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  • 1.
    Abbasi, Saeed
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Sellgren, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Pin-on-disc study of the effects of railway friction modifiers on airborne wear particles from wheel-rail contact2013Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 60, s. 136-139Artikkel i tidsskrift (Fagfellevurdert)
    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.

    Fulltekst (pdf)
    peerreviewad version
  • 2.
    Aiso, Toshiharu
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Kubota, Manabu
    Nippon Steel & Sumitomo Metal Corporation.
    Jacobson, Staffan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Effect of Si and Cr additions to carbon steel on material transfer in a steel/TiN coated tool sliding contact2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 97, s. 337-348Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A crossed cylinders sliding test, simulating the contact between the chip and the tool in machining, is used to evaluate material transfer and friction characteristics of a TiN coating against specifically designed model steels. These include one base reference, only alloyed with C (Base steel) and two alloyed also with 1 mass% Si or Cr. When sliding against the Base steel, an Fe-O layer is formed on the coating. Against the Si and Cr alloyed steels, Fe-Si-O and Fe-Cr-O layers are formed. In these oxides, Si and Cr are enriched, i.e. preferentially transferred from the steels. Compared to the Base steel, the friction coefficient is significantly lower against the Si alloyed steel and higher against the Cr alloyed steel.

  • 3.
    Aiso, Toshiharu
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Kubota, Manabu
    Nippon Steel & Sumitomo Metal Corporation.
    Jacobson, Staffan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Influence of Mn and Al additions to carbon steel on material transfer and coating damage mechanism in a sliding contact between steel and TiN coated HSS tool2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 101, s. 414-424Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A crossed cylinders sliding test, simulating the contact between the chip and the cutting tool, is used to evaluate material transfer, friction characteristics and coating damage of a TiN coated high speed steel against specifically designed model steels. These steels include one reference with C as the only alloy element (Base steel), and two alloyed also with 1 mass% Mn or Al. When sliding against the Base steel, an Fe–O layer forms on the coating and protects it from wear. Against the Mn alloyed steel, Fe–Mn–O forms, which has no protective effect. Against the Al alloyed steel, an almost pure Al–O layer forms. This leads to the highest friction, rapidly causing substrate softening and coating fracture.

  • 4.
    Alemon, B.
    et al.
    University of Guadalajara, Mexico; Tecnol Monterrey, Mexico.
    Flores, M.
    University of Guadalajara, Mexico.
    Ramirez, W.
    University of Guadalajara, Mexico.
    Huegel, J. C.
    Tecnol Monterrey, Mexico.
    Broitman, Esteban
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Tribocorrosion behavior and ions release of CoCrMo alloy coated with a TiAlVCN/CNx multilayer in simulated body fluid plus bovine serum albumin2015Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 81, s. 159-168Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    While the CoCrMo biomaterial is currently employed in artificial joints, there are medical concerns regarding its metal ion release and material loss caused by tribocorrosion. In this work, a TiAlVCN/CNx multilayer coating has been employed to improve the tribocorrosion-resistance of the CoCrMo substrate. During the tribocorrosion test, with the sample immersed in a simulated body fluid containing bovine serum albumin, open-circuit potential measurements showed more noble potential as well as a reduction of both the friction coefficient and wear-rate during the sliding phase. Inductive coupled plasma results demonstrate that the multilayer coating effectively blocked the emigration of metallic ions.

    Fulltekst (pdf)
    fulltext
  • 5.
    AlMotasem, Ahmed Tamer
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Holleboom, Thijs Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Adhesion between ferrite iron-€“iron/cementite countersurfaces: A molecular dynamics study2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 103, s. 113-120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adhesive properties of Fe(110)/Fe(110) and Fe3C(001)/Fe(110) countersurfaces have been investigated by using classical molecular dynamics simulations. The simulation results show that Fe3C/Fe exhibits a relatively lower adhesion compared to the Fe/Fe. Additionally, the temperature dependence of the adhesive properties between 300–700 K has been examined. The results demonstrate that, with increasing the temperature, the values of the adhesion force and the work of adhesion continuously decrease in the case of Fe3C/Fe; they initially slightly increase up to 500 K then decrease in the case of Fe/Fe. Furthermore, the effect of lattice coherency between Fe/Fe has been examined and found to slightly reduce the adhesion. These results explain how carbides improve galling resistance of tool steel observed during dry sliding. 

