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  • 51.
    Asnafi, Nader
    et al.
    Sapa Technology, Finspång (and Vetlanda), Sweden .
    Widlund, Conny
    Håltagning vid hydroformning: material- och processparametrars inverkan på hålkvaliteten2000Rapport (Annet vitenskapelig)
  • 52.
    bergman, martin
    Örebro universitet, Akademin för naturvetenskap och teknik.
    Sinnenas Rum - Ytor för bastumiljö2010Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I denna rapport kan läsaren följa händelseförloppet med framtagningen av en fysisk mood-board med tillhörande grafisk manual. Läsaren kommer att få en allmän förståelse för hur det semantiska hos en produkt påverkar dess användare samt hur detta påverkar produktens resultat på marknaden. I projektet pressenteras en tämligen oanvänd metod som, kortfattat; syftar till att ta vara på en målgrupps specifika känslor om exempelvis en produkt för att göra denna mer optimerad. I detta projekt handlade det mer om att ta fram specifika strukturer vilka tillslut kom att leda till ett antal speciellt utvalda ytor och material åt företaget Tylö® AB. Materialet tillsammans med speciella ytor skall komma att skapa en mer elegant känsla i deras kommande sortiment. Metoden som används för att nå fram till resultatet heter Kansei Engineering.

  • 53.
    Berns, H.
    et al.
    Institut für Werkstofle, Ruhr-Universität Bochum, Bochum, Germany .
    Melander, A.
    lnstitutet för Metallforskning, Stockholm, Sweden .
    Weichert, D.
    Laboratoire de Mécanique de Lille, Lille, France .
    Asnafi, Nader
    lnstitutet för Metallforskning, Stockholm, Sweden .
    Broeckmann, C.
    Institut für Werkstofle, Ruhr-Universität Bochum, Bochum, Germany .
    Gross-Weege, A.
    Laboratoire de Mécanique de Lille, Lille, France .
    A new material for cold forging tools1998Inngår i: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 11, nr 3, s. 166-180Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new tool material for cold forging applications was developed using numerical simulation techniques (FEM) for the design and a powder metallurgical route (HIP) for the production. The basic idea was to find an optimized microstructure of the two phase material by simulating different distributions of hard particles within the metal matrix. On the micro-scale, loading was applied by a field of deformations which was obtained by a macroscopical simulation of a particular cold forming process in bolt making. A new double dispersion microstructure was found to show the best resistance against crack propagation. Specimens were produced by hot isostatic pressing. Afterwards the new material was tested in the laboratory. Wear resistance and bending strength of the double dispersive material are comparable to a standard dispersion material with the same volume fraction of particles, but fracture toughness is increased by about 30%. Testing the new material in bolt making showed that the life time of the tool is increased by a factor of 8.

  • 54.
    Edström, Daniel
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik. Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden.
    Sangiovanni, D. G.
    Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden; ICAMS, Ruhr-Universität Bochum, Bochum, Germany.
    Hultman, L.
    Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden.
    Petrov, I
    Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden; Frederick Seitz Materials Research Laboratory and the Materials Science Department, University of Illinois at Urbana-Champaign, Urbana IL, USA.
    Greene, J. E.
    Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden; Frederick Seitz Materials Research Laboratory and the Materials Science Department, University of Illinois at Urbana-Champaign, Urbana IL, USA; Materials Science Department, National Taiwan University of Science and Technology, Taipei, Taiwan.
    Chirita, V
    Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden.
    TiN film growth on misoriented TiN grains with simultaneous low-energy bombardment: Restructuring leading to epitaxy2019Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 688, artikkel-id UNSP 137380Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We perform large-scale molecular dynamics simulations of TiN deposition at 1200 K on TiN substrates consisting of under-stoichiometric (N/Ti = 0.86) misoriented grains. The energy of incoming Ti atoms is 2 eV and that of incoming N atoms is 10 eV. The simulations show that misoriented grains are reoriented during the early stages of growth, after which the film grows 001 epitaxially and is nearly stoichiometric. The grain reorientation coincides with an increase in film N/Ti ratio. As the grains reorient, additional nitrogen can no longer be accommodated, and the film composition becomes stoichiometric as the overlayer grows epitaxially.

  • 55.
    Ekengren, Jens
    Karlstads universitet, Avdelningen för maskin- och materialteknik.
    Estimating inclusion content in high performance steels2008Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Non-metallic inclusions in steel pose a major problem for the fatigue resistance, especially regarding fatigue at very long lives corresponding to low cyclic stress levels, as well as being detrimental to material toughness and polishability.

    The largest inclusions are quite rare, which makes conventional detection methods timeconsuming if reliable results are to be obtained. Based on surface scanning using light or electron microscopes, these methods provide results that have to be converted to reflect the statistical volume distribution of inclusions.

    Very high cycle fatigue (in the order of 109 cycles or more) using ultrasonic fatigue at 20 kHz has been found efficient at finding the largest inclusions in volumes of about 300 mm3 per specimen. The inclusions found at the fatigue initiation site can then been used to estimate the distribution of large inclusions using extreme value statistics.

    In this work, a new method for estimating the volume distribution of large inclusions is presented as well as a suggested ranking variable based on the volume distribution.

    Results from fatigue fractography and area scanning methods are compared to the endurance limit at 109 cycles for a number of batches from two high performance steels.

    In addition, the extreme value distributions of fatigue initiating inclusions in six high performace steels, produced by different routes, are presented. It is shown that all modes of the Generalized Extreme Values distribution can be found in different materials. This result shows that the assumption of mode I distribution, also known as Gumbel or Largest Extreme Value distribution, must be substantiated.

    Delarbeid
    1. Relating gigacycle fatigue to other methods in evaluating the inclusion distribution of a H13 tool steel
    Åpne denne publikasjonen i ny fane eller vindu >>Relating gigacycle fatigue to other methods in evaluating the inclusion distribution of a H13 tool steel
    2007 (engelsk)Inngår i: Fourth International Conference on Very High Cycle Fatigue (VHCF-4) / [ed] John E. Allison, J. Wayne Jones, James M. Larsen & Robert O. Ritchie, TMS (The Minerals, Metals & Materials Society) , 2007, s. 45-50Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Inclusions play a crucial role for the fatigue properties of high strength steel, but to find the largest inclusions by microscopy measurements large areas have to be examined.In this study ultrasonic gigacycle staircase fatigue testing has been used to find large inclusions in an H13 tool steel. The inclusions have been examined in SEM and their size distribution modeled using methods from extreme value statistics. The inclusion distribution obtained from the fatigue crack surfaces is compared to distributions acquired by microscopy study of cross sections as well as ultrasound immersion tank measurements and to the corresponding staircase fatigue data via the Murakami √Area model.It is shown that the fatigue method more effectively finds large inclusions than the other methods. It is also shown that the correlation between predictions of inclusion sizes by the √Area model from stress levels and fatigue initiating inclusions is weak forthis material.

    sted, utgiver, år, opplag, sider
    TMS (The Minerals, Metals & Materials Society), 2007
    Emneord
    non-metallic inclusion, steel, gigacycle fatigue
    HSV kategori
    Forskningsprogram
    Materialteknik
    Identifikatorer
    urn:nbn:se:oru:diva-39905 (URN)978-0-87339-704-9 (ISBN)
    Konferanse
    Fourth International Conference on Very High Cycle Fatigue (VHCF-4)
    Tilgjengelig fra: 2009-02-05 Laget: 2014-12-19 Sist oppdatert: 2017-10-17bibliografisk kontrollert
    2. Detecting large inclusions in steels: evaluating methods
    Åpne denne publikasjonen i ny fane eller vindu >>Detecting large inclusions in steels: evaluating methods
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    HSV kategori
    Identifikatorer
    urn:nbn:se:oru:diva-40114 (URN)
    Tilgjengelig fra: 2015-01-02 Laget: 2015-01-02 Sist oppdatert: 2017-10-17bibliografisk kontrollert
    3. Extreme value distributions of inclusions in six steels
    Åpne denne publikasjonen i ny fane eller vindu >>Extreme value distributions of inclusions in six steels
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    HSV kategori
    Identifikatorer
    urn:nbn:se:oru:diva-40117 (URN)
    Tilgjengelig fra: 2015-01-02 Laget: 2015-01-02 Sist oppdatert: 2017-10-17bibliografisk kontrollert
    4. Finding non-metallic inclusions in clean steel
    Åpne denne publikasjonen i ny fane eller vindu >>Finding non-metallic inclusions in clean steel
    2008 (engelsk)Rapport (Annet vitenskapelig)
    sted, utgiver, år, opplag, sider
    Karlstad: Karlstads universitet, 2008
    Serie
    Karlstad University Studies, ISSN 1403-8099 ; 2008:51
    HSV kategori
    Forskningsprogram
    Materialteknik
    Identifikatorer
    urn:nbn:se:oru:diva-39895 (URN)978-91-7063-208-2 (ISBN)
    Tilgjengelig fra: 2009-02-05 Laget: 2014-12-19 Sist oppdatert: 2017-10-17bibliografisk kontrollert
  • 56.
    Ekengren, Jens
    Örebro universitet, Institutionen för naturvetenskap och teknik. Karlstads universitet, Avdelningen för maskin- och materialteknik.
    Finding non-metallic inclusions in clean steel2008Rapport (Annet vitenskapelig)
  • 57.
    Ekengren, Jens
    Avdelningen för maskin- och materialteknik, Karlstads universitet, Karlstad, Sverige.
    Large and rare: An extreme values approach to estimating the distribution of large defects in high-performance steels2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The presence of different types of defects is an important reality for manufacturers and users of engineering materials. Generally, the defects are either considered to be the unwanted products of impurities in the raw materials or to have been introduced during the manufacturing process. In high-quality steel materials, such as tool steel, the defects are usually non-metallic inclusions such as oxides or sulfides.

