated fatigue compared to the wrought groundsteel having surface-initiated fatigue. Testing new finishing methods and materials, onehas to be aware of the influence of the gear micro geometry.

  • 8.
    Björklund, Stefan
    KTH, Superseded Departments (pre-2005), 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.

  • 9. Boschkova, K.
    et al.
    Kronberg, B.
    Rutland, Mark W
    KTH, Superseded Departments (pre-2005), Chemistry.
    Imae, T.
    Study of thin surfactant films under shear using the tribological surface force apparatus2001In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 34, no 12, p. 815-822Article in journal (Refereed)
    Abstract [en]

    Static and dynamic behaviour of thin surfactant films in aqueous solution of hexadecyltrimethylammonium salicylate (C16TASal) were investigated using the tribological surface force apparatus. Normal force measurements show that 0.15 mM C16TASal builds up an innermost film of approximately 8-11 Angstrom thickness at each mica surface, indicating that the surfactant adsorbs in a flat conformation. Furthermore, the height of the force barrier at approximately 60 Angstrom is low (ca 2 mN/m) indicating that the second adsorbed layer is easily pushed out. Addition of salicylate salt to 0.15 mM C16TASal give rise to a more close packed structure, with a total thickness of 62-65 Angstrom. indicative of a micellar or bilayer arrangement at the surfaces. Furthermore, the frequency dependence of the shear modulus was investigated both at close separation at the innermost force barrier and at larger separations (up to 300-400 Angstrom). The visco-elastic measurements show that the elasticity modulus, G ', dominates over the loss modulus, G , for all studied cases, indicative of a more solid-like than liquid-like film. Finally, it is shown that shear at high contact pressures induces new aggregate structures at the surface.

  • 10.
    Cadario, Alessandro
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Alfredsson, Bo
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Fretting fatigue experiments and analyses with a spherical contact in combination with constant bulk stress2006In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 39, no 10, p. 1248-1254Article in journal (Refereed)
    Abstract [en]

    A fretting experiment with separate control of bulk stress, normal and tangential contact loads is presented. For the initial test series, constant normal and bulk loads were combined with a cyclic tangential load. Both the spherical indenter and the plane specimen were manufactured from alpha + beta titanium alloys. Strain gauges and acoustic emission measurements were employed for the determination of the time to crack initiation and the propagation life. The fretting cracks always initiated inside the slip zone at positions that were spread over the whole slip zone. Crack nucleation was investigated with five multiaxial fatigue criteria. It was concluded that macroscale stresses from the contact and bulk load alone could not explain all aspects of crack initiation. A possible explanation was found in the fretting-induced roughness. The growth of the fretting crack was simulated numerically by a parametrical description. It was noted that a cyclic bulk load was required to drive the crack growth through the specimen to final failure.

  • 11.
    Cha, Matthew
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Waukesha Bearings, United Kingdom .
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Ghent University, Belgium .
    Nonlinear dynamic behaviour of vertical and horizontal rotors in compliant liner tilting pad journal bearings: Some design considerations2015In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 82, p. 142-152Article in journal (Refereed)
    Abstract [en]

    Dynamic behaviour of vertical and horizontal rotors in journal bearings with line pivot pads is investigated. Two bearing designs are compared: one with white metal pads and another with compliant liner pads. The influence of elasticity of the liner on the journal orbits is investigated. Some practical aspects of the compliant liner pad design are discussed. Compliant bearing design parameters such as preload factor, pivot offset, radial clearance, viscoelasticity, and pad inclination to control the size of the journal orbit are considered.

  • 12.
    Cha, Matthew
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Isaksson, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Influence of pad compliance on nonlinear dynamic characteristics of tilting pad journal bearings2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 57, p. 46-53Article in journal (Refereed)
    Abstract [en]

    The effect of pad compliance on the dynamic response of tilting pad journal bearings is investigated. Pad compliance is varied by changing pivot geometry and Young's modulus of pad backing and pad liner. Two pad support configurations are considered: one that allows only circumferential tilt and another one that allows both circumferential and axial tilts. Journal orbits, oil film pressure and oil film thickness are compared and discussed. It is shown that higher pad backing compliance significantly increases the journal orbit size and results in an increase in oil film pressure while oil film thickness is decreased. With a compliant liner, oil film pressure is decreased while oil film thickness is increased. Tapers at the pad edges are essential to increase the global minimum oil film thickness in compliant liner bearings.

  • 13. Cupillard, Samuel
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Cervantes, Michel
    3D thermohydrodynamic analysis of a textured slider2009In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 42, no 10, p. 1487-1495Article in journal (Refereed)
    Abstract [en]

    Analysis of a 3D inlet textured slider bearing with a temperature dependent fluid is performed. Numerical simulations are carried out for a laminar and steady flow. Hot and cold lubricant mixing in the groove is modelled and examined for different operating conditions. Thermohydrodynamic performance of the bearing is analysed for different texture lengths. Results show that texture has a stronger and positive influence on load carrying capacity when thermal effects are considered. This beneficial effect is at a maximum for the longest dimples with a length shorter than the pad length. Texture is also beneficial for the load carrying capacity when the sliding speed and inlet flow rate are varied. The load carrying capacity of the slider can be increased by up to 16% in severe operating conditions (high sliding speed).