  • 6.
    AlMotasem, Ahmed Tamer
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Posselt, Matthias
    Helmholtz Zentrum Dresden-Rossendorf, Germany.
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Nanoindentation and nanoscratching of a ferrite/austenite iron bi-crystal: An atomistic study2018Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 127, s. 231-239Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molecular dynamics simulations are applied to investigate the wear/friction behavior of a ferrite/austenite iron bi-crystal, as a model system for duplex stainless steels. The plasticity of the ferrite phase is dominated by dislocations while both dislocations and stacking faults are the primary cause of plastic deformation of the austenite phase. Interestingly, the responses of tribological parameters vary depending on the scratch direction. For instance, the scratch hardness is increased by about 46% whereas the friction coefficient is reduced by about 22% when scratch starts from austenite to ferrite. At the interface, a local softening/hardening occurs because of dislocation-interface interaction. The present results demonstrate that martensitic phase transformation is responsible for experimentally observed high amount of ferrite of the pile-up.

  • 7. Almqvist, A.
    et al.
    Essel, E.
    Persson, Lars-Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik.
    Wall, P.
    Homogenization of the unstationary incompressible Reynolds equation2007Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, nr 9, s. 1344-1350Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper is devoted to the effects of surface roughness during hydrodynamic lubrication. In the numerical analysis a very fine mesh is needed to resolve the surface roughness, suggesting some type of averaging. A rigorous way to do this is to use the general theory of homogenization. In most works about the influence of surface roughness, it is assumed that only the stationary surface is rough. This means that the governing Reynolds type equation does not involve time. However, recently, homogenization was successfully applied to analyze a situation where both surfaces are rough and the lubricant is assumed to have constant bulk modulus. In this paper we will consider a case where both surfaces are assumed to be rough, but the lubricant is incompressible. It is also clearly demonstrated, in this case that homogenization is an efficient approach. Moreover, several numerical results are presented and compared with those corresponding to where a constant bulk modulus is assumed to govern the lubricant compressibility. In particular, the result shows a significant difference in the asymptotic behavior between the incompressible case and that with constant bulk modulus.

  • 8.
    Almqvist, Andreas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Dasht, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    The homogenization process of the Reynolds equation describing compressible liquid flow2006Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 39, nr 9, s. 994-1002Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper summarizes the homogenization process of rough, hydrodynamic lubrication problems governed by the Reynolds equation used to describe compressible liquid flow. Here, the homogenized equation describes the limiting result when the wavelength of a modeled surface roughness goes to zero. The lubricant film thickness is modeled by one part describing the geometry/shape of the bearing and a periodic part describing the surface topography/roughness. By varying the periodic part as well as its wavelength, we can try to systematically investigate the applicability of homogenization on this type of problem. The load carrying capacity is the target parameter; deterministic solutions are compared to homogenized by this measure. We show that the load carrying capacity rapidly converges to the homogenized results as the wavelength decreases, proving that the homogenized solution gives a very accurate representation of the problem when real surface topographies are considered

  • 9.
    Almqvist, Andreas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Essel, Emmanuel Kwame
    Persson, Lars-Erik
    Wall, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Homogenization of the unstationary incompressible Reynolds equation2007Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, nr 9, s. 1344-1350Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper is devoted to the effects of surface roughness during hydrodynamic lubrication. In the numerical analysis a very fine mesh is needed to resolve the surface roughness, suggesting some type of averaging. A rigorous way to do this is to use the general theory of homogenization. In most works about the influence of surface roughness, it is assumed that only the stationary surface is rough. This means that the governing Reynolds type equation does not involve time. However, recently, homogenization was successfully applied to analyze a situation where both surfaces are rough and the lubricant is assumed to have constant bulk modulus. In this paper we will consider a case where both surfaces are assumed to be rough, but the lubricant is incompressible. It is also clearly demonstrated, in this case that homogenization is an efficient approach. Moreover, several numerical results are presented and compared with those corresponding to where a constant bulk modulus is assumed to govern the lubricant compressibility. In particular, the result shows a significant difference in the asymptotic behavior between the incompressible case and that with constant bulk modulus.

  • 10.
    Almqvist, Andreas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Sahlin, Fredrik
    Larsson, Roland
    Glavatskikh, Sergei
    On the dry elasto-plastic contact of nominally flat surfaces2007Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, nr 4, s. 574-579Artikkel i tidsskrift (Fagfellevurdert)
    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 profiler used 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.

