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  • 51.
    Hagman, Olle
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Åstrand, Erik
    Linköpings universitet.
    Österberg, Mats
    Linköpings universitet.
    Åström, Anders
    Linköpings universitet.
    Near-sensor real time spectral time classification for industrial applications1995In: Theory and applications of image analysis II: Selected papers from the 9th Scandinavian Conference on Image Analysis / [ed] Gunilla Borgefors, Singapore: World Scientific and Engineering Academy and Society, 1995, p. 355-Conference paper (Refereed)
  • 52.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    Lundgren, Nils
    Hagman, Olle
    Finite element modeling (FEM) simulation of interactions between wood and microwaves2006In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 52, no 5, p. 406-410Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to use finite element modeling (FEM) as a tool to analyze microwave scattering in wood and to verify the model by measurements with a microwave scanner. A medical computed tomography scanner was used to measure distribution of density and moisture content in a piece of Scots pine (Pinus sylvestris). Dielectric properties were calculated from measured values for cross sections from the piece and used in the model. Images describing the distribution of the electric field and phase shift were obtained from the FEM simulation. The model was verified by measurements with a scanner based on a microwave sensor. The results show that simulated values correspond well to measured values. Furthermore, discontinuities in the material caused scattering in both the measured and the simulated values. The greater the discontinuity in the material, the greater was the need for computational power in the simulation.

  • 53.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundgren, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    Hagman, Olle
    FEM simulation of heating wood in an industrial microwave applicator2005In: 10th International Conference on Microwave and High Frequency Heating : Modena, Italy, September 12 - 15, 2005 / [ed] Cristina Leonelli, 2005Conference paper (Refereed)
  • 54.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundgren, Nils
    Antti, Lena
    Hagman, Olle
    Microwave penetration in wood using imaging sensor2005In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 38, no 1, p. 15-20Article in journal (Refereed)
    Abstract [en]

    It is possible to determine properties of wood using microwave scanning techniques. The purpose of this study was to verify the measured values from a microwave imaging sensor. Attenuation and phase shift of an electromagnetic wave transmitted through birch wood were measured and compared with theoretical calculated values. A test piece with varying thickness was measured with a scanner based on a microwave sensor (Satimo 9.375GHz) at different temperatures and moisture contents. The density distribution of the test piece was determined by computer tomography scanning. The result showed good correspondence between measured and theoretical values. The proportion of noise was higher at low moisture content due to lower attenuation. There is more noise in attenuation measurement than in measurement of phase shift. A reason for this could be that wood is an inhomogeneous material in which reflections and scattering affect attenuation more than phase shift. The microwave scanner has to be calibrated to a known dielectric to quantify the error in the measurement

  • 55.
    Johansson, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pahlberg, Tobias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fast visual recognition of Scots pine boards using template matching2015In: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 118, p. 85-91Article in journal (Refereed)
    Abstract [en]

    This paper describes how the image processing technique known as template matching performs when used to recognize boards of Scots pine (Pinus sylvestris L.). Recognition of boards enables tracking of individual boards through an industrial process, which is vital for process optimization.A dataset of 886 Scots pine board images were used as a database to match against. The proposed board recognition method was evaluated by rescanning 44 of the boards and matching these to the larger dataset. Three different template matching algorithms have been investigated while reducing the pixel densities of the board images (downsampling the images). Furthermore, the effect of variations in board length has been tested and the computational speed of the recognition with respect to the database size has been measured. Tests were conducted using the open source software package OpenCV due to its highly optimized code which is essential for applications with high production speed.The conducted tests resulted in recognition rates above 99% for board lengths down to 1 m and pixel densities down to 0.06 pixels/mm. This study concluded that template matching is a good choice for recognition of wooden board surfaces.

  • 56.
    Johansson, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pahlberg, Tobias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Recognition of Sawn Timber using Template Matching2015Conference paper (Refereed)
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  • 57. Johansson, J.
    et al.
    Hagman, Olle
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting moisture content and density of Scots pine by microwave scanning of sawn timber2003In: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 41, no 1-3, p. 85-90Article in journal (Refereed)
    Abstract [en]

    Non-destructive testing of wood for prediction of strength is significantly influenced by wood density and moisture content. A sensor capable of measuring both density and moisture content would be a good tool to aid in predicting the strength of sawn timber. This study was carried out to investigate the possibility of calibrating a prediction model for the moisture content and density of Scots pine (Pinus sylvestris) using microwave sensors. The material was initially at green moisture content, and thereafter dried in several steps to zero moisture content. At each step all the samples were weighted, scanned with a microwave camera (Satimo 9.4 GHz) and CT scanned with a medical CT scanner (Siemens Somatom AR.T.). The output variables from the microwave camera were used as predictors, and CT images correlated with known moisture content were used as response variables. Multivariate models to predict moisture content and density were calibrated using partial least squares (PLS) regression. The result shows that it is possible to predict both moisture content and density with very high accuracy using microwave sensors

  • 58.
    Johansson, Jan
    et al.
    Luleå tekniska universitet.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fjellner, Bengt-Arne
    Predicting moisture content and density distribution of Scots pine by microwave scanning of sawn timber2003In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 49, no 4, p. 312-316Article in journal (Refereed)
    Abstract [en]

    This study was carried out to investigate the possibility of calibrating a prediction model for the moisture content and density distribution of Scots pine (Pinus sylvestris) using microwave sensors. The material was initially of green moisture content and was thereafter dried in several steps to zero moisture content. At each step, all the pieces were weighed, scanned with a microwave sensor (Satimo 9,4 GHz), and computed tomography (CT)-scanned with a medical CT scanner (Siemens Somatom AR.T.). The output variables from the microwave sensor were used as predictors, and CT images that correlated with known moisture content were used as response variables. Multivariate models to predict average moisture content and density were calibrated using the partial least squares (PLS) regression. The models for average moisture content and density were applied at the pixel level, and the distribution was visualized. The results show that it is possible to predict both moisture content distribution and density distribution with high accuracy using microwave sensors.

