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  • 301.
    Karlsson, Maria
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Underlag för utformning av statistikrapporter i ett scannersystem2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study aims to provide support and suggestions for the design of statistical reports to WoodEye's new statistical database based on interviews with a sample of customers of Innovativ Vision AB. The new databas will be developed because of the improved fifth generation WoodEye 5, that will be in operation in late 2011. The customers varies widely in scope, and therefore the new statistical database should be characterized by a greater freedom of choice. Automatic sorting of wood panels imply a higher capacity and a smoother inspection. A greater variety of products can be produced, and a larger amount of sorting rules can be applied to automatic inspection of wood than in the case of manual inspection. The interviews reveal that there are wide variations in follow-up activities between the companies. The follow-ups the reference companies perform today are primarily whether the actual production is related to the deferred production, personnel monitoring, availability monitoring and supplier monitoring. Many of the companies demand some kind of defects statistics, for optimal follow-up of the raw material.

  • 302.
    Kielmann, B
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Georg-August-University Göttingen, Germany.
    Militz, H
    Georg-August-University Göttingen, Germany ; Technological Educational Institute of Larissa, Greece.
    Koch, G
    Federal Research Institute of Rural Areas, Forestry and Fisheries (vTI), Germany.
    Mai, C
    Georg-August-University Göttingen, Germany.
    Modification of three hardwoods with an N-methylol melamine compound and a metal-complex dye2014In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 48, no 1, p. 123-136Article in journal (Refereed)
    Abstract [en]

    This study evaluated the combined modification and staining of ash, beech and maple wood with a low molecular weight N-methylol melamine compound (NMM) and a metal-complex dye. Wood samples were treated with aqueous solutions of 10, 20 and 30 wt% NMM and 5 wt% of the dye. The treatment caused the fixation of the water-soluble dye by the NMM resin. Vacuum pressure impregnation of unsealed wood blocks did not result in different solution uptake and weight percent gain after curing among the three species, but sealing of the surfaces of the wood blocks to allow penetration only into one direction revealed easiest penetrability of beech followed by maple and ash. UV micro-spectrophotometry and light microscopy indicated that NMM was partly deposited in the cell wall and partly in the lumens. Penetration of the metal-complex dye was shown by means of X-ray micro-analysis (SEM–EDX). The study shows that a combined resin modification and staining of the three wood species tested is possible and that NMM causes fixation of the water-soluble dye.

  • 303.
    Kielmann, B
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Georg-August-University Göttingen, Germany ; Technological Educational Institute of Thessaly, Greece.
    Militz, H
    Georg-August-University Göttingen, Germany.
    Mai, C
    Georg-August-University Göttingen, Germany.
    Decay resistance of ash, beech and maple wood modified with N-methylol melamine and a metal complex dye2014In: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 89, p. 110-114Article in journal (Refereed)
    Abstract [en]

    This study evaluated the decay resistance of ash (Fraxinus excelsior L.), beech (Fagus sylvatica L.), and maple (Acer platanoides L.) wood impregnated by a full cell process with N-methylol melamine (NMM) and combined NMM-metal complex dye (NMM-BS) in aqueous solutions. Basidiomycete decay testing involved incubation with Coniophora puteana (brown rot) and Trametes versicolor (white rot) according to a modified EN 113 (1996) standard, while for the soft rot fungal resistance was evaluated following the standard ENv 807 (2001). NMM and NMM-BS modifications at a WPG range of 7–11% provided decay protection against brown rot resulting in a mass loss less than the required limit (3%). The NMM and NMM-BS modified wood showed increased resistance to white rot decay; however, a higher WPG is needed to prohibit attack from this hardwood specific fungus. The metal-complex dye alone revealed biocidal effects against basidiomycetes. An increased WPG in NMM or NMM-BS had a positive impact against soft rot decay and the lowest mass losses after 32 weeks of exposure were obtained with NMM modification at about 18–21% WPG. NMM modification at this WPG range, however, was not sufficient to protect the wood from soft rot decay. The wood of beech and maple showed slightly higher resistance to all decay types than ash, probably due to the poorer degree of modification of the latter.

  • 304.
    Kielmann, B
    et al.
    Georg-August-University Göttingen, Germany.
    Militz, H
    Georg-August-University Göttingen, Germany.
    Mai, C
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Technological Educational Institute of Thessaly, Greece.
    Strength changes in ash, beech and maple wood modified with a N-methylol melamine compound and a metal-complex dye2013In: Wood research, ISSN 1336-4561, Vol. 58, no 3, p. 343-350Article in journal (Refereed)
    Abstract [en]

    Ash, beech and maple wood was modified with aqueous solutions of methylated N-methylol melamine (NMM) and a metal-complex dye (BS) consisting of 10, 20, and 30 % NMM and 5 % BS. Static bending strength and stiffness, impact bending strength and hardness were examined to evaluate the suitability of modified wood for structural uses. The combined NMMBS modification resulted in significant higher dynamic (MOEdyn) and static (MOE) moduli of elasticity for all species. Beech and maple exhibited enhanced static bending strength (MOR), while that of ash was unchanged. The higher stiffness and strength of NMM-BS modified wood is attributed to its higher wood density and lower EMC and to the stiff character of NMM resin incorporated in the wood matrix. Impact bending strength decreased substantially after modification as a result of reduced pliability of treated wood. Brinell hardness significantly increased with the weight percent gain (WPG) due to modification, and, unlike the other properties, it was positively correlated with the WPG.

  • 305. Kielmann, BC
    et al.
    Militz, Holger
    Adamopoulos, Stergios
    Technological Educational Institute of Larissa, Greece.
    Combined N-Methylol melamine-colouring agent modification of hardwoods to improve their performance under use class 32012In: The Sixth European Conference on Wood Modification: Proceedings / [ed] Dennis Jones, Holger Militz, Marko Petrič, Franc Pohleven, Miha Humar, Matjaž Pavlič, University of Ljubljana , 2012, p. 437-446Conference paper (Refereed)
  • 306.
    Kifetew, Girma
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Nilsson, Jonaz
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Is it possible to constrain moisture movement of densified wood product mechanically?2011In: Mechano-chemical transformation of wood during THM processing / [ed] Navi, P. & Roth, A, Biel Switzerland: Bern University of Applied Sciencs, Architecture, Wood and Civil Engineering , 2011, p. 67-68Conference paper (Refereed)
    Abstract [en]

    Densification of wood in the transverse direction increases the density. One of the reasons for densifying wood is to produce high quality timber from timbers of low quality. However, densified wood shows an undesired behaviour, i.e. a tendency to return to its initial dimensions when it is subjected to heat and humidity, i.e. shape memory. There are several methods to overcome the problem of shape memory.

    This study uses a three-layered cross-laminated wood panel where one of the layers is of densified wood and the other two are of normal wood together these will mechanically restrain the shape memory of the densified layer.

    The study includes three stages:

    • Densification of clear wood in the radial direction
    • Manufacture of a three-layered cross laminated composite product with densified wood as a service layer
    • Testing of the shape stability when the composite was subjected to variations relative humidity (40-85 % RH at 20°)

    The result of this study reveals the significance of service to bottom layer thickness ratio on the shape stability of the cross laminated composite. Consequently, the performance and the shape stability of the cross laminated composite were significant when the service to bottom layer thickness ratio increases. Therefore, it appears feasible to disclose the appreciable degree of shape stability, hardness and wear resistance of the product. Accordingly, cross laminated composite can be considered as one of the promising mechanical methods for improving moisture movement of densified wood product.

  • 307.
    Kifetew, Girma
    et al.
    KTH, Träteknologi.
    Sandberg, Dick
    KTH, Träteknologi.
    A Comparsion of Dot-counting and Mercury immersion Methods for Determing Density.1996Report (Other academic)
    Abstract [en]

    This paper describes two wood density determination techniques, one using the dotcounting and the other Mercury immersion and discuses the correlation between the methods. The paper includes also a short literature survey on some other wood density determination methods.

