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  • 1.
    Ah Shenga, Pedro António
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Simulation of Tropical Hardwood Processing: Sawing Methods, Log Positioning, and Outer Shape2015Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, nr 4, s. 7640-7652Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To increase understanding of breakdown strategies for Mozambican timber, simulations were carried out using different sawing patterns that can be alternatives to the low degree of refinement performed for export today. For the simulations, 3D models of 10 Jambirre and 5 Umbila logs were used. The log shape was described as a point cloud and was acquired by 3D-laser scanning of real logs. Three sawing patterns (cant-sawing, through-and-through sawing, and square-sawing) were studied in combination with the log positioning variables skew and rotation. The results showed that both positioning and choice of sawing pattern had a great influence on the volume yield. The results also showed that the log grade had an impact on the sawing pattern that should be used for a high volume yield. The volume yield could be increased by 3 percentage points by choosing alternative sawing patterns for fairly straight logs and by 6 percentage points for crooked logs, compared to the worst choice of sawing pattern.

  • 2.
    Ah Shenga, Pedro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield2017Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, nr 4, s. 257-262Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The sawmill industry is a very important link in the Mozambique forest products value chain, but the industry is characterized by undeveloped processing technology and high-volume export of almost unrefined logs. The low volume yield of sawn timber has been identified as a critical gap in the technological development of the industry. To improve the profitability of the industry, there is thus a need to develop methods and techniques that improve the yield. In this paper, different positioning of logs prior to sawing and the possibility of increasing the volume yield of crooked logs by bucking the logs before sawing have been studied. A computer simulation was used to study the cant-sawing and through-and-through sawing of the logs to determine the volume yield of sawn timber from the jambirre (Millettia stuhlmannii Taub.) and umbila (Pterocarpus angolensis DC.) species. The optimal position, i.e. the position of the log before sawing that gives the highest volume yield of sawn timber for a given sawing pattern when the positioning parameters, offset, skew and rotation, are considered gave a considerable higher volume yield than the horns-down position. By bucking very crooked logs and using the horns-down positioning before sawing, the volume yield can be of the same magnitude as that obtained by optimal positioning on full-length (un-bucked) logs. The bucking reduces the crook of the logs and hence increases the volume yield of sawn timber.

  • 3.
    Ah Shenga, Pedro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    The Effect of Log Position Accuracy on the Volume Yield in Sawmilling of Tropical Hardwood2016Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 4, s. 9560-9571Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigated the effect of the positioning of the log before sawing on the volume yield of sawn timber from tropical hardwood species. Three positioning parameters were studied, the offset, skew, and rotation, combined with two sawing patterns of cant-sawing and through-and-through sawing. A database consisting of two tropical hardwood species with very different outer shapes, jambirre (Millettia stuhllmannii Taub.) and umbila (Pterocarpus angolensis DC.), was used to simulate the sawing process. The result of the simulation revealed that, according to the combined effect of offset, skew, and rotation positioning, the positioning of the log before sawing is extremely important to achieve a high volume yield of sawn timber. The positioning parameter that has the highest effect on the volume yield is the rotation, and the variation in the volume yield associated with a deviation in the positioning can reduce the volume yield of sawn timber by between 7.7% and 12.5%.

  • 4.
    Berg, Sven
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Vaziri, Mojgan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Crack influence on load-bearing capacity of glued laminated timber using extended finite element modelling2015Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, nr 4, s. 335-343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Most of the cracks are caused by changes in temperature and relative humidity which lead to shrinkage and swelling of the wood and thereby induce stresses in the structure. How these cracks influence the strength of the wooden structure, especially the shear strength, is not well understood. However, it is reasonable to expect that cracks have an impact on the shear strength as they preferably run along the beams in the direction of grain and bond lines. The purpose of this study was to investigate the load-bearing capacity of cracked glulam beams and to find a model that could predict the failure load of the beams due to the cracks. Three-point bending tests were used on glulam beams of different sizes with pre-manufactured cracks. An orthotropic elastic model and extended finite element method was used to model the behaviour of the cracked beams and to estimate the load-bearing capacity. The conclusions were validated by numerical simulations of the mechanical behaviour of three-point bending of glulam beams with different crack locations. The crack initiation load was recorded as the failure load and compared to the experimental failure load. The results of the compaction simulations agree well with the experimental results

  • 5. Bianchi, S.
    et al.
    Pena, M.I. Placencia
    Ganne-Chédeville, C.
    Pichelin, F.
    Sandberg, Dick
    Softwood strand-boards manufacturing without adhesive using linear friction welding technology2012Inngår i: Current and Future Trends of Thermo-Hydro-Mechanical Modification of Wood, Université Nancy , 2012, s. 142-143Konferansepaper (Fagfellevurdert)
  • 6.
    Blomqvist, L.
    et al.
    Linnéuniversitetet.
    Johansson, J.
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Moisture-induced distortion of laminated veneer products2013Inngår i: Proceedings of the 9th meeting of the Northern European network for wood science and engineering (WSE): September 11-12, 2013, Hannover, Germany / [ed] C. Brischke; L. Meyer, 2013, s. 178-183Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Laminated veneer products consist of veneers bonded together with adhesive into apredetermined shape. Since wood is a hygroscopic material and also anisotropic bynature, laminated veneer products are especially shape-sensitive to changes in moisturecontent. A deviation from the intended shape is a problem for both the manufacturersand users of the final products and annually such deviations cause great economic lossesin the manufacturing industry.To illustrate the influence of moisture on distortion and shape stability, studies havebeen performed in industrial conditions and in a laboratory environment. Veneers ofbeech and birch and a seat shell moulded from these veneers were used in the study.Distortion, i.e. spring-back, position and twist, has been determined directly aftermoulding and during subsequent moisture and drying cycles.The distortion follows more or less slavishly the changes in relative humidity around theproduct. The distortion is generally small directly after moulding but, after the laminateshave been exposed to a variation in relative humidity, the distortion increases. Some ofthe problems of poor shape stability that may arise later in the bending process can bereduced if attention is paid to moisture content and fibre orientation already in theproduction of the veneer.To achieve good shape stability of laminated veneer products in practice, the followingshould be followed by the manufacture industry:• develop cooperation with suppliers of veneer and set requirements of veneerwith regard to deviation of the fibre orientation, and require that the veneer bedried and conditioned to a moisture content consistent with production,• control incoming veneers with respect to fibre orientation and moisture content,• plan warehousing of veneers and ensure adequate conditioning, and• consider the orientation of the veneers and the species.