  • 14.
    de la Presilla, Roman José
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design.
    Leckner, Johan
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design. Axel Christiernsson Int AB, SE-44911 Nol, Sweden..
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design. Univ Ghent, Dept Electrochem Syst & Met Engn, B-9000 Ghent, Belgium.;Univ New South Wales, Sch Chem, Sydney, NSW 2033, Australia..
    Grease lubricity in the fretting contact: Are ionic liquids the solution?2023In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 185, p. 108509-, article id 108509Article in journal (Refereed)
    Abstract [en]

    A statistical, energy-based approach is employed to experimentally characterize the ability of different greases to reduce friction when a point contact is subjected to repeated reciprocal displacements of smaller magnitude than the contact diameter. This approach allows the assessment of lubricant fretting performance with respect to its ability to remain within the contact and also its boundary lubrication properties. The results indicate that composition-dependent boundary lubrication properties of greases loaded with non-halogenated ionic liquids containing bis(oxalato)borate ([BOB]) and bis(mandelato)borate ([BMB]) anions can result in no detectable wear and low friction, even under conditions of moderately high pressures and where the original contact area is never fully uncovered. This discovery paves the way for the development of anti-fretting ionic greases.

  • 15.
    de la Presilla, Roman José
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design.
    Wandel, Sebastian
    Leibniz University Hanover, Institute of Machine Design and Tribology, DE-30167, Hanover, Germany.
    Stammler, Matthias
    Fraunhofer Institute for Wind Energy Systems, Department of Reliability and Validation, DE-21029, Hamburg, Germany.
    Grebe, Markus
    Competence Center for Tribology at University of Applied Sciences Mannheim, D-68163 Mannheim, Germany.
    Poll, Gerhard
    Leibniz University Hanover, Institute of Machine Design and Tribology, DE-30167, Hanover, Germany.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design. Ghent University, Department of Electrical Energy, Metals, Mechanical Constructions and Systems, B-9000 Ghent, Belgium; University of New South Wales, School of Chemistry, NSW 2033, Sydney, Australia.
    Oscillating rolling element bearings: A review of tribotesting and analysis approaches2023In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 188, article id 108805Article, review/survey (Refereed)
    Abstract [en]

    Rolling element bearings, when subjected to small oscillating movements or vibrations, run the risk of being damaged by mechanisms such as Standstill Marks and False Brinelling. Damages resulting from these phenomena can decrease bearing fatigue life and increase wear-induced friction torque. These failures do not correlate well with standard life estimation approaches. Experimental studies play a crucial role in gaining knowledge in this area. The review integrates knowledge from experiments ranging from single contacts to laboratory and full-scale bearings in wind power and aerospace applications. The generalization is achieved using a non-dimensional amplitude parameter that relates rolling element travel during an oscillation to the Hertzian contact size. The review encompasses testing methods, procedures, reporting practices, result scaling, and application-specific considerations.

  • 16.
    Duvefelt, Kenneth
    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.).
    Johannesson, Carl Michael
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Skedung, Lisa
    Model for contact between finger and sinusoidal plane to evaluate adhesion and deformation component of friction2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 96, p. 389-394Article in journal (Refereed)
    Abstract [en]

    One of the main parameters affecting finger friction, friction-induced vibrations in the finger, and consequently tactility is surface topography. Recently Skedung et al. performed finger friction measurements on fine controlled surfaces. These surfaces were sinusoidal with wavelengths from 0.27 to 8.8 mu m and amplitudes from 0.007 to 6 mu m. Building on those tests an analytical model for the contact was developed to explain the differences in friction coefficient. The contact was modelled as trapezoids in a circular pattern pressed against a sinusoidal plane. Results showed that the calculated contact area and therefore friction coefficient corresponded well with the measurements. This model can be used to see how the different surface parameters influence friction.

  • 17.
    Everitt, Carl-Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Alfredsson, Bo
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Contact fatigue initiation and tensile surface stresses at a point asperity which passes an elastohydrodynamic contact2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 123, p. 234-255Article in journal (Other academic)
    Abstract [en]

    Contact mechanics and tribology was combined with fundamental fatigue and fracture mechanics to form a new mechanism for surface initiated rolling contact fatigue. Following, fatigue was investigated numerically for single asperities and craters in lubricated rolling contact surfaces. The hypothesis suggests that asperity point contacts can create sufficiently large tensile stresses for fatigue. The investigated case corresponded to a heavily loaded truck gear with ground surfaces. Reynolds equation resolved the elastohydrodynamic effect of the asperity in the transient three dimensional contacts. The Findley critical plane criterion was used for multiaxial and non-proportional fatigue evaluation. The simulations confirmed the new mechanism for rolling contact fatigue and showed how asperities can create contact fatigue in the lubricated contacts even without slip.

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    fulltext
  • 18.
    Everitt, Carl-Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Alfredsson, Bo
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Surface initiation of rolling contact fatigue at asperities considering slip, shear limit and thermal elastohydrodynamic lubrication2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 137, p. 76-93Article in journal (Refereed)
    Abstract [en]

    A numerical investigation was performed, with single axisymmetric asperities passing through lubricated rolling contacts at different slip. Two explanatory and cooperating phenomena were found as to why the damage develops more frequently at negative than positive slip. Metal contact occurred in the inlet, where tractive asperity contacts at negative slip provided a large tensile surface stress outside the contact. As the asperity moved through the contact, sliding supplied it with lubricant and heated the lubricant along the contact. The shear tractions were thus higher near the inlet than the outlet, making them more detrimental for negative than positive slip.

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    Surface initiation of rolling contact fatigue
  • 19.
    Everitt, Carl-Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Alfredsson, Bo
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    The influence of gear surface roughness on rolling contact fatigue under thermal elastohydrodynamic lubrication with slip2020In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 151, article id 106394Article in journal (Refereed)
    Abstract [en]

    Measured shot peened, ground and worn surfaces were included in thermal elastohydrodynamic lubrication and fatigue simulations. Considering transient temperature fields, shear limit and metal to metal contact, moderate negative slip was found to be more detrimental than positive. The location of pitting in gears was thus explained by the surface roughness and the slide to roll ratio. The λ-ratio correlated with fatigue risk within each surface structure. As a supplement to the λ-ratio the surface skewness qualitatively ranked the fatigue risk between the surface structures.