  • 308.
    Kliger, Robert
    et al.
    Chalmers University of Technology, Sweden.
    Johansson, Marie
    Chalmers University of Technology, Sweden.
    Ormarsson, Sigurdur
    Chalmers University of Technology, Sweden.
    Bäckström, Magnus
    Chalmers University of Technology, Sweden.
    The Builders'€™ View on Drying Quality and its Consequences2004In: Proceedings of COST E15 - Drying timber for value-added products, Athens, Greece, 22-24 April. 01/01/2004, 2004Conference paper (Refereed)
  • 309.
    Konnerth, Johannes
    et al.
    BOKU-University of Natural Resources and Applied Life Sciences, Austria.
    Eiser, Martina
    Competence Center for Wood Composites and Wood Chemistry, Austria.
    Jäger, Andreas
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Follrich, Jürgen
    Competence Center for Wood Composites and Wood Chemistry, Austria.
    Ters, Thomas
    BOKU-University of Natural Resources and Applied Life Sciences, Austria.
    Hansmann, Christian
    Competence Center for Wood Composites and Wood Chemistry, Austria.
    Wimmer, Rupert
    ood Technology and Wood-based Composites Unit, Germany.
    Macro- and micro-mechanical properties of red oak wood (Quercus rubra L.) treated with hemicellulases2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 4, p. 447-453Article in journal (Refereed)
    Abstract [en]

    Red oak wood (Quercus rubra L.) samples were submitted to an enzymatic treatment with a commercial mixture of hemicellulases aiming at the selective depolymerization and removal of the hemicelluloses. Mechanical properties of treated samples were characterized and compared with untreated samples at two hierarchical levels. At the macrolevel, tensile properties revealed to be less sensitive to degradation of the cell wall matrix compared to compression and hardness properties. Results obtained through indentation at the microlevel indicated that hardness and the so-called reduced modulus of treated wood were significantly lowered. Accordingly, hardness and reduced elastic modulus have proven to be most sensitive to modification of the cell wall matrix by reducing the content of hemicelluloses. It is proposed that transversal and shear stresses, which are mainly carried by the cell wall matrix, are additional parameters having strong effects on elastic modulus obtained by nanoindentation. Micromechanical modeling was employed to confirm the observed changes. There is consistency between the measured and the modeled properties, obtained at both the microlevel and the macrolevel of wood.

  • 310. Kortsalioudakis, Nathanail
    et al.
    Petrakis, Panagiotis
    Moustaizis, Stavros
    Voulgaridis, Elias
    Adamopoulos, Stergios
    Karastergiou, Sotirios
    Passialis, Costas
    An application of a laser drilling technique to fir and spruce wood specimens to improve their permeability2015In: Innovation in Woodworking Industry and Engineerings Design, ISSN 2367-6663, no 1, p. 5-13Article in journal (Refereed)
    Abstract [en]

    In this work, the application of a laser drilling technique on fir (Abies borisii regis) and spruce (Picea excelsa) wood and a new approach of improvement the wood permeability is investigated. This technique is focusing on increasing the permeability of wood after surface drilling by a high power laser source. The research was involving the establishment of an effective drilling pattern protocol, which will not substantially affect the mechanical strength of wood and to improve its permeability. All lateral surfaces of the wood specimens, 2 × 2 cm in cross section and 34 cm long, were drilled by laser to a depth of 4 mm (1/5 of specimen thickness) with two drilling patterns (distance between holes 10 × 10 mm and 10 × 20 mm). Preliminary results showed that laser drilling is a promising method for improvement of wood permeability without significant effect on its mechanical strength, and this is very important for an effective treatment of the refractory to impregnation fir and spruce wood.

  • 311. Kumar, A
    et al.
    Adamopoulos, S
    Jones, D
    Amiandamhen, Stephen
    Forest biomass availability and utilization potential in Sweden: A review2020In: Waste and Biomass Valorization, ISSN 1877-2641, E-ISSN 1877-265XArticle in journal (Refereed)
    Abstract [en]

    In recent years, there has been a growing interest in many parts of the world for more effective biomass utilization due tolegislative and public interest in sustainable development. Whilst much of the effort has been on energy generation frombiomass, there is considerable interest on biomass availability and utilization for other end uses. With about 1% of the world’scommercial forest areas, Sweden provides about 10% of the sawnwood, and pulp and paper that is traded on the global market.The Swedish agricultural sector also contributes to biomass availability, not only by production of sustainable food crops, butalso by utilizing side streams and underutilized land for biomaterial purposes. To meet the challenges that climate changepresents, there has to be a shift to sustainable biomass production and increased interest in promoting a circular bioeconomy.This review presents a systematic assessment on the availability of biomass and its utilization potential in Sweden. Thereview also focuses on biomass production and trade in the Swedish forest industry. In addition, the environmental impactof biomass utilization is discussed

  • 312.
    Kumar, Anuj
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Czech Technical University in Prague, Czech Republic.
    Richter, Jan
    Czech Technical University in Prague, Czech Republic.
    Tywoniak, Jan
    Czech Technical University in Prague, Czech Republic.
    Hajek, Petr
    Czech Technical University in Prague, Czech Republic.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Šegedin, Urban
    University of Ljublijana, Slovenia.
    Marko, Petrič
    University of Ljublijana, Slovenia.
    Surface modification of Norway spruce wood by octadecyltrichlorosilane (OTS) nanosol by dipping and water vapour diffusion properties of the OTS-modified wood2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 1, p. 45-56Article in journal (Refereed)
    Abstract [en]

    The present research deals with a simple dipping method to insert octadecyltrichlorosilane (OTS) into cell walls of spruce wood and to deposit OTS layers on its inner and outer surfaces. Distribution and chemical interactions of OTS with wood polymers has been investigated by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The OTS/n-hexane solution penetrated into wood via capillary forces through ray tracheids and bordered pits and was deposited as OTS organic-inorganic layers on wood cell walls. The hypothesis is supported by the results, according to which the OTS molecules are hydrolysed by the wood moisture and by free OH groups of the cell wall components. The hydrolysed OTS molecules react with the OH groups and elevate the hydrophobicity of wood.

  • 313.
    Kumar, Anuj
    et al.
    Natural Resources Institute Finland (Luke), Finland;Czech Technical University in Prague, Czech Republic.
    Ryparovà, Pavla
    Czech Technical University in Prague, Czech Republic.
    Kasal, Bohumil
    Wilhelm-Klauditz-Institut WKI, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Hajek, Petr
    Czech Technical University in Prague, Czech Republic.
    Resistance of bamboo scrimber against white-rot and brown-rot fungi2020In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 15, no 1, p. 57-63Article in journal (Refereed)
    Abstract [en]

    Bamboo scrimber is one of the most emerging structural materials for future building applications andit possesses properties comparable to other natural wood-based engineered materials such as glulam,laminated veneer lumber and cross-laminated timber. The goal of this work was to study the decayresistance of bamboo scrimber against white-rot (Trametes versicolor) and brown-rot fungi (Serpulalacrymans). Bamboo scrimber samples were incubated in petri dishes with the wood-decaying fungiand the weight loss after 12 weeks was measured. The surface morphology of fungal-degradedbamboo scrimber was evaluated using optical microscopy. Based on the percentage weight loss,bamboo scrimber could be classified as highly resistant against bio-deterioration by white andbrown-rot fungi.

