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  • 1.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    A first attempt of true prediction of EHL friction2013Conference paper (Refereed)
  • 2.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction in elasto hydrodynamically lubricated contacts: the influence of speed and slide to roll ratio2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Reducing losses in transmissions has become a high priority in the automotive market during recent years, mainly due to environmental concerns leading to regulations placed on the automotive industry to drive the development of vehicles with lower fuel consumption and CO2 emissions. Rising fuel prices and increasing environmental concerns have also made customers more prone to purchase more fuel efficient vehicles. In addition to the fuel savings that could be achieved by increased efficiency of transmissions there are other benefits as well. A more efficient transmission will in general generate less heat, and experience less wear. This will lead to fewer failures, longer service life of components, and possibly longer service intervals. Furthermore this implies a possibility to reduce coolant components, thus reducing the total weight of the system, leading to a further decrease in consumption and a lower impact on the environment due to a reduction of material usage. A low weight design is also beneficial for vehicle dynamics and handling. In addition to the automotive market, gears are extensively used in many other fields, such as wind power and industry. In some cases a substantial part of the losses in a gear transmission is attributed to gear contact friction due to sliding and rolling between the gear teeth. To better understand the contact friction phenomena in gears an experimental apparatus capable of running under similar conditions to gears is chosen. By using a ball on disc test device the contact friction can be measured in a broad range of speeds and slide to roll ratios (SRR). The results are presented as a 3D friction map which can be divided into four different regions; Linear, Non-linear, mixed and thermal. In each of these regions different mechanisms are influencing the coefficient of friction. Several tests have been conducted with different lubricants, EP- additive packages, operating temperatures, surface roughness and coatings. The method gives a good overview, a system fingerprint, of the frictional behaviour for a specific system in a broad operating range. By observing results for different systems, it is possible to identify how different changes will influence the coefficient of friction in different regimes, and therefore optimize the system depending on operating conditions. Among other things the tests have shown that reducing base oil viscosity increases contact friction in most operating conditions, introducing an earlier transition from full film to mixed lubrication, and increasing full film friction in many cases with high sliding speeds. An increase in operating temperature could both increase, and decrease the coefficient of friction depending on running conditions. Introducing smoother surfaces reduces the coefficient of friction at lower entrainment speeds since thinner lubricant films are required to avoid asperity collitions. By applying a DLC coating on one or both surfaces in a EHL contact, the friction coefficient is shown to decrease, even in the full film regime.

  • 3.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction in Elastohydrodynamic Lubrication2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today, with increasing demands on industry to reduce energy consumption and emissions, the strive to increase the efficiency of machine components is maybe bigger than ever. This PhD thesis focus on friction in elastohydrodynamic lubrication (EHL), found in, among others, gears, bearings and cam followers. Friction in such contacts is governed by a complex interaction of material, surface and lubricant parameters as well as operating conditions. In this work, experimental studies have been conducted that show how friction varies over a wide range of running conditions when changing parameters like lubricant viscosity, base oil type, surface roughness and lubricant temperature. These measurements have also been used to predict the friction behaviour in a real gear application. Numerical modeling of elastohydrodynamic (EHD) friction and film thickness are important for increased understanding of the field of EHL. Due to the high pressure and shear normally found in EHD contacts it is crucial that appropriate rheological models are used. An investigation has been carried out in order to assess the friction prediction capabilities of some of the most well founded rheological models. A numerical model was used to predict friction coefficients through the use of lubricant transport properties. Experiments were then performed that matches the predicted results rather well, and the deviations are discussed. The numerical model in combination with experimental measurements are used to investigate the friction reducing effect of diamond like carbon (DLC) coatings in EHL. A new mechanism of friction reduction through thermal insulation is proposed as an alternative to the current hypothesis of solid-liquid slip. These findings opens up for new families of coatings where thermal properties are in focus that may be both cheaper, and more effective in reducing friction in certain applications than DLC coatings of today.

  • 4.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glycerol and Diamond-Like-Carbon in Elastohydrodynamic Lubrication2018Conference paper (Refereed)
  • 5.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Bair, Scott
    Georgia Institute of Technology, Centre for High Pressure Rheology, G.W. Woodruff School of Mechanical Engineering, Atlanta, GA.
    Mu, Liwen
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Zhu, Jiahua
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Elastohydrodynamic performance of a bio-based, non-corrosive ionic liquid2017In: Applied Sciences: APPS, ISSN 1454-5101, E-ISSN 1454-5101, Vol. 17, no 10, article id 996Article in journal (Refereed)
    Abstract [en]

    To improve performance of machine components, lubrication is one of the most important factors. Especially for use in extreme environments, researchers look for other solutions rather than common lubricant base stocks like mineral oils or vegetable oils. One such example is ionic liquids. Ionic liquids have been defined as molten salts with melting points below 100 °C that are entirely ionic in nature, comprising both cationic and anionic species. The industrial use of ionic liquids is mostly as solvents, electrolytes, extractants and catalysts. In tribological applications, ionic liquids are mainly studied in boundary lubrication and in pure sliding contacts. In this work, the elastohydrodynamic performance of a bio-based, non-corrosive, [choline][L-proline] ionic liquid is evaluated in terms of pressure-viscosity response, film forming capability and friction. The results show a pressure-viscosity coefficient of below 8 GPa-1 at 25 °C, among the lowest reported for any ionic liquid. The ionic liquid generated up to 70% lower friction than a reference paraffin oil with a calculated difference in film thickness of 11%. It was also shown that this ionic liquid is very hygroscopic, which is believed to explain part of the low friction results, but also has to be considered in practical applications since the water content will influence the properties and thus the performance of the lubricant.

