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  • 1.
    Bergström, Per
    et al.
    Mid Sweden Univ, Dept Chem Engn, Holmgatan 10, SE-85170 Sundsvall, Sweden.
    Hossain, Md Shakhawath
    Department of Chemical Engineering and FSCN, Mid Sweden University, Holmgatan 10, SE 85170 Sundsvall, Sweden.
    Uesaka, Tetsu
    Department of Chemical Engineering and FSCN, Mid Sweden University, Holmgatan 10, SE 85170 Sundsvall, Sweden.
    Scaling behaviour of strength of 3D-, semi-flexible-, cross-linked fibre network2019Ingår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 166, s. 68-74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Anisotropic, semi-flexible, cross-linked, random fibre networks are ubiquitous both in nature and in a wide variety of industrial materials. Modelling mechanical properties of such networks have been done extensively in terms of criticality, mechanical stability, and scaling of network stiffnesses with structural parameters, such as density. However, strength of the network has received much less attention. In this work we have constructed 3D-planar fibre networks where fibres are, more or less, oriented in the inplane direction, and we have investigated the scaling of network strength with density. Instead of modelling fibres as 1D element (e.g., a beam element with stretching, bending and/or shear stiffnesses), we have treated fibres as a 3D-entity by considering the features like twisting stiffness, transverse stiffness, and finite cross-link (or bond) strength in different deformation modes. We have reconfirmed the previous results of elastic modulus in the literature that, with increasing density, the network modulus indeed undergoes a transition from bending-dominated deformation to stretching-dominated with continuously varying scaling exponent. Network strength, on the other hand, scales with density with a constant exponent, i.e., showing no obvious transition phenomena. Using material parameters for wood fibres, we have found that the predicted results for stiffness and strength agree very well with experimental data of fibre networks of varying densities reported in the literature.

  • 2.
    Bjälkefur Seroka, Sofia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Roth, Emelie
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Bergentz, Anna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Thufvesson Retzner, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Green, Madeleine
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Söderqvist, Åsa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Riskklassificering av fiberområde i Bollstafjärden2016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I detta projekt har ett fiberområde i Bollstafjärden i Västernorrland undersökts. Fiberområdet består av en fiberbank och fiberrika sediment. Trä- och cellulosafibrer har tillsammans med kemikalier släppts ut från pappers- och massaindustri vilket gett upphov till fiberområden. Kemikaliernas farlighet samt risk för spridning och upptag i näringsväven utgör ett miljöhot. Syftet med projektet var att undersöka och klassificera fiberområdet med hjälp av en modell som tagits fram av Golder Associates på uppdrag av Länsstyrelsen i Västernorrland. Modellen bygger på Naturvårdsverkets Metodik för Inventering av Förorenade Områden (MIFO) och är den första av sitt slag varmed det också ingår i syftet att utvärdera denna. Volymen för fiberbanken beräknades för att få en uppfattning om dess storlek samt för att den ingår i modellen.

    Fiberbankens volym beräknades i programvaran ArcGIS till 197 143 m3. Volymen kan jämföras med en simbassäng (50x25 meter) som har ett djup på 158 meter. Den beräknade volymen ansågs vara mycket osäker eftersom det fanns för lite mätdata att tillgå, vilket innebar att beräkningsmetoderna i ArcGIS inte fungerade optimalt.

    Genom att fylla i modellens parametrar riskklassificerades fiberområdet till klass 1C, ”särskilt stor risk”, på en skala från 1-4. Riskklassificeringar används för att kun- na jämföra förorenade områden med varandra och för att få en uppfattning om vilka områden som ska prioriteras vid eventuella åtgärder.

    Modellen validerades genom att ändra parametrarna inom ett rimligt intervall samt se hur den påverkades då inget parametervärde angavs. Då värden som innebar störst risk användes på ett flertal parametrar erhölls högsta riskklass 1A. De parametrar som enskilt påverkade riskklassen var ”sammanvägda spridningsförutsättningar” och ”avstånd till närmaste bostadshus”. Det är anmärkningsvärt att en dubblering eller hal- vering av volym fiberbank och fiberrika sediment inte resulterade i en förändring av riskklass. Under arbetet med modellen visade det sig att fiberområdet kunde riskklas- sificeras utan information om dess volym.