    Traditional methods for purity control during standard manufacturing practice are usually based on the light optical microscopy scanning of polished surfaces and some statistical evaluation of the results. Yet, as the steel manufacturing process has improved, large defects have become increasingly rare. A major disadvantage of the traditional quality control methods is that the accuracy decreases proportionally to the increased rarity of the largest defects unless large areas are examined.

    However, the use of very high cycle fatigue to 109 cycles has been shown to be a powerful method to locate the largest defects in steel samples. The distribution of the located defects may then be modelled using extreme value statistics.

    This work presents new methods for determining the volume distribution of large defects in high-quality steels, based on ultrasonic fatigue and the Generalized Extreme Value (GEV) distribution. The methods have been developed and verified by extensive experimental testing, including over 400 fatigue test specimens. Further, a method for reducing the distributions into one single ranking variable has been proposed, as well as a way to estimate an ideal endurance strength at different life lengths using the observed defects and endurance limits. The methods can not only be used to discriminate between different materials made by different process routes, but also to differentiate between different batches of the same material.

    It is also shown that all modes of the GEV are to be found in different steel materials, thereby challenging a common assumption that the Gumbel distribution, a special case of the GEV, is the appropriate distribution choice when determining the distribution of defects.

    The new methods have been compared to traditional quality control methods used in common practice (surface scanning using LOM/SEM and ultrasound C-scan), and suggest a greater number of large defects present in the steel than could otherwise be detected.

    Delarbeid
    1. Relating gigacycle fatigue to other methods in evaluating the inclusion distribution of a H13 tool steel
    Åpne denne publikasjonen i ny fane eller vindu >>Relating gigacycle fatigue to other methods in evaluating the inclusion distribution of a H13 tool steel
    2007 (engelsk)Inngår i: Fourth International Conference on Very High Cycle Fatigue (VHCF-4) / [ed] John E. Allison, J. Wayne Jones, James M. Larsen & Robert O. Ritchie, TMS (The Minerals, Metals & Materials Society) , 2007, s. 45-50Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Inclusions play a crucial role for the fatigue properties of high strength steel, but to find the largest inclusions by microscopy measurements large areas have to be examined.In this study ultrasonic gigacycle staircase fatigue testing has been used to find large inclusions in an H13 tool steel. The inclusions have been examined in SEM and their size distribution modeled using methods from extreme value statistics. The inclusion distribution obtained from the fatigue crack surfaces is compared to distributions acquired by microscopy study of cross sections as well as ultrasound immersion tank measurements and to the corresponding staircase fatigue data via the Murakami √Area model.It is shown that the fatigue method more effectively finds large inclusions than the other methods. It is also shown that the correlation between predictions of inclusion sizes by the √Area model from stress levels and fatigue initiating inclusions is weak forthis material.

    sted, utgiver, år, opplag, sider
    TMS (The Minerals, Metals & Materials Society), 2007
    Emneord
    non-metallic inclusion, steel, gigacycle fatigue
    HSV kategori
    Forskningsprogram
    Materialteknik
    Identifikatorer
    urn:nbn:se:oru:diva-39905 (URN)978-0-87339-704-9 (ISBN)
    Konferanse
    Fourth International Conference on Very High Cycle Fatigue (VHCF-4)
    Tilgjengelig fra: 2009-02-05 Laget: 2014-12-19 Sist oppdatert: 2017-10-17bibliografisk kontrollert
    2. Detecting large inclusions in steels: evaluating methods
    Åpne denne publikasjonen i ny fane eller vindu >>Detecting large inclusions in steels: evaluating methods
    2009 (engelsk)Inngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 80, nr 11, s. 854-858Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The distributions of large non-metallic inclusions in two steel grades have been investigated using light optical microscopy, scanning electron microscopy and ultrasonic fatigue testing in the gigacycle range. The different methods have inherently different capabilities for finding inclusions in different size ranges. A measure of the distribution of large inclusions is proposed as the size S at which half of the fatigue specimens are expected to contain at least one inclusion of size S or larger, corresponding to 50% failure probability. Values of S are obtained using the volume distribution estimated by the three methods. Extrapolation from microscopy measurements on surfaces agree with fatigue fractography results regarding density of large inclusions, as measured by the proposed ranking variable S.

    sted, utgiver, år, opplag, sider
    Weinheim, Germany: Wiley-VCH Verlagsgesellschaft, 2009
    Emneord
    Inclusion distribution, steel, very high cycle fatigue
    HSV kategori
    Forskningsprogram
    Materialteknik
    Identifikatorer
    urn:nbn:se:oru:diva-39902 (URN)10.2374/SRI08SP156 (DOI)000272027100010 ()2-s2.0-73149120049 (Scopus ID)
    Merknad

    Vid tidpunkten för författarens licentiatseminarium, förelåg detta delarbete som manuskript. This paper was first published as a manuscript at time for the author's licentiate seminar.

    Tilgjengelig fra: 2009-02-05 Laget: 2014-12-19 Sist oppdatert: 2019-10-11bibliografisk kontrollert
    3. Assessment of strength and inclusions of tool steels in very high cycle fatigue
    Åpne denne publikasjonen i ny fane eller vindu >>Assessment of strength and inclusions of tool steels in very high cycle fatigue
    2009 (engelsk)Inngår i: Proceedings of the 8th International Tooling Conference, Vol 1 / [ed] P. Beiss, C. Broeckmann, S. Franke, B. Keysselitz, Aachen: Verlag Mainz, Wissenschaftsverlag , 2009Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Fatigue strength is an important material property for many tooling applications, particularly in high performance applications. The research in Very High Cycle Fatigue (VHCF) has demonstrated that the traditional fatigue limit may not be valid for many materials subjected to 107 or more load cycles. Presently, both materials data and mechanism knowledge is missing on VHCF applications, even though many components are run at these life lengths. The fatigue strength is commonly controlled by different defects initiating failure, as in well controlled laboratory experiments may be internal inclusions. In this paper VHCF experimental testing was accomplished by the use of ultrasonic fatigue testing run at 20 kHz allowing long life evaluation within reasonably short test time. Fatigue strength, failure mechanisms and inclusion content were accordingly assessed. Fatigue strength data on H13 tool steel are presented, as well as a statistical approach considering available defect distribution and load distribution in the critically stressed volume, important to both steel supplier and end-user.

    sted, utgiver, år, opplag, sider
    Aachen: Verlag Mainz, Wissenschaftsverlag, 2009
    Emneord
    very high cycle fatigue, tool steel, inclusion distribution
    HSV kategori
    Identifikatorer
    urn:nbn:se:oru:diva-39903 (URN)9783810793058 (ISBN)
    Konferanse
    8th International Tooling Conference (TOOL 09), Tool steels - deciding factor in worldwide production, Aachen University, Aachen, Germany, June 2-4, 2009
    Tilgjengelig fra: 2011-09-12 Laget: 2014-12-19 Sist oppdatert: 2019-10-11bibliografisk kontrollert
    4. Extreme value distributions of inclusions in six steels
    Åpne denne publikasjonen i ny fane eller vindu >>Extreme value distributions of inclusions in six steels
    2012 (engelsk)Inngår i: Extremes, ISSN 1386-1999, E-ISSN 1572-915X, Vol. 15, nr 2, s. 257-265Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    There is a prevailing assumption that the largest inclusions in steel volumes follows mode I of the Generalized Extreme Values (GEV) distribution. In this work, the GEV distributions of non-metallic inclusions in six different high performance steels, of different grades and processing routes, were investigated by means of fractography of inclusions causing failure in ultrasonic fatigue testing to one billion cycles and all three modes of the GEV were found for the different steel grades. Values of the shape parameter ξ of the GEV distribution as high as 0.51 (standard deviation 0.11) were found in one steel grade. Thus, the present results show that the assumption of GEV-I (Gumbel, LEVD) distribution has to be substantiated before being used to estimate the size of the largest inclusions.

