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  • 1.
    Ah Shenga, Pedro António
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Simulated Breakdown of Two Tropical Hardwood Species2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 450-456Article in journal (Refereed)
    Abstract [en]

    A simulation study has been performed on a small log database of tropical hardwoods consisting of 10 Jambirre (Millettia stuhlmannii Taub.) and 5 Umbila (Pterocarpus angolensis D.C.) logs. The outer log shape was acquired by a 3D laser scanner before sawing and the heartwood content was estimated by measurement on images of the centre slabs after through-and-through sawing. Yield and value recovery using different sawing techniques and different sawing patterns, together with rotational and skew positioning errors, are presented. The results show that through-and-through sawing in the best rotation and skew positions tested improves the yield of Umbila logs by an average of 4.5 percentage points and Jambirre logs by 3.6 percentage points compared to cant sawing. It can be concluded that positioning and sawing patterns have a great influence on the yield and value recovery of these species and that log grade and species have an impact on the sawing pattern that should be used.

  • 2.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Equalization of moisture in pre-dried pinewood using microwave power2010In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 6, no 2, p. 53-59Article in journal (Refereed)
    Abstract [en]

    Commonly, during air-circulation kiln drying moisture gradients within wood cross-sections are developed, i.e. the surfaces become drier than the interior. To minimize these gradients a conditioning step subsequent to the drying is needed. The aim with this study was to investigate the possibility to use microwave power for equalization of moisture within pinewood boards after air-circulation kiln drying to the average moisture content 0,14. Two dimensions of pinewood were tested; thickness 50 and 63 mm, in two different plants, generating 5 and 12 kW microwave power respectively. Results show that microwave energy give rise to a fast and advantageous moisture equalization within the wood. The higher microwave power density the faster heating and moisture redistribution in these wood dimensions. Required time for heating and redistribution of moisture was found to be as short as 3 minutes at the power density 500 kW/m3. In addition, split-tests indicate decreased or elimination of gap after microwave treatment in the investigated specimens.

  • 3.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Basic knowledge of wood properties for improved performance of laminated Veneer products2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 549-556Article in journal (Refereed)
    Abstract [en]

    To ensure success in the production of laminated veneer products, it is necessary to acquire a sound basic understanding of the behaviour of the wood, and to understand the inherent reactions of wood to adhesive, heat, moisture, strain and stress. This can ensure an efficient wood utilization and promote the development of new processes and products that take advantage of the visco-elastic nature of wood. A shortcoming of the laminated bending process is that the products may become distorted after moulding and during use. In this study, we have examined how the performance of laminated veneer products can be improved through the implementation of basic knowledge of wood in the design and production process. The results show that the material and process parameters and storage in a changing relative humidity have a clear impact on distortion. Fibre orientation of the veneers in the moulded assembly was the most critical parameter to control. Fibre deviations mainly resulted in twist of the product. A moisture content in one veneer deviating from that of the rest of the veneers in the assembly before moulding resulted in distortion of the laminated veneer products both after moulding and during use. To decrease the negative effect of fibre orientation and moisture content on shape stability, the veneer should be straight-grained and well-conditioned to a moisture level adapted to the use of the final product. Special care should also be taken to orientate the veneers during assembly before moulding.

  • 4.
    Blomqvist, Lars
    et al.
    Linneaus University.
    Sterley, Magdalena
    SP Technical Research Institute of Sweden, SP Wood Technology, Skellefteå.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Johansson, Jimmy
    Department of Forestry and Wood Technology, Linnæus University.
    The effect of veneer-modifcation on the bond-strength in laminated veneer products2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 43-49Article in journal (Refereed)
    Abstract [en]

    A major problem in the manufacture of three-dimensional laminated veneer products (LVP) is damage due to stretching and/or buckling of the veneer. To reduce or eliminate this problem, veneer densification or adding a strengthening layer to the veneer can be an alternative. To study how veneer modification influences the veneer-to-adhesive bond strength, three methods of modification were studied in relation to an unmodified reference veneer: (1) densified veneer, (2) veneer pre-bonded with paper and hot melt adhesive (HMA), (3) veneer pre-bonded with non-woven polypropylene (NW) fabric glued to the veneer (a) with a urea formaldehyde (UF) adhesive, (b) with a mixture of UF and polyvinyl acetate (PVAc) adhesive, and (c) with a PVAc adhesive. Densification, pre-bonding with paper, and NW with UF/PVAc adhesive mixture resulted in no or only a slight decrease in strength of the bond-line compared to the reference. NW glued with UF or PVAc adhesive showed a considerable reduction in the strength of the bond-line. The climatic cycling had no significant influence on the bond strength.

