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  • 1.
    Ah Shenga, Pedro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield2017Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, nr 4, s. 257-262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 2.
    Antti, Lena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Finell, Michael
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry, SE-90183 Umeå, Sweden.
    Arshadi, Mehrdad
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry, SE-90183 Umeå, Sweden.
    Lestander, Torbjörn A.
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry, SE-90183 Umeå, Sweden.
    Effects of microwave drying on biomass fatty acid composition and fuel pellet quality2011Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, nr 1-2, s. 34-40Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Drying of biomass for fuel pellet production is a time- and energy-consuming process. The objective of this study was to investigate not only whether microwave drying could be an alternative drying method but also whether the microwave treatment brings beneficial chemical properties into the biomass feedstock in terms of, for example, fatty acid composition and, further, whether this could be advantageous in the production of wood pellets. Microwave drying tests were conducted using fresh sawdust from pinewood as a biomass model. In these tests sawdust was dried from weight-based moisture content 0.47 to final moisture contents in the interval 0.08-0.14. The chemical composition, pellet-making and mechanical properties of the pellets were then investigated. It was shown that 0.5 kg sawdust could be dried within 40 min of microwave exposure. The effects of microwave treatment on the fatty and resin acid composition indicated that some changes occurred, but the total amounts were not significantly different from those in oven-dried samples. However, the microwave treatment of sawdust significantly improved pellet density and pellet strength. These results indicate new possibilities to alter fatty and resin acid composition and to improve particle bonding within fuel pellets.

  • 3.
    Axelsson, Ann
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Effect of planing on warp in Scots Pine (Pinus sylvestris)2012Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 3, s. 154-161Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    Axelsson, Ann
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Rectangularity of planed Scots Pine (Pinus sylvestris) planks2013Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, nr 2, s. 145-151Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Axelsson, Ann
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Potential for increasing volume yield by reducing planing allowance2017Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, nr 5, s. 301-306Artikel i tidskrift (Refereegranskat)
    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.

  • 6.
    Bachtiar, Erik Valetine
    et al.
    Fraunhofer-Institut für Holzforschung, Wilhelm-Klauditz-Institut WKI, Braunschweig, Germany.
    Niemz, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. ETH Zürich, Institute for Building Materials, Zürich, Switzerland; Department of Forestry and Biomaterials, Czech University of Life Sciences Prague, Prague, Czech Republic.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Department of Forestry and Biomaterials, Czech University of Life Sciences Prague, Prague, Czech Republic.
    Properties of adhesive films used in cultural assets2022Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 17, nr 2, s. 147-150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hygroscopic nature of wood leads to large moisture fluctuations in the material that may influence the mechanical performance of glued wood products. Adhesives based on bone, fish and hide have a long tradition for the gluing of wood and can be found in wooden structures in our cultural heritage. In this study, selected sorptive and mechanical properties of animal adhesives have been compiled and compared to those of synthetic polyurethane adhesives. Bone, fish and hide adhesives show a high moisture uptake at high relative humidity, which confirms the low moisture resistance of such adhesives. The modulus of elasticity and ultimate tensile strength of the films based on animal adhesives are considerably reduced when the moisture content is increased.

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  • 7.
    Berg, Sven
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Vaziri, Mojgan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Crack influence on load-bearing capacity of glued laminated timber using extended finite element modelling2015Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, nr 4, s. 335-343Artikel i tidskrift (Refereegranskat)
    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.

  • 8.
    Berg, Sven
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Turesson, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Huber, Johannes Albert Josef
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Finite element analysis of bending stiffness for cross-laminated timber with varying board width2019Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, nr 6, s. 392-403Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cross 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.

  • 9.
    Berglund, Anders
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Dahlquist, Simon
    SP Trä.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Detection of saw mismatch in double arbor saw machines using laser triangulation2013Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, nr 4, s. 219-225Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Björngrim, Niclas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Myronycheva, Olena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Fjellström, Per-Anders
    Timber Bridge Specialists Bureå, Sweden.
    The use of large-scale X-ray computed tomography for the evaluation of damaged structural elements from an old timber bridge2022Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 17, nr 6, s. 1028-1029Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper shows how timber structures in our cultural heritage can be evaluated by large-scale X-ray computed tomography (CT) to supplement visual inspection and conventional strength and biological degradation tests. Approx. 25 year old preservative-impregnated timber beams from a nearly 300-year-old timber bridge were replaced due to severe degradation. The condemned beams were examined by CT scanning, and three-point bending and decay tests were performed. The CT imaging gave a good overview of the internal structure of the beams, and features such as rot, nails and cracking could easily be detected and quantified. The CT images indicate that mild-steel nails from the decking of the bridge were the main cause of subsequent degradation by rot fungus. The load at breakage and the modulus of elasticity (MOE) values of the condemned beams were approx. half those of the undamaged reference beam. Large-scale CT scanning is a powerful tool for the non-destructive inspection of timber members in historical structures.