    Modellen ansågs vara användarvänlig men hade en del brister så som otillräckligt definierade svarsalternativ för en del parametrar. Viss information upplevdes som svår- tillgänglig men är förmodligen enklare att hitta för handläggare vid länsstyrelser. 

  • 3.
    Carlsson, Jenny
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Heldin, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Isaksson, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Investigating tool engagement in groundwood pulping: finite element modelling and in-situ observations at the microscale2019Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    With industrial groundwood pulping processes relying on carefully designed grit surfaces being developed for commercial use, it is increasingly important to understand the mechanisms occurring in the contact between wood and tool. We present a methodology to experimentally and numerically analyse the effect of different tool geometries on the groundwood pulping defibration process. Using a combination of high-resolution experimental and numerical methods, including finite element (FE) models, digital volume correlation (DVC) of synchrotron radiation-based X-ray computed tomography (CT) of initial grinding and lab-scale grinding experiments, this paper aims to study such mechanisms. Three different asperity geometries were studied in FE simulations and in grinding of wood from Norway spruce. We found a good correlation between strains obtained from FE models and strains calculated using DVC from stacks of CT images of initial grinding. We also correlate the strains obtained from numerical models to the integrity of the separated fibres in lab-scale grinding experiments. In conclusion, we found that, by modifying the asperity geometries, it is, to some extent, possible to control the underlying mechanisms, enabling development of better tools in terms of efficiency, quality of the fibres and stability of the groundwood pulping process.

  • 4.
    Chinga-Carrasco, Gary
    et al.
    Paper and Fibre Research Institute (PFI), Norway.
    Miettinen, Arttu
    Department of Physics, University of Jyväskylä, Finland.
    Luengo Hendriks, Cris L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Centrum för bildanalys. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Gamstedt, E. Kristofer
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Kataja, Markku
    Department of Physics, University of Jyväskylä, Finland.
    Structural Characterisation of Kraft Pulp Fibres and Their Nanofibrillated Materials for Biodegradable Composite Applications2011Ingår i: Nanocomposites and Polymers with Analytical Methods / [ed] Cuppoletti, John, InTech , 2011, s. 243-260Kapitel i bok, del av antologi (Refereegranskat)
  • 5.
    Heldin, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Designing grinding tools to control and understand fibre release in groundwood pulping2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Mechanical pulping is a very energy demanding process in which only a fraction of the energy is used for the actual separation of wood fibres. The rest of the energy is lost, partly in damaging already separated fibres and partly as heat during viscoelastic deformation of the wood. Groundwood pulping is one of the major mechanical pulping processes. In this process, a piece of wood is pressed against a rotating grinding stone. The stone surface has traditionally been made of grinding particles fused to a vitrified matrix. Though the process is close to 200 years old, the detailed mechanisms of the interactions between the grinding particles and the wood surface are still not fully understood. The random nature of the grinding stones combined with the heterogeneous nature of wood creates a stochastic process that is difficult to study in detail. This work utilizes well-defined tools, that facilitate testing and analysis, to increase the understanding of the tool-wood-interaction. In-situ tomography experiments were performed with such well-defined tools, to study the deformations and strains induced in the wood as the tool asperities engage the wood surface. Numerical simulations were used to study the influence of asperity shape, and to show how the induced strains promote intercellular cracks and fibre separation. Several well-defined tool surfaces were designed and tested in a newly developed lab-scale grinding equipment, to study their performance in terms of energy consumption and the quality of the produced fibres. It was shown that the well-defined grinding surfaces, with asperities the same size as a fibre diameter, can be designed both to achieve drastically lower energy consumption compared with that of traditional stones and to produce long and undamaged fibres. This thesis shows that it is possible to design future tools that can help reducing the energy consumption in industrial pulping.

    Delarbeten
    1. Initiation of wood defibration in groundwood pulping, single asperity indentation and scratching
    Öppna denna publikation i ny flik eller fönster >>Initiation of wood defibration in groundwood pulping, single asperity indentation and scratching
    2016 (Engelska)Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, nr 3, s. 401-406Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    To understand how the energy requirements of the mechanical pulping process can be reduced, the fundamental mechanisms behind fiber separation in Norway spruce were studied experimentally and analytically. Single tip scratching in heated water was used to reproduce initial defibration mechanisms found industrially. The resulting scratches were then compared with surfaces ground in a real industrial process. Moreover, the mechanical behavior of the wood microstructure was monitored with X-ray computed microtomography as a single hard tip was pressed into it. Subsequent digital image correlation was applied to estimate the strain field in the region around the indenting tip. Regions in the wood with high tensile or shear strains were identified, i.e. where cracking and fiber separation is believed to initiate.

