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  • 51.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Effect of planing on warp in Scots Pine (Pinus sylvestris)2012In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, no 3, p. 154-161Article in journal (Refereed)
    Abstract [en]

    If a sawn board or plank that is warped after drying is being planed, the feed rollers and the pressure elements will more or less straighten the wood during planing. However, when the pressure is released, some degree of warp will recur since the wood will spring back. With a large amount of straightening, only the cross-sectional dimensions of the wood should be affected by the planing operation, leaving warp unchanged, while a small amount of straightening should have a larger impact on warp. The objective of this study was to evaluate how warp is affected by planing in an industrial planer with standard configuration. A total of 20 pine planks with the dry target dimension 50 mm×150 mm were selected, of which half were severely warped. The worst twist, crook and bow per two metres and maximum cup were measured both before and after planing.The planer in the experiment had different impacts on the different warp types. For the individual planks, twist was reduced by 25% and crook was reduced by about 20% on average. Although bow decreased for half of the planks, the total average change for individual planks was a slight increase. Cupping practically vanished.

  • 52.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    How Planer Settings Affect Timber Properties2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 4, p. 6432-6439Article in journal (Refereed)
  • 53.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    How planing affects warp2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Although planers and wood machining researchers have been around a long time, the interactions between planks and planers have been neglected in basic research. With a solid understanding of the movements of planks during planing, planers and planing strategies can be developed to reduce waste and improve the value yield.Cutting depths, changes in the amount of warp and cross-sectional shape were used to analyse the movements of the planks during planing, the alignment between the planks cross-sections and planers cutters and the improvement potential. The feeding roller in the planer intake had most control over the plank motion. Apart from cup reduction, the parts mostly affected by planing were the top and the butt end, where twist-induced misalignment between the cross-sections and the planers cutters resulted in skewed cross-sections and reduced rectangularity. By adjusting the cutting depths and in some cases the sawing oversize, planer misses could have been avoided but improvements in rectangularity would have required changes in the planer setting or planer design.This thesis increases the knowledge on how a 4-side planer works together with warp to affect 50 × 150 mm planks. For the 20 planks used in this study, the planer removed cup, it decreased the amount of twist and crook but had no effect on bow. The major factor reducing the rectangularity of the planed planks was twist. In the future, knowledge derived from this thesis can be used to create a simulation tool to model the behaviour of warped planks in a planer.

  • 54.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Impact of twist near the ends of planed timber2013In: Proceedings of the 21st International Wood Machining Seminar, 2013Conference paper (Refereed)
    Abstract [en]

    When sawn timber is planed, the timber is to some extent flattened by the feeding rollers and other pressure elements inside the planer, with the plank middle affected to a greater degree than the top and butt end. As a result, any twist present in rough timber influences the planing process in the proximity of the latter two areas. This is manifested primarily as reduced rectangularity in the affected zones of the planed timber, but also as an increased risk of planer misses. One way to avoid these unwanted features in the end product is to plane an excess length of timber, then cross-cutting to the required final length after planing.This study found low rectangularity to be a larger problem than planer misses, with the top end most affected. The study also indicates that simple models could be used to predict the size of the zone affected by twisting near the ends of planed timber, and thus also the length that must be removed in order to produce an acceptable cross-sectional shape throughout the length of planed timber.

  • 55.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Planing wood with twist2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    About half the total volume of sawlogs end up as sawn timber. The rest is lostdue to drying shrinkage or is turned into byproducts like wood chips, sawdustand shavings. As the raw material is a large expense for a sawmill, it is important to fully utilize the logs. The inherent properties of timber are such that warp, such as bow, cup, spring and twist, is inevitable, and extensive knowledge of whether and to what extent warp will appear is therefore important for managing the production. It is also important to develop strategies to handle warped timber, for example in the planing process.This thesis focuses on how twisted timber is affected by the planing process with regard to twist reduction, cross-sectional shape, planer misses and cutting depth. This was studied in three practical tests on sawn timber with differentapproaches. In one test, sawn pine timber with a large variation of twist withinthe group was planed with standard settings, and five evenly spaced crosssections along the length of the sawn timber were subjected to more detailed studies. In the second test, the main yield from spruce logs was planed. One sample board from each log was planed with the normal pressure settings of the planing mill, while the second sample was planed with a pressure either higher or lower than the normal settings. In this study, seven cross-sections were studied in more detail, three close to the top end, three close to the butt end, and one in the middle of the sawn timber. In the third test, sawn pine timber with a more moderate twist was planed with standard settings in another similar planer.

  • 56.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting twist after planing2015Conference paper (Refereed)
  • 57.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Rectangularity of planed Scots Pine (Pinus sylvestris) planks2013In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, no 2, p. 145-151Article in journal (Refereed)
    Abstract [en]

    This study deals with how warp affects the cross-sectional shape of planed planks. A total of 20 planks with dry target cross-sectional dimensions of 50×150 mm were planed to 45×145 mm. The rectangularity of five cross sections of every plank was measured before and after planing. The cutting depths were measured in 10 positions in the cross sections, and the angles between the planks and the cutters were calculated. Also, the warp, that is, twist, bow, crook, and cup, was measured before and after planing. All the studied properties pointed in the same direction. In terms of both rectangularity and angles of cut, the problems were larger in the top and butt ends of the investigated planks than in the intermediate parts, and the main reason for deviations from the desired result after planing was twist.