  • 314.
    Landscheidt, Steffen
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Kans, Mirka
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Automation Practices in Wood Product Industries: Lessons learned, current Practices and Future Perspectives2016In: The 7th Swedish Production Symposium SPS, 25-27 October, 2016, Lund, Sweden, Lund, Sweden: Lund University , 2016, , p. 9article id E1Conference paper (Refereed)
    Abstract [en]

    Wood product industries are a cornerstone of the Swedish industry and contribute vastly to the total Swedish export value. Wood as material itself has a promising perspective of becoming one of the most valuable resources. Sweden in particular has a long tradition and the knowledge of how to cultivate forests. In comparison to the highly automated forest industries, production systems of Swedish wood products industries are mostly characterized by a low degree of automation, tough manual labour and a relative low competency of the workforce. Facing fiercer competition on a global market, Swedish wood product industries are starting to lose touch with wood working industries in other industrialized European countries. Based upon established literature, this paper systematizes the status of automation practices in wood processing industries. The outcome of this study also outlines the expected effects and the future perspectives of digitalization and robotic automation for wood processing industries in high-1are not ready to implement the necessary standards to enter Industry 4.0. Not only are the technical prerequisites not fulfilled, but also a lack of appropriate production organization, logistics and economic basis is affecting negatively.

  • 315.
    Landscheidt, Steffen
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Kans, Mirka
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Winroth, Mats
    Chalmers University of Technology.
    Differences on automation practices in wooden single-family houses manufacturing: Four case studies2017In: 23rd International Wood Machining Seminar Proceedings / [ed] Marcin Zbiec and Kazimierz Orlowski, Warsaw, Poland: Warsaw University of Life Sciences , 2017, p. 350-359Conference paper (Refereed)
    Abstract [en]

    In densely forested countries, forest and wood-based products are an important contributing factor to the country’s economy and also a valuable resource for house manufacturing. With rising demand for housing in Europe, wooden houses have become more of an alternative to concrete houses. Although wooden houses have always been popular in Nordic countries, higher demand puts more pressure on seemingly outdated production facilities and personnel in order to supply the market. Whereas many other industries strive to modern production concepts such as Industry 4.0 to adapt to new market conditions, industrial timber house building is still characterized by a high amount of manual labor.

    In Europe´s highly industrialized countries, labor costs influence wooden house manufacturers rather negatively and exert great pressure on them to stay competitive. Some companies have chosen outsourcing of their operations and production as means to survive. Another way, already successfully proven in other industries, is the automation and digitalization of production processes. Effective implementation of automation equipment depends on several factors, e.g. production volume, applied material, chosen application or cycle times. It is not entirely clear which factors are contributing to the successful change to a more automated production.

    Based on an Industry 4.0 readiness model, the purpose of this study is to seek out which dimensions correlate with each other in order to support improved production processes and efficiency for wooden single-house manufactures. 

    By applying a comparative case study approach, automation standards and practices in Sweden, Germany and Austria, are described and compared. Results of this case study reveal that a production strategy together with sound digital support and information sharing leads to the best production systems for single-wooden houses manufacturers.

  • 316. Larsen, Finn
    et al.
    Ormarsson, Sigurdur
    A numerical and experimental study of stress and crack development in kiln-dried wood2012In: Proceedings of World Conference on Timber Engineering 2012, 2012Conference paper (Refereed)
    Abstract [en]

    Numerical and experimental investigations were carried out on well defined log-disc samples of Norway spruce consisting of both heartwood and sapwood, with the aim of gaining more adequate knowledge of stress and fracture generation during the drying process. Use of thin discs enabled a well-controlled and simplified drying history of the samples to be obtained. Experiments supported by the numerical model showed the heartwood to dry below the fibre saturation point, much earlier than the sapwood, and thus to start shrinking at a much earlier stage.

  • 317.
    Larsen, Finn
    et al.
    Technical University of Denmark, Denmark.
    Ormarsson, Sigurdur
    Technical University of Denmark, Denmark.
    Experimental and finite element study of the effect of temperature and moisture on the tangential tensile strength and fracture behavior in timber logs2014In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, no 1, p. 133-140Article in journal (Refereed)
    Abstract [en]

    Timber is normally dried by kiln drying, in the course of which moisture-induced stresses and fractures can occur. Cracks occur primarily in the radial direction due to tangential tensile strength (TSt) that exceeds the strength of the material. The present article reports on experiments and numerical simulations by finite element modeling (FEM) concerning the TSt and fracture behavior of Norway spruce under various climatic conditions. Thin log disc specimens were studied to simplify the description of the moisture flow in the samples. The specimens designed for TS were acclimatized to a moisture content (MC) of 18% before TSt tests at 20°C, 60°C, and 90°C were carried out. The maximum stress results of the disc simulations by FEM were compared with the experimental strength results at the same temperature levels. There is a rather good agreement between the results of modeling and experiments. The results also illustrate the strong decrease of TSt with increasing temperature at a constant MC level.

  • 318.
    Larsen, Finn
    et al.
    Technical University of Denmark, Denmark.
    Ormarsson, Sigurdur
    Technical University of Denmark, Denmark.
    Numerical and experimental study of moisture-induced stress and strain field developments in timber logs2013In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 47, no 4, p. 837-852Article in journal (Refereed)
    Abstract [en]

    When solid wood dries from a green condition to a moisture content used for further processing, moisture-induced fracture and stresses can occur. The drying stresses arise because of internal deformation constraints that are strongly affected by the cross-sectional moisture gradient differential shrinkage and the inhomogeneity of the material. To obtain a better understanding of how stresses develop during climatic variations, the field histories of stresses (and strains) in cross sections in their entirety need to be studied. The present paper reports on experiments and numerical simulations concerned with analysing the development of strains and stresses during the drying of 15-mm-thick discs of Norway spruce timber log. The samples were dried at 23 °C and relative humidity of 64 % from a green condition to equilibrium moisture content. The moisture gradient in the longitudinal direction was minimised by use of thin discs simplifying the moisture history of the samples studied. The strain field history was measured throughout the drying process by use of a digital image correlation system. Numerical simulations of the samples agreed rather well with the experimental strain results obtained. The stress results also indicated where in the cross section and when fractures could be expected to occur during drying. More optimal drying schemes showed markedly reduced stress generation.

  • 319.
    Larsen, Finn
    et al.
    Technical University of Denmark, Denmark.
    Ormarsson, Sigurdur
    Technical University of Denmark, Denmark.
    Olesen, John Forbes
    Technical University of Denmark, Denmark.
    Experimental Investigation of Moisture Driven Fracture in Solid Wood2010In: WCTE - World Conference on Timber Engineering 2010: Conference Proceeding, Riva del Garda: Trees and Timber Institute , 2010, p. 449-450Conference paper (Refereed)
    Abstract [en]

    Solid timber products, containing both heartwood and sapwood, often have a high tendency to crack during the drying process. This can cause severe loss of material for the saw-mills, especially for products with large cross sectional dimensions. The cracks (e.g. end-cracks) arise, in some cases, early in the drying process and close again later in the process. It can be difficult to see the closed cracks with visual grading. This may result in too high grading of the damaged material which may cause problems for customers such as building and furniture industries. Moisture content (MC) in green wood varies within the cross section of a timber log. The MC of heartwood, for example, is considerable lower than the MC of sapwood. Shrinkage starts at different times within different parts of the cross section, which results in a complex state of strains and stresses. The moisture related crack pattern in wood often becomes quite complex because of the annual ring structure and the different MC levels within heartwood and sapwood. The focus of this work represents the cross sectional behaviour of a timber log. The main aim is to accumulate experimental results and data for the development of a finite element model to evaluate the various couplings in the hygro-mechanical problem that govern moisture driven cracking in wood.