  • 5.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Implementation of Computer Aided Tool for Non-Destructive X-Ray Measurement of Moisture Content Distribution in Wood2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 330-336Article in journal (Refereed)
    Abstract [en]

    This paper reports recent attempts for implementing non-destructive measuring of moisture contentin wood based on computed tomography technology. The study focus onan image analysis method that has been already proposed and validated in the literature, but ithas not been tested for measuring low moisture content variations below fibre saturation point.The computed tomography method was tested against the oven-dry method.The results show thatit is possible to apply this technology to measure low levels of moisture content based on a regression model, where therootmean square error of the modelwas 1,4percentage points of moisture content. The method can still be improved because the density differences between samples are relatively small in relation to the experimental error and the computed tomography precision.

  • 6.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Norwegian University of Science and Technology (NTNU), Department of ICT and Natural Sciences, Norway.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    CT scanning of capillary phenomena in bio-based materials2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 181-187Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) is a powerful tool for the non-destructive study of dynamic moisture processes in wood and other bio-based materials. In the CT facilities at Luleå University of Technology, it is possible to study wood-moisture relations such as water absorption, drying and related material deformation under a temperature- and humidity-controlled environment.An increase in the use of bio-based materials in building construction has led to an increased interest in capillary phenomena in these materials, because of an increasing number of moisture-related damage in timber and hybrid-timber buildings. This article shows some examples of how different bio-materials used in construction interact with liquid water over time. The overall purpose has been to develop the CT technique as a powerful tool for the determination and visualization of capillary flow that can be a base for modelling and an increased understanding of moisture flow in new bio-based building materials.Early-stage observation of the behaviour of different traditional and new bio-based building materials shows that CT scanning, combined with image processing, has a high potential to be used in performing non-destructive and non-contact tests that can help to increase the knowledge of water-material interactions and develop building materials with an optimized performance.

  • 7.
    Cristescu, Carmen
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Neyses, Benedikt
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Söderström, Ove
    Kungliga tekniska högskolan, KTH, KTH Byggnadsmateriallära.
    Modeling of the temperature distribution in self-bonded beech-veneer boards during hot pressing2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 97-103Article in journal (Refereed)
    Abstract [en]

    Auto-adhesion is a phenomenon that is in general related to the manufacture of wood-basedfibreboards, e.g. to the Masonite process or similar processes based on lignocellulosic raw materials.Auto-adhesion as a mechanism for the bonding of solid wood or veneer has not met with the sameindustrial success, but interest is increasing for environmental reasons and as a result of theincreasing cost of adhesives in wood products. The temperature in the laminate is crucial for the autoadhesionprocess that will result in bonding between veneers during hot-pressing. This paper presentsa model for the temperature evolution during the hot-pressing of a porous material, which wasdeveloped and verified for a five-veneer beech laminate pressed at a temperature of 250°C and apressure of 6MPa in an open system for 280 seconds. The result shows good agreement between themodel and the experimental temperature data during the hot-pressing. It can be concluded that a goodcontrol of the temperature evolution during the manufacture of adhesive-free veneer boards is of majorimportance to reach the target properties of the product.

  • 8.
    Cristescu, Carmen
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Could colour predict hardness of hot-ptressed self-laminated beech boards2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 150-156Article in journal (Refereed)
    Abstract [en]

    Laminated self-bonded densified boards were obtained by pressing five veneers of beech(Fagus sylvatica L.) parallel-grain-oriented, without adhesive and without surface activation. Theboards were pressed according to an experimental design based on fifteen different combinations ofpressing parameters: temperature (200, 225, and 250°C), pressure (4, 5, and 6MPa), and time (240,300, and 360s). The image of the 40 board edges (radial sections) was analysed with ImageJ softwarein the red-green-blue (RGB) colour space. Brinell hardness tests were also performed. The resultsshow an almost linear relation between the brightness values (defined as the arithmetic mean of theRGB channels) and the Brinell hardness. It is suggested that brightness is a predictor of strength forself-bonded laminated boards.