  • 11. 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 surfaces2007Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, nr 4, s. 574-579Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 12. Almqvist, Torbjörn
    et al.
    Almqvist, Andreas
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    A comparison between computational fluid dynamic and Reynolds approaches for simulating transient EHL line contacts2004Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 37, nr 1, s. 61-69Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When simulating elastohydrodynamic lubrication (EHL), the Reynolds equation is the predominating partial differential equation for prediction of the fluid flow. Also very few attempts have been carried out using the full momentum and continuity equations separately. The aim of this investigation is to compare two different approaches for simulation of EHL line contacts where a single ridge travels through an EHL conjunction. One of the approaches is based on the Reynolds equation, addressing the coupling between the pressure and the film thickness. The solver uses the advantages of multilevel techniques to speed up the convergence rate. The other approach is based on commercial CFD software. The software uses the momentum and continuity equations in their basic form, enabling numerical simulations outside the contact regions, as well as in the thin film region to be carried out. The numerical experiments show that, under the running conditions chosen, only small deviations between the two approaches can be observed. The results are encouraging from several viewpoints: validation of the codes, the possibilities of further developments of the CFD approach and the justification of using a Reynolds approach under the running conditions chosen

  • 13. Almqvist, Torbjörn
    et al.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    The Navier-Stokes approach for thermal EHL line contact solutions2002Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 35, nr 3, s. 163-170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The complicated nature of the EHL-problem has so far forced researchers to develop their own computer codes. These codes are ultimately based on the Reynolds equation, and if thermal EHL-simulations are required, a simultaneous solution of the equation of energy also has to be performed. To date only a few attempts to solve the full equations of momentum and continuity as well as equations of energy have been performed. However, such an approach will give extended possibilities of simulating EHL-contacts; i.e. the computational domain can be expanded and it will be possible to simulate the flow, not only in the contact but also around the contact. Another possibility is to investigate how the altering length scales of the surface roughness influence the behaviour of the flow in the contact. However, the aim of the work presented in this paper is to investigate the possibilities of using a commercial CFD-code (computational fluid dynamics code) based on the above-mentioned equations for simulating thermal EHL. The rheology is assumed to be Newtonian and the equations of momentum and continuity are then commonly referred to as the Navier-Stokes equations (N-S equations). The geometry chosen for the simulations is a smooth line contact geometry, for which the results from the simulations show that it is possible to use the N-S equations for thermal EHL for contact pressures up to approximately 0.7 GPa. The code used in this work is the commercial CFD software (CFX 4.3 user guide). There is a limitation in the N-S approach due to a singularity that can occur in the equation of momentum when the principal shear stresses in the film become too high. However, a thermal approach makes it possible to simulate EHL-contacts at higher loads compared with an isothermal approach, due to the reduction of the viscosity in the former approach. The singularity is not present in the Reynolds approach.

  • 14.
    Almqvist, Torbjörn
    et al.
    LKAB.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Thermal transient rough EHL line contact simulations by aid of computational fluid dynamics2008Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, nr 8, s. 683-693Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reynolds equation is the pre-dominantly used PDE for modelling the fluid flow or more accurately the fluid pressure in an elastohydrodynamic lubrication (EHL) contact. The equation is derived by combining the two conservation equations of momentum and continuity into a single equation for the fluid pressure. The numerical approach for theoretical investigations performed on EHL contacts in this work is somewhat different. The modelling of the fluid flow is based on a computational fluid dynamic (CFD) technique. The fluid flow is simulated by aid of the equations of momentum and continuity in a more complete form and when the thermodynamics is incorporated, the equation of energy. The aim of the investigation was to examine whether the CFD technique could be used to handle thermal transient rough EHL line contacts. It is shown that commercial CFD software can be modified to meet such requirements. The influence of thermal effects on the flow under sliding motion was investigated. The non-Newtonian model used in this work is the Ree-Eyring model. It is shown that the choice of the Eyring stress in the model influences flow in the contacts. If the thermal properties of the surrounding solids differ, it has been shown experimentally and theoretically that a dimple or increased central film thickness may appear in the EHL contacts. This work shows that the governing mechanisms that result in the dimple are also present in thermal transient rough EHL line contacts.