  • 320.
    Larsen, Finn
    et al.
    Technical University of Denmark, Denmark.
    Ormarsson, Sigurdur
    Technical University of Denmark, Denmark.
    Olesen, John Forbes
    Technical University of Denmark, Denmark.
    Experimental study of moisture-driven distortion and fracture in solid wood2010In: 11th International IUFRO Wood Drying Conference : Recent Advances in the Field of Wood Drying, Luleå: Luleå tekniska universitet, 2010, p. 137-144Conference paper (Refereed)
    Abstract [en]

    Moisture-induced fracture and lack of shape stability in solid wood products are well known problems to the saw-milling and building industries. Cracks that initiate during the drying process may cause severe material losses and the building industry may be forced to use alternative building materials. The cracking caused by kiln-drying of solid timber (and round wood) is extremely difficult to predict due to the strong orthotropic and non-homogeneous characteristics of the material in combination with considerable amounts of microscopic defects which may act as crack initiators. An experimental study has been performed to reveal the cracking behaviour of Norway spruce during drying from green moisture content down to equilibrium moisture content (EMC) at a temperature of 22-24°C and a RH of 64%. The moisture related strains and crack widths were measured with a digital image correlation system (ARAMIS) on thin discs cut from a timber log. The history of the strain field over the entire cross section of the discs was measured throughout the drying period. The results showed that the thicker discs (30 mm) cracked very early during the drying process. They also cracked significantly more than the thinner ones (15 mm) and the crack patterns developed differently. For the thicker discs the early cracks which may partly be caused by the moisture gradient in the longitudinal direction of the log, closed and became invisible later during the drying process. This indicates that sealing of timber log ends in the green moisture state could significantly reduce the development of end-cracks. It was also recognized that the initial moisture content and the shrinkage properties vary significantly from pith to bark. Based on this experimental finding it can be concluded that modelling of crack propagation in solid wood must take the material inhomogeneities into account.

  • 321.
    Larsen, Finn
    et al.
    University of Denmark.
    Ormarsson, Sigurdur
    University of Denmark.
    Olesen, John Forbes
    University of Denmark.
    Moisture-driven fracture in solid wood2011In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, no 1-2, p. 49-57Article in journal (Refereed)
    Abstract [en]

    Moisture-induced fractures in solid timber create considerable problems for both building industries and sawmills. Cracks caused by kiln-drying of solid timber are extremely difficult to predict. This paper reports on experiments concerned with methods of reducing cracks in wood and with the cracking behaviour of Norway spruce discs. The spruce was dried from green moisture content down to equilibrium moisture content at 23°C and 64% relative humidity. Moisture-related strains and crack development were measured using a digital image correlation system, Aramis. The moisture gradient in the longitudinal direction had a major influence on crack behaviour and was quite pronounced in discs more than 30 mm thick, but much more limited in discs only 15 mm thick. Although the thicker discs often cracked very early in the drying process, many of these cracks became invisible later on in the drying process, suggesting that sealing the ends of timber logs while in the green moisture state could considerably reduce the development of end-cracks. The initial moisture content and the shrinkage properties of the wood varied markedly from pith to bark. The importance of taking material inhomogeneities into account when modelling crack propagation in solid wood is emphasized. © 2011 Taylor & Francis.

  • 322.
    Lederer, Wolfgang
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Ductility of the Embedment Behavior of Steel Dowels in Wood - Permanent Deformations and the Influence of Reinforcements2015In: 20th Inter-InstituteSeminar for Young Researchers ; Jubilee Sessionfor Professor Zenon Waszczyszyn: ProgrammeandBook of Abstracts ; October 9-10, 2015, Cracow, Poland / [ed] A. Matuszak J. Pamin, Cracow, Poland, 2015, p. 27-Conference paper (Other academic)
  • 323. Lederer, Wolfgang
    et al.
    Bader, Thomas K.
    Eberhardsteiner, Josef
    Experimental Investigations and Numerical Modelling of Dowel Connections in Timber Constructions2015Conference paper (Other academic)
  • 324.
    Lederer, Wolfgang
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Numerical and Experimental Investigations of the Elasto-Plastic Behaviour of Wood-Steel Dowel Connections2013In: 19th Inter-Institute Seminar for Young Researchers, Vienna, Austria, 2013, p. 29-Conference paper (Other academic)
  • 325. Lederer, Wolfgang
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Numerical Modelling of Dowel Connections in Timber Constructions2013Conference paper (Other academic)
  • 326.
    Lederer, Wolfgang
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Muszyński, Lech
    Oregon State University, USA.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Exploring a Multi-modal Experimental Approach to Investigation of Local Embedment Behaviour of Wood under Steel Dowels2016In: Strain, ISSN 0039-2103, E-ISSN 1475-1305, Vol. 52, no 6, p. 531-547Article in journal (Refereed)
    Abstract [en]

    A multi-modal experimental approach for analysing the embedment behaviour of timber connections with steel dowels is proposed in this study. In this approach, a standard mechanical embedment test on single-dowel connections is combined with an optical measurement of surface deformations of the connection based on digital image correlation principle and an X-ray micro-computed tomography examination of the deformations in the dowel-wood interface. The latter is conducted on cylindrical cores including the dowel hole, physically extracted from the loaded specimen at three characteristic points of the load-deformation curves. The major challenge of this procedure is disrupted load transfer between the cylindrical core specimens and the external material they were plugged in for further analysis. Despite its challenges and limitations, the method revealed a potential for an unprecedented insight into the micromechanics of dowel connections and for effective correlation of the micro-level observations with the external macroscopic load-deformation characteristics.

  • 327.
    Lederer, Wolfgang
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Unger, Gerhard
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Influence of different types of reinforcements on the embedment behavior of steel dowels in wood2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, no 6, p. 793-807Article in journal (Refereed)
    Abstract [en]

    In this study, dowel displacement-embedment stress relationships for different types, numbers and positions of reinforcements were experimentally investigated using a half-hole embedment test setup. Tests were performed parallel to the grain and in compression. Screws with a full or partial thread at different positions below the dowel and oriented strand board, plywood and nail plates on the loaded surfaces of the specimens, served as reinforcements. Test results underline their potential for an increased ductility of dowel-type connections. Comparison of reinforced and unreinforced specimens suggests premature failure of the unreinforced wood and consequently, an underestimation of the embedment strength as it is subsequently used in the design of dowel connections using the European yield model. This was supported by the investigation of cracks on the surface of the specimens visualized by means of a full-field deformation measurement system. It could be demonstrated that the strength in the embedment test even further increases if the reinforcement elements actively contribute to the load transfer. This property however cannot be considered as embedment strength, but represents the strength of a connection system. Test data is compared to the design equation in Eurocode 5.

  • 328.
    Lindblad, Fredrik
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Flinkman, Matti
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Schauerte, Tobias
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Assessing corporate economic distress: a study of the wood construction industry2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 594-601Article in journal (Refereed)
    Abstract [en]

    Wood buildings are considered as a viable option to support the effort minimizing the current housing shortage in Sweden. Companies trying to develop into this industry are needed to increase the use of prefabricated wooden elements, volumes or modules in an industrialized way. Suitable companies to make this development could be found amongst firms producing wooden single-family houses. These companies currently act on a highly competitive market with many companies offering relatively homogeneous products or services. Therefore, differentiation towards the wooden multi-family house industry could be considered as a long-term strategy, minimizing the economic distress and improving the survival of the company.The study is aiming at describing the development of economic distress and market concentration ratio in the Swedish industry for wooden single-family houses, for an eleven-year period from 2005 to 2015. The companies could be helped to understand, if and how the market concentration ratio and the economic distress are connected, linking company size to economic stability and efficient resource utilization. This will be conducted by applying Altman’s Z’-score model, grouping firms into a risk, a grey or a safe zone, combined with calculating the industry structure by means of the concentration ratio model. The required data were collected from the annual reports of the 51 relevant firms in the industry.