  • 7.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Berg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Chipless machining: challanges in manufacture of laminated veneer products2015Inngår i: Proceedings of the 22nd International Wood Machining Seminar, IWMS 22. / [ed] Roger Hernández; Claudia B. Cáceres, Qubec City: Universite Laval , 2015, s. 155-164Konferansepaper (Fagfellevurdert)
  • 8.
    Blomqvist, Lars
    et al.
    Linnӕus University, Department of Building Technology, Växjö, Sweden. RISE, Research Institute of Sweden.
    Berg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Department of Wood Processing and Biomaterials, Czech University of Life Sciences Prague, Prague, Czech Republic.
    Distortion in laminated veneer products exposed to relative-humidity variations: Experimental studies and finite-element modelling2019Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, nr 2, s. 3768-3779Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A shortcoming of the laminated bending process is that the product may become distorted after moulding. This study focused on the influence of fibre orientation deviation for individual veneers on the distortion of a moulded shell. The distortion of 90 cross-laminated shells of the same geometrical shape, consisting of seven peeled birch veneers, were studied under relative humidity variation. All the veneers were straight-grained in the longitudinal-tangential plane, but to simulate a deviation in fibre orientation, some of the individual veneers were oriented at an angle of 7° relative to the main orientation of the other veneers in the laminate. A finite element model (FEM) was applied to study the possibility of predicting the results of a practical experiment. The study confirms the well-known fact that deviation in fibre orientation influences shape stability. The results also show how the placement of the abnormal veneer influences the degree of distortion. From this basic knowledge, some improvements in the industrial production were suggested. However, the FE model significantly underestimated the results, according to the empirical experiment, and it did not show full coherence. The survey shows the complexity of modelling the behaviour of laminated veneer products under changing climate conditions and that there is a great need to improve the material and process data to achieve accurate simulations. Examples of such parameters that may lead to distortion are density, annual ring orientation in the cross section of the veneer, the orientation of the loose and tight sides of the veneer, and parameters related to the design of the moulding tool.

  • 9.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Basic knowledge of wood properties for improved performance of laminated Veneer products2013Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, nr 4, s. 549-556Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Contact free measurement of complex shapes in the wood industry2011Inngår i: Mechano-chemical transformations of wood during THM processing: COST Action FP0904 workshop : February, 16-18, 2011, Biel, Switzerland : book of abstracts / [ed] Parviz Navi; Andreas Roth, Biel: Berne University of Applied Sciences , 2011, s. 143-144Konferansepaper (Fagfellevurdert)
    Abstract [en]

    There is an increasing need to update and correct information about product geometry in the wood manufacturing industry. Changes in machinery or personnel can be the cause of that need. Manual measurement takes time and diff erent ways of digitizing the geometry of the products have therefore been developed.In this study, two methods (3D-coordinate measurement and optical scanning) have been tested together in order to determine the position of a product in relation to the processing machine, and to optically scan the product geometry. The aim was to identify and evaluate methods to digitize product geometry into a CAD-model for the wood industry. Th e seat shell measured was fitted in the CNC-machine where the processing later would be performed.The methodology used has made it possible to create a CAD-model from the physical model. Based on the experience from this methodology, it would be recommended to continue by creating of a tool that minimizes the need for after processing, i.e. the adjustment of certain coordinates manually.