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  • 11.
    Blomqvist, Lars
    et al.
    Department of Forestry and Wood Technology, Linnaeus University, Växjö, Sweden.
    Johansson, Jimmy
    Department of Forestry and Wood Technology, Linnaeus University, Växjö, Sweden.
    Sandberg, Dick
    Department of Forestry and Wood Technology, Linnaeus University, Växjö, Sweden.
    Shape stability of laminated veneer products – An experimental study of the influence on distortion of some material and process parameters2013Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, nr 3, s. 198-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 12.
    Blomqvist, Lars
    et al.
    Forest and Wood Technology, Linnæus University.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Johansson, Jimmy
    Linnæus University, Forestry and Wood Technology.
    Influence of veneer orientation on shape stability of plane laminated veneer products2014Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, nr 4, s. 224-232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 13.
    Borko, Domen
    et al.
    Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
    Scharf, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Lin, Chia-Feng
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Humar, Miha
    Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Jones, Dennis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
    The potential of citric acid and glucose enhancing the reaction of wood with bicine and tricine2024Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To improve the resistance of wood to biological decay the Maillard reaction between introduced amines and wood cell-wall polymers can be utilised. However, initial studies in wood modification showed almost complete leaching of bicine and tricine from treated wood and the loss of beneficial effects. The objective of this study was to assess whether possible reactions of bicine or tricine with wood could be further enhanced and reaction products stabilised through the addition of glucose and/or citric acid. Thus, Scots pine sapwood specimens were impregnated with tricine or bicine, with or without glucose and citric acid, and then heated to a temperature of 160°C. The dimensional stability, degree of chemical leaching and mechanical properties were assessed. Overall, it was concluded that neither the presence of glucose nor citric acid did appear to enhance the reactivity of tricine or bicine. Anti-swelling efficiency (ASE) of 50% was observed for combined treatments of bicine/tricine and citric acid but the leaching resistance originated mainly from citric acid and glucose, with no indication for the retention of bicine or tricine. The presence of citric acid led to a strongly reduced modulus of rupture. 

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  • 14.
    Breinig, Lorenz
    et al.
    Forest Research Institute of Baden-Württemberg, 79100, Freiburg, Germany.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Brüchert, Franka
    Forest Research Institute of Baden-Württemberg, 79100, Freiburg, Germany Freiburg.
    Becker, Gero
    Forest Research Institute of Baden-Württemberg, 79100, Freiburg, Germany.
    Optimization potential for perception-oriented appearance classification by simulated sawing of computed tomography-scanned logs of Norway spruce2015Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, nr 4, s. 319-334Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wood, as a natural material, has favourable properties in both technical and aesthetic aspects. Due to its inherent variability,production of high-quality sawn timber demands adequate control of log conversion, which is feasible with computedtomography (CT) log scanning. Existing appearance grading rules for sawn timber might not fully reflect people’s visualperception of wood surfaces, and therefore, an alternative, more perception-oriented appearance classification could bebeneficial. An appearance classification of sawn timber based on partial least squares discriminant analysis (PLS-DA) ofknot-pattern variables was developed and tested. Knot-pattern variables derived from images of board faces were used intraining PLS-DA models against an initial classification of the board faces previously established by aid of cluster analysis.Virtual board faces obtained from simulated breakdown of 57 CT-scanned Norway spruce logs were graded according tothe developed classification. Visual assessment of the grading results indicated that the classification was largely consistentwith human perception of board appearance. An initial estimation of the potential to optimize log rotation, based on CTdata, for the established appearance grades was derived from the simulations. Considerable potential to increase the yield ofa desired appearance grade, compared to conventional log positioning, was observed.

