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  • 501.
    Scheepers, Gerhard
    et al.
    RISE .
    Nilsson, Jonaz
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Johansson, Jimmy
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Mätning av ytspänningar i torkat gran med NIR2017Rapport (Övrigt vetenskapligt)
    Abstract [en]

    In sawmilling, a lot of timber properties are measured online in the sorting and grading of dried timber. This may include moisture content, shape, and a host of other parameters. An important wood property that cannot be measured online is drying stresses, although it is an important parameter for many customers. Since the destructive test methods for stress determination are time consuming, no high frequency routine measurement of the internal stresses is done. In literature, there are a few examples of near infrareds (NIR) capability to detect surface stresses along the fiber direction. There is also an example of stress measurements across the grain on a Japanese wood specie during drying, however, these measurements were always done on a tangential surface. It is unknown whether NIR prediction models can predict surface tension and stress measurements across the grain of dried Norway spruce with varying characteristics, i.e. material from different logs, heart- or sapwood, different year ring orientations, etc. If the technique cannot handle the variation in material properties, such as occurs in a sawmill environment, this means that a simple NIR measurement would not be sufficient to predict the surface tension in industry. This study investigated whether surface stresses in mechanically loaded as well as dried spruce samples with varying material properties can be predicted by NIR models. The measurement data from some mechanically loaded samples showed a correlation between the predicted and actual stress values, but many other samples showed no correlation. Moreover, the data for a single sample could show a good correlation, but the prediction could be at an incorrect stress level. As for the dried samples, NIR models were good at separating the conditioned and nonconditioned samples, but had no predictive power concerning the stress level. The models used to predict the stress level in mechanically loaded samples, were also used to predict the stress in the dried samples, but there was no correlation between the measured strain and the predicted stress level. Therefore, it is concluded that there are no clear indication that NIR measurements can be used in an industrial application for predicting the surface stress level of dried Norway spruce boards.

  • 502.
    Scheepers, Gerhard
    et al.
    RISE Research Institutes of Sweden.
    Wiberg, Pär
    Alent Dynamic.
    Johansson, Jimmy
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    A method to estimate wood surface moisture content during drying2017Ingår i: MADERAS: Ciencia y Tecnología, ISSN 0717-3644, E-ISSN 0718-221X, Vol. 19, nr 2, s. 133-140Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method to estimate the surface moisture content below the fibre saturation point that is a function of the surface temperature, wet- and dry bulb temperatures, equilibrium moisture content, and fibre saturation point was evaluated. The method is based on the premise that the surface temperature is solely influenced by the surface moisture content and the climate that the surface is exposed to. The prediction model contends that the surface moisture content is equal to the fibre saturation point when the surface temperature is equal to the wet bulb temperature, and equal to the equilibrium moisture content when the surface temperature is equal to the dry bulb temperature, with a linear interpolation between those two points. The model thus predicts that the average moisture content of a thin piece of veneer can be predicted with fairly good accuracy. Also, when drying boards in a fast changing climate, e.g. fan reversals in industrial kilns, the surface temperature and surface moisture content should change as abruptly as the climate does. Additionally, the surface moisture content should correlate to the known drying phases, with a consistently high surface moisture content during the capillary phase when the wet line is close to the surface, and a quickly decreasing surface moisture content when the wet line moves into the wood during the transition to the diffusion phase. The prediction model was tested in these three scenarios and the results suggest that the basic premise is reasonable, and that the method is useful for surface moisture content estimation.

  • 503.
    Scholz, Gunthard
    et al.
    Univ Gottingen, Germany.
    Adamopoulos, Stergios
    Univ Gottingen, Germany.
    Militz, Holger
    Univ Gottingen, Germany.
    Migration of blue stain hyphae within wax treated wood2011Ingår i: IAWA Journal, ISSN 0928-1541, Vol. 32, nr 1, s. 88-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The colonization of wax impregnated pine sapwood (Pinus sylvestris L.) and beech (Fagus sylvatica L.) by blue stain fungi and their hyphal migration within the treated wood was investigated. Neither the hydrophobation effect nor the physical presence of the congealed wax deposits could impede fungal growth on the surface. However, in contrast to the untreated controls, there was a lower occurrence of hyphae in wax-treated wood. Blue stain fungi grew mainly near the cross cut as well as in empty spaces such as micro-capillaries, parenchyma tissue or other wax free zones of treated wood.

  • 504.
    Schweigler, Michael
    Vienna University of Technology.
    A numerical model for slip curves of dowel connections and its application to timber structures2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Wood as a natural and renewable material currently experiences a revival as structural building material. New technologies and a new design standard request appropriate, modern design methods for timber structures. Particularly, the design of modern timber connections is of importance since more challenging timber constructions demand ambitious connections. Most connections in timber structures are compliant in the sense that relative deformations between the connected structural elements occur during load transfer. In particular dowel connections exhibit this behavior since load transfer in dowel connections is based on the compliant embedment behavior of stiff steel dowels in wood.

    The aim of this thesis is to develop a model for a consistent calculation of the load-deformation relationship of connections. Additionally, this model is applied to timber structures to study the influence of compliant connections on the structural behavior. As a basis for the modeling of dowel connections, properties of single-dowel connections are presented. Different responses of wood in case of different loading directions, as well as several models for the calculation of single-dowel slip curves are discussed. Significant differences in the predicted load-deformation behavior of single-dowels can be observed among these approaches. A sub-model is used to determine realistic single-dowel slip curves for arbitrary connection configurations. Furthermore, the state-of-the-art approach for the determination of connection slip curves of multi-dowel connections is discussed. The restriction of this approach to some specific design situations is highlighted. These limitations of the current design approach are the motivation to develop a model for the calculation of slip curves of multi-dowel connections. This model enables a straight forward determination of member forces and connection slip curves for an arbitrary set of deformations. The single calculation steps and the feasibility of application on arbitrary connection configurations are discussed. Furthermore, a modification of the model to determine the deformation and force distribution within the connection for specific member forces is presented.

    Finally, the model is applied to different connections to illustrate their behavior for simple design examples. Moreover, connection slip curves have been implemented in the structural analysis of a static indetermined system in order to illustrate the necessity of considering the compliance of connections in the design of timber structures. It is shown that negligence of the connection slip may lead to uneconomic or even unsafe timber structures. Furthermore, the importance of an exact definition of the connection slip curves is discussed. Even insignificant differences from standard configurations may lead to remarkable changes in the connection behavior and, consequently, in the behavior of the structure. Moreover, a considerable influence of the used method to describe the single-dowel behavior on the behavior of the connection and, consequently, on the structural behavior has been found.

  • 505.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Experimental characterization and parameterization of the load-to-grain angle dependent embedment behavior of dowel-type fasteners in laminated veneer lumber (LVL)2016Rapport (Övrigt vetenskapligt)
  • 506.
    Schweigler, Michael
    Vienna University of Technology.
    Nonlinear modeling of reinforced dowel joints in timber structures: a combined experimental-numerical study2018Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Steel dowels are indispensable elements for the design of joints in modern timber structures. Dowels are broadly used because of their flexibility in design and easy assembling on-site, as well as due to their advantageous mechanical behavior. Recent developments in reinforcement techniques allow for designing ductile dowel joints, which exhibit nonlinear slip behavior. However, currently applied limit state approaches for calculation of connection strength are not able to fully exploit the potential of dowel joints. This calls for development of more advanced calculation methods, which was aimed for in this thesis.

    For thorough understanding of the complex mechanical behavior of dowel connections, application of a so-called multiscale approach is advantageous. Thereby, nonlinear loaddeformation behavior of dowel connections is studied on different length scales, from the scale of connection components, up to the joint level. The aim of this thesis was to exploit knowledge from lower scales in models that finally allow for nonlinear analysis of timber structures. In the work at hand, this was achieved by a combined experimental-numerical analysis.

    Experimental studies on the nonlinear embedment slip of ductile dowel connections, and its relation to the orthotropic material behavior of wood, was one of the objectives of this work. Breaking new ground by testing up to large dowel displacements, at various angles to the grain, for unconstrained and constrained lateral displacement conditions, required development of new testing procedures and test setups. Test results gave access to nonlinear embedment slip curves and showed their dependence on loading direction and lateral displacement conditions.