  • 11.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Improving the performance of bended laminated veneer products2011Inngår i: Mechano-chemical transformations of wood during THM processing: COST Action FP0904 workshop : February, 16-18, 2011, Biel, Switzerland : book of abstracts / [ed] Parviz Navi; Andreas Roth, Biel: Berne University of Applied Sciences , 2011, s. 147-148Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Laminated bending of veneers mean that dried, thin veneers or thin wood sheets are glued together under influence of pressure and eventually increased temperature. At the same time the product is given its desired shape, most often curved. This thermo hydro mechanical process offers several benefits. For example thick bends of small radiuses of any species of wood may be formed and poor quality wood containing knots, splits and other defects may be utilised. Laminated bends can usually be set more readily and made to conform better to the shape of the form than similar bends of solid wood. Further no softening treatment is generally required before the pieces are bent. However, there are also disadvantages e.g. more technical skill and better equipment are usually required than for solid wood bending. The presence of glue may be somewhat detrimental to the machines used for the final cleaning up of the bent pieces. Further the glue lines which are usually visible on the sides may be an aesthetical unappreciated effect [1],[2].The quality of the laminated bended veneer products are obtained as an interaction between the process, the veneers and the glue [3]. In industries designing and producing these products it is of interest to obtain better understanding of how processing- and material parameters affect the product quality. With an improved understanding of the material and processing parameters it may be possible to increase the efficiency of wood utilisation and promote the development of new processes and products that manipulate the viscoelastic nature of wood. In particular the possibilities to obtain narrower radius of curvature and better possibilities of bending in more than one plane would be advantageous.This study has focused on the moisture content (MC) and the grain angle orientation in the veneers. These two specific aspects were assumed to have a great influence on spring-back and distortions of the laminated bended veneer products. Spring-back and distortions were therefore studied in separate tests where MC and the grain angle orientation was varied separately in manufactured laminated bended wood products. After manufacturing the products were exposed to variations in humidity and temperature whereupon the spring-back and distortions were measuredThree tests were performed. For the first and the second test a seat shell was selected as test product, figure 1a. To the third test another product was selected, figure 1b. This product was a small bookshelf. The company producing this shelf had experienced large problems considering distortions of this product. Further the product was very simple in shape with only one bend and therefore suitable for measurements.In the first test the influence of MC of the veneers was investigated. In the second and third test the influence of grain angle of the veneers was studied.For the study veneers of birch and beech were selected in the production. For the first and third study only birch veneers were used. The veneers were initially conditioned to equilibrium moisture contents (EMC) according to setups in different test groups. For the first study a test group was also built up from veneers taken directly out of production to study the industrial conditions. The seat shells in this test group contained veneers conditioned to EMC 4 %, except for the surface veneers that had been stored in the production hall. The humidity and temperature conditions in this room corresponded to MC 7 %.The manufacturing of the products were performed in industrial conditions. In the tests the products were built up from a number of veneers and the studied factors were varied between the veneers in a controlled manner.The results from the first test showed that the MC of the veneers influenced the spring-back and the distortions. A large moisture gradient between veneers and especially unsymmetrical placements of these in the construction were especially critical. The results from the second and third tests showed that grain angle deviation has large effect on the distortions of the products. Even a small grain angle deviation as in study two (5°) resulted in large problems with distortions. The study also showed that when crossing two or more veneers with deviating grain angles there were cases when these faults interacted and multiplied the distortions. In production grain angle deviations can be a result of inaccurate placement of the veneers during pressing, incorrect cutting of the veneers, inherent from the growth of the tree or a combination of these factors. Deviations of the grain angle were, however, shown to have only small effects on spring-back.

  • 12.
    Blomqvist, Lars
    et al.
    Linnæus University, Forestry and Wood Technology.
    Johansson, Jimmy
    Linnæus University, Forestry and Wood Technology.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Modification of surface veneer to reduce damage in laminated veneer products during manufacturing2014Inngår i: Final Cost Action FP0904 Conference: “Recent Advances in the Field of TH and THM Wood Treatment” : May 19-21, 2014, Skellefteå, Sweden : book of abstracts / [ed] Mojgan Vaziri; Dick Sandberg, Skellefteå: Luleå tekniska universitet, 2014, s. 50-51Konferansepaper (Fagfellevurdert)
  • 13.
    Blomqvist, Lars
    et al.
    Linneaus University.
    Johansson, Jimmy
    Linneaus University.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Moisture-induced distortion of laminated veneer products.2014Inngår i: 68th Forest Products Society International Convention, Quebec City, Canada, August 10-13, 2014, 2014Konferansepaper (Annet vitenskapelig)
  • 14.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Shape stability of laminated veneer products: an experimental study of the influence on distortion of some material and process parameters2013Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, nr 3, s. 198-211Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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 the influence of different UF-adhesive systems, adhesive distribution, and veneer properties such as species, moisture content, and fibre orientation. Two different species were studied: beech (Fagus silvatica L.) and birch (Betula pubescens Ehrh.). Distortion was determined directly after moulding and after storage in a changing relative humidity. The aim of the work was to study how the above-mentioned material and process parameters influence the distortion. The results show that the material and process parameters and the storage in a changing relative humidity had a clear impact on distortion. Fibre orientation, differences in moisture content between veneers, and the moisture gradient in the final product are identified in this study as being the most important parameters influencing the distortion and shape stability of laminated veneer products

  • 15.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Shape stability of laminated veneer products: How to decrease the negative effects of fibre deviation?2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A shortcoming of the laminated bending process is that the products may become distorted after moulding and during use. Annually, significant financial losses have incurred in the furniture and interior design industries as a result of distorted products. In this study, we have examined the influence of deviation of fibre orientation of individual veneers on distortion of a moulded shell to find ways to improve shape stability of laminated veneer products.Ninety cross-laminated shells, consisting of 7 veneers of Birch (Betula pubescens Ehrh.) with a total thickness of 3.6 mm, were studied. The in-plane dimensions of the veneer were 400x660 mm. All the veneers were straight-grained, but to simulate deviation in fibre orientation some of the individual veneers were oriented 7 degrees relative to the main orientation of the other veneers in the laminate. Distortion was determined directly after moulding and after storage in a changing relative humidity.The results show the well-known fact that deviation of fibre orientation of the veneers in the laminate influences the shape stability of the product. The results from this study, however, also show how the placement of the abnormal veneers in the laminated veneer products influences the degree of distortions. From this basic knowledge some improvements for production of laminated veneer products were suggested.