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  • 15.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Wood material features and technical defects that affect yield in a finger joint production process2012Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 4, s. 167-175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A cost efficient process is the goal of all production, and each manufacturing step affects the material utilization and cost efficiency. There is high diversity in the inherent features of wood, and manufacturing steps must be able to handle this. The overall objective was to study the potential and problems in manufacturing production processes in terms of material utilization efficiency. The production of finger jointed bed sides was chosen as a study case, where the chain of production units are the sawmill, finger joint plant and furniture plant. This article describes the impact of raw material and wood defects that could affect the total yield. A total of 177 logs of three types were tested: butt, intermediate and fresh knot logs. The test material quality was detected and measured through all steps in the manufacturing chain. The results show differences between log types in down-grade causes, reject volume and final yield. Also, the test material showed high levels of defective components with process-related defects, which suggested the need for technical improvement in the manufacturing process. The intermediate log group showed the overall best result.

  • 16.
    Butylina, Svetlana
    et al.
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Martikka, Ossi
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Kärki, Timo
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Comparison of water absorption and mechanical properties of wood-plastic composites made from polypropylene and polylactic acid2010Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 5, nr 3-4, s. 220-228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study focuses on the water absorption and mechanical properties of composites made from softwood sawdust and plastics, such as virgin and recycled polypropylene and polylactic acid (PLA). The composites were processed by extrusion, and their properties were investigated by a water immersion test, mechanical tests and a cyclic test for moisture resistance. Scanning electron microscopy was used to study the morphology of the fracture surfaces of the composites. The composites made with recycled polypropylene had the lowest water absorption and thickness swelling of the studied composites. The PLA composites made with heat-treated sawdust showed the highest flexural strength. Of the polypropylene based composites, virgin polypropylene resulted in composites with higher flexural strength. The Charpy impact strength of the composites was found to have an inverse trend compared to flexural strength. Cyclic treatment of the studied composites resulted in 20-60% loss of flexural strength, depending on type of composite.

  • 17.
    Caprolu, Giuseppe
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Girhammar, Ulf Arne
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Källsner, Bo
    School of Engineering, Linnæus University, Växjö, Linnéuniversitetet, Linnaeus University, Växjö.
    Analytical models for splitting capacity of bottom rails in partially anchored timber frame shear walls based on fracture mechanics2017Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, nr 3, s. 165-188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Plastic design methods can be used for determining the load-carrying capacity of partially anchored shear walls. For such walls, the leading stud is not fully anchored against uplift and tying down forces are developed in the sheathing-to-framing joints and the bottom rail will be subjected to crosswise bending, leading to possible splitting failure of the rail. In order to use these plastic design methods, a ductile behaviour of the sheathing-to-framing joints must be ensured. In two earlier experimental programmes, the splitting failure capacity of the bottom rail has been studied. Two brittle failure modes occurred during testing: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the side surface of the bottom rail. In this article, a fracture mechanics approach for the two failure modes is used to evaluate the experimental results. The comparison shows a good agreement between the experimental and analytical results. The failure mode is largely dependent on the distance between the edge of the washer and the loaded edge of the bottom rail. The fracture mechanics models seem to capture the essential behaviour of the splitting modes and to include the decisive parameters. 

  • 18.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Lin, Chia-feng
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Schleicher, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Svensson, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Jones, Dennis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Mantanis, George I.
    Laboratory of Wood Science and Technology, Department of Forestry, Wood Sciences and Design, University of Thessaly, Karditsa, Greece.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Use of X-ray computed tomography for real-time studies of the fire progress in wood2023Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 18, nr 6, s. 2150-2152Artikel i tidskrift (Refereegranskat)
  • 19.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Lindgren, Owe
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Söderström, Ove
    c Professor Emeritus of Building Materials, Stockholm, Sweden.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Real-time wood moisture-content determination using dual-energy X-ray computed tomography scanning2019Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, nr 6, s. 437-444Artikel i tidskrift (Refereegranskat)
    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.