  • 59.
    Lindgren, Owe
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, AndersHagman, Olle
    Proceedings from the 3rd International Seminar/Workshop on Scanning Technology and Image Processing on Wood: Skellefteå, Sweden, August 17-19, 19981998Collection (editor) (Other academic)
  • 60. Lundgren, Nils
    et al.
    Brännström, Mattias
    Hagman, Olle
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting the strength of Norway spruce by microwave scanning: a comparison with other scanning techniques2007In: Wood and Fiber Science, ISSN 0735-6161, Vol. 39, no 1, p. 167-172Article in journal (Refereed)
    Abstract [en]

    In this study, 90 boards of Norway spruce (Picea abies (L.) Karst.) sized 48 x 148 mm in cross-section, have been examined using different scanning and measurement techniques. All of the boards originated from a sawmill located in southern Finland. Planar X-ray scanning, microwave scanning, and grain-angle measurement have been performed. In addition, strength and elastic properties were assessed for eachpiece by four point bending. The purpose of the study was to relate the potential of microwave scanning compared to other, industrially available techniques and to explain the physiological background of the microwave responses. The results show that the microwave signal, after transmission through wood, contains information about the bending strength and the modulus of elasticity. The correlation to densityis a key factor. Annual ring width was also found to be correlated both to microwave measurements and strength properties.

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  • 61.
    Lundgren, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Johansson, Jan
    Luleå tekniska universitet.
    Calibration for frozen/non-frozen conditions when predicting moisture content and density distribution of wood by microwave scanning of sawn timber2004In: Forest Products Society 58th Annual meeting, Forest Products Society, 2004Conference paper (Other academic)
    Abstract [en]

    This study was carried out in order to investigate the influence of frozen wood when calibrating a prediction model for the moisture content and density distribution of Scots pine (Pinus sylvestris) and birch (Betula pubescens) using microwave sensors. The material was initially of green moisture content, and thereafter dried to zero moisture content. At each step all the pieces were weighed, scanned with a microwave sensor (Satimo 9, 4 GHz), and CT scanned with a medical CT scanner (Siemens Somatom At.T.) at frozen and room temperature conditions. The output variables from the microwave sensor were used as predictors, and CT images correlated with known moisture content, temperature levels, and frozen/non-frozen conditions were used as response variables. Multivariate models to predict average moisture content and density were calibrated using PLS regression. The models for average moisture content and density were applied on mean values for spatially distributed areas and pixel level, and the distribution was visualized. The result shows that it is possible to predict both moisture content distribution and density distribution with high accuracy using microwave sensors, but frozen conditions require calibration.

  • 62. Lundgren, Nils
    et al.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Johansson, Jan
    Luleå tekniska universitet.
    Predicting moisture content and density distribution of Scots pine by microwave scanning of sawn timber II: Evaluation of models generated on a pixel level2006In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 52, no 1, p. 39-43Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to use images from a microwave sensor on a pixel level for simultaneous prediction of moisture content and density of wood. The microwave sensor functions as a line-scan camera with a pixel size of 8mm. Boards of Scots pine (Pinus sylvestris), 25 and 50mm thick, were scanned at three different moisture contents. Dry density and moisture content for each pixel were calculated from measurements with a computed tomography scanner. It was possible to create models for prediction of density on a pixel level. Models for prediction of moisture content had to be based on average values over homogeneous regions. Accuracy will be improved if it is possible to make a classification of knots, heartwood, sapwood, etc., and calibrate different models for different types of wood. The limitations of the sensor used are high noise in amplitude measurements and the restriction to one period for phase measurements

  • 63. Lundgren, Nils
    et al.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Antti, Lena
    FEM simulation of interactions between microwaves and wood during thawing2006In: Mathematical modeling of wave phenomena: conference on mathematical modeling of wave phenomea, Växjö, Sweden, 14 - 19 August 2005 / [ed] Börje Nilsson; Louis Fishman, Melville, NY: American Institute of Physics (AIP), 2006, p. 260-267Conference paper (Refereed)
    Abstract [en]

    Dipole polarization of water molecules is an important factor when microwaves interact with moist wood. Hence there will be a considerable change in dielectric properties when the wood changes from frozen to nonfrozen condition. The aim of this study was to develop a model that simulates measurements with a microwave scanner based on a sensor working at 9.4 GHz. Two-dimensional finite element modelling (FEM) was implemented to analyze interactions between microwaves and green wood during thawing of frozen wood at room temperature. A medical computed tomography scanner was used to measure the internal structure of density in a piece of wood in green and dry condition. From these density images the distribution of dry weight moisture content was calculated for a cross section of the piece and used in the model. Images describing the distribution of the electric field and phase shift at different temperatures where obtained from the FEM simulation. The results show that simulated values correspond well to measured values. This confirms that the model presented in this study is a useful tool to describe the interaction between microwaves and wood during microwave scanning at varying conditions.