  • 9.
    Ekevad, Mats
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Finite Element Simulation of Nailed Glulam Timber Joints2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 318-323Article in journal (Refereed)
    Abstract [en]

    hispaper presents a finite element modeling method for a certain type of nailed jointbetween glulam beams. The joint in question is a traditional arrangement of a horizontal beam anda vertical pillar but herethere is also a nailed steel plate inserted on the two sides in order to strengthen the joint.Experimental results and a comparisonsof simulated and experimental results aremade. The model includes the elastic and plastic orthotropic behaviour of wood and the elastic and plastic behaviour of nails.The nail joint between the steel plate and the wood is modelled as an elastic-plastic surface to surface connection with elastic-plastic properties. Also the reinforcing effect of nails in the nail-affectedvolume of wood is taken into consideration by raising rolling shear yield limitin the affected wood volume.The comparisons showthat the model works well and give results that are comparable to experimental results.

  • 10.
    Eliasson, Lars
    et al.
    Linneaus University.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Some aspects on the more efficient use of wood in the industrial manufacture of single-fammily timber houses2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 418-425Article in journal (Refereed)
  • 11.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Factors Affecting Volume Yield in a Forestry-Wood Value Chain: A Simulation Study Based on CT Scanning2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 540-548Article in journal (Refereed)
    Abstract [en]

    The paper presents the results of a simulation study, where log models based on CT scanned logs of Scots pine (Pinus sylvestris L.) was used as input material to a computer simulation model of a generic value chain involving sawing, drying, crosscutting and finger jointing. The aim was to investigate which factors that affect the volume yield in the value chain, be it forestal, log-, process- or quality-related factors. The results show that factors related to growth conditions and log size have a large impact on the volume yield in the studied value chain, together with quality requirements on knots. Factors such as sawing positioning and log quality had a much smaller impact. It can be concluded that it is possible to model a forestry-wood value chain, while assessing which input variables affect the result in terms of volume yield, using CT scanning of logs and subsequent computer simulation of the production processes.

  • 12.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The Use of CT-Scanning Technology in Wood Value-Chain Research and in Wood Industry: A State of The Art2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 533-539Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) is a powerful tool for the non-destructive  measurement  of  dynamic  processes in wood. After more than 25 years of research at Luleå University of Technology in the field of CT-scanning of wood material, the first industrial CT-scanners are now installed in sawmill production for the in-situ measurement of internal  log features to steer of the sawmill process with the help of this information.This  paper  provides  an  overview  of  the  potential  of  CT-scanning in wood-material  research  and  how  this data can be used for the modelling and simulation of the wood value chain. A database of CT-images of trees  is  used  to  create  a  log  model  including  the  outer  shape  of  the  logs  and  their  internal  knot  structure.  Simulation software is used to saw these virtual logs in different positions relative to the sawblade, and also for the crosscutting of the sawn timber to components. The output is dimensions and grades of sawn timber, volume yield as well as an economic result based on real economic conditions. A specially designed climate chamber  for  CT  studies  of  the  drying  of  sawn  timber  is  used  to  increase  the  knowledge  of  how  the  drying  affects the response from the sawn timber during seasoning.

  • 13.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cherepanova, Ekaterina
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    CT-scanning during heat treatment of wood2011In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 7, no 4, p. 11-17Article in journal (Refereed)
    Abstract [en]

    Earlier experiences from industrial heat treatment of wood with the ThermoWood® process show that more or less extensive internal cracking may occur for thicker dimensions. This type of timber damage is particularly troublesome because these cracks do not reach the surface and are thus not visible on unprocessed timber. After resawing or planing the boards, cracks can appear, resulting in costly downgrading of the material. The ThermoWood® heat treatment process can be divided into six periods. The first period, the heating period, is when saturated steam is injected into the kiln, the second period is the drying step, which can be either high or low temperature drying, the third period is when the final heating and drying take place, the fourth period is when the temperature is kept constant for about 2–4 hours, the fifth period is the cooling regime, the sixth period is the conditioning regime for remoistening the material, and the last period is the cooling one. At the Division of Wood Physics at Luleå University of Technology in Skellefteå a climate chamber has recently been installed. This climate chamber together with a CTscanner makes it possible to study wood density changes in different climates. As the maximum temperature that can be reached in the climate chamber is 220 °C, it is also possible to study the heat treatment process, besides conventional air circulation drying. The aim of this study was to use the CT-scanning (CT) technique during heat treatment of wood in order to investigate whether it is possible to detect internal checking in situ during the treatment.

