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  • 1. Arfvidsson, J.
    et al.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wiberg, P.
    Luleå tekniska universitet.
    The development of a moisure sorption model to predict moisture within solid wood based on non-destructive moisture gradient measurements using CT-scanning and digital ...1997In: International Conference on Wood-Water Relations, 16 - 17 June 1997, Copenhagen, Denmark: [COST Action E8, Mechanical Performance of Wood and Wood Products] / [ed] Preben Hoffmeyer, Copenhagen: Technical University of Denmark , 1997Conference paper (Refereed)
  • 2.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Estimation of miosture content in wood using dual x-ray energies in a medical CT-scanner2016In: Process Technologies for the Forest & Biobased Products Industries: PTF BPI 2016, 2016, p. 22-Conference paper (Other academic)
  • 3.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Söderström, Ove
    c Professor Emeritus of Building Materials, Stockholm, Sweden.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Real-time wood moisture-content determination using dual-energy X-ray computed tomography scanning2019In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, no 6, p. 437-444Article in journal (Refereed)
    Abstract [en]

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

  • 4.
    Fredriksson, Maria
    et al.
    Division of Building Materials, Lund University.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    End grain water absorption and redistribution in slow-grown and fast-grown Norway spruce (Picea abies (L.) Karst.) heartwood and sapwood2013In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, no 4, p. 245-252Article in journal (Refereed)
    Abstract [en]

    Wood is susceptible to decay by rot fungi if it is exposed to high-moisture contents during long periods of time and it is therefore important to limit the duration of such periods. Critical points in outdoor wood structures are, for example, end grain surfaces in joints where water can get trapped after a rain. It is therefore of interest to study both absorption and redistribution of moisture in wood. This paper presents moisture content profiles during end grain water absorption and redistribution in Norway spruce (Picea abies (L.) Karst.) measured by computed tomography with the specimens in individual climate boxes. Heartwood and sapwood of two provenances (slow-grown and fast-grown wood) were included. No major differences were seen between the water uptake of the slow-grown and the fast-grown wood since the densities were similar despite of the large difference in growth ring width. However, for the sapwood specimens, the moisture content was higher further into the specimens than for the heartwood specimens in agreement with previous studies. For the slow-grown wood, the redistribution was also generally more rapid for the sapwood specimens than for the heartwood specimens.

  • 5. Grundberg, Stig
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Noggrannhet vid detektering av stockars inre kvalitet: avrapportering av steg 11989Report (Other academic)
  • 6. Grundberg, Stig
    et al.
    Lindgren, Owe
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The development of an X-ray based scanner for log grading at full protection speed1996In: Proceedings / 10th International Symposium on Nondestructive Testing of Wood: Lausanne, Switzerland, August 26-27-28, 1996 / [ed] J.L. Sandoz, Lausanne: Swiss Federal Institute of Technology , 1996Conference paper (Refereed)
  • 7.
    Lindberg, Henrik
    et al.
    Luleå tekniska universitet.
    Grahn, Johnny
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hellgren, A-C.
    Water diffusion through acrylate latex paint films measured by computed tomography1996In: Proceedings / 10th International Symposium on Nondestructive Testing of Wood: Lausanne, Switzerland, August 26-27-28, 1996 / [ed] J.L. Sandoz, Lausanne: Swiss Federal Institute of Technology , 1996Conference paper (Refereed)
  • 8.
    Lindberg, Henrik
    et al.
    Luleå tekniska universitet.
    Lindberg, L.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Mätning av trädensitet och fuktinnehåll i trä: Kalibrering av datortomograf1990Report (Other academic)
  • 9.
    Lindberg, K.A.H.
    et al.
    Luleå tekniska universitet.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grahn, Johnny
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Fast water paths through latex paint films1996In: Durability of Building Materials and Components 7: proceedings of the seventh International Conference on Durability of Building Materials and Components, 7DBMC, Stockholm, Sweden, 19-23 May 1996 / [ed] Christer Sjöström, London: Taylor and Francis Group , 1996, p. 667-672Conference paper (Refereed)
  • 10.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Accuracy of medical CAT-scan images for non-destructive density measurements in small volume elements within solid wood1990Report (Other academic)
  • 11.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Medical CAT-scanning: X-ray absorption coefficients, CT-numbers and their relation to wood density1991In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 25, no 5, p. 341-349Article in journal (Refereed)
    Abstract [en]