  • 329.
    Lindblad, Fredrik
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Schauerte, Tobias
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Identifying drivers facilitating product development within the industry for wooden multi-family houses2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 602-609Article in journal (Refereed)
    Abstract [en]

    Sweden is forecasted to grow its population with 1.1 million people over the next eight-year period, increasing the demand on the construction phase of housing units throughout Sweden. However, at present, 240 of Sweden's 290 municipalities show an existing deficit of available housing units in their regions, resulting in inherent difficulties fulfilling this demand utilizing the current production structure. Therefore, further utilizing wood as a building material could contribute to minimize the gap, as well as fulfilling the EU’s goals towards the Europe 2020 strategy and the EU forest strategies, focusing on development towards innovation, bio-economy, sustainable sourcing and use of raw materials. This study is aiming to identify drivers supporting the Swedish industry of wooden multi-family houses to enable market growth through competitive and sustainable strategies. The representatives within the building process identify drivers, how they perceive their effect on the companies’ abilities to develop based on long-term and short-term strategic impact. Thus, the goal is to find ways in which wooden multi-family houses could compete as a building solution, compared to established solutions, thereby increasing the market share in Sweden. The methods used in this study is surveys distributed to representatives from municipalities, developers, contractors, architects and real estate companies.The result identifies three change drivers influencing the industry development for wooden multi-family houses in Sweden: technological-, knowledge- and environmental- drivers. These drivers have an effect on the companies’ ability for successful new product development and for development of sustainable strategies towards market growth for wooden multi-family houses.

  • 330.
    Lindemann, Jonas
    et al.
    Lund Institute of Technology, Sweden.
    Ormarsson, Sigurdur
    Dahlblom, Ola
    Sandberg, Göran
    Enabling Access to Distributed Resources in a Software for Simulating Drying Induced Deformation of Wood2003In: 16th Nordic Seminar on Computational Mechanic, 2003Conference paper (Refereed)
  • 331.
    Lukacevic, Markus
    et al.
    Vienna University of Technology, Austria.
    Kandler, Georg
    Vienna University of Technology, Austria;Dynardo Austria GmbH, Austria.
    Hu, Min
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Füssl, Josef
    Vienna University of Technology, Austria.
    A 3D model for knots and related fiber deviations in sawn timber for prediction of mechanical properties of boards2019In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 166, p. 1-18, article id 107617Article in journal (Refereed)
    Abstract [en]

    Increased use of wood has led to complex timber constructions and new types of engineered wood products. In simulations, however, mainly simplified models are used to describe this material with its strongly varying properties. Therefore, reliable prediction tools for mechanical properties of wooden boards are needed. Those varying properties mainly originate from knots and fiber deviations. Thus, we use fiber directions on board surfaces to reconstruct knots within boards. Combined with a fiber deviation model we assess our model with experiments on different levels: fiber directions on surfaces, strain fields and bending stiffness profiles.

    This model now better describes fiber patterns near knots and knot clusters. Also, we showed that accurate modeling of the pith is important to avoid large regions of incorrect fiber deviations. Furthermore, modified knot stiffness properties were successfully used to consider pre-cracked knots. Finally, we obtained multiple bending stiffness profiles, where we showed that even local effects can be simulated accurately.

    We anticipate our tool to be a starting point for improving strength grading models, where effects of knot configurations can be studied more easily than with experiments alone. Furthermore, the presented improvements will render the simulation of realistic failure mechanisms in wooden boards more likely.

  • 332.
    Lundstedt, Karin
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Thermal stresses in load-bearing glass-timber components2012Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Thermal stresses can arise in glass used in architectonic realisations in buildings as a result of solar irradiation:  that is, sunlight.  The magnitude of these thermal stresses depends on the temperature conditions in the glass in terms of the temperature differences between warm and cold areas. 

    The work described here has verified the existence and distribution of thermal stresses in glass, both theoretically and experimentally, in a load-bearing element made of glass and wood, when exposed to incident solar radiation and various degrees of shading. 

    The finite element method was used in order to simulate the temperature distribution in the glass, together with the resulting associated thermal stresses.  Parts of these model results were then compared with results and data from experimental investigations in a solar simulator.  The experimental trials were carried out on a plain glass sheet and on a wood-framed glass sheet.  This frame assembly saw the glass fitted in a wooden frame such that its edge was flush with the edges of the frame and therefore freely exposed to the surroundings.  Two different grades of glass were analysed in the theoretical modelling and used in the experimental solar exposure:  a clear glass, with a low absorption coefficient, and a tinted glass having a relatively high absorption coefficient.  The experimental part of the work included two different finishes to the glass edge:  as-cut, with no further attention, and cut and smoothed. 

    The results from the finite element method calculations agree relatively well with the experimental results.  When simulating the temperature values and distributions, the value of the coefficient of heat transfer is an important factor in determining the results.  The coefficient can be given either a constant value, taken from a standard, or a calculated value that varies depending on the surface temperature and ambient temperature at every instant.  For the clear glass with a low coefficient of absorption, the calculated temperatures did not differ significantly depending on which method had been used to provide a value for the coefficient of heat transfer.  However, for the glass with a high coefficient of absorption, and when exposed to high solar intensity, a calculated value of coefficient of heat transfer should be used in order to arrive at relevant values of surface temperatures and stresses.  Thermal tensile stresses have more effect on the total stress level than have stresses arising from typical in-service vertical loads.

  • 333.
    Lykidis, C
    et al.
    Institute of Mediterranean Forest Ecosystems and Forest Products Technology, National Agricultural Research Foundation, Greece.
    Mantanis, G
    Technological Educational Institution (TEI) of Thessaly, Greece.
    Adamopoulos, Stergios
    Technological Educational Institution (TEI) of Thessaly, Greece.
    Kalafata, K
    NanoPhos S.A., Greece.
    Arabatzis, I
    NanoPhos S.A., Greece.
    Effects of nano-sized zinc oxide and zinc borate impregnation on brown-rot resistance of black pine (Pinus nigra L.) wood2013In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, no 4, p. 242-244Article in journal (Refereed)
    Abstract [en]

    In this work, the brown rot resistance of black pine (Pinus nigra L.) wood, pressure-treated in an autoclave with nano-sized zinc borate and zinc oxide dispersions, was investigated. The two formulations based on zinc borate have given encouraging results, indicating fungicide effects of the metal nanoparticles onConiophora puteana. In specific, mean weight losses for P. nigra sapwood exposed to this fungus (one without and one with the addition of a binder) were negligible, that is 0.54% and 0.34%, respectively. On the contrary, the impregnation of pine wood with nano-sized zinc oxide resulted in minimal protection, i.e. 35.9% weight loss. Therefore, nano-sized zinc borate can be utilised in new formulations to impart resistance to wood against the brown rot C. puteana.

  • 334.
    Löv, Morgan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Ceder: Virkesegenskaper och användningsområden2011Independent thesis Basic level (university diploma), 5 credits / 7,5 HE creditsStudent thesis
  • 335.
    Mahnert, Karl-Christian
    et al.
    Norwegian Institute of Wood Technology, Norway ; Georg August University of Göttingen, Germany.
    Adamopoulos, Stergios
    Technological Educational Institute of Thessaly, Greece.
    Koch, Gerald
    Thünen Institute of Wood Research, Germany.
    Militz, Holger
    Georg August University of Göttingen, Germany.
    UV-microspectrophotometry: A method to prove wood-modification with MMF?2014In: European Conference on Wood Modification 2014, 2014Conference paper (Refereed)
    Abstract [en]

    The modification of wood with methylolated melamine formaldehyde resin (MMF) belongs to the group of impregnation modifications. In the course of this study, Koto sapwood samples were impregnated with MMF-solutions in a full-cell vacuum-pressure process. The samples were cured at a maximum temperature of 120 ºC for 24 hours. To characterize the modification, the solution uptake (SU) and weight percent gain (WPG) of the samples were calculated. The fixation of the melamine as parameter for the degree of curing was examined by C/N analysis. Areal UV-microspectrophotometry (UMSP)-scans of ultra-thin transverse sections of an untreated control and MMFmodified samples at 240 nm were recorded. Additionally, photometric point measurements with a spot size of 1 μm2 in the range 230 nm and 350 nm were conducted. UMSP was proven as suitable technique for the quantitative analysis of MMF-modified wood.