  • 14.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fjellner, Bengt-Arne
    Luleå University of Technology, Professional Support, VSS Support.
    Wood shrinkage coefficient and dry weight moisture content estimations from CT-images2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 557-561Article in journal (Refereed)
  • 15.
    Hemmilä, Venla
    et al.
    Linnéuniversitetet.
    Trischler, Johann
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bio-based adhesives for the wood industry: an opportunity for the future?2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 118-125Article in journal (Refereed)
    Abstract [en]

    This paper reviews the use of some of the new technologies that may be implemented in bio-based adhesives, e.g. carbohydrate polymers, proteins, tannins, lignins, and vegetable oils. In order to take a part of the market share, an adhesive should have low production costs, fulfil the environmental and health standards and give better properties than conventional synthetic adhesives. For large-volume wood products such as chipboard, it is essential to develop adhesives that enable the product to be cost competitive. Bio-based adhesives that are available and affordable for the wood industry suffer from three main problems: low moisture resistance, low reactivity and poor adhesive properties, and in several cases they are expensive compared to synthetic adhesives.

  • 16.
    Johansson, Jimmy
    et al.
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Integrated use of product data for improved wood material utilization in furniture and joinery production2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 321-327Article in journal (Refereed)
    Abstract [en]

    Quality communication from customer to supplier is crucial for the effectiveness of a value chain. In the forest products industry, a mutual understanding of quality requirements between customer and supplier in relation to material characteristics and production conditions is important if the material is to be utilized effectively. In the mechanical wood industry, hardwood has normally been quality graded manually. This has been a work-intensive operation and a problematic working environment. Automatic grading equipment based mainly on camera and laser technology is therefore gradually replacing the manual grading operation which relies on the human eye. The cross-cutting of sawn wood into shorter components with well-defined quality parameters is a process which needs to be automated. This makes it possible for the sawmill to redefine the quality grading process with e.g. more complex grading rules. To gain full benefits from the new technology, however, the grading process must be redefined in cooperation with the customers. There is also an expressed need for tools to communicate the quality of products produced by sawmills.In this study, three case studies were therefore performed where the communication of requirements between sawmills and customers was studied with regard to three different components delivered from two sawmills. In one sawmill, two products were studied; one intended for a furniture producer and one for a joinery producer. In the other sawmill, the studied product was intended for a producer of solid wood panels. The idea has been to study the need for product information expressed by both the customer and supplier through the automatic grading process and to utilise this equipment for data collection and visualisation. The requirements for a communication and data exchange tool have been derived. There is often an expressed need to measure how different raw materials affect the volume yield in a process and how different quality requirements affect the volume yield. Sharing this information between customer and supplier has been shown to yield a mutual understanding of how and why deviations occur. Visualisation possibilities are a prerequisite for a mutual understanding of quality conceptions.

  • 17.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cristescu, Carmen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Autoadhesion of laminated boards from Scots pine veneers: effect of oxidative pretreatment2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 110-115Article in journal (Refereed)
    Abstract [en]

    This paper presents results from studies on the pre-treatment of veneers from Scots pineusing hydrogen peroxide and a ferrous catalyst followed by pressing at 220, 230, and 240°C. Thetreatment gave boards that did not delaminate when exposed to water followed by drying of roomtemperature, whereas boards without a pre-treatment delaminated. The press-plate temperature didnot influence the extent of delamination, but the thickness swelling was lower at higher presstemperature. Analysis of extracts from the oxidative pre-treated and hot-pressed surface materialusing UV-spectroscopy was compared with analysis of bondlines from water-stable laminated boardsfrom beech.