    This paper describes how X-ray absorption coefficients and CT-number in medical CAT-scanning can be calculated for dry and wet wood. A comparison with earlier recorded data for dry wood showed that the deviation between calculated and measured CT-numbers was not significant. Linear regression showed that wood density could be measured with an accuracy of +/- 4 kg/m3. Wood having the same green density but containing different amounts of water have different absorption coefficients and CT-numbers. A linear relationship between CT-numbers and density of wood containing water was developed. Wood density could be measured with an accuracy of +/- 13.4 kg/m3

  • 12.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Medical CT-scanners for non-destructive wood density and moisture content measurements1992Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Most methods to measure wood density and moisture content are destructive. One non-destructive technique is X-ray computed tomography (CT). The actual physical variable measured is the X-ray linear attenuation coefficient which is highly density dependent. The primary purpose of this thesis is to establish the accuracy of medical CT-scanners for wood density measurements in small volume elements. As wood moisture content has an effect on wet wood density, the secondary purpose of the thesis is to suggest and evaluate an image processing method to perform moisture content measurements using CT-images. The thesis contains a method for calculating X-ray attenuation coefficients and CT-numbers for wood and describes how the CT-numbers correlate to wood densities. Conventional methods are not suitable for measuring densities of small volumes inside solid wood. Therefore, a method for calculating the accuracy in CT-images depending on image noise is suggested for medical CT-scanners. The results are experimentally compared to density measurements made with a microtomography CT-scanner and show that wood density can be measured with an accuracy of +/-1kg/m3 in a 2 x 2 x 1.5 mm volume element using a medical CT-scanner at a significance level of 0.05. However, the area within which measurements are made must not contain large density variations deriving from annual growth rings. The method suggested for moisture content measurements indicates an accuracy of +/-1% in moisture content in 3 x 3 x 5 mm volumes. In practice an accuracy of +/-1.4% or better below fiber saturation point and +/-4% or better above fiber saturation point can be expected in corresponding volumes.

  • 13.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    On the relationship between density/moisture content in wood and x-ray attenuation in computed tomography1985Report (Other academic)
  • 14.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Proceedings from the 2nd International Seminar/Workshop on Scanning Technology and Image Processing on Wood: Skellefteå, Sweden, August 14-16, 19951995Collection (editor) (Other academic)
  • 15.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The accuracy of medical CAT-scan images for non-destructive density measurements in small volume elements within solid wood1991In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 25, no 6, p. 425-432Article in journal (Refereed)
    Abstract [en]

    A comparison between identically sampled CAT-scan images of five wooden test pieces (Pinus sylvestris) showed that the CT-number in each pixel varied with a standard deviation of ±3.9-11.1 CT numbers. This inaccuracy in CT-numbers is called "noise". As long as the direction of rotation can be controlled the noise in CAT-scan images of wood can be assumed to be approx. ±4 CT-numbers in each pixel. A calculation showed the average CT-number must differ ±1 unit to distinguish average CT-numbers in 2 × 2 × 1.5 mm volumes within solid wood. It has previously been shown that a change of ±1 CT-number corresponds approx. to a change in density of ±1 kg/m3. On the other hand, there is a difference in X-ray absorption coefficients between wood and water. Thereby dry wood densities in corresponding volumes must differ approx. ±2 kg/m3 to significantly be distinguished. The corresponding figure is approx. ±6 kg/m3 for wet wood densities with moisture content levels ranging from 6-100%.