  • 16.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Shape stability of THM-processed laminated veneer products glued with bio-based adhesive systems2013Inngår i: Evaluation, processing and predicting of THM treated wood behaviour by experimental and numerical methods / [ed] Carmen-Mihaela Popescu; Maria-Cristina Popescu, 2013, s. 99-100Konferansepaper (Fagfellevurdert)
  • 17.
    Blomqvist, Lars
    et al.
    Linneaus University.
    Johansson, Jimmy
    Linneaus University.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Veneer modification for improved formability when moulding laminated veneer products.2014Inngår i: 68th Forest Products Society International Convention, Quebec City, Canada, August 10-13, 2014, 2014Konferansepaper (Annet vitenskapelig)
  • 18.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Kifetew, Girma
    Linnéuniversitetet.
    The influence of individual veneer orientation on the shape stability of planar lamination2012Inngår i: Current and Future Trends of Thermo-Hydro-Mechanical Modification of Wood: Opportunities for new markets? / [ed] Mathieu Pétrissans; Philippe Gérardin, Nancy: Université Nancy , 2012, s. 160-162Konferansepaper (Fagfellevurdert)
  • 19.
    Blomqvist, Lars
    et al.
    Forest and Wood Technology, Linnæus University.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Johansson, Jimmy
    Linnæus University, Forestry and Wood Technology.
    Influence of veneer orientation on shape stability of plane laminated veneer products2014Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, nr 4, s. 224-232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the most important quality aspects of a laminated veneer product is its shape stability under changing relative humidity (RH). This study aimed to establish an understanding of how the orientation of individual veneers in the laminate, i.e., orientation according to fibre orientation and orientation of the loose (the side with ‘lathe checks’) or tight side of the veneer, affects the shape stability. Three-ply laminates from peeled veneers of beech (Fagus sylvatica L.) were studied. The four types of laminate were the following: loose sides of all veneers in the same direction (cross and parallel centre ply) and loose sides of the outer veneers facing inward (cross and parallel centre ply). Four replicates of each type yielded 16 samples. The samples were exposed to RH cycling at 20% and 85% RH at 20°C, and the shapes of the samples were determined. The shape stability was influenced by the veneer orientation. Laminations with the middle veneer perpendicular to the top and bottom veneer (cross-laminated) showed the best shape stability, especially when the loose sides of the veneers were oriented the same direction. In parallel-laminated veneers, the laminates with opposite directions of the loose sides in the two outermost veneers showed the best shape stability. The major explanation of the behaviour of the laminates is that the loose side expanded more than the tight side from the dry to the humid climate, which was shown by optical 3D deformation analysis (ARAMISTM). After RH cycling, the laminates with cross plies showed visible surface checks only when the tight side was facing outwards.

  • 20.
    Blomqvist, Lars
    et al.
    Linneaus University.
    Sterley, Magdalena
    SP Technical Research Institute of Sweden, SP Wood Technology, Skellefteå.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Johansson, Jimmy
    Department of Forestry and Wood Technology, Linnæus University.
    The effect of veneer-modifcation on the bond-strength in laminated veneer products2015Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, nr 4, s. 43-49Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 21.
    Blomqvist, Lars
    et al.
    Department of Forestry and Wood Technology, Linnæus University.
    Sterley, Magdalena
    SP Technical Research Institute of Sweden, Wood Technology.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Johansson, Jimmy
    Department of Forestry and Wood Technology, Linnæus University.
    The influence of veneer modification on adhesive bond strength2014Inngår i: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE) / [ed] Peter Wilson, Edinburgh: Edinburgh Napier University. , 2014, s. 150-155Konferansepaper (Fagfellevurdert)
  • 22.
    Báder, Mátyás
    et al.
    University of Sopron, Sopron, Hungary.
    Bak, Miklós
    University of Sopron, Sopron, Hungary.
    Németh, Róbert
    University of Sopron, Sopron, Hungary.
    Rademacher, Peter
    Mendel University in Brno, Brno, Czech Republic.
    Rousek, Radim
    Mendel University in Brno, Brno, Czech Republic.
    Horníček, Stanislav
    Mendel University in Brno, Brno, Czech Republic.
    Dömény, Jakub
    Mendel University in Brno, Brno, Czech Republic.
    Klímek, Petr
    Mendel University in Brno, Brno, Czech Republic.
    Kudela, Jozef
    Technical University in Zvolen, Zvolen, Slovakia.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Neyses, Benedikt
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Kutnar, Andreja
    University of Primorska, Koper, Slovenia; InnoRenew CoE, Izola, Slovenia.
    Wimmer, Rupert
    University of Natural Resources and Life Sciences, Vienna, Austria; Renewable Materials, Tulln an der Donau, Austria.
    Pfriem, Alexander
    Eberswalde University for Sustainable Development, Eberswalde, Germany.
    Wood densification processing for newly engineered materials2018Inngår i: Proceedings of the 5th International Conference on Processing Technologies for the Forest and Bio-based Products Industries (PTF BPI 2018), Freising/Münich, September 20-21 / [ed] M. C. Barbu; A. Petutschnigg; E. M. Tudor, Kuchl, 2018, s. 255-263Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wood is a renewable, bio-based material with a mixture of different properties and qualities, used in numerous applications. Beside many species with high wood qualities several species suffer due to a number of disadvantages, where low hardness and abrasive resistance are characteristic for low-density species. This paper presents examples of on-going European research projects and industrial processes mostly related to wood densification methods. Wood densification is a classical thermohydro-mechanical (THM) wood treatment process, through which density is increased by mechanical compression of wood perpendicular to the grain, by impregnation of cell lumens or cell walls with solutions or melted substances (resins, waxes), or by a combination of both. The purpose is to produce newly designed and engineered materials and products with new property profiles, which would potentially find new markets. In general, the THM processes consist of three stages: plasticization of the wood cells, followed by the actualcompression, and finally solidification of the compressed wood in order to prevent elastic spring-back and the moisture-induced set-recovery. The wood densification process refers but is not limited to solid wood and might apply to whole wood pieces, or to local areas within given pieces only. Another THM method is the mechanical compression of wood parallel to the grain, which leads to a product with high flexibility. A European wood research network, represented by the authors of this contribution, has extended experience in many wood modification processes, as demonstrated through ongoing researches and case studies in this paper