  • 18.
    Neyses, Benedikt
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Development of a new wood-based modular furniture system: evaluation of suitable materials for connectors2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 595-602Article in journal (Refereed)
    Abstract [en]

    Concepts for modular furniture systems are of growing interest from the perspective of bothproducers and customers, and they are now entering the area of mass customization. Modularity andstandard interfaces eliminate the interdependency of the components of a product, and allow themanufacturer and customer to change components without affecting the product architecture. In thiscontext, the connectors between components of the modular furniture systems are essential for thesystems. The objective of this study was to evaluate the suitability of different wood-based materialsfor the connectors of the modular furniture system, the focus being on the strength properties.13different types of wood-based material were tested in three-point bending tests, and the modulus ofelasticity (MOE) and the modulus of rupture (MOR) were determined. The tested materialsincorporated wood modifications such as compression, heat treatment and impregnation, as well asdifferent types of adhesives. It could be concluded that birch plywood bonded with soybean glue, andsolid cumaru wood are the most suitable types of wood-based material for the modular furnituresystem. Compressed plywood generally exhibited better strength properties than ordinary plywood,and the type of adhesive had no significant influence on either MOE or MOR. Self-bonding plywoodhad a high MOE, but a comparably low MOR. Solid cumaru wood exhibited both a high MOE and ahigh MOR. Materials which had reasonable strength properties and a comparably low environmentalimpact were considered suitable for the connectors of the modular furniture system, which meant thatnon-formaldehyde-emitting adhesives were favoured.

  • 19.
    Popovic, Djordje
    et al.
    Jönköping University, School of Engineering.
    Meinlschmidt, Peter
    Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI.
    Plinke, Burkhard
    Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI.
    Dobic, Jovan
    Tarkett Eastern Europe, BU WOOD.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Crack Detection and Classification of Oak Lamellas Using On-Line and Ultrasound Excited Thermography2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 464-470Article in journal (Refereed)
    Abstract [en]

    On-line thermography and ultrasound-excited thermography have been evaluated for the detection of cracks in oak lamellae of flooring top layers. Image acquisition accompanied the tests and the objects were identified by post-processing and the evaluation of lamella images. The results were validated by comparing these findings with the actual state of the lamellae in terms of cracks and the classification accuracy of the method was calculated. The classification accuracy of the ultrasound-excited thermography method was three times greater than that of on-line thermography. The main conclusion is that the ultrasound-excited thermography method is the more suitable for the detection of cracks and the classification of lamellae.

  • 20.
    Rademacher, Peter
    et al.
    University of West Hungary, Hungary.
    Bader, Matyas
    University of West Hungary, Hungary.
    Nemeth, Robert
    University of West Hungary, Hungary.
    Rousek, Radim
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Paril, Petr
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Baar, Jan
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Hornicek, Stanislav
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Dejmal, Ales
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Dömeny, Jakub
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Kúdela, Jozef
    Technical University in Zvolen, Department of Wood Science, Slovakia.
    Kutnar, Andreja
    University of Primorska, Slovenia.
    Neyses, Benedikt
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    European co-operation in wood research From native wood to engineered materials: Part 2: densification modification in product development2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 351-360Article in journal (Refereed)
    Abstract [en]

    Wood  is  a  renewable,  biological  material  used  in  numerous  applications  and  it  is  growing  in  importance  due  to  sustainable  development  efforts.  Wood  also  suffers  from  a  number  of  disadvantages,  were low hardness and abrasive resistance are characteristic for low-density species.  This paper presents state of the art on different wood densification processes as one emerging process technology for increased use  of  low-density  species.  The  presentation  is  based  on  work  by  different  European  research  groups  in  wood  science,  collaborating  in  the  field  mainly  through  different  COST  Actions.  The  main  principles  for  processes are discussed, such as bulk and surface densification, as well as methods for reducing the shape memory  effect  of  densified  wood.  The  main  challenges  for  the  future  are  in  the  field  of  finding  fast  and  environmental  friendly  method  for  elimination  of  the  set-recovery  and  scaling  up  to  profitable  industrial  applications.  To  provide  a  better  understanding  with  this  regard,  some  relevant  applications  of  densified  wood are presented.

  • 21.
    Rademacher, Peter
    et al.
    University of West Hungary, Hungary.
    Báder, Mátyás
    University of West Hungary, Hungary.
    Németh, Róbert
    University of West Hungary, Hungary.
    Klímek, Petr
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Šprdlik, Václav
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Rousek, Radim
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Čermak, Petr
    Mendel University in Brno, Department of Wood Science, Czech Republic.
    Pfriem, Alexander
    Eberswalde University for Sustainable Development, Faculty of Wood Science and Technology, Germany.
    Sanne, Moritz
    Eberswalde University for Sustainable Development, Faculty of Wood Science and Technology, Germany.
    Meinlschmidt, Peter
    Fraunhofer - Institut für Holzforschung - Wilhelm-Klauditz-Institut (WKI), Germany .
    Wimmer, Rupert
    University of Natural Resources and Life Sciences, Institute of Natural Materials Technology, Austria .
    Trischler, Johann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    European co-operation in wood research From native wood to engineered materials: Part 3: engineered hybrid wood-based products2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 361-372Article in journal (Refereed)
    Abstract [en]

