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  • 51.
    Höglund, Erik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Uusitalo, Östen
    Luleå tekniska universitet.
    Viscosity-pressure index of two CASTROL oils1995Rapport (Annet vitenskapelig)
  • 52.
    Jacobson, Bo
    et al.
    Luleå tekniska universitet.
    Hamrock, Bernard
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Correlation of rheological characteristics of lubricants with transmission efficiency measurements1985Rapport (Annet vitenskapelig)
    Abstract [en]

    The power efficiency of a helicopter transmission has been analyzed for 11 lubricants by looking at the Newtonian and non-Newtonian properties of the lubricants. A non-Newtonian property of the lubricants was the limiting shear strength proportionality constant. The tests were performed on a high-pressure, short-time shear strength analyzer. The Newtonian and non-Newtonian properties of the lubricants were used in obtaining a power efficiency formula.

  • 53.
    Jacobson, Bo
    et al.
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Jonsson, Ulf
    Luleå tekniska universitet.
    Wardle, F.P.
    Dolfsma, H.
    The effect of refrigerants on the lubrication of rolling element bearings used in screw compressors1992Inngår i: Compressor engineering : 11th International conference : Papers, 1992Konferansepaper (Fagfellevurdert)
  • 54. Jonsson, Ulf
    et al.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Determination of viscosities of oil-refrigerant mixtures at equilibrium by means of film thickness measurements1993Inngår i: ASHRAE Transactions, ISSN 0001-2505, Vol. 99, nr 2, s. 1129-1136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To be able to measure the actual film thickness in a bearing contact lubricated with oil-refrigerant mixtures, a test rig has been designed where the film thickness can be measured by optical interferometry. By calculating backward from the measured film thickness, it is possible to calculate the effective viscosity. The test rig was used to measure the effective viscosity of a polyol ester together with R-134a as a function of temperature and pressure. This paper includes comparisons between viscosity calculated from measured film thickness and viscosity measured with an oscillating bob viscometer. The apparatus was also used for investigating the effect of film thickness of flow rate and sudden changes in pressure.

  • 55.
    Jonsson, Ulf
    et al.
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    The influence of refrigerants on the high pressure properties of lubricating oil1992Inngår i: Tribologia : Finnish Journal of Tribology, ISSN 0780-2285, Vol. 11, nr 2-4, s. 89-96Artikkel i tidsskrift (Fagfellevurdert)
  • 56.
    Kassfeldt, Elisabet
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Artic research in machine design and machine elements1988Rapport (Annet vitenskapelig)
  • 57.
    Larsson, Roland
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Elastohydrodynamic lubrication2004Inngår i: Tribology of mechanical systems: a guide to present and future technologies, New York: American Society of Mechanical Engineers , 2004Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 58.
    Larsson, Roland
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Elastohydrodynamic lubrication at impact loading1994Inngår i: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 116, nr 4, s. 770-776Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The case of a ball impacting a flat lubricated surface is investigated theoretically. This case implies transient conditions and the lubricating effect is due to pure squeeze action in the contact. Results of the analysis show that increasing the velocity, increases the minimum value of film thickness achieved during the total impact time. The damping capacity of the lubricating film is very high at low impact velocity and small ball mass. Thickness of lubricant layer has little effect on the results if it is thicker than certain critical values. If the pressure-viscosity coefficient is increased, the film becomes thicker

  • 59.
    Larsson, Roland
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Elastohydrodynamic lubrication at pure squeeze motion1994Inngår i: Nordtrib '94: proceedings of the 6th Nordic Symposium on Tribulogy ; 12 - 15 June 1994, Uppsala, Sweden / [ed] P. Hedenquist, Uppsala, 1994, s. 103-110Konferansepaper (Fagfellevurdert)
  • 60.
    Larsson, Roland
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Elastohydrodynamic lubrication at pure squeeze motion1994Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 179, nr 1-2, s. 39-43Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experimental and theoretical studies of elastohydrodynamically lubricated contacts normally assume static or quasi-static conditions. Non-steady conditions are, however, common. In this paper the case of a ball impacting a flat lubricated surface is investigated theoretically. This case implies transient conditions and the lubricating effect is due to pure squeeze action. Pressure and film thickness distributions are computed during impact and rebound. The results of the analysis show the effects of ball mass, initial impact velocity, lubricant properties and the thickness of the applied lubricant layer on the minimum film thickness. Increased impact velocity increases the minimum value of film thickness achieved during the bounce. The damping capacity of the lubricating film is very high at low impact velocity and small ball mass. In fact, the damping is so high that no rebound occurs if the velocity or the ball mass are smaller than certain critical values. The thickness of the lubricant layer has no influence on the results if it is greater than a certain value. If the pressure-viscosity coefficient is increased, the film becomes thicker