    Emneord
    Extreme values; Non-metallic inclusions; Steel
    HSV kategori
    Forskningsprogram
    Maskinteknik
    Identifikatorer
    urn:nbn:se:oru:diva-39899 (URN)10.1007/s10687-011-0139-5 (DOI)000303585200006 ()2-s2.0-84860624529 (Scopus ID)
    Tilgjengelig fra: 2011-09-09 Laget: 2014-12-19 Sist oppdatert: 2019-10-11bibliografisk kontrollert
    5. Influence of life length on estimated defect distribution in a low defect steel material
    Åpne denne publikasjonen i ny fane eller vindu >>Influence of life length on estimated defect distribution in a low defect steel material
    2011 (engelsk)Inngår i: Proceedings of the Fifth International Conference on Very High Cycle Fatigue / [ed] C. Berger and H.-J. Christ, Berlin: Deutscher Verband für Materialforschung und -prüfung , 2011, s. 177-182Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    This paper reports on results of very high cycle fatigue tests on a steel with a relatively low number of defects per unit volume. Two series of newly designed dog-bone specimens, with low stress gradients, were tested at two constant stress levels, aiming at providing fatigue life lengths of 106–108 cycles and 107–109 cycles, respectively. Fatigue-initiating defects on the fracture surfaces were measured and the corresponding size distributions were analysed to investigate the influence of the elevated stress level needed to achieve shorter life lengths. The presented results indicate a difference between the distribution of initiating defects in the long and shorter life length test series. The main conclusion is that fixed stress level fatigue testing to life lengths around 107 cycles may be a suitable method to estimate the content of large defects in low defect steel materials, provided a suitable test specimen geometry with low stress gradients is used.

    sted, utgiver, år, opplag, sider
    Berlin: Deutscher Verband für Materialforschung und -prüfung, 2011
    Emneord
    Defect volume distribution, Extreme value statistics, Tool steel
    HSV kategori
    Identifikatorer
    urn:nbn:se:oru:diva-39900 (URN)978-3-9814516-0-3 (ISBN)
    Konferanse
    Fifth International Conference on Very High Cycle Fatigue, Berlin, Germany, June 28-30, 2011
    Tilgjengelig fra: 2011-09-09 Laget: 2014-12-19 Sist oppdatert: 2019-10-11bibliografisk kontrollert
    6. Estimating the volume distribution of large defects using Generalized Extreme Values
    Åpne denne publikasjonen i ny fane eller vindu >>Estimating the volume distribution of large defects using Generalized Extreme Values
    2011 (engelsk)Inngår i: Extremes, ISSN 1386-1999, E-ISSN 1572-915XArtikkel i tidsskrift (Annet vitenskapelig) Submitted
    Abstract [en]

    The presence of defects, such as oxides and other non-metallic inclusions, is an important factor in determining the properties of steels. Due to improvements in the manufacturing of high-quality steels, the amount of large defects has decreased and therefore it has become increasingly difficult to accurately determine their distribution using conventional methods. Previously, a method for estimating the distribution of large defects using a conversion from the Gumbel distribution has been presented. However, it has been shown that the Gumbel distribution is not always appropriate for modelling the sizes of the largest defects and that the Generalized Extreme Values (GEV) distribution should be used instead. In this work a more general method for the estimation of the total volume distribution of large defects isproposed, showing how the volume distribution may be calculated from the estimated parameters for the GEV distribution. The new method is applied to the results of a series of specimens made from high-quality tool steel tested in ultrasonic resonance fatigue. Possible methods for obtaining the confidence limits of thevolume distribution are also discussed.

    HSV kategori
    Identifikatorer
    urn:nbn:se:oru:diva-39901 (URN)
    Tilgjengelig fra: 2011-09-14 Laget: 2014-12-19 Sist oppdatert: 2019-10-25bibliografisk kontrollert
  • 58.
    Ekengren, Jens
    et al.
    Karlstads universitet.
    Bergström, Jens
    Karlstads universitet.
    Detecting large inclusions in steels: evaluating methodsManuskript (preprint) (Annet vitenskapelig)
  • 59.
    Ekengren, Jens
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Detecting large inclusions in steels: evaluating methods2009Inngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 80, nr 11, s. 854-858Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The distributions of large non-metallic inclusions in two steel grades have been investigated using light optical microscopy, scanning electron microscopy and ultrasonic fatigue testing in the gigacycle range. The different methods have inherently different capabilities for finding inclusions in different size ranges. A measure of the distribution of large inclusions is proposed as the size S at which half of the fatigue specimens are expected to contain at least one inclusion of size S or larger, corresponding to 50% failure probability. Values of S are obtained using the volume distribution estimated by the three methods. Extrapolation from microscopy measurements on surfaces agree with fatigue fractography results regarding density of large inclusions, as measured by the proposed ranking variable S.

  • 60.
    Ekengren, Jens
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Estimating the volume distribution of large defects using Generalized Extreme Values2011Inngår i: Extremes, ISSN 1386-1999, E-ISSN 1572-915XArtikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The presence of defects, such as oxides and other non-metallic inclusions, is an important factor in determining the properties of steels. Due to improvements in the manufacturing of high-quality steels, the amount of large defects has decreased and therefore it has become increasingly difficult to accurately determine their distribution using conventional methods. Previously, a method for estimating the distribution of large defects using a conversion from the Gumbel distribution has been presented. However, it has been shown that the Gumbel distribution is not always appropriate for modelling the sizes of the largest defects and that the Generalized Extreme Values (GEV) distribution should be used instead. In this work a more general method for the estimation of the total volume distribution of large defects isproposed, showing how the volume distribution may be calculated from the estimated parameters for the GEV distribution. The new method is applied to the results of a series of specimens made from high-quality tool steel tested in ultrasonic resonance fatigue. Possible methods for obtaining the confidence limits of thevolume distribution are also discussed.

  • 61.
    Ekengren, Jens
    et al.
    Karlstads universitet.
    Bergström, Jens
    Karlstads universitet.
    Extreme value distributions of inclusions in six steelsManuskript (preprint) (Annet vitenskapelig)
  • 62.
    Ekengren, Jens
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Extreme value distributions of inclusions in six steels2012Inngår i: Extremes, ISSN 1386-1999, E-ISSN 1572-915X, Vol. 15, nr 2, s. 257-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a prevailing assumption that the largest inclusions in steel volumes follows mode I of the Generalized Extreme Values (GEV) distribution. In this work, the GEV distributions of non-metallic inclusions in six different high performance steels, of different grades and processing routes, were investigated by means of fractography of inclusions causing failure in ultrasonic fatigue testing to one billion cycles and all three modes of the GEV were found for the different steel grades. Values of the shape parameter ξ of the GEV distribution as high as 0.51 (standard deviation 0.11) were found in one steel grade. Thus, the present results show that the assumption of GEV-I (Gumbel, LEVD) distribution has to be substantiated before being used to estimate the size of the largest inclusions.

  • 63.
    Ekengren, Jens
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Influence of life length on estimated defect distribution in a low defect steel material2011Inngår i: Proceedings of the Fifth International Conference on Very High Cycle Fatigue / [ed] C. Berger and H.-J. Christ, Berlin: Deutscher Verband für Materialforschung und -prüfung , 2011, s. 177-182Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper reports on results of very high cycle fatigue tests on a steel with a relatively low number of defects per unit volume. Two series of newly designed dog-bone specimens, with low stress gradients, were tested at two constant stress levels, aiming at providing fatigue life lengths of 106–108 cycles and 107–109 cycles, respectively. Fatigue-initiating defects on the fracture surfaces were measured and the corresponding size distributions were analysed to investigate the influence of the elevated stress level needed to achieve shorter life lengths. The presented results indicate a difference between the distribution of initiating defects in the long and shorter life length test series. The main conclusion is that fixed stress level fatigue testing to life lengths around 107 cycles may be a suitable method to estimate the content of large defects in low defect steel materials, provided a suitable test specimen geometry with low stress gradients is used.

  • 64.
    Ekengren, Jens
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Kazymyrovych, Vitaliy
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Assessment of strength and inclusions of tool steels in very high cycle fatigue2009Inngår i: Proceedings of the 8th International Tooling Conference, Vol 1 / [ed] P. Beiss, C. Broeckmann, S. Franke, B. Keysselitz, Aachen: Verlag Mainz, Wissenschaftsverlag , 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fatigue strength is an important material property for many tooling applications, particularly in high performance applications. The research in Very High Cycle Fatigue (VHCF) has demonstrated that the traditional fatigue limit may not be valid for many materials subjected to 107 or more load cycles. Presently, both materials data and mechanism knowledge is missing on VHCF applications, even though many components are run at these life lengths. The fatigue strength is commonly controlled by different defects initiating failure, as in well controlled laboratory experiments may be internal inclusions. In this paper VHCF experimental testing was accomplished by the use of ultrasonic fatigue testing run at 20 kHz allowing long life evaluation within reasonably short test time. Fatigue strength, failure mechanisms and inclusion content were accordingly assessed. Fatigue strength data on H13 tool steel are presented, as well as a statistical approach considering available defect distribution and load distribution in the critically stressed volume, important to both steel supplier and end-user.