    In the next step, embedment slip data were exploited in modeling of single-dowel connections. Beam-on-nonlinear foundation modeling was applied for this purpose. Validation of connection tests and a parameter study not only highlighted suitability of the calculation method, but allowed for gaining insight into limit states. Thus, beam-on-foundation modeling was found to be an attractive alternative to advanced 3D FEM models for engineering design.

    Parameterized equations for regression analysis of nonlinear slip curves, and interaction curves describing the grain angle dependence of mechanical parameters, were summarized in a literature review. With these equations at hand, a multi-dimensional parameterization method for the nonlinear slip as a function of the load-to-grain angle was developed. This method was applied to experimental data derived in embedment and single-dowel connection tests as well as in simulations. Analytical equations for connection slip are expected to facilitate engineering modeling at the single-dowel connection and joint level, respectively.

    Joint modeling aimed at establishing a calculation method suitable for engineering design with an attractive trade-off between modeling effort, calculation time and accuracy. This was tackled by a semi-analytical model based on nonlinear elastic springs for the dowel slip and rigid connection members. Thereby, global joint slip, and thus stiffness and strength of joints, as well as local load distribution within joints can be predicted. This model proved to be suitable for single-dowel-based and joint-based design concepts. Calculation examples showed pronounced influence of loading direction dependence and nonlinearity of dowel slip on local load distribution, as well as on global joint slip. Influence of interaction between internal forces on the joint stiffness became obvious from structural analysis with nonlinear joint slip.

    This work covers a combined experimental-numerical analysis of the slip behavior of ductile dowel joints, from the wood embedment and steel dowel bending behavior, the single-dowel slip, to the joint behavior, with final application in nonlinear structural analysis. Presented models predicted nonlinear slip with suitable accuracy and efficiency. Application of nonlinear joint slip in structural analysis showed the potential of ductile dowel joints, which could be exploited in engineering design by the herein presented multiscale modeling strategy.

  • 507.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Load Direction Dependency of the Embedment Behaviour of Dowel-Type Fasteners in Laminated Veneer Lumber2014Ingår i: 16th International Conference on Experimental Mechanics (ICEM16), July 7-11, 2014, University of Cambridge, UK, Cambridge, UK, 2014Konferensbidrag (Övrigt vetenskapligt)
  • 508. Schweigler, Michael
    et al.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Eberhardsteiner, Josef
    The influence of displacement boundary conditions on the embedment behavior of dowel-type fasteners2016Ingår i: Presented at 33nd Danubia-Adria Symposium on Advances in Experimental Mechanics, Portorož, Slovenia, 2016, 2016Konferensbidrag (Övrigt vetenskapligt)
  • 509.
    Schweigler, Michael
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Engineering modeling of semi-rigid joints with dowel-type fasteners for nonlinear analysis of timber structures2018Ingår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 171, s. 123-139Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Plastic analysis in engineered structures requires ductility of structural components, which in timber structures is primarily provided by joints made of dowel-type fasteners. A prerequisite for nonlinear analysis is realistic modeling of joint stiffness and load distribution in dowel-type joints. A joint model suitable for structural analysis is presented and validated in this contribution. The semi-analytical joint model is based on kinematic compatibility and equilibrium considerations. It accounts for local fastener slip by means of nonlinear elastic springs. Influences of nonlinearity and orientation dependence of fastener slip are assessed. Elastic deformations of the timber in between dowels are however neglected. The model allows for predicting global joint stiffness, as well as load distribution within the joint, taking explicitly the effect of simultaneously acting internal forces into account. Model validation builds upon an experimental database that spans from embedment testing on the material scale up to joint testing on the structural scale. Application examples demonstrate the broad applic- ability of the model for structural analysis. Moreover, they illustrate effects of assumptions of fastener slip on the joint and structural behavior. Limitations, as well as pros and cons of these assumptions are discussed. Special attention is drawn to load distribution within the joint, since it is important for fastener-based design, currently prescribed by the European design standard. Load distribution in joints is also important for verification against brittle failure modes. As an alternative to fastener-based design, joint-based design, by means of a framework for applying the presented model to plastic design of timber structures with ductile joints, is proposed.

  • 510.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    A Novel Approach for the Load-Displacement Behavior of Single-Dowel Connections in Laminated Veneer Lumber2016Ingår i: 17th International Conference on Experimental Mechanics, Rhodes, Greece, July 3-7, 2016, 2016Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The load-to-grain orientation dependence of the mechanical behavior of single-dowel connections is discussed in this contribution. The effect of the anisotropy of wood was experimentally assessed by means of a novel biaxial test set-up. Thus, lateral reaction forces in addition to forces parallel to the prescribed displacement direction could be quantified. Material properties of the components, namely the steel dowel and the Laminated Veneer Lumber were measured as well. This comprehensive experimental dataset was further exploited in an engineering model for single-dowel connections.

  • 511. Schweigler, Michael
    et al.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hochreiner, Georg
    Eberhardsteiner, Josef
    An engineering modeling approach for the load-deformation behavior of multi-dowel connections in timber structures2017Ingår i: EMI 2017: Engineering Mechanics Institute Conference, June 4-7, 2017, San Diego, 2017Konferensbidrag (Refereegranskat)
  • 512.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    An Engineering Modeling Approach for the Non-Linear Load-Displacement Behavior of Single Dowel Connections: Parameter Study2016Ingår i: Proceedings of the 2016 World Conference on Timber Engineering (WCTE), Vienna: Vienna University of Technology , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    A beam on non-linear elastic foundation model for consistent determination of the non-linear loaddisplacement behavior of single dowel connections is presented. The influence of certain parameters, like the load-tograin direction or the side member thickness on the connection behavior is demonstrated by means of a parameter study and compared to experimental findings.

  • 513. Schweigler, Michael
    et al.
    Bader, Thomas K.
    Hochreiner, Georg
    Eberhardsteiner, Josef
    Ein baustatischer Modellierungsansatz für das Last-Verformungsverhalten von Stabdübelgruppen im Ingenieurholzbau2014Konferensbidrag (Övrigt vetenskapligt)
  • 514. Schweigler, Michael
    et al.
    Bader, Thomas K.
    Hochreiner, Georg
    Eberhardsteiner, Josef
    Experimental Characterization of Dowel Connections beyond the Elastic Domain2015Ingår i: Presented at 32nd Danubia-Adria-Symposium (DAS 32), Zilina, Slovakia, 2015, s. 62-63Konferensbidrag (Övrigt vetenskapligt)
  • 515.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Load-Deformation Behavior of Single Dowel Connections in Timber Structures2015Konferensbidrag (Övrigt vetenskapligt)
  • 516.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Lemaître, Romain
    University of Lorraine, France.
    Parameterization equations for the nonlinear connection slip applied to the anisotropic embedment behavior of wood2018Ingår i: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 142, s. 142-158Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nonlinear numerical models for the engineering design of mechanical connections in anisotropic materials require nonlinear material behavior of their components, which are essentially determined by material or structural testing. Herein, a multi-step approach for the parameterization of the nonlinear and anisotropic connection slip behavior is presented and applied to the ductile embedment behavior of steel dowels in wood. For this purpose, previously proposed regression functions for the slip behavior are reviewed, and further possible equations are discussed. Their suitability in the description of typical shapes of slip curves observed in connection testing is assessed before certain combinations are applied to an experimental dataset of embedment tests of steel dowels embedded in Laminated Veneer Lumber. The dependence of the regression parameters on the displacement range in the experimental dataset and the benefit of using parameters with a physical interpretation for being able to exploit connection test data reported in literature is highlighted.