  • 20.
    Everitt, Carl-Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Vrček, Aleks
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, 971 87, Luleå, Sweden.
    Alfredsson, Bo
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Experimental and numerical investigation of asperities and indents with respect to rolling contact fatigue2020In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 151, article id 106494Article in journal (Refereed)
    Abstract [en]

    Rolling contact experiments with slip were performed on artificial asperities and indents with pile-up. Micro-pits arose at the leading edge of the asperities and classic rolling contact fatigue (RCF) cracks initiated behind the trailing edge of the indents. The elastic-plastic run-in process and the thermal elastohydrodynamic lubrication (TEHL) load cycles were studied numerically. The run-in process caused high tensile residual stresses at the leading edge of the asperities while the TEHL load cycle caused high tensile stresses at the trailing edge of both the asperities and the indents. The conclusion was thus drawn that the classic RCF cracks behind the indents were caused by the TEHL load cycle while the micro-pits at these artificial asperities were caused by the tensile residual stresses from plastic deformation.

  • 21. Fillon, M.
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    PTFE-faced centre pivot thrust pad bearings factors affecting TEHD performance2008In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, no 12, p. 1219-1225Article in journal (Refereed)
    Abstract [en]

    The paper presents a thermoelastohydrodynamic (TEHD) analysis of thrust bearings with polytetrafluoroethylene (PTFE) faced pads. The influence of pad active surface geometry on main characteristics such as temperature profile, film thickness and pressure field are investigated. Due to the high compliance of the PTFE layer, deformations of the active surface due to pressure are quite large and have to be taken into account. The initial geometry of the pad is also of great importance; a parametric study on the pad geometry permits clarification of both geometry and deformation effects. The geometry of the pad, particularly for centrally pivoted pads, has to be considered in order to accurately predict performance of PTFE-faced tilting-pad thrust bearings.

  • 22.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    A method of temperature monitoring in fluid film bearings2004In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 37, no 2, p. 143-148Article in journal (Refereed)
    Abstract [en]

    In the present paper a method to improve temperature monitoring of fluid film bearings is described. The method is tested in an industrial tilting pad thrust bearing. Test results for steady state and transient operating conditions are reported. Temperatures monitored by a thermocouple through the utilisation of the proposed method are compared to those measured by thermocouples in the pad backing and in the collar. The method is also tested on a PTFE-faced bearing. Test results show that the proposed method improves sensitivity to thermal transients in conventional babbitted bearings and provides adequate means of temperature monitoring in the PTFE-faced bearings.

  • 23.
    Glavatskih, Sergei
    et al.
    Luleå University of Technology, Division of Machine Elements.
    Höglund, Erik
    Tribotronics: towards active tribology2008In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, no 9-10, p. 934-939Article in journal (Refereed)
    Abstract [en]

    A constant trend towards more compact mechanical systems with higher power densities and increased thermo-mechanical loads emphasises the importance of the development of new design approaches and novel tribological systems. Ignoring this may cause a significant slow down in technological and industrial development. Tribotronics or active tribology based on adaptive performance is thought of as being critical in the implementation of smart machine concepts. Recognition of the importance of tribotronics, or active control of system loss outputs, such as those through friction and wear will have significant beneficial economic consequences as a result of the associated accelerated rate of technological progress. These smart tribotronic systems can be embedded in a great variety of machines and mechanisms. If this integration is made at the design stage, products that are more flexible, efficient and reliable can be produced. The concept of tribotronics is presented and discussed in this paper. Some illustrativeexamples that show the feasibility of an “active” approach are given. In addition, various possibilities already reported in literature are discussed.

  • 24. Golchin, Arash
    et al.
    Simmons, Gregory F.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Break-away friction of PTFE materials in lubricated conditions2011In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 48, p. 54-62Article in journal (Refereed)
    Abstract [en]

    This study investigates the tribological characteristics at initiation of sliding (break-away friction) of several polytetrafluoroethylene based materials. Four PTFE composites, pure PTFE, and white metal were tested in a reciprocating tribo-meter with the block on plate configuration against a steel counter-surface. Apparent contact pressure and oil temperature were varied from 1 to 8 MPa and 25 to 85 Â°C respectively. SEM investigations revealed wear patterns of the PTFE materials and the abrasive nature of hard fillers. Bronze filled, carbon filled, and pure PTFE were found to provide lower break-away friction and less variation over the course of testing and generally superior properties.

  • 25.
    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.

  • 26. Kawada, S.
    et al.
    Watanabe, Seiya
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Tadokoro, C.
    Tsuboi, R.
    Sasaki, S.
    Lubricating mechanism of cyano-based ionic liquids on nascent steel surface2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 119, p. 474-480Article in journal (Refereed)
    Abstract [en]

    This study investigates the lubricating mechanism of cyano-based ionic liquids on steel surfaces using Q-MS, ToF-SIMS, and TGA. [EMIM][DCN], [EMIM][TCC], [EMIM][TCB], [BMPL][DCN], [BMPL][TCC], and [BMPL][TCB] were selected as lubricants. [EMIM][TCB] exhibited the highest friction coefficient. The others exhibited very low friction coefficients of less than 0.08. Q-MS analysis indicated that the cation components were detected in outgassing during sliding tests. However, anion components were not detected. ToF-SIMS results showed that the anions remained on the worn surfaces which would lead low friction coefficients. To achieve low friction coefficient, the tribo-decomposition of the ionic liquids and adsorption of anion were required. TGA indicated thermal stability was an index for tribo-decomposition on the nascent steel surface.