  • 23.
    Carlsson, Staffan
    et al.
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Eskilander, Stephan
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Sandberg, Dick
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Utvärdering av deplacementmetod med vatten för bestämning av träets torrdensitet1996Rapport (Annet vitenskapelig)
  • 24.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Department of Ocean Operations and Civil Engineering. Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Ahec, Ambroz
    University of Ljubljana.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    CT-scanning of the drying process of Eucalyptus nitens.2018Inngår i: Proceedings of 21st International Drying Symposium. / [ed] Cárcel JA, Polo GC, García-Pérez JV, Mulet A, Rosselló C.,, Valencia: Editorial Universitat Politècnica de València , 2018, s. 1269-1276Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The drying of Eucalyptus nitens is a troublesome process as the species is extremely prone to drying defects. This paper reports ongoing research toimprove the understanding of surface checking and cell collapse in Chilean grown Eucalyptus nitens during drying. Computed tomography (CT) scanning was used as a powerful tool for studying the internal changes in the wood-material during the drying process. Different levels of temperatures have been tested with the same equilibrium moisture content (EMC) conditions and low air velocity. The results confirm that a low drying temperature and a low air velocity, which results in a slow rate of drying, reduce internal cell collapse and surface checking .

  • 25.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Dual-energy X-ray absorptiometry for measuring moisture content in wood – Is it possible?2019Inngår i: Proceedings of the 21st International Nondestructive Testing and Evaluation of Wood Symposium, Freiburg, Baden-Württemberg, Germany, September 24–27, United States Department of Agriculture , 2019, s. 292-292Konferansepaper (Fagfellevurdert)
  • 26.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    In situ CT-scanning for detection of internal checking and cell collapse during drying of hardwood species2016Inngår i: The 7th European Conference on Hardwood, Eco-efficient resource wood with special focus on hardwoods / [ed] Teischinger A., Németh R., Rademacher P., Bak M. & Fodor F. (Eds.), Sopron: University of West Hungary , 2016, s. 58-59Konferansepaper (Fagfellevurdert)
    Abstract [en]

    During the drying of sawn timber, hydrostatic tension forces within the cell may exceed the compressive strength perpendicular to the grain of the thin cell wall and the cell then collapses. This phenomenon is common in hardwoods such as Sequoia sempervirens, Thuja plicata, Tsuga heterophylla, Juglans nigraand many species of eucalyptus and oak. Usually, this leads to severe surface deformation, and both surface and internal checking(honeycombing) may occur. The quality of the final product is lowered by these cracks and deformations. The aim of this study was to investigate, by CT-scanning samples throughout the drying process, whether it is possible to detect when and how cracking and deformation occurs and develops in specimens of Eucalyptus nitens. Based on this knowledge, better drying schedules can be developed to improve the yield and ensure a higher quality of the sawn timber. Three specimens, one specimen in each drying run, of Eucalyptus nitens were used for the tests. Their cross-sectional dimensions, prior to drying, were 105x23 mm2 and their length was 70 cm. A specially designed laboratory drying kiln that fits within the gantry of a Siemens Somatom Emotion medical CT-scanner was used (Fig. 1). With this equipment, it is possible to scan the inside of the kiln without interrupting the drying process.

  • 27.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    CT-studies during the Conditioning phase of the Wood Drying Process2018Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Computed tomography (CT) during drying of sawn timber is an excellent non-destructivetechnique to study the moisture flux as a function of drying time. In this study, a climatechamber combined with a medical CT- scanner has been used for non-destructive studies ofdensity changes in sawn timber during drying and conditioning.Green sawn timber contains large amounts of water and has to be dried before it can befurther processed and used in various building applications. The most common dryingmethod is convective air-circulation drying in large industrial kilns, where the relativehumidity (RH) of the hot circulating air is gradually reduced until the timber reaches thetarget moisture content (MC).Drying of sawn timber is driven by the existence of a difference in MC between the coreand the surface, so that moisture moves from the wet inner region towards the drier outerregion. During the early capillary stages of drying, the drying rate is high while, at the laterstages when all liquid water has evaporated, the drying rate is slow and diffusioncontrolled.At the end of the drying process, the timber surface is always drier than its core.In addition to this moisture gradient, internal stresses develop within the cross section withcompression stresses in the timber surface and tension in the inner regions. To avoidunwanted distortions, both these stresses and the moisture gradient, need to be eliminatedbefore the timber is further processed. This is achieved in a final conditioning stage withinthe drying process by moistening the circulating air through steaming or water spraying.The aim of the present work was to optimize the conditioning stage by developing amethod for studying of moisture gradients, deformations and internal and externaldimensional changes in sawn timber during the conditioning phase by using a CT-scannercombined with a drying unit for in-situ measurements of moisture flow.The results show that it is possible to detect the moisture gradient between the surface andcore of the timber with satisfactory reliability, but not the internal and external dimensionalchanges. However, this method creates a potential for increasing the knowledge andunderstanding of the conditioning phase and makes it possible to optimize and develop thisstep in the drying process to improve the yield and ensure a higher quality of the sawntimber.

  • 28.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    The use of X-ray computed tomography in timber construction research2016Inngår i: New Horizons for the Forest Products Industry: 70th Forest Products Society International Convention, June 26-29, Portland, Oregon, USA, Madison: Forest Products Society, 2016Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    powerful tool for the non-destructive measurement of dynamic processes in wood. For more than 20 years, CT has been used in wood research at Luleå University of Technology. The uniqueness of the CT equipment means that processes such as drying, modification, water absorption, internal and external cracking and material deformation can be studied in temperature- and humidity-controlled environments. The data recorded by the CT during the process is converted into two- or three-dimensional images that for instance can show dynamic moisture behavior in wood drying.This paper gives an overview of the possibilities of using CT in timber construction research, and shows examples of applications and results which can be particularly difficult to achieve using other methods. A specific focus is on studies on wood products for construction, and how to deal with different material combinations such as wood and metal.The practical application of the result is that CT-scanning, combined with image processing, can be used for non-destructive and non-contact 3-D studies of exterior constructions elements during water sorption and desorption, to study swelling and shrinking behaviour, delamination phenomena, crack development, etc.