  • 61.
    Larsson, Roland
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Numerical simulation of a ball impacting and rebounding a lubricated surface1995Inngår i: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 117, nr 1, s. 94-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The case of a ball bouncing on a flat surface covered by a thin lubricant layer is analyzed theoretically. Both impact and rebound are studied. A Newtonian lubricant and perfect elastic solids are assumed. As long as the ball approaches the flat surface the pressure in the contact increases and a lubricant entrapment is formed at the center of the contact. When the ball begins to leave the surface, cavitation occurs. At the periphery of the contact a pressure spike is formed. Just before the ball leaves the lubricated surface, very high pressure values arise at and near the contact center. These results are compared with the case of nonlubricated impact. It is found that the pressure in the contact at lubricated impact is higher than in the case of dry impact. Due to the elastic and damping properties of the lubricant film and the impacting surfaces, a time delay is observed between the time of maximum impact force and minimum film thickness. Comparing the theoretical results with experimental results, presented by other authors, shows good correlations.

  • 62.
    Larsson, Roland
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson-Kråik, Per-Olof
    Eriksson, Erland
    Sjöberg, Martin
    Luleå University of Technology.
    Höglund, Erik
    Lubricant properties for input to hydrodynamic and elastohydrodynamic lubrication2000Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 214, nr 1, s. 17-27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The properties of a number of common lubricants have been measured, namely the viscosity, elastohydrodynamic lubrication (EHL) friction coefficient, density, thermal conductivity and heat capacity per unit volume. These properties have been measured within relatively broad pressure and temperature ranges. The lubricants tested were naphthenic and paraffinic mineral oils, blends of these, polyalphaolefins and a polyglycol. Physical--empirical expressions have been developed upon the basis of the measurement results and a number of lubricant constants, or lubricant parameters, have been determined for each lubricant. These expressions can be used in engineering computational tools for lubrication analysis. The use of such analyses is expected to increase into the new millennium and it is thus important to provide reliable and relevant input data

  • 63. Larsson-Kråik, Per-Olof
    et al.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Jonsson, Ulf
    Luleå tekniska universitet.
    Mätning av viskositet och filmtjocklek för två polyalfaolefiner1992Rapport (Annet vitenskapelig)
  • 64. Larsson-Kråik, Per-Olof
    et al.
    Jacobson, Bo
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oil drop formation at the outlet of an elastohydrodynamic lubricated point contact1994Konferansepaper (Fagfellevurdert)
  • 65. Larsson-Kråik, Per-Olof
    et al.
    Jacobson, Bo
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oil drop formation at the outlet of an elastohydrodynamic lubricated point contact1995Inngår i: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 117, nr 1, s. 74-79Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The loss of lubricant from grease-lubricated bearing surfaces is determined by a number of different mechanisms such as side-flow out of the contacts, evaporation, drop formation, oxidation etc. Some of the drops formed behind a rolling element in a bearing will be onrolled by the next rolling element but some will be lost from the bearing. This loss of lubricant is dependent to a high degree on the speed of the air flow through the bearing and is one of the reasons for early failure of grease lubrication in bearings operating in strong, axial air streams. To evaluate the most important parameters in drop formation, the droplets being thrown out from the outlet of an elastohydrodynamic contact were analyzed using picture processing and statistical methods. An empirical model has been built to describe mathematically the principal factors involved in the volume flow thrown out into the air at the outlet side of the Hertzian contact area. For example, drops in a ball bearing will contribute to the inlet feed of oil for the next ball if it is not lost by sideways flow out from the bearing.