  • 16.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    X-ray absorption coefficients CT-numbers and their relation to wood density: medical cat-scanning1990Report (Other academic)
  • 17.
    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.

  • 18.
    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)
  • 19.
    Lindgren, Owe
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundqvist, S.-O.
    Geometric transformation (warping) of CT-images: an aid for non-destructive wood density and moisture content measurements2003In: Developments in image processing and scanning of wood: selected and edited papers from the 4th International Conference on Image Processing and Scanning of Wood, Mountain Lake, Virginia, USA, 21 - 23 August, 2000 / [ed] A.Lynn Abbott, 2003Conference paper (Refereed)
  • 20.
    Lindgren, Owe
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Orädd, Greger
    Umeå universitet.
    First observations using magnetic resonance imaging (MRI) for non-destructive glue line water durability investigations2003In: IWSS 5: Proceedings / Fifth International conference om image processing and scanning of wood, March 23 to 26, Bad Walterdorf, Austria, Europe, 2003, p. 87-94Conference paper (Other academic)
  • 21.
    Lindgren, Owe
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Seifert, Thomas
    Department of Forest & Wood Science, Stellenbosch University.
    Plessis, Anton du
    Central Analytical Facilities, Stellenbosch University.
    Moisture Content Measurements in Wood Using Dual Energy CT-scanning: A Feasibility Study2016In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 11, no 5, p. 312-317Article in journal (Refereed)
    Abstract [en]

    Currently computed tomography (CT) scanning provides a non-destructive method to determine moisture content in wood in three dimensions. With the current methodology two measurements are needed, one with the scanned piece of wood’s moist state and one after drying. Then the difference of the images can be calculated. The drawback and challenge is that dimensional changes due to shrinkage of wood in the drying process have to be compensated for by image processing. In this study a dual-energy CT scanning method is tested based on the consecutive scanning of wood samples at different energy levels to differentiate water from wood, without the necessity to dry the sample and thus without the need for complex image correction. Not quantified but visible differentiations due to moisture content were obtained on small cubical pine samples of different densities by quick consecutives scans at 60 and 200 kV. The results suggest that given that the pixels in the CT images are representing absorption coefficients it should be possible to directly measure moisture content in wood non-destructively in small volume elements inside solid wood in three dimensions. Further applications of this technique in industrial CT scanning of wood are discussed.

  • 22.
    Mansouri, Hamid
    et al.
    ENSTIB-UHP, Epinal.
    Pizzi, Antonio
    ENSTIB-UHP, Epinal.
    Leban, Jean-Michel
    INRA, Campenoux.
    Delmotte, L.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Vaziri, Mojgan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Causes for the improved water resistance in pine wood linear welded joints2011In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 25, no 16, p. 1987-1995Article in journal (Refereed)
    Abstract [en]

    Linear vibration welding of good quality pine (Pinus sylvestris) wood from Sweden containing a small proportion of a native mixture of terpenoic acids, known under the collective name of rosin, has been shown to yield joints of much upgraded water resistance. This has been shown to be due to the protecting influence the molten rosin from the wood itself has on the welded interphase, because of the water repellency of rosin. Joints of unusually high percentage wood failure but modest strength were obtained, rosin apparently reinforcing the welded interphase to yield weldline strengths always much higher than the strength of the surrounding wood.