  • 64.
    Myronycheva, Olena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sidorova, Ekaterina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hyperspectral Imaging Surface Analysis for Dried and Thermally Modified Wood: An Exploratory Study2018In: Journal of Spectroscopy, ISSN 2314-4920, E-ISSN 2314-4939, article id 7423501Article in journal (Refereed)
    Abstract [en]

    Naturally seasoned, kiln-dried, and thermally modified wood has been studied by hyperspectral near-infrared imaging between 980 and 2500 nm in order to obtain spatial chemical information. Evince software was used to explore, preprocess, and analyse spectral data from image pixels and link these data to chemical information via spectral wavelength assignment. A PCA model showed that regions with high absorbance were related to extractives with phenolic groups and aliphatic hydrocarbons. The sharp wavelength band at 2135 nm was found by multivariate analysis to be useful for multivariate calibration. This peak represents the largest variation that characterizes the knot area and can be related to areas in wood rich in hydrocarbons and phenol, and it can perhaps be used for future calibration of other wood surfaces. The discriminant analysis of thermally treated wood showed the strongest differentiation between the planed and rip-cut wood surfaces and a fairly clear discrimination between the two thermal processes. The wavelength band at 2100 nm showed the greatest difference and may correspond to stretching of C=O-O of polymeric acetyl groups, but this requires confirmation by chemical analysis.

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  • 65.
    Neyses, Benedikt
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Identifying suitable wood species for wooden products with multivariate data analysis2015In: Holztechnologie, ISSN 0018-3881, Vol. 56, no 2, p. 33-36Article in journal (Refereed)
    Abstract [en]

    In many cases only few wood species are used or even considered for any given wooden product, even though there are hundreds of wood species available. The objective of this project was the development of a time efficient and structured method to identify the most suitable wood species for wooden products, based on a set of required material properties. This goal was achieved by applying multivariate data analysis. The method was based on a dataset consisting of commercially available wood species represented by many different properties. The scores and loadings of the multivariate data analysis method Principal Component Analysis (PCA) were used to identify the wood species with the most fitting property combinations for the product in question. Applying the method to an example case resulted in several plausible alternatives to the commonly used wood species. It is possible to apply the method to any wooden product by determining the set of required properties.

  • 66.
    Neyses, Benedikt
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Nilsson, Annika
    Swerea Mefos.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sundqvist, Bror
    SP.
    Continuous Wood Surface Densification: Chemical Treatments to Reduce the Set-Recovery2016In: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium - Bio-based composites for a sustainable future, Concepción: University of Concepción , 2016, p. 66-77Conference paper (Refereed)
    Abstract [en]

    The hardness of the outer surface of solid wood can be improved by densification, and this opens up new fields of application for low-density species. So far, surface densification is carried out in time- and energy-consuming batch processes, and this means that potential advantages over more expensive hardwood species or non- renewable materials are lost. One of the crucial problems in all densification processes is to reduce the moisture-induced set-recovery of the densified wood cells. In a previous study, a new high-speed continuous surface densification process was introduced, where the surface of solid Scots pine boards could be densified at speeds of up to 80 m/min by a roller pressing technique. The aim of the present study was to integrate the roller pressing technique with different pre- and post-treatment methods to reduce the set- recovery. An aqueous solution of sodium hydroxide was used as a pre-treatment agent to activate the wood surface prior to densification, and a methacrylate ester monomer solution was used as an impregnation agent, both before and after densification. After densification and impregnation, the methacrylate monomers are polymerized by curing in an oven at 100°C in order to stabilize the compressed wood cells. The results show that the different treatments had no significant effect on the set-recovery, probably due to insufficient penetration into the wood material. Future work will focus on improving the treatment process and integrating all process steps into a fully continuous and automatic process. 

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    Neyses et al (2016)
  • 67.
    Neyses, Benedikt
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Nilsson, Annika
    Swerea MEFOS AB.
    Development of a continuous wood surface densification process: the roller pressing technique2016In: Proceedings of the 59th International Convention of Society of Wood Science and Technology.: Forest Resource and Products: Moving Toward a Sustainable Future. / [ed] Susan LeVan-Green, Monona, WI: Society of Wood Science and Technology , 2016, p. 17-24Conference paper (Refereed)
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  • 68.
    Neyses, Benedikt
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wålinder, Magnus
    KTH Byggnadsmateriallära.
    Development of a continuous wood surface densification process with a reduced environmental impact2015In: Proceedings of the 1st COST Action FP1407 Conference, Life Cycle Assessment, EPDs and Modified Wood. Kutnar A, Burnard M, Schwarzkopf M, Simmons A (Eds.), Koper, Slovenia, August 25-26: Life Cycle Assessment, EPDs and Modified Wood, Koper, Slovenia, August 25-26 / [ed] A. Kutnar; M. Burnard; M. Schwarzkopf; A. Simmons, Koper, Slovenia: University of Primorska, Scence and Research Centre of Koper , 2015, p. 30-31Conference paper (Refereed)
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  • 69.
    Niu, Min
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Department of Wood Science & Technology.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cai, LiLi
    Fujian Agriculture and Forestry University, Department of Wood Science & Technology.
    Effect of Si-Al compounds on fire properties of ultra-low density fiberboard2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 2, p. 2415-2430Article in journal (Refereed)
    Abstract [en]