  • 66. Larsson-Kråik, Per-Olof
    et al.
    Jacobson, Bo
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oil drops leaving an EHD contact1994Inngår i: Nordtrib '94: proceedings of the 6th Nordic Symposium on Tribulogy ; 12 - 15 June 1994, Uppsala, Sweden / [ed] P. Hedenqvist, Uppsala, 1994, s. 75-83Konferansepaper (Fagfellevurdert)
  • 67. Larsson-Kråik, Per-Olof
    et al.
    Jacobson, Bo
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oil drops leaving an EHD contact1994Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 179, nr 1-2, s. 23-28Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many machine elements are lubricated with oil or grease. The flow of lubricant depends on different parameters such as surface roughness, surface energy, temperature, etc. A known problem with rolling bearings is that lubricants have to be refilled more frequently if a gas stream passes through the bearing. It is therefore important to know the behaviour of the lubricant in order to predict, e.g. bearing fatigue life due to a gas stream. By studying the droplets thrown out into the air after passing an elastohydrodynamic contact, the most important parameters for oil drop formation have been determined. The analysis is based on picture processing and statistical methods. The experiments show that an increase in temperature, viscosity or surface velocity will increase the total drop volume. Decreased contact pressure and pure rolling also increase the total drop volume. The volume flow, passing the Hertzian contact area, varied between 18 and 30% of the air born oil-drop flow and it is reasonable to assume that increased flow of air-borne droplets will decrease the film thickness due to insufficient replenishment.

  • 68.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Grease Free Surface Flow on a Rotating Plate: a Combined Experimental and Analytical Analysis2014Konferansepaper (Fagfellevurdert)
  • 69.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Green, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Baart, Pieter
    µPIV measurement of grease velocity profiles in channels with two different types of flow restrictions2012Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 54, s. 94-99Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Grease is commonly used to lubricate various machine components such as rolling bearings and seals. In this paper the flow of lubricating grease passing restrictions is described. Such flow occurs in rolling bearings during relubrication events where the grease is flowing in the transverse (axial) direction through the bearing and is hindered by guide rings, flanges et cetera, as well as in seals where transverse flow occurs, for example during so-called breathing caused by temperature fluctuations in the bearing. This study uses a 2D flow model geometry consisting of a wide channel with rectangular cross-section and two different types of restrictions to measure the grease velocity vector field, using the method of Micro Particle Image Velocimetry. In the case of a single restriction, the horizontal distance required for the velocity profile to fully develop is approximately the same as the height of the channel. In the corner before and after the restriction, the velocities are very low and part of the grease is stationary. For the channel with two flow restrictions, this effect is even more pronounced in the “pocket” between the restrictions. Clearly, a large part of the grease is not moving. This condition particularly applies to the cases with a low-pressure drop and where high consistency grease is used. In practice this means that grease is not replaced in such “corners” and that some aged/contaminated grease will remain in seal pockets.

  • 70.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Zhmud, Boris
    Applied Nano Surfaces.
    Rheology of Lubricating Grease2015Inngår i: Lube Magazine, ISSN 1744-5418, Vol. 126, s. 12-18Artikkel i tidsskrift (Fagfellevurdert)
  • 71.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Baart, Pieter
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Experimental study of free surface grease flow subjected to centrifugal forces2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to improve the understanding of grease flow in various applications such as gears, seals and rolling bearings, the free surface flow of different greases under different running conditions has been investigated. A rotating disc has been used to study grease flow as the grease was subjected to a centrifugal force. The grease flow and mass loss was measured for greases with different rheology on different surfaces and with surface textures. It is shown that the speed at which grease starts to move is mostly determined by grease type and yield stress, while the impact of the surface material and roughness is less pronounced. The mass loss is shown to be influenced both by the rheology of the grease and the surface material

  • 72.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet
    SKF ERC.
    Baart, Pieter
    SKF ERC.
    Lubricating Grease Shear Flow and Boundary Layers in a Concentric Cylinder Configuration2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Grease is extensively used to lubricate various machine elements such as rolling bearings, seals, and gears. Understanding the flow dynamics of grease is relevant for the prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. In this study, grease flow is visualized using micro Particle Image Velocimetry (μPIV). The experimental setup includes a concentric cylinder configuration with a rotating shaft to simulate the grease flow in a double restriction seal geometry with two different grease pocket sizes. It is shown that the grease is partially yielded in the large grease pocket geometry and fully yielded in the small grease pocket. For the small grease pocket, it is shown that three distinct grease flow layers are present: a high shear rate region close to the stationary wall, a bulk flow layer, and a high shear rate boundary region near the rotating shaft. The grease shear thinning behavior and its wall slip effects have been identified. The μPIV experimental results have been compared with a numerical model for both the large and small gap size. It is shown that the flow is close to one-dimensional in the center of the small pocket. A one-dimensional analytical model based on the Herschel-Bulkley rheology model has been developed, showing good agreement with the measured velocity profiles in the small grease pocket. Furthermore, wall slip effects and shear banding are observed, where the latter imply that using the assumption of uniform shear in conventional concentric cylinder rheometers may result in erroneous rheological results.