  • 23.
    Sandberg, Karin
    et al.
    Luleå tekniska universitet.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Measurement of spruce moisture gradients using CT scanning during three cycles of liquid water absorption2003In: IWSS 5: Proceedings / Fifth International conference om image processing and scanning of wood, March 23 to 26, 2003, Bad Waltersdorf, Austria, Europe, Joanneum research , 2003, p. 95-106Conference paper (Other academic)
  • 24.
    Vaziri, Mojgan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pizzi, A.
    ENSTIB-LERMAB, Université Henri Poincaré - Nancy.
    Mansouri, H.R.
    ENSTIB-LERMAB, Université Henri Poincaré - Nancy.
    Moisture sensitivity of Scots pine joints produced by linear frictional welding2010In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 24, no 8, p. 1515-1527Article in journal (Refereed)
    Abstract [en]

    The industrial application range of welded wood so far has been limited to interior use because of its poor moisture resistance. Influences of some welding and wood parameters such as welding pressure, welding time, and heartwood/sapwood on water resistance of Scots pine (Pinus sylvestris) were investigated. An X-ray Computed Tomography scanner was used to monitor density change in weldlines during water absorption-desorption. Axial samples measuring 200 mm × 20 mm × 20 mm from Scots pine were welded and placed standing in 5-mm-deep tap water. Then they were taken out of the water one at a time and scanned at 10-min intervals until the first crack appeared in the weldline where the two parts of each specimen made connection. Results showed that the X-ray Computed Tomography can be used as an effective tool to study welded wood. Welding pressure, welding time, and heartwood/sapwood showed significant effect on length and location of the crack in the welded zone. Data evaluation showed that combination of 1.3 MPa welding pressure, 1.5 s welding time and using heartwood led to highest moisture resistance, which produced only a very short crack in the beginning of the weldline

  • 25.
    Vaziri, Mojgan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pizzi, Antonio
    ENSTIB-UHP, Epinal.
    Influence of machine setting and wood parameters on crack formation in Scots pine joints produced by linear friction welding2012In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 26, no 18-19, p. 2189-2197Article in journal (Refereed)
    Abstract [en]

    Previous investigations on linear welded woods have shown that the connections are not sufficiently resistant to water for use in outdoor conditions. Therefore, they are utilized mainly for non-structural use, with only short time exposure to varying humidity. Influences of some welding and wood parameters such as welding pressure, welding time and heartwood or sapwood on crack formation in the weldline of Scots pine (Pinus sylvestris) were investigated. Axial samples measuring 200 mm×20 mm×20 mm from Scots pine were welded, placed vertically in 5-mm-deep tap water and were taken out of the water one at a time after each 10 min of water absorption. Then they were scanned and put back into water until the first crack appeared in the weldline. An X-ray Computer Tomography (CT-) scanner was used to monitor water movement and density change in the weldlines during water absorption–desorption. CT-scanning enabled to detect the cracks as they formed in the weldline and could be used in wood welding studies. Data evaluation showed that all the three studied parameters had significant effects on crack formation and that crack occurrence could be postponed by using heartwood samples with 1.3 MPa welding pressure and 1.5 s welding time.

  • 26.
    Vaziri, Mojgan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pizzi, Antonio
    ENSTIB-LERMAB, Université Henri Poincaré - Nancy.
    Influence of welding parameters and wood properties on the water absorption in Scots pine joints induced by linear welding2011In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 25, no 15, p. 1839-1847Article in journal (Refereed)
    Abstract [en]

    Wood welding is an environmentally-friendly and very quick technique to yield wood joints in just a few minutes and without using any adhesives. The only limitation of welded wood is that the joint is suitable only for interior use. Exterior use, or use in an environment with varying humidity requires water resistance of the welded joints. An investigation was performed to determine the effects of welding parameters and wood properties on water absorption in the weldline and how to reduce it through controlling the production parameters. The influences of welding pressure, welding time, and heartwood/sapwood on water absorption in the weldline of Scots pine (Pinus sylvestris) joints were investigated. Specimens composed of two pieces of heartwood or sapwood, each of dimensions 200 mm × 20 mm × 20 mm, were welded together to form specimens of dimensions 200 mm × 20 mm × 40 mm. The specimens were allowed to stand in 5-mm-deep tap water and then they were taken out of the water one at a time and scanned in 10-min intervals until the first crack appeared in the weldline. An X-ray Computerized Tomography scanner was employed to monitor water movement and density change in weldlines during water absorption-desorption. All three evaluated parameters showed significant effect on water absorption. Samples of heartwood welded by 1.3 MPa welding pressure and 1.5 s welding time showed the lowest water absorption