    An ultra-low density fiberboard was made of plant fiber using a liquid frothing approach. The inflammability of the plant fiber limited its application as a candidate for building insulation materials and packaging buffering materials. Si-Al compounds were introduced into the foaming system because of the high temperature resistance of Si and Al compounds. The results from energy-dispersive spectroscopy suggested that the Si and Al relatively evenly covered the surface of the fibers, and their weight ratios in the material increased as a function of the amount of Si-Al compounds. The increasing weight ratios of Si and Al affected the fire properties of the material, reducing the released amount of heat, smoke, and off-gases such as CO and CO2, as well as decreasing the mass loss percentage, shown through the use of a Cone Calorimeter. It follows that Si-Al compounds have an evident collaborative effect on the halogen fire retardant. The system can effectively restrain the fire hazard intensity and the yields of solid and gas volatiles.

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  • 70.
    Niu, Min
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wang, Xiaodong (Alice)
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Xie, Yongqun
    Fujian Agriculture and Forestry University.
    Microstructure of Burned Ultra-Low-Density Fiberboards using Plant Fiber as the Matrix and Si-Al compounds as the Filler2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 2, p. 2903-2912Article in journal (Refereed)
    Abstract [en]

    Ultra-low-density fiberboards (ULDFs) were prepared by a liquid frothing technique using plant fibers as the matrix and Si-Al compounds as the filler to be used as a versatile bio-based composite. Si-Al compounds played an important role in the fire properties of ULDFs. Fire intensity and the amount of volatiles were significantly restrained because of the Si-Al compounds. To determine the combustion mechanism of ULDFs treated by Si-Al compounds, the microstructure of burned specimens was tested by chemical analysis, X-ray diffractometer (XRD), and infrared spectrometer (IR). According to the results from gas chromatography, glucose, xylose, and mannose disappeared in the bottom ashes. After combustion, the XRD profiles of the two ashes became weaker and broader; the sharpest peaks at 18.6o (2) that represented Si-Al compounds remained; the obvious peaks at 22o (2) from cellulose were gone. The results from IR suggested the characteristic functional groups OH, CH, and C=O from carbohydrate also disappeared, and absorbance at 1200 to 400 cm-1, which attributed to the vibration of Si-O, Al-O, and Si- O-Si bonds, increased. In conclusion, fibers are almost completely pyrolyzed at 780 °C. The crystalline structure of Si-Al compounds is rearranged and more amorphous silicon oxide and aluminum oxide are generated.

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  • 71.
    Niu, Min
    et al.
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Xiaodong (Alice)
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Xie, Yongqun
    Fujian Agriculture and Forestry University.
    Morphology of Burned Ultra-low Density Fiberboards2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 4, p. 7292-7301Article in journal (Refereed)
    Abstract [en]

    The synergistic effect of two fire retardants, a Si-Al compound and chlorinated paraffin, was tested on ultra-low density fiberboards (ULDFs). To further understand the mechanism of fire retardancy, morphologies of unburned and burned ULDFs were studied using a scanning electron microscope with energy dispersive spectroscopy. It was found that as the volume of the burned ULDFs shrank, some crevices appeared. In addition, less fly ash formed on the top of specimens, and more bottom ashes remained in the original framework, with a clear network of structure built by the fibers. Carbon was almost absent in the fly ash; however, the weight ratio of C in the bottom ashes reached the maximum (> 43%) of the composition. Oxygen, Al, and Si appeared to have varying weight ratios for different ashes. Oxygen content increased with increasing Si and Al contents. Furthermore, Cl sharply decreased to less than 1% after combustion. Therefore, upon combustion, it was found that almost all of the substances in ULDFs, except for the Si-Al compound, were pyrolyzed to volatile carbon oxides and Cl compounds, especially the fly ash and lightweight C compounds.

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  • 72. Nyström, Jan
    et al.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Methods for detecting compression wood in green and dry conditions1999In: Polarization and Color Techniques in Industrial Inspection: 17 - 18 June 1999, Munich, Germany / [ed] Elzbieta A. Marszalec; Emanuele Trucco, Bellingham, Wash: SPIE - International Society for Optical Engineering, 1999, p. 287-294Conference paper (Refereed)
    Abstract [en]

    The living softwood tree forms compression wood to compensate for external loads during growth, which creates wood fibers with higher longitudinal shrinking and swelling than normal wood at moisture content changes. This is often the cause of undesirable warping of sawn wood products after drying. An automatic detection of severe compression wood is thus useful to reject unwanted pieces. Detection in green condition is often preferred in a sawmill while detection in dry condition is needed in other applications. Three different non- destructive scanning methods were evaluated on both green and dry wood surfaces. The methods used were RGB (red, green, blue) color scanning, tracheid-effect scanning and x-ray scanning. The color and x-ray methods were evaluated on Southern yellow pine lumber, while the tracheid-effect scanning was tested on Norway spruce. For scanning in green condition detection of compression wood was good using the tracheid-effect and color scanning. X-ray scanning was not useful because of the uneven moisture distribution in green lumber. After drying the result changes, tracheid-effect and x-ray scanning have good detection ability while RGB color does not provide sufficient information for reliable detection.