  • 517.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Unger, Gerhard
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Load-to-grain angle dependence of the embedment behavior of dowel-type fasteners in laminated veneer lumber2016Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 126, s. 1020-1033Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Load-to-grain angle dependence of the embedment behavior of steel dowels in laminated veneer lumber, as a consequence of the anisotropic material behavior of wood, is experimentally investigated in this study. As a novel issue, in addition to the stress dependence, the displacement path of the dowel depend- ing on the load-to-grain angle, is discussed. Full-hole embedment tests of screw-reinforced LVL speci- mens up to dowel displacements of two times the dowel diameter and thus, representative for highly ductile dowel connections were conducted. Tests were performed with unconstrained lateral displace- ment boundary conditions of steel dowels with a diameter of 12 mm and 16 mm. Surface deformations were monitored with a full-field deformation measurement system. Increasing the load-to-grain angle caused reduced quasi-elastic limits and loading stiffness. However, for load-to-grain angles of 60 and higher, a pronounced displacement-hardening effect, leading to high embedment stresses at large dowel displacements, was observed. For the investigated dowel diameters, surface strains and plastic deforma- tions around the dowel indicate an almost dowel diameter independent load bearing area, which might explain higher nominal embedment stresses and consequently a more pronounced hardening effect of the smaller dowel diameter. Dowel displacements perpendicular to the initial loading direction, i.e., non- linear displacement paths of the dowel, were related to the anisotropic stiffness of wood and densifica- tion effects close to the dowel. The established experimental dataset was compared to current European timber engineering design equations and could serve as input to analytical and numerical models of dowel connections. 

  • 518.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Constrained displacement boundary condition in embedment testing of dowel-type fasteners in LVL2017Ingår i: Strain, ISSN 0039-2103, E-ISSN 1475-1305, Vol. 53, nr 6, artikel-id e12238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the loading orientation with respect to the grain direction of wood and the influence of the lateral dowel displacement boundary condition on the embedment behaviour of steel dowels in laminated veneer lumber (with parallel-laminated veneers) are investigated in this study. For limit states of the lateral boundary condition, the load-displacement behaviour was experimentally studied by means of full-hole embedment tests on screw-reinforced laminated veneer lumber, for two dowel diameters and up to large dowel displacements. A novel biaxial test set-up is proposed for embedment tests with constrained lateral dowel displacement boundary condition, in order to quantify laterally evoked reaction forces. Corresponding forces were found to change orientation with increasing dowel displacement and amounted to about 20% and 40% of the vertical reaction force for dowel displacements of 5 mm and twice the dowel diameter, respectively. The influence of the lateral displacement boundary condition was highlighted by comparison of the test data with a previously established data set for unconstrained embedment testing. Constrained loading showed a stiffer response and higher nominal embedment stresses, as well as a more pronounced displacement hardening, compared to unconstrained loading.

  • 519.
    Sehlstedt-Persson, Margot
    et al.
    Luleå University of Technology.
    Ahmed, Sheikh Ali
    Luleå University of Technology.
    Metodutveckling för mögeltestning av trä - förstudie: Slutrapport2014Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Syftet med denna förstudie har varit att utveckla enkla och robusta forcerade mögeltester på trä som kan följas och utvärderas kontinuerligt i forskningsprojekt som bedrivs inom beständighetsområdet vid LTU och SP Trätek i Skellefteå. Testerna som gjorts i klimatskåp bygger på naturlig kontaminering och klimatval som gynnar mögeltillväxt.De metoder som utvecklats gör inte anspråk på att kunna erbjuda jämförelser med andra etablerade metoder utan enbart jämförelser inom batcher som ingår i de material- och processvariabler som studeras, exempelvis inom virkestorkning, värmebehandling och impregneringsmetoder.I förstudien utvärderades ett antal olika klimatval i ett klimatskåp som användes i försöken. Mögelpåväxt gynnas av stabil och hög RF, mörker och stillastående luft. Därför täcktes glasdörren till skåpet med svart plast och övre delen av klimatskåpet skärmades av med en mellanplåt eftersom en fläkt cirkulerar luften i kammaren nedre delar. I den övre delen av klimatskåpet gjordes noggranna mätningar av klimatet för att säkerställa ett jämnt och stabilt klimat i olika positioner.Mögelkontaminerat furumaterial sparat från tidigare TCN projekt användes som ”smittokälla” genom att placeras i klimatskåpets nedre del vid valt klimat under 2 dygn för att infektera kammaren med mögelsporer. Därefter placerades försöksmaterialet i klimatskåpets övre del. Smittokällan dvs. det kontaminerade materialet befann sig i skåpet under hela försöket. Inspektion av mögelpåväxtengjordes regelbundet fram tills beslut togs att avbryta försöket och utvärdera mögelpåväxten. Den utvärderingsmetod som används för att bedöma mögelpåväxt bygger på en visuell bedömningsskala översatt i ”praktisk användning” som utarbetats i tidigare TCN-projekt.Den lämpligaste metoden bedöms vara att använda klimatskåpets ”set-points” +27°C/95 % RF samt att avbryta försöket efter ca 12-14 dagar. Mögelgraderna på de undersökta proverna har då varit av samma omfattning som efter ca 100 dagars forcerat utomhustest beskrivit i tidigare TCN-projekt.Den framtagna metoden har använts i fyra ”skarpa” studier som publicerats i vetenskapliga tidskrifter. Detta får ses som att projektet varit lyckat och utgör ett viktigt vetenskapligt bidrag.Metoden beskrivs i detalj i en av dessa publikationer som finns som bilaga till denna rapport nämligen: “Development of a new rapid method for mould testing in a climate chamber: Preliminary tests.” Ahmed, S. A., Sehlstedt-Persson, M. & Morén, T. jul 2013 i :Holz als Roh- und Werkstoff .71 ,4 ,s. 451-461.11 s.Den framtagna metoden har fungerat mycket bra. Metoden har följande fördelar:* Den är enkel, robust och billig.* Mögelpåväxten kan följas på plats.* Det är möjligt att få svar redan efter två veckor på inverkan av olika variabler som undersöks.* Enkel kontaminering – ingen uppodling av speciella mögelarter.* Upp till 44 stycken prover kan ingå i en batch, beroende av dimension.Metoden har följande nackdelar:* Ingen standardiserad metod dvs. det är inte möjligt göra jämförelser mellan olika försöksomgångar utan endast möjligt att göra ”inom-batch” jämförelser.* Ingen kontroll av vilka mögelarter som angriper virket.

  • 520.
    Sehlstedt-Persson, Margot
    et al.
    Luleå University of Technology.
    Persson, Fredrik
    SP Trä.
    Karlsson, Olov
    Luleå University of Technology.
    Ahmed, Sheikh Ali
    Luleå University of Technology.
    Virkestorkningens inverkan på impregnerbarhet i furusplint – Del II: Delrapport 12013Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Projektets målsättning är att undersöka om och hur virkestorkning påverkar impregnerbarhet i furusplint med vattenbaserat kopparmedel, samt att ge rekommendationer om hur torkningsbetingelserna kan göras så gynnsamma som möjligt för ett bra impregneringsresultat. Det bör tydliggöras att det virke som impregnerats i denna studie inte kommer att säljas inom detaljhandeln. Virket anses inte heller vara representativt för impregnerat virke då det har impregnerats vid fuktkvoter som avsiktligt avviker från normala förhållanden och som kan antas vara ogynnsamma för inträngningen. Virket impregnerades enligt Nordiska Träskyddsföreningen (NTR) klass AB.

    I delsteg 1 som avrapporteras i denna rapport, har huvudfrågan varit att undersöka inverkan av fuktkvotsnivå och maxtemperatur under torkningen på impregneringsresultatet. Försöksmaterialet har bestått av totalt 553 hyvlade bräder och plank (28 resp. 48 mm). Både planken och bräderna sågades fram ur centrumutbyte och innehöll därför kärnved. Virket torkades industriellt vid 60°C och 80°C maxtemperatur till tre målfuktkvoter: 24 %, 18 % och 10 %. Efter impregnering har samtliga virkesstycken kapats upp var 50:e cm och impregneringsresultat har analyserats visuellt enligt NTR:s bedömningsgrunder. Vissa kemiska analyser har även utförts för att undersöka om och hur extraktiver och fetter kan förklara impregneringsmissarna i bräderna.