  • 336.
    Mahnert, K-C
    et al.
    Georg August University of Göttingen, Germany.
    Adamopoulos, Stergios
    Georg August University of Göttingen, Germany ; Technological Educational Institute of Larissa, Greece.
    Koch, G
    Federal Research Institute of Rural Areas, Germany.
    Militz, H
    Georg August University of Göttingen, Germany.
    Topochemistry of heat-treated and N-methylol melamine modified wood of Koto (Pterygota macrocarpa K. Schum.) and Limba (Terminalia superba Engl. et Diels)2013In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, no 2, p. 137-146Article in journal (Refereed)
    Abstract [en]

    To broaden the knowledge about the chemical changes at the cell wall level of differently modified tropical hardwoods, heat-treated and N-methylol melamine (NMM)-treated samples of koto (Pterygota macrocarpa) and limba (Terminalia superba) were prepared. UV microspectrophotometry (UMSP) was applied at 278 and 240 nm as specific wavelengths to analyze chemical alterations of the samples caused by heat and NMM treatment, respectively. The absorbance of koto exceeded that of limba before and after treatment, potentially due to the higher extractive content of the former. Regardless of the wood species, the absorbance of the samples increased with increasing intensity of the NMM treatment. Additionally, the absorbance of lignin within the spectrum of 230–350 nm was altered due to the NMM treatment. The functionality of applying specific wavelengths for the analysis of different modification methods of wood was proven. However, the comparison with literature did not show differences in the absorbance, which could be assigned to the characteristics of tropical hardwoods.

  • 337.
    Mahnert, K-C
    et al.
    Norwegian Institute of Wood Technolgy, Norway ; Georg August University of Göttingen, Germany.
    Adamopoulos, Stergios
    Technological Educational Institute of Thessaly, Greece.
    Koch, G
    Thünen Institute of Wood Research, Germany.
    Militz, Holger
    Georg August University of Göttingen, Germany.
    UV-microspectrophotometry: A method to prove wood modification with MMF?2015In: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 6, no 1, p. 27-30Article in journal (Refereed)
    Abstract [en]

    The modification of wood with methylolated melamine formaldehyde resin belongs to the group of impregnation modifications. In the course of this study, Koto sapwood samples were impregnated with methylolated melamine formaldehyde resin solutions in a full cell vacuum pressure process. The samples were cured at a maximum temperature of 120°C for 24 h. To characterise the modification, the solution uptake and weight percent gain of the samples were calculated. The fixation of the melamine as parameter for the degree of curing was examined by C/N analysis. Areal UV-microspectrophotometry scans of ultra-thin transverse sections of an untreated control and samples impregnated with methylolated melamine formaldehyde resin at 240 nm were recorded. Additionally, photometric point measurements with a spot size of 1 μm−2 in the range 230 and 350 nm were conducted. UV-microspectrophotometry was proven as suitable technique for the quantitative analysis of wood modified with methylolated melamine formaldehyde resin.

  • 338.
    Mantanis, George
    et al.
    Laboratory of Wood Technology, Greece.
    Adamopoulos, Stergios
    Technological Education Institute of Larissa, Greece.
    Rammou, Ekaterina
    Laboratory of Wood Technology, Greece.
    Physical and mechanical properties of Pinus leucodermis wood2010In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 5, no 1, p. 50-52Article in journal (Refereed)
    Abstract [en]

    The present work reports on the main physical and mechanical properties of Pinus leucodermis mature wood, one of the least studied coniferous species in south-east Europe. Pinus leucodermis heartwood specimens were found to have average density values of 0.73 g cm−3 at equilibrium moisture content of 11.5% and average density of 0.64 g cm−3 under oven-dry conditions. The overall tangential shrinkage was 3.4% and the radial shrinkage was 1.9%. The modulus of rupture was on average 77 N mm−2, while the static modulus of elasticity averaged 7087 N mm−2. The hardness of P. leucodermis heartwood using the modified Janka test was 33.4 N mm−2 in the transverse direction and 48.0 N mm−2 in the longitudinal direction, while its compression strength parallel to grain was approximately 41.6 N mm−2.

  • 339.
    Michalec, Jiri
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Niklasova, Sylvie
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Water uptake of hardwoods2006Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study investigate water uptake in six different species of hardwood in tangential and radial section. Alder (Alnus glutinosa) and beech (Fagus sylvatika) represent semi-diffuse-porous hardwoods. Aspen (Popolus tremula) and birch (Betula pubescens) represent diffuse-porous group; oak (Quercus robur) and ash (Fraxinus excelsior) the ring-porous hardwoods. Spruce (Picea abies) was used as a reference sample.

    Significantly higher water uptake was observed in the diffuse-porous and the semi-diffuse-porous group. Water uptake varied among the species, nevertheless tangential section was more permeable in general. Any impact of density or annual rings width on water uptake was observed. Correlation between ratio of earlywood and latewood and water uptake in dependence on hardwood group was found out. Ring-porous species had low rate of earlywood and low water uptake, whereas diffuse-porous and semi-diffuse-porous hardwoods had high rate of earlywood and high water uptake. Relation between water uptake and microstructure of wood was observed.

  • 340.
    Michalec, Jiri
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Strnad, Pavel
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Present and future use of commercially important European hardwoods2008Independent thesis Basic level (professional degree), 15 credits / 22,5 HE creditsStudent thesis
  • 341.
    Mngomezulu, Lehlohonolo
    et al.
    Stellenbosch University, South Africa.
    Amiandamhen, Stephen
    Stellenbosch University, South Africa.
    Meincken, Martina
    Stellenbosch University, South Africa.
    Tyhoda, Luvuyo
    Stellenbosch University, South Africa.
    Influence of heat curing and aggregates on the properties of phosphate bonded biocomposites2019In: SN Applied Sciences, ISSN 2523-3963, Vol. 1, p. 1-12, article id 1620Article in journal (Refereed)
    Abstract [en]

    There is renewed effort in reducing the carbon footprint of conventional building materials by employing novel phosphate cements. This study investigates the influence of industrial aggregates, namely fly ash, silica fume and calcium carbonate on biocomposite properties. The biomaterials used included pine, bagasse and wattle. The density of the boards produced ranged from 0.82 to 1.16 g/cm3, and the MOE ranged from 410.57 to 1737.87 MPa. The study concluded that biomass type, curing temperature and aggregates have significant effects on the biocomposite properties. The boards produced met the physical property requirements for use as non-load-bearing structures in humid and external conditions.

  • 342.
    Navi, Parviz
    et al.
    EPFL, École Polytechnique Fédérale de Lausanne.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    The thermo-hydro-mechanical processing of wood.2012 (ed. 1)Book (Refereed)
    Abstract [en]

    The fabrication of wood-derived products is numerous and is continuously being developed thanks to its unique advantages: widespread availability, natural renewal, favorable ecological assessment and its flexibility of implementation. Moreover, the polymeric components of wood together with its porous structure confer to it a faculty for transformation exceeding that of other materials.

    Since the dawn of civilization wood has been used in its natural state. Only recently has wood been developed to form a range of products that are increasingly functional, based on a combination of performance and sustainability requirements.

    Since the beginning of the last century, the advance of knowledge on this topic has been constant, mainly through the efforts of systematic scientific research and new types of applications.

    Around the middle of the last century the preliminary work addressing the science and technology of wood was published. The current success in the understanding of its material properties, chemistry, physics and advances obtained in materials science, together with modeling techniques, provided the means for engineers and researchers to be able to engineer wood as a material and to produce new materials and products under controlled processing conditions.

    The intention to overcome difficulties in the processing technologies, as related to wood, requires an interdisciplinary approach. A close co-operation between scientific disciplines such as the anatomy of wood, physics, chemistry and mechanics makes it possible for each to contribute a constructive and complementary part in order to evolve, together, the technologies that relate to the various wood treatments, such as, for example - conservation, drying, machining, shaping and joining, etc.