  • 73.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet
    Baart, Pieter
    SKF Engineering & Research Center, Nieuwegein.
    Lubricating grease shear flow and boundary layers in a concentric cylinder configuration2014Inngår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 57, nr 6, s. 1106-1115Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Grease is extensively used to lubricate various machine elements such as rolling bearings, seals, and gears. Understanding the flow dynamics of grease is relevant for the prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. In this study, grease flow is visualized using microparticle image velocimetry (μPIV). The experimental setup includes a concentric cylinder configuration with a rotating shaft to simulate the grease flow in a double restriction seal geometry with two different grease pocket sizes. It is shown that the grease is partially yielded in the large grease pocket geometry and fully yielded in the small grease pocket. For the small grease pocket, it is shown that three distinct grease flow layers are present: a high shear rate region close to the stationary wall, a bulk flow layer, and a high shear rate boundary region near the rotating shaft. The grease shear thinning behavior and its wall slip effects have been identified. The μPIV experimental results have been compared with a numerical model for both the large and small gap size. It is shown that the flow is close to one-dimensional in the center of the small pocket. A one-dimensional analytical model based on the Herschel-Bulkley rheology model has been developed, showing good agreement with the measured velocity profiles in the small grease pocket. Furthermore, wall slip effects and shear banding are observed, where the latter imply that using the assumption of uniform shear in conventional concentric cylinder rheometers may result in erroneous rheological results.

  • 74.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Design of test rig for visualizations of cylindrical shear and pressure driven Couette flow using μPIV2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Couette flow is often encountered in concentric cylinder application such as rheometers etc. Being able to visualize such flows is of interest both from a fundamental point of view to understand the dynamics of complex fluids, but also in specific applications such as lubricants flowing through seal geometries. In this study a concentric cylinder test rig has been designed to visualize Couette flow in both radial and axial direction using micro Particle Image Velocimetry. The rig allows for control of the flow motion; the rotating inner cylinder creates a peripheral flow and an applied pressure in the axial direction creates a pressure driven flow. Thus, a single flow direction or a combination of directions can be analyzed. To demonstrate the technique a flow of a non-Newtonian shear thinning fluid in the form of lubricating grease was investigated and discussed. It is found that it is possible to capture the yield behavior of the grease, with regions of fully and partially yielded flow visible. The influence of temperature creep flow is also presented. Grease with both high and low yield stress are measured and compared could be measured and compared in a pocket with variable size. Furthermore, non-homogeneous effects such as shear banding and wall slip can be visualized. The test rig has thus a high potential to investigate the influence of wall material and wettability between fluids and the housing on the flow and wall slip behavior as long as the fluid is optically transparent.

  • 75.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Grease free surface flow on a rotating plate2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to improve the understanding of grease flow in various applications such as gears, seals and rolling element bearings, free surface flow of different greases under different running conditions has been investigated. A rotating disc has been used to study grease flow as the grease is subjected to a centrifugal force. The adhesion and mass loss was detected for greases with different rheology on different surfaces and surface textures. It is shown that the speed at which grease starts to move is mostly determined by grease type, yield stress and bleeding properties rather than surface material. Also, the surface adhesion is shown to be influenced both by the rheology of the grease and the surface material.

  • 76.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Baart, Pieter
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Lubricating grease shear flow and boundary layers in a concentric cylinder configuration2013Inngår i: Proceedings of the 3rd International Tribology Symposium of IFoMM (International Federation for the Promotion of Mechanism and Machine Science), Luleå, March 19-21, 2013, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Grease is extensively used to lubricate various machine elements such as rollingbearings, seals, and gears. Understanding the flow dynamics of grease is relevant forthe prediction of the grease distribution for optimum lubrication and the migration ofwear- and contaminant particles. In this study grease flow is visualized using themethod of micro Particle Image Velocimetry; the experimental setup comprises aconcentric cylinder with rotating shaft to simulate the grease flow in a DoubleRestriction Seal (DRS) geometry with two different grease pocket heights. It is shownthat grease may be partially yielded in the large grease pocket geometry and fullyyielded in the small grease pocket geometry. For the small grease pocket geometry, itis shown that three distinct grease flow layers are present: a high shear rate regionclose to the stationary wall, a bulk flow layer, and a high shear rate boundary regionnear the rotating shaft. The grease shear thinning behaviour and its wall slip effectshave been detected and discussed.