  • 6.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Bair, Scott
    Georgia Institute of Technology, Centre for High Pressure Rheology, G.W. Woodruff School of Mechanical Engineering, Atlanta, GA 30332-0405, USA;.
    Mu, Liwen
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325, USA;.
    Zhu, Jiahua
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325, USA;.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Elastohydrodynamic Performance of a Non-Corrosive Non-Protic Ionic Liquid2017Conference paper (Refereed)
    Abstract [en]

    Ionic liquids have been defined as molten salts with melting points below 100 degrees C that are entirely ionic in nature, comprising both cationic and anionic species. The industrial use of ionic liquids is mostly as solvents, electrolytes, extractants and catalysts. In tribological applications, Ionic liquids are mainly studied in boundary lubrication and in pure sliding contacts. In this work, the elastohydrodynamic performance of a non-corrosive, non-protonic ionic liquid is studied to assess the feasibility to use this kind of ionic liquid in machine components such as gears, rolling bearings and cam followers. This study includes ball on disc friction experiments in rolling sliding full film elastohydrodynamic lubrication at high slide to roll ratios, as well as film thickness measurements with optical interferometry. A commercially available paraffin oil has been used as a reference.

  • 7.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Andrew, Spencer
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The effect of oil ageing on friction in elastohydrodynamic lubrication2018Conference paper (Refereed)
  • 8.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Spencer, Andrew
    Dynamics, Acoustics and Tribology, Engine Dynamics, Scania, Scania Technical Centre.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The effect of ageing on elastohydrodynamic friction in heavy-duty diesel engine oils2017In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 231, no 6, p. 708-715Article in journal (Refereed)
    Abstract [en]

    To further improve the efficiency of machine components found in automotive engine systems it is important to understand the friction generation in these components. Modelling and simulation of these components are crucial parts of the development process. Accurate simulation of the friction generated in these machine components is, amongst other things, dependent on realistic lubricant rheology and lubricant properties, where especially the latter may change during ageing of the lubricant. Many modern heavy-duty diesel engines are in operation for several hundred hours before the engine oil is changed. In this work, two engine oils, one 10 W-30 and one 5 W-20, have been aged in full heavy-duty diesel engine bench tests for 400 and 470 hours respectively. This roughly corresponds to the amount of ageing these oils are subjected to between oil drains in field conditions. The aged oils were subjected to a number of oil analyses showing, among other things, a maximum increase in oil viscosity of 12.9% for the 5 W-20 oil and 5.5% for the 10 W-30 oil, which is most likely primarily an effect of evaporation and oxidation. The aged oils were tested in a ball-on-disc test rig under elastohydrodynamic conditions where friction was measured and the performance was compared to fresh samples of the same oils. The results show that there is almost no difference in elastohydrodynamic friction when comparing the aged oils with the fresh oils. These results indicate that it is not necessary to include oil ageing in numerical elastohydrodynamic friction models as long as the oil is changed before the ageing has reached a critical level

  • 9.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Spencer, Andrew
    Scania.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The effect of oil ageing on friction in elastohydrodynamic lubrication2018Conference paper (Refereed)
    Abstract [en]

    Numerical modeling of friction in elastohydrodynamically lubricated contacts are of high importance in the development of various types of machine elements such as gears, rolling element bearings and cam followers. The friction generated in the machine elements of a system does not only affect efficiency, but also the dynamics and overall function. Accurate simulation of the friction generated in machine components is, among other things dependent on realistic lubricant properties, which may change during ageing of the lubricant. Many modern machines are in operation for several hundred ours before the oil is changed. In this work, two engine oils, one 10W-30 and one 5W-20, have been aged in full heavy-duty diesel engine bench tests for a duration comparable to the amount of ageing these oils are subjected to between oil drains in field conditions. The aged oils were subjected to several analyses showing, among other things, a maximum increase in viscosity, and a reduction in some additives. Fresh and aged oils were tested in a ball-on-disc test rig under elastohydrodynamic conditions where friction was measured. The results showed almost no difference in elastohydrodynamic friction between the fresh and the aged oils.

  • 10.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    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 University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Erratum: Towards the true prediction of EHL friction2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 133, p. 297-297Article in journal (Refereed)
  • 11.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    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 University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Towards the true prediction of EHL friction2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 66, p. 19-26Article in journal (Refereed)
    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.