  • 29.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Lindgren, Owe
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Söderström, Ove
    c Professor Emeritus of Building Materials, Stockholm, Sweden.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Real-time wood moisture-content determination using dual-energy X-ray computed tomography scanning2019Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The estimation of the pixel-wise distribution of the moisture content (MC) in wood using X-ray computed tomography (CT) requires two scans of the same wood specimen at different MCs, one of which is known. Image-processing algorithms are needed to compensate for the anisotropic distortion that wood undergoes as it dries. An alternative technique based on dual-energy CT (DECT) to determine MC in wood has been suggested by several authors. The purpose of the present study was to evaluate the hypothesis that DECT can be used for the determination of MC in real time. A method based on the use of the quotient between the linear attenuation coefficients (μ) at different acceleration voltages (the so-called quotient method) was used. A statistical model was created to estimate the MC in solid sapwood of Scots pine, Norway spruce and brittle willow. The results show a regression model with R2 > 0.97 that can predict the MC in these species with a RMSE of prediction of 0.07, 0.04 and 0.11 (MC in decimal format) respectively and at MC levels ranging from the green to the totally dry condition. Individual measurements of MC show an uncertainty of up to ±0.4. It is concluded that under the conditions prevailing in this study, and in studies referred to in this paper, it is not possible to measure MC with DECT.

  • 30.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Lindgren, Owe
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Söderström, Ove
    c Professor Emeritus of Building Materials, Stockholm, Sweden.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Real-time wood moisture-content determination using dual-energy X-ray computed tomography scanning2019Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, nr 6, s. 437-444Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The estimation of the pixel-wise distribution of the moisture content (MC) in wood using X-ray computed tomography (CT) requires two scans of the same wood specimen at different MCs, one of which is known. Image-processing algorithms are needed to compensate for the anisotropic distortion that wood undergoes as it dries. An alternative technique based on dual-energy CT (DECT) to determine MC in wood has been suggested by several authors. The purpose of the present study was to evaluate the hypothesis that DECT can be used for the determination of MC in real time. A method based on the use of the quotient between the linear attenuation coefficients (μ) at different acceleration voltages (the so-called quotient method) was used. A statistical model was created to estimate the MC in solid sapwood of Scots pine, Norway spruce and brittle willow. The results show a regression model with R2 > 0.97 that can predict the MC in these species with a RMSE of prediction of 0.07, 0.04 and 0.11 (MC in decimal format) respectively and at MC levels ranging from the green to the totally dry condition. Individual measurements of MC show an uncertainty of up to ±0.4. It is concluded that under the conditions prevailing in this study, and in studies referred to in this paper, it is not possible to measure MC with DECT.

  • 31.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Neyses, Benedikt
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    In-situ moisture content and density measurements in surface densified wood using dual X-ray absorptiometry in medical CT-scanning2016Inngår i: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium, Bio-based composites for a sustainable future., Concepción: University of Concepción , 2016, Vol. 2, s. 92-, artikkel-id NA01Konferansepaper (Fagfellevurdert)
  • 32.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    The use of X-ray computed tomography in bio-composite research2016Inngår i: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium : Bio-based composites for a sustainable future,, Conceptión: University of Concepción , 2016, s. 42-45Konferansepaper (Fagfellevurdert)
    Abstract [en]

    X-ray computed tomography (CT), which was introduced in the medical field in the early 1970s, is also a powerful tool for the non-destructive measurement of dynamic processes in wood. For more than 20 years, medical CT has been used in wood research at Luleå University of Technology. The uniqueness of the CT equipment allowsprocesses such as drying, modification; water absorption; internal and external cracking; and material deformation to be studied in temperature- and humidity-controlled environments. The data recorded by the CT scanner during the process is converted into two or three dimensional images that, for instance, can show dynamic moisture behaviour in wood drying and crack formation. This paper provides an overview of the possibilities of using CT in bio-composite research, and shows examples of applications and results that can be particularly difficult to achieve using other methods. A specific focus is on studies on wood products that use combinations with materials such as metal and especially about how to deal with the difficulties that this entails.The practical application of the result is that CT scanning, combined with image processing, can be used for non-destructive and non-contact three-dimensional s tudies of exterior construction elements during water sorption and desorption, to study parameters such as swelling and shrinking behaviour; delamination phenomena; and crack development.