  • 77. Lindholm, P.
    et al.
    Larsson, Roland
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Tribological test of iron powder lubricants and iron powder mixtures1996Inngår i: Modelling in materials science and processing., European Commission Joint Research Centre, 1996Konferansepaper (Fagfellevurdert)
  • 78.
    Lingesten, Niklas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    On the significance of operating temperature to the durability of a wet clutch2013Konferansepaper (Fagfellevurdert)
  • 79.
    Lingesten, Niklas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Studies on wear phenomena in wet clutches2012Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Wet clutches are critical components in many automatic transmissions in the automotive industry. These components handle large amounts of energy through sliding friction as they engage during machine operation, resulting in clutch disc wear. Wear experiments at high clutch engagement energies has revealed that a change in the friction material wear rate can occur at some point during the test, i.e. transitioning from a low to a high wear rate. This brings into question the conventional way of performing wear tests i.e. measuring a specimen before and after testing and the usual way of viewing wear i.e. as a constant wear rate after running in. The authors propose a two step wear model to describe the wear that can occur under some conditions exemplified in this paper.

  • 80.
    Lingesten, Niklas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    The influence of repeated high-energy engagements on the permeability of a paper-based wet clutch friction material2017Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 231, nr 12, s. 1574-1582Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The behavior of a wet clutch during engagement is of great importance to the durability of the clutch and the drivability of a vehicle. While many different factors influence the engagement behavior, the focus of this paper is to investigate only one factor, the permeability of the wet clutch friction material. Two test cells for measuring the permeability of friction material mounted on clutch discs have been developed. The test cells were then used to examine the effect of clutch material ageing through clutch engagement on the permeability of the material. The tests were performed on full size friction discs including the steel core prior and subsequent to testing in a wet clutch engagement test rig. The ability of the friction material to allow for oil flow both through the sliding surface layer and the bulk of the material was measured. The results indicate that repeated clutch engagements will increase the bulk permeability. However, the repeated engagements will decrease the ability to pass fluid through the friction material sliding surface. This contradictory behavior could be explained by a combination of an increase in pore size through repeated compression and the surface glaze clogging of the friction interface surface pores.

  • 81.
    Lingesten, Niklas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lund, Martin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundin, Joakim
    Volvo Construction Equipment.
    Mäki, Rikard
    Volvo Construction Equipment.
    Apparatus for continuous wear measurements during wet clutch durability tests2012Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 288, s. 54-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 82. Lundberg, Jan
    et al.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    A new method for determining the mechanical stability of lubricating greases2000Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 33, nr 3-4, s. 217-223Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mechanical stability is of central importance when dealing with the long-term service-length of grease-lubricated roller bearings. Poor stability will lead to consistency degradation of the grease, because of mechanical forces between the rolling parts of the bearing. The result can be leakage of grease through seals, or at worst a total failure of the bearing. The present investigation was initiated because present-day methods for prediction of mechanical stability show weak correlation with real service-length. The aim of the project was to develop a useful alternative. In order to fulfil this, both field tests and laboratory tests were carried out. In the field tests, nine different commercial greases were examined in the wheel bearings of five ore waggons, used for transporting ore by railroad from the Kiruna Mine in northern Sweden to Narvik in northern Norway for shipping to foreign markets. The test ore waggons travelled a distance of about 300,000 km during a period of 3 years. Small samples of greases were taken, on eight different occasions, for consistency testing. After the end of the test period, the damage on the bearings was also studied. In the laboratory tests, new undestroyed greases of the same brand as in the field tests were examined using conventional methods, such as the V2F, the Roll Stability Test and the Grease Worker. Comparisons between the field tests and these laboratory tests indicate poor correlation. In addition to these conventional methods, the relevance of the shear strength of the greases to the prediction of the mechanical stability was also tested. The shear stress τL depends on the applied pressure p, thus τL=τO+γ·p where τO is the shear stress at atmospheric pressure, γ is a property of the lubricant in the same way as viscosity or density. It was found that γ correlates well with the mechanical stability in service. Increased γ values lead to a decrease in the mechanical stability. One reasonable explanation is that high γ values correspond to high shear stresses in the grease, and thus severe conditions for the thickener.