    Undersökningen visar att virkesdimension, fuktkvot och temperaturnivå har betydelse för impregneringsresultatet. Totalt sett fanns det fler missar i planken än i bräderna. Plank och bräder uppvisar dessutom något olika beteende: för bräder är resultatet mera tydligt vilket även framkom vid multivariat dataanalys (MVDA) på medelvärdesnivå: högre temperatur och högre fuktkvot visar minst impregneringsmissar hos brädgrupperna. För plankgrupper erhölls överhuvudtaget inga MVDA-modeller. Även för plank hade den högre temperaturen i medel bättre impregneringsresultat. Sambandet hög fuktkvot och god impregnerbarhet är inte lika tydligt för plank, möjligen att kombinationen låg temperatur och låg fuktkvot är ogynnsam.

    Densitetsvariationerna visade sig vara tämligen liten och inga låga/höga extremvärden fanns i försöksmaterialet. Vid MVDA framkom ändå tendenser att det hos bräder var gynnsamt ur impregneringssynpunkt med högre densitet.

    Kemiska analyser visar inga dramatiska omfördelningar av extraktiver under torkning som förklaring till impregneringsmissar. Detekterbara fetter och hartssyror var dock lägre i ytliga än i inre delar av splintveden troligen beroende på oxidativ förnätning av deras struktur under torkningen.

    Sammanfattningsvis blir tolkningen att torktemperatur, fuktkvotsintervall och virkesdimensioner har betydelse för impregneringsresultat men att det finns ett antal okända materialvariabler som har stor inverkan på resultatet på individnivå. Även om torkningsbetingelserna görs så gynnsamma som möjligt för impregnering förekommer individer som har allvarliga genomgående missar.

  • 521.
    Sehlstedt-Persson, Margot
    et al.
    Luleå University of Technology.
    Wamming, Thomas
    SPTrätek.
    Karlsson, Olov
    Luleå University of Technology.
    Ahmed, Sheikh Ali
    Luleå University of Technology.
    Modern torknings inverkan på impregnerbarhet i furusplint: Förstudie2011Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Under senare år rapporteras i Sverige för vissa impregneringsmedel en kraftig ökning av antalet underkända prov och då speciellt för kopparbaserade vattenlösliga medel. På några års sikt, när konsekvenserna av impregneringsmissar blir synliga hos slutanvändaren genom att rötskadat virke måste bytas ut, beräknas kostnaderna kunna uppgå till en halv miljard årligen. Orsakerna till inträngningsproblem diskuteras och en av många teorier är att virkestorkningen är en av huvudorsakerna. Målet med denna förstudie har varit att identifiera relevanta process- och materialvariabler som misstänks inverka på impregnerbarheten i furusplint. Resultat från impregneringsförsöken i denna förstudie visar att fuktkvotsnivån i bräder efter torkning är viktig för impregneringsresultatet. Bäst inträngning erhölls vid högre fuktkvotsnivåer än vad som vanligen används vid anläggningarna idag: i fuktkvotsintervallet 20-25 % var andelen missar lägst medan andelen missar ökade påtagligt vid sjunkande fuktkvot. En rekommendation är att inte övertorka virke som ska impregneras. Detta är vanligt speciellt vid torkning av tunna dimensioner i äldre brädkanaler.Resultat från denna förstudie sammanfattas enligt följande•Inverkan av fuktkvotsnivå vid impregnering är viktig. Bäst inträngning i bräder erhölls i fuktkvotsintervallet 20-25 %, dvs. vid högre fuktkvot än vad som vanligen görs medan missarna ökade påtagligt vid sjunkande fuktkvot. •Resultaten pekar på att splintvedsdensiteten tycks spela roll för impregnerbarheten: högre densitet tenderar att vara bättre ur impregneringssynpunkt. •Olika typer av impregneringsmissar noteras. Vissa typer har en tydlig koppling till vedanatomiska detaljer medan andra missar kopplas till process och yttre form.•Anrikning av näring mot splintvedsytor som sker vid forcerad torkning kan i vissa fall ha försvårat inträngning av träskyddsmedel.•Vedanatomiska studier visar att– axiella kådkanaler sannolikt spelar en viktig roll för inträngning av träskyddsmedel– parenkymcellers hartsinnehåll i splintved kan blockera inträngning via märgstrålar•Tomografering indikerar att hög splintvedsdensitet är gynnsamt för inträngning av träskyddsmedel. Detta överensstämmer med iakttagelsen att axiella hartskanaler är viktiga för inträngning av träskyddsmedel eftersom axiella hartskanaler främst finns i sommarved och hög densitet förknippas med hög sommarvedsandel. •Kemisk analys indikerar att lokal skillnad i extraktivämneshalt kan vara en av förklaringarna till impregneringsmiss i splintved. •I fortsatta studier är tomografering ett kraftfullt analysverktyg för att se inträngningsmissar i rått tillstånd.

  • 522.
    Setijono, Djolo
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Sandberg, Dick
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Customer Value Strategy and Customer Value Management for Competitive Wood-Flooring Manufacturers: Litterature review2005Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This literature study describes the potential contributions of Customer Value Strategy and Customer Value Management if they are implemented in wood floor manufacturing, as the "new" approach towards competitiveness.

    The growing market for wood floor products is creating an opportunity for the industries in this sector to make economic value of their offerings. The customers of flooring products often have a prejudice that wood-flooring materials are costly compared to other types of flooring material. This is apparently caused by a high recurring cost during the use of the product that makes the life cycle cost (LCC) of wood floor is amongst the highest, despite the lower initial cost of the product.

    In the other hand, the customers are not always sensitive to the price if they are aware about the benefits they get exceed their sacrifices. This is the main reason that the wood floor manufacturer should focus on customer value rather than barely on product price. The cost would still be important consideration, but the perspective needs to be extended to include costs during the life cycle of the product (or the period of ownership).

    Improving the benefits and reducing the sacrifices are the core idea of Customer Value Strategy and Customer Value Management. These concepts require an understanding of what the customer value and would value as well as excellent performance on product, process, and production. A proper implementation of Customer Value Strategy and Customer Value Management would strengthen manufacturing competitiveness.