  • 58.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The effect of planing on shape deformations in pine2011In: Proceedings of the 20th international wood machining seminar, Skellefteå, 2011, p. 485-492Conference paper (Refereed)
  • 59.
    Axelsson, Ann
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Potential for increasing volume yield by reducing planing allowance2017In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 5, p. 301-306Article in journal (Refereed)
    Abstract [en]

    About half the volume of sawlogs ends up as sawn and planed timber. The rest is lost due to drying shrinkage or is turned into by products. As the raw material is a major expense for a sawmill, it is important to reduce waste.

    To investigate how much the volume yield in the production of sawn and planed timber could be increased by reducing the target dimensions in the sawing stage in a sawmill, two groups of sawn timber were planed under similar conditions. One group consisted of sawn Scots pine timber with a large variation in twist. The other group consisted of sawn Norway spruce timber planed under different pressure settings. Using X-ray images, the minimum dimension for avoiding planer misses was calculated for each board, to find the smallest green target dimension. This was compared to actual measured dimensions.

    It was found that most sawn timber had unnecessarily large dimensions, and it was also found that a reduction in the target dimensions could increase the volume yield for sawn and planed timber by more than 3 percentage points. Boards with large twist would however need a higher planing allowance. The effect of the planer pressure setting was negligible.

  • 60.
    Axelsson, Ann
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Potential for waste reduction when planing wood2014Conference paper (Refereed)
  • 61. Axelsson, B.
    et al.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lateral forces in wood cutting1991In: Proceedings of the Tenth International Wood Machining Seminar : Oktober 21 - 23, 1991 / [ed] Richard L. Lemaster, University of California at Berkeley , 1991Conference paper (Refereed)
  • 62. Axelsson, B.
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lateral forces in wood cutting due to momentary disturbances in the wood structure1992In: Better wood products through science : All-Division 5 conference "Forest Products", Nancy, France, August 23 - 28, 1992 ; [proceedings], ENGREF , 1992Conference paper (Refereed)
  • 63. Axelsson, B.
    et al.
    Lundberg, S.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cutting forces at and near a cutting edge1992In: Better wood products through science : All-Division 5 conference "Forest Products", Nancy, France, August 23 - 28, 1992 ; [proceedings], ENGREF , 1992Conference paper (Refereed)
  • 64.
    Axelsson, B.O.M.
    et al.
    Luleå tekniska universitet.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The use of gray scale images when evaluating disturbances in cutting force due to changes in wood structure and tool shape1991In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 49, no 12Article in journal (Refereed)
    Abstract [en]

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

  • 65.
    Axelsson, B.O.M.
    et al.
    Luleå tekniska universitet.
    Lundberg, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Studies of the main cutting force at and near a cutting edge1993In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 51, no 1, p. 43-48Article in journal (Refereed)
    Abstract [en]

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

  • 66.
    Aydemir, Deniz
    et al.
    Bartin University, Faculty of Forestry, Department of Forest Industrial Engineering, 74100, Bartin.
    Civi, Busra
    Bartin University, Faculty of Forestry, Department of Forest Industrial Engineering, 74100, Bartin.
    Alsan, Mizgin
    Bartin University, Faculty of Forestry, Department of Forest Industrial Engineering, 74100, Bartin.
    Can, Ahmet
    Bartin University, Faculty of Forestry, Department of Forest Industrial Engineering, 74100, Bartin.
    Sivrikaya, Huseyin
    Bartin University, Faculty of Forestry, Department of Forest Industrial Engineering, 74100, Bartin.
    Gunduz, Gokhan
    Bartin University, Faculty of Forestry, Department of Forest Industrial Engineering, 74100, Bartin.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Mechanical, Morphological and Thermal Properties of Nano-boron Nitride Treated Wood Materials2016In: MADERAS: Ciencia y Tecnología, ISSN 0717-3644, E-ISSN 0718-221X, Vol. 18, no 1, p. 19-32Article in journal (Refereed)
    Abstract [en]

    Thermal instability is the one of the most important disadvantages of wood since it begins to decompose at a low temperature (˃110 °C). Many scientists, past and present, have conducted studies aimed at improving the thermal stability of wood. The aim of this study was to impregnate wood with nano-sized boron nitride (NBN) to improve its thermal stability and to investigate the changes in the properties of Scots pine, Ash and Iroco woods after the impregnation. The effects of the impregnation with NBN also were investigated on the heat-treated woods. The impregnation was conducted with using empty-cell method (the Rueping method) in a chamber under a pressure of 6 bars for 1 hr. Densities at 0% and 12% moisture content (MC), mechanical properties, color changes, thermal stability, and scanning electron microscopy (SEM/EDX) analysis were determined. The test results showed that the impregnation of wood with NBN increased generally the flexural strength and elasticity of modulus at bending, but the NBN impregnation decreased generally the compression strength except for ACI, ATWI, IC, and ICI. It was also determined that the changes in density and color were statistically different after the impregnation. According to the SEM/EDX results, deposits of nano-sized boron nitride were found inside the cell wall and on the pits. But the deposits were also determined in inside structure of the wood with EDX analysis. Thermal stability in T10% and T50% of wood was found to improve after the impregnation with NBN. TG/DTG and DTA values for some samples were found to fluctuate due to the heterogeneous dispersion of the NBN in the wood.