  • 12.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Habchi, Wassim
    Department of Industrial and Mechanical Engineering, Lebanese American University, Byblos.
    Bair, Scott
    Georgia Institute of Technology, Centre for High Pressure Rheology, G.W. Woodruff School of Mechanical Engineering, Atlanta.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Correction to: Friction reduction in elastohydrodynamic contacts by thin-layer thermal insulation2018In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, no 4, p. 1-1Article in journal (Refereed)
    Abstract [en]

    The original version of this article unfortunately contained a mistake. The correct information is given below. [ABSTRACT FROM AUTHOR]  Copyright of Tribology Letters is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

  • 13.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Habchi, Wassim
    Department of Industrial and Mechanical Engineering, Lebanese American University, Byblos, Lebanese American University, Department of Industrial and Mechanical Engineering, Byblos.
    Bair, Scott
    G.W. Woodruff School of Mechanical Engineering, Centre for High Pressure Rheology, Georgia Institute of Technology, Atlanta.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction reduction by thin-layer thermal insulation in elastohydrodynamic contacts2016Conference paper (Refereed)
  • 14.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Habchi, Wassim
    Department of Industrial and Mechanical Engineering, Lebanese American University, Byblos.
    Bair, Scott
    Georgia Institute of Technology, Centre for High Pressure Rheology, G.W. Woodruff School of Mechanical Engineering, Atlanta.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction reduction in elastohydrodynamic contacts by thin-layer thermal insulation2014In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 53, no 2, p. 477-486Article in journal (Refereed)
    Abstract [en]

    Reducing friction is of utmost importance to improve efficiency and lifetime of many products used in our daily lives. Thin hard coatings like diamond-like carbon (DLC) have been shown to reduce friction in full-film-lubricated contacts. In this work, it is shown that contrarily to common belief, the friction reduction stems mainly from a thermal phenomenon and not only a chemical/surface interaction one. It is shown that a few micrometer-thin DLC coating can significantly influence the thermal behavior in a lubricated mechanical system. The presented simulations, validated by experiments, show that applying a thin DLC coating to metal surfaces creates an insulating effect that due to the increased liquid lubricant film temperature at the center of the contact, locally reduces lubricant viscosity and thus friction. The results of the investigation show that the addition of thin insulating layers could lead to substantial performance increases in many applications. On a component level, the contact friction coefficient in some common machine components like gears, rolling element bearings, and cam followers can potentially be reduced by more than 40 %. This will most likely open up the way to new families of coatings with a focus on thermal properties that may be both cheaper and more suitable in certain applications than DLC coatings

  • 15.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Habchi, Wassim
    Lebanese American University, Department of Industrial and Mechanical Engineering, Byblos.
    Bair, Scott
    G.W. Woodruff School of Mechanical Engineering, Centre for High Pressure Rheology, Georgia Institute of Technology, Atlanta.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Towards the true prediction of EHL friction2013Conference paper (Refereed)
  • 16.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Habchi, Wassim
    Bair, Scott
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Warm carbon coat reduces friction2014In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 505, no 7483, p. 264-Article in journal (Other academic)
    Abstract [en]

    A coating material made of carbon reduces friction not just by providing a slippery surface, but also by keeping the points of contact warm. Marcus Björling at Luleå University of Technology in Sweden and his team coated steel balls with ``diamond-like-carbon'' - a material in which carbon atoms have a bonding pattern similar to that of diamond. They rolled the balls against a metal disk with an oil lubricant in between, and showed that the carbon coating acts as an insulator, lowering the viscosity of the lubricant and thus reducing the fricion between the ball and the disk. These findings could encourage the development of lubricant coatings made from insulating materials

  • 17.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Isaksson, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The influence of DLC coating on EHL friction coefficient2012In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 47, no 2, p. 285-294Article in journal (Refereed)
    Abstract [en]

    High hardness, high elastic modulus, low friction characteristics, high wear and corrosion resistance, chemical inertness, and thermal stability are factors that make diamond-like carbon (DLC) coatings the subject of many studies. For the same reasons they also seem suitable for use in, amongst others, machine components and cutting tools. While most studies in the literature focus on the influence of coatings on wear and friction in boundary lubrication and pure sliding contacts, few studies can be found concerning rolling and sliding elastohydrodynamic lubrication (EHL) friction, especially in the mixed and full film regime. In this article tests are carried out in a Wedeven Associates Machine tribotester where an uncoated ball and disc pair is compared to the case of coated ball against uncoated disc, coated disc against uncoated ball, and coated disc against coated ball. The tests are conducted at two different temperatures and over a broad range of slide-to-roll ratios and entrainment speeds. The results are presented as friction maps as introduced in previous work (Björling et al. in J Eng Tribol 225(7):671, 2011). Furthermore a numerical simulation model is developed to investigate if there is a possibility that the hard, thin DLC coating is affecting the friction coefficient in an EHL contact due to thermal effects caused by the different thermal properties of the coating compared to the substrate. The experimental results show a reduction in friction coefficient in the full film regime when DLC-coated surfaces are used. The biggest reduction is found when both surfaces are coated, followed by the case when either ball or disc is coated. The thermal simulation model shows a substantial increase of the lubricant film temperature compared to uncoated surfaces when both surfaces are coated with DLC. The reduction in friction coefficient when coating either only the ball or the disc are almost the same, lower than when coating both the surfaces but still higher than the uncoated case. The findings above indicate that it is reasonable to conclude that thermal effects are a likely cause for the decrease in coefficient of friction when operating under full film conditions, and in the mixed lubrication regime when DLC-coated surfaces are used