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  • 20.
    Cristescu, Carmen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Influence of pressing parameters on mechanical and physical properties of self-bonded laminated beech boards2015Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, nr 2, s. 205-214Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Five-ply self-bonded boards were obtained by pressing beech veneers parallel to the grain without additional adhesives, steam or pre-treatment. Fifteen different combinations of pressing parameters were tested, including temperature (200°C, 225°C and 250°C), pressure (4, 5 and 6 MPa) and pressing time (240, 300 and 360 seconds). Due to severe pressing conditions, the new product showed a higher density and different properties compared to a conventionally glued laminated wooden board. The self-bonding quality was assessed through dry shear strength tests, through a three-point bending test and a water-soaking test at 20°C. The dimensions in the cross section of the boards were measured after soaking in water. Results show that the choice of pressing parameters affects all the mechanical and physical properties tested. A statistical analysis revealed that the pressing temperature is the most influential parameter. Boards pressed at 200°C delaminated rapidly in water, whereas boards pressed at 225°C delaminated only at core-positioned layers after 48 hours and boards pressed at 250°C did not delaminate at all in water. Compared to panels pressed at lower temperatures, boards pressed at 250°C had the highest density, a higher shear and bending strength and a lower water absorption.

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  • 21.
    Cristóvão, Luís
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Sitoe, Rui
    Department of Mechanical Engineering , Eduardo Mondlane University, Maputo, Mozambique.
    Main cutting force models for two species of tropical wood2012Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 3, s. 143-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of the study was to evaluate the main cutting force for two species of tropical Mozambican wood and to develop predictive models. Cutting these hardwoods is difficult. Determination of cutting parameters is required to optimize cutting processes, machines and tools in the cutting operations. This determination would enable the forestry and wood sector to achieve higher financial results. Samples of a lesser-known wood species Pseudolachnostylis maprounaefolia (ntholo) and a well-known wood species Swartzia madagascariensis (ironwood) were machined in a test apparatus. A standard single saw tooth mounted on a piezoelectric load cell was used to evaluate the main cutting force. Data were captured using an A/D converter integrated with National Instruments LabVIEW software. The measured signals were recorded at a sampling frequency of 25 kHz. The experimental set-up used response surface methodology for developing predictive models. The experimental clearly determined the relationship between the main cutting force and edge radius, wood density, rake angle, chip thickness, moisture content (MC) and cutting direction (CD). Among the studied variables, chip thickness and CD had the highest effect on the main cutting force level while wood density, MC and rake angle had the lowest effect.

  • 22.
    Cristóvão, Luís
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Lhate, Inácio
    Department of Wood Science, Swedish University of Agricultural Science, SE-750 07, Uppsala, Sweden.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sitoe, Rui
    Department of Mechanical Engineering, Eduardo Mondlane University, Maputo, Mozambique.
    Tool wear for lesser known tropical wood species2011Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, nr 3, s. 155-161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigated the relationship between tool wear and some chemical and physical properties for four different Mozambican lesser known tropical species,: Pseudolachnostylis maprounaefolia (ntholo), Sterculia appendiculata (metil), Acacia nigrescens (namuno) and Pericopsis angolensis (muanga). Tool wear is an important aspect for sawmilling and for the woodworking industry. For Mozambique, the utilization of available lesser known wood species will help to increase domestic industry and the economic usage viability of sustainable forest management. A set of experiments was performed on a shaper with a mechanical feed mechanism. Tools of a cemented carbide grade for woodworking were used, and the cutting parameters were fixed. Edge recession and tool wear radius were measured for monitoring tool wear. The wear mechanism was investigated using a scanning electron microscope. The experimental results showed that the chemical properties of the wood species have a great effect on tool wear. Wood silica content was the most important factor affecting tool wear. Wood density and extractives had a low influence on tool wear. The highest tool wear was observed in ntholo, which also had the highest ash and silica contents. A single parameter for evaluation of tool wear was not sufficient to describe the amount of total tool wear.

  • 23.
    Dagbro, Ola
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Torniainen, Petteri
    Department of Forest Products, Swedish University of Agricultural Sciences, Uppsala.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Colour responses from wood, thermally modified in superheated steam and pressurized steam atmospheres2010Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 5, nr 3, s. 211-219Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, two different methods were used to produce thermally modified wood. One was carried out in a typical kiln drying chamber using superheated steam (SS) and the other used pressurized steam in an autoclave cylinder (PS). Overall, both processes followed the same principles and the wood was not treated with any chemicals. Two wood species were studied, Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). Treatments in the autoclave were carried out under pressure using temperatures of 160°C, 170°C and 180°C. Temperatures of 190°C and 212°C were used in treatments in the chamber at normal air pressure. The colour was measured using L*C*H colour space. Results for both species showed that similar L* (lightness) can be reached at lower (20-308C) temperatures using PS compared with SS treatment. The hue angle of PS-treated wood was smaller than that of SS-treated wood. No significant difference in C* (chroma) was detected. The difference in E value between PS- and SS-treated wood was smaller for Norway spruce than for Scots pine. The residual moisture content was about 10% higher in wood treated by the PS process compared with the SS process