  • 65.
    Ekengren, Jens
    et al.
    Karlstads universitet, Avdelningen för maskin- och materialteknik.
    Kazymyrovych, Vitaliy
    Karlstads universitet, Avdelningen för maskin- och materialteknik.
    Burman, Christer
    Karlstads universitet, Avdelningen för maskin- och materialteknik.
    Bergström, Jens
    Karlstads universitet, Avdelningen för maskin- och materialteknik.
    Relating gigacycle fatigue to other methods in evaluating the inclusion distribution of a H13 tool steel2007Inngår i: Fourth International Conference on Very High Cycle Fatigue (VHCF-4) / [ed] John E. Allison, J. Wayne Jones, James M. Larsen & Robert O. Ritchie, TMS (The Minerals, Metals & Materials Society) , 2007, s. 45-50Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Inclusions play a crucial role for the fatigue properties of high strength steel, but to find the largest inclusions by microscopy measurements large areas have to be examined.In this study ultrasonic gigacycle staircase fatigue testing has been used to find large inclusions in an H13 tool steel. The inclusions have been examined in SEM and their size distribution modeled using methods from extreme value statistics. The inclusion distribution obtained from the fatigue crack surfaces is compared to distributions acquired by microscopy study of cross sections as well as ultrasound immersion tank measurements and to the corresponding staircase fatigue data via the Murakami √Area model.It is shown that the fatigue method more effectively finds large inclusions than the other methods. It is also shown that the correlation between predictions of inclusion sizes by the √Area model from stress levels and fatigue initiating inclusions is weak forthis material.

  • 66.
    Ekstrand, Gunnar
    et al.
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Asnafi, Nader
    Industrial Development Centre, Olofström, Sweden.
    On testing of the stiffness and the dent resistance of autobody panels1998Inngår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 19, nr 4, s. 145-156Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this study has been to establish a platform which can be used in future attempts to set up at least a reasonable (scientifically based) company standard for stiffness and dent resistance tests. Stiffness and dent testing equipment was developed and used in this investigation. This equipment, which is mounted in a mechanical testing machine, consists chiefly of three parts: a table, on which the panel is placed; a fixture, which is used to restrain the panel; and a punch, with which the panel centre is loaded. Two different punches are used: a flat-headed punch of diameter 100 mm in the stiffness tests and a hemispherical punch of diameter 25 mm in the dent resistance tests. The boundary conditions play a significant role in the stiffness and the dent resistance measurements. The largest stiffness is obtained with the boundary configuration case I, whilst the boundary configuration case IV yields the smallest stiffness. The attained experimental results show that the thicker the sheet thickness at the panel centre, the greater will be the panel stiffness. The greater the panel radii (the more severe the springback), the smaller the stiffness. The experimental results show too that the larger the initial yield strength, the higher is the dent resistance. The thicker the sheet, the higher is the dent resistance. The purpose of this study has been to establish a platform which can be used in future attempts to set up at least a reasonable (scientifically based) company standard for stiffness and dent resistance tests. Stiffness and dent testing equipment was developed and used in this investigation. This equipment, which is mounted in a mechanical testing machine, consists chiefly of three parts: a table, on which the panel is placed; a fixture, which is used to restrain the panel; and a punch, with which the panel centre is loaded. Two different punches are used: a flat-headed punch of diameter 100 mm in the stiffness tests and a hemispherical punch of diameter 25 mm in the dent resistance tests. The boundary conditions play a significant role in the stiffness and the dent resistance measurements. The largest stiffness is obtained with the boundary configuration case I, whilst the boundary configuration case IV yields the smallest stiffness. The attained experimental results show that the thicker the sheet thickness at the panel centre, the greater will be the panel stiffness. The greater the panel radii (the more severe the springback), the smaller the stiffness. The experimental results show too that the larger the initial yield strength, the higher is the dent resistance. The thicker the sheet, the higher is the dent resistance.

  • 67. Ekstrand, Gunnar
    et al.
    Asnafi, Nader
    Industrial Development Centre, Olofström, Sweden.
    On Testing of the Stiffness and the Dent Resistance of Autobody Panels1998Rapport (Annet vitenskapelig)
  • 68. Ekstrand, Gunnar
    et al.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden .
    Hammam, Tag
    Process Monitoring and Sheet Metal Formability in Pressing of Box-Shaped Components1997Rapport (Annet vitenskapelig)
  • 69.
    El-Amine, Karim
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik. Suzuki Garphyttan AB, Garphyttan, Sweden.
    Larsson, Joakim
    Örebro universitet, Institutionen för naturvetenskap och teknik. Department of Mechanical Engineering.
    Pejryd, Lars
    Örebro universitet, Institutionen för naturvetenskap och teknik. Department of Mechanical Engineering.
    Experimental comparison of roller die and conventional wire drawing2018Inngår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 257, s. 7-14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, the application of roller dies as an alternative to conventional dies in the wire drawing process – claimed in earlier works to offer many advantageous improvements – is evaluated. To this end, experimental procedures using a single stage drawing machine were conducted, drawing low and medium carbon steel wires using both roller dies and conventional dies. The two reduction processes were compared with respect to drawing force and the resulting wire temperature. Also the mechanical properties of the drawn wires were investigated. The obtained results have not shown any large differences between the two processes, and the main improvement using the roller die method was a better wire surface. This advantage was counteracted with downsides including higher wire temperature and lower strain at fracture.

    Moreover, a formula to theoretically calculate drawing force for the conventional drawing process was modified and used to calculate drawing force for the two reduction steps in the roller die cassette. The results showed that the proportion of inhomogeneous deformation was much higher in the rolling process as compared to the conventional process.

    In view of the outcomes in this work, the alternative of drawing wire through roller dies was not considered to be offering more improvements with respect to the conventional drawing method.

  • 70.
    Flyktman, Stefan
    et al.
    Örebro universitet, Akademin för naturvetenskap och teknik.
    Johansson, Jan
    Örebro universitet, Akademin för naturvetenskap och teknik.
    Tillverkningsmetoders påverkan på en transmissions vikt och tillverkningskostnad2010Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Volvo Powertrain, VPT, i Köping tillverkar idag växellådor för tunga fordon. Till medeltunga fordon köper Volvo växellådor från bland annat underleverantören ZF. Volvo vill undersöka scenariot att ta fram AMT - växellådor för medeltunga fordon. I-shift modellen AT2412, som är dimensionerad för en max belastning på 2400 Nm och anpassad för tunga lastbilar, skulle kunna fungera även i medeltunga fordon men är då överdimensionerad och onödigt tung.

    Med tanke på kommande utvecklingsprojekt behöver Volvo öka sin kunskap hur val av tillverkningsmetoder påverkar vikt och tillverkningskostnader. Det behövs för att öka förståelsen för hur olika prioriteringar ska göras med avseende på vikt och tillverkningskostnader. Examensarbetets syfte var att ge denna förståelse för hur olika tillverkningsprocesser påverkar en transmissions utformning med avseende på mått och vikt utifrån ett givet momentområde. Målet med examensarbetet var att påvisa samband mellan valet av tillverkningsmetoder för enskilda artiklar och hur mycket det kan påverka den kompletta transmissionens vikt samt tillverkningskostnad. Arbetet var avgränsat till att analysera modifierade kugghjul i baslådan.

    Första delen av arbetet bestod av att dimensionera nya kugghjul anpassade för max belastning på 1600 Nm, detta utifrån samma produktionsupplägg som för befintliga kugghjul som återfinns i bland annat AT2412. Den andra delen bestod av att ta fram faktorer för hur olika tillverkningsmetoder påverkar dimensioneringen och för varje enskilt kugghjul beräkna vikt och tillverkningskostnad då åtta kombinationer av tillverkningsmetoder används. Avslutningsvis gjordes en summering för att visa vilka varianter som ger en optimal växellåda utifrån minimal vikt respektive minimal tillverkningskostnad.

    Resultatet visar att valet av tillverkningsmetoder leder till att vikten på kugghjulen kan reduceras mer eller mindre. Generellt visar beräkningarna att kugghjul som slipas, kulpenas och manganfosfateras får lägst vikt och blir dyrast att producera. Lägsta tillverkningskostnad uppnås genom att vissa tillverkningsprocesser som kulpening och manganfosfatering utesluts men detta måste då kompenseras med ökad kuggbredd vilket leder till högre vikt.

    Om VPT väljer att ta fram en ny variant av I-shift där kugghjulen är dimensionerade för 1600Nm så kan växellådan göras 6-11 kg lättare och tillverkningskostnaderna för kugghjulen kan minska med ca 10 procent.