  • 27.
    Vaziri, Mojgan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pizzi, Antonio
    ENSTIB-LERMAB, Université Henri Poincaré - Nancy.
    Influence of weldling parameters on weldline density and its relation to crack formation in welded Scots pine joints2011In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 25, no 15, p. 1819-1828Article in journal (Refereed)
    Abstract [en]

    Exterior use of welded wood laminates without further treatment is not recommended. Frictional welded joints have poor resistance to moisture variation, especially to drying. Therefore, application of welded woods is limited to interior use without exposure to highly variable air humidity. Influences of some welding and wood parameters such as welding pressure, welding time and heartwood/sapwood on weldline density of Scots pine (Pinus sylvestris) joints were investigated. Interdependence between density and water resistance of weldline (in terms of crack time) was also studied by comparing the results of this investigation with those of the earlier studies. Specimens composed of two wood pieces, each measuring 20 mm x 20 mm x 200 mm, were welded together to form a specimen measuring 40 mm x 20 mm x 200 mm by a vibration movement of one wood surface against another at a frequency of 150 Hz. An X-ray Computerized Tomography scanner was used to measure weldline density. Weldlines of sapwood produced by 1.3 MPa welding pressure and 1.5 s welding time showed the highest density. No correlation between weldline density and crack time was evident.

  • 28. Vaziri, Mojgan
    et al.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pizzi, Antonio
    ENSTIB-UHP, Epinal.
    Optimization of tensile-shear strength for linear welded Scots pine2012In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 26, no 1-3, p. 109-119Article in journal (Refereed)
    Abstract [en]

    The mechanical performance of welded wood has a decisive role in its applications. This study was performed to determine the welding conditions that optimized the tensile-shear strength of welded Scots pine (Pinus sylvestris). Tensile-shear strength as a function of welding pressure, welding time and holding time1 was measured according to European standard EN 205. Maximum tensile-shear strength of welded sample was 9.3 MPa that was obtained using 1.3 MPa welding pressure, 2.8 s welding time and 70 s holding time. This tensile-shear strength was about two times that of PVAc-glued samples. According to data evaluation tensile-shear strength could be optimized to 9.7 MPa by increasing the welding time to 3.5 s and decreasing the holding time to 60 s.

  • 29.
    Vaziri, Mojgan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Orädd, Greger
    Department of Radiation Sciences, Umeå University.
    Lindgren, Owe
    Pizzi, Antonio
    ENSTIB-UHP, Epinal.
    Magnetic resonance imaging of water distribution in welded woods2011In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 25, no 16, p. 1997-2003Article in journal (Refereed)
    Abstract [en]

    This study was performed for a better understanding of water effect on welded wood and improving its water resistance. In this article, we have also attempted to demonstrate the feasibility of using Magnetic Resonance Imaging technology to study water movement in welded woods. Water distribution in welded woods of Scots pine (Pinus sylvestris) and beech (Fagus sylvatica) was investigated by Magnetic Resonance Imaging. Axial specimens were cut from beech and sapwood of Scots pine in longitudinal direction of wood grain. Two pieces of each wood species were welded together by a linear vibration machine. Sub-samples measuring 30 mm × 20 mm × 100 mm were cut from the welded specimens for Magnetic Resonance Imaging. The results showed that weldline of Scots pine was more resistant to water than weldline of beech. Pine joint was still holding after 40 h immersion in water, while a rapid wetting of the beech joint resulted in breakage of the joint in even less than an hour. This preliminary study also showed that MRI is a powerful tool to measure water distribution in welded woods and highlighted the potential of this technique to enhance understanding of wood welding

1 - 29 of 29
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