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  • 1.
    Ahmed, Sheikh Ali
    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.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Development of a new rapid method for mould testing in a climate chamber: Preliminary tests2013In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, no 4, p. 451-461Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to develop fast, simple and robust solid wood mould testing methods for the use in small-scale laboratory tests. The objective was to investigate mould susceptibility of different wood materials within the batches. The proposed method is based on natural contamination of non-sterile surfaces in climates conducive to mould growth. For this purpose, a climate chamber with regulated temperature and relative humidity was used. The conditioning chamber was divided into upper and lower chamber by a thin layer of stainless steel placed horizontally above the fan to minimise air circulation to the sample in the upper compartment. Mould-infected samples from outdoor tests were used as a source of mould inocula, and test trials were conducted on Scots pine (Pinus sylvestris L.) sapwood. Samples were suspended from the top of the upper chamber, and the chamber was exposed to different temperature and humidity levels. Severe mould infestation was observed after 12-14 days of incubation. Visual mould rating was then performed. Regardless of some constraints, this test method was very simple, fast, and effective. More importantly, unlike other test methods, it closely models mould infestation as it would occur under natural condition.

  • 2.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Microwave drying of pine and spruce1995In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, no 5, p. 333-338Article in journal (Refereed)
    Abstract [en]

    microwave energy consumption from 365 to 760 kWh/m 3. Internal wood temperatures up to 140°C were used. Internal vapour pressure in the wood could rise to about 20 kPa without checking. Maximal drying rates of 0.20 to 0.45% moisture content per minute are possible to obtain when drying above fiber saturation (fsp). Below fsp the feasible drying rates ranged from 0.10 to 0.20% moisture content per minute. Spruce dried approximately 1.6 times faster than pine. No conditioning of the wood was necessary since the wood was free of stresses. The wood was free of checks but colour changes occured in the interior of some specimens.

  • 3.
    Axelsson, B.O.M.
    Luleå tekniska universitet.
    Lateral cutting force during machining of wood due to momentary disturbances in the wood structure and degree of wear of the cutting tool1994In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 52, no 3, p. 198-204Article in journal (Refereed)
    Abstract [en]

    The paper presents a study of the effect of momentary disturbances due to variations in wood structure on the lateral cutting force. Density, shape and fibre-direction of the disturbances, and the degree of wear of the cutting tool are taken into consideration. The paper shows that high density gradients result in high lateral forces. The highest momentary lateral force noted has a value of approximately 40 N. The geometrical shape of the cutting tool in terms of degree of wear has a big impact on the lateral force. The work indicates a potential to increase the cutting performance by a more accurate supervision of the condition of the cutting tools.

  • 4.
    Axelsson, B.O.M.
    et al.
    Luleå tekniska universitet.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The use of gray scale images when evaluating disturbances in cutting force due to changes in wood structure and tool shape1991In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 49, no 12Article in journal (Refereed)
    Abstract [en]

    A method is presented for studying the effect of momentary disturbances due to variations in wood structure on the cutting force near the cutting edge. Force and density measurements are converted to a gray scale image. This method is very effective as regards the evaluation of experimental tests

  • 5.
    Axelsson, B.O.M.
    et al.
    Luleå tekniska universitet.
    Lundberg, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Studies of the main cutting force at and near a cutting edge1993In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 51, no 1, p. 43-48Article in journal (Refereed)
    Abstract [en]

    The present work is a study of how various parameters affect the cutting forces at, and near a cutting edge when cutting wood at full speed and with all cutting edges of the tool. Statistical methods from experimental results are used to develop a model

  • 6.
    Bekhta, Pavlo
    et al.
    Ukranian National Forestry University.
    Sedliacik, Jan
    Technical University in Zvolen.
    Jones, Dennis
    DJ Timber Consultancy Ltd.
    Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood2018In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, no 2, p. 549-562Article in journal (Refereed)
    Abstract [en]

    In this study, the physical and mechanical properties of plywood panels made from pre-compressed birch (Betula verrucosa Ehrh.) veneer were evaluated. Veneer sheets underwent short-term thermo-mechanical (STTM) compression at temperatures of 150 or 180 ⁰C and at pressures of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 or 3.5 MPa for a period of 1 minute before being adhesive applied and pressed into panels using phenol formaldehyde adhesive at 100 g/m2 spread rate; this was one third less than the adhesive spread used for the control panels (150 g/m2). The pressing pressure was 1.0 MPa that was almost half of the pressure used for the control panels (1.8 MPa); and pressing time was 3 min, also half of the pressing time used for the control panels (6 min). The results showed that surface roughness of compressed veneer, water absorption and thickness swelling of plywood panels made from compressed veneer were significantly improved. The shear strength values of plywood panels made from compressed birch veneer even with reduced adhesive spread were higher than those of plywood panels made from un-compressed veneer. The findings in this study indicated that compression of birch veneer would be considered as an alternative to produce more eco-friendly (owing to smaller adhesive spread) value-added material with enhanced properties.

  • 7.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Johansson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Skog, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Value optimized log rotation for strength graded boards using computed tomography2014In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 72, no 5, p. 635-642Article in journal (Refereed)
    Abstract [en]

    A possible application for an industrial computed tomography scanner in a sawmill is finding an optimal rotational position of logs with respect to knots and outer shape. Since a computed tomography scanner is a great investment, it is important to investigate potential profitability of such an investment for different production strategies. The objective of this study was to investigate the potential value increase of the sawn timber of Norway spruce (Picea abies (L.) Karst.) by rotating logs to their optimum position prior to sawing compared with sawing all logs in horns down position. The production strategy evaluated by log breakdown simulation in this case study was to produce strength graded timber of the center boards, while the side boards were appearance graded. This case study showed an average value increase with respect to the value of center boards, side boards and chips of 11 %.