  • 33.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Norwegian University of Science and Technology (NTNU), Department of ICT and Natural Sciences, Norway.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    CT scanning of capillary phenomena in bio-based materials2017Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, nr 4, s. 181-187Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 34.
    Cristescu, Carmen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Neyses, Benedikt
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Söderström, Ove
    Kungliga tekniska högskolan, KTH, KTH Byggnadsmateriallära.
    Modeling of the temperature distribution in self-bonded beech-veneer boards during hot pressing2015Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, nr 4, s. 97-103Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 35.
    Cristescu, Carmen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Self-bonding of veneers with heat and pressure: a full scale test2014Inngår i: Final Cost Action FP0904 Conference: “Recent Advances in the Field of TH and THM Wood Treatment” : May 19-21, 2014, Skellefteå, Sweden : book of abstracts, Skellefteå: Luleå tekniska universitet, 2014, s. 76-Konferansepaper (Fagfellevurdert)
  • 36.
    Cristescu, Carmen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Influence of pressing parameters on mechanical and physical properties of self-bonded laminated beech boards2015Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, nr 2, s. 205-214Artikkel i tidsskrift (Fagfellevurdert)
  • 37.
    Cristescu, Carmen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Could colour predict hardness of hot-ptressed self-laminated beech boards2015Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, nr 4, s. 150-156Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 38.
    Cristescu, Carmen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Markers of quality in self-bonded beech boards2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A self-bonding phenomenon takes place when five layers of beech (Fagus SylvaticaL.) veneers are pressed at temperatures higher than 200ºC. If the pressing temperature between veneer surfaces reaches at least 225ºC during pressing and if the pressure applied is optimal, water-resistant bonds are formed between veneers. This study investigates the relation of thickness reduction (marker of compression) and mass loss (marker of heat treatment intensity) to boards quality. The effect of water and water vapour on the bondings between veneer in boards pressed at 200, 225 and 250ºC is studied. The conclusion is that pressing 5 layers of 2 mm rotary-cut beech veneer parallel-fibered at 225ºC, 5 MPa and 300 s leads to a thickness reduction of 33.4 % and mass loss of 1.23 %; in such boards bondings are not resistant to liquid water but are resistant to vapour after one adsorption-desorption cycle. When pressing at 250ºC, 5 MPa and 300 seconds, the thickness reduction is 50% and the mass loss 4%; in such boards no delamination was observed when soaked in water. Boards pressed athigher temperature show lower hygroscopicity. Their equilibrium moisture content (EMC) rangedbetween 3.6 and 7%. Based on the results of this study it ishypothesised that the decay resistance of self-bonded boards will increase when increasing the severity of the hot-pressing.

  • 39. Dvinskikh, Sergey V.
    et al.
    Furó, István
    Sandberg, Dick
    Söderström, Ove
    Kungliga tekniska högskolan, KTH.
    Moisture content profiles and uptake kinetics in wood cladding materials evaluated by a portable nuclear magnetic resonance spectrometer2011Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, nr 3, s. 119-127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study evaluated the capability of nuclear magnetic resonance (NMR) technology based on small portable magnets for in situ studies of the local moisture content in wood. Low-field and low-resolution [1H]NMR with a unilateral permanent magnet was used to monitor and map the moisture content of wood cladding materials of various types in a spatially resolved manner. The results show that portable NMR equipment based on small open-access permanent magnets can be successfully used for non-invasive monitoring of the moisture content in various extended wood specimens. The moisture content was measured with a depth resolution of 0.2 mm and a maximum penetration depth of 3 mm. This makes the technique suitable for in situ local moisture content measurements beneath a coating layer in the cladding, for example, and it is also possible to relate the moisture level to specific properties of the wood material.

  • 40.
    Ekatarina, Siderova
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Composition of monosaccharides in aqueous extracts of thermally modified wood.2018Inngår i: ECWM9 - The 9th European Conference on Wood Modification / [ed] Jos Creemers, Thomas Houben, Bôke Tjeerdsma, Holger Militz, Brigitte Junge and Jos Gootjes, Wageningen: SHR Wageningen, The Netherlands , 2018, s. 575-580Konferansepaper (Fagfellevurdert)
  • 41.
    Eliasson, Lars
    et al.
    Linneaus University.
    Berg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Some aspects on the more efficient use of wood in the industrial manufacture of single-fammily timber houses2015Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, nr 4, s. 418-425Artikkel i tidsskrift (Fagfellevurdert)
  • 42.
    Eliasson, Lars
    et al.
    Linnéuniversitetet.
    Sandberg, Dick
    Trähusföretag tappar fördel i slarvig tillverkning2011Inngår i: Husbyggaren, ISSN 0018-7968, nr 7, s. 24-27Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    Ska trä öka sin konkurrenskraft måste trähusföretag och virkesleverantörer bli bättre på att både ställa och uppfylla kravspecifikationer. Idag kan materialspill och felleveranser uppgå till närmare en femtedel av virkeskostnaden.Trähusbranschen står inför ett antal utmaningar. Avgörande är att kunna producera attraktiva bostäder till en kostnad som inte är högre än att människor har råd.Trähusföretagen utnyttjar inte fullt ut material och metoder som är anpassade för en effektiv produktion av hus i fabrik. I den kontexten får träets miljöfördelar en underordnad betydelse i konkurrensen med andra mindre miljömässigt uthålliga material.