  • 27.
    Kumar, Mayank
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Atlas Copco Ind Tech AB, S-13154 Nacka, Sweden..
    Persson, Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Atlas Copco Ind Tech AB, S-13154 Nacka, Sweden..
    Sherrington, Ian
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Univ Cent Lancashire, Jost Inst Tribotechnl, Preston PR1 2HE, Lancs, England..
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Univ Ghent, Electromech Syst & Met Engn, B-9052 Ghent, Belgium..
    Changes in friction of zinc flake coated threaded fasteners due to humidity, temperature and storage duration2022In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 170, p. 107498-, article id 107498Article in journal (Refereed)
    Abstract [en]

    The friction coefficient of a specific material combination is often assumed to be invariant in manufacturing processes such as during the tightening of threaded fastener joints. This paper considers the impact of storage conditions on threaded fastener friction. Fasteners were stored in hot humid and sub-zero temperature conditions to study friction in the thread and under-head contacts. Four Zn-flake coatings, commonly used in the automotive industry were considered. Consequent tightening of these fasteners at room temperature revealed that storage history had a significant impact on their friction coefficients, halving under-head friction in some cases. This varied behavior was considered to be a response to coating nano-hardness and structure and differences in adsorption/absorption of water and zinc-oxide formation during storage.

  • 28.
    Kuznetsov, Evgeny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). COMSOL LLC, Russian Federation.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Ghent University, Belgium .
    Dynamic characteristics of compliant journal bearings considering thermal effects2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 94, p. 288-305Article in journal (Refereed)
    Abstract [en]

    A numerical THD model that takes into account mechanical and thermal deformations of a compliant lining is used to investigate the influence of compliance on dynamic characteristics of a two axial groove bearing. A detailed study on the contribution of mechanical and thermal deformation components of the compliant lining to the non-dimensional bearing stiffness and damping is carried out. Thermal deformation is found to increase horizontal stiffness K<inf>yy</inf> and cross-coupled stiffness K<inf>xy</inf> and slightly reduce journal critical mass. Mechanical deformation of the compliant lining is found to decrease damping, reduce vertical and cross-coupled K<inf>xy</inf> stiffness. Radial clearance is found to increase stiffness, except its horizontal component, and decrease horizontal damping. Compliant lining is found to improve bearing stability.

  • 29. Kuznetsov, Evgeny
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Fillon, Michel
    THD analysis of compliant journal bearings considering liner deformation2011In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 44, no 12, p. 1629-1641Article in journal (Refereed)
    Abstract [en]

    A numerical THD model is developed to investigate the effect of lining compliance on the bearing characteristics. The analysis shows increased load carrying capacity, significantly reduced peak pressures and thicker oil film in the loaded zone compared to a white metal bearing. Slightly thinner oil films are predicted at the bearing edges. Temperature and power loss are found to be similar for some load–speed combinations but higher for other operating conditions. It is also shown that load carrying capacity is more sensitive to thermal expansion while pressure and oil film thickness profiles are more sensitive to elastic deformation.

  • 30.
    Li, Xinmin
    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.).
    A study on friction and wear reduction due to porosity in powder metallurgic gear materials2017In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 110, p. 86-95Article in journal (Refereed)
    Abstract [en]

    It has been widely acknowledged that controlled texturing on a surface can contribute to friction and wear reduction at lubricated sliding contact interfaces. This paper investigates the influence on friction and wear of different pore size distributions of powder metallurgy gear materials. The pore sizes are controlled by different densities of the powder metallurgic materials. Two different kinds of powder metallurgy (PM) gear materials were applied and a standard gear material are used as a reference. The friction and wear coefficients of PM materials sliding on PM materials increase with increasing pore size. The friction and wear coefficients of regular steel sliding on PM materials decrease with increasing pore size. No matter what the material of the disc, peeling is one of the main damage mechanisms of powder metallurgy pins with the biggest porosity.

  • 31.
    Li, Xinmin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sosa, Mario
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Martin
    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 efficiency of spur gears made of powder metallurgy materials - ground versus super-finished surfaces2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 95, no 1, p. 211-220Article in journal (Refereed)
    Abstract [en]

    Power loss is one of the main concerns in gear transmission systems. In this study a recirculating power back-to-back FZG test rig was used to investigate the efficiency of spur gears made of powder metallurgy (PM) material using two different surface manufacturing methods (ground and super-finished). The results were compared with previously presented results of standard gear material from the same test rig. The influence of the material (Wrought steel or PM) and surface roughness on the gear mesh efficiency and the total efficiency of the gearbox were analyzed in detail. The Young's modulus for PM materials is lower than for conventional gear steel. This may influence gear tooth bending and the efficiency of the gear transmission. Gear contact simulation results showed that the influence of gear tooth bending on PM gear transmission efficiency can be ignored in the FZG gear geometry. Higher surface energy combined with a smoother surface led to a lower transmission efficiency for the super-finished powder metallurgy gear combination compared to the standard gear material.