  • 67.
    Aydemir, Deniz
    et al.
    Bartin University, Faculty of Forestry, Department of Forest Industrial Engineering, 74100, Bartin.
    Gündüz, Gökhan
    Bartin University, Faculty of Forestry, Department of Forest Industrial Engineering, 74100, Bartin.
    Aşık, Nejla
    Bartin University, Faculty of Forestry, Department of Forest Industrial Engineering, 74100, Bartin.
    Wang, Xiaodong (Alice)
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The Effects of Poly(vinyl acetate) Filled with Nanoclay and Cellulose Nanofibrils on Adhesion Strength of Poplar and Scots Pine Wood2016In: Drvna industrija, ISSN 0012-6772, E-ISSN 1847-1153, Vol. 67, no 1, p. 17-24Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNFs) and nano clay (NC) were selected to determine effects of different fillers on the characterization of poly(vinyl acetate) (PVA). Characterizations of the PVA composites obtained were studied by thermogravimetric analysis (TGA/DTG), scanning electron microscopy (SEM) and the lap joint shear strength (LJSS). The morphological studies revealed that some clumpings were observed in SEM pictures for 1%, 2%, and 4% wt loadings for CNFs and NC fillers. Dispersed particle orientation morphology and the wave sheets appear to be uniformly distributed on the surface of the composites. As seen as the effects of fillers on the thermal stability, the results showed that NC has a greater effect than CNFs, depending on the loading rates of fillers. Lap joint shear strength generally increased after adding CNFs and NC to PVA matrix. Thus, it can be said that PVA has higher bonding performance and can be used in applications requiring higher bonding strength.

  • 68.
    Bandura, Iryna
    et al.
    Tavria State Agrotechnological University, Department of technology of processi ng and storage of agricultural products.
    Myronycheva, Olena
    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.
    Assessment of Raw Plant material and Substrate for Efficient production of Oyster Mushrooms (Pleurotusostreatus (Jacq.) P. Kumm.)2016In: Ochrana drevín a dreva 2016: zborník recenzovaných vedeckých prác a abstraktov / [ed] Pavol Hlaváč , Zuzana Vidholdová, Zvolen: Technická univerzita vo Zvolene , 2016, p. 27-33Conference paper (Refereed)
    Abstract [en]

    Microbial analysis of raw materials and substrate during all phases of thermal processing revealed the most efficient methods for industrial mushroom cultivation. The aerobic fermentation in the upper layer is preferable if using long term stored material. The oyster mushroom strain HK-35 was used for testing. An increase in biological efficiency with 37% was found for aerobic fermentation in comparison with stream processing. From evaluation of temperature influence during pasteurization phase, the biological efficiency increased with 11% for tested temperature treatment at 74±3°С in comparison to the standard at 63±3°С.

  • 69.
    Bandura, Iryna
    et al.
    Tavria State Agrotechnological University .
    Myronycheva, Olena
    Tavria State Agrotechnological University .
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Anike, F.N.
    North Carolina A&T State University, Greensboro.
    Isikhuemhen, O.S.
    North Carolina A&T State University, Greensboro.
    Pretreatment of wheat straw and solid state fermentation improves yield and biological efficiency in Pleurotus ostreatus Jacq) P. Kumm. mushroom production2017In: Advances in medicinal mushroom science: Building bridges between Western and Eastern medicine : th International medicinal mushrooms conference : book of abstracts / [ed] Maria Letizia Gardano, Giuseppe Venturella, Palermo, Italy: University of Palermo , 2017, p. 41-43Conference paper (Refereed)
    Abstract [en]

    The pretreatment method for generating substrate for large scale production of oyster mushroom is critical for determining high yield and biological efficiency (BE). The aim of this study was to develop an optimal storage and pretreatment procedure for substrate used in oyster mushroom production. The effect of wheat straw substrate storage (outdoor- open air versus indoor- closed barn) and pretreatment (steam (SP) and hot water (HWP) pasteurization and solid state fermentation (SSF)) on substrate microbiological quality, mushroom yield/BE were investigated during the cultivation of Pleurotus ostreatus strain HK-35. The influence of temperatures used during solid state fermentation on BE was also investigated. There were significant changes among the parameters measured (moisture, total nitrogen, ash content, C/N ratio and total microbial count (CFU) between indoor and outdoor storage. The indoor storage gave higher values. With outdoor storage, CFU showed about 800 times increase. Among the substrate treatment methodstested (SP-control, HWP and SSF), SSF gave consistently higher fruit body yield and BE which ranged from 77-86% compared to the control which ranged from 40-53%. Also SSF conducted at higher temperature (74°C) gave higher BE of 81.2% compared to one conducted at lower temperature (63°C), which gave BE of 69.4%. We consider these findings to be useful in further studies on the redesign oF industrial production systems, which can make oyster mushroom production more profitable in Ukraine and beyond.