  • 15.
    Anderberg, Cecilia
    et al.
    Volvo Cars Corporation, Gothenburg, Sweden.
    Dimkovski, Zlate
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, Rydberglaboratoriet för tillämpad naturvetenskap (RLAS).
    Rosén, Bengt Göran
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, Rydberglaboratoriet för tillämpad naturvetenskap (RLAS).
    Thomas, Tom R.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, Rydberglaboratoriet för tillämpad naturvetenskap (RLAS).
    Low friction and emission cylinder liner surfaces and the influence of surface topography and scale2019Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 133, s. 224-229Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A low friction piston ring pack, with tangential load halved, was tested in engines with four different cylinder liner finishes. Oil consumption, oil temperature and liner surface temperature were monitored at different load and speed levels, under similar test conditions. The two smoother surfaces generally kept lower oil consumption compared to the two rougher ones. Results were correlated using an area-fractal analysis. The relative area of the surface was calculated at different scales and the result was compared with the level of oil consumption for the different liner surfaces at different engine speeds. It was found that oil consumption was strongly correlated with scale for areas of above 1000 μm2 and below 20 μm2.  © 2018

  • 16.
    Andersson, Martin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Sosa, Mario
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    The effect of running-in on the efficiency of superfinished gears2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 93, s. 71-77Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 17.
    Andersson, Sören
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Björklund, Stefan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Söderberg, Anders
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Frictions models for sliding dry, boundary and mixed lubricated contacts2007Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, s. 580-587Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 18.
    Bakoglidis, Konstantinos
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. SKF Engineering and Research Centre, Tribology and Lubrication Department, Nieuwegein, The Netherlands.
    Nedelcu, Ileana
    SKF Engineering and Research Centre, Tribology and Lubrication Department, Nieuwegein, The Netherlands.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Meeuwenoord, Ralph
    SKF Engineering and Research Centre, Tribology and Lubrication Department, Nieuwegein, The Netherlands.
    Schmidt, Susann
    IHI Ionbond AG, Olten, Switzerland.
    Janzén, Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Ehret, Pascal
    SKF Engineering and Research Centre, Tribology and Lubrication Department, Nieuwegein, The Netherlands.
    Greczynski, Grzegorz
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rolling performance of carbon nitride-coated bearing components in different lubrication regimes2017Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 114, s. 141-151Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The performance of carbon nitride (CN) coated roller bearings is investigated, using a micropitting rig. The rolling performance is evaluated using Stribeck test, with a continuously varying rolling speed (0.2 - 2 m/s). Rolling contact fatigue tests with constant speeds (0.5, 1, 2, and 3.5 m/s) are also conducted in order to study the high-cycle performance of the rollers. The obtained Stribeck curve shows that the presence of coatings eliminates run-in, resulting in low friction coefficients (similar to 0.08). Raman spectroscopy, performed at the wear tracks, reveals that CNx maintain stable chemical state. Coatings show abrasion although the wear rate is not detrimental for the performance of the rollers, since a CNx to-steel contact is retained during the entire rolling contact fatigue test.

  • 19.
    Bakoglidis, Konstantinos
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Nedelcu, Ileana
    SKF Engn and Research Centre, Netherlands.
    Schmidt, Susann
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Greczynski, Grzegorz
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Ehret, Pascal
    SKF Engn and Research Centre, Netherlands.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rolling contact fatigue of bearing components coated with carbon nitride thin films2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 98, s. 100-107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bearing rollers were coated with CNx films using high power impulse magnetron sputtering deposition in order to reduce their rolling-contact fatigue as investigated using a Micro-Pitting Rig tribometer under poly-alpha-olefin lubricated conditions. Coated rollers with a similar to 15 nm thick W adhesion layer to the substrate, exhibit the best performance, presenting mild wear and no fatigue after 700 kcycles. The steady-state friction coefficient was similar to 0.05 for both uncoated and coated rollers. Uncoated rollers show run-in friction in the first 50 kcycles, because of steel-to-steel contact, which is absent for coated rollers. Analytical transmission electron microscopy and X-ray photoelectron spectroscopy show that the presence of a CNx coating prevents steel-to-steel contact of the counterparts, prior to the elastohydrodynamic lubrication, reducing their wear and increasing the lifetime expectancy. (C) 2016 Elsevier Ltd. All rights reserved.