  • 523.
    Sidorova, Ekaterina
    et al.
    Luleå University of Technology.
    Ahmed, Sheikh Ali
    Luleå University of Technology.
    Diego, Elustondo
    Luleå University of Technology.
    Wood thermal-modification at Luleå University of Technology2014Ingår i: Final Cost Action FP0904 Conference “Recent Advances in the Field of TH and THM Wood Treatment” May 19-21, 2014, Skellefteå, Sweden: Books of Abstracts / [ed] Mojgan Vaziri, Dick Sandberg, Skellefteå: Luleå tekniska universitet , 2014, s. 75-75Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Wood Physics group at Luleå University of Technology (LTU) has the vision of transforming Swedish solid wood into the material of choice for the renewable economy of the future. To realize that vision, the group believes, stability and durability of local softwood species must be enhanced at a reasonable cost without jeopardizing the natural beauty of this environmentally friendly material. One of the methods for enhancing stability and durability of solid wood is thermal modification, and LTU's Wood Physics group has vast experience in developing and evaluating thermal modification process. In simple words, thermal modification involves exposing the wood to relatively high temperatures, between 160o C and 240o C depending on the products and technologies used, and in the absence of oxygen to avoid degradation of the wood by combustion. It has been proved that these relatively high temperatures modify the chemical structure of the wood polymers (cellulose, hemicellulose and lignin), and wood becomes less prone to absorb moisture from the environment and more resistance to biological degradation. There are a number of thermal modification methods that have been implemented in Europe at the commercial level, such as ThermoWood® and WTT thermo-treatment. ThermoWood® process is performed under normal atmospheric pressure with superheated steam containing as little oxygen as possible. The wood is first dried to almost 0% moisture content with steam temperatures up to 130°C, and then exposed to steam temperatures between 185°C to 212°C for a few hours. Afterward the vapor temperature is reduced to below 90°C to saturate the steam and allow the wood regain moisture. The WTT thermotreatment is performed with saturated steam under pressure up to 20 bars and temperatures between 160°C and 210°C, so the wood is not dried during the process. In the last years, LTU's Wood Physics group has performed several studies in collaboration with local wood producers interested in the evaluation and optimization of thermal modification processes. To study thermal modification in laboratory, LTU's Wood Physics has built pilot scale kiln/thermal-modification unit that fits through the field of view of a CT-scanner unit specially adapted for wood material studies. This combined equipment allowed measuring wood density profiles through entire thermal modification process, thus providing valuable information about the effect of the process conditions in the material. More recently, LTU's Wood Physics group became interested in the process of thermal modification by boiling in linseed oil for 2 to 4 hours. This technology is available in the market, but the novelty at LTU was the implementation of an additional oil impregnation cooling phase in which the wood is submerged in cool oil after thermal modification. This creates a sudden contraction of the gases inside the wood, which in turn draws considerable amounts of oil into the wood. The authors believe that this combined thermal-modification/oil-impregnation treatment offers a simple but effective methodology for simultaneously: 1) enhance the stability and durability of solid wood, 2) impregnate the wood surfaces with oil for increasing the repellency to moisture. This presentation includes an example of the combined thermal-modification/oil-impregnation treatment applied to common Swedish softwood and hardwood species. Both species were treated by using the WTT heat treatment technology and impregnated with different types of preservative oils. After impregnation, the samples were tested for water repellency, dimensional stability, and resistance to mould. Water repellency and dimensional stability were assessed for both liquid water and air relative humidity, and the resistance to oil leaching was determined by exposing the treated wood to cycles in which the samples absorbed water by immersion and then release the water under vacuum. As expected, the treatments showed a significant improvement in the water repellency and dimensional stability of the wood. Overall, untreated wood was more stable after thermal modification, and thermally modified wood was more stable after oil impregnation. The resistance to mould was evaluated by using an accelerated technique also developed by the Wood Physics group at Luleå University of Technology. The technique consists in placing the wood samples in the upper zone of a conditioning chamber in which there are other pieces of wood already infected by mould in the lower zone. Typically, the source of mould is pine sapwood infected with mould of aspergillus, rhizopus, penicillium genus along with other various species, and the test samples are exposed approximately 20 days to the infected environment. After incubation, the incidence of mould over the surfaces is graded in scale from 0 to 6 based on the visual assessment of two independent observers. The results of the study showed that some of the oil impregnation treatments did not significantly improved mould resistance, and it was still questionable whether the oil would not leach from the wood when the products are in service. Future research in wood modification would be certainly needed to find the right thermal-modification/oil-impregnation combination for the right application, as well as to realize the vision of transforming solid wood in the material of choice for the renewable economy of future.

  • 524.
    Sint, KM
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Georg-August-University Göttingen, Germany ; Technological Educational Institute of Larissa, Greece.
    Koch, G
    Federal Research Institute of Rural Areas, Germany.
    Hapla, F
    Georg-August-University Göttingen, Germany.
    Militz, H
    Georg-August-University Göttingen, Germany.
    Impregnation of Bombax ceiba and Bombax insigne wood with a N-methylol melamine compound2013Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 47, nr 1, s. 43-58Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methylated N-methylol melamine (NMM) is known for its ability to enhance physico-mechanical properties, anti-fungal ability, and hydrophobicity and was therefore used to impregnate two less used and non-durable wood species from Myanmar, Bombax ceiba and Bombax insigne. Solution uptake, weight percent gain and nitrogen content were increased by increasing melamine concentrations with B. ceiba always achieving higher values compared with B. insigne. According to the leaching results, a higher degree of condensation after curing as well as a better crosslinking of NMM could be obtained at higher temperatures. However, both curing temperatures used (90 and 120 °C) resulted in almost the same amount of nitrogen fixed in the cell wall. UV microspectrophotometry confirmed the penetration of the NMM into different morphological regions of wood tissues, which was again supported by the analysis of point measurement spectra of treated and untreated specimens.

  • 525.
    Sint, KM
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Georg-August-University Göttingen, Germany ; Technological Educational Institute of Larissa, Greece.
    Koch, G
    Federal Research Institute of Rural Areas, Germany.
    Hapla, F
    Georg-August-University Göttingen, Germany.
    Militz, H
    Georg-August-University Göttingen, Germany.
    Wood anatomy and topochemistry of Bombax ceiba L. and Bombax insigne Wall2013Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, nr 1, s. 530-544Artikel i tidskrift (Refereegranskat)
  • 526.
    Sint, KM
    et al.
    Univ Gottingen, Germany.
    Militz, H
    Univ Gottingen, Germany.
    Hapla, F
    Univ Gottingen, Germany.
    Adamopoulos, Stergios
    Technol Educ Inst Larissa, Greece.
    Treatability and penetration indices of four lesser-used Myanmar hardwoods2011Ingår i: Wood research, ISSN 1336-4561, Vol. 56, nr 1, s. 13-22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Depletion of Myanmar's top commercial timbers has grown the attention towards lesser-used timbers, which present: low durability and require protection against biodegradation. This research tested the treatability of four nondurable Myanmar hardwoods: Bombax ceiba, Bombax insigne, Spondias pinnata and Tetrameks nudiflora. Conditioned heartwood samples were pressure-treated according to standard schedules using a staining solution. Solution uptake,penetration depths, and percent of each cell type penetrated were determined and discussed according to wood anatomical characteristics. B. ceiba, B. insigne and S. pinnata had high uptakes and good penetration making them promising for protective treatment. T nudiflora was also classified as easy to treat based on its penetration index but as generally difficult to treat according to retention and depth of penetration. This different behavior was attributed to the tyloses occluding its vessels. The results are useful for the development of specific treatment schedules to achieve the retentions and penetration required for the effective protection of these lesser-used hardwoods.

  • 527.
    Sjökvist, Tinh
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Coated Norway Spruce: Influence of Wood Characteristics on Water Sorption and Coating Durability2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wood used outdoors is often degraded and discoloured by microorganisms as a natural part of its life cycle, particularly when exposed to high levels of moisture for prolonged times. In this case, the application of a coating (i.e. paint) is an option for increasing the service life of the wood.

    Norway spruce (Picea abies (L.) Karst.) is commonly used for outdoor applications in Sweden. Earlier studies have shown that uncoated spruce heartwood is less prone to moisture sorption in outdoor exposure, resulting in lower moisture content (MC) levels, as compared to sapwood. However, studies related to the above mentioned characteristics are rather limited for coated spruce, especially including the influence of outdoor exposure (i.e. weathering).

    The aim of this thesis is, therefore, to increase the knowledge of how heartwood and sapwood of different densities influence on the durability of coated Norway spruce for outdoor use. Different types of coatings with alkyd-, acrylic-, flour- (calcimine paint), or linseed-oil-based resin were included. The objectives were to study the water sorption (including MC variation) behaviour and crack formation of uncoated and coated heartwood and sapwood of different densities.

    Furthermore was an objective to study the microbial growth on the surface of similar samples of coated spruce in outdoor exposure. The used methods included wetting and liquid permeability experiments, accelerated water absorption (with samples floating freely in water), and outdoor field test. The field method lasted between three to five years and involved monitoring of the MC variation, the crack formation and the microbial growth on the samples.

    The results based on wetting measurements using octane as the adsorbed liquid showed no difference in liquid permeability between the spruce heartwood and sapwood samples of comparable densities, and indicated a similar level of pit aspiration (closure). The common flow path between two cells of conifers occurs through the pits. Still, the sapwood samples had in general a clearly higher water sorption rate than heartwood samples. It could be concluded that the increased sorption was presumably caused by a lowered water surface tension, most likely by a contamination effect of the water by surface-active sapwood extractives rather than differences in morphology of heartwood and sapwood.

    However, no clear difference in water absorption and MC levels was seen between coated heartwood and sapwood in the field study or in the accelerated water absorption study. Thus, it is suggested that a coating hinders the surfaceactive extractives to lower the water surface tension, resulting in a similar water absorption behaviour of coated heartwood and sapwood. The influence of density on water sorption of coated spruce was similarly to uncoated spruce, meaning the low-density samples had a higher MC than the high-density samples in the field tests. Furthermore, a one-year weathering of the coated and uncoated samples caused a larger increase in water sorption of high-density heartwood in the accelerated water absorption study.