    Forest-based  industries  have  been  continuously  developing  advanced  processes,  materials  and  wood-based solutions, to meet evolving demands and increase competitiveness. Engineered wood products (EWPs)  constitute  one  emerging  group  of  materials  aiming  at  improved  property  profiles  of  wood,  and  provide desired shapes and functionality. In this paper, the main principles for different processes to soften wood  and  make  it  more  flexible  for  bending  and  moulding,  such  as  longitudinal  compression,  plasticization  by  water  vapour  and  gaseous  ammonia,  and  a  dielectric  heating  technique,  are  discussed.  Examples  of  implementation  of  these  techniques  for  the  production  of  wooden  products  are  presented,  and  the  use  of  reed  canary  grass,  and  a  novel  technique  for  embossment  of  hybrid  particleboards  are  also  further  discussed.

  • 22. Rebstock, Florian
    et al.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Makerjoint, a new concept for joining members in timber engineering: Strength test and failure analyses2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 397-404Article in journal (Refereed)
    Abstract [en]

    The wood construction industries are becoming more focused on climate change and resourcedepletion, and individual and industrial consumption must reflect a greater degree of concern for theclimate and environmental wellbeing. This paper presents a new concept for timber engineering, thepurpose being to acquire information about the failure modes and the tensile and compressivestrengths of two types of joint, the Simple Gooseneck and Thick Gooseneck, that can be used in anew concept for joining members in timber structures. This Makerjoint concept uses laminated veneerlumber (LVL) as nodes in regions with a pronounced non-uniform stress distribution and sawn timberin regions with a more uniform stress distribution. No metal fasteners or adhesives are used in thejoint between timber and LVL. The concept is intended for joints using 3-axis CNC machinery and tobe a system for on-site- and pre-fabrication of e.g. small houses, emergency shelters and exhibitionstands. The joints have a higher compressive than tensile strength. The joints exhibited brittle failure intension (beam and/or node failure) and buckling occurred in compression around the thinnest crosssection of the beams. Suggestions are made for how the mechanical properties of the joints can beimproved.

  • 23.
    Trischler, Johann
    et al.
    Linnéuniversitetet.
    Nilsson, Jonaz
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Reed canary grass as light-weight core in particle boards2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 469-476Article in journal (Refereed)
    Abstract [en]

    Particle boards are an important material for furniture production. In this sector, two tasks have had priority during recent years: to reduce the weight of the panels and to reduce the formaldehyde emission. As the production methods have been more or less the same for decades, these tasks have to be tackled by reducing or replacing the raw material in the board production.In this study, the possibility of replacing wood with reed canary grass (Phalaris arundinacea L.) to obtain a light-weight particle board has been studied. The boards studied were three-layered with a core of wood/reed canary grass particles and a surface of 100 % wood particles. A protein-based adhesive was tested as an alternative to a UMF adhesive to reduce the formaldehyde emission. Different combinations of densities between 250 and 450 kg/m3 were included in the study and no additional treatments were made to the raw materials.The results showed poor mechanical and swelling properties of all the tested boards regardless of the design. The main explanation of the poor properties is the poor wetting of the reed canary grass surface by the adhesives. A pre-treatment of the reed canary grass particles with steam, lipase enzyme or alkali is suggested to increase the wettability.

