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Löfgren, H. (2018). A first order friction model for lubricated sheet metal forming. Theoretical and Applied Mechanics Letters, 8(1), 57-61
Open this publication in new window or tab >>A first order friction model for lubricated sheet metal forming
2018 (English)In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 8, no 1, p. 57-61Article in journal (Refereed) Published
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

Place, publisher, year, edition, pages
Melville, NY: American Institute of Physics (AIP), 2018
Keywords
Friction model, Lubrication, Sheet metal forming
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:hh:diva-38007 (URN)10.1016/j.taml.2018.01.002 (DOI)000437223900011 ()2-s2.0-85049335252 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , PV08-0041
Available from: 2018-09-17 Created: 2018-09-17 Last updated: 2018-09-17Bibliographically approved
Philip, R. & Löfgren, H. (2018). Experimental Verification of an Instrument to Test Flooring Materials. In: IOP Conference Series: Materials Science and Engineering. Paper presented at International Conference on Advances in Materials and Manufacturing Applications 2017, IConAMMA 2017, 17-19 August, 2017. Bristol: Institute of Physics Publishing (IOPP), 310(1), Article ID 012121.
Open this publication in new window or tab >>Experimental Verification of an Instrument to Test Flooring Materials
2018 (English)In: IOP Conference Series: Materials Science and Engineering, Bristol: Institute of Physics Publishing (IOPP), 2018, Vol. 310, no 1, article id 012121Conference paper, Published 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.

Place, publisher, year, edition, pages
Bristol: Institute of Physics Publishing (IOPP), 2018
Series
IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X ; 310
Keywords
coefficients of the floor, Fluid model, least square method, linear dynamics, Matlab, Building materials, Energy dissipation, Least squares approximations, Manufacture, Different floors, Elastic modeling, Experimental verification, Flooring materials, Fluid modeling, Least square methods, Standardized testing, Floors
National Category
Materials Engineering
Identifiers
urn:nbn:se:hh:diva-38746 (URN)10.1088/1757-899X/310/1/012121 (DOI)000446072000121 ()2-s2.0-85043698814 (Scopus ID)
Conference
International Conference on Advances in Materials and Manufacturing Applications 2017, IConAMMA 2017, 17-19 August, 2017
Available from: 2019-01-11 Created: 2019-01-11 Last updated: 2019-01-11Bibliographically approved
Gåård, A., Löfgren, H., Nilsson, B. & Hallbäck, N. (2017). Införandet av Computer Based Mathematics (CBM) i ingenjörsutbildningar. In: : . Paper presented at 6:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar, Chalmers tekniska högskola, 22 november – 23 november 2017.
Open this publication in new window or tab >>Införandet av Computer Based Mathematics (CBM) i ingenjörsutbildningar
2017 (Swedish)Conference paper, Published 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. 

National Category
Pedagogy
Identifiers
urn:nbn:se:hh:diva-38041 (URN)
Conference
6:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar, Chalmers tekniska högskola, 22 november – 23 november 2017
Available from: 2018-09-23 Created: 2018-09-23 Last updated: 2018-10-31Bibliographically approved
Löfgren, H. B. (2012). A solution to the hydrodynamic lubrication of a circular point contact sliding over a flat surface with cavitation [Letter to the editor]. Theoretical and Applied Mechanics Letters, 2(3), Article ID 032004.
Open this publication in new window or tab >>A solution to the hydrodynamic lubrication of a circular point contact sliding over a flat surface with cavitation
2012 (English)In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 2, no 3, article id 032004Article in journal, Letter (Refereed) Published
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.

Place, publisher, year, edition, pages
Melville, NY: American Institute of Physics (AIP), 2012
Keywords
Reynolds equation, analytical solution, cavitation, point contact
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:hh:diva-17792 (URN)10.1063/2.1203204 (DOI)
Funder
Swedish Foundation for Strategic Research
Available from: 2012-05-31 Created: 2012-05-31 Last updated: 2018-01-12Bibliographically approved
Dimkovski, Z., Cabanettes, F., Löfgren, H., Anderberg, C., Ohlsson, R. & Rosén, B.-G. (2012). Optimisation of Cylinder Liner Surface Finish by Slide Honing. Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, 226(4), 575-584
Open this publication in new window or tab >>Optimisation of Cylinder Liner Surface Finish by Slide Honing
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2012 (English)In: 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) Published
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.