  • 71.
    Fürsatz, Marian
    et al.
    Department of Physics, Chemistry, and Biology, Linköping University, Linköping, Sweden.
    Skog, Mårten
    Department of Physics, Chemistry and Biology, Linkopings universitet, Linköping, Sweden.
    Sivlér, Petter
    Department of Physics, Chemistry and Biology, Linkopings universitet, Linköping, Sweden.
    Palm, Eleonor
    Örebro universitet, Institutionen för medicinska vetenskaper.
    Aronsson, Christopher
    Department of Physics, Chemistry and Biology, Linkopings universitet, Linköping, Sweden.
    Skallberg, Andreas
    Department of Physics, Chemistry and Biology, Linkopings universitet, Linköping, Sweden.
    Greczynski, Grzegorz
    Department of Physics, Linköping University, Linkoping, Sweden.
    Khalaf, Hazem
    Örebro universitet, Institutionen för medicinska vetenskaper.
    Bengtsson, Torbjörn
    Örebro universitet, Institutionen för medicinska vetenskaper.
    Aili, Daniel
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Functionalization of bacterial cellulose wound dressings with the antimicrobial peptide ε-poly-L-Lysine2018Inngår i: Biomedical Materials, ISSN 1748-6041, E-ISSN 1748-605X, Vol. 13, artikkel-id 025014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wound dressings based on bacterial cellulose (BC) can form a soft and conformable protective layer that can stimulate wound healing while preventing bacteria from entering the wound. Bacteria already present in the wound can, however, thrive in the moist environment created by the BC dressing which can aggravate the healing process. Possibilities to render the BC antimicrobial without affecting the beneficial structural and mechanical properties of the material would hence be highly attractive. Here we present methods for functionalization of BC with ε-Poly-L-Lysine (ε-PLL), a non-toxic biopolymer with broad-spectrum antimicrobial activity. Low molecular weight ε-PLL was cross-linked in pristine BC membranes and to carboxymethyl cellulose (CMC) functionalized BC using carbodiimide chemistry. The functionalization of BC with ε-PLL inhibited growth of S. epidermidis on the membranes but did not affect the cytocompatibility to cultured human fibroblasts as compared to native BC. The functionalization had no significant effects on the nanofibrous structure and mechanical properties of the BC. The possibility to functionalize BC with ε-PLL is a promising, green and versatile approach to improve the performance of BC in wound care and other biomedical applications.

  • 72. Gunnarsson, Lars
    et al.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden .
    In-Process Control of Blank Holder Force in Axisymmetric Deep Drawing with Degressive Gas Springs1996Konferansepaper (Annet vitenskapelig)
  • 73.
    Gunnarsson, Lars
    et al.
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Schedin, Erik
    Swedish Institute for Metals Research, Stockholm, Sweden.
    In-process control of blank holder force in axi-symmetric deep drawing with degressive gas springs1998Inngår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 73, nr 1-3, s. 89-96Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new blank-holder system with degressive gas springs has been developed and evaluated for axi-symmetric deep drawing. In contrast to most published works in this field, in which hydraulic systems are utilized, the new system is integrated with the tool body instead of with the press, the advantage with this approach being that the system is independent of press facilities. The new system consists of inter-connected active and passive gas springs, moving parallel during forming. With the new system, degressive, constant and progressive blank-holder force (BHF) trajectories can be obtained. The BHF-trajectories were pre-determined with a specially developed software. Two materials, an ordinary deep drawing steel and a high-strength rephosphorized steel, have been analysed. The thickness was 0.7 mm and a water emulsion was used as lubricant. The blank holder force, punch force, total force and the separation of the blank holder (wrinkle detection) were recorded continuously during the pressing operation. With a degressive BHF-trajectory the process window between fracture and wrinkling in axi-symmetric deep drawing is larger compared to those obtained with constant and progressive trajectories, and also, the LDR is higher.

  • 74.
    Gåård, Anders
    et al.
    Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Karlstads universitet, Karlstad, Sweden.
    Karlsson, Patrik
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Krakhmalev, Pavel
    Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Karlstads universitet, Karlstad, Sweden.
    Broitman, Esteban
    Tunnfilmsfysik, Linköpings universitet, Linköping, Sweden.
    Nano-scale friction of multi-phase powder metallurgy tool steels2015Inngår i: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 1119, s. 70-74Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Friction is a fundamental phenomenon in tribology involving complex mechanisms between thecontacting surfaces. Measurements of friction are often made using devices with substantially largercontact area than dimensions corresponding to microstructural features of the materials. Hence, for multi-phase materials,influence of particular microstructural constituents is not resolved. In the present work, a tribometerwith a contact area in the nano-scale range was used to map friction for different types of tool steelswith different chemical- and phase composition. Owing to the small tip radius, frictionalcharacteristics of primary carbides and the steel matrix were measured and compared. Dependingon chemical composition, a difference was observed where the coefficient of friction wasapproximately twice higher for the steel possessing highest coefficient of friction, including bothcarbides and the steel matrix.

  • 75. Hadad, Rabie
    et al.
    Lindgren, Patrik
    Jonsson, Mikael
    Lundberg, Sven-Erik
    Örebro universitet, Institutionen för teknik.
    A Theoretical / Empirical study of void closure in heavy plate hot rolling of tool steel2009Inngår i: Metallurgy and New Materials Researches / Cercetari metalurgice, si de noi materiale, ISSN 1221-5503, Vol. 17, nr 1, s. 9-26Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    By the introduction of TOOLOX®, SSAB in Oxelösund has turned into a new market segment, including heavier sizes and dramatically increased requirements on inner quality of the plate. To be able to determine the minimum reduction from slab to finished plate with acceptable inner quality, a study was made, to evaluate the minimum reduction for a given requirement of inner quality. By experimental rolling in the heavy plate mill in Oxelösund it has been proven that more than 40 % total reduction is necessary for total closure of voids under the geometrical deformation conditions in that mill. The total reduction is more important than the geometrical rolling conditions, and heavy pass reductions are favourable for void closure. The closure of internal defects can be improved by cooling the surface of the slabs.

  • 76. Hammam, Tag
    et al.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden .
    Forming an aluminium semi-pipe with flexform technique (die-forming): a comparison with conventional technique1992Rapport (Annet vitenskapelig)
    Abstract [en]

    The purpose of the present work is to compare flexform technique (die-forming) with conventional pressing technique by analyzing the strain state of the components after forming. A double curved component was formed with a die tool in flexforming and with conventional technique. The sheet material was the aluminium alloy AA6061-O, according to the American standard, with thickness of 1mm. This study shows that the flexforming (die-forming) leads to a higher local thinning. This is due to the fact that the flange, in flexforming (die-forming), is locked at the final stage of forming, after which the component is fully formed. This means that the final stage in flexforming (die-forming) is a stretching operation. The level of the strains is highly dependent on the chosen process parameters. This is valid for both flexforming and conventional forming. There is, however, a natural difference between conventional forming and flexforming (die-forming), which leads to different strain distributions. A difference, which can not be diminished by changing the process parameters of the geometry.

  • 77.
    Hekkanen, Mikko
    Örebro universitet, Akademin för naturvetenskap och teknik.
    Inclusion Rating of Clean Steels2009Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

     

    This report covers a study concerning the methods that are available for determining the cleanness level for steels. No outstanding method is available for rating clean steels, when clean steel is defined as free of fatigue initiating inclusions. Fatigue strength is to a large extent dependant of the biggest inclusion size in the stressed volume. Examples of methods that can be used for finding and testing material for the presence of big inclusions is reported.

     

  • 78.
    Hekkanen, Mikko
    Örebro universitet, Institutionen för teknik.
    Inclusion Rating of Clean Steels2009Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    The main part of this work has been a literature survey, reviewing scientifical reports forinformation on how steel cleanness is evaluated today, and also how the steel cleanness is related tothe fatigue performance of clean steels.

  • 79.
    Huang, Shuo
    et al.
    Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm, Sweden.
    Holmstrom, Erik
    Sandvik Coromant R&D, Stockholm, Sweden.
    Eriksson, Olle
    Örebro universitet, Institutionen för naturvetenskap och teknik. Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Uppsala, Sweden.
    Vitos, Levente
    Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm, Sweden; Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Uppsala, Sweden; Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, Hungary.
    Mapping the magnetic transition temperatures for medium- and high-entropy alloys2018Inngår i: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 95, s. 80-84Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tailorable magnetic state near room temperature is very promising for several technological, including magnetocaloric applications. Here using first-principle alloy theory, we determine the Curie temperature (T-C) of a number of equiatomic medium- and high-entropy alloys with solid solution phases. All calculations are performed at the computed lattice parameters, which are in line with the available experimental data. Theory predicts a large crystal structure dependence of T-C, which explains the experimental observations under specified conditions. The sensitivity of the magnetic state to the crystal lattice is reflected by the magnetic exchange interactions entering the Heisenberg Hamiltonian. The analysis of the effect of composition on T-C allows researchers to explore chemistry-dependent trends and design new multi-component alloys with pre-assigned magnetic properties.