  • 83.
    Lundberg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of limiting shear strength of oils on breakdown of a lubricating oil film1992Inngår i: Tribologia : Finnish Journal of Tribology, ISSN 0780-2285, Vol. 11, nr 4, s. 106-114Artikkel i tidsskrift (Fagfellevurdert)
  • 84.
    Lundberg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Velocity measurements in a squeeze/sliding lubricated contact1991Inngår i: Tribologia : Finnish Journal of Tribology, ISSN 0780-2285, Vol. 10, nr 4, s. 32-47Artikkel i tidsskrift (Fagfellevurdert)
  • 85.
    Lundberg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Åström, H.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Grease lubrication of an elliptical EHD: contact in combined squeezing and sliding1990Inngår i: Putting tribology to work: reliability and maintainability through lubrication and wear technology ; preprints of papers ; Brisbane, 2 - 5 December 1990 / International Tribology Conference 1990, Barton: Academia adacta, 1990, s. 151-155Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Experimental investigations have been made using an apparatus specially built to study lubrication combined squeezing and sliding. In this investigation nine different lubricating greases and two base oils have been tested. The results are presented as a critical sliding velocity above which asperity contact occurs. The squeeze (normal) velocity was 0.2 m/s and the critical sliding velocity was between 1 and 6 m/s depending on the lubrican Although the greases have the same NLGI grade (2), they show quite different lubricating ability. The experiment showed that the lithium and lithium complex thickeners increased the lubrication ability of the base oil.

  • 86. Lundmark, Jonas
    et al.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Running-in behaviour of rail and wheel contacting surfaces2006Inngår i: AITC-AIT 2006: 5th International Conference on Tribology ; 20 - 22 September 2006, Parma, Italy, 2006, s. 33-Konferansepaper (Fagfellevurdert)
  • 87. Marklund, Pär
    et al.
    Mäki, Rikard
    Larsson, Roland
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Khonsari, Michael. M.
    Louisiana State University.
    Jang, Joonyoung
    Louisiana State University.
    Ganemi, Bager
    Statoil Lubricants.
    Ohlsson, Richard
    Haldex Traction AB.
    Thermal influence on torque transfer of wet clutches in limited slip differential applications2005Inngår i: Proceedings of the World tribology congress III: presented at ..., September 12 - 16, 2005, Washington, DC, New York: American Society of Mechanical Engineers , 2005, s. 245-246Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Wet clutches operating under low velocity and high load are studied with the aim of obtaining reliable models for the torque transfer during boundary lubrication conditions.

  • 88.
    Marklund, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Mäki, Rikard
    Larsson, Roland
    Höglund, Erik
    Khonsari, M.M.
    Louisiana State University.
    Jang, Joonyoung
    Louisiana State University.
    Thermal influence on torque transfer of wet clutches in limited slip differential applications2007Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, nr 5, s. 876-884Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wet clutches operating under low velocity and high load are studied with the aim of obtaining reliable models for the torque transfer during boundary lubrication conditions. A friction model which takes temperature, speed and nominal pressure into account is developed and used with temperature calculations to be able to simulate behavior of a wet clutch working in boundary lubrication regime. Predicted torque and temperatures from the model agree well with experimental data.

  • 89. Mäki, Rikard
    et al.
    Ganemi, Bager
    Svenska Statoil AB.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Olsson, Richard
    Haldex Traction Systems AB.
    Wet clutch transmission fluid for AWD differentials: influence of lubricant additives on friction characteristics2007Inngår i: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 19, nr 2, s. 87-99Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In recent years, several electronically controllable automotive transmission systems using wet clutches as intelligent differentials have emerged on the market. These applications place great demands on the anti-shudder properties of the transmission fluids used. The aims of this study were (i) to investigate the influence of different additives on the friction characteristics of a transmission fluid for all-wheel drive systems featuring wet multi-plate clutch with a sintered brass-based friction material and, based on this knowledge, (ii) to formulate a new transmission fluid with the desired frictional properties. In addition to excellent anti-shudder properties, the new fluid was required to lubricate hypoid gears under high load. To meet this requirement, it is necessary to add significant amounts of extreme pressure additives to the base oil, which are known to have an unfavourable influence on anti-shudder properties, necessitating the adoption of novel additive technologies. The additives studied include anti-wear additives, friction modifiers, corrosion inhibitors, detergents, antioxidants and extreme pressure additives. This paper shows how different additives affect friction in different ways, and that the interactions between the different additives are important to consider. It was concluded that it is feasible to combine good anti-shudder properties for wet clutches with good lubrication of hypoid gears.

  • 90.
    Sarkar, Chiranjit
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, Staffan T.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Numerical simulations of lubricating grease flow in a rectangular channel with and without restrictions2018Inngår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 61, nr 1, s. 144-156Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents numerical simulations of the laminar flow of lubricating greases in a channel with rectangular cross section. Three greases with different consistencies (NLGI grades 00, 1, and 2) have been considered in three different configurations composed of a rectangular channel without restrictions, one rectangular step restriction, and one double-lip restriction. The driving pressure drop over the channel spans from 30 to 250 kPa. The grease rheology is described by the Herschel-Bulkley rheology model, and both the numerical code and rheology model have been validated with analytical solutions and flow measurements using micro-particle image velocimetry.