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  • 32.
    Lin, Jiachun
    et al.
    Department of Mechanical Engineering, Faculty of Materials and Manufacturing, Beijing University of Technology, China; Beijing Engineering Research Center of Precision Measurement Control and Instruments (Beijing University of Technology), China.
    Fan, Xinyu
    Department of Mechanical Engineering, Faculty of Materials and Manufacturing, Beijing University of Technology, China; Beijing Engineering Research Center of Precision Measurement Control and Instruments (Beijing University of Technology), China.
    Wang, Peng
    Department of Mechanical Engineering, Faculty of Materials and Manufacturing, Beijing University of Technology, China; Beijing Engineering Research Center of Precision Measurement Control and Instruments (Beijing University of Technology), China.
    Li, Yunfei
    Department of Mechanical Engineering, Faculty of Materials and Manufacturing, Beijing University of Technology, China; Beijing Engineering Research Center of Precision Measurement Control and Instruments (Beijing University of Technology), China.
    Shi, Zhaoyao
    Department of Mechanical Engineering, Faculty of Materials and Manufacturing, Beijing University of Technology, China; Beijing Engineering Research Center of Precision Measurement Control and Instruments (Beijing University of Technology), China.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design, System and Component Design.
    Gear wear prediction based on the theorem of degradation entropy generation2024In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 191, article id 109175Article in journal (Refereed)
    Abstract [en]

    Tooth surface material loss caused by gear wear alters the surface morphology of gears, which impacts their vibration, noise, and remaining lifespan. Although gear wear modeling and prediction have been extensively studied, this paper proposes a novel approach based on the theorem of degradation entropy generation (DEG). A point-by-point calculation method is introduced to determine the degradation coefficient for each measurement point on the tooth profile, accounting for varying working conditions along the tooth profile during the actual meshing process of the gear pair. First, the FZG gear's bearing capacity is tested. Next, a surface roughness profilometer is employed to in-situ measure the tooth profile after each load stage. The profile deviation curve and the amount of profile wear following each load stage are obtained by processing the measured profile morphology data. Then, the pitting safety factor for each point on the tooth surface is calculated according to the ISO 6336–22:2018 standard and used to correct the degradation coefficient for that point. Finally, the entropy generation of the system during each load stage of the FZG gear is calculated. The degradation coefficient suggested in the DEG theorem is employed to link gear wear with system entropy generation, realizing gear wear modeling and prediction. The results demonstrate that the gear wear calculation method based on the DEG theorem can accurately predict the evolution of tooth profile surface morphology during the experimental process. This research provides a unified calculation method for surface morphology evolution caused by gear wear during service.

  • 33.
    Lin, Jiachun
    et al.
    Beijing Univ Technol, Fac Mat & Mfg, Dept Instrument Sci & Technol, Beijing, Peoples R China.;Beijing Univ Technol, Beijing Engn Res Ctr Precis Measurement Control &, Beijing, Peoples R China..
    Teng, Chen
    Beijing Univ Technol, Fac Mat & Mfg, Dept Instrument Sci & Technol, Beijing, Peoples R China.;Beijing Univ Technol, Beijing Engn Res Ctr Precis Measurement Control &, Beijing, Peoples R China..
    Bergstedt, Edwin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Li, Hanxiao
    Beijing Univ Technol, Fac Mat & Mfg, Dept Instrument Sci & Technol, Beijing, Peoples R China.;Beijing Univ Technol, Beijing Engn Res Ctr Precis Measurement Control &, Beijing, Peoples R China..
    Shi, Zhaoyao
    Beijing Univ Technol, Fac Mat & Mfg, Dept Instrument Sci & Technol, Beijing, Peoples R China.;Beijing Univ Technol, Beijing Engn Res Ctr Precis Measurement Control &, Beijing, Peoples R China..
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A quantitatively distributed wear-measurement method for spur gears during micro-pitting and pitting tests2021In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 157, article id 106839Article in journal (Refereed)
    Abstract [en]

    FZG gear testing is widely used to evaluate the performance of lubricants, gear materials, and gear-tooth geometries under different loads. During these tests, gear tooth wear results in the loss of gear profile in the form of micro-pitting, pitting and scuffing, can be observed. However, gear wear is usually measured by weighting. This method cannot be used to study the wear depth on a specific point on the gear-tooth surface. In this study, tooth profiles were measured via a profilometer during the FZG gear-pitting test. Moreover, an algorithm was developed to quantitatively evaluate the distributed cumulative wear and wear progress at a certain test stage. Simultaneously, the real tooth profile was obtained. Experiments were performed to validate the proposed method, and the results showed that gear-tooth-surface wear can be quantitatively determined. Thus, the proposed method can be used for further gear-failure-prediction experiments.

  • 34.
    Lyu, Yezhe
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Bergseth, Ellen
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Tu, Minghui
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Effect of humidity on the tribological behaviour and airborne particle emissions of railway brake block materials2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 118, p. 360-367Article in journal (Refereed)
    Abstract [en]

    A pin-on-disc tribometer placed in a one-way ventilated chamber was used to investigate the effect of relative humidity on the tribology and airborne particle emission of three commercial railway brake block materials (grey cast iron, organic composite, and sintered). Cast iron showed the highest friction coefficient, particle emission and wear loss and organic composite exhibited the lowest. The generation of oxide layers on the worn cast iron surface resulted in a decrease in friction, particle emission and wear. Moisture adsorption by the organic composite leads to decreased friction coefficient and particle emission with increasing humidity. Relative humidity does not affect the friction coefficient of the sintered brake block, whose particle emission and wear loss significantly decline with increasing relative humidity.