  • 73. Nyström, Jan
    et al.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Real-time spectral classification of compression wood in Picea abies1999In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 45, no 1, p. 30-37Article in journal (Refereed)
    Abstract [en]

    Compression wood is formed by the living tree to compensate for external loads. It creates wood fibers with properties undesirable in sawn products. Automatic detection of compression wood can lead to production advantages. A wood surface was scanned with a spectrometer, and compression wood was detected by analyzing the spectral composition of light reflected from the wood surface within the visible spectrum. Linear prediction models for compression wood in Norway spruce (Picea abies) were produced using multivariate analysis and regression methods. The resulting prediction coefficients were implemented in a scanning system using the MAPP2200 smart image sensor combined with an imaging spectrograph. This scanning system is capable of making a pixelwise classification of a wood surface in real time. Classification of one spruce plank was compared with analysis by scanning electron microscopy, showing that the automatic classification was correct in 11 of 14 cases.

  • 74.
    Pahlberg, Tobias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Feature recognition and fingerprint sensing for guiding a wood patching robot2012In: World Conference on Timber Engineering: WCTE Auckland New Zealand 15-19 July 2012 / [ed] Pierre Quenneville, Auckland: New Zealand Timber Design Society , 2012, p. 724-733Conference paper (Other academic)
    Abstract [en]

    This paper includes a summary of a few commonly used object recognition techniques, as well as a sensitivity analysis of two feature point recognition methods. The robustness was analyzed by automatically trying to recognize 886 images of pine floorboards after applying different levels of distortions. Recognition was also tested on a subset of 5% of the boards which were both re-scanned using a line scan camera and photographed using a digital camera. Experiments showed that both the Block matching method and the SURF method are valid options for recognizing wood products covered with distinct features. The Block matching method outperformed the SURF method for small geometric distortions and moderate radiometric distortions. The SURF method, in its turn, performed better compared to the other method when faced with low resolution digital images.

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  • 75.
    Pahlberg, Tobias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Recognition of boards using wood fingerprints based on a fusion of feature detection methods2015In: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 111, p. 164-173Article in journal (Refereed)
    Abstract [en]

    This paper investigates the possibility to automatically match and recognize individual Scots pine (Pinus sylvestris L.) boards using a fusion of two feature detection methods. The first method denoted Block matching method, detects corners and matches square regions around these corners using a normalized Sum of Squared Differences (SSD) measure. The second method denoted the SURF (Speeded-Up Robust Features) matching method, matches SURF features between images (Bay et al., 2008). The fusion of the two feature detection methods improved the recognition rate of wooden floorboards substantially compared to the individual methods. Perfect matching accuracy was obtained for board pieces with more than 20 knots using high quality images. More than 90% matching accuracy was achieved for board pieces with more than 10 knots, using both high- and low quality images.

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  • 76.
    Pahlberg, Tobias
    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.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Wood fingerprint recognition using knot neighborhood K-plet descriptors2015In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 49, no 1, p. 7-20Article in journal (Refereed)
    Abstract [en]

    In the wood industry, there is a wish to recognize and track wood products through production chains. Traceability would facilitate improved process control and extraction of quality measures of various production steps. In this paper, a novel wood surface recognition system that uses scale and rotationally invariant feature descriptors called K-plets is described and evaluated. The idea behind these descriptors is to use information of how knots are positioned in relation to each other. The performance and robustness of the proposed system were tested on 212 wood panel images with varying levels of normally distributed errors applied to the knot positions. The results showed that the proposed method is able to successfully identify 99–100 % of all panel images with knot positional error levels that can be expected in practical applications

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  • 77.
    Pahlberg, Tobias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Popovic, Djordje
    Jönköping University.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Crack detection in oak flooring lamellae using ultrasound-excited thermography2018In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 88, p. 57-69Article in journal (Refereed)
    Abstract [en]

    Today, a large number of people are manually grading and detecting defects in wooden lamellae in the parquet flooring industry. This paper investigates the possibility of using the ensemble methods random forests and boosting to automatically detect cracks using ultrasound-excited thermography and a variety of predictor variables. When friction occurs in thin cracks, they become warm and thus visible to a thermographic camera. Several image processing techniques have been used to suppress the noise and enhance probable cracks in the images. The most successful predictor variables captured the upper part of the heat distribution, such as the maximum temperature, kurtosis and percentile values 92–100 of the edge pixels. The texture in the images was captured by Completed Local Binary Pattern histograms and cracks were also segmented by background suppression and thresholding.

    The classification accuracy was significantly improved from previous research through added image processing, introduction of more predictors, and by using automated machine learning. The best ensemble methods reach an average classification accuracy of 0.8, which is very close to the authors’ own manual attempt at separating the images (0.83).