    The field study on uncoated and calcimine-coated spruce showed a higher number of cracks on the high-density samples than on the low-density samples. Additionally, within each density group, a larger number of cracks were seen on sapwood samples as compared to heartwood samples. High-density samples with an alkyd- or an acrylic coating also showed a higher number of cracks. As expected, the formation of cracks on the samples increased their water sorption significantly. The microbial growth was higher on sapwood than on heartwood samples with a white coloured alkyd coating.

    The main conclusion is that heartwood and sapwood of different densities influence the water sorption and durability of coated Norway spruce. However, the principles in water sorption of uncoated heartwood and sapwood could not be applied to coated samples. Overall, the results point out that low-density heartwood could be the best material combination to improve the durability of coated spruce in outdoor use. The knowledge acquired in this thesis can enable an increased service life of coated spruce in outdoor use. The increase in service life is achieved by a careful selection of the wood material regarding the proportion of heartwood and to the choice of wood density. As a concluding remark, the role of surface-active spruce extractives needs to be explored, and a follow-up investigation in the context of water sorption is suggested for future research.

  • 528.
    Sjökvist, Tinh
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Blom, Åsa
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Influence of some wood characteristics on the variation of moisture content in outdoor exposed coated Norway spruce panels2016Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A field test of coated spruce was exposed outdoors during three years, measuring the influence of wood characteristics on the variation of moisture content in coated panels. Wood samples had following characteristics: fast-grown or slow-grown wood, heartwood or sapwood. Three different film-forming coatings were tested and all samples were exposed above ground on racks. The measured moisture contents were evaluated using the statistical method Principal Component Analysis (PCA). The moisture content of the coated samples was clearly influenced by wood characteristics; fast-grown wood had higher moisture content and higher moisture fluctuation than slow-grown wood in each respective coating system. The choice of coating system also affects the wood moisture content. The result indicates that in order to achieve low moisture content- excluding the effectiveness of coatings, wood characteristics should also be considered.

  • 529.
    Sjökvist, Tinh
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Blom, Åsa
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    The impact of heartwood and sapwood on biological discoloration of a painted surface2016Ingår i: Proceedings of the 12th meeting of the Northern European Network for Wood Science and Engineering (WSE): Wood science and engineering - a key factor on the transition to Bioeconomy. September 12-13, 2016, Riga, Latvia / [ed] Bruno Andersons, Arnis Kokorevics, Riga: Latvian State Institute of Wood Chemistry , 2016, s. 137-142Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Wood material has advantages, it comes from a renewable source and it is easy to manage. But one disadvantage when used outdoors is biological discoloration of the material. Some impact on the discoloration is the presence of moisture and nutrients, necessary components for the microorganisms to grow and start a colonisation. Samples made of Norway spruce (Picea abies (L.) Karst) heartwood or sapwood coated with two different film forming paints was studied. The paints had a binder formula made of alkyd or acrylate. Additional parameters related to study the influence of moisture content on discoloration were high and low density material, with and without impregnation oil. Outdoor exposure was made during five years in the southern part of Sweden. The samples were hung with 45 degree inclination, facing south direction. Visual differences in biological surface discoloration were observed for samples within the same paint, which could be explained by differences in heartwood and sapwood.

  • 530.
    Sjökvist, Tinh
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Blom, Åsa
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    The influence of coating color, heartwood and sapwood, on moisture content and growth of microorganisms on the surface during outdoor exposure of Norway spruce boards2019Ingår i: Journal of Coatings Technology and Research, ISSN 1547-0091, Vol. 16, nr 3, s. 819-826Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of wood contributes to the global transformation into a bio-based community. There are, however, challenges. The growth of mold, rot fungi, and algae on the coated surface is of major concern due to decreased aesthetic service life and shorter maintenance intervals. The colonization of a coated surface requires the presence of spores, nutrients, and a sufficient amount of water. This work studied the influence of using heartwood and sapwood on the moisture content (MC) and growth of microorganisms on the surface of coated Norway spruce boards [Picea abies (L.) Karst.]. The results revealed a relationship of heartwood samples having a lower MC and a lower or equal degree of biological growth on the coated surface than sapwood samples. The relationship was valid through a range of densities (309–548 kg/m3) and two different coating systems based on either an alkyd or an acrylic resin. Furthermore, the choice of coating color (red compared to white) affected the MC as the red-colored samples had a lower MC, combined with no growth of microorganisms.

  • 531.
    Sjökvist, Tinh
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Blom, Åsa
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Utomhusexponering av ytbehandlat trä: Undersökning av trämaterialets påverkan på beständigheten hos en målad granpanel2017Rapport (Övrig (populärvetenskap, debatt, mm))
  • 532.
    Sjökvist, Tinh
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Blom, Åsa
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Wålinder, Magnus
    KTH Royal Institute of Technology, Sweden.
    The influence of heartwood, sapwood and density on moisture fluctuations and crack formations of coated Norway spruce in outdoor exposure2019Ingår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 65, nr 1, s. 1-9, artikel-id 45Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The moisture sorption behaviour of wood strongly influences the durability of exterior-coated wood. Wood characteristics are known to influence the water sorption of uncoated wood. Despite this, the majority of the research on coated wood has been focused on the coating properties. This study aims to investigate the impact of heartwood, sapwood and density on the moisture content (MC) and crack formation of coated Norway spruce (Picea abies (L.) Karst.). Boards with film-forming coatings or a non-film-forming coating were exposed outdoors during 3 years. Crack development and the mass of the boards were recorded during this period. Heartwood and sapwood samples showed no differences in MC. Thus, a coating seems to reduce the differences in water sorption behaviour that is present in uncoated heartwood and sapwood spruce. The reduction is probably related to wetting properties and different sorption mechanisms, involving free and bond water diffusion. However, the low-density samples had significantly higher MC levels than the high-density samples. The high-density samples with a non-film-forming coating showed a higher number of cracks than those with lower density. Furthermore, sapwood samples had a remarkably high number of cracks when compared to the corresponding heartwood samples, despite a similar density and MC.

  • 533.
    Sjökvist, Tinh
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Niklewski, Jonas
    Lund university, Sweden.
    Blom, Åsa
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Effect of wood density and cracks on the moisture content of coated Norway spruce (Picea abies (L.) Karst.)2019Ingår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 51, nr 2, s. 160-172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A protective coating is often used on the cladding of wooden facades to limit the absorption of moisture. Low wood moisture content (MC) is essential to obtain satisfactory durability performance. Wood density is known to influence the water sorption and crack formation of uncoated wood. However, the effect of density on the aforementioned behaviors of coated spruce is not yet fully understood. Six-years of data on the crack formation and the MC variation of outdoor exposed panels are analyzed in this article. The outdoor test was complemented by a subsequent laboratory experiment, wherein the MC variation was monitored at different depths on the board during artificial water spraying. The aim of this research was to increase the knowledge about how wood density and aging affect the water sorption of coated spruce through the crack formation. The results indicated that wood density had an impact on the overall sorption behavior of coated spruce. Low-density spruce contributed to faster water absorption and desorption processes than coated samples with higher density. However, the observed correlation to density was limited to a condition with an intact coating. High-density characteristics contributed to more crack formation, and the density–sorption relationship reversed with a cracked coating. A cracked coating caused a strong local increase in the MC of the wood at the location of the cracks. Weather-exposed replicates without cracks had a higher MC in the core of the board compared with the value beneath the coating. The higher MC is probably due to the water sorption of the uncoated backside of the panel. Such an occurrence raised awareness for future studies to account for multidimensional sorption behavior from all sides of the panel. The local difference in MC also raises awareness for future studies to investigate local MC variations (as opposed to the global average of the panel) in research on the durability of coated wood.