  • 24.
    Trischler, Johann
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Competitive strategies to wood production in Europe: A conceptional study2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 586-593Article in journal (Refereed)
    Abstract [en]

    Wood  is  a  raw  material  with  multifaceted  properties  making  it  useful  for  a  diversity  of  industrial  products. However, its primary production is restricted by environmental conditions and alternative land use. Forestry,  as  the  main  supplier  of  wood  as  raw  material,  is  assumed  to  act  strategically  with  regard  to  the market  situation  and  to  try,  therefore,  to  provide  the  most  beneficial  mix  of  different  assortments  of  wood.  Changes  in  the  supply  of  different  assortments  and  their  current  value  on  the  market  are  assumed  to  be  closely  related.  Fluctuations  in  stock  and  market  value  affect  the  wood-using  industry  depending  on  the  different assortments as raw material. The purpose of this study was to apply a concept of competitive strategies for market-driven goods to  forest  management  in  Europe,  in  order  to  derive  information  about  the  operational  possibilities  of  forest  management  in  specific  market  situations.  For  this  purpose,  Steinmann’s  and  Schreyögg’s  concept  of  competitive  strategies  for  market-driven  goods  was  applied  to  forest  management,  in  order  to  defining different  competitive  strategies  for  the  production  of  different  assortments  of  wood.  The  results  show  that  different market strategies can be applied to forest management and that, even though the overall production is limited, forestry has quite a high flexibility regarding the competitive strategy used. The results also show possible impacts on the nature of forests due to changes in forest management.

  • 25.
    Trischler, Johann
    et al.
    Linnéuniversitetet, Linnaeus University, Växjö.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wheat protein as adhesive for wood products for interior use2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 246-252Article in journal (Refereed)
    Abstract [en]

    Protein is one of the most researched and widely used natural adhesives. Before the breakthrough of synthetic adhesives in the wood industry, proteins were commonly used in furnitureproduction. Today, proteins in the form of industrial by-products e.g. soy protein, blood and wheatprotein are on the market, and these proteins can in general be used as a base for wood-productsadhesives. Proteins are in general denatured by a change in pH, heat or organic solvents before theycan be used as adhesives. In this study, a cold-dissolution of wheat protein (gluten) was tested withregard to its usability for the production of particleboards and laminated veneer products. The bondingwas evaluated by testing the internal bond strength, thickness swelling, tensile strength and tensileshear strength. The results showed that the strength of the bond-line was in some cases as high asthe strength of the wood material, but also that there were in some cases problems with thepenetration of the adhesive into the wood and this lowered the bond-line strength considerably. Themain conclusion is that cold-dissolved gluten adhesives are a good alternative to commercial syntheticadhesives for interior use, but that there are still challenges with the poor moisture resistance of theadhesive.

  • 26.
    Trischler, Johann
    et al.
    Department of Forestry and Wood Technology, Linnæus University.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Noszkowski, Calle
    Linnæus University, Department of Design.
    The use of gluten adhesive and removable surface finishes in recyclable furniture panels2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 613-618Article in journal (Refereed)
    Abstract [en]

    A general problem in the recycling of furniture is that different materials and components areincluded within a single piece of furniture. Not only is the furniture built of components such as wood,leather, textiles, foams, steel and others but the wood component is also very often a composite madeof wood, adhesives and functional additives such as water repellents or chemical substances assurface treatments. Sometimes these additives make cost-effective recycling of the composite wooddifficult because of problems related to the separation of the components. The purpose of this studywas to present an alternative product design for wood-based panels i.e. particleboards, which reducesor avoids many of the problems in the recycling of wood-based panels used in furniture. The resultsshow that it is possible to produce wood-based panels in a way that facilitates the recycling of thesepanels although there are still some challenges which have to be dealt with. The concept as suchseems to be promising.

  • 27.
    Vikberg, Tommy
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Mornén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Internal Heat Exchange in Progressive Kilns2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 318-323Article in journal (Refereed)
    Abstract [en]

    In this work possible energy savings were investigated by introducing a new layout of a 2-zone progressive kiln. The layout consisted of installing a door between the first and second zone, thereby allowing the two zones to be run at different temperature levels -making internal heat recovery possible. An Optimized Two Stage continuous kiln is dimensioned for drying sideboard of Norway spruce (Picea abies L. Karst) with the aid of a commercial simulation program. Temperature levels of 75/55°C (dry bulb/wet bulb) were chosen at the pressure side of zone 1 and 45/25°C (dry bulb/wet bulb) at the pressure side of zone 2. The capacity of the heat exchanger was assumed to be sufficient to make the suggested design functional and no consideration was given to the increased air flow resistance the introduction of the heat exchanger would cause. The results indicated that roughly 30% of the heat is possible to recover in comparison to a traditional kiln. It was finally concluded that the influence of ingoing process parameters needs to be implemented in the kiln control system to fully utilize the kilns potential.

1 - 27 of 27
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