  • 20.
    Bejjani, Roland
    et al.
    Sandvik Coromant Västberga.
    Marianne, Collin
    Sandvik Coromant Västberga.
    Thersleff, Thomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Stina, Odelros
    Sandvik Coromant Västberga.
    Multi-scale study of initial tool wear on textured alumina coating, and the effect of inclusions in low-alloyed steel2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 100, s. 204-212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When turning low-alloyed steel with hard inclusions, scores and grooves have been observed in the wear of the alumina coating in CVD coated cutting tools. This study focuses on detailed understanding of flank wear in the textured alumina coating and the relation to the workpiece's inclusions. For chip formation studies, a quick stop device has been used. A topography analysis for the worn coating was performed in the micro scale. Studies at lower scales were performed using TEM. This allowed the study of wear on the coating crystalline structure and the embedment of workpiece material on its surface. Based on the results, the mechanism behind the initial wear was analyzed and an abrasion wear model is proposed.

  • 21.
    Bergseth, Ellen
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Sjöberg, Sören
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Björklund, Stefan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Influence of real surface topography on the contact area ratio in differently manufactured spur gears2012Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 56, s. 72-80Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 22.
    Björklund, Stefan
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    The influence of surface roughness in elliptical contacts2001Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 34, nr 12, s. 841-845Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 23.
    Björling, Marcus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Habchi, W.
    Lebanese American University, Department of Industrial and Mechanical Engineering, Byblos.
    Bair, S.
    G.W. Woodruff School of Mechanical Engineering, Centre for High Pressure Rheology, Georgia Institute of Technology, Atlanta.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Corrigendum to “Towards the true prediction of EHL friction” [tribol. Int. 66 (2013) 19–26]2019Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 133, s. 297-297Artikkel i tidsskrift (Annet vitenskapelig)
  • 24.
    Björling, Marcus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Habchi, W.
    Lebanese American University, Department of Industrial and Mechanical Engineering, Byblos.
    Bair, S.
    G.W. Woodruff School of Mechanical Engineering, Centre for High Pressure Rheology, Georgia Institute of Technology, Atlanta.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Towards the true prediction of EHL friction2013Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 66, s. 19-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The capability to predict elastohydrodynamic film-thickness and friction from primary measurements of transport properties of liquid has been an elusive goal for tribologists for 50 years. Most comparisons between predictions and experiments involve some amount of tuning of the model in order to match the experimental results. In true prediction, this cannot be done since there are normally no experimental results to compare to. Primary measurements of lubricant transport properties of Squalane were performed, and used in a numerical friction prediction model. Afterwards, friction was measured in a ball-on-disc tribotester. No tuning of the lubricant properties, model or test setup were applied. The current work on EHL-friction is therefore a true representation of the current level of EHL-friction prediction.

    Fulltekst (pdf)
    fulltext
  • 25.
    Björling, Marcus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Miettinen, J.
    Group of Tribology and Machine Elements, Department of Materials Science, Tampere University of Technology.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lehtovaara, A.
    Group of Tribology and Machine Elements, Department of Materials Science, Tampere University of Technology.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    The correlation between gear contact friction and ball on disc friction measurements2015Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 83, s. 114-119Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Running experiments with full-size gearboxes from the actual application has the advantage of giving realistic results in terms of power losses. The drawback is extensive costs, lengthy testing, and the difficulty in differentiating between load dependent and load independent losses, and which losses are coming from the gears, seals, bearings or synchronizers. In this work, the correlation between friction measurements conducted in a ball-on-disc machine and friction measurements conducted in a back-to-back gear rig is investigated. The correlation between the gear tests and the ball-on-disc tests were reasonably good in terms of absolute values, and the shape of the friction curves were similar, indicating that the ball-on-disc measurements to a large extent are capturing the behavior of the gear contact

    Fulltekst (pdf)
    fulltext
  • 26. Boschkova, K
    et al.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Rutland, M
    YKI – Ytkemiska institutet.
    Imae, T
    Study of thin surfactant films under shear using the tribological surface force apparatus2001Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 34, s. 815-822Artikkel i tidsskrift (Fagfellevurdert)
    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 Å thickness at each mica surface, indicating that the surfactant adsorbs in a flat conformation. Furthermore, the height of the force barrier at approximately 60Å 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 Å, 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 Å). 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