  • 91.
    Shah, Faiz Ullah
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Glavatskih, Sergei
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lindberg, Mats
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Interfacial antiwear and physicochemical properties of alkylborate-dithiophosphates2011Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 3, nr 4, s. 956-968Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Boron compounds have become of interest in tribology because of their unique tribochemical and tribological properties. At the same time, dialkyldithiophosphates (DTPs) of transition metals have been extensively used as multifunctional additives in lubricants to control friction and reduce wear in mechanical systems. Because of the environmental pollution and health hazards of these compounds, ashless compounds with reduced amounts of sulfur and phosphorus are desirable. This work reports on the synthesis, characterization, and tribological properties of a new class of compounds, alkylboratedithiophosphates. This class combines two high-iron-affinity surface active groups, borate and dialkyldithiophosphate, into a single molecule. The final products, viscous liquids, were characterized by FT-IR, multinuclear 1H, 13C, 31P, and 11B NMR spectroscopy and thermal analyses. Residues of one representative compound from this class, DPB-EDTP, after thermal analyses were additionally characterized by multinuclear 13C, 31P and 11B MAS and 31P CP/MAS NMR spectroscopy. Solid-state NMR data suggest that a dominant part of the solid residue of DPB-EDTP consists of borophosphates. Antiwear and friction properties of a mineral oil with these novel additives were evaluated in a four-ball tribometer in comparison with O,O0-di-n-butyl-dithiophosphato-zinc (II), Zn-BuDTP, as a reference lubricant additive. The surface morphology and the elemental composition of the tribofilms were characterized using scanning electron microscopy with energy-dispersive X-rays spectroscopy (SEM/EDS). The results show that alkylborate-dithiophosphates, with substantially reduced amounts of sulfur and phosphorus compared with Zn-BuDTP, have considerably better antiwear and friction performance.

  • 92.
    Westerberg, Lars-Göran
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Farré-Lladós, Josep
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    Li, Jinxia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Casals-Terré, Jasmina
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    Grease flow in elbow channel2014Inngår i: Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2014, Society of Tribologists and Lubrication Engineers , 2014, Vol. 1, s. 398-400Konferansepaper (Fagfellevurdert)
  • 93.
    Westerberg, Lars-Göran
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Farré-Lladós, Josep
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    Li, Jinxia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Casals-Terré, Jasmina
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    Grease flow in an elbow channel2015Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 57, nr 3, artikkel-id 30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The flow of lubricating greases in an elbow channel has been modeled and validated with velocity profiles from flow visualizations using micro-particle image velocimetry. The elbow geometry induces a nonsymmetric distribution of shear stress throughout its cross section, as well as varying shear rates through the transition from the elbow inlet to the outlet. The flow has been modeled both for higher flow rates and for creep flow. The influence of the grease rheology and flow conditions to wall slip, shear banding and an observed stick–slip type of motion observed for low flow rates are presented. The effect on the flow of the applied pressure is also modeled showing that the flow is sensitive to the pressure in the angular ( ϕ ) direction of the elbow. For high pressures, it is shown that the flow is reversed adjacent to the elbow walls.

  • 94.
    Westerberg, Lars-Göran
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Green, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Li, Jinxia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Baart, Pieter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Understanding grease flow through optical visualizations2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The flow dynamics of a lubrication mechanism is very complex, much due to the complex rheology and composition of the grease. In order to obtain an optimal lubrication, both the initial amount of grease and the position of the grease is highly important as too much grease will contribute to an increased friction, and grease in the wrong place will negatively affect the replenishment through oil bleeding. To understand the flow dynamics of grease hence is highly important for the understanding of the lubrication mechanism. Using micro Particle Image Velocimetry (μPIV) we have in a series of studies investigated the dynamics of grease flow in 2D straight channels with- and without restrictions, and in a full 3D configuration comprising a double restriction seal geometry. Velocity profiles for greases of different thickness have been measured, showing the influence of the grease rheology on the grease flow behaviour. KEYWORDS: Lubricants:Greases, Lubricant Physical Analysis:Non-Newtonian Behavior, Lubricant Physical Analysis:Rheology.