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  • 78.
    Popovic, Djordje
    et al.
    Jönköping University, School of Engineering.
    Meinlschmidt, Peter
    Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI.
    Plinke, Burkhard
    Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI.
    Dobic, Jovan
    Tarkett Eastern Europe, BU WOOD.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Crack Detection and Classification of Oak Lamellas Using On-Line and Ultrasound Excited Thermography2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 464-470Article in journal (Refereed)
    Abstract [en]

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

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  • 79.
    Sandak, Jakub
    et al.
    IVALSA/CNR, via Biasi 75, 38010 San Michele All’Adige (TN), Italy.
    Sandak, Anna
    IVALSA/CNR, via Biasi 75, 38010 San Michele All’Adige (TN), Italy.
    Dusan, Pauliny
    IVALSA/CNR, via Biasi 75, 38010 San Michele All’Adige (TN), Italy.
    Krasnoshlyk, Victoria
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Near infrared spectroscopy as a tool for estimation of mechanical stresses in wood2013In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 778, p. 448-453Article in journal (Refereed)
    Abstract [en]

    Significant scientific work has been dedicated for exploration of the infrared applications within wood science and technology, not much has been done linking it to the mechanical testing. It is expected that due to mechanical stresses (and related deformations) the interaction between constitutive elements of wood changes, proportionally to the stresses applied. The response of the material to mechanical stresses (such as tensile loading) on the molecular level should be therefore detectable by means of infrared spectroscopy. Dedicated tests have been devoted for proving this hypothesis. Self developed testing machine has been integrated with infrared spectrometer in order to conduct a series fully controlled mechanical tests. It was possible to predict stress level of wood during tension by applying proper chemometric analysis (partial least square (PLS) models). Implementation of infrared spectroscopy in to timber engineering and mechanical testing of wood provides very essential supplement to the typical information collected during standard tests. More additional tests and reference data is necessary in order to create more reliable and universal model suitable for routine assessments. Nevertheless, it was demonstrated that prediction of the stress on the basis of the infrared spectra is possible.

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  • 80.
    Sandberg, Karin
    et al.
    SP Technical Research Institute of Sweden.
    Mostolygin, Kirill
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Effect of lamellas annual-ring orientation on cracking of glulam beams investigated with computer tomography and image processing2013In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, no 3, p. 166-174Article in journal (Refereed)
    Abstract [en]

    Cracks in glulam beams can reduce their strength, depending on the crack's depth, length, and location and can also be a passage for the accumulation of water and dirt. To avoid cracks, the relationship between cracks (area of cracks, mm2) and annual-ring orientation in glulam beams of spruce (Picea abies), and pine (Pinus sylvestris) with different dimensions and surface treatments was investigated using RGB images of the surface and tomography images of the cross-sections. Image processing was used to measure characteristics visible in the photos such as crack area and lamella position in the beam. Combination of lamellas in lay up was measured from computer tomography images. Four types of combinations were defined; type 1 (pith side facing outward), types 2 and 3 (pith to the same side), and type 4 (pith sides meet pith side). It was found that the area close to the glue line in the lamellas in combination type 4 is the most subject to cracking, whereas combinations of type 1 show the highest resistance to cracking. This means that type 4 should not be used in glulam beams, because the lamellas shrink apart from each other causing stresses and resulting cracks.

  • 81.
    Scheepers, Gerhard
    et al.
    RISE Bioekonomi.
    Olsson, Jörgen
    RISE Bioekonomi.
    Lycken, Anders
    RISE Bioekonomi.
    Grahn, Thomas
    RISE Bioekonomi.
    Lundqvist, Sven-Olof
    RISE Bioekonomi.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hållfasthetsbestämning av virke med en NIR-kamera2017Report (Other academic)
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  • 82.
    Vaziri, Mojgan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Abrahamsson, Lars
    Vattenfall AB, BU Fuel, Engineering & Projects, Solna, Sweden.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Welding of wood in the presence of wollastonite2020In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 15, no 1, p. 1617-1628Article in journal (Refereed)
    Abstract [en]

    The use of wollastonite as a natural additive for the welding of Scots pine improved the water resistance and shear strength of the welded joint. The X-ray computed tomography images revealed that the welding of Scots pine with wollastonite could postpone crack formation in the welded joints. The specimens welded for a longer time (5 s) had a more uniform distribution of wollastonite particles in welded joints. The microstructure of the wood and the thickness of the wood cell walls also had a great influence on the thickness and strength of the welded joints. Water immersion tests showed that the use of wollastonite in wood joints was able to meet the requirement of resistance to frequent short-term and long-term exposure to water.

  • 83.
    Vorobyev, Alexey
    et al.
    Division of Appplied Mechanics, Uppsala University, Box 534, SE-751 21, Uppsala, Sweden.
    Garnier, Florian
    École Nationale Supérieure de Mécanique et des Microtechniques, 26 Rue de l'Épitaphe, 25000 Besançon, France.
    van Dijk, Nico P.
    Division of Appplied Mechanics, Uppsala University, Box 534, SE-751 21, Uppsala, Sweden.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Gamstedt, Kristofer
    Division of Appplied Mechanics, Uppsala University, Box 534, SE-751 21, Uppsala, Sweden.
    Evaluation of displacements by means of 3D laser scanning in a mechanically loaded replica of a hull section of the Vasa ship2018In: Digital Applications in Archaeology and Cultural Heritage, ISSN 2212-0548, Vol. 11, article id e00085Article in journal (Refereed)
    Abstract [en]