  • 534.
    Sjökvist, Tinh
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Wålinder, Magnus E.P.
    Royal Institute of Technology, KTH.
    Blom, Åsa
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Liquid sorption characterisation of Norway spruce heartwood and sapwood using a muiticycle Wilhelmy plate metho2018Ingår i: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 9, nr 2, s. 58-65Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A multicycle Wilhelmy plate method was applied to study the water and octane sorption behaviour of small Norway spruce veneers. Dry heart- and sapwood samples of varying density were investigated. The results showed a correlation between the porosity and the sorption of octane for all samples, i.e. a higher wood porosity resulted in higher octane sorption. However, no difference in octane sorption was found between heart- and sapwood samples of similar density. The water sorption behaviour was difficult to interpret, probably due to the influence of surface-active wood extractives. It is suggested that the presence of such extractives, particularly in the sapwood samples, increases the sorption of water due to a significant decrease in its apparent surface tension. Hence, the results indicate that the liquid water sorption of spruce heart- and sapwood is strongly influenced by variations in the extractives content rather than by the micromorphology.

  • 535.
    Skagersten, Joel
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Inverkan på ekonomi och kvalitet: Vid användande av röntgenutrustning för timmersortering 2014Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Genom att mäta stockens påverkan på röntgenstrålar skapar röntgenutrustningen en bild av hur stocken ser ut på insidan. Röntgenutrustning bör kunna användas för att tidigarelägga vissa delar av sorteringen. För att avgör om detta fungerade studerades två fall.

    I det första fallet studerades virke som antingen användes till fönsterämnen eller konstruktion. För att avgöra om sorteringen fungerade jämfördes täckningsbidraget från centrumutbytet vid användning av röntgenutrustningen, som ökade med 3,7 % per sågad m3to.

    I det andra fallet skulle röntgenutrustningen användas för att sortera fram stockar med 80 % friskkvist till specialsortimentet. Då ökade andelen godkänt virke med 2,6 % vid automatisk bedömning med samma inställningar. 72 ±9 % av virket godkändes vid den manuella bedömningen.

  • 536.
    Soltani, Abolfazl
    et al.
    Shahid Rajee Teacher Training University, Iran.
    Hosseinpourpia, Reza
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Taghiyari, Hamid R.
    Shahid Rajee Teacher Training University, Iran.
    Ghaffari, Ehsan
    Shahid Rajee Teacher Training University, Iran.
    Effects of heat-treatment and nano-wollastonite impregnation on fire properties of solid wood2016Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 4, s. 8953-8967Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of nano-wollastonite (NW) suspension impregnation on the fire-retarding properties of heat-treated solid wood of three species (beech, poplar, fir) were studied. Heat treatment was performed at two temperatures of 180 °C and 200 °C. Impregnation was carried out at a pressure of 3 bars for 30 min. The fire properties included ignition time, glowing time, back-darkening, back-splitting, back-firing, and length and width of the burnt area. Both impregnation with NW and heat-treatment generally improved all fire-retarding properties, although not always to a significant level. As a mineral material, NW acted like a physical shield against fire penetration into the texture of wood specimens, thus improving fire properties. Moreover, the high thermal conductivity coefficient of wollastonite increased the thermal conductivity of wood, therefore preventing the accumulation of heat at the point nearest to a piloted flame and contributing to the improvement of fire properties. The chemical degradation of wood cell components caused by heat-treatment further improved the fire properties. Cluster analysis indicated the significant effect of species on fire properties. Significant R-square values were found amongst fire properties related to the spread of fire on the surface of specimens. The combination of thermal modification and impregnation with NW provides suitable fire properties for solid wood.

  • 537.
    Stenudd, Stefan
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Skog och trä.
    The influences of log storage and kiln drying climate on the colour of non-steamed beech (Fagus sylvatica L.) wood.2008Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 3, nr 1-2, s. 71-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Discolouration during the drying of non-steamed beech is a major industrial concern. The generally preferred yellow-white colour can easily develop a reddish or dull grey appearance during drying. In this study, the influences of log storage time and kiln drying climate on the colour of non-steamed sawn beech have been investigated and quantified. Samples 27x87 mm in cross section were dried in laboratory kilns and the average colour, in CIELAB colour space was measured on dry planed surfaces using a photoelectric colorimeter. Log storage for 13 weeks under low-temperature conditions had no visible effect. The reddish discolouration is mainly temperature related while the greyish discolouration is mainly controlled by the equilibrium moisture content (EMC) during the initial drying. Within the investigated climate interval, the EMC was twice as important as temperature for the final colour. Regression models developed show that, as long as the EMC is kept below 15%, a temperature of up to 37 degree Celsius can be allowed without any visually detectable discolouration.

  • 538.
    Svensson, Henric
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Characterization, toxicity and treatment of wood leachate generated outdoors by the wood-based industry2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Trä är ett naturligt råmaterial som knappast anses vara en risk för miljön. Däremot har hanteringen av trämaterial i industriell skala visat sig ha negativ inverkan på vattendrag. De flesta utredningar avseende vattenföroreningar inom träbaserade industrier har fokuserat på stora industrier med stor vattenförbrukning så som massa- och pappersbruk. Lakvatten som alstras vid kontakten mellan vatten och trä innehåller höga halter av organiska ämnen som är potentiellt farliga för vattendrag. Målet med denna avhandling är att få kunskap om ovanstående miljöproblem och möjlig behandlingar av dessa. Förorenat lakvatten skapas av industrier, där stora mängder timmer och sågspån är placerade utomhus och utsätts för regn och bevattning, såsom inom trägolv och bioenergisektorn. Man har funnit att lakning från olika träslag ger olika sammansättningar på lakvattnet, där lakvatten från ek har den högsta halten av föroreningar följt av furu. Denna undersökning visar att ek har potential att laka ut tio gånger så mycket polyfenoler jämfört med andra undersökta arter (tall, bok och lönn). Dessutom har lakvatten från ek den lägsta andelen av biologisk syreförbrukning efter 7dagar per kemisk syreförbrukning (0,12), vilket tyder på ett potentiellt problem med den biologiska nedbrytningen av detta lakvatten. Man har även påvisat att lakvattnet från trä är potentiellt giftigt för akvatiska organismer.

    Studier för att försöka minska miljöpåverkan av lakvatten från denna trädsort gjordes i pilotskala inom ramen för denna avhandling. Dessa studier visade bland annat på möjligheterna att använda sig av våtmarker som reningsmetod, där växter och luftning påverkar hur bra en våtmark fungerar. Men den viktigaste faktorn var den ökade uppehållstiden som vattnet får i våtmarken. Utöver studier av våtmarker har också ett filtermaterial studerats, filtret bestod av en blandning av torv och aska, som användes för att absorbera en specifik kemisk grupp i lakvattnet (polyfenoler). I en tredje typ av behandlingsprocess visade det sig också att polyfenoler effektivt kan brytas ned av ozon.

  • 539.
    Säll, Harald
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Spiral grain in trees from drought tolerant Eucalyptus species grown on dry land on the west coast of South Africa2015Ingår i: Collection of Extended abstractsfor the International Symposium: Silviculture and Management of Dryland Forests, Stellenbosch, South Africa,16-19 March 2015, Stellenbosch University , 2015, s. 87-89Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this project titled “Evaluation of drought resistant tree species to alleviate poverty in arid regions of South Africa” trees from a 20-year old field trial from two sites on the dry west coast area of South Africa were recently evaluated for growth characteristics. The three most promising Eucalyptus species, namely E. gomphocephala, E. cladocalyx and E. grandis × camaldulensis hybrid, for growth characteristics were selected for further evaluation. The objective of the study reported was to investigate between species variability of selected physical and processing properties determining the suitability of these three species for lumber production. It will also be useful for informing tree breeders and silviculturists to identify which properties need improvement through breeding selection or forest management strategies. And in the future results can hopefully be used for selection of species for small farm plantations which may be processed and sold to generate income.

    One of most common reasons for a customer to avoid using wood is the lack of shape stability. There is a clear connection between spiral growth and how twisted the sawn timber will be when it is dried. Depending on the log diameter a grain angle over 3 to 5 degrees will produce sawn wood that will be pronounced to twist. In older softwood trees, the cracks lean mostly to the right. This means that the grain angle is right handed, and the visible cracks create a spiral in an anti-clockwise direction, looking from the base to the top of the tree (Figure 1). In spruce trees, however, the grain angle close to the pith is left-handed, which means that the fibres follow a clockwise spiral up the trunk (Harris 1989).