  • 70. Berg, Per
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Att detektera fibervinkel med 4 kameror på obarkade stockar: Resultat från vinterprov2004Report (Other academic)
  • 71.
    Berg, Sven
    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.
    Ekevad, Mats
    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.
    Crack influence on load-bearing capacity of glued laminated timber using extended finite element modelling2015In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, no 4, p. 335-343Article in journal (Refereed)
    Abstract [en]

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

  • 72.
    Berg, Sven
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Turesson, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Björnfot, Anders
    Faculty of Engineering, Department of Manufacturing and Civil Engineering, Norwegian University of Science and Technology, Gjøvik, Norway.
    In-plane Shear Modulus of Cross-laminated Timber by Diagonal Compression Test2019In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 3, p. 5559-5572Article in journal (Refereed)
    Abstract [en]

    Cross-laminated timber (CLT) is an engineered wood material that is used in the construction industry, e.g., for floors, walls, and beams. In cases where CLT-elements are used as shear walls, the in-plane-stiffness is an important property. For non-edge glued CLT, in-plane shear stiffness is lower than for edge-glued CLT. To evaluate the non-edge glued CLT panel’s in-plane shear modulus, the diagonal compression test and finite element (FE) simulation was used. FE-models with both isotropic and orthotropic material models were used to calculate the shear stiffness. The FE models using pure shear loads were used as a reference to determine the correct value of the shear modulus. To verify the FE simulations, diagonal compression tests were conducted on 30 CLT samples. A calibration formula was derived using the least square method for calculation of shear modulus. The formula gave accurate results. The results showed that FE simulations can reproduce the same shear stiffness as tests of non-edge glued 3-layer and 5-layer CLT panels.

  • 73.
    Berg, Sven
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Turesson, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Huber, Johannes Albert Josef
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Finite element analysis of bending stiffness for cross-laminated timber with varying board width2019In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Article in journal (Refereed)
    Abstract [en]

    ross laminated timber (CLT) is a wood panelling building system that is used in construction, e.g. for floors, walls and beams. Because of the increased use of CLT, it is important to have accurate simulation models. CLT systems are simulated with one-dimensional and two-dimensional (2D) methods because they are fast and deliver practical results. However, because non-edge-glued panels cannot be modelled under 2D, these results may differ from more accurate calculations in three dimensions (3D). In this investigation, CLT panels with different width-to-thickness ratios for the boards have been simulated using the finite element method. The size of the CLT-panels was 3.0 m × 3.9 m and they had three and five laminate layers oriented 0°–90°–0° and 0°–90°–0°–90°–0°. The thicknesses of the boards were 33.33, 40.0, and 46.5 mm. The CLT panel deformation was compared by using a distributed out-of-plane load. Results showed that panels with narrow boards were less stiff than wide boards for the four-sided support setup. The results also showed that 2D models underestimate the displacement when compared to 3D models. By adjusting the stiffness factor k88, the 2D model displacement became more comparable to the 3D model.

  • 74.
    Berglund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Efficient utilization of sawlogs using scanning techniques and computer modelling2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main question asked of the work described in this thesis was howthe sawing of logs into sawn timber can be performed more efficientlywith respect to the choice of raw material, volume and value yield in thesawing and in the grading of the sawn timber produced.The development of industrial computed tomography scanning providesinformation about the external and internal properties of a sawlogat production speed. This opens up new possibilities of controlling theflow of raw material early in the process and of optimizing the breakdownof each sawlog. Another use of industrial computed tomography scanningis for predicting the strength of sawn timber better than is possible withcurrent visual and machine strength grading equipment.A more traditional way of increasing sawmill profitability is by increasingthe volume of sawn timber. One way of doing this is by reducing thesaw blade thickness which results in less sawdust. With the use of thinnersaw blades however there is a risk that the saw blades become misalignedwhich in turn leads to saw mismatch, an unevenness seen on the surfaceof the sawn timber. In this work, attempts were made to automaticallymeasure and monitor saw mismatch in a sawmill during ongoing production.It is also possible for a sawmill to increase its profitability by measuresnot related to the sawing process. One such example is customer adaptationwhen delivering the sawn timber. Different customers use the sawntimber for different purposes and consequently have different requirements,which is why the sawn timber produced is graded and sorted before it isdelivered to the customer. In this work, an alternative method for gradingsawn timber more efficiently using a multivariate method was developedand evaluated.The following results have been obtained:Log breakdowns of 716 Scots pine logs and 750 Norway spruce logsthat had been scanned using computed tomography were simulated andthe rotational position of each log was optimized. The results showedan average relative value increase of 16% for appearance graded sawntimber compared to the conventional horns down position. When simulating log breakdowns of 677 Norway spruce logs with respect to visuallystrength graded sawn timber, an average relative value increase of 11%was obtained. The effect that errors in knot detection algorithms had ona breakdown optimization was also analysed when optimizing breakdownof 57 Norway spruce sawlogs. The results showed that errors in the knotdiameter had the most severe impact on the average relative value increaseof a log rotation optimization, followed by errors in the dead knot border.The smallest effect was observed in the case of errors in rotational positionof the knots.Computed tomography scanning can also be used in a sawmill for log sorting in relation to different end-uses of the sawn timber. A simulationsoftware for cross-cutting optimization based on computed tomographydata was developed and it was shown that there was a reasonable correlationbetween these results and the results of an industrial system. Sincethe developed software can be combined with log breakdown simulationsbased on computed tomography data, it is evident that computed tomographycan be used to identify logs that would result in a poor volume yieldin the subsequent cross-cut optimization.Destructive bending strength tests were performed on 113 pieces of Norway spruce sawn timber. Multivariate models for predicting the bending strength of the sawn timber were created using computed tomography data of the sawlogs from which the sawn timber originated. The results showed that computed tomography scanning of logs produced prediction models of bending strength with a higher accuracy than discrete X-rayscanning. The main advantage was the detailed knot information that could be used in the prediction models.A method to measure saw mismatch automatically in a sawmill basedon laser triangulation was developed and the measurements were well correlatedwith manual measurements of saw mismatch. When laser triangulationwas used to measure saw mismatch in a sawmill, a distinguishabletrend of increasing magnitude and frequency of saw mismatch was observed.Finally, ways in which the sawn timber in a sawmill could be gradedand sorted more efficiently was investigated. It was found that by using agrading method based on multivariate techniques it is possible to increasethe proportion of higher sawn timber grades by up to 10 percentage points,which may increase sawmill profitability.