    Nyckelord
    Defibration, Scratching, Strain analysis
    Nationell ämneskategori
    Teknik och teknologier Trävetenskap
    Forskningsämne
    Teknisk fysik med inriktning mot tribomaterial
    Identifikatorer
    urn:nbn:se:uu:diva-310478 (URN)000387974800001 ()
    Forskningsfinansiär
    Energimyndigheten
    Tillgänglig från: 2016-12-16 Skapad: 2016-12-16 Senast uppdaterad: 2019-05-02Bibliografiskt granskad
    2. Investigating tool engagement in groundwood pulping: finite element modelling and in-situ observations at the microscale
    Öppna denna publikation i ny flik eller fönster >>Investigating tool engagement in groundwood pulping: finite element modelling and in-situ observations at the microscale
    2019 (Engelska)Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArtikel i tidskrift (Refereegranskat) Epub ahead of print
    Abstract [en]

    With industrial groundwood pulping processes relying on carefully designed grit surfaces being developed for commercial use, it is increasingly important to understand the mechanisms occurring in the contact between wood and tool. We present a methodology to experimentally and numerically analyse the effect of different tool geometries on the groundwood pulping defibration process. Using a combination of high-resolution experimental and numerical methods, including finite element (FE) models, digital volume correlation (DVC) of synchrotron radiation-based X-ray computed tomography (CT) of initial grinding and lab-scale grinding experiments, this paper aims to study such mechanisms. Three different asperity geometries were studied in FE simulations and in grinding of wood from Norway spruce. We found a good correlation between strains obtained from FE models and strains calculated using DVC from stacks of CT images of initial grinding. We also correlate the strains obtained from numerical models to the integrity of the separated fibres in lab-scale grinding experiments. In conclusion, we found that, by modifying the asperity geometries, it is, to some extent, possible to control the underlying mechanisms, enabling development of better tools in terms of efficiency, quality of the fibres and stability of the groundwood pulping process.

    Nyckelord
    CT; Defibration; DVC; FE; Grinding; Wood
    Nationell ämneskategori
    Pappers-, massa- och fiberteknik Tribologi (ytteknik omfattande friktion, nötning och smörjning)
    Identifikatorer
    urn:nbn:se:uu:diva-382716 (URN)
    Forskningsfinansiär
    Energimyndigheten, 37206-2
    Tillgänglig från: 2019-04-29 Skapad: 2019-04-29 Senast uppdaterad: 2019-11-20
    3. Defibration mechanisms and energy consumption in the grinding zone – a lab scale equipment and method to evaluate groundwood pulping tools
    Öppna denna publikation i ny flik eller fönster >>Defibration mechanisms and energy consumption in the grinding zone – a lab scale equipment and method to evaluate groundwood pulping tools
    2019 (Engelska)Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669Artikel i tidskrift (Refereegranskat) Epub ahead of print
    Abstract [en]

    Groundwood pulping is a process that employs large machines, making them difficult to use in research. Lab scale grinders exist, but even though they are smaller, the sizes of the grinding stones or segments make them cumbersome to exchange and tailor. This study presents a method and an apparatus for investigating the detailed mechanisms and the energy requirements behind the fibre separation process. A well-defined grinding tool was used at three different temperatures to demonstrate that the equipment can differentiate levels of energy consumption and defibration rates, confirming the well-known fact that a higher temperature facilitates defibration. It is also shown how the equipment can be used to study the influence of grinding parameters, exemplified by the effect of temperature on the way fibres are separated and the character of the produced fibres. A key feature of the equipment is the use and evaluation of small grinding surfaces, more readily designed, produced, evaluated and studied. This reduces both the cost and time necessary for testing and evaluating. At the same time, a technique to produce well defined grinding surfaces was employed, which is necessary for repeatability and robust testing, not achievable with traditional grinding stones.