  • 27. Boschkova, K.
    et al.
    Kronberg, B.
    Rutland, Mark W
    KTH, Tidigare Institutioner                               , Kemi.
    Imae, T.
    Study of thin surfactant films under shear using the tribological surface force apparatus2001Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 34, nr 12, s. 815-822Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 28.
    Cadario, Alessandro
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Alfredsson, Bo
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Fretting fatigue experiments and analyses with a spherical contact in combination with constant bulk stress2006Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 39, nr 10, s. 1248-1254Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 29.
    Cha, Matthew
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.). Waukesha Bearings, United Kingdom .
    Glavatskih, Sergei
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.). Ghent University, Belgium .
    Nonlinear dynamic behaviour of vertical and horizontal rotors in compliant liner tilting pad journal bearings: Some design considerations2015Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 82, s. 142-152Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 30.
    Cha, Matthew
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Isaksson, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Glavatskih, Sergei
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Influence of pad compliance on nonlinear dynamic characteristics of tilting pad journal bearings2013Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 57, s. 46-53Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 31.
    Cha, Matthew
    et al.
    Kungliga tekniska högskolan, KTH.
    Isaksson, Patrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Glavatskih, Sergei
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of pad compliance on nonlinear dynamic characteristics of tilting pad journal bearings2013Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 57, s. 46-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of padcompliance on the dynamic response of tiltingpadjournalbearings is investigated. Padcompliance 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.

  • 32.
    Cousseau, T.
    et al.
    INEGI, Universidade do Porto.
    Björling, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Graça, B.
    INEGI, Universidade do Porto.
    Campos, A.
    ISEP, Instituto Superior de Engenharia do Porto.
    Seabra, J.
    FEUP, Universidade do Porto.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Film thickness in a ball-on-disc contact lubricated with greases, bleed oils and base oils2012Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 53, s. 53-60Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three different lubricating greases and their bleed and base oils were compared in terms of film thickness in a ball-on-disc test rig through optical interferometry. The theoretical values calculated according to Hamrock's equation are in close agreement with the base oil film thickness measurements, which validates the selected experimental methodology.The grease and bleed oil film thickness under fully flooded lubrication conditions presented quite similar behaviour and levels. Therefore, the grease film thickness under full film conditions might be predicted using their bleed oil properties, namely the viscosity and pressure-viscosity coefficient. The base and bleed oil lubricant parameter LP are proportional to the measured film thickness.A relationship between grease and the corresponding bleed oil film thickness was evidenced

  • 33. Cupillard, Samuel
    et al.
    Glavatskih, Sergei
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    3D thermohydrodynamic analysis of a textured slider2009Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 42, nr 10, s. 1487-1495Artikkel i tidsskrift (Fagfellevurdert)
    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).

  • 34. Cupillard, Samuel
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Cervantes, Michel
    3D thermohydrodynamic analysis of a textured slider2009Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 42, nr 10, s. 1487-1495Artikkel i tidsskrift (Fagfellevurdert)
    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).

  • 35.
    Das, Sanjeev
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Effect of static and dynamic ageing on wear and friction behavior of aluminum 6082 alloy2013Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 60, s. 1-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present investigation the effect of static and dynamic ageing on the wear and friction behavior of aluminum alloy (AA 6082) sliding against tool steel (TS) surface has been studied. The AA 6082 alloy samples used in the present study were in as-cast, solutionized and peak aged conditions. Scanning electron microscope analysis of the debris and worn surfaces revealed the role of precipitates on the dry sliding wear behavior. Frictional behavior varies significantly for all the conditions at elevated temperature (180 °C) compared to room temperature (40 °C). Such response was attributed to the dynamic precipitations during elevated temperature test.

  • 36.
    Dimkovski, Zlate
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, Maskinteknisk produktframtagning (MTEK), Funktionella ytor.
    Tomanik, Eduardo
    MAHLE Metal Leve, Jundiai, Sao Paulo, Brazil.
    Profito, Francisco
    University of Sao Paulo, Sao Paulo, Brazil.
    Influence of measurement and filtering type on friction predictions between cylinder liner and oil control ring2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 100, s. 7-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is of a vital importance to reduce the frictional losses in the engines and hence the fuel/energy consumption. The major contributors to this are the oil control ring and cylinder liner interactions difficult to understand when comparing the experimental and theoretical results. The latter largely depend on the liner surface measurement and filtering type used in the simulations. Therefore, low-pass and high-pass filtrations were applied and the friction behaviors between the filtered liner surfaces and a perfectly flat ring surface were simulated for different engine speeds. The surfaces low-pass filtered by lower cutoffs showed higher friction, while the type of de-noising revealed about two and a half times higher friction. Stylus surfaces showed larger friction than the interference ones. © 2015 Elsevier Ltd. All rights reserved.