  • 75.
    Berglund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Process control and production strategies in the sawmill industry2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The sawmill process itself is not complicated. What makes it complex is thediversity of the raw material, the logs that are processed in the sawmill, and thedivergent production with many different end products. In the sawmill variousnumber of measurement and scanning equipments are installed. These are usedfor controlling the various processes and for measuring how well they are carriedthrough.The main objective of this thesis is to build knowledge of how we can makethe sawing process, one of the main steps within the sawmill process, more efficientwith respect to both volume yield and value recovery by new equipmentand new production strategies. The intention has been that the conclusions inthis thesis can contribute to a knowledge base that can be of assistance in decisionsregarding control process parameters and production strategies for a sawmill.There is a possible economic saving by increased volume yield for the sawmillsif the saw kerf width can be reduced, but there is a fear that the presence andmagnitude of saw mismatch will be affected by this. Saw mismatch occurs on thesawn boards due to displacement in axial direction of the saw blades in doublearbor saw machines as a consequence of wear, heat or mechanical disturbance. Itis shown in this thesis that it was possible to measure saw mismatch automaticallyduring sawmill operation by laser triangulation and that the measurements werecomparable to manual measurements. It is also suggested how the presence andmagnitude of saw mismatch can be evaluated when measurements are carriedout in a sawmill.Another study addressed in the thesis is the consideration of applying analternative log rotation for each log than the in Scandinavia industrial praxis ofhorns down (log crook faced upwards). This possibility for a greater profit returncomes in question since the development of an industrial computed tomographyscanner makes the internal knot structure of the log available.Log breakdown simulations of about 600 Scots pine (Pinus sylvestris [L.])logs and 800 Norway spruce (Picea abies [L.] Karst.) logs mainly from differentgeographic locations in Sweden showed that there is a potential value increasewhen rotating each log for greatest profit return. The potential value increase wasdependent of the rotational error of the sawing machine and the price differencesbetween quality grades. For the 600 Scots pine logs and the 800 Norway sprucelogs in the study an increased average value increase of 13% was obtained ifapplying the rotation that maximizes the value of each log instead of the horns down position. An introduced rotational error of the sawing machine reducedthe value potential to 6%. There was a weak correlation between the log rotationthat maximizes the value of each log and the outer shape of the logs. This meansthat the outer shape can not be used as an indicator of how the log should berotated for greatest profit return.One subject of discussion in the thesis is also the importance of representativeinput data in order to make as general conclusions as possible. The Swedishstem bank has been an important factor in many studies made in the field ofwood technology. It is a well-documented data set and computed tomographyscanning of logs has made it possible to represent internal wood features in logbreakdown software. Since computed tomography scanning of logs is a time consuming process the number of scanned logs are relatively small. Now thatan industrial computed tomography scanner operating at production speed isentering the market this opens up new possibilities. Hopefully simulation studiesthat are performed on larger industrial data sets coming from logs processed inthe sawmills at a daily basis is not too far away.

  • 76.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Improved log rotation using information from a computed tomography scanner2013In: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 90, p. 152-158Article in journal (Refereed)
    Abstract [en]

    The development of an industrial computed tomography scanner for the sawmilling industry raises the question of how to find a production strategy that uses a computed tomography scanner in the sawmill production line to its full potential. This study was focused on a Scandinavian sawmill processing Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). The potential value increase when allowing an alternative log rotation other than the horns down position was investigated using a log breakdown simulation. The resulting data was analysed with respect to the size of the log rotational step, an introduced rotational error of the sawing machine and different price differences between the quality grades. It was also of interest to define the outer log properties that characterise the logs sawn for the greatest profit return close to the horns down position compared to logs sawn for a greater profit return in a different log rotation. Such characteristics can be used to reduce the number of degrees of freedom in an optimisation and consider instead other parameters, such as positioning and sawing pattern. Other defects such as pitch pockets, splits and rot are also of interest. The results shows that there is a potential value increase when applying the log rotation that maximises the value for each log instead of processing all logs in the horns down position. However, the potential value increase depends on the rotational error of the used sawing machine and the price differences between the quality grades. The log properties that differ between logs sawn for the greatest profit return close to the horns down position compared to a different log rotation are the bow height and the log taper. Unfortunately, predictability of log rotation for greatest profit return based on the outer properties of logs is poor. It is not possible to differentiate logs which would be sawn for the greatest profit return close to the horns down position from those where a different log rotation results in the greatest profit return, based only on their outer properties.