  • 18.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The effect of DLC coating thickness on elstohydrodynamic friction2014In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 55, no 2, p. 353-362Article in journal (Refereed)
    Abstract [en]

    The application of surface coatings has been shown to reduce friction in elastohydrodynamic lubrication (EHL), not only in the mixed and boundary regime when asperity interactions occur, but also in the full film regime. Several studies suggest that the full film friction reduction is due to a violation of the no-slip boundary condition and thus slip is taking place between the solid and the liquid. Another hypothesis proposes that the full film friction reduction is due to the low thermal conductivity of diamond-like carbon (DLC) coatings. In this work, two DLC coatings with the same composition, but different thicknesses, are investigated with uncoated steel specimens as a reference, all with the same surface roughness. Friction tests in a ball-on-disk machine show that both coatings reduce friction compared to the uncoated reference case in full film EHL. The thicker coating is significantly more effective at reducing friction than the thinner one at a maximum friction reduction of 41 % compared to 29 % for the thinner coating. Moreover, contact angle measurements, surface energy measurements, and spreading parameter calculations show no statistically significant differences between the two coatings, suggesting that the friction reduction capabilities of coatings in full film EHL cannot be described by solid-liquid interactions alone. The difference in friction reduction between the specimens in this work is mainly attributed to different thermal properties.

  • 19. Björling, Marcus
    et al.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Kassfeldt, Elisabet
    EHL friction mapping: the influence of lubricant, roughness, speed and slide to roll ratio2010In: 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010, Luleå: Luleå tekniska universitet, 2010Conference paper (Refereed)
    Abstract [en]

    A friction test is conducted in a WAM ball on disc test rig. The output from the test is friction coefficient versus entrainment speed and slide-to-roll ratio presented as a 3D friction map. A number of parameters are varied while studying the friction coefficient; surface roughness, base oil viscosity and EP additive package. Entrainment speed, slide to roll ratio and oil temperature are also varied. The results show that the mapping is efficient in showing the different types of friction that may occur in an EHL contact. The results also show that the friction behaviour can be strongly influenced by changing surface roughness as well as base oil viscosity, EP additive content and operating temperature.

  • 20.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Kassfeldt, Elisabet
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Elastohydrodynamic lubrication friction mapping: The influence of lubricant, roughness, speed, and slide-to-roll ratio2011In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 225, no 7, p. 671-681Article in journal (Refereed)
    Abstract [en]

    A friction test is conducted in a Wedeven Associates Machine ball-on-disc test rig. The output from the test, friction coefficient versus entrainment speed and slide-to-roll ratio (SRR), is presented as a three-dimensional friction map. A number of parameters are varied while studying the friction coefficient; surface roughness, base oil viscosity, base oil type, and extreme pressure (EP) additive package. Entrainment speed, SRR, and oil temperature are also varied. The results show that the mapping is efficient in showing the different types of friction that may occur in an elasto-hydrodynamic lubrication contact. The results also show that the friction behaviour can be strongly influenced by changing surface roughness as well as base oil viscosity, base oil type, EP additive content, and operating temperature.

  • 21.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    On the effect of DLC coating on full film EHL friction2013Conference paper (Refereed)
  • 22.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Miettinen, J.
    Group of Tribology and Machine Elements, Department of Materials Science, Tampere University of Technology.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lehtovaara, A.
    Group of Tribology and Machine Elements, Department of Materials Science, Tampere University of Technology.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The correlation between gear contact friction and ball on disc friction measurements2015In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 83, p. 114-119Article in journal (Refereed)
    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

  • 23.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Miettinen, Juha
    Group of Tribology and Machine Elements, Department of Materials Science, Tampere University of Technology.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lehtovaara, Arto
    Group of Tribology and Machine Elements, Department of Materials Science, Tampere University of Technology.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The correlation between gear contact friction and ball on disc friction measurements2016Conference paper (Refereed)
  • 24.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Sundararajan, Bharath
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Environmentally acceptable lubricants for marine applications2018Conference paper (Refereed)
  • 25.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    DLC and Glycerol: Superlubricity in Rolling/Sliding Elastohydrodynamic Lubrication2019In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 67, no 1, article id 23Article in journal (Refereed)
    Abstract [en]