    Nyckelord
    Computed tomography, Energy efficiency, Groundwood pulping, Lab scale equipment, Test method
    Nationell ämneskategori
    Tribologi (ytteknik omfattande friktion, nötning och smörjning) Pappers-, massa- och fiberteknik
    Identifikatorer
    urn:nbn:se:uu:diva-382698 (URN)10.1515/npprj-2019-0063 (DOI)
    Forskningsfinansiär
    Energimyndigheten, 37206-2
    Tillgänglig från: 2019-04-29 Skapad: 2019-04-29 Senast uppdaterad: 2019-11-12
    4. Influences of load and temperature on groundwood pulping with well-defined tools
    Öppna denna publikation i ny flik eller fönster >>Influences of load and temperature on groundwood pulping with well-defined tools
    2019 (Engelska)Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 438-439, artikel-id 203051Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Groundwood pulping is an industrial process with a high energy demand, although only a minor part of the energy is used for actually separating the fibres and the rest for working them. Traditionally, the separation process employs a grinding stone having particles embedded in a softer matrix. The position and distribution of the particles have been random, causing their interaction with the wood to also be random. This makes studies of the mechanisms during the separation process difficult. Knowledge of the mechanisms in the separation process helps when designing future tools aimed at energy efficiency or tailored fibre properties. Recently, grinding surfaces having diamond particles brazed to a steel backing at fixed positions have been developed and commercialised. In this work, individual particles are not positioned at the tool surfaces. Instead, well-defined structured diamond films, soldered to a backing, are used as grinding tools. The grinding asperities of such films can be tailored to shapes that are not possible to achieve by using particles. Using this kind of tool in a lab scale grinding equipment, confirms the well-known fact that increased load or increased temperature both lead to lower energy consumption for fibre separation and longer, less damaged fibres.

    Nyckelord
    Grinding, Pulping, Wood tomography, Energy savings, Tool design
    Nationell ämneskategori
    Tribologi (ytteknik omfattande friktion, nötning och smörjning) Pappers-, massa- och fiberteknik
    Identifikatorer
    urn:nbn:se:uu:diva-382700 (URN)10.1016/j.wear.2019.203051 (DOI)
    Forskningsfinansiär
    Energimyndigheten, 37206-2
    Tillgänglig från: 2019-04-29 Skapad: 2019-04-29 Senast uppdaterad: 2019-11-12
    5. Evaluation of well-defined tool surface designs for groundwood pulping
    Öppna denna publikation i ny flik eller fönster >>Evaluation of well-defined tool surface designs for groundwood pulping
    2019 (Engelska)Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, nr 4, s. 9575-9587Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Groundwood pulping is a process in which logs are pressed against a rotating grinding stone. A conventional grinding stone is generally made of grinding particles in a vitrified matrix. As the particles are practically round, their contact with the wood is limited to occasional point contacts. The interaction between the particles and the wood occurs at random positions and at random times, only intermittently contributing to the defibration process. In this work, well-defined grinding tools with asperities giving line contacts rather than point contacts were tested. The tool surface asperities were elongated in shape and positioned with different density over the surface. The tools were tested in a lab-scale equipment at elevated temperatures, and their performance was compared to that of a conventional grinding stone. The grinding mechanisms varied between the different tools, and the specific grinding energy was reduced compared to the conventional tool.

    Nyckelord
    Groundwood pulping, Diamond tools, Energy consumption, Tomography, Grinding mechanisms
    Nationell ämneskategori
    Tribologi (ytteknik omfattande friktion, nötning och smörjning) Pappers-, massa- och fiberteknik
    Identifikatorer
    urn:nbn:se:uu:diva-382701 (URN)10.15376/biores.14.4.9575-9587 (DOI)000493997400141 ()
    Forskningsfinansiär
    Energimyndigheten, 37206-2
    Tillgänglig från: 2019-04-29 Skapad: 2019-04-29 Senast uppdaterad: 2019-12-05Bibliografiskt granskad
    6. Influence of alignment between extended tool ridges and the wood structure on the defibration mechanisms in groundwood pulping experiments
    Öppna denna publikation i ny flik eller fönster >>Influence of alignment between extended tool ridges and the wood structure on the defibration mechanisms in groundwood pulping experiments
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nationell ämneskategori
    Tribologi (ytteknik omfattande friktion, nötning och smörjning) Pappers-, massa- och fiberteknik
    Identifikatorer
    urn:nbn:se:uu:diva-382709 (URN)
    Forskningsfinansiär
    Energimyndigheten, 37206-2
    Tillgänglig från: 2019-04-29 Skapad: 2019-04-29 Senast uppdaterad: 2019-09-10
  • 6.
    Heldin, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Carlsson, Jenny
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Isaksson, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    On tool engagement in groundwood pulping - in-situ observations and numerical modelling at the microscale2019Ingår i: The 11th Fundamental Mechanical Pulp Research Seminar, Norrköping, Sweden, April 2-4, 2019Konferensbidrag (Övrigt vetenskapligt)
  • 7.
    Heldin, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    A labscale test equipment ot study the tool surface influence in pressure groundwood pulping2015Ingår i: 20th International Conference on Wear of Materials, Toronto, Canada, April 12-16, 2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A test rig has been designed to allow controlled studies of the mechanisms in the industrial Pressure Ground Wood (PGW) pulping process:

    • The equipment consists of a setup similar to a lathe, with a tool sliding against a rotation wood workpiece.
    • Placed inside a pressure chamber which allows testing at steam temperatures and pressures exceesing those in industrial pulping.
    • Normal force and friction force are continuously monitored.
    • Separated fibers, collected after the test, the tool surface and the track of the machined workpiece are analysed after the test.
  • 8.
    Heldin, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Defibration mechanisms and energy consumption in the grinding zone – a lab scale equipment and method to evaluate groundwood pulping tools2019Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Groundwood pulping is a process that employs large machines, making them difficult to use in research. Lab scale grinders exist, but even though they are smaller, the sizes of the grinding stones or segments make them cumbersome to exchange and tailor. This study presents a method and an apparatus for investigating the detailed mechanisms and the energy requirements behind the fibre separation process. A well-defined grinding tool was used at three different temperatures to demonstrate that the equipment can differentiate levels of energy consumption and defibration rates, confirming the well-known fact that a higher temperature facilitates defibration. It is also shown how the equipment can be used to study the influence of grinding parameters, exemplified by the effect of temperature on the way fibres are separated and the character of the produced fibres. A key feature of the equipment is the use and evaluation of small grinding surfaces, more readily designed, produced, evaluated and studied. This reduces both the cost and time necessary for testing and evaluating. At the same time, a technique to produce well defined grinding surfaces was employed, which is necessary for repeatability and robust testing, not achievable with traditional grinding stones.

  • 9.
    Heldin, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Designed tools for controlling the defibration mechanisms in the pressure groundwood process2015Ingår i: International Tribology Conference, Tokyo 2015, Tokyo, Japan, September 16-20, 2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The pulp and paper industry is a large global industry producing millions of tons of paper each year. To produce pulp for this paper, only a handful of processes are used. One of these is the mechanical pulping process, called Pressure Ground Wood (PGW). Although commonly used, the tribological details of the mechanisms behind the stochastic fiber separation are not well known.

    In order to study these mechanisms, and the influence of geometries at the tool surface, a test equipment allowing testing in a similar, but more controlled, environment is needed. For this purpose, a lab scale rig has been designed, capable of grinding at temperatures and pressures at industrially relevant conditions. The tools used are made of CVD-diamond thin films, structured into different well defined patterns of sharp edges. Samples of Norway spruce have been ground both using these tools and a conventional grinding stone surface. The fibers produces are compared and the possibility of controlling the fiber characteristics using the designed tools is discussed.

  • 10.
    Heldin, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Evaluation of well-defined tool surface designs for groundwood pulping2019Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, nr 4, s. 9575-9587Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Groundwood pulping is a process in which logs are pressed against a rotating grinding stone. A conventional grinding stone is generally made of grinding particles in a vitrified matrix. As the particles are practically round, their contact with the wood is limited to occasional point contacts. The interaction between the particles and the wood occurs at random positions and at random times, only intermittently contributing to the defibration process. In this work, well-defined grinding tools with asperities giving line contacts rather than point contacts were tested. The tool surface asperities were elongated in shape and positioned with different density over the surface. The tools were tested in a lab-scale equipment at elevated temperatures, and their performance was compared to that of a conventional grinding stone. The grinding mechanisms varied between the different tools, and the specific grinding energy was reduced compared to the conventional tool.