  • 77.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Oja, Johan
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Customer adapted grading of Scots pine sawn timber using a multivariate method2015In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 30, no 1, p. 87-97Article in journal (Refereed)
    Abstract [en]

    To define new grading rules, or to customize the ones in use in a rule-based automatic grading system of boards, is a time-consuming job for a sawmill engineer. This has the effect that changes are rarely made. The objective of this study was to continue the development of a method that replaces the calibration of grading rule settings by a holistic-subjective automatic grading, using multivariate models. The objective was also to investigate if this approach can improve sawmill profitability and at the same time have a satisfied customer. For the study, 323 Scots pine (Pinus sylvestris L.) boards were manually graded according to preferences of an important customer. That is, a customer that regularly purchases significant volumes of sawn timber. This manual grading was seen as reference grading in this work. The same boards were also scanned and graded by a rule-based automatic grading system, calibrated for the same customer. Multivariate models for prediction of board grade based on aggregated knot variables, obtained from the scanning, were calibrated using partial least squares regression. The results show that prediction of board grades by the multivariate models were more correct, with respect to the manual grading, than the grading by the rule-based automatic grading system. The prediction of board grades based on multivariate models resulted in 76-87% of the boards graded correctly, according to the manual grading, while the corresponding number was 63% for the rule-based automatic grading system.

  • 78.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Dahlquist, Simon
    SP Trä.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Detection of saw mismatch in double arbor saw machines using laser triangulation2013In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, no 4, p. 219-225Article in journal (Refereed)
    Abstract [en]

    In the sawing process of a sawmill, not only are the target sizes of great importance. The saw mismatch that may occur in double arbor saw machines is also an essential parameter that affects the planing allowance, as well as the quality of the sawn products. In this study, a newly developed measurement equipment for detecting saw mismatch in the green sorting line of a sawmill has been evaluated in an initial experimental test. The obtained data has been compared to manual measurements of saw mismatch with good results. Also, based on a small sample, 75 – 95% of the boards with a maximal saw mismatch exceeding 0.5 mm are detected. The rate of detection depends on the number of cameras used.

  • 79. Berglund, Anders
    et al.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Project: CT-Pro2012Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Projektet är finansierat av WoodWisdom-Net, VINNOVA, Fachagentur Nachwachsende Rohstoffe e. V. och medverkande företag. Syftet med projektet är att visa att det är möjligt att extrahera ut viktig och detaljerad information från en timmerstock med hjälp av en speciellt utvecklad röntgenskanner och sedan utnyttja denna information i produktionsstategier för att öka värdet i den träindustiella värdekedjan.

  • 80.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    An industrial test of measuring saw mismatch using laser triangulation2013Conference paper (Refereed)
    Abstract [en]

    Sawing yield is an important parameter for the sawmill profit. One way to increase the sawing yield is by a reduced saw kerf width, an adapted shrinking allowance, and a lower sawing allowance. The Swedish sawmills on the other hand see a risk of poorer sawing accuracy and sawing precision and at worst, more frequent saw blade failures. One problem with a reduced saw kerf width is the saw mismatch that may occur in double arbor saw machines. Saw mismatch occurs when the saw blades are displaced in axial direction with respect to each other due to wear, heat or mechanical disturbance. In this study the aim was to test the robustness of a laser triangulation unit used for measuring saw mismatch during sawmill operation. The aim was also to find a suitable response variable for saw mismatch which was evaluated by using the cant height, feed speed and average top diameter of the logs as predicting variables in a partial least squares regression. The goodness of prediction for each response variable was used to compare the response variables with each other. The results showed that the robustness when measuring saw mismatch by laser triangulation during ongoing sawmill production was satisfactory. The response variable with the best goodness of prediction (Q2 = 0.135) was defined using a sliding window with a size of 500 boards. Each element of the response variable was calculated as the share of boards within the sliding window exceeding a threshold value of 0.5 mm. This response variable was positively correlated with the cant height, feed speed and average top diameter of the log. Future work requires a designed experiment where the predicting variables are varied systematically and where the effect of characteristics and wear of the saw blades is also considered.

  • 81. Berglund, Anders
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Dahlquist, Simon
    SP Trä, Sverige.
    Projekt: Processuppföljning sågverk2013Other (Other (popular science, discussion, etc.))
  • 82.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Johansson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Skog, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Value optimized log rotation for strength graded boards using computed tomography2014In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 72, no 5, p. 635-642Article in journal (Refereed)
    Abstract [en]

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

  • 83.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Monitoring and Inspections of Timber Bridges: Moisture Content Measurements Adapted for Large Timber Constructions2017Doctoral thesis, comprehensive summary (Other academic)
  • 84.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Monitoring of a Timber Footbridge2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Alvsbacka Bridge was erected in the summer of 2011. During the planningof the construction researchers from LTU and SP Tr¨a designed ahealth monitoring system that constantly measures different parameterson the bridge. The motivation for health monitoring systems is several:Bridge safety, verification of the design and complement during inspections.Health monitoring of infrastructure is common, many bridges areequipped with health monitoring systems. Timber bridges are rarely monitored.This research project is looking to answer what type of sensorsis suitable for bridges in order to make them smart. The smartness ofthe bridge in this case is to help optimize bridge maintenance, assurethe service life and build knowledge about measurements on large timberconstructions. This thesis presents the monitoring system of the bridge,moisture content monitoring and studies the weather effects on the bridge.The monitoring system of ¨Alvsbacka Bridge consists of several differentsensor systems that continuously measure temperature, moisture content,movements, cable forces, wind velocity, wind direction. The monitoringsystem had some problems with sensors not communicating. Long termmoisture content monitoring show anticipated results and the bridge deckmovements are close to the theoretical values.