  • 80.
    Jana, S.
    et al.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden; Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, India.
    Panda, S. K.
    Centre de Physique Théorique, Ecole Polytechnique, CNRS UMR 7644, Université Paris-Saclay, Palaiseau, France; Department of Physics, Bennett University, Uttar Pradesh, India.
    Phuyal, D.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Pal, B.
    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, India.
    Mukherjee, S.
    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, India.
    Dutta, A.
    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, India.
    Kumar, P. Anil
    Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
    Hedlund, D.
    Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
    Schött, J.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Thunström, P.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Kvashnin, Y.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Rensmo, H.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Kamalakar, M. Venkata
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Segre, Carlo U.
    CSRRI & Department of Physics, Illinois Institute of Technology, Chicago Illinois, USA.
    Svedlindh, P.
    Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
    Gunnarsson, K.
    Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
    Biermann, S.
    Centre de Physique Théorique, Ecole Polytechnique, CNRS UMR 7644, Université Paris-Saclay, Palaiseau, France; Collège de France, Paris, France.
    Eriksson, Olle
    Örebro universitet, Institutionen för naturvetenskap och teknik. Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Karis, O.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Sarma, D. D.
    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, India.
    Charge disproportionate antiferromagnetism at the verge of the insulator-metal transition in doped LaFeO32019Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, nr 7, artikkel-id 075106Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We explore the effects of electron doping in lanthanum ferrite, LaFeO3 by doping Mo at the Fe sites. Based on magnetic, transport, scanning tunneling spectroscopy, and x-ray photoelectron spectroscopy measurements, we find that the large gap, charge-transfer, antiferromagnetic (AFM) insulator LaFeO3 becomes a small gap AFM band insulator at low Mo doping. With increasing doping concentration, Mo states, which appear around the Fermi level, is broadened and become gapless at a critical doping of 20%. Using a combination of calculations based on density functional theory plus Hubbard U (DFT+U) and x-ray absorption spectroscopy measurements, we find that the system shows charge disproportionation (CD) in Fe ions at 25% Mo doping, where two distinct Fe sites, having Fe2+ and Fe3+ nominal charge states appear. A local breathing-type lattice distortion induces the charge disproportionation at the Fe site without destroying the antiferromagnetic order. Our combined experimental and theoretical investigations establish that the Fe states form a CD antiferromagnet at 25% Mo doping, which remains insulating, while the appearance of Mo states around the Fermi level is showing an indication towards the insulator-metal transition.

  • 81.
    Jansson, Anton
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Pejryd, Lars
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Characterisation of carbon fibre-reinforced polyamide manufactured by selective laser sintering2016Inngår i: Additive Manufacturing, ISSN 2214-8604, Vol. 9, s. 7-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polymers and reinforced plastics are employed in various load-bearing applications, from household objects to aerospace products. These materials are light, strong, and relatively cheap but can be difficult to form into complex geometries. However, the development of additive manufacturing processes has made it easier to manufacture reinforced plastics in complex shapes. The aim of this work was to study the internal features and mechanical properties of carbon fibre-reinforced polyamide (CF/PA12) fabricated with the additive manufacturing technique of selective laser sintering. The test specimens were studied using computed tomography to analyse the internal geometry, and the material proved to be highly porous. Moreover, the test specimens revealed an internal layered structure, which was found to have a great effect on the tensile properties of the material. The results highlight that there is room for further optimisation of the manufacturing parameters for CF/PA12, because the layered structure makes it challenging to design end user parts with acceptable mechanical properties.

  • 82.
    Jansson, Anton
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Pejryd, Lars
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Surface vs Truss lattice networks, benefits and limitations2018Inngår i: NAFEMS nordic: Exploring the Design Freedom of Additive Manufacturing through Simulation, NAFEMS , 2018, s. 217-218Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The use of additive manufacturing is growing rapidly among industries within many different fields of fabrication. The benefits of applying additive manufacturing can be many and an application that have received special interest is the ability to design lightweight components. Lightweight components can be fabricated with additive manufacturing with the use of lattices that have a high stiffness to weight ratio and topology optimised, complex, designs. The most commonly used lattices today are based on trusses, however, there is also the possibility to generate lattices based around continuous surfaces. In this study, the properties of the popular body-centred-cubic lattice are compared the properties of the lesser known Schwartz diamond surface lattice. The mechanical compression properties, the fabrication processes, and the possibilities of the lattices are discussed and analysed.

  • 83.
    Jarl, Magnus
    et al.
    Örebro universitet, Institutionen för teknik.
    Axelsson, Fredrik
    Wear of dies, measured and calculated by the process control system in a drawing machine2009Inngår i: Wire Journal International, ISSN 0277-4275, Vol. 42, nr 10, s. 80-83Artikkel i tidsskrift (Fagfellevurdert)
  • 84.
    Jarl, Magnus
    et al.
    Örebro universitet, Institutionen för teknik.
    Överstam, Henrik
    Örebro universitet, Institutionen för teknik.
    Simulation of temperatures in the wiredrawing process2008Inngår i: Wire Journal International, ISSN 0277-4275, Vol. 41, nr 2, s. 150-155Artikkel i tidsskrift (Fagfellevurdert)
  • 85.
    Karlberg, Magnus
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Löfstrand, Magnus
    Luleå University of Technology, Luleå, Sweden.
    Marjavaara, Daniel
    LKAB, Kiruna, Sweden.
    Lundström, T. Staffan
    Luleå University of Technology, Luleå, Sweden.
    Simulation driven processing function development, offering and operation2012Inngår i: ASME 2012 International Mechanical Engineering Congress and Exposition, Proceedings (IMECE2012), New York, USA: ASME Press, 2012, Vol. 3, s. 1561-1572Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In today’s industry, functional provision is becoming more and more important, necessitating increased simulation support. In this paper, the objective is to present a modeling and simulation approach for simulation-driven design (SDD) to support function development. The scope of this paper is simulation support for developing hardware equipment used in processing industry. The research is founded on industrial needs identified through two parallel interview-based studies in the Swedish process industry. Both companies explore doing business with functional products rather than hardware, in scenarios where the responsibility for and availability of the functions may remain with the service provider. One as-is and one future (to-be) scenario are presented. A decomposition of a general processing function (applicable to both companies) describes how the companies transfer machine input to output specifications. The decomposition includes customer and provider value and the paper demonstrates, as part of the results and based on the SDD approach, how that value may be increased through evaluation and prioritization. Additionally, the SDD approach shows that it is possible to identify a set of solutions which meet the specified requirements, supporting evaluation and prioritization of business offers and activities.

  • 86.
    Karlsson, Lennart
    et al.
    The Faste Laboratory, Division of Computer Aided Design, Luleå University of Technology, Luleå, Sweden.
    Pahkamaa, Andreas
    Division of Computer Aided Design, Luleå University of Technology, Luleå, Sweden.
    Karlberg, Magnus
    The Faste Laboratory, Division of Computer Aided Design, Luleå University of Technology, Luleå, Sweden.
    Löfstrand, Magnus
    The Faste Laboratory, Division of Computer Aided Design, Luleå University of Technology, Luleå, Sweden.
    Goldak, John
    Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, Canada .
    Pavasson, Jonas
    The Faste Laboratory, Division of Computer Aided Design, Luleå University of Technology, Luleå, Sweden.
    Mechanics of materials and structures: a simulation-driven design approach2011Inngår i: Journal of Mechanics of Materials and Structures, ISSN 1559-3959, E-ISSN 2157-5428, Vol. 6, nr 1-4, s. 277-301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Engineering product development has developed considerably over the past decade. In order for industry to keep up with continuously changing requirements, it is necessary to develop new and innovative simulation methods. However, few tools and methods for simulation-driven design have been applied in industrial settings and proven to actually drive the development and selection of the ideal solution. Such tools, based on fundamental equations, are the focus of this paper. In this paper the work is based on two cases of mechanics of materials and structures: welding and rotor dynamical simulations. These two examples of simulation-driven design indicate that a larger design space can be explored and that more possible solutions can be evaluated. Therefore, the approach improves the probability of innovations and finding optimal solutions. A calibrated block dumping approach can be used to increase the efficiency of welding simulations when many simulations are required.

  • 87.
    Karlsson, Patrik
    Örebro universitet, Institutionen för naturvetenskap och teknik. Avdelningen för maskin- och materialteknik, Karlstads universitet, Karlstad, Sverige.
    The early stage of galling2012Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In sheet metal forming (SMF) of materials such as stainless steels there is a major problem with transfer and accumulation of sheet material to the metal forming tool surface. The problem is known as galling; a kind of severe adhesive wear, which results in severe scratching of produced parts. In this thesis, galling observed in contacts between tool steels and stainless steel sheets under lubricated sliding conditions was studied, focusing on the early stage of galling. It was found that changes in friction cannot be used as galling indicator in the early stage of galling because transfer and accumulation of sheet material happens even though friction is low and stable. The progression of galling is influenced by tool steel damage occurring around the tool steel hard phases caused by sheet material flow, which results in formation of wear-induced galling initiation sites. A correlation between the critical contact pressure to galling and sheet material proof stress was found. Galling happened at lower pressures for sheet material with lower proof stress possibly due to easier sheet material flow, resulting in quicker tool damage. Material transfer and tool steel damage were delayed for tool steels comprising homogenously distributed, small and high hard phases. Additionally, the galling resistance was higher for tool steels with higher hardness due to decreased tool steel damage. In a comparison between observations of the worn tool surfaces after wear tests and calculations in FEM it was found that material transfer did not take place at regions with highest contact pressures but at regions with highest plastic strains. The results obtained in this thesis indicate that tool steel damage and sheet material flow occurring in the contact during sliding are important factors influencing galling.