  • 35.
    Lyu, Yezhe
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Leonardi, Mara
    Trento University.
    Wahlström, Jens
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Gialanella, Stefano
    Trento University.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Friction, wear and airborne particle emission from Cu-free brake materials2020In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 141, article id 105959Article in journal (Refereed)
    Abstract [en]

    Cu is required to be abated in brake pads due to its toxicity. There are on the market several Cu-free brake pads. These Cu-free brake pads are only evaluated regarding their friction and wear performance, whereas, their airborne particle emissions are not considered. A pin-on-disc tribometer is used to evaluate the friction, wear and airborne particle emission from two Cu-free commercial brake pads used in the Europe. Moreover, a commercial brake pad containing Cu is evaluated as a reference. The results indicate that Cu-free brake pads yield comparable coefficient of friction as the Cu-contained brake pad. All three brake materials result in similar wear to the mating brake rotor. Cu-free brake pads generate more airborne particles than Cu-contained brake pad.

  • 36. Mallipeddi, D.
    et al.
    Norell, M.
    Sosa, Mario
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Nyborg, L.
    Influence of running-in on surface characteristics of efficiency tested ground gears2017In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 115, p. 45-58Article in journal (Refereed)
    Abstract [en]

    The effect of running-in load (0.9 or 1.7 GPa) on surface characteristics of ground spur gears, and on their development during subsequent efficiency testing (FZG rig), is examined. The effect was confined to less than 10 μm depth. Micropitting was associated with surface asperities and their plastic deformation; higher running-in load gave more micropitting, also after identical efficiency tests. Running-in increased unequal compressive residual stresses in both profile and axial directions, while after efficiency testing they approached equal levels. Deformation induced martensite is considered to form during running-in only at high load, still the amount after efficiency testing increased with running-in load. Higher surface content of phosphorous from extreme pressure additive (EP) occurred only after efficiency test following running-in at high load.

  • 37.
    Mallipeddi, D.
    et al.
    Chalmers Univ Technol, Ind & Mat Sci, SE-41296 Gothenburg, Sweden..
    Norell, M.
    Chalmers Univ Technol, Ind & Mat Sci, SE-41296 Gothenburg, Sweden..
    Sosa, Mario
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Nyborg, L.
    Chalmers Univ Technol, Ind & Mat Sci, SE-41296 Gothenburg, Sweden..
    The effect of manufacturing method and running-in load on the surface integrity of efficiency tested ground, honed and superfinished gears2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 131, p. 277-287Article in journal (Refereed)
    Abstract [en]

    This study compares gear surface characteristics generated by grinding, honing and superfinishing of casehardened steel, including the evolution during efficiency testing with two different prior running-in loads (0.9 GPa and 1.7 GPa). The most influential factor was surface roughness. Micro-pitting was associated with surface asperities and hence only seen in ground and honed gears, while being absent for super-finished gears. The micro-pitting was enhanced by running-in load, but only for rough surfaces. Deformation-induced localized microstructure impact was associated with cracks. Residual stresses reached similar levels after efficiency testing. Phosphorous content in the gear surface was connected to surface roughness and running-in load.

  • 38. Matějka, V.
    et al.
    Metinöz, I.
    Wahlström, Jens
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). System- o Komponentdesign.
    Alemani, M.
    Perricone, G.
    On the running-in of brake pads and discs for dyno bench tests2017In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 115, p. 424-431Article in journal (Refereed)
    Abstract [en]

    Running-in process of low metallic brake pads and cast iron discs are investigated using full scale inertia brake dynamometer designed for particle emission studies. The airborne particles are measured using ELPI+ and collected on filters. The pads and disc contact surfaces are studied using microscopy techniques. It is observed that the particle emissions from the new pads and discs are significantly higher compared with the used ones and indicates importance of proper running-in of the pads and disc for wear particle emission tests. The results also indicate that pads and disc pairs which are able to stabilize friction behavior faster will produce less particle emissions which could influence the strategies of brake material formulations or steps during their production.

  • 39.
    Nilsson, Rickard
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Sundvall, Krister
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Filtration and coating effects on self-generated particle wear in boundary lubricated roller bearings2005In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 38, no 2, p. 145-150Article in journal (Refereed)
    Abstract [en]

    A specially designed test system involving boundary lubricated roller bearings was used to study wear at low particle concentration levels. A separate oil system circulated the oil through the test bearings. The effects of self-generated contaminants from the system were studied. Even at very low concentration levels, self-generated contaminants can cause significant wear. The concentration of self-generated particles was very high during the running-in period. It is therefore important that the filtration be very efficient during this period. The experimental results show that filtration during run-in for 1 h with a 3 μm filter can reduce both the mass loss and the number of self-generated particles by a factor of 10. Furthermore, the results also show that while the bearings with standard rollers can have significant wear, those with coated rollers are at the same time almost unaffected by wear. Also, the number of particles generated in the contact was significantly less when using coated rollers. There were twice as many self-generated particles when using a standard bearing as those compared with a coated bearing.

  • 40.
    Nosko, Oleksii
    et al.
    Saitama University, Japan .
    Nagamine, T.
    Mori, H.
    Sato, Y.
    Theoretical study of thermofrictional oscillations due to negative friction-temperature characteristic2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 61, p. 235-243Article in journal (Refereed)
    Abstract [en]

    Analytical study on oscillations of a body on a moving counterbody has been done by assuming imperfect frictional thermal contact and friction that decreases with contact temperature. It has been shown that stick-slip oscillation occurs due to decrease of friction coefficient when the body moves in the opposite direction to the counterbody. Dynamical characteristics, such as conditions for stable sliding and limit cycles, have been studied. Normal force between the bodies has significant effect on sliding stability.