    Low friction is one of the most important parameters for the development of machine components and machines with high efficiency. Many of the common machine components of today such as gears, rolling element bearings and cam-followers are defined by their non-conformal contacts leading to high-contact pressures, typically 1–4 GPa. The lubrication of such contacts is usually called elastohydrodynamic lubrication (EHL). Diamond-like carbon (DLC) coatings and glycerol have individually been shown to produce low friction in boundary, mixed and full film lubrication. A few studies have been conducted using both glycerol and DLC-coated surfaces to achieve even lower friction in pure sliding boundary-lubricated contacts. However, the literature is lacking studies of how the combination of glycerol and DLC performs in non-conformal rolling/sliding contacts where many common machine components operate. Such a study is presented in this article where a ball-on-disc test rig is used to investigate the performance of the combination of DLC and glycerol at pressures up to 1.95 GPa at various entrainment speeds and slide-to-roll ratios. The investigation shows that the DLC-glycerol combination provides very low friction values, in some cases, below the superlubricity threshold of 0.01, possibly shown for the first time at such high pressure in a non-conformal rolling/sliding contact. The low friction mechanism in full film lubrication is a combination of the low pressure-viscosity and high temperature-viscosity sensitivity of glycerol in combination with thermal insulation of the DLC coating and is presented as thermally assisted liquid superlubricity.

  • 26.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Yijun, Shi
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glycerol and Diamond-Like-Carbon in Elastohydrodynamic Lubrication2018Conference paper (Other academic)
    Abstract [en]

    Lubrication and surface engineering plays a vital part in the efficiency of machine components. By using low friction fluids and low friction coatings the efficiency of machine components can be improved dramatically. Glycerol is an example of a fluid with extraordinary low friction characteristics in various systems. Diamond like carbon (DLC) coatings have also been shown to reduce friction in a variety of tribological interfaces. In this study, the elastohydrodynamic performance of glycerol with DLC coated surfaces has been investigated in rolling sliding contacts at high pressures and high slide-to-roll ratios. The DLC-glycerol system is compared to a steel-synthetic oil system and the differences are significant.

  • 27.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Yijun, Shi
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glycerol and DLC in Elastohydrodynamic Lubrication2018Conference paper (Refereed)
    Abstract [en]

    Lubrication and surface engineering plays a vital part in the efficiency of machine components. By using low friction fluids and low friction coatings the efficiency of machine components can be improved dramatically. Glycerol is an example of a fluid with extraordinary low friction characteristics in various systems. Diamond like carbon (DLC) coatings have also been shown to reduce friction in a variety of tribological interfaces. In this study, the elastohydrodynamic performance of glycerol with DLC coated surfaces has been investigated in rolling sliding contacts at high pressures and high slide-to-roll ratios. The DLC-glycerol system is compared to a steel-synthetic oil system and the differences are significant.

  • 28.
    Björling, Marcus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Yijun, Shi
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glycerol and DLC in Elastohydrodynamic Lubrication2018Conference paper (Refereed)
    Abstract [en]

    Lubrication and surface engineering plays a vital part in the efficiency of machine components. By using low friction fluids and low friction coatings the efficiency of machine components can be improved dramatically. Glycerol is an example of a fluid with extraordinary low friction characteristics in various systems. Diamond like carbon (DLC) coatings have also been shown to reduce friction in a variety of tribological interfaces. In this study, the elastohydrodynamic performance of glycerol with DLC coated surfaces has been investigated in rolling sliding contacts at high pressures and high slide-to-roll ratios. The DLC-glycerol system is compared to a steel-synthetic oil system and the differences are significant.

  • 29.
    Cousseau, T.
    et al.
    INEGI, Universidade do Porto.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Graça, B.
    INEGI, Universidade do Porto.
    Campos, A.
    ISEP, Instituto Superior de Engenharia do Porto.
    Seabra, J.
    FEUP, Universidade do Porto.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Film thickness in a ball-on-disc contact lubricated with greases, bleed oils and base oils2012In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 53, p. 53-60Article in journal (Refereed)
    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

  • 30.
    Cousseau, Tiago
    et al.
    FEUP, Universidade do Porto.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Graça, Beatriz
    INEGI, Universidade do Porto.
    Campos, Armando
    ISEP, Instituto Superior de Engenharia do Porto.
    Seabra, Jorge
    FEUP, Universidade do Porto.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of grease bleed oil on ball-on-disc lubrication2013Conference paper (Refereed)
  • 31.
    Cousseau, Tiago
    et al.
    FEUP, Universidade do Porto, INEGI, Universidade do Porto.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Graça, Beatriz
    INEGI, Universidade do Porto.
    Campos, Armando
    ISEP, Instituto Superior de Engenharia do Porto.
    Seabra, Jorge
    FEUP, Universidade do Porto.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Film thickness and friction torque prediction of lubricant greases using bleed oil properties2012In: Film thickness and friction torque prediction of lubricant greases using bleed oil properties, 2012Conference paper (Refereed)
  • 32.
    Hansen, Jonny
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    How a small change in surface roughness dramatically changes the transition to full-film lubrication in EHL2019Conference paper (Refereed)
    Abstract [en]

