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  • 1.
    Bååth, Lars B.
    et al.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK).
    Löfgren, Hans
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK).
    Ny teknologi för avisning av vindkraftvingar2008Conference paper (Other academic)
  • 2.
    Bååth, Lars
    et al.
    Halmstad University, School of Business, Engineering and Science, Mechanical Engineering and Industrial Design (MTEK), Fotonik och mikrovågsteknik.
    Löfgren, Hans
    Halmstad University, School of Business, Engineering and Science, Mechanical Engineering and Industrial Design (MTEK).
    Ny teknik för avisning av vindkraftsvingar2008Report (Other academic)
    Abstract [en]

    This is a pilot study to investigate icing on wings of wind power turbines. In this report we present and discuss various ways and means to either heat water droplets or melt ice when formed on the wings of wind turbines. The situation is different from icing on wings of airplanes in that (1) the wings of wind turbines spend all of their time in the atmosphere where the risk of icing is highest and (2) the speed of wing to air varies over the wing where it is constant for an airplane. The form of the wind turbine wings also varies from tip to centre, to compensate for the varying relative air speed.

    We have concentrated on icing conditions at temperatures -10°C – 0°C and droplet sizes of 1-10 μm. Icing occurs also at much lower temperatures, but this will probably be because of direct freezing of water vapour to ice. This is presently outside the scope of our pilot project report.

    We conclude that

    • The form of the wing, especially on the contact area may be crucial to the icing problem.
    • Also the nano-metric structure of the wing surface can probably be designed so that the water droplets have a minimized contact area to the wing.

    Our pilot investigation also suggests the following:

    • Microwaves are much too inefficient to heat water or melt ice. Direct microwave devices should therefore not be developed. Indirect heating with microwaves is possible.
    • Millimeter waves are sufficiently efficient, but the generation is most probably too inefficient to be of any practical use.
    • Infrared waves are very efficient to heat water and melt ice and should be investigated.
    • Heat conduction is also efficient and should be pursued. Using microwaves to heat the wing surface which then conduct heat to the water/ice is a very efficient and robust method.

    Our pre-study suggests that the solution to avoid icing or de-ice wings of wind turbines most probably is not one single technology. The form and surface structure of the wings play important role for icing conditions. Both variables have to be modified depending on the latitude and atmospheric climate. The surface structure also has to be designed to vary over the wing, both along and across to be optimized for the mean conditions at the site. In addition, heating of the impact area, or at least the possibility to heat this, may be important to avoid loss of energy output due to ice.

    Further research is required. We strongly suggest investigating the water droplet flow over the wing as function of the cross section form, and the contact with the wing surface as function of the surface structure (e.g. Lotus effect).

    The present report is the result of a pre-study project. We will now continue with a deeper project which will concentrate on the form and surface structure suggestions which results from our analysis and flow simulations.

  • 3.
    Cabanettes, Frédéric
    et al.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Löfgren, Hans Bertil
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Rosén, Bengt-Göran
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Evaluation of manufacturing processes for cam/roller contact2011Conference paper (Refereed)
  • 4.
    Cabanettes, Frédéric
    et al.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Löfgren, Hans Bertil
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Rosén, Bengt-Göran
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    The impact of manufacturing processes on Automotive Cam/Roller Contact2011Conference paper (Refereed)
  • 5.
    Dimkovski, Zlate
    et al.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Anderberg, Cecilia
    Volvo Power Train Corp., Volvo Group, Göteborg, Sweden.
    Cabanettes, Frédéric
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Löfgren, Hans
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Rosén, B.-G.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Influence of Different Cylinder Liner Surfaces on Their Performance with the Twin Land Oil Control Ring in a Car Engine2011In: Proceedings of the 13th International Conference on Metrology and Properties of Engineering Surfaces, 2011Conference paper (Refereed)
  • 6.
    Dimkovski, Zlate
    et al.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Cabanettes, Frédéric
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Löfgren, Hans
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Anderberg, Cecilia
    Volvo Cars.
    Ohlsson, Robert
    Volvo Powertrain.
    Rosén, Bengt-Göran
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Optimisation of Cylinder Liner Surface Finish by Slide Honing2012In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 226, no 4, p. 575-584Article in journal (Refereed)
    Abstract [en]

    Cylinder liner surface finish controls the frictional losses, oil consumption, and emissions of internal combustion engines to a large extent. In order to minimize such losses, it is important to optimize the liner surface topography by a consistent and more productive finishing process such as slide honing. This process employs diamond abrasives and has been recently introduced in the automotive industry. In this study, its potentials are explored, especially the winning combination of its key process parameters: the base honing pressure and plateau honing time that would yield an optimal liner surface finish. A number of truck engine liners were slide-honed by using different process parameters, samples of the liners were cut, and three-dimensional (3D) surface measurements were taken on a white light interferometer. Then, among others, the (deep honing) groove parameters, specific for liner surfaces, were computed from the measurements for building a large database for comparison and correlation. By simulating the contact and fluid mechanics between the measured liner topographies and a twin land oil control ring under mixed lubrication conditions, the friction mean effective pressure and oil passage rate for a range of engine speeds were calculated. These two parameters represent the liner's function associated with the engine's friction and oil consumption respectively. The results show that the lowest friction and oil flow are highly correlated with surfaces having smoother plateaus and smaller valleys, finished by using lower base honing pressure and longer plateau honing time. High correlations between the 3D roughness parameters were also found, enabling the selection and use of more stable and robust parameters in the quality control of the liner's surface finish. © IMechE 2012.