  • 37.
    Duvefelt, K.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Olofsson, U.
    KTH Royal Institute of Technology, Sweden.
    Johannesson, C. M.
    KTH Royal Institute of Technology, Sweden.
    Skedung, Lisa
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Model for contact between finger and sinusoidal plane to evaluate adhesion and deformation component of friction2014Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, s. 389-394Artikkel i tidsskrift (Fagfellevurdert)
    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 frictionmeasurements on fine controlled surfaces. These surfaces were sinusoidal with wavelengths from 0.27 to 8.8 μm and amplitudes from 0.007 to 6 μm. 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.

  • 38.
    Duvefelt, Kenneth
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Johannesson, Carl Michael
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Skedung, Lisa
    Model for contact between finger and sinusoidal plane to evaluate adhesion and deformation component of friction2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 96, s. 389-394Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 39.
    Duvefelt, Kenneth
    et al.
    KTH Royal Institute of Technology, Sweden.
    Olofsson, Ulf
    KTH Royal Institute of Technology, Sweden.
    Johannesson, Carl Michael
    KTH Royal Institute of Technology, Sweden.
    Skedung, Lisa
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Model for contact between finger and sinusoidal plane to evaluate adhesion and deformation component of friction2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 96, s. 389-394Artikkel i tidsskrift (Fagfellevurdert)
    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 μm and amplitudes from 0.007 to 6 μm. 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.

  • 40.
    Everitt, Carl-Magnus
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Alfredsson, Bo
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Contact fatigue initiation and tensile surface stresses at a point asperity which passes an elastohydrodynamic contact2018Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 123, s. 234-255Artikkel i tidsskrift (Annet vitenskapelig)
    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.

    Fulltekst (pdf)
    fulltext
  • 41.
    Everitt, Carl-Magnus
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Alfredsson, Bo
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Surface initiation of rolling contact fatigue at asperities considering slip, shear limit and thermal elastohydrodynamic lubrication2019Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 137, s. 76-93Artikkel i tidsskrift (Fagfellevurdert)
    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.

    Fulltekst (pdf)
    Surface initiation of rolling contact fatigue
  • 42. Fatima, Nowshir
    et al.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Berglund, Kim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of water on the tribological properties of zinc dialkyl-dithiophosphate and over-based calcium sulfonate additives in wet clutch contacts2015Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 87, s. 113-120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Usually the wet clutch lubricant properties vary with different formulations of base oil types and additives. The aim of this paper was to evaluate the effect of water on the performance of additives in ATF. Simplified lubricants, ZDDP and over-based Ca-sulfonates detergent additives in an API Group I mineral base oil, were employed to compare with the commercial fully-formulated automatic transmission fluid (DEXRON®VI) during water-contamination. A full-scale wet clutch test rig was used to evaluate the frictional response due to water contamination of the lubricants. Fourier Transform Infrared Spectroscopy was utilized to evaluate the variation in the solubility of these polar organic additives in the water phase and Karl-Fischer titration was utilized to evaluate the post-test water content for different formulations.

  • 43. Fatima, Nowshir
    et al.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Surface chemistry of wet clutch influenced by water contamination in automatic transmission fluids2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 96, s. 395-401Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lubricated friction interfaces used for wet clutches produces different friction behaviour depending on the lubricant conditions. Usually the lubricant conditions vary for water contamination in automatic transmission fluid (ATF). The presence of water retards the ATF performance by increasing the friction and can influence the deterioration of the clutch plates. Water as a polar contaminant can change the absorbability of the surface active additives, which might cause the characteristic friction behaviour. The aim of this paper is to verify the surface chemistry of tribotested standard friction interfaces lubricated with water contaminated commercial ATF (DEXRON® VI). The evidences of the influence of water on ATF performances were shown by surface analyses