  • 540. Säll, Harald
    et al.
    Pettersson, Bengt-Elis
    Masurbjörk2008Bok (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    Detta häfte är en introduktion till dig som är intresserad av att ekonomiskt utveckla ditt skogsbruk genom odling och användning av masurbjörk, Skandinaviens värdefullaste trädslag. Vi vill här kort ge dig grundfakta så att du kan förstå den ekonomiska möjlighet som odling av klonade masurbjörk för med sig, också i ditt skogsbruk. 

  • 541.
    Taalas, Saara L.
    et al.
    Linnéuniversitetet, Fakultetsnämnden för ekonomi och design, Ekonomihögskolan, ELNU.
    Sandberg, Dick
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Bridging life at home and sustainable production.2011Ingår i: Rediscovering Wood: The Key to a Sustainable Future, 2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Dr Saara Taalas and Dr Dick Sandberg presented the relevance of looking in more detail the consumption patterns that will influence relationships with material culture. The consumption patterns change over time suiting to everyday life of that time at a locality. For instance, in Nordic countries, the same forests that served livelihood of people in the past are now important centres for recreation- a change of dimension from livelihood to sports. Thus, the relations with forests have dramatically changed. Many people are now secondary stakeholders (using its products) than directly depending on it for livelihood as people did 100 years ago. The same happened to the relation with the material originating from the forests. For instance, in Sweden firewood dominated harvest from forests (40%) in 1900, but is less than 8 % now. On the contrary, pulpwood that was just 5 % of the harvest in 1900 constitutes now 44 %. Only sawmilling remained relatively the same. Visions for Finnish bio economy business levels reflect the increasing relevance of living trees and bio-energy in future. The wood products will be there but the requirements will change- from volume to specific requirements on properties (e.g. shape stability). The tactile of part of wood see more money but the traditional paper and pulp products are likely to lose its relevance in Northern Europe because of high prices, changing markets and long rotation of forest trees.

    Thus, the pulp mills diversify with new products (e.g. textiles). Innovation in new processes will drive ways for new wood use in future (e.g. polymers and chemicals, bioenergy etc). Prioritising purpose will determine wood’s value. For example, using wood for bioenergy (which gains relevance in Northern Europe) might negatively influence many other business levels. Increasing business value should be given emphasis as trees could be sold 100 times through process innovations.

  • 542.
    Taghiyari, Hamid Reza
    et al.
    Shahid Rajaee Teacher Training University, Iran.
    Elyasi, Abdollah
    University of Tehran, Iran.
    Doost-Hoseini, Kazem
    University of Tehran, Iran.
    Hosseinpourpia, Reza
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Georg August University Gottingen, Germany.
    Correlation between gas and liquid permeability with noise reduction coefficient in insulation boards made from sugar cane bagasse2017Ingår i: Bulgarian Journal of Agricultural Science, ISSN 1310-0351, Vol. 23, nr 3, s. 674-681Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Specific gas and liquid permeability, as well as noise reduction coefficients, in insulating boards made of sugar-cane bagasse were studied here. Urea-formaldehyde (UF) and melamine-urea-formaldehyde (MUF) were used to produce homogeneous as well as three-layered insulating boards with three densities of 0.3, 0.4, and 0.5 g/cm3. The obtained results indicated that MUF slightly decreased gas and liquid permeability, but it did not significantly affect the noise reduction coefficients. Gas and liquid permeability were considerably affected by the density of the boards, due to the compression between the bagasse particles and less spaces and voids to let the fluids to pass through. However, noise reduction coefficients were significantly affected both by the density, as well as the board-type. More compression between the particles and the consequent less space between the bagasse particles entangled the waves; further more, the sudden change between the layers in the three-layered boards formed a barrier towards transmission of waves.

  • 543.
    Taghiyari, Hamid Reza
    et al.
    Shahid Rajaee University, Iran.
    Hosseinpourpia, Reza
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Jahangiri, Asghar
    Rabie, Davood
    Effects of Nano-Wollastonite Impregnation on Fire Properties of Some Thermally-Treated Solid Wood Species2017Ingår i: Proceedings IRG Annual Meeting, IRG/WP 17-40771, International research group on wood protection , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    The effects of nano-wollastonite (NW) suspension impregnation on the fire-retarding properties of heat-treated solid wood of three species (beech, poplar, fir) were studied. Heat treatment was performed at two temperatures of 180 °C and 200 °C. Impregnation was carried out at a pressure of 3 bars for 30 min. The fire properties included ignition time, glowing time, back-darkening, back-splitting, back-firing, and length and width of the burnt area. Both impregnation with NW and heat-treatment generally improved all fire-retarding properties, although not always to a significant level. As a mineral material, NW acted like a physical shield against fire penetration into the texture of wood specimens, thus improving fire properties. Moreover, the high thermal conductivity coefficient of wollastonite increased the thermal conductivity of wood, therefore preventing the accumulation of heat at the point nearest to a piloted flame and contributing to the improvement of fire properties. The chemical degradation of wood cell components caused by heat-treatment further improved the fire properties. Cluster analysis indicated the significant effect of species on fire properties. Significant R-square values were found amongst fire properties related to the spread of fire on the surface of specimens. The combination of thermal modification and impregnation with NW provides suitable fire properties for solid wood.

  • 544.
    Thörn, Andreas
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Umeland, Christian
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Björkämnesförsörjning i ett möbelproducerande företag2009Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Detta examensarbete handlar om hur ett möbelproducerande företags råmaterialförsörjning går till. Företaget som har varit värd för arbetet är ett möbeltillverkande företag som heter Stolab och ligger i Smålandstenar. Studiebesök och intervjuer har hos Stolab och deras leverantörer legat till grund för det arbete som vi har utfört. Ämnen som är behandlade är kvalitetsaspekter på råmaterialet samt hur relationerna mellan kund – leverantör fungerar. Arbetet fokuserar främst på den sista punkten, hur relationerna ser ut mellan kund leverantör, vilka möjligheter man har att förbättra kommunikationen mellan företagen och hur inköp och lagerhållning kan fungera. För att kunna förbättra kvaliteten på det råmaterial som kommer till företaget så är en viktig del i det att öka förståelsen för de krav som ställs. Kraven måste också kommuniceras på ett effektivt sätt. Vi har utarbetat en modell för hur detta samarbete kan gå till samt gett en del andra förslag till åtgärder för att kunna förbättra kvalitet på materialet och förbättra relationerna.

  • 545.
    Thörnqvist, Thomas
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Hantering av stormfällt virke: en litteratursammanställning2005Rapport (Övrigt vetenskapligt)
  • 546.
    Thörnqvist, Thomas
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Input Wood Processing Strategy from Sweden2008Ingår i: A European Wood Processing Strategy: Country Reports. / [ed] Joris Van Acker, Ghent: DCL Print & Sign , 2008, s. 307-319Konferensbidrag (Refereegranskat)
  • 547.
    Thörnqvist, Thomas
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Stora värden till spillo: Tema: Efter stormen2005Rapport (Övrig (populärvetenskap, debatt, mm))
  • 548.
    Thörnqvist, Thomas
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    The chain related to wooden products from the forset to the end-user.2007Ingår i: Cost Action E44 - Wood Processing Strategy / [ed] Arto Uusenius, Belgum: Gent University , 2007Konferensbidrag (Refereegranskat)
  • 549.
    Thörnqvist, Thomas
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Vem står för skogsägarnas rotnetto?2007Rapport (Övrigt vetenskapligt)
  • 550.
    Thörnqvist, Thomas
    et al.
    Sveriges lantbruksuniversitet, Inst för virkeslära.
    Nylinder, Mats
    Lagring av grenar och toppar i olika fraktioner: Studie utförd vid Åtvidabergs Trävaru AB1980Rapport (Övrigt vetenskapligt)
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