  • 85.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fjellström, Per-Anders
    Science Partner.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Factory Mounted and Retrofit Passive Resistance Sensors Adapted to Monitor Moisture Content in Timber Bridges2017In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 4, p. 7218-7227Article in journal (Refereed)
    Abstract [en]

    The biggest threats to the longevity of a timber bridge are rot and decay. Wood protection by design, inspections, and monitoring of the bridge for elevated moisture content will ensure that the full service life of the structure can be achieved. Today's sensors for moisture content measurements are limited in their functionality and range. This paper presents a sensor that can be both factory installed and retrofitted, which can measure the moisture content through the cross-section of the member in a timber bridge. The sensor has been mounted on Sundbron bridge during manufacturing and retrofitted on Gislaved bridge. The ensuing measurements helped to adjust a design flaw on Gislaved bridge. Monitoring of Sundbron showed that the bridge deck dried up after the bridge had been exposed to sleet and snow during the on-site assembly of the stress laminated bridge deck

  • 86.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fjellström, Per-Anders
    SP - Science Partner.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Long Term Evaluation of Factory Installed And Retro Fitted Moisture Content Sensor adapted for Timber Bridges2017In: Article in journal (Refereed)
  • 87.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fjellström, Per-Anders
    SP - Science Partner.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Resistance measurements to find high moisture content inclusions adapted for large timber bridge cross-sections2017In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 2, p. 3570-3582Article in journal (Refereed)
    Abstract [en]

    One challenge of monitoring and inspecting timber bridges is the difficulty of measuring the moisture content anywhere other than close to the surface. Damage or design mistakes leading to water penetration might not be detected in time, leading to costly repairs. By placing electrodes between the glulam beams, the moisture content through the bridge deck can be measured. Due to the logarithmic decrease of the resistance in wood as a function of electrode length, the model must be calibrated for measurement depth. Two models were created: one for electrode lengths of 50 mm and one for electrode lengths up to 1355 mm. The model for short electrodes differed by no more than 1 percentage points compared with the oven dry specimens. The model for long electrodes differed up to 2 percentage points for lengths up to 905 mm, and over that it could differ up to 4 percentage points.

  • 88.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Gustafsson, Anders
    SP Trätek.
    Pousette, Anna
    SP Trätek.
    Health monitoring of timber bridges2010In: Proceedings International Conference Timber Bridges: ICTB 2010 / [ed] Lasse Postmyr, Trondheim: Tapir Academic Press , 2010, p. 213-222Conference paper (Refereed)
  • 89.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Gustafsson, Anders
    SP Trätek, SP Technical Research Institute of Sweden, Skellefteå.
    Pousette, Anna
    Luleå tekniska universitet, SP Trätek.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Health monitoring of a cable-stayed timber footbridge2011Conference paper (Refereed)
  • 90.
    Björngrim, Niclas
    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.
    Multivariate Screening of the Weather Effect on Timber Bridge Movements2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 8890-8899Article in journal (Refereed)
    Abstract [en]

    Monitoring displacements and weather impact of complex structures such as a large cable stayed footbridge generates large amount of data. In order to extract, visualize and classify health-monitoring data to get a better comprehension multivariate statistical analysis is a powerful tool. This paper is a screening to evaluate if principal component analysis is useful on health monitoring data. Principal component analysis (PCA) and projections to latent structures by means of partial least squares (PLS) modeling were used to achieve a better understanding of the complex interaction between bridge dynamics and weather effects. The results show that principal component analysis (PCA) give good overview of the collected data, and PLS modeling show that winds from east and west best explain bridge movements.

  • 91.
    Björngrim, Niclas
    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, Xiaodong (Alice)
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Moisture Content Monitoring of a Timber footbridge2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 2, p. 3904-3913Article in journal (Refereed)
  • 92.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Laitila, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Forsman, Samuel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Model-based production for engineered-to-order joinery products2012In: World Conference on Timber Engineering, WCTE: Final Papers / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 697-701Conference paper (Refereed)
    Abstract [sv]

    När det levereras snickeri-produkter till byggindustrin som utvecklas mot kundorder, tar tillverkaren tar ofta ansvar för hela värdeflödet från offertförfrågan till slutmontering på byggarbetsplatsen. Det finns dock luckor i informationsflödet mellan varje aktör i den interna leveranskedjan, vilket leder till osäkerheter i kvalitet och påverkar processeffektiviteten. En del av problemen kommer från avsaknaden av rutiner för dokumentation av både ändringar och tillägg till den ursprungliga planen. För att kompensera för bristen på dokumentation, hantverkare förlita sig på sina färdigheter och erfarenhet, vilket ofta leder till onödiga och tidskrävande ad hoc-lösningar. Varje aktör i kedjan tillbringar tidåterupptäcka tidigare känd information istället för att hänvisa till dokumentationen. I denna artikel föreslås ett modell-baserad angreppsätt, som utnyttjar informations-och kommunikationsteknik (IKT) för att förbättra information- och kunskapsutbytet genom värdekedjan för bättre spridningav relevant information till berörda aktörer.