Place, publisher, year, edition, pages
London: Mechanical Engineering Publ., 2012
Keywords
3D characterization, diamond honing, liner surface finish, mixed lubrication simulation
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hh:diva-14645 (URN)10.1177/0954405410396154 (DOI)000305481600001 ()2-s2.0-84860231449 (Scopus ID)
Available from: 2011-03-25 Created: 2011-03-25 Last updated: 2018-03-23Bibliographically approved
Cabanettes, F., Löfgren, H. B. & Rosén, B.-G. (2011). Evaluation of manufacturing processes for cam/roller contact. Paper presented at The 4th Swedish Production Symposium 2011 (SPS'11), Lund University, Sweden, 3 - 5 May 2011.
Open this publication in new window or tab >>Evaluation of manufacturing processes for cam/roller contact
2011 (English)Conference paper, Published paper (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:hh:diva-16339 (URN)
Conference
The 4th Swedish Production Symposium 2011 (SPS'11), Lund University, Sweden, 3 - 5 May 2011
Available from: 2011-09-26 Created: 2011-09-26 Last updated: 2018-01-12Bibliographically approved
Dimkovski, Z., Anderberg, C., Cabanettes, F., Löfgren, H. & Rosén, B.-G. (2011). Influence of Different Cylinder Liner Surfaces on Their Performance with the Twin Land Oil Control Ring in a Car Engine. In: Proceedings of the 13th International Conference on Metrology and Properties of Engineering Surfaces. Paper presented at The 13th International Conference on Metrology and Properties of Engineering Surfaces, Met & Props 2011, 12-15 April 2011, Twickenham Stadium, London, UK.
Open this publication in new window or tab >>Influence of Different Cylinder Liner Surfaces on Their Performance with the Twin Land Oil Control Ring in a Car Engine
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2011 (English)In: Proceedings of the 13th International Conference on Metrology and Properties of Engineering Surfaces, 2011Conference paper, Published paper (Refereed)
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hh:diva-14647 (URN)
Conference
The 13th International Conference on Metrology and Properties of Engineering Surfaces, Met & Props 2011, 12-15 April 2011, Twickenham Stadium, London, UK
Available from: 2011-03-25 Created: 2011-03-25 Last updated: 2018-03-23Bibliographically approved
Cabanettes, F., Löfgren, H. B. & Rosén, B.-G. (2011). The impact of manufacturing processes on Automotive Cam/Roller Contact. Paper presented at The 13th International Conference on Metrology and Properties of Engineering Surfaces, 12-15 April 2011, Twickenham Stadium, UK.
Open this publication in new window or tab >>The impact of manufacturing processes on Automotive Cam/Roller Contact
2011 (English)Conference paper, Published paper (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:hh:diva-16338 (URN)
Conference
The 13th International Conference on Metrology and Properties of Engineering Surfaces, 12-15 April 2011, Twickenham Stadium, UK
Available from: 2011-09-26 Created: 2011-09-26 Last updated: 2018-01-12Bibliographically approved
Rosén, B.-G., Dimkovski, Z., Cabanettes, F. & Löfgren, H. (2010). Controlling variation of topography towards robust surface performance. In: Bergstrom T. et al. (Ed.), Proceedings of the 2nd International Conference on Surface Metrology: October 25-27, 2010, Worcester Polytechnic Institute, Worcester, MA, USA. Paper presented at 2nd International Conference on Surface Metrology, Worcester, MA, USA, October 25-27, 2010 (pp. 43-51). Worcester, USA: Worcester Polytechnic Institute
Open this publication in new window or tab >>Controlling variation of topography towards robust surface performance
2010 (English)In: 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, Published paper (Refereed)
Place, publisher, year, edition, pages
Worcester, USA: Worcester Polytechnic Institute, 2010
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:hh:diva-16360 (URN)978-1-4507-4290-0 (ISBN)
Conference
2nd International Conference on Surface Metrology, Worcester, MA, USA, October 25-27, 2010
Available from: 2011-09-27 Created: 2011-09-27 Last updated: 2016-08-15Bibliographically approved
Bååth, L. & Löfgren, H. (2008). Ny teknik för avisning av vindkraftsvingar. Halmstad: Halmstad University
Open this publication in new window or tab >>Ny teknik för avisning av vindkraftsvingar
2008 (Swedish)Report (Other academic)
Alternative title[en]
New Technologies for de-icing Wind Turbines
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.