  • 8.
    Blomberg, Jonas
    et al.
    Luleå tekniska universitet.
    Persson, Bengt
    Högskolan Dalarna.
    An algorithm for comparing density in CT-images taken before and after compression of Pinus sylvestris2005In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, no 1, p. 23-29Article in journal (Refereed)
    Abstract [en]

    Ten plain-sawn boards of Scots pine (Pinus sylvestris L.) were compressed semi-isostatically according to the CaLignum process in a Quintus press at 25°C and 140 MPa. X-ray computerised tomography images of the same cross-sections were captured before and after compression and compared using a transformation algorithm. In the algorithm the shape of compressed cross-sections were converted to the same shape as non-compressed using the density variation between pixels. Density after compression and the increase in density were analysed using PLS regression. The regressor variables described position in the cross-section and wood properties of each pixel. Heartwood and other resinous wood were less compressed than sapwood, particularly in boards with high resin content. Density also increased little close to the press table, especially in whorls with large knots. Higher original density gives lower degree of compression but still higher density after compression. © Springer-Verlag 2005

  • 9.
    Bomark, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hirche, Johannes
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Colour visualisation of real virtual timber using image quilting2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 6, p. 837-839Article in journal (Refereed)
    Abstract [en]

    When presenting images of wood obtained through x-ray computed tomography to an audience inexperienced in interpreting radiological images, explaining the correspondence between mass attenuation and features of wood could be time consuming and confusing. Realistically colourised attenuation images might be a suitable option in order to facilitate understanding of the images. Mass attenuation and colour of wood does not have a simple correlation, so naive grey-scale to colour conversion does not work. This paper describes how image quilting can be used to transfer colour information from a image pair where both mass attenuation and colour is known to a target mass attenuation image. An example of this method applied on scots pine shows that it is capable of retaining the major structures of wood, such as year rings and knots. The method could allow for easier understanding of simulation studies where logs scanned using x-ray computed tomography are virtually sawn.

  • 10.
    Butylina, Svetlana
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Mechanical Engineering, Lappeenranta University of Technology.
    Hyvärinen, Marko
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Kärki, Timo
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Weathering of wood-polypropylene composites containing pigments2012In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 70, no 5, p. 719-726Article in journal (Refereed)
    Abstract [en]

    Outdoor applications of composites have raised questions about their durability. In this study, the effects of outdoor weathering on the properties of wood-polypropylene composites with and without pigments were examined. The composites were placed outdoors for one year, and their colour changes were evaluated after 1, 3, 6, 9 and 12 months of weathering. The durability of the composites was assessed by testing flexural strength and density. Scanning electron microscopy was applied to evaluate the surface degradation of the composites. The weathering resulted in considerable colour fading of the composites. The composites containing darker colour pigments had better colour stability. After weathering, the general trend was a decrease of the flexural strength and density of the composites. The decrease in flexural strength was found to be lower for the composites having higher density.

  • 11.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Fujian Agriculture and Forestry University, Fuzhou, China.
    Wu, Zhenzeng
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Niu, Min
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Effect of Si-Al Molar Ratio on Microstructure and Mechanical Properties of Ultra-low Density Fiberboard2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, no 2, p. 151-160Article in journal (Refereed)
    Abstract [en]

    To clarify how the mechanical properties of ultra-low density fiberboards (ULDFs) affected by Si-Al molar ratios, they were prepared with different Si-Al molar ratios. Microstructure and mechanical properties of the ULDFs were tested using scanning electron microscope, energy dispersive spectroscopy, X-ray photoelectron spectrometer, Fourier transform infrared spectrometer, X-ray diffractometer, and microcomputer control electronic universal testing machine. The results showed that Si and Al component were uniformly distributed on the fibers’ surface and the bond of Si-O-C was formed. The different microstructures and relative densities were presented with different Si-Al molar ratios. The results of the modulus of elasticity (MOE), modulus of rupture (MOR) and internal bond strength (IB) were also significantly affected by different Si-Al molar ratios; and their maximum values of 20.78, 0.17, and 0.025MPa were obtained while Si-Al compounds with Si-Al molar ratio of 2:1 was added.

  • 12.
    Danvind, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    PLS prediction as a tool for modeling wood properties2002In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, no 2, p. 130-140Article in journal (Refereed)
    Abstract [en]

    During an earlier study, material responses of shrinkage and deformation during air-drying were measured on small wood specimens cut from the cross section of a Pinus radiata log. In this paper the analysis of the collected data and the modeling of studied responses were done using multivariate methods. A first model with all variables and all 104 observations was created. In this model there were observations that deviated from the rest and some of them were therefore excluded from further modeling. Also, weak variables and undesired variables were excluded from further modeling. After these exclusions, 77 observations of wood responses below fiber saturation point remained. The results showed good modeling of radial, tangential and volumetric shrinkage between 0-22% MC, with explained variance (R2) and predicted variance (Q2) at approximately 0.9, and moderate modeling of longitudinal shrinkage, R2 = 0.67 and Q2 = 0.65. It was also shown that longitudinal shrinkage has weak correlation to density-related variables in the studied wood. No model with good predictability of deformation was found. This study showed that PLS prediction modeling of shrinkage and deformation in studied wood samples was found to be an effective and easy-to-use tool for untangling relationships between variables and generating information from data.