  • 24.
    Deliiski, Nencho
    et al.
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Niemz, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Institute for Building Materials, ETH Zürich, Zürich, Switzerland.
    Angelski, Dimitar
    Department of Furniture Production, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Campean, Mihaela
    Department of Woodprocessing and Design of Wood Products, Faculty of Furniture Design and Wood Engineering, Transilvania University of Braşov, Braşov, Romania.
    Vitchev, Pavlin
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    An engineering approach for calculating the energy required for defrosting and subsequent heating of frozen wood during thermal treatment2024Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Artikel i tidskrift (Refereegranskat)
  • 25.
    Deliiski, Nencho
    et al.
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Niemz, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Institute for Building Materials, ETH Zürich, Zürich, Switzerland.
    Angelski, Dimitar
    Department of Furniture Production, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Tumbarkova, Natalia
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    A methodology for computing the relative icing degrees of logs stored in an open warehouse at ambient air temperature in winter2021Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 16, nr 6, s. 421-428Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes a methodology for mathematical modeling, computing, and research of two mutually connected problems: 2D non-stationary temperature distribution in logs stored for a long time in an open warehouse at periodically changing ambient air temperature in winter and change in the icing degrees of the logs during this time. Mathematical descriptions of the periodically changing ambient air temperature and of three types of relative icing degree of the logs that result under the influence of that temperature have been presented. These descriptions are introduced in coupled 2D non-linear mathematical models of the heat distribution in logs during their freezing and defrosting. The paper presents solutions of the models with explicit form of the finite-difference method. Results from a simulative investigation of the 2D non-stationary temperature distribution, average mass temperature, and three types of icing degree of beech logs with industrial dimensions (diameter of 0.4 m and length of 0.8 m), moisture content of 0.6 kg·kg−1, and initial temperature of 0°C during their 5 days and nights alternating freezing and defrosting in an open warehouse at sinusoidal change of the ambient air temperature with various initial values below −5°C and different amplitudes are graphically presented and analyzed. 

  • 26.
    Deliiski, Nencho
    et al.
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Niemz, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Institute for Building Materials, ETH Zürich, Zürich, Switzerland.
    Angelski, Dimitar
    Department of Furniture Production, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Tumbarkova, Natalia
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    An approach for computing the specific heat capacities of logs stored for a long time in an open warehouse2022Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 17, nr 5, s. 376-385Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes an approach for computing the specific heat capacities of logs stored for long in an open warehouse. It includes the heat capacities of the wood of non-frozen and frozen zones in the logs and of both the frozen free and bound water in these zones, also the capacities formed by the release of the latent heat of both the free and bound water during their crystallization, as well as the effective specific heat capacities of logs stored in an open warehouse at periodically changing air temperature. The approach is based on the solutions of 2D models of the temperature distribution in logs during their alternating heating and cooling. Results from a simulative study of 2D unsteady temperature distribution and all types of the specific heat capacities of beech logs with a diameter of 0.4 m, length of 0.8 m, moisture content of 60%, and initial temperature of 0°C and 20°C during their 5 days and nights continous alternating heating, cooling, freezing and defrosting in an open warehouse at sinusoidal change of the ambient air temperature with various initial and different amplitudes in the range from –25°C to 40°C are graphically presented and analyzed.

  • 27.
    Deliiski, Nencho
    et al.
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Niemz, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Institute for Building Materials, ETH Zürich, Zürich, Switzerland.
    Dzurenda, Ladislav
    Department of Woodworking, Faculty of Wood Science and Technology, Technical University in Zvolen, Zvolen, Slovakia.
    Vitchev, Pavlin
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Angelski, Dimitar
    Department of Furniture Production, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    An approach for computing the thermal balance and energy consumption of concrete pits during boiling of frozed logs for veneer production2023Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 18, nr 6, s. 2153-2163Artikel i tidskrift (Refereegranskat)
  • 28.
    Deliiski, Nencho
    et al.
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Niemz, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Institute for Building Materials, ETH Zürich, Zürich, Switzerland