  • 88.
    Karlsson, Patrik
    Karlstad university, Karlstad, Sweden.
    The influence of tool steel microstructure on galling2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In sheet metal forming (SMF) of materials such as stainless steels there is a major problem with transfer and accumulation of sheet material to the metal forming tool surface. The problem is known as galling; a sort of severe adhesive wear, which results in severe scratching of produced parts. In this thesis, the overall aim was to gain knowledge of the influence of tool steel microstructure on galling initiation under sliding conditions. It was discovered that material transfer and tool steel damage caused by sheet material flow creating wear-induced galling initiation sites occurred in the early stage of galling. The galling resistance was higher for tool steels with higher matrix hardness due to better resistance to tool steel damage. Initial friction and critical contact pressure to galling was influenced by the strength of the sheet material. Material transfer happened at low pressures and the friction value was high in a case of sheet materials with lower proof strength, possibly due to the sheet contact against the tool steel matrix resulting in high adhesion and quicker tool damage. It was demonstrated that, in addition to hardness of the tool steel matrix and sheet material proof strength, tool steel microstructural features like size, shape, distribution and height of hard phases are important parameters influencing galling. Tool steels comprising homogeneously distributed, small and high hard phases better prevented the contact between sheet material and the tool steel matrix. Thus, a metal to metal contact with high friction was more efficiently avoided, which resulted in better tool performance.

     

  • 89.
    Karlsson, Patrik
    et al.
    Karlstad University, Karlstad, Sweden.
    Eriksson, Jenny
    Dalarna University, Falun, Sweden.
    Gåård, Anders
    Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Karlstad University, Karlstad, Sweden.
    Olsson, Mikael
    Dalarna University, Falun, Sweden.
    Bergström, Jens
    Karlstad University, Karlstad, Sweden.
    Galling resistance evaluation of tool steels by two different laboratory test methods for sheet metal forming2012Inngår i: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 24, nr 6, s. 263-272Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adhesive accumulation of work material on the tool surface is today a major problem in many sheet metal-forming applications. Different laboratory test methods are used to investigate galling with respect to different tool materials, lubricants and process conditions. In the present study, the galling resistance of a modern nitrogen-alloyed powder metallurgy tool steel and an conventional ingot cast D2 type tool steel was evaluated under lubricated sliding against ferritic stainless steel sheets using a commercial pin-on-disc (POD) and an in-house made slider-on-flat-surface (SOFS) tribotester. The investigated tool steels ranked similarly in terms of galling resistanc in both test methods. However, sliding distances to galling were longer for the SOFS equipment due to continuous sliding on new lubricated sheet surface. Best performance was demonstrated by the powder metallurgy tool steel treated to 65 HRC. Differences in friction behaviour and galling initiation were analysed on the basis of the two different working conditions, i.e. open (SOFS) and closed (POD) tribosystems. Copyright © 2012 John Wiley & Sons, Ltd.

  • 90.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Influence of tool steel microstructure on friction and initial material transfer2014Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 319, nr 1-2, s. 12-18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An investigation was conducted to study the influence of tool steel microstructure on initial material transfer and friction. Two different powder metallurgy tool steels and an ingot cast tool material were tested in dry sliding against 1.4301, 1.4162, Domex 355 MC and Domex 700 MC sheet materials. It was found that tool steel hard phase heights influence initial material transfer and friction. The coefficient of friction increased with decreasing tool steel hard phase heights at 50 N normal load and initial material transfer occurred around protruding hard phases. At higher load of 500 N the sheet material adhered to both the tool steel matrix and hard phases. Coefficient of friction decreased with increasing proof strength of the sheet material at 500 N normal load.

  • 91.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Galling Resistance and Wear Mechanisms for Cold Work Tool Steels in Lubricated Sliding Against High Strength Stainless Steel Sheets2010Inngår i: Tribology of manufacturing processes: Proceedings of the 4th International Conference on Tribology in Manufacturing Processes (ICTMP 2010), Volume 2 / [ed] Eric Felder; Pierre Montmitonnet, Paris: Presses de l'Ecole des mines , 2010, s. 673-682Konferansepaper (Fagfellevurdert)
  • 92.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Galling resistance and wear mechanisms for cold-work tool steels in lubricated sliding against high strength stainless steel sheets2012Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 286-287, s. 92-97Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tool damage in sheet metal forming of stainless steel is of high concern for the forming industry. In the present work, ingot cast AISI D2 and advanced powder metallurgy tool steel (PM) cold-work tool steels were evaluated and ranked regarding wear mechanisms and galling resistance. Wear tests were performed using a slider-on-flat-surface (SOFS) tribometer in sliding against austenitic–ferritic (duplex) stainless steel sheets at different contact pressures in lubricated conditions. The best galling resistance was observed for the nitrogen alloyed PM tool steels. Abrasive scratching of the tool surfaces and transfer of sheet material due to adhesive wear were the main metal forming tool surface damage mechanisms. By increasing the hardness of one PM sheet metal forming tool grade, the galling resistance was enhanced.

  • 93.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Berhe-Larsson, Johanna
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Influence of tool steel hard phase orientation and shape on galling2014Inngår i: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 966-96, s. 249-258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conventionally manufactured cold work tool steel is often used in sheet metal forming as die material. Due to the forging process, the as-cast network structure of carbides is broken into elongated particles. Depending on the tool cross-section, the orientation and shape of carbides in the active tool surface is different. In the present research, the influence of tool steel hard phase orientation and shape on galling was investigated. D2 type tool steel was cut in three different orientations and tested in lubricated sliding conditions against AISI 304 austenitic stainless steel. Tests were performed using a Slider-On-Flat-Surface and galling was detected by changes in friction and post-test microscopy. The lubricant was Castrol FST8 using 5 g/m2 sheet material. Results showed a strong correlation between sliding distance to galling and tool steel hard phase orientation and shape at low loads, whereas high load contact resulted in early galling in all cases. Material transfer was observed mainly to the tool steel matrix. The worst performance was observed for specimens cut so that the tool steel hard phase, M7C3 carbides in the D2 steel, were oriented along the sliding direction, which resulted in longer open tool matrix areas contacting the sheet material.

  • 94.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Influence of work material proof stress and tool steel microstructure on galling initiation and critical contact pressure2013Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 60, s. 104-110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    EN 1.4301 (austenitic), EN 1.4509 (ferritic), EN 1.4162 (duplex) and EN 1.4310 C1000 (metastable austenitic) stainless steels were tested in lubricated sliding against an ingot cast EN X153WCrMoV12 and powder metallurgy nitrogen alloyed Uddeholm Vancron 40 tool steels to reveal critical to galling contact pressure, Pcr. The calculated Pcr were higher for steels with higher strength. At P>Pcr, due to plastic flow of sheet material, the tool is damaged substantially and wear-induced matrix damage causes rapid galling initiation. At P<Pcr, galling was not observed. The powder metallurgy tool steel was more resistant to galling against all tested stainless steels. Better performance was associated with fine and homogeneously distributed hard phases preventing intensive wear of the tool steel matrix.

  • 95.
    Karlsson, Patrik
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Pejryd, Lars
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Oikonomou, Christos
    Uddeholms AB, Hagfors, Sweden.
    Factors Influencing Mechanical Properties of Additive Manufactured Thin-Walled Parts2017Inngår i: Euro PM2017 Congress Proceedings, European Powder Metallurgy Association (EPMA) , 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    By using the Additive Manufacturing (AM) method it is possible to manufacture components with thin-walled sections and complex geometry. However, it is not clear when the surface becomes the strength limiting factor on thin-walled sections in the components or if the thickness of the components is reduced. Also, the microstructure of AM produced specimens may be heterogeneous and it is not clear how the build direction influence the strength of thin section components. In the present study, the influence of component thickness, surface roughness and build direction on the strength of AM produced components were investigated. Test specimens were manufactured using EOS M290 3D-printer and EN 1.2709 maraging steel powder. To investigate when the part thickness, surface and built orientation becomes the strength limiting factors tensile testing using thin samples built in both  horizontal and vertical build orientation with thicknesses ranging from 0.2 mm to 4 mm was performed. Results on strength limiting factors are discussed.

  • 96.
    Karlsson, Sofie
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Reducera omställningstiden i ytmonteringslinan Panasonic på Stoneridge Electronics AB2014Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Omställningstiden i ytmonteringslinan Panasonic på Stoneridge Electronics AB ansågs vara en bidragande orsak till att maskinernas fulla kapacitet inte kunde utnyttjas. Syftet med det här examensarbetet var därför att analysera omställningssituationen och med analysen som grund reducera omställningstiden med hjälp av SMED-metoden samt ta fram förbättringsförslag gällande arbetet i övrigt.

    Förutom SMED har tidsmätningar, observationer samt litteraturstudier legat till grund för reduceringen av omställningstid samt förbättringsförslagen som innebär bl.a. sekventiell omställning av conveyersystemet i ytmonteringslinan samt tydligare instruktioner och mer visuell styrning, enligt teorin om Lean.