  • 13.
    Ekevad, Mats
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cristovao, Luis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Geometry of kerf when curve sawing with a circular rip-saw2014In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 72, no 6, p. 809-814Article in journal (Refereed)
    Abstract [en]

    Rip-sawing following the curvature of a crooked log means advantages for yield. However, the possibility to saw in a narrow curve with a circular saw blade is limited because of the inherently flat geometry of circular saw blades. For a double arbour circular saw the situation is even more problematic because the two blades have a certain overlap and thus, the two arbours are not positioned in the same horizontal position. In this study, a theoretical geometrical study of the creation of a kerf with a single circular saw blade and with a double arbour circular saw with two saw blades was examined. Results for stiff saw blades show that the kerfs become in general curved and inclined (tilted) in the vertical direction and also that the width of the kerfs for double arbour saws becomes wider at the top and bottom of the cant than in the middle. Additionally, the sawn boards obtain varying thickness along their width because of the varying kerf width. A comparison with experimental thickness data from four test sawings at a sawmill indicates that the theoretical results are valid and that curve sawn boards become thinner than straight sawn boards.

  • 14.
    Eklund, Urban
    Luleå tekniska universitet.
    Influencing factors on sawing accuracy in a bandsawmill2000In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 58, no 1-2, p. 102-106Article in journal (Refereed)
    Abstract [en]

    The influence of the cutting height, the feed speed, the strain in the band and the cutting time for the band on the sawing accuracy has been investigated by fractional factorial analysis in a normal production situation at a sawmill in Sweden. Factorial analysis has proven to be a useful method when checking the situation at a sawmill as there are many factors that influence the sawing results. The findings in this investigation are: (a) the feed speed must be adapted to the actual cutting height to a higher degree than done today; (b) the working time for the band has some influence on the result but not to the great extent as expected; (c) the feeding equipment has probably a big influence on the sawing accuracy

  • 15.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berglund, Anders
    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.
    Validating a crosscutting simulation program based on computed tomography scanning of logs2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 2, p. 143-150Article in journal (Refereed)
    Abstract [en]

    Wood scanners and software for calculating crosscutting positions have been used in the wood industry for some years now. The scanners are used to detect biological and geometrical deviations on the sawn timber, which makes it possible to remove undesired defects using crosscut saws. Yield calculations for crosscutting have not been investigated to the same extent as sawing yield calculations for primary breakdown of logs, especially if the whole chain from log to end product is considered. The objective of this study was to validate the result of a computer program developed for simulating crosscutting of boards. The crosscut simulations were performed with respect to knot characteristics on Scots pine (Pinus sylvestris L.) board surfaces. Validating a crosscutting simulation program would mean that it can be used to investigate how raw material and customization of quality rules affect the yield in a wood production chain from log to crosscut end product. The validation showed that crosscutting yield for boards could be predicted with a root mean square error of 13 percentage points, and the technique can be used to identify unsuitable logs for a certain product at an early stage of production.

  • 16. Grundberg, Stig
    et al.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Measuring active wood fracture surfaces1993In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 51, no 1, p. 49-54Article in journal (Refereed)
    Abstract [en]

    This report describes a measurement method, based on image processing, for calculating the proportion of active wood fractures in a sheet of particle board that has been pulled apart. This method gives an indirect measurement of the effectiveness of the glue in a particle board. The basic procedure is to separate different surfaces on both sides of the tensile fracture. The separation of the glue covered surfaces from wood surfaces has been enhanced by a development process. The separated surfaces for each side, represented in the form of a binary image, are added, and a proportion of the surface with coinciding wood surfaces represents the proportion of wood fractures. The error analysis covers the randomly obtained coinciding surfaces.

  • 17. Grönlund, Ulla
    Quality variations in the chain log-board-blank1994In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 52, no 1, p. 57-62Article in journal (Refereed)
    Abstract [en]

    To achieve a high economic yield in the wood industry it is important to control the grading procedures and to know the quality distribution in different steps. Scots pine (Pinus sylvestris) timber from Sweden has been compared regarding quality variations in the chain log-board-blank caused by biological properties and subjective grading procedures. This study describes the quality distributions in the treatment of trees from harvesting throughout sawing and to the user's judgements, the correlation between the grading procedures in various steps, and the yield in all classes based upon the customer's opinion. The results emphasise that current classification system is very hazardous and seems not be in concordance with the customers' demand. The subjective and visual grading procedures are not sufficiently effective to predict the properties. Three main needs must be satisfied in order to reduce the costs for poor quality; knowledge about the biological variations, new equipment for grading and knowledge about the customers' needs and behaviours

  • 18. Grönlund, Ulla
    et al.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Relations between wood properties and manual grading: an approach based on multivariate analysis1995In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, no 6, p. 413-420Article in journal (Refereed)
    Abstract [en]

    Pinus sylvestris ) boards from Sweden have been scanned on all four sides. The output variables together with additional variables describing e.g. geographic areas and manual classification class are analysed by using multivariate statistical methods. The purpose was to study if the manual grading procedure of boards/blanks are in conformity with automatically measured properties and if there is any single property that carries more information than others. The results show that most of the original variables are uncorrelated and therefore it is impossible to reduce and simplify the grading procedure by e.g. measuring only a few characteristics. The study also shows the weakness of the objective grading procedure describing only the amount of characteristics.

  • 19.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Multivariate prediction of wood surface features using an imaging spectrograph1997In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 55, no 6, p. 377-382Article in journal (Refereed)
    Abstract [en]

    Picea abies , Pinus sylvestris), is reported, showing verified 92-94% correct classification. It is shown that compression wood classification could be reduced to an uncomplicated linear model using just a few spectral components where the most important one is around the limit for visible light going to the Ultraviolet spectra. This almost univariate behaviour for the model is not the common behaviour for other wood surface features

  • 20.
    Hagman, Olle
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, S.A.
    Swedish Institute for Wood Technology Research.
    Classification of scots pine ( Pinus sylvestris ) knots in density images from CT scanned logs1995In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, no 1, p. 75-81Article in journal (Refereed)
    Abstract [en]

    This study was carried out to test methods for separating knots from clearwood in a digital image stack when scanning for internal defects with a medical CT-scanner. Scots pine knots, represented by its tangential surface density image extracted from a CT-image stack, have been classified by two different methods showing equal results. The knots are classified in four knot types by an Artificial Back-propagation Neural Network (ANN) and a Partial Least Squares Modelling with Latent Variables (PLS) model. The classification precision of aim of four different knot types, is between 85% and 97%. The results indicate that both methods may be useful tools in order to describe and classify knots in concentric surfaces around the pith in CT-images and thereby extract parametrical models from CT raw data image stacks. A simplified classification model has been obtained, by analysing the learning patterns in both the ANN and PLS model, that classify knots and transform density related data to segmented and classified parametrical descriptions.

  • 21. Johansson, Dennis
    et al.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The potential of colour measurement for strength prediction of thermally treated wood2006In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 64, no 2, p. 104-110Article in journal (Refereed)
    Abstract [en]

    This paper investigates the effects of thermal treatment of birch with respect to colour and strength. Birch wood was treated at 175 °C and 200 °C for 0 h, 1 h, 3 h and 10 h. In bending-strength experiments, treatment was also performed at 185 °C for 2 h. Both static bending strength and impact bending strength were investigated using multivariate statistics (PLS) for correlation to process parameters, density, EMC, position in board, modulus of elasticity (only in static bending), colour and dimensions of samples. In static bending, two PLS models were designed, one based on process parameters and the other based on colour and EMC. From these models it was concluded that colour is not a useful parameter for prediction of strength. In impacted bending, the correlation was too small to give useful results. One test of static bending strength with matched samples was performed, and it showed a strength reduction of 43% when treatment was conducted at 200 °C for 3 h. Measurement of colour homogeneity of the treated boards showed that the colour is not homogeneous.

  • 22.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stehn, Lars
    Plug shear failure in nailed timber connections: load distribution and failure initiation2004In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 62, no 6, p. 455-464Article in journal (Refereed)
    Abstract [en]

    Brittle failures in mechanical timber joints should be avoided, because this often results in low capacity and brittle failure of the structure. Nailed joints experience three ultimate failure modes: embedding, splitting or plug stear failure. To avoid plug shear failure, short and wide joints are preferred, limiting the number of fasteners in line with the load and grain direction. Plug shear failure was examined in short-term experiments on nailed steel-to-timber joints in glulam loaded in tension parallel to the grain with five different joint geometries. The aim of the study was to examine if the fastener group layout can be adjusted to avoid plug shear failure and to gain an insight into the causes of failure initiation. Using spring models, it is shown that the load distribution creates pronounced stresses at the last nail in the joint, which probably initiates the plug shear failure. Test results are compared with prediction models found in the literature. It was found that fasteners placed in groups can be a successful way of reducing the risk of plug shear failure. The failure is probably initiated at the nail farthest from the free end, where tensile stresses perpendicular to grain occur.

  • 23.
    Jonoobi, Mehdi
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Wood and Paper Sciences and Technology, Faculty of Natural ResourcesUniversity of Tehran.
    Ghorbani, Maryam
    Faculty of Natural Resources, Sari University of Agricultural Sciences and Natural Resources, Sari .
    Azarhazin, Ali
    Faculty of Natural Resources, Sari University of Agricultural Sciences and Natural Resources, Sari .
    Hosseinabadi, Hamid Zarea
    Department of Wood and Paper Sciences and Technology, Faculty of Natural Resources, University of Tehran.
    Effect of surface modification of fibers on the medium density fiberboard properties2018In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, no 2, p. 517-524Article in journal (Refereed)
    Abstract [en]

    Surface modification of mixed hardwoods fibers by sodium hydroxide (NaOH) was conducted to investigate the effect of chemical treatment on the fiber properties along with physico-mechanical characteristics of the medium density fiberboard (MDF). The results indicated that the NaOH treatments can dissolve a portion of hemicelluloses and almost all amount of extractives from the fibers, but it was not strong enough to remove the lignin thoroughly. The FTIR results illustrated that chemical changes can occur during the various NaOH treatments of the fibers. X-ray diffraction analysis revealed that the crystallinity of the studied fibers increased after the alkaline treatment. Investigation of mechanical properties of the MDF showed that modulus of rupture and internal bond strength of the treated samples were decreased compared to the control ones. In addition, water absorption and thickness swelling of treated boards were higher than that of untreated samples. This study indicated that the physico-mechanical properties of the boards were negatively affected by the NaOH treatment.

  • 24.
    Källander, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Influence of sample size during thermal modification on resulting equilibrium moisture content of Scots pine2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736XArticle in journal (Refereed)
  • 25.
    Källander, Björn
    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.
    Influence of sample size during industrial and laboratory thermal modification on mass loss and impact bending strength of Scots pine2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736XArticle in journal (Refereed)
  • 26.
    Lindgren, Owe
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Davis, J.
    Monash University, Melbourne, VIC.
    Wells, P.
    Monash University, Melbourne, VIC.
    Shadbolt, P.
    Monash University, Melbourne, VIC.
    Non-destructive wood density distribution measurements using computed tomography1991In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 50, no 7-8, p. 295-299Article in journal (Refereed)
    Abstract [en]

    Two computed tomography scanners have been used to acquire density profiles from five wooden test pieces. These test pieces had annual growth ring widths varying between about 0.6 mm and 3.5 mm. The two scanners employed were a medical scanner, a GE 9800 Quick scan system, and a purpose built microscanner constructed around a Rigaku D-Max II diffractometer. The results demonstrated that the annual growth rings could be resolved and density measurements could be reliably determined using the microscanner when the annual growth rings were about 0.9 mm or greater in width. The medical scanner could not satisfactorily measure density in carlywood or latewood resions even in samples where the annual growth ring width was of the order of 3.5 mm. A small difference in density measurements could be observed between the two scanners for the same specimens. The difference is attributed to calibration differences, the reconstruction algorithms used and the different geometries of the two systems; particularly in relation to the detector apertures. The larger detector size in the medical system results in too high or too low density values in the carlywood or the latewood respectively due to spatial averaging. However, the medical scanner provides satisfactory density accuracy in specimens where the density is very uniform or as long as measured areas include both carlywood and latewood. An accuracy of ±2-6 kg/m3 at 95% confidence level can then be expected.

  • 27.
    Lundberg, Staffan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Porankiewicz, B.
    Agriculture University of Pouznan.
    Erratum: Studies of non-contact methods for roughness measurements on wood surfaces1996In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 54, p. 72-Article in journal (Refereed)
  • 28.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Steam conditioning after low temperature drying1994In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 52, no 2, p. 77-82Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to investigate the response of saturated water vapour steaming on boards from Scots pine and Norway spruce. Steaming treatment of the predried boards were done in a laboratory chamber equipped with a 1.5 kW electric water boiler. The experiments were performed mainly at 100°C in saturated steam and the relation between temperature and moisture pickup as well as stress relaxation was studied. The results showed that steaming is a very efficient process to relax stress and equalise moisture gradients in boards. The gain of time is considerable; steaming takes only about 10% of traditional conditioning time at lower temperatures. The temperature rise is correlated to moisture pickup from surface condensation resulting in the possibility of estimating the increase of moisture content during steaming from measurements of temperature.

  • 29.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The effect of drying and conditioning on the cupping of boards from Pinus sylvestris and Picea abies1993In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 51, no 4, p. 296-Article in journal (Refereed)
  • 30.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Evaluation of knot parameters measured automatically in CT-images of Norway spruce (Picea abies (L.) Karst.)2000In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 58, no 5, p. 375-379Article in journal (Refereed)
    Abstract [en]

    Knot parameters measured automatically in CT-images of Norway spruce have been evaluated on logs from four plots in the Norway spruce stem bank. The evaluation was made through comparisons between measurements on real centre boards and measurements on reconstructed boards. The reconstructions were based on the automatically measured parameter descriptions of knots and log shape and on simulated sawing. The diameter of knots was measured with a mean error of -2 mm and a standard deviation of 3 mm. It was shown that the reconstructed centre boards were well in accordance with the real centre boards in terms of position, number, size and type of knots. The exception is knot type for small knots in large butt logs.

  • 31.
    Oja, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Temnerud, E.
    Sveriges Lantbruksuniversitet.
    The appearance of resin pockets in CT-images of Norway spruce (Picea abies (L.) Karst.)1999In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 57, no 5, p. 400-406Article in journal (Refereed)
    Abstract [en]

    The appearance of resin pockets in CT-images of Norway spruce (Picea abies (L.) Karst.) was studied. The study also includes a comparison between measured and calculated CT-numbers of Norway spruce resin and wood. It was found that it should be possible to create algorithms that automatically detect large resin pockets in CT-images of Norway spruce. Compared to resin pockets in heartwood, resin pockets in green sapwood are more difficult to detect due to the high density of the surrounding wood. The study also showed that the correlation between measured and calculated CT-numbers was high and that it is possible to use the same function for conversion between CT-number and density for both green wood and resin.

  • 32.
    Pang, Shusheng
    et al.
    Wood Processing Division, New Zealand Forest Research Institute.
    Wiberg, Per
    Luleå tekniska universitet.
    Model predicted and CT scanned moisture distribution in a Pinus radiata board during drying1998In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 56, no 1, p. 9-14Article in journal (Refereed)
    Abstract [en]

    Pinus radiata sapwood boards of 100 × 40 × 1200 mm were dried in a tube dryer at Luleå University, using a computer tomography (CT) scanner to scan the wood during drying. The CT-scanned wet wood density can illustrate moisture distribution within wood when the wood basic density profile is known. The CT-scanned results were used to validate a 2-D single board drying model developed at the New Zealand Forest Research Institute. The validation has shown that the model is not only capable of predicting the average moisture content but also moisture content gradients in board thickness, width and within growth rings. To investigate the effects of sawing pattern and intrinsic wood properties on drying, the input parameters for the model include within-ring variations of wood density, green moisture content and wood permeability. The model can assist in understanding the causes of some drying defects and has potential for the development of drying schedules.

  • 33.
    Pang, Shusheng
    et al.
    New Zealand Forest Research Institute.
    Wiberg, Pär
    Luleå tekniska universitet.
    Model predicted and CT scanned moisture distribution in a Pinus radiata board during drying1999In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 57, no 1, p. 79-80Article in journal (Other academic)
  • 34.
    Parida, Gabriela
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Fragiacomo, Massimo
    Department of Architecture, Design and Urban Planning, Faculty of Architecture, University of Sassari.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Prefabricated timber walls anchored with glued-in rod connections: racking tests and preliminary design2013In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, no 5, p. 635-646Article in journal (Refereed)
    Abstract [en]

    A new beam and post system for multi-storey timber buildings is being developed in Sweden. The stabilising walls are constructed from two Kerto-Q LVL boards glued and screwed onto a glulam skeleton. The walls are prefabricated off-site and connected to the foundation using either glued-in rods or nail plates.An introductory racking test of a full scale stabilising wall anchored with glued-in rods was performed. The paper presents the results of the experimental test and evaluates them using the transformed section method. To evaluate the strength of the glued-in rods, two newly proposed models were employed. A theoretical examination was conducted to investigate the role of the sheathing in the racking load carrying capacity. An analysis was also performed to quantify the contribution of the axial force on the racking capacity of the wall, which was conservatively ignored in the experiment. Generally, the stabilising wall panels tested in this experimental programme showed high strength and stiffness. The anchoring joints with glued-in rods demonstrated a high load-carrying capacity, however, with a large scatter and a brittle failure mode characterized by pull-out from the timber member. The transformed section method is recommended as a method for designing stabilising walls anchored with glued-in rods.

  • 35. Sandberg, Dick
    Distortion and visible crack formation in green and seasoned timber: Influence of annual ring orientation in the cross section2005In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, no 1, p. 11-18Article in journal (Refereed)
    Abstract [en]

    This work describes distortion (bow, crook, twist, cup) and the formation of visible cracks in green and seasoned timber of Scots pine and Norway spruce. Distortion and crack formation have been evaluated according to the original location in the cross section of the log. The purpose is to describe differences in distortion and crack formation between sawn timber taken from star sawing and from traditional sawing patterns. Bow and crook develop in the green timber immediately after sawing as a result of growth stress release. Drying and conditioning in general lead to a marginal increase in bow, but crook may show a large percentage increase depending on the location of the wood in the cross section. Twist and cup do not occur directly after sawing, but arise during seasoning of the wood. In sawn wood, the juvenile wood has a major influence on the twist. This means that timber sawn close to the pith shows a greater twist than timber sawn away from the pith. This is a consequence of the fibre orientation in this timber. Cupping increases with decreasing radius of curvature of the annual rings in the cross section of the timber. Cracks occur in timber before seasoning. The pattern of crack formation is the same in both pine and spruce; timber sawn close to the pith or with pith enclosed exhibits a considerably larger number of visible cracks than timber sawn away from the pith. Cracks occur mainly on surfaces orientated to the pith, a fact that becomes clearer when timber is observed close to the pith. Seasoned star-sawn timber with a rectangular cross section has bow and crook of the same extent as or less than that of timber sawn according to traditional sawing patterns. Seasoned star-sawn timber with a triangular cross section has high bow, but the crook is low. Star-sawn timber does not show any cup and has a good shape stability according to the geometrical shape in the cross section. It also has a very small twist and shows very few visible cracks after seasoning

  • 36.
    Sandberg, Dick
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Influence of pith and juvenile wood on proportion of cracks in sawn timber when kiln dried and exposed to wetting cycles.1996In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 54, no 3, p. 152-Article in journal (Refereed)
  • 37. Sandberg, Dick
    Radially sawn timber - the Primwood Method for improved properties2005In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, no 2, p. 94-101Article in journal (Refereed)
    Abstract [en]

    A new manufacturing system, the PrimWood Method, has been proposed to improve the utilization of wood. A basic concept within this method is the sawing pattern called star-sawing, which produces timber with both rectangular and triangular cross sections. This method facilitates an efficient production of radially sawn timber with vertical annual rings, without juvenile wood. The sawn timber produced in the PrimWood Method is used to produce high quality, knot-free solid wood panels with vertical annual rings. In this process, part of the timber is finger-jointed to form knot-free lengths which are glued together into a block. This block can then be divided according to thickness into thinner panels with vertical annual rings. The PrimWood Method has been tested in an industrial plant. The manufacturing system was designed for a sawing capacity of about 30,000 m3 logs, which corresponds to 16,800 m 3 of star-sawn timber per shift per annum. The production of solid wood panel was then designed to give a volume of 5,800 m3 per annum.

  • 38.
    Sandberg, Dick
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Radially sawn timber: Star-sawing - a new method for producing timber with vertical annual rings1996In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 54, no 3, p. 145-151Article in journal (Refereed)
    Abstract [sv]

    I detta arbete presenteras en ny sönderdelningsmetod för att framställa märgfritt virke med stående års¬ringar och utan juvenil ved. Metoden som benämns stjärnsågning ger två olika for¬mer på det utsågade virket, dels konventionellt virke med rektangulärt tvärsnitt, dels virke med triangulärt tvärsnitt. Volymutbytet för stjärnsågning har bestämts med hjälp av simulerad sönderdelning och genom provsågningar. Resultaten visar att stjärnsågning är bäst lämpad för stockar med toppdiameter över 200 millimeter. Då erhålls både högt volymutbyte och lämpliga dimensioner på det utsågade virket. Volymutbytet av virke med stående årsringar vid stjärn¬sågning är omkring 0,70 beräknat med avseende på toppcylindervolymen under bark.

  • 39.
    Sandberg, Dick
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Radially sawn timber: The influence of annual ring orientation on crack formation and deformation in water soaked pine (Pinus silvstris L) and spruce (Picea abies Karst) timber1997In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 55, no 3, p. 175-182Article in journal (Refereed)
  • 40.
    Sandberg, Dick
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    The influence of annual ring orientation on strength and dimensional changes during moisture variation in finger joints.1997In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 55, no 1, p. 50-Article in journal (Refereed)
  • 41.
    Sandberg, Dick
    et al.
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Holmberg, Hans
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Radially sawn timber: Gluing of star-sawn triangular profiles into form-stable products with vertical annual rings1998In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 56, no 3, p. 171-177Article in journal (Refereed)
    Abstract [en]

    A method is presented for the gluing of star-sawn triangular profiles of pine (Pinus silvestris L.) into form-stable wood products with vertical annual rings. The triangular profiles are free from pith and from most of the juvenile wood.The method is based on dried and conditioned triangular profiles. Undesired defects are removed and the wood is finger-jointed into long lengths. In the finger-jointing, consideration is given to the appearance and annual ring orientation of the jointed materials. After the jointing, the triangular profiles are planed and glued into rectangular blocks with vertical annual rings. These blocks can then e.g. be used as construction beams or be sawn up into solid wood panels.A pilot plant has been built for the manufacture of knot-free solid wood panels based on the proposed method. Results show a total volume yield of 53.8%. Three critical production stages can be distinguished: removal of knots and defects, planing, and division of blocks into boards. These three operations are together responsible for more than 93% of the total losses in the manufacture.The removal of knots and defects meant a volume loss of 12.8%. 13% of the manufactured units were 2.1 m long without finger-jointing and free from knots and other defects. The average length of the remaining pieces used for finger-jointed units was 0.41 m.

  • 42.
    Sandberg, Dick
    et al.
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Holmberg, Hans
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Radially sawn timber: Knots - number, type and size in star-sawn triangular profiles of pine (Pinus silvestris L) and spruce (Picea abies Karst)1996In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 54, no 6, p. 369-376Article in journal (Refereed)
    Abstract [sv]

    I detta arbete kartHiggs kvistars utseende oeh antal i stjamsagad trekantprofil av furu (Pinus silvestris L) och gran (Picea abies Karst). Tyngdpunkten ar lagd pA att ta fram volymutbytet av amnen med ett visst kvistutseende samt slorleken pA fiberstornmgarna kring kvistama och hur de paverkar utbytet. Provmaterialet har tagits fran tre omraden i Sverige och utgors av rotstoekar fran furu samt fran normal oeh frodvuxen gran.Resultaten visar att en stor andel av de kvistar som Aterfinns i trekantprofilema fran rotstoekar ar oacceptabla vid vidareforadling av virket och mAste kapas bort. Man kan konstatera att det finns fa friska kvistar.Vid framkapning av kvistfria amnen fAr man en volymminskning med i medeltal 8 oeh 21 procentenheter for furu respektive gran, beraknat med avseende pa den ursprungliga profilvolymen. Kapar man dessutom bort fiberstorningen kring kvistama far man darutover en volymminskning med 5 procentenheter for furu och 6 proeentenheter for gran. De framtagna amnena har ett brett spektrum av langder mellan 2 och 500 centimeter for furu och mellan 2 och 400 eentimeter for gran.

  • 43.
    Sandberg, Dick
    et al.
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Stehr, Micael
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Bending strength of I-beams with webs of wood-fibre board and flanges of star-sawn triangular profiles1997In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 55, no 5, p. 292-Article in journal (Refereed)
  • 44.
    Scheepers, Gerhard
    et al.
    University of Stellenbosch.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Rypstra, Tim
    University of Stellenbosch.
    Liquid water flow in Pinus radiata during drying2007In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 65, no 4, p. 275-283Article in journal (Refereed)
    Abstract [en]

    End-sealed 60×60×250 mm3 Pinus radiata pieces were dried at 65/37 °C (dry bulb/wet bulb temperature) and 4 ms-1 air speed to study various drying phenomena above fibre saturation point. While drying, an X-ray computed tomography (CT) scanner captured a cross-cut density image every ten minutes. The density data was used to determine moisture content, rate of moisture loss from the core, wetline (boundary line of the free water region) depth and cross-cut area of the wood pieces. Repeating patterns were observed, which indicated that the cavity-size distribution of the wood pieces dictated fluctuations in the rate of moisture loss from the core and cross-cut area shrinkage during drying in the free water phase. It is hypothesised that, while drying an interconnected capillary network in the free water phase, the largest meniscus penetrates a wood piece through the largest cavities, thus also allowing air into the capillary network. The largest meniscus would always get smaller as it penetrates the wood piece until it is not the largest meniscus in the network anymore. Then the new largest meniscus would start penetrating the capillary network, etc. The largest meniscus would also determine the liquid tension in the capillary network. When the largest meniscus gets small enough, and the liquid tension strong enough, deformation and collapse of the remaining liquid-filled cavities can occur. A large liquid-filled interconnected capillary network would eventually fragment into a number of smaller liquid-filled interconnected networks, at which point a receding wetline could be observed.

  • 45.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    High-temperature drying of Scots pine: A comparison between HT- and LT-drying1995In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, no 1, p. 95-99Article in journal (Refereed)
    Abstract [en]

    In order to study the influence of high temperature on wood properties, boards from Scots pine were dried at three different schedules, two high-temperature-schedules (HT) and one at low temperature (LT). Strength properties as hardness, cleavage- and shear-strength were determined and sorption/desorption behaviour were studied. Material was analysed concerning carbohydrate and extractive content and mould growth test at wooden surfaces. Results showed a significant influence of temperature on decreasing shear strength and equilibrium moisture content (EMC) in sorption/desorption tests. Sorption/desorption tests resulted in up to 2.4% lower EMC for HT dried material at the same climate compared with LT-dried and the hysteresis effect seems to be more pronounced in HT-dried material. Mould growth test showed an inhibiting effect of HT-drying on mould susceptibility at wooden surfaces. Carbohydrate analysis revealed a lower content of hemicelluloses in HT-dried boards which indicates a decomposition of the hemicelluloses explaining the decrease in shear strength and hygroskopic moisture uptake seen in the HT dried boards.

  • 46.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The effect of drying temperature on subsequent moisture and dimensional changes for Scots pine and Norway spruce2000In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 58, no 5, p. 353-Article in journal (Refereed)
    Abstract [en]

    The effect of three different drying procedures on moisture and dimensional changes for Scot pine and Norway spruce during subsequent climate changes was studied. It was found that no difference exists between pine and spruce in maximal radial or tangential shrinkage for the reference material. High temperature (HT) dried spruce showed higher maximal shrinkage at 0% moisture content compared with HT dried pine.

  • 47. Sundqvist, Bror
    Color response of Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula pubescens) subjected to heat treatment in capillary phase2002In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, no 2, p. 106-114Article in journal (Refereed)
    Abstract [en]

    Clearwood of Scots pine, Norway spruce, and birch was subjected to heat treatment while capillary water was kept in the wood. The treatments were performed on initially green wood from 65 °C to 95 °C from 0 to 6 days, followed by drying at 35 °C for 2 days. Color measurements, CIEL*C*h color space, were made on dry planed samples using a photoelectric colorimeter. Treatment time was more important than temperature for birch sapwood regarding the color responses, while time and temperature were of similar importance for pine and spruce. Birch sapwood became much redder and darker compared with pine and spruce. The darkening accelerated generally when treatment temperature exceeded approximately 80 °C. Pine and spruce showed generally similar color responses, untreated and treated, except for pine heartwood untreated, which showed a more saturated color. Pine treated at 65 °C and 80 °C showed red-yellow shift and yellow-red shift for sap- and heartwood respectively, as time elapsed. The color homogeneity was less for birch sapwood than for pine and spruce, and the homogeneity was generally indicated to decrease with increasing treatment temperature.

  • 48. Sundqvist, Bror
    et al.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The influence of wood polymers and extractives on wood colour induced by hydrothermal treatment2002In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, no 5, p. 375-376Article in journal (Refereed)
    Abstract [en]

    A method to evaluate the influence of wood polymers and extractives on the color of wood subjected to hydrothermal treatment was proposed. As such, the technique used was extraction and color measurements. It was found that both degradation products from wood polymers and extractive compounds were indicated to be participating in the color formation of wood subjected to hydrothermal treatment.

  • 49.
    Temnerud, E.
    et al.
    Swedish University of Agricultural Sciences.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A preliminary study on unbiased volume estimation of resin pockets using stereology to interpret CT-scanned images from one spruce log1998In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 56, no 3, p. 193-200Article in journal (Refereed)
    Abstract [en]

    Stereological methods for the volume estimation of resin pockets in saw logs were studied using computed tomography (CT) and image analysis. The Cavalieri theorem was applied for transverse sections and the Pappus theorem was applied for longitudinal radial sections. Stereology applied on wood has to consider both the linear orientation of tracheids and rays, and the circular, lamellar oriented structure of annual rings. The precision of the estimates is illustrated with varying step length between sections, i.e. varying sample size and sampling intensity. To estimate the volume of resin pockets in one log with a coefficient of error of less than 10% requires a step length of 80umm between transverse sections or ten radial longitudinal sections 18 degrees apart. Here, the resolution of 1.37u2u1.37u2u5umm overestimated the true volume of resin pockets. Large resin pockets can be detected, whereas detection of small resin pockets, which involved differentiation between resin pockets and compression wood, was difficult with the CT-scanner. This study proves that implementation of stereology on wood can be a good tool for quantitative analysis of resin pockets, which also means that the methods are suited for effective quality control of resin pockets in sawn timber

  • 50.
    Vasco, Diego A.
    et al.
    Departamento de Ingeniería Mecánica, Universidad de Santiago de Chile, Santiago .
    Salinas-Lira, Carlos
    Departamento de Ingeniería Mecánica, Universidad del Bío-Bío, Concepción .
    Barra-Reyes, Ignacio
    Departamento de Ingeniería Mecánica, Universidad del Bío-Bío, Concepción .
    Elustondo, Diego M.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Kinematic characterization of the pressure-dependent PCM impregnation process for radiata pine wood samples2018In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, no 5, p. 1461-1469Article in journal (Refereed)
    Abstract [en]

    This paper reports on the properties of Pinus radiata wood impregnated with an organic phase change material (O-PCM). The tests are aimed at characterizing the kinetics of impregnation (rates, flows, and fronts) and the thermophysical properties (thermal conductivity and specific heat). In particular, a paraffin type O-PCM (octadecane) is used to impregnate dry radiata pine wood in the tangential flow direction at four manometric pressures (0, 1, 2, and 3 bar) and constant temperature of 50 °C. The wood is sapwood from 12-year old P. radiata growing in the Bío-Bío region and dimensioned according to Chilean standard for treated wood sample extraction. The results show that it is viable to impregnate P. radiata wood with O-PCM to improve its thermophysical properties with the purpose of passive conditioning.

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