  • 11.
    Heldin, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Influence of alignment between extended tool ridges and the wood structure on the defibration mechanisms in groundwood pulping experimentsManuskript (preprint) (Övrigt vetenskapligt)
  • 12.
    Heldin, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Influences of grinding surface alignment in groundwood pulping of Norway spruce2018Ingår i: 18th Nordic Symposium on Tribology - NORDTRIB 2018, Uppsala, Sweden, June 18-21, 2018Konferensbidrag (Övrigt vetenskapligt)
  • 13.
    Heldin, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Influences of load and temperature on groundwood pulping with well-defined tools2019Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 438-439, artikel-id 203051Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Groundwood pulping is an industrial process with a high energy demand, although only a minor part of the energy is used for actually separating the fibres and the rest for working them. Traditionally, the separation process employs a grinding stone having particles embedded in a softer matrix. The position and distribution of the particles have been random, causing their interaction with the wood to also be random. This makes studies of the mechanisms during the separation process difficult. Knowledge of the mechanisms in the separation process helps when designing future tools aimed at energy efficiency or tailored fibre properties. Recently, grinding surfaces having diamond particles brazed to a steel backing at fixed positions have been developed and commercialised. In this work, individual particles are not positioned at the tool surfaces. Instead, well-defined structured diamond films, soldered to a backing, are used as grinding tools. The grinding asperities of such films can be tailored to shapes that are not possible to achieve by using particles. Using this kind of tool in a lab scale grinding equipment, confirms the well-known fact that increased load or increased temperature both lead to lower energy consumption for fibre separation and longer, less damaged fibres.

  • 14.
    Heldin, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wiklund, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Tailored grinding surfaces for groundwood pulping - influencing wear mechanisms and energy requirements2017Ingår i: 21st International Conference on Wear of Materials, Long Beach, March 26-30, 2017Konferensbidrag (Övrigt vetenskapligt)
  • 15.
    Hossain, Md Shakhawath
    et al.
    Department of Chemical Engineering and FSCN, Mid Sweden University, Holmgatan 10, SE-85170, Sundsvall, Sweden.
    Bergström, Per
    Department of Chemical Engineering and FSCN, Mid Sweden University, Holmgatan 10, SE-85170, Sundsvall, Sweden.
    Uesaka, Tetsu
    Department of Chemical Engineering and FSCN, Mid Sweden University, Holmgatan 10, SE-85170, Sundsvall, Sweden.
    Uniaxial compression of three-dimensional entangled fibre networks: impacts of contact interactions2019Ingår i: Modelling and Simulation in Materials Science and Engineering, ISSN 0965-0393, E-ISSN 1361-651X, Vol. 27, nr 1, artikel-id 015006Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper concerns uniaxial compression of anisotropic fibre network, as typically seen in the end use of nonwoven and textile fibre assemblies. The constitutive relationship and deformation mechanism have been investigated by using a bead-model to represent the complex structures of the constituent fibres and the fibre networks. The compression stress shows a power-law dependency on the density with a threshold density for both experimental and numerical fibre networks. Unlike the widely studied tri-axial compression of the initially isotropic network, it was found that the contact interaction between the fibres, especially the fibre-fibre contact stiffness (or the transverse compression properties of fibres), has a large impact on all the constitutive parameters. In particular, the exponent values computed based on the softer contact stiffnesses agreed very well with the experimental values reported in the literature. The internal deformation mechanism was similar to the earlier studies that at low compression, the deformation is dominated by the low-energy-mode deformations (i.e. bending and shear), whereas at higher compression, the difference appears: the compression of fibre-fibre contacts, instead of the deformation in the fibre axial direction, takes over.

  • 16.
    Krasnoshlyk, Victoria
    et al.
    Univ Grenoble Alpes, CNRS UMR 5521, Grenoble INP, Lab Sols Solides Struct Risques 3SR, F-38000 Grenoble, France;Univ Grenoble Alpes, CNRS UMR 5518, Grenoble INP, Lab Genie Proc Papetiers LGP2, F-38000 Grenoble, France.
    du Roscoat, Sabine Rolland
    Univ Grenoble Alpes, CNRS UMR 5521, Grenoble INP, Lab Sols Solides Struct Risques 3SR, F-38000 Grenoble, France.
    Dumont, Pierre J. J.
    Univ Lyon, Inst Natl Sci Appl Lyon INSA Lyon, CNRS UMR 5259, Lab Mecan Contacts & Struct LaMCoS, F-69621 Lyon, France.
    Isaksson, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Ando, Edward
    Univ Grenoble Alpes, CNRS UMR 5521, Grenoble INP, Lab Sols Solides Struct Risques 3SR, F-38000 Grenoble, France.
    Bonnin, Anne
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Three-dimensional visualization and quantification of the fracture mechanisms in sparse fibre networks using multiscale X-ray microtomography2018Ingår i: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences, ISSN 1364-5021, E-ISSN 1471-2946, Vol. 474, nr 2215, artikel-id 20180175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The structural changes that are induced by the initiation and the propagation of a crack in a low-density paper (LDP) were studied using single edge-notched fracture tests that were imaged under an optical microscope or in laboratory or synchrotron X-ray microtomographs. The two-dimensional optical images were used to analyse the links between the mesoscale structural variations of LDP and the crack path. Medium-resolution X-ray three-dimensional images were used to analyse the variations in the thickness and local porosity of samples as well as their displacement field that were induced by the LDP fracture. High-resolution three-dimensional images showed that these mesostructural variations were accompanied by complex fibre and bond deformation mechanisms that were, for the first time, in situ imaged. These mechanisms occurred in the fracture process zone that developed ahead of the crack tip before the crack path became distinct and visible. They were at the origin of the aforementioned thickness variations that developed more particularly along the crack path. They eventually led to fibre-fibre bond detachment phenomena and crack propagation through the fibrous network. These results can be used to enhance the current structural and mechanical models for the prediction of the fracture behaviour of papers.