Abstract [sv]

Denna rapport presenterar resultatet av en förstudie om tekniker för avisning av vindkraftverk. Rapporten presenterar och diskuterar möjliga metoder och tekniker för att antingen värma vattendroppar till över fryspunkten, eller smälta is som har bildats på vingen. Problematiken för vingar på vindkraftverk skiljer sig markant från nedisning av flygplansvingar i att: (1) vingar på vindkraftverk tillbringar all sin tid i den delen av atmosfären där risken för nedisning är som störst; och (2) hastigheten för vingen mot luft varierar med avstånd från rotationscentrum medan den är konstant över vingen på ett flygplan. Formen på vingen på ett vindkraftverk varierar också från toppen in till centrum för att kompensera för variationen av relativ hastighet mot luften.Rapporten koncentreras på isbildning inom temperaturintervallet -10°C – 0°C och droppstorlekar av 1- 10 μm. Nedisning sker även vid mycket lägre temperaturer, men då sker troligen isbildningen direkt från vattenånga.

Vi drar följande slutsatser från vår studie:

  • Formen på vingen, speciellt vid kontaktytan mot gasflödet, kan ha betydelse för nedisning.
  • Nano-strukturen av ytan på vingen kan troligen konstrueras så att vattendropparna får enminimal kontaktyta mot vingen.

Vår förstudie visar dessutom:

  • Mikrovågor är alltför ineffektiva för att värma rent vatten eller smälta is. Tekniker för direktstrålning av mikrovågor mot vatten eller is på vingar bör således inte vidare utvecklas.
  • Millimetervågor är tillräckligt effektiva, men generationen av vågor på så höga frekvenser ärtroligen alltför ineffektiv för att detta ska vara en möjlig väg framåt.
  • Infrarött ljus är mycket effektivt för att värma vattendroppar eller smälta is och bör undersökasvidare.
  • Värmeledning är också effektivt och bör utvecklas. En robust och effektiv metod kan vara attvärma vingytan med mikrovågor så att kontakten mot den varma ytan smälter isen.

Vår förstudie visar att problematiken med undvikande av isbildning på, eller avisning av, vindkraftsverk inte har sitt svar i en enda teknik. Formen på vingen och strukturen på dess yta kan spela en viktig roll i förhållandena för isbildning. Båda dessa variabler kan behöva varieras beroende på latitud och atmosfäriskt klimat. Ytstrukturen måste troligen också variera över vingytan, både längs med vingen och tvärs, för att optimera för de lokala förhållandena. Dessutom kan smältning av is medelst värmning av vingytan vara en viktig extra möjlighet för att undvika effektförluster.Mer forskning är nödvändig, men vi sammanfattar att det största intresset just nu är att studera flödet av droppar över vingen som funktion av tvärsnittsytans form och kontakten mellan vingytan som funktion av ytstrukturen (t.ex. Lotus effekten).Denna rapport är resultatet av ett förstudieprojekt. Vi ämnar nu fortsätta med ett djupare forskningsprojekt som koncentreras på formen och ytstrukturen enligt vad som framkommit av vår analys och våra datorsimuleringar.

Place, publisher, year, edition, pages
Halmstad: Halmstad University, 2008. p. 54
Series
Vindforsk tillämpade programmet ; V-238
Keywords
De-icing, Wind turbines
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-3629 (URN)
Projects
Project 30988-1/V-238
Available from: 2009-12-21 Created: 2009-12-17 Last updated: 2017-11-29Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0292-893X

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