    For a development of full-scale finite-element models of large objects in cultural heritage, it can be useful to mechanically test replicas of key parts to identify structural properties which would otherwise not be available. This paper presents full scale tests on a replica of a section of the hull of the 17th century warship Vasa in three load configurations. We focus on determining a displacement of the loaded replica from 3D laser measurements. Two measures were found useful: (i) 3D displacements at well-defined intersections of the wooden replica, and (ii) normal displacements of larger surfaces. Wood surfaces were preferred to steel parts of the rig since the latter showed more scatter in displacement values in their point clouds caused by their reflective properties. The measurements were verified with draw-wire sensors. Some of these sensors were attached to the steel rig supporting the replica and, therefore, measured relative displacements. The scanning data was also useful to quantify the absolute movement of the steel rig supporting the replica, which improved the precision of the measurements of replica deformation. Finally, it is discussed how the replica test results can be used in a model of the entire museum ship.

  • 84.
    Wang, Alice
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Björnberg, Jonatan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ahmed, Sheikh Ali
    Department of Forest Products, Linnaeus University, Växjö, Sweden.
    Wan, Hui
    Mississippi State University, Department of Sustainable Bioproducts, Mississippi , Forest Products Laboratory, Mississippi State University, Mississippi State, Department of Sustainable Bioproducts, Mississippi State University, Mississippi State.
    Niemz, Peter
    Department of Civil Engineering, ETH Zurich, Switzerland.
    Effect of Low Temperatures on the Block Shear Strength of Norway Spruce Glulam Joints2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 9638-9648Article in journal (Refereed)
    Abstract [en]

    The block shear strength of Norway spruce (Picea abies (L.) Karst.) glulam joints was tested under low temperatures. Glulam samples were glued with the three of the most common outdoor structural adhesives. The cold temperatures tested were 20, -20, -30, -40, -50, and -60 degrees C. Within the temperature test range, the block shear strength of the glulam joints was resistant to the effect of temperature. As the temperature decreased, the joints' block shear strength did not show any significant change. In most cases, phenol-resorcinol-formaldehyde (PRF) adhesive yielded the strongest block shear strength, while melamine-formaldehyde (MF) adhesive yielded the weakest block shear strength. Melamine-urea-formaldehyde (MUF) adhesive yielded similar results to those of MF adhesives for all temperatures tested. The block shear strengths of the glulam joints with PRF, MUF, and MF adhesives were not sensitive to temperature change. The results indicated that PRF, MUF, and MF adhesives are stable for outdoor structural engineered wood construction in cold climates. The results also suggest that the SS-EN 14080 (2013) standard for the block shear method may not be the proper standard for testing differences in shear strength at different temperatures. The EN 302-1 (2011) standard could be more suitable for this purpose.

  • 85.
    Wang, Xiaodong (Alice)
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Engineered wood in cold climate: application to monitoring of a new Swedish suspension bridge2013In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 639-640, p. 96-104Article in journal (Refereed)
    Abstract [en]

    Engineered wood is increasingly used in large structures in Europe, though little is known of its behavior in cold climate. This paper presents the structural health monitoring (SHM) system of a newly built suspension bridge with a deck of glulam timber as well as a bond stability study regarding cold climate performance of engineered wood. The bridge is located in Skellefteå in northern Sweden, and it connects two parts of the city situated on opposite shores of the Skellefteå river. In this ongoing study of the timber-bridge, a structural health monitoring system is employed to verify structural design and long-term performance. This 130m-span bridge is monitored using GNSS receivers, MEMS accelerometers, laser positioning systems, wireless moisture content sensors, strain gauges and weather stations. Data from the monitoring systems is analyzed regarding accuracy, complexity, costs and reliability for long time use. Engineered wood application in bridges, sports centers and timber buildings are discussed. Bond stability of glulam structures in cold climate is also examined in a range of experiments ranging from small glued wood joints to full size glulam bridge performance over time. From an engineered wood material point of view, the study is relevant to cold regions such as Scandinavia, Canada, Alaska, Russia, and the northern parts of China and Japan etc. The engineered wood constructions in these areas will be exposed to low temperature in a quite long period each year. The goal is to determine how engineered wood behaves when exposed to temperatures between 20 °C to -60 °C.

  • 86.
    Wang, Xiaodong (Alice)
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sundqvist, Bror
    SP Technical Research Institute of Sweden, SP Wood Technology, Skellefteå.
    Ormarsson, Sigurdur
    Department of Civil Engineering, Technical University of Denmark, Danmarks tekniska universitet.
    Wan, Hui
    Forest Products Laboratory, Mississippi State University, Mississippi State.
    Niemz, Peter
    Department of Civil Engineering, ETH Zurich, Switzerland.
    Impact of cold temperatures on the shear strength of Norway spruce joints glued with different adhesives2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 2, p. 225-233Article in journal (Refereed)
    Abstract [en]