  • 17.
    Malmberg, Filip
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Centrum för bildanalys. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Lindblad, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Centrum för bildanalys. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Östlund, Catherine
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Centrum för bildanalys. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Almgren, Karin
    Gamstedt, E. Kristofer
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Measurement of fibre–fibre contact in three-dimensional images of fibrous materials obtained from X-ray synchrotron microtomography2011Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 637, nr 1, s. 143-148Artikel i tidskrift (Refereegranskat)
  • 18. Marais, Andrew
    et al.
    Magnusson, Mikael S.
    Joffre, Thomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Wernersson, Erik L. G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Wågberg, Lars
    New insights into the mechanisms behind the strengthening of lignocellulosic fibrous networks with polyamines2014Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, nr 6, s. 3941-3950Artikel i tidskrift (Refereegranskat)
  • 19.
    Mesquine, Abdellah
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Fibre Network Generation andAnalysis: Method for simulation of inhomogeneous static fibre networks2012Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In paper optics, advanced modeling of the interaction of light with complex structuresare required for optimization of the optical properties of paper. Monte Carlosimulation routines have been developed in an Open Source project, PaperOpt, inorder to simulate light scattering in paper. The goal of the project is to make the toolmore modular and extensible so that researchers within the paper optics field canmake their own contributions to the model. This thesis is a part of Open PaperOptproject and its goal is to generate paper structures that resemble real paper sheets.This Master’s thesis describes the design and implementation of a model forgeneration of virtual fiber networks with controlled fiber distribution within the papersheet. A C++ written program that generates a fiber network according to a fibermass distribution table has been developed. A qualitative and quantitative comparisonbetween simulated paper structures and real paper obtained from beta-scanmeasurements is also described.

  • 20.
    Miettinen, Arttu
    et al.
    Department of Physics, University of Jyväskylä, Finland.
    Luengo Hendriks, Cris L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Chinga-Carrasco, Gary
    Paper and Fibre Research Institute, Trondheim, Norway.
    Gamstedt, E. Kristofer
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Kataja, Markku
    Department of Physics, University of Jyväskylä, Finland.
    A non-destructive X-ray microtomography approach for measuring fibre length in short-fibre composites2012Ingår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 72, nr 15, s. 1901-1908Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An improved method based on X-ray microtomography is developed for estimating fibre length distribution of short-fibre composite materials. In particular, a new method is proposed for correcting the biasing effects caused by the finite sample size as defined by the limited field of view of the tomographic devices. The method is first tested for computer generated fibre data and then applied in analyzing the fibre length distribution in three different types of wood fibre reinforced composite materials. The results were compared with those obtained by an independent method based on manual registration of fibres in images from a light microscope. The method can be applied in quality control and in verifying the effects of processing parameters on the fibre length and on the relevant mechanical properties of short fibre composite materials, e.g. stiffness, strength and fracture toughness. (C) 2012 Elsevier Ltd. All rights reserved.

  • 21.
    Wernersson, Erik L. G.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Borodulina, Svetlana
    Kulachenko, Artem
    Borgefors, Gunilla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Characterisations of fibre networks in paper using micro computed tomography images2014Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, nr 3, s. 468-475Artikel i tidskrift (Refereegranskat)
1 - 21 av 21
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