    One of the emerging eco-friendly treatment methods is the combined use of temperature, moisture and mechanical action, the so called Thermo-Hydro-Mechanical (THM) treatment.  THM processing is implemented to improve the intrinsic properties of wood, to produce new materials, and in order to acquire a form and functionality desired by engineers without changing the eco-friendly nature of the material. These processes can be divided into two major categories; Thermo-Hydro (TH) treatments and Thermo-Hydro-Mechanical (THM) treatments.

    As we pointed out above, wood consists of natural polymeric chains, connecting to each other by hydrogen bands, and in certain parts by covalent bonds. The hydrogen bond is at the origin of its properties to transformation. For example, when wood is put under thermo-hydrous conditions, allowing for the softening of its amorphous components, it can easily deform which makes it possible to consider the application of a large number of industrial processes such as molding, densification, surface densification, bending, shaping, drying at high temperature, etc. Nevertheless, the application of high temperature, however, with or without moisture can damage mechanically, and modify chemically, the polymeric components of wood.

    The intention to gather together in one book the key elements of the chemical degradation of wood constituents under TH processing, the Thermo-Hydro, the Thermo-Hydro-Mechanical behavior, as well as a selection of the principal technologies implemented in TH/THM treatments, constitutes the primary reason of this edition. This work is intended for researchers, professionals of timber construction, as well as students studying the science of materials, wood technology and processing, civil engineering and architecture. This work is not exhaustive or a reference, but intends to deliver an outline of the scientific disciplines necessary to apprehend the technologies of wood THM and its behavior during treatment, as well as during its use.

    This work consists of 11 chapters. The first chapter is devoted to the reasons for TH/THM processing.  The ancient treatments of wood by THM processing are discussed in the second chapter. It is shown that different heat treatment processes have been used to improve the performance of wood and that the use of these processes dates back many thousands of years. The description of the structure and the chemical composition of the components of wood are given in the third chapter. In the fourth chapter, the explanation and modeling of certain THM behaviors of wood is presented. In the first part, the small and large deformations of wood are described, and the constitutive equations of elastic linear, as well as elastic nonlinear behavior of wood, are derived. In the second part the viscoelastic behavior of wood under ambient temperature, constant and variable humidity is described. In the chapter five, the behavior of THM of wood under variable moisture and temperatures (as high as 200°C), is examined by considering that during the processing, at high temperatures, the components of wood undergo certain chemical modifications. In this chapter the effects of the processing parameters: temperature, moisture content and time, on the THM wood characteristics are discussed. The sixth chapter is devoted to the processing of wood densification by THM treatment. In the first part of this chapter various THM wood densification processing methods are discussed and the machines that have been developed in different countries corresponding to open, closed, and mixed processing, are illustrated. In the rest of this chapter the origin and mechanisms of the shape memory and fixation of compression-set by THM treatment are discussed. Chapters seven and eight are devoted respectively to the wood welding by friction techniques and wood surface densification techniques. In both chapters different techniques are discussed and the problems related to these different ‘open systems’ are explained.

    In the recent decades developments in the area of heat treatment have accelerated considerably. At the present time many countries have developed their own wood TH treatments. In chapter nine most of these processing methods are presented and discussed. In chapter ten different wood bending processes: bending of solid-wood, laminated wood bending and other methods like green wood bending and kerfing are presented and different techniques discussed. Also, the theory of solid wood bending is explained. This chapter gives a demonstration of solid wood bending in the laboratory and at industrial levels. Finally, a selection of technologies is presented in the eleventh chapter on the fabrication of reconstituted wood, namely: Fiberboards, Particle boards and panels made of veneers.

    For the benefit wood engineers and other people with an interest in this fascinating industry, we hope that the availability of this material as printed book will provide an understanding of all the fundamentals involved in TH and THM processing of wood.

  • 343. Nikolaisen, L
    et al.
    Daugbjerg Jensen, P
    Zielke, U
    Jirjis, R
    Blomqvist, P
    Göransson, U
    Haglund, N
    Walsh, S
    Thörnqvist, Thomas
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Poulsen, T
    Schulz, G
    Andersen, P
    Skov, S
    Madsen, A.M
    Guidelines for storing and handling of solid biofuels.: NT Method.2008Report (Other academic)
  • 344.
    Nilsson, Bengt
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Extraction of logging residues for bioenergy: effects of operational methods on fuel quality and biomass losses in the forest2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wood products play a key role in the transformation to a more sustainable society based on renewable bio-based resources, together with the positive effects on climate mitigation by replacing fossil fuels. However, to increase the use of forest fuel in practice it is important to understand the effects of handling and storage on its quality and removal of nutrients from the forest. This thesis addresses these effects with special focus on a comparative evaluation of the traditional dried-stacked with “new” and to some extent more controversial fresh-stacked methods for extraction of logging residues from Norway spruce (Picea abies (L.) Karst).

    The results indicate that a normal extraction of logging residues will leave at least 20% of logging residues at the clear-felled area, in accordance with Swedish Forest Agency recommendations. However, the results also indicate that the ambition of the dried-stacked method to leave the majority of the needles well spread over the clear-felled area does not meet these recommendations. In fact, the harvesting operation is more important than the extraction method, with respect to how much logging residues (nutrients) being left in the forest. The results also show that the quality of fuel yielded by the two handling methods differs only to minor extent, indicating that other factors have stronger effects, where “dried-stacked” and “fresh-stacked” logging residues from different clear-felling areas is often similar. Generally, logging residues stored over summer (regardless method), seem to provide sufficiently dry forest fuel, with a needle content of about 5–10%. There is a clear correlation between drying and effective loss of needles from twigs, but the loss does not necessarily mean that the needles will remain in the forest.  However, needle color (green or brown) is not a strong indicator for a reduction in needle content.

    Acceptance of the fresh-stacked method would provide opportunities for the development of new technologies, more efficient use of machinery throughout the whole year, reduced costs, shorter lead times and increased amounts of logging residues extracted from each clear-felled area. This is mainly because it would enable extraction at optimal times from a logistical, financial and/or forestry perspectives.

    Written in English with summary and conclusion in Swedish.

  • 345.
    Nilsson, Bengt
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Blom, Åsa
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Thörnqvist, Thomas
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Hanteringens inverkan på skogsbränslets barrandel och fukthalt: – en jämförande studie mellan grönrisskotning och traditionell brunrisskotning av grot2011Report (Other academic)
    Abstract [sv]

    I föreliggande studie har vi analyserat hur grotens barrandel påverkas av grönrisskotning jämfört med traditionell brunrisskotning. En hypotes har varit att den traditionella brunrisskotningen inte medför så stort barravfall som man tidigare trott. Om grönrisskotning skulle accepteras skulle det öppna möjligheter för nya tekniker, minskade kostnader, kortare ledtider samt ett större totalt uttag från den enskilda avverkningstrakten. Observera att även grönrisskotning ger ett torkat bränsle och inte skall förväxlas med färsk grot. Bestämning av fraktionsfördelning och fukthalt har genomförts i det material som levereras till den energiomvandlande industrin i anslutning till flisning av groten.

    Resultaten visar att grönrisskotning medför en kraftig avbarrning och innehåller betydligt mindre andel barr än färsk grot. Resultatet visar även att traditionellt brunrisskotad grot innehåller en hel del barr. I praktiken innebär det att grönrisskotad grot innehåller dubbelt så mycket barr (ca 8 % av grotens total torrmassa) som den traditionellt brunrisskotade (ca 4 % av grotens total torrmassa) vid leverans till den energiomvandlande industrin. Både grönrisskotning och brunrisskotning ger en tillfredsställande torkning och resultatet visar att det endast skiljer 5 procentenheter i medelfukthalt mellan grönrisskotad (36 %) för och brunrisskotad (31 %) grot.

    Det har även kunnat konstaterats att groten behöver ligga större delen av sommaren i små processorhögar för att uppnå den rekommenderade avbarrningen. All grot som skotas ihop tidigare än augusti månad är därmed att betrakta som mer eller mindre grönrisskotad. Slutsatsen blir att en stor del av den grot som idag levereras till den energiomvandlande industrin snarare är grönrisskotad än brunrisskotad och innehåller ca 5–10 % barr.