  • 43.
    Elustondo, Diego
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sidorova, Ekaterina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Development of method for surface modification of wood.2015Inngår i: Proceedings of the Eighth European Conference on Wood Modification: ECWM8 / [ed] Mark Huges; Lauri Rautkari; Tuuli Uimonen; Holger Militz; Brigitte Junge, Helsinki: Aalto University, School of Chemical Engineering , 2015, s. 137-140Konferansepaper (Fagfellevurdert)
  • 44.
    Elustondo, Diego
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Örberg, Håkan
    Swedish University of Agricultural Sciences.
    Xiong, Shaojun
    SLU, Umeå, Swedish University of Agricultural Sciences, Umeå.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Measuring moisture content and shrinkage during drying of biological materials through CT-scanner technology.2015Inngår i: Proceedings of the 5th European Drying Conference (EuroDrying’2015), Budapest: Szent István University, Gödöllő , 2015, s. 113-119Konferansepaper (Fagfellevurdert)
  • 45.
    Fransson, Jonas
    et al.
    Växjö universitet.
    Olsson, Axel
    Växjö universitet.
    Witten, Thomas
    Växjö universitet.
    Sandberg, Dick
    Växjö universitet.
    Svenska barr- och lövträd: användning och anatomi.2007Rapport (Annet vitenskapelig)
  • 46.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    The Use of CT-Scanning Technology in Wood Value-Chain Research and in Wood Industry: A State of The Art2017Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, nr 4, s. 533-539Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 47.
    Gaff, Milan
    et al.
    Czech University of Life Sciences Prague (CULS).
    Babiak, Marián
    Czech University of Life Sciences Prague (CULS).
    Kačík, František
    Czech University of Life Sciences Prague (CULS), Technical University in Zvolen.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Turčan, Marek
    Czech University of Life Sciences Prague (CULS).
    Hanzlíka, Peter
    Czech University of Life Sciences Prague (CULS).
    Vondrová, Veronika
    Czech University of Life Sciences Prague (CULS).
    Plasticity properties of thermally modified timber in bending: the effect of chemical changes during modification of European oak and Norway spruce.2019Inngår i: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 165, s. 613-625Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The plasticity of thermally modified European oak (Quercus robur L.) and f thermally modified Norway spruce (Picea abies Karst. (L.)) timber was evaluated in bending, and the plastic properties were related to the changes in chemical composition of the wood after modification. The objective was to gain new knowledge about the properties of materials in the plastic region of the force-deformation diagram in bending. A new software was developed (MATESS) and used to identify important characteristics of the material. This software eliminates shortcomings in current standards, such as simplifications in the evaluation of data when sufficiently sensitive measuring equipment is not available. The characteristics studied were: modulus of rupture (MOR), plastic potential (PP) chord modulus (CHM), the moduli of plasticity (EE), and the moduli of plasticity (EMV, EP). Extractives, lignin, cellulose, holocellulose, and hemicelluloses were analysed chemically to reveal the patterns that occur during the loading of the specimens. Thermal modification has different effects on the mechanical properties of oak and spruce, especially on CHM, EMV and EP, due to their different contents and structures of their chemical components. A strong correlation (r > 0.90) between hemicellulose content and MOR and Pp values was found for both species. The coefficients of determination indicated a very low dependence (r2 < 0.1) of MOR, PP, CHM, EE, EMV and EP, on the average density.

  • 48.
    Gaff, Milan
    et al.
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague,Suchdol, Czech Republic.
    Kačík, František
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague,Suchdol, Czech Republic.Department of Chemistry and Chemical Technologies, Faculty of Wood Sciences and Technology, Technical University in Zvolen, Zvolen, Slovakia.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague,Suchdol, Czech Republic.
    Babiak, Marián
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague,Suchdol, Czech Republic.
    Turčani, Marek
    Department of Forest Protection and Entomology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Suchdol, Czech Republic.
    Niemz, Peter
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague,Suchdol, Czech Republic.
    Hanzlík, Peter
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague,Suchdol, Czech Republic.
    The effect of chemical changes during thermal modification of European oak and Norway spruce on elasticity properties2019Inngår i: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 220, s. 529-538Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The elasticity in bending of European oak (Quercus robur L.) and Norway spruce (Picea abies (L.) Karst.) timber was evaluated before and after thermal modificationand related to the changes in chemical composition of the wood as a result of the modification. A new software was developed (MATESS) and used to identify characteristic points on the force-deformation diagram. The modulus of elasticity(MOE), stress at the limit of proportionality (LOP) and elastic potential (PE) were used to describe the wood properties. Extractives, lignin, cellulose, holocellulose, and hemicelluloses were analysed to reveal the patterns that occur during the loading of the specimens. Thermal modification lowers the mechanical properties (MOE, LOP and PE) of oak and spruce wood, and the reduction increases with increasing modification temperature. Changes in chemical composition of thermally modified wood show a strong relationship to the reduction in elasticity properties for bot species.

  • 49.
    Garskaite, Edita
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Stankeviciute, Zivile
    Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Vilnius, Lithuania.
    Aivaras, Kareiva
    Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Vilnius, Lithuania.
    Jones, Dennis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Surface hardness and flammability of Na2SiO3 and nano-TiO2 reinforced wood composites2019Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, nr 48, s. 27973-27986Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this study was to explore an effect of the combined inorganic materials on the wood hardness and flame-retardancy properties in a concept of sustainable material management. Herein, the reinforcement of Scots pine (Pinus sylvestris L.) sapwood with sodium silicate and TiO2 nanoparticles via vacuum-pressure technique is reported. Pyrolysis of modified wood was studied by TG-FTIR analysis; the results showed that maximum weight loss for the modified wood was obtained at 40–50 °C lower temperatures compared to the reference untreated wood. The Gram–Schmidt profiles and spectra extracted at maxima absorption from Gram–Schmidt plots indicated chemical changes in wood–inorganic composites. SEM/EDS analysis revealed the presence of Na–O–Si solid gel within the wood-cell lumen and showed that TiO2 was homogeneously distributed within the amorphous Na–O–Si glass-forming phase to form a thin surface coating. EDS mapping further revealed the higher diffusivity of sodium into the cell wall compared to the silicon compound. The presence of amorphous sodium silicate and nano-TiO2 was additionally confirmed by XRD analysis. FTIR spectra confirmed the chemical changes in Scots pine sapwood induced by alkalization. Brinell hardness test showed that the hardness of the modified wood increased with the highest value (44% increase in hardness) obtained for 10% Na2SiO3–nTiO2 modified wood. The results showed good correlation between TG and flammability test; limiting oxygen index (LOI) values for the wood–inorganic composites increased by 9–14% compared to the untreated wood.

  • 50.
    Hemmilä, Venla
    et al.
    Linnéuniversitetet.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Modified Wood-Protein Adhesive Bondline Strength Development during Curing2014Inngår i: The seventh European Conference on Wood Modification: Book of Abstracts / [ed] Lina Nunes; Dennis Jones; Callum Hill; Holger Militz, Lissabon, 2014, s. 134-137Konferansepaper (Fagfellevurdert)
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