  • 93.
    Blomberg, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Mechanical and physical properties of semi-isostatically densified wood2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    When wood is densified through semi-isostatical compression in a Quintus- press at pressures up to 140 MPa, the material properties change. The cells are flattened, size is decreased and shape is changed, as a consequence of this the density is increased. Most properties of native woods are strongly correlated to the density. This is also true for densified wood. To understand the compression mechanisms plastic and elastic strains were studied at different pressures. Strength, density, anatomy and swelling were studied. Some of the methods used were: image analysis, computer tomography scanning (CT), scanning electron microscopy (SEM) and mechanical testing. Data was statistically analysed by linear regression and multivariate statistical methods. A big advantage of using semi-isostatic pressure is that wood of all dimensions, with knots and anomalous wood can be compressed without major checking. As the pressure is mediated through a flexible diaphragm the density becomes homogenous. Plain-sawn wood with inside-face to press-table gets the most homogenous density and the most rectangular shape. Strength is improved by the densification, especially the hardness, the bending and the axial compression strength. At water-soaking densified wood, the cell-shape recovers almost completely. This indicates the non-destructive character of the process. The swelling pressure, that develops when densified wood is restrained from dimensional change and then water-soaked, is more than twice as high as for native wood. The swelling can be reduced by deep impregnation with oil in combination with a surface lacquer.

  • 94.
    Blomberg, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Persson, Bengt
    Dalarna University.
    Swelling pressure of semi-isostatically densified wood under different mechanical restraints2007In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 41, no 5, p. 401-415Article in journal (Refereed)
    Abstract [en]

    Semi-isostatically densified and native wood samples of Scots pine and European birch were soaked in water. The swelling coefficients as well as the swelling pressure, that arose when the specimens were restrained in some way prior to the swelling, were measured using a universal testing machine equipped with a high resolution load-cell and an external extensometer. As densified wood swells, the native structure is almost restored and the swelling pressure became twice as high as for native wood in the most compressed directions (radial for pine and birch). That cell-shape recovery increases the swelling pressure can explain the problems with imbalance in laminated constructions where densified wood is used. The possibility to predict the swelling pressure from basic material properties was evaluated. The correlations between swelling pressure and material properties were strong enough to yield good predictive models

  • 95.
    Blomberg, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Persson, Bengt
    Dalarna University, Borlänge.
    Bexell, Ulf
    Dalarna University, Borlänge.
    Effects of semi-isostatic densification on anatomy and cell-shape recovery on soaking2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 1, p. 322-331Article in journal (Refereed)
    Abstract [en]

    Images obtained by scanning electron microscopy (SEM) helped to clarify the question as to how anatomy influences the deformation on compression and the spring-back of densified wood on water soaking. Transverse sections of Norway spruce (Picea abies), Scots pine (Pinus sylvestris), black alder (Alnus glutinosa), Swedish aspen (Populus tremula), European birch (Betula pubescens), European beech (Fagus sylvatica) and pedunculate oak (Quercus robur) were studied. Wood is reinforced with rays in the radial direction and with dense latewood in the tangential direction. When strained radially, rays buckle or tilt tangentially. Softwoods were mainly compressed radially, owing to low number of rays and since latewood is much denser than earlywood. The diffuse-porous hardwoods with low density variation between latewood and earlywood were mainly deformed tangentially, except birch, which has high density at the annual ring border and is mainly compressed radially. The ringporous hardwoods were relatively equally deformed in the radial and tangential directions because of the high number of rays and high latewood density. Moisture-induced springback (shape recovery) was proportional to the degree of compression. Rays remained deformed, which also influenced the surrounding wood. Longitudinal wood cells almost resumed their original shape. Wood with low density and a low degree of compression showed the highest structural recovery. Shearing deformation was particularly pronounced and permanent in woods with high strength anisotropy. Thin-walled and sheared cells, such as earlywood in softwood, tended to crack on compression. Cracks usually stopped at the middle lamella and had a lesser influence on strength properties than for lumen-to-lumen cracks. Copyright

  • 96.
    Blomqvist, L.
    et al.
    Linnéuniversitetet.
    Johansson, J.
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Moisture-induced distortion of laminated veneer products2013In: Proceedings of the 9th meeting of the Northern European network for wood science and engineering (WSE): September 11-12, 2013, Hannover, Germany / [ed] C. Brischke; L. Meyer, 2013, p. 178-183Conference paper (Refereed)
    Abstract [en]

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

  • 97.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Chipless machining: challanges in manufacture of laminated veneer products2015In: Proceedings of the 22nd International Wood Machining Seminar, IWMS 22. / [ed] Roger Hernández; Claudia B. Cáceres, Qubec City: Universite Laval , 2015, p. 155-164Conference paper (Refereed)
  • 98.
    Blomqvist, Lars
    et al.
    Linnӕus University, Department of Building Technology, Växjö, Sweden. RISE, Research Institute of Sweden.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Wood Processing and Biomaterials, Czech University of Life Sciences Prague, Prague, Czech Republic.
    Distortion in laminated veneer products exposed to relative-humidity variations: Experimental studies and finite-element modelling2019In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 2, p. 3768-3779Article in journal (Refereed)
    Abstract [en]

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

  • 99.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Basic knowledge of wood properties for improved performance of laminated Veneer products2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 549-556Article in journal (Refereed)
    Abstract [en]

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

  • 100.
    Blomqvist, Lars
    et al.
    Linnæus University, Forestry and Wood Technology.
    Johansson, Jimmy
    Linnæus University, Forestry and Wood Technology.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Modification of surface veneer to reduce damage in laminated veneer products during manufacturing2014In: Final Cost Action FP0904 Conference: “Recent Advances in the Field of TH and THM Wood Treatment” : May 19-21, 2014, Skellefteå, Sweden : book of abstracts / [ed] Mojgan Vaziri; Dick Sandberg, Skellefteå: Luleå tekniska universitet, 2014, p. 50-51Conference paper (Refereed)
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