  • 346.
    Nilsson, Börje
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Sjödén, Therese
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Nordebo, Sven
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Säll, Harald
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    A method for under bark detection of the wood grain angle radial dependence2007In: Wood Material Science and Engineering, ISSN 1748-0272, Vol. 2, no 3,4, p. 118-129Article in journal (Refereed)
    Abstract [en]

    Twist in wood, being closely related to spiral grain, may cause

    serious problems in building structures, furniture, and joinery. It is therefore of great interest to sort out, at an early stage in the manufacturing process, trees, logs and boards that have an access of spiral grain. The spiral grain pattern is described by a helical deviation of the fibre direction in relation to the longitudinal direction of a living tree or a log and seems to be an indicator for other defects such as compression wood. Remote microwave sensing of spiral grain has received a large interest during the latest two decades. Its development has been impeded by the large variation with moisture content of the microwave properties of wood and by the complexity in modelling the electromagnetic field in a log with spiral grain. A review is presented of a direct method with no requirement of information on moisture content for boards. This procedure has recently been generalized to cylindrical logs and trees having a constant slope of the grain. A further generalization is presented here to allow for the normal spiral grain pattern with radially changing slope of grain in wood under bark. Based on this theory, a measurement procedure is proposed for the detection of wood grain angle with radial dependence, requiring no information on moisture content in the sapwood, also applicable for completely or partially frozen wood. A suitable application would be an instrument to use in the forest for measurements on living trees or logs.

  • 347.
    Nilsson, Daniel
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Thörnqvist, Thomas
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Lagring av flisad grot vid värmeverk: en jämförande studie mellan vinter och sommar förhållanden2013Report (Other academic)
    Abstract [sv]

    Företrädare för den energiomvandlande industrin upplever i vissa fall attdet är skillnader i den inmätta energimängden och den energimängd somlevereras ut till kund. Detta gäller även vid beaktande av verkningsgrad iförbränningsanläggningen.Syftet med studien har varit att identifiera och storleksbestämma deskillnader i energiinnehåll hos två stackar om vardera 1000 m3s flisad grotsom mättes in vid leverans, samt efter tre månaders lagring strax innanförbränning. Studien är genomförd under två tidsperioder den enarepresenterande vinter- och den andra sommarförhållande, dålagringsegenskaperna skiljer sig åt beroende på årstid.Medelfukthalten för groten som flisades under den frusna delen av åretbestämdes vid leverans till 41,5 % och var efter tre månaders lagring 42,8%. Substansförlusten noterades till 5,6 % och energiförlusten till 6,1 %.För den grot som flisades under sommarförhållanden bestämdesmedelfukthalten vid leverans till 32,2 % och efter tre månaders lagringhade medelfukthalten i stacken ökat till 44,6 %. Substansförlusternanoterades till 10,1 % och energiförlusten till 14,1 % under de tresommarmånaderna.Den grot som flisades under vinterförhållanden visade vid leverans på ettfuktigare material jämfört med den grot som flisades och levereades undersommarförhållanden. Däremot ökade fukthalten endast marginellt hosbränslet som flisades under vinterförhållandena medan fukthalten ökadeavsevärt under lagringen för bränslet som flisades undersommarförhållandena.Substansförlusterna i stacken med vinterflisad grot såväl som i stackenmed sommarflisad grot visade sig ligga väl i paritet med vad tidigare 

    studier visat med substansförluster på i storleksordningen 2 – 3 % permånad under de tre månader som studien pågick. Energiförlusterna vardäremot betydligt högre för den stack med sommarflisad grot vilket varväntat då både substansförlusterna och fukthaltsökningen var större.

  • 348.
    Nilsson, Jonaz
    Växjö University, Faculty of Mathematics/Science/Technology, Institutionen för industriella produktionssystem.
    Driftsäkerhet, avbrottsanalys och arbetsmiljögranskning av såglinje2001Independent thesis Basic level (degree of Bachelor)Student thesis
  • 349.
    Nilsson, Jonaz
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Requirements for wood-based lightweight panels intended for furniture and interior use2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Introduction: Throughout many parts of the world, forests exist in one form or another. And for the timber from these forests to be used, it must be processed by, for example, sawing into planks and dried. Studies have shown that profits for the forest owners increase from beneficial processing of these raw materials. An efficient use of this raw material is to process it into lightweight panels. Some general incentives for using lightweight constructions are: economical, technical and environmental. Some general weaknesses with sandwich constructions are more sensitive to impact and bumps, risk for delamination, harder to make fastenings, and more sensitive to the concentration of point loads. This work aims to increase the knowledge of properties and design of wood based lightweight panels used for interiors and furniture. The intention with this knowledge is that it can contribute to the development of lightweight panels.

    Material and method: A lightweight panel of cross glued sandwich type and a cross-glued multi-layered panel with densified face sheets have been used as an example to investigate and understand which parameters are crucial for a lightweight panel, made of wood. The lightweight panel of sandwich construction has been studied to consider the changes of shape brought about by moisture, as well as which mechanical properties this panel has, with a focus on creep deformation. Two methods for reducing the moisture-generated shape changes so as to increase the shape stability of the panel have also been studied. The methods are crossgluing and thermal treatment of the wood material. In the investigations of the panels, primarily quantitative methods in the form of empirical tests have been used. Some numerical simulations describing the moisture-generated shape changes and stresses that arise in the investigated lightweight panels were also made.

    Results and discussion: Cross-gluing of a multi-layered panel and also for the lightweight panel used in this study is a way to reduce the movement in the panel, generated by moisture. The drawbacks with this method are that stresses occur in the panels when the moisture change, and this can lead to a decrease in the shape stability of the panel. Thermal treatment can also be used to decrease the moisture-generated movement in wood, and in this way increase the shape stability of the product. In those cases where the empirical experiments were combined with numerical simulations, there was good agreement between the experimental and the numerical results. With the lightweight panels a weight reduction was achieved from 307 to 540 kg/m3 compared with a solid beech wood panel. The creep deformation of the lightweight panel was better or comparable for 6 of the 8 studied groups, compared to solid beech wood panel. The study also show that is possible to adapt the mechanical properties through its design of this lightweight panel.

  • 350.
    Nilsson, Jonaz
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Bending and Creep Deformation of a Wood-Based Lightweight Panel: An Experimental Study2019In: Wood and Fiber Science, ISSN 0735-6161, Vol. 51, no 1, p. 16-25Article in journal (Refereed)
    Abstract [en]

    When wood is exposed to long-term loading, creep deformation can occur because of its viscoelastic characteristic. The aim of this study was to increase the understanding and knowledge of creep deformation of a wood-based lightweight sandwich-type panel and to see if this type of panel has similar properties for creep as solid wood has. This was done by means of a study based on experiments. The panel studied consisted of two face sheets of beech wood and a core of pinewood struts cross-glued to the face sheets. A solid beech panel was used as a reference. In all, there were 27 samples for the test. The densities of the lightweight panel varied from 165 to 297 kg/m(3), compared with the density of the solid panel of 705 kg/m(3). The study consisted of two parts: a bending test and a creep test. The bending test was used to determine the maximum failure load for the panel. For the creep test, 30% of the original failure load was used. When the results from the bending tests were ranked for load capacity in relation to density, the results for the lightweight panel varied from 9.0 to 18.0 m(4)/s(2), compared with the value of the reference panel at 27.3 m(4)/s(2). This measured how effective the panel was in withstanding bending loads in relation to their density. However, this was not to say that the panel with the highest value also took the highest load in absolute terms. If the creep deformation is instead ranked in relation to density, the results for the lightweight panel varied from 10.4 to 33.7 kg/m, compared with the value of the reference panel at 45.5 kg/m. As with the bending test, these values rank how effective the panel was in resisting creep deformation in relation to density.

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