  • 7.
    Gåård, Anders
    et al.
    Karlstads Universitet, Karlstad, Sverige.
    Löfgren, Hans
    Halmstad University, School of Business, Engineering and Science, The Rydberg Laboratory for Applied Sciences (RLAS).
    Nilsson, Bertil
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Hallbäck, Nils
    Karlstads Universitet, Karlstad, Sverige.
    Införandet av Computer Based Mathematics (CBM) i ingenjörsutbildningar2017Conference paper (Other (popular science, discussion, etc.))
    Abstract [sv]

    CBM är ett koncept som innebär användning av datorn och matematikprogramvaror som huvudverktyg i under-visningen. Istället för att som i traditionell undervisning kombinera handräkning med datorlabbar ligger tyngdpunkten i en CBM-kurs på datoriserade beräkningsverktyg. Härav för-flyttas fokus mot konceptförtåelse, modellering och tolkning av resultat. Vid Högskolan i Halmstad och Karlstads Universitet finns idag flera kurser baserat på CBM. Kvantitativt har införandet lett till ökad studentgenomströmning samtidigt som innehållet i kurser har ökat. Kvalitativa markörer, såsom studentens egen uppfattning om konceptuell förståelse och nyfikenhet inom ämnet, har baserat på kursvärderingar också ökat. 

  • 8.
    Löfgren, Hans
    Halmstad University, School of Business, Engineering and Science, The Rydberg Laboratory for Applied Sciences (RLAS).
    A first order friction model for lubricated sheet metal forming2018In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 8, no 1, p. 57-61Article in journal (Refereed)
    Abstract [en]

    This paper presents the derivation of a first order friction model for lubricated sheet metal forming. Assuming purely plastic real contacts, Newton's law of viscosity, and a square root behavior of the hydrodynamic coefficient of friction with respect to the hydrodynamic Hersey parameter an analytic model is found. The model predicts the coefficient of friction as a function of the relative pressure, the relative Hersey parameter and the real contact coefficient of friction. Questions about local and global friction are raised in the validation of the model against flat tool sheet experiments. For some flat tool sheet experiments reasonable agreements are obtained assuming a rigid punch pressure distribution. The restricted number of user inputs makes the model useful in early tool design simulations. © 2018 The Authors. Published by Elsevier Ltd on behalf of The Chinese Society of Theoretical and Applied Mechanics

  • 9.
    Löfgren, Hans Bertil
    Halmstad University, School of Business, Engineering and Science, Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    A solution to the hydrodynamic lubrication of a circular point contact sliding over a flat surface with cavitation2012In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 2, no 3, article id 032004Article in journal (Refereed)
    Abstract [en]

    This letter presents an analytical solution to the hydrodynamic lubrication of a circular point contact sliding over a flat surface with cavitation. The solution is found by solving the Reynolds equation with Reynolds boundary condition for cavitation. The cavitation boundary is shown to be straight lines directed 108.4° against the sliding direction. The result is experimentally verified in the limit of large values of viscosity, sliding velocity and radius of a spherical ball. The solution raises questions about the coupling between cavitation and film rupture and can be used as an independent check on the validity of numerical solutions.

  • 10.
    Philip, Rony
    et al.
    Amrita University, Coimbatore, India.
    Löfgren, Hans
    Halmstad University, School of Business, Engineering and Science, The Rydberg Laboratory for Applied Sciences (RLAS).
    Experimental Verification of an Instrument to Test Flooring Materials2018In: IOP Conference Series: Materials Science and Engineering, Bristol: Institute of Physics Publishing (IOPP), 2018, Vol. 310, no 1, article id 012121Conference paper (Refereed)
    Abstract [en]

    The focus of this work is to validate the fluid model with different flooring materials and the measurements of an instrument to test flooring materials and its force attenuating capabilities using mathematical models to describe the signature and coefficients of the floor. The main contribution of the present work focus on the development of a mathematical fluid model for floors. The aim of the thesis was to analyze, compare different floor materials and to study the linear dynamics of falling impacts on floors. The impact of the hammer during a fall is captured by an accelerometer and response is collected using a picoscope. The collected data was analyzed using matlab least square method which is coded as per the fluid model. The finding from this thesis showed that the fluid model works with more elastic model but it doesn't work for rigid materials like wood. The importance of parameters like velocity, mass, energy loss and other coefficients of floor which influences the model during the impact of falling on floors were identified and a standardized testing method was set. © Published under licence by IOP Publishing Ltd.

  • 11.
    Rosén, Bengt-Göran
    et al.
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Dimkovski, Zlate
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Cabanettes, Frédéric
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Löfgren, Hans
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.
    Controlling variation of topography towards robust surface performance2010In: Proceedings of the 2nd International Conference on Surface Metrology: October 25-27, 2010, Worcester Polytechnic Institute, Worcester, MA, USA / [ed] Bergstrom T. et al., Worcester, USA: Worcester Polytechnic Institute , 2010, p. 43-51Conference paper (Refereed)
1 - 11 of 11
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