    To improve the efficiency in non-conformal type of machine elements, it is of crucial importance to gain knowledge about the underlying mechanism that governs the formation of an elastohydrodynamic (EHD) oil film. This study was set out to explore the dependency of surface roughness and operating conditions on the transition to full film elastohydrodynamic lubrication (EHL). A ball-on-disc device, arranged for monitoring electrical contact resistance (ECR), was operated under a wide variety of heavily loaded rolling/sliding conditions. To reduce complexity in the film formation process, any tribo-chemical effects were minimized by the selection of a neat synthetic lubricant. Two types of tests were set-up to examine, in particularly, the role of load and slide-to-roll ratio (SRR) on the EHD film formation. In the first, the contact was mapped over the speed and SRR parameter space to capture the transition from EHL to mixed lubrication when starting in EHL. The contact was then operated under different loads to reveal the EHL transitions dependency to variations in Hertzian contact pressure. In the second set of tests, the contact was initiated in mixed lubrication, and film formation was monitored until surfaces achieved lift-off for EHL by adequate surface modification due to running-in. Subsequently, special emphasis was set out to investigate what transformations those surfaces had to undergo in order for EHL lift-off to take place.

  • 33.
    Hansen, Jonny
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Improved performance by ionic additives in hydrocarbon base fluids for mixed-rolling/sliding contacts2018Conference paper (Refereed)
  • 34.
    Hansen, Jonny
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Gear Technology, Transmission Development, Scania CV AB, Södertälje.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mapping of the lubrication regimes in rough surface EHL contacts2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 131, p. 637-651Article in journal (Refereed)
    Abstract [en]

    Understanding film formation in rough surface elastohydrodynamically lubricated (EHL) contacts have been an ongoing pursuit in lubrication science for more than half a century. This study furthers that quest by establishing a single combined friction and electrical contact resistance map that forms a clear and comprehensive overview of the lubrication performance. A ball-on-disc machine was operated under a wide variety of heavily loaded rolling/sliding contact conditions. Results show that while sweeping the contact over the SRR- and entrainment speed-domain, the primary sweep direction significantly affects running-in and consequently the transition from full-film to the mixed lubrication regime. Such knowledge sheds new light into the mechanisms that governs EHL film formation and the concurrent interplay with the mixed lubricated friction coefficient.

  • 35.
    Hansen, Jonny
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    On the full film to mixed lubrication transition in rolling/sliding Non-conformal Contacts2018Conference paper (Refereed)
  • 36.
    Hansen, Jonny
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    On the full film to mixed lubrication transition in rolling/sliding non-conformal contacts2018Conference paper (Refereed)
    Abstract [en]

    Lower weight components and thinner lubricating oils, with simultaneous improved power density, is an on-going pursuit in industry and lubrication science. The outcome is shifting the tribological performance towards more severe lubricating regimes. This in turn sets new levels of demands for knowledge about the complex and concurrent interaction between engineering surfaces and lubricants. An emerging need is therefore to make use of the enhancing properties of tribo-improvers, thus to gain knowledge of their working mechanism is consequently of uttermost importance. This study was set out to investigate the tribofilm formation induced by different degrees of surface roughness. A ball on disc device was operated under heavily loaded rolling/sliding conditions at elevated temperature to simulate gear like conditions. The tribological performance is ultimately evaluated in terms friction and wear with special emphasis on the development and mechanism of additive derived tribofilms.

  • 37.
    Hansen, Jonny
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    On the surface lift-off transition in rough surface EHL contacts2019Conference paper (Refereed)
    Abstract [en]

    The pumping and churning losses in transmission assemblies are minimized when gears are operated in low viscosity lubricants. Therefore, in order to improve gear efficiency, it is of crucial importance to gain knowledge about the underlying mechanism that governs elastohydrodynamic (EHL) contacts ability to form a separating oil film. This study was set out to explore the necessary requirements for EHL contacts to achieve a state of full film separation. A ball on disc device, arranged for electrical contact resistance (ECR) measurement, was operated under a wide variety of heavily loaded rolling/sliding conditions. Friction and ECR-signal were simultaneously monitored to capture the contact performance until surfaces achieved lift-off by adequate surface modification due to running-in. Special emphasis was set on post-test surface analysis to reveal whether any surface roughness parameter could provide insights in the pre-requisite for surface lift to take place.