    Ett fortsatt arbete i form av uppdatering av arbetsinstruktioner och själva utförandet av omställningen är exempel på typen av ständiga förbättringar som företaget redan idag jobbar aktivt med.

  • 97.
    Korin, Christer
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Ristinmaa, Matti
    Div Solid Mech, Lund University, Lund, Sweden.
    Saabye Ottosen, Niels
    Div Solid Mech, Lund University, Lund, Sweden.
    Analytical prediction of package collapse loads: consideration to windows in the package2014Inngår i: Nordic Pulp & Paper Research Journal, ISSN, ISSN 0283-2631, Vol. 29, nr 4, s. 717-724Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Windows in a package is a common way to promote the product. The possibility to predict the collapse load for these types of cartonboard packages is considered. It is shown that reliable estimates of the collapse loads can be obtained by a very simple approach. This approach is a straightforward generalization of the proposal by Ristinmaa et al. (2012): for a side that contains a window, one simply removes the strip of the package side in the loading direction that contains the window. The calculation procedure is described in detail. As a test of the calculation procedure, comparisons are made with experimentally obtained collapse loads for packages containing windows with different sizes and locations.

  • 98.
    Liljengren, Magnus
    et al.
    Olofström School of Automotive Stamping, Olofström, Sweden.
    Kjellson, Kenneth
    Volvo Cars Body Components, Olofström, Sweden.
    Johansson, Tuve
    Volvo Cars Body Components, Olofström, Sweden.
    Asnafi, Nader
    Volvo Cars Body Components, Olofström, Sweden.
    Die materials, hardening methods and surface coatings for forming of high, extra high and ultra high strength steel sheets (HSS/EHSS/UHSS)2006Inngår i: Drawing the Things to Come: Trends and Advances in Sheet Metal Forming: Proceedings: IDDRG International Deep Drawing Research Group 2006 Conference / [ed] Abel D. Santos, A. Barata da Rocha, Inst. de Engenharia Mecânica e Gestão Industrial , 2006, s. 597-604Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    During the past years, large efforts have been made at Volvo Cars to establish a scientific and systematic approach to selection of die materials, hardening methods and surface treatments/coatings. These efforts were initiated, since both new higher strength sheet materials and new die materials with better performance were introduced. Both these higher strength sheet materials and higher performance die materials needed to be industrialized. 

    Volvo cars transferred to a so-called Dry Presshop several years ago. This means that only the rust protection oil applied by the material supplier to the sheet prior to delivery is allowed as the stamping lubricant. No additional lubricant can be accepted. This transfer is done with regard to environmental improvement and a lean production philosophy. "Trouble-shooting" (reduction of abrasive and adhesive die wear) by using additional lubrication is therefore not possible anymore.

    In this investigation 1.20 and 1.95 mm thick uncoated and hot-dip galvanized sheets of DP600, DP800 and DP1000 were tested. The wear behaviour of the die materials Sverker 21 (D2), Calmax, Sleipner, Weartec, Vanadis 6 and Vancron 40 were studied. Uncoated, plasma-nitrided, PVD-coated (CrN and TiAlN) versions of dies made in the above-mentioned materials were tested.

    The tests were carried out both in laboratory in a U-bend test equipment and in real stamping production. Based on the results obtained in laboratory and production tests, guidelines were established for selection of die materials and surface treatments in stamping of DP600, DP800 and DP1000. These guidelines are described in the present paper.

  • 99.
    Morales, Luis Orlando
    et al.
    Department of Forest Products Technology, School of Chemical Technology, Aalto University, Aalto, Finland.
    Iakovlev, Mikhail
    Department of Forest Products Technology, School of Chemical Technology, Aalto University, Aalto, Finland.
    Martin-Sampedro, Raquel
    Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria INIA, Madrid, Spain.
    Rahikainen, Jenni L.
    VTT Technical Research Centre of Finland, Finland.
    Laine, Janne
    Department of Forest Products Technology, School of Chemical Technology, Aalto University, Aalto, Finland.
    van Heiningen, Adriaan
    Department of Forest Products Technology, School of Chemical Technology, Aalto University, Aalto, Finland; Department of Chemical and Biological Engineering, University of Maine, Orono, USA.
    Rojas, Orlando J.
    Department of Forest Products Technology, School of Chemical Technology, Aalto University, Aalto, Finland; Departments of Forest Biomaterials and Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, USA.
    Effects of residual lignin and heteropolysaccharides on the bioconversion of softwood lignocellulose nanofibrils after SO2-ethanol-water fractionation2014Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 161, s. 55-62Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The amount of residual lignin and hemicelluloses in softwood fibers was systematically varied by SO2-ethanol–water fractionation for integrated biorefinery with nanomaterial and biofuel production. On the basis of their low energy demand in mechanical processing, the fibers were deconstructed to lignocellulose nanofibrils (LCNF) and used as substrate for bioconversion. The effect of LCNF composition on saccharification via multicomponent enzymes was investigated at different loadings. LCNF digestibility was compared with the enzyme activity measured with a quartz crystal microbalance. LCNF hydrolysis rate gradually decreased with lignin and hemicellulose concentration, both of which limited enzyme accessibility. Enzyme inhibition resulted from non-productive binding of proteins onto lignin. Near complete LCNF hydrolysis was achieved, even at high lignin and hemicellulose content. Sugar yields for LCNF were higher than those for precursor SEW fibers, highlighting the benefits of high surface area in LCNF.

  • 100.
    Nieves, P.
    et al.
    ICCRAM, International Research Center in Critical Raw Materials and Advanced Industrial Technologies, Universidad de Burgos, Burgos, Spain.
    Arapan, S.
    ICCRAM, International Research Center in Critical Raw Materials and Advanced Industrial Technologies, Universidad de Burgos, Burgos, Spain; VSB Tech Univ Ostrava, IT4Innovations, Ostrava, Czech Republic.
    Maudes-Raedo, J.
    Department of Civil Engineering, Universidad de Burgos, Burgos, Spain.
    Marticorena-Sánchez, R.
    Department of Civil Engineering, Universidad de Burgos, Burgos, Spain.
    Del Brio, N. L.
    ICCRAM, International Research Center in Critical Raw Materials and Advanced Industrial Technologies, Universidad de Burgos, Burgos, Spain.
    Kovacs, A.
    Department for Integrated Sensor Systems, Danube University Krems, Lower Austria, Krems, Austria.
    Echevarria-Bonet, C.
    BCMaterials, Basque Centre for Materials, Applications and Nanostructures, UPV/EHU Science Park, Leioa, Spain.
    Salazar, D.
    BCMaterials, Basque Centre for Materials, Applications and Nanostructures, UPV/EHU Science Park, Leioa, Spain.
    Weischenberg, J.
    Department of Materials and Geosciences, TU Darmstadt, Darmstadt, Germany.
    Zhang, H.
    Department of Materials and Geosciences, TU Darmstadt, Darmstadt, Germany.
    Vekilova, O. Yu
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Serrano-Lopez, R.
    ICCRAM, International Research Center in Critical Raw Materials and Advanced Industrial Technologies, Universidad de Burgos, Burgos, Spain.
    Barandiaran, J. M.
    BCMaterials, Basque Centre for Materials, Applications and Nanostructures, UPV/EHU Science Park, Leioa, Spain.
    Skokov, K.
    Department of Materials and Geosciences, TU Darmstadt, Darmstadt, Germany.
    Gutfleisch, O.
    Department of Materials and Geosciences, TU Darmstadt, Darmstadt, Germany.
    Eriksson, Olle
    Örebro universitet, Institutionen för naturvetenskap och teknik. Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Herper, H. C.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Schrefl, T.
    Department for Integrated Sensor Systems, Danube University Krems, Lower Austria, Krems, Austria.
    Cuesta-López, S.
    ICCRAM, International Research Center in Critical Raw Materials and Advanced Industrial Technologies, Universidad de Burgos, Burgos, Spain.
    Database of novel magnetic materials for high-performance permanent magnet development2019Inngår i: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 168, s. 188-202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes the open Novamag database that has been developed for the design of novel Rare-Earth free/lean permanent magnets. Its main features as software technologies, friendly graphical user interface, advanced search mode, plotting tool and available data are explained in detail. Following the philosophy and standards of Materials Genome Initiative, it contains significant results of novel magnetic phases with high magnetocrystalline anisotropy obtained by three computational high-throughput screening approaches based on a crystal structure prediction method using an Adaptive Genetic Algorithm, tetragonally distortion of cubic phases and tuning known phases by doping. Additionally, it also includes theoretical and experimental data about fundamental magnetic material properties such as magnetic moments, magnetocrystalline anisotropy energy, exchange parameters, Curie temperature, domain wall width, exchange stiffness, coercivity and maximum energy product, that can be used in the study and design of new promising high-performance Rare-Earth free/lean permanent magnets. The results therein contained might provide some insights into the ongoing debate about the theoretical performance limits beyond Rare-Earth based magnets. Finally, some general strategies are discussed to design possible experimental routes for exploring most promising theoretical novel materials found in the database.

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