  • 41.
    Nosko, Oleksii
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Nagamine, T.
    Nosko, A. L.
    Romashko, A. M.
    Mori, H.
    Sato, Yuichi
    Measurement of temperature at sliding polymer surface by grindable thermocouples2015In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 88, p. 100-106Article in journal (Refereed)
    Abstract [en]

    This paper is devoted to experimental study of capabilities and limitations of grindable thermocouples as applied to polymer materials sliding on metal. Chromel-alumel and chromel-copel grindable thermocouples have been developed and tested for wide ranges of contact pressure and sliding velocity. The background temperature of the sliding surface can be determined as the lower envelope of the signal from the grindable thermocouple. Steady and unsteady regimes of sliding have been investigated. For steady sliding, the accuracy of the temperature determination increases with measurement duration. In the case of unsteady sliding, accurate temperature determination requires multiple tests under the same conditions. The thickness of the thermocouple junction has been analyzed for correct comparison of experimental and calculated temperatures.

  • 42.
    Olofsson, Ulf
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    On the identification of wear modes and transitions using airborne wear particles2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 59, no SI, p. 104-113Article in journal (Refereed)
    Abstract [en]

    A novel test method was used to identify how contact conditions influence the wear modes and transitions for sliding steel-on-steel contacts. The test equipment was a pin-on-disc tribometer equipped with instruments for counting airborne particles. The results show that the dominant wear mode significantly influences the number of airborne particles generated from the contact. During mild wear few or no measurable airborne particles were generated. The transitional running-in process could also be identified by airborne particle measurement analysis.

  • 43.
    Olsson, Erik
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Larsson, Per Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    A unified correlation model describing global properties at elastoplastic sharp indentation contact2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 103, p. 252-260Article in journal (Refereed)
    Abstract [en]

    The correlation of sharp indentation testing is analyzed and discussed based on present and previous numerical findings. In particular, correlation of two global indentation properties, hardness and relative contact area, at sharp indentation of classical elastic-plastic materials is discussed in detail. It is shown that the results cannot in general, and in particular at high strain hardening, be correlated accurately using a single parameter, comprising both geometrical and mechanical properties, with the uniaxial stress-strain curve represented by the flow stress at a representative value on the effective plastic strain. Instead, also the level of the plastic hardening must be considered. Based on this finding, a unified model for correlation of global properties is presented for cone indentation of elastoplastic materials.

  • 44.
    Riva, Gabriele
    Brembo S.p.A..
    An FEA approach to simulate disc brake wear and airborne particleemissions2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 138, p. 90-98Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Emissions from disc brake wear adversely affect the air quality in cities. Finite Element Analysis (FEA) approachesfocussing on the macroscopic wear of pads and rotors can be found in the literature, but none of thesetake the wear and emission dependence of the local contact pressure and sliding speed into account. The aim ofthe present study is to further develop an FEA approach for simulation of macroscopic wear and airborneemission to include the dependences of local contact pressure and sliding speed by implementing wear andemission maps obtained by pin-on-disc tribometer tests. Results from a dyno bench test are compared withsimulated results. The simulated rotor and pads wear, and airborne emissions are in line with the measuredvalues.

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  • 45.
    Riva, Gabriele
    et al.
    Brembo S.p.A., Stezzano, BG, Italy.
    Valota, Giorgio
    Brembo S.p.A., Stezzano, BG, Italy.
    Perricone, Guido
    Brembo S.p.A., Stezzano, BG, Italy.
    Wahlström, Jens
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). 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.
    An FEA approach to simulate disc brake wear and airborne particle emissions2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 138, p. 90-98Article in journal (Refereed)
    Abstract [en]

    Emissions from disc brake wear adversely affect the air quality in cities. Finite Element Analysis (FEA) approaches focussing on the macroscopic wear of pads and rotors can be found in the literature, but none of these take the wear and emission dependence of the local contact pressure and sliding speed into account. The aim of the present study is to further develop an FEA approach for simulation of macroscopic wear and airborne emission to include the dependences of local contact pressure and sliding speed by implementing wear and emission maps obtained by pin-on-disc tribometer tests. Results from a dyno bench test are compared with simulated results. The simulated rotor and pads wear, and airborne emissions are in line with the measured values.

  • 46.
    Rohlmann, Patrick
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design.
    Black, Jeffrey J.
    Univ New South Wales, Sch Chem, Sydney, NSW 2052, Australia..
    Watanabe, Seiya
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Osaka Univ, 1-1 Machikaneyama, Toyonaka, Osaka 5600043, Japan..
    Leckner, Johan
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design. Axel Christiernsson Int AB, SE-44911 Nol, Sweden..
    Shimpi, Manishkumar R.
    Luleå Univ Technol, Chem Interfaces, SE-97187 Luleå, Sweden.;Stockholm Univ, Dept Mat & Environm Chem, Stockholm, Sweden..
    Rutland, Mark W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Univ New South Wales, Sch Chem, Sydney, NSW 2052, Australia.;Ecole Cent Lyon, Lab Tribol & Dynam Syst, F-69134 Ecully, France..
    Harper, Jason B.
    Univ New South Wales, Sch Chem, Sydney, NSW 2052, Australia..
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design. Univ New South Wales, Sch Chem, Sydney, NSW 2052, Australia.;Univ Ghent, Dept Electromech Syst & Met Engn, B-9052 Ghent, Belgium..
    Tribochemistry of imidazolium and phosphonium bis(oxalato)borate ionic liquids: Understanding the differences2023In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 181, p. 108263-, article id 108263Article in journal (Refereed)
    Abstract [en]

    Lubrication properties of imidazolium and phosphonium bis(oxalato)borate ionic liquids (ILs) are compared in a reciprocating sliding contact at 80 degrees C and 140 degrees C. Both the influence of the alkyl chain length and the cation architecture on friction, wear and lubricant breakdown are investigated. Imidazolium ILs showed lower friction than phosphonium ILs though only phosphonium-based ILs reduced wear. A longer alkyl chain reduced friction only in the case of the imidazolium-based ILs. Analysis of the wear scars was consistent with chemical breakdown solely of the anion. Chemical changes in the ILs after the tribotests were more pronounced for imidazolium-based ILs, and comparison of breakdown and tribofilm formation implicated catalysis by the imidazolium center, which, in turn, had a strong dependence on the surface self-assembly.