  • 38.
    Hansen, Jonny
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Improved performance by ionic additives in hydrocarbon base fluids for mixed-rolling/sliding contacts2018Conference paper (Refereed)
  • 39.
    Hansen, Jonny
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Gear Technology, Transmission Development, Scania CV AB, Södertälje.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Performance and mechanisms of silicate tribofilm in heavily loaded rolling/sliding non-conformal contacts2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 123, p. 130-141Article in journal (Refereed)
    Abstract [en]

    Lubricant performance is vital as heavy-duty gear manufacturers increase power density in their efforts towards increased efficiency. In this work, a recently developed ionic liquid is introduced as a multifunction additive for use in hydrocarbon base fluid. A ball-on-disc tribological test machine was used to evaluate friction and wear in heavily loaded mixed rolling/sliding conditions. The novel multifunctional additive is benchmarked against conventional axle-gear oil additives, and results shows excellent tribological performance in terms of friction and wear. Post-test surface analysis of the wear scars revealed a silicate based tribofilm derived from the novel ionic additive, contrary to conventional phosphorous and/or sulfur based. The silicate tribofilm is correlated to a significantly increased wear resistance and vastly improved running-in performance.

  • 40.
    Hansen, Jonny
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Nyberg, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Elastohydrodynamic performance of a hydrocarbon mimicking ionic liquid additive2017Conference paper (Refereed)
    Abstract [en]

    Machine elements operating under lubricated conditions will eventually fail due to high stresses and fatigue-related causes. In order to find optimum protective measures, it is important to understand how the stresses arise and what factors that influence their magnitude. With the current shift for more sever lubricating regimes, the role of tribo-improvers is becoming vital. At this point, the interplay between the chemisorption mechanism of various lubricant compounds and surface failure is not yet fully understood. To obtain a better understanding of this, a newly developed ionic structured tribo-improving additive, based on silicon, was investigated and benchmarked against conventional heavy-duty gearbox additives. A ball on disc device was operated under heavily loaded rolling/sliding conditions, at elevated temperature to simulate gear like conditions, and lubricating performance was subsequently evaluated in terms of friction and wear. Such results highlight the importance of properly designed lubricants for optimal tribo-performance under rolling-sliding conditions

  • 41.
    Shi, Yijun
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Boundary and elastohydrodynamic lubrication studies of glycerol aqueous solutions as green lubricants2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 39-45Article in journal (Refereed)
    Abstract [en]

    In this paper, the boundary and elastohydrodynamic lubricating behaviour of glycerol and its aqueous solutions are discussed in both rolling and sliding contacts with a view on assessing the use of glycerol as a green lubricant. To understand the lubricating mechanism, the film thickness of glycerol and its aqueous solutions were studied at different velocities. The results show that the viscosity of glycerol can be controlled for a wide range by adding different amounts of water. The lubricating behaviour of glycerol in all lubricating regimes can be improved by adding water. The results suggest that glycerol aqueous solutions have great potential to replace rapeseed oils as environmentally friendly base oils in several applications.

  • 42.
    Shirzadegan, Mohammad
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Almqvist, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Low degree of freedom approach for predicting friction in elastohydrodynamically lubricated contacts2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 94, p. 560-570Article in journal (Refereed)
    Abstract [en]

    A low degree of freedom, semi-analytical model for rapid estimation of the friction coefficient in elastohydrodynamically lubricated contacts was developed and tested. Its estimates are based on the shear rate dependent Carreau equation for the apparent viscosity, together with the hydrodynamic pressure and the temperature of the lubricant. To validate the approach, the model's predictions were compared to experimental coefficient of friction measurements acquired using a ball-on-disc test device at various applied loads, entrainment velocities, and slide to roll ratios. The model’s predictions were in good agreement with the experimental results, showing that it is suitable for use in multibody dynamics analyses where rapid computation of elastohydrodynamic friction is required to minimize computing time and resource consumption.

  • 43.
    Shirzadegan, Mohammad
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Almqvist, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Low degree of freedom EHL friction: Through fast estimation2015In: 42nd Leeds-Lyon Symposium on Tribology, 2015Conference paper (Refereed)
  • 44.
    Tosic, Marko
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Jovanović, Janko
    Faculty of Mechanical Engineering, University of Montenegro, Montenegro.
    Lohner, Thomas
    Gear Research Centre (FZG), Technical University of Munich (TUM), Germany.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Stahl, Karsten
    Gear Research Centre (FZG), Technical University of Munich (TUM), Germany.
    A Computational Fluid Dynamics Study on Shearing Mechanisms in Thermal Elastohydrodynamic Line Contacts2019In: Lubricants, E-ISSN 2075-4442, Vol. 7, no 8, article id 69Article in journal (Refereed)
    Abstract [en]

    A computational fluid dynamics (CFD) model of the thermal elastohydrodynamically lubricated (EHL) line contact problem has been developed for the purpose of exploring the physical processes that occur inside a thin EHL film subjected to shearing motion. The Navier–Stokes equations are solved by using the finite volume method (FVM) in a commercial CFD software, ANSYS Fluent. A set of user-defined functions (UDF) are used for computing viscosity, density, heat source, temperature of moving surfaces and elastic deformation of the top roller according to well-established equations commonly used in the EHL theory. The cavitation problem is solved by taking into account multiphase mixture flow. The model combinations of Houpert and Ree–Eyring and of Tait and Carreau were used for modeling the non-Newtonian behavior of Squalane and the results were compared. Both rheological models suggest the existence of shear-band and plug-flow at high fluid pressure. Due to the differences in viscosity at GPa-level pressure, the chosen model has substantial influence on the computed shear stress and temperature distributions in the high-pressure region. This shows the importance of using correct rheology information in the whole range of pressure, temperature, and shear strain rate.