  • 44.
    Fillon, M.
    et al.
    University of Poitiers.
    Glavatskih, Sergei
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    PTFE-faced centre pivot thrust pad bearings: factors affecting TEHD performance2008Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, nr 12, s. 1219-1225Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 45. Fillon, M.
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    PTFE-faced centre pivot thrust pad bearings factors affecting TEHD performance2008Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, nr 12, s. 1219-1225Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 46.
    Flores-Ruiz, F. J.
    et al.
    CONACYT-Instituto de Física, Benemérita Universidad Autónoma de Puebla, Apdo. Post. J-48, Puebla, Pue, Mexico.
    Tucker, Mark
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Bakoglidis, Konstantinos
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. School of Materials, Faculty of Science and Engineering, The University of Manchester, Manchester, United Kingdom.
    Yu, X.
    Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA.
    Gellman, A. J.
    Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA.
    Herrera-Gomez, A.
    CINVESTAV-Unidad Queretaro, Queretaro, Qro, Mexico.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Broitman, Esteban
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. SKF Research & Technology Development Center, Nieuwegein, Netherlands.
    Micro-tribological performance of fullerene-like carbon and carbon-nitride surfaces2018Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 128, s. 104-112Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We studied the microtribological behavior of amorphous and fullerene-like (FL) carbon and carbon-nitride coatings deposited by filtered-cathodic-arc. All films show similar friction coefficients but different wear mechanisms. The FL films exhibit a surface swelling with the formation of a layer that thickens during the test, limiting wear and maintaining a low friction. X-ray photoelectron spectroscopy on worn FL film surfaces show an increase in the sp(2)-content, indicating that the lubricious layer generated by the wear process is probably the result of re-hybridization due to plasticity induced by localized shear. In contrast, the wear results of the amorphous films, involving tribomechanical and tribochemical surface phenomena, show that the surface layer formed during sliding is a precursor to the onset of wear.

  • 47.
    Forsberg, Peter
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Debord, Dominique
    Scania CV AB.
    Jacobson, Staffan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Quantification of Combustion Valve Sealing Interface Sliding - A Novel Experimental Technique and Simulations2014Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, s. 150-155Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The rapid sharpening of the environmental legislation during the last decades has forced engine manufacturers to radical design modifications. It has been shown that the sliding in the sealing interface is one of the major reasons for wear. The sliding wear is expected to have an even more important role in modern engines. This paper presents unique experimental data, acquired using a dedicated technique in a test-rig. The experimental data is complemented by FEM-simulations. The simulations involve validation of the test-rig valve sealing interface sliding behaviour and investigations on how different parameters influence the sliding length. These parameters include combustion pressure, contact angle, contact length, valve head thickness, coefficient of friction, running-in wear, and change of elastic modulus due to temperature variations.

  • 48.
    Forsberg, Peter
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Elo, Robin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Jacobson, Staffan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    The importance of oil and particle flow for exhaust valve wear - An experimental study2014Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, s. 176-183Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oil residue particles have a large impact in protecting the sealing surfaces of heavy duty exhaust valves. To increase the understanding of the mechanism behind this, the wear behavior of exhaust valves subjected to a flow of hot air with controlled amounts of oil particles of three different compositions has been investigated. Air flow without addition of oil was used as a reference. The degree and mechanisms of surface damage proved to be sensitive to the test parameters. Residues from the oils containing additives proved to form protective tribofilms, while the oil without additives promoted agglomeration of wear debris on the sealing surfaces. The dry reference showed severe wear with debris scattered over the surfaces.

  • 49. Furustig, Joel
    et al.
    Almqvist, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Bates, C.A.
    Danfoss Power Solutions ApS, Nordborg.
    Ennermark, P.
    Danfoss Power Solutions ApS, Nordborg.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    A two scale mixed lubrication wearing-in model, applied to hydraulic motors2015Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 90, s. 248-256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wearing-in of a machine component can increase the conformity between contacting pairs and smoothen the surface topography. A two scale model, combining the wearing-in effects, resulting in changes in the surface topography, with the wear that occurs on the component, is presented. The geometry of the components are represented with measured coordinates. Wear leads to changes of the geometry, which has an effect on several tribological conditions, such as contact forces, relative velocities and conformity. Due to the wear on the topography scale, the load sharing is also affected. The model is applied to orbital hydraulic motors. The wear depth predicted with the model, is qualitatively in good agreement with the wear depth recorded in experiments.

  • 50.
    Gaard, Anders
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Influence of tool microstructure on galling resistance2013Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 57, s. 251-256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In sheet metal forming, different types of tool steels are used depending on sheet quality. In the present work, influence of amount, and type, of primary carbides and carbo-nitrides was investigated regarding tool galling resistance against austenitic stainless steel. A significant impact of amount of carbides on galling resistance was observed and tool performance was improved as volume fraction increased. However, no influence of carbide type was distinguished. Alloying by nitrogen further improved the galling resistance and best tool performance was observed for a tool steel comprising only carbo-nitride M(C,N) particles. Besides transfer of sheet material, several other tool damage mechanisms were observed such as cracking, micro-chipping and abrasive scratching. (C) 2012 Elsevier Ltd. All rights reserved.

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