  • 95.
    Westerberg, Lars-Göran
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Li, Jinxia
    Lugt, Piet
    SKF ERC, University of Twente/SKF ERC.
    Baart, Pieter
    SKF ERC.
    Free-Surface Flow of Lubricating Greases2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Grease lubrication is traditionally used in a great variety of mechanicalsystems such as rolling bearings, seals, and gears where it has beenshown more advantageous than oil, mainly due to its consistencyallowing the grease to stay inside the system and not leak out. Freesurface effects play an important role in rolling bearings and opengears as the configuration normally is filled with about 30% grease toavoid heavy churning. In this study an analytical model of thestationary uniform flow on a rotating disc is developed and validatedwith experiments. The model results in the velocity profile for the flowin the thin fully yielded viscous layer in connection to the surface aswell as an expression for the plug flow region on top of the viscouslayer. Experiments with two different greases having NLGI grade 1 and2 respectively shows it is possible to obtain a good fit with theanalytically obtained thickness using the rheological parameters foractual greases.

  • 96.
    Westerberg, Lars-Göran
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Sarkar, Chiranjit
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Modelling and experimental validation of grease flow2016Inngår i: Eurogrease Magazine, nr 4, s. 17-32Artikkel i tidsskrift (Annet vitenskapelig)
  • 97.
    Westerberg, Lars-Göran
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Sarkar, Chiranjit
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Modelling and experimental validation of lubricating grease flow2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Being able to fully model the flow dynamics of grease, including phase separation, will be highly valuable in the design of lubricated machine elements such as rolling element bearings. Complete models will also be a valuable tool in the process of providing tailor-made greases for different applications. An understanding of the grease flow dynamics enables prediction of grease distribution for optimum lubrication and for the migration of wear- and contaminant particles. In this paper the potential of combined analytical modelling, flow visualizations, and numerical modelling in grease flow dynamics is presented. Specifically, the relation between the rheology of the grease and its impact on the flow motion is of interest in combination with validation of the numerical models in simplified geometries. The numerical models then enable simulations in more complex geometries of particular interest for the grease and bearing industry. It is shown that grease flow is heavily influenced by its non-Newtonian properties and the shear rates in the contact, resulting in distinct regions of yielded and un-yielded grease. Further, the numerical models are shown to match well with experiments and analytical models, enabling numerical models on more complicated geometries.

  • 98.
    Westerberg, Lars-Göran
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Sarkar, Chiranjit
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    On the Flow of Lubricating Greases: a Computational Fluid Dynamics Approach2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Being able to model the flow dynamics of grease is highly valuable in the design of lubricated machine elements such as rolling element bearings. An understanding of the grease flow dynamics enables prediction of grease distribution for optimum lubrication and for the migration of wear- and contaminant particles. In this paper the potential of combined analytical modelling, flow visualizations, and numerical modelling in grease flow dynamics is presented. Specifically, the relation between the rheology of the grease and its impact on the flow motion is of interest in combination with validation of the numerical models in simplified geometries. The numerical models then enable simulations in more complex geometries of particular interest for the grease and bearing industry. It is shown that grease flow is heavily influenced by its non-Newtonian properties and the shear rates in the contact, resulting in distinct regions of yielded and un-yielded grease. Further, the numerical models are shown to match well with experiments and analytical models, enabling numerical models on more intricate geometries in the bearing industry.

  • 99.
    Westerberg, Lars-Göran
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Li, Jinxia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Green, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lugt, Piet
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Baart, Pieter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    μPIV measurements of lubricating grease flow in channel with two types of restrictions2012Konferansepaper (Fagfellevurdert)
  • 100.
    Westerberg, Lars-Göran
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Li, Jinxia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Lugt, Piet
    SKF ERC, Tribology Group.
    Baart, Pieter
    SKF ERC, Tribology Group.
    Free-surface grease flow: influence of surface roughness and temperature2015Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 59, nr 1, artikkel-id 18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Grease flow in grease lubricated systems can often be qualified as free-surface flow. It occurs for example in rolling bearings after the churning phase or on open gears. Here only a fraction of the bearing or gearbox volume is filled with grease. Part of the grease is flowing in relatively thin layers induced by centrifugal forces caused by rotation of the various components. In this paper a model problem is investigated in the form of a free-surface flow of grease on a rotating disc. Experiments have been performed where the onset of flow and remaining grease have been studied varying the surface roughness, temperature and the centrifugal forces. The experiments have been coupled to analytical models describing the flow and temperature distribution in the grease. It was found that the impact of surface roughness could be neglected. The flow is determined by the centrifugal forces and rheology of the grease. Temperature effects the rheology but also the oil separation creating low shear strength/low viscosity layers at the surface.

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