  • 47.
    Rohlmann, Patrick
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Watanabe, Seiya
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Tokyo Univ Sci, Dept Mech Engn, Katsushika Ku, 6-3-1 Niijuku, Tokyo 1258585, Japan..
    Shimpi, Manishkumar R.
    Luleå Univ Technol, Chem Interfaces, S-97187 Luleå, Sweden..
    Leckner, Johan
    Axel Christiernsson Int AB, SE-44911 Nol, Sweden..
    Rutland, Mark W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Univ New South Wales, Sch Chem, UNSW Sydney, Sydney, NSW 2052, Australia.;RISE Res Inst Sweden, Surfaces Proc & Formulat, SE-10044 Stockholm, Sweden..
    Harper, Jason B.
    Univ New South Wales, Sch Chem, UNSW Sydney, Sydney, NSW 2052, Australia..
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Univ New South Wales, Sch Chem, UNSW Sydney, Sydney, NSW 2052, Australia.;Univ Ghent, Dept Electromech Syst & Met Engn, B-9052 Ghent, Belgium..
    Boundary lubricity of phosphonium bisoxalatoborate ionic liquids2021In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 161, article id 107075Article in journal (Refereed)
    Abstract [en]

    The lubricating performance of trihexyl(tetradecyl)phosphonium bisoxalatoorthoborate (P-BOB) ionic liquid is analysed at 80 degrees C and 140 degrees C, and compared to an ionic liquid containing a partially hydrated version of the anion. The reduction of the anions produces oxalate complexes that contribute synergistically to lower friction. The role of oxalate in enhancing lubricity was indicated by the fact that the partially hydrated anion is a precursor orthoborate anion complexed with oxalic acid. It consequently showed the lowest friction at 80 degrees C. Upon heating, the precursor was converted into [BOB]- and displayed the same friction at 140 degrees C as the fully synthesised species. The mechanisms of the breakdown of the [BOB]- anion and formation of the tribofilm are elucidated.

  • 48. Sahlin, Fredrik
    et al.
    Almqvist, Andreas
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Larsson, Roland
    Rough surface flow factors in full film lubrication based on a homogenization technique2007In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, no 7, p. 1025-1034Article in journal (Refereed)
    Abstract [en]

    This paper describes a method to compute the flow factors that compensate for an arbitrary surface roughness in a compressible hydrodynamic lubrication based on a homogenization technique. The Reynolds equation is used as the governing equation and the two-scale expansion involved in the homogenization process enables the local roughness scale to be treated separately from the global geometry scale. With this method, it is possible to compute the flow factors for any deterministic roughness. Measured two-dimensional surface profiles are used as examples. Profiles having the same Abbot curve are also shown to have the same flow factors, providing an efficient classification of surfaces in hydrodynamic two-dimensional contacts. Flow factors are computed for the rough surface profiles, and solutions for global bearing geometry are obtained and compared with the corresponding solutions from a smooth geometry.

  • 49. Sahlin, Fredrik
    et al.
    Almqvist, Andreas
    Larsson, Roland
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    A cavitation algorithm for arbitrary lubricant compressibility2007In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, no 8, p. 1294-1300Article in journal (Refereed)
    Abstract [en]

    A general cavitation algorithm that accommodates for an arbitrary density-pressure relation is presented. It is now possible to model the compressibility of the lubricant in such a way that the density-pressure relation is realistic throughout the contact. The algorithm preserves mass continuity for cavitation caused by bearing geometry and surface topography. It is a commonly accepted physical assumption that the contribution of the pressure driven flow is negligible in the cavitated region. This phenomenon is adopted in the present algorithm, which is similar to that of Elrod, and is modeled by a switch function that terminates the pressure gradient at the cavitation regions. Results with this algorithm for different density-pressure relations are presented and discussed. The effects of inlet conditions, such as surface roughness and starvation, on the load carrying capacity of the contact are analyzed.

  • 50.
    Salmeron, Gabriel Calderon
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Leckner, Johan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Axel Christiernsson International AB, Nol, Sweden.
    Schwack, Fabian
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Westbroek, René
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Department of Electromechanical, Systems and Metal Engineering, Ghent University, Belgium; School of Chemistry, University of New South Wales, Sydney, Australia.
    Greases for electric vehicle motors: thickener effect and energy saving potential2022In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 167, p. 107400-107400, article id 107400Article in journal (Refereed)
    Abstract [en]

    Electric vehicle motors in e-drivetrain are equipped with grease-lubricated bearings operating at both low and high speeds with frequent speed changes. The grease-bearing system must secure a long lifespan and low frictional torque to improve efficiency and sustainability. The present paper focuses on the influence of two types of thickener, lithium complex and polypropylene, on the grease lubrication performance under conditions typical for e-motors. The comparison of both thickeners is performed in terms of friction torque and energy consumption in eight long-duration experiments (337 hr). The results show that the polypropylene thickener provides 21.5% lower energy consumption compared to the lithium complex. Changes in grease rheology and degradation in the tests are analysed and correlated with the grease lubrication performance.

12 1 - 50 of 69
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