  • 45.
    Vrček, Aleks
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hultqvist, Tobias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Baubet, Yannick
    SKF, Nieuwegein.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Micro-pitting and wear assessment of engine oils operating under boundary lubrication conditions2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 129, p. 338-346Article in journal (Refereed)
    Abstract [en]

    Current state-of-the-art engine oils tend to enhance micro-pitting damage in rolling contacts under certain operating conditions. ZDDP anti-wear additive was shown to promote such behavior. However, in order to optimize an engine oil formulation for rolling contacts, further studies are needed to assess engine oils in terms of micro-pitting and wear damage. This investigation studies the micro-pitting and wear performance of a number of engine oils for rolling contacts in a ball-on-disc configuration under conditions prevalent in crankshaft roller bearing applications. Based on the results it was concluded that an engine oil containing higher blend of PAO base oil compared to the oil mixture of Group III and PAO has a lower tendency towards micro-pitting and wear.

  • 46.
    Vrček, Aleks
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hultqvist, Tobias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Baubet, Yannick
    SKF Engineering & Research Centre, Nieuwegein, The Netherlands.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction2019In: Lubricants, E-ISSN 2075-4442, Vol. 7, no 5, article id 42Article in journal (Refereed)
    Abstract [en]

    Under certain operating conditions, rolling contacts have been shown to experience some challenges when lubricated with engine oils containing zinc dialkyldithophosphate (ZDDP) anti-wear additive. In order to better understand the main damage mechanisms during various operating conditions, further studies are needed. This article studies micro-pitting and wear damages of bearing steel surfaces under mixed lubrication conditions in a ball-on-disc setup, lubricated with different engine oils. Based on the results, micro-pitting and wear damage is shown to be highly case-dependent. In general, PAO-based engine oil tends to eliminate micro-pitting damage compared to mineral-based engine oil at less severe lubricating conditions. Moreover, a critical lambda was found for both oils, where the highest micro-pitting damage was observed. 

  • 47.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Application of an inclined, spinning ball-on-rotating disc apparatus to simulate railway wheel and rail contact problems2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 374-375, p. 46-53Article in journal (Refereed)
    Abstract [en]

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

  • 48.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Traction formula for rolling-sliding contacts in consideration of roughness under low slide to roll ratios2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 104, p. 263-271Article in journal (Refereed)
    Abstract [en]

    Based on the numerical results of a wide range of parameters in terms of the linear complementarity framework, an easy-to-use formula is presented by using the regression analyses to estimate the traction coefficient for rolling-sliding contacts under low Slide-to-Roll Ratio (SRR) domain for dry condition. The parameters include geometry, surface roughness, SRR and friction coefficient and contact radius. The formula's predictions are in good agreement with measurements using a ball on disc test rig. The results indicate that for steel-steel contact, the effects of third body layer and plasticity on the traction can almost cancel each other out. In addition, by revising the expression proposed by Masjedi and Khonsari, the formula is extended to estimate the cases under mixed lubrication.

  • 49.
    Zhang, Chen Hui
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Zhao, Ying Chun
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wang, Yan
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Lou, Jian Bin
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    EHL properties of polyalkylene glycols and their aqueous solutions2012In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 45, no 3, p. 379-385Article in journal (Refereed)
    Abstract [en]

    Polyalkylene glycols (PAGs) are a type of synthetic lubricants widely used as compressor lubricants, gear oils, hydraulic fluids, and metal working fluids. The PAGs with typical molecular structure can dissolve in water, which makes it a candidate for the base stock of water-based lubricants. Till now, most of the investigations on the water-based lubrication have focussed on the additives. In this work, the potential of PAGs aqueous solutions to replace water as base stocks has been investigated. Four types of PAGs with different molecular weight and their aqueous solutions with different concentrations were studied to reveal their elastohydrodynamic lubrication (EHL) behavior. It has been found that the PAGs solutions can form EHL film like traditional oils. The film-forming capability depends on the viscosity, the pressure-viscosity coefficient, and the molecular weight of PAGs. The results indicate that the PAGs aqueous solution can be employed as base stocks of water-based lubricant

  • 50.
    Zhang, Chenhui
    et al.
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Zhao, Yingchun
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Luo, Jianbin
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Film forming characteristics of polyalkylene glycols aqueous solutions in EHL contact2011In: 6th China International Symposium on Tribology: August 19-22, 2011, Lanzhou, China, Lanzhou, China: State Key Laboratory of Solid Lubrication , 2011, p. 121-121Conference paper (Refereed)
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