    As wood construction increasingly uses engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives used. Bondline strength is a crucial issue for engineered wood applications, especially in cold climates. In this study, Norway spruce (Picea abies) joints (150 mm × 20 mm × 10 mm) were bonded with seven commercially available adhesives: polyurethane (PUR), polyvinyl acetate (PVAc), emulsion-polymer-isocyanate (EPI), melamine-formaldehyde (MF), phenol-resorcinol-formaldehyde (PRF), melamine-urea-formaldehyde1 (MUF1), and melamine-urea-formaldehyde2 (MUF2). Each adhesive was tested at six temperatures: 20, −20, −30, −40, −50 and −60 °C. Generally, within the temperature test range, temperature changes significantly affected the shear strength of solid wood and wood joints. As the temperature decreased, the shear strength decreased. PUR adhesive in most cases resulted in the strongest shear strength and MUF adhesive resulted in the weakest. MF and PRF adhesives responded to temperature changes in a similar manner to that of the PUR adhesive. The shear strengths of wood joints with PVAc and EPI adhesives were more sensitive to temperature change. At low temperatures, the variability of shear strengths increased with all adhesives. Percent wood failures of joints bonded with different adhesives in most cases were not sensitive to temperature changes

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  • 87.
    Wang, Xiaodong (Alice)
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sundqvist, Bror
    SP Technical Research Institute of Sweden, SP Sustainable Built Environment, Skellefteå, Sweden.
    Ormarsson, Sigurdur
    Department of Civil Engineering, Technical University of Denmark, Denmark.
    Wan, Hui
    Department of Sustainable Bioproducts, Mississippi State University, Mississippi State.
    Niemz, Peter
    Department of Civil Engineering, ETH Zurich, Switzerland.
    Shear strength of Scots pine wood and glued joints in cold climate2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 1, p. 944-956Article in journal (Refereed)
    Abstract [en]

    The impacts of cold temperatures on the shear strength of Scots pine (Pinus sylvestris) joints (150 mm x 20 mm x 10 mm) glued with seven commercially available adhesives were studied in this work. The adhesives used here were: polyurethane (PUR), polyvinyl acetate (PVAc), emulsion-polymer-isocyanate (EPI), melamine-formaldehyde (MF), phenol-resorcinol-formaldehyde (PRF), melamine-urea-formaldehyde1 (MUF1), and melamine-urea-formaldehyde2 (MUF2). The cold temperatures investigated here were: 20, -20, -30, -40 and -50 °C. Generally, within the temperature test range, the shear strength of Scots pine solid wood and wood joints resisted more temperature effects than Norway spruce. As the temperature decreased, only some of the joints shear strength decreased significant. PUR adhesive in most cases resulted in the strongest shear strength and MUF adhesive resulted in the weakest. MF adhesive responded to temperature changes in a similar manner to that of the PUR and PVAc adhesives. The shear strengths of wood joints with PRF and EPI adhesives were more sensitive to temperature change. For dynamic tests of shear strength, the values for 12 hours and 6 days tests under cycled of temperature (-20°C and 0°C) were compared. For 6 days tests, the values for the various types of the adhesives are lower than for 12 hours. Therefore, the duration of the samples subjected to the same temperature had significant impact on shear strength. PUR is the most stable adhesive; MUF and PRF have significant decrease.

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  • 88.
    Wang, Xiaodong (Alice)
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sundqvist, Bror
    SP Technical Research Institute of Sweden, SP Wood Technology, Skellefteå.
    Ormarsson, Sigurdur
    Department of Civil Engineering, Technical University of Denmark, Danmarks tekniska universitet.
    Wan, Hui
    Forest Products Laboratory, Mississippi State University, Mississippi State.
    Niemz, Peter
    Department of Civil Engineering, ETH Zurich, Switzerland.
    Wood construction under cold climate: Part one: Impact of cold temperatures on the shear strength of different adhesives glued wood joints of Norway spruce and Scots pine2014Conference paper (Other academic)
  • 89.
    Wang, Xiaodong (Alice)
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sundqvist, Bror
    SP Technical Research Institute of Sweden, SP Wood Technology, Skellefteå.
    Ormarsson, Sigurdur
    Department of Civil Engineering, Technical University of Denmark.
    Wan, Hui
    Forest Products Laboratory, Mississippi State University, Mississippi State.
    Niemz, Peter
    Department of Civil Engineering, ETH Zurich, Switzerland.
    Wood Construction Under Cold Climate: Part one: Impact of cold temperatures on the shear strength of different adhesives glued wood joints of Norway spruce and Scots pine2014Conference paper (Refereed)
    Abstract [en]

    As wood constructions increasingly use engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives system. The glueline stability is a crucial issue for engineered wood application, especially under cold climate. In this study, Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) joints (150mm x 20mm x 10mm) were bonded with seven commercially available resins (PUR, PVAc, EPI, MF, MUF1, PRF and MUF2) and tested at six temperatures (20, -20, -30, -40, -50 and -60 °C), respectively. Generally, for both species, temperature changes significantly affected shear strength of wood joints. As temperature decreased, the shear strength decreased. PUR resin resulted in the strongest shear strength at all temperatures tested. MF resin responded to temperature changes in a similar ways as the PUR resin. The shear strength of wood joints with EPI resins was sensitive to temperature change. MUF, PRF and PVAc resins demonstrated different characters with Norway spruce and Scot pine. At room temperature, all types of adhesive showed relative stability, in terms of shear strength variation. While at low temperature, the shear strength varied considerably. More specimens need to be tested in further work to more completely present the issue. The EN 301 and EN 302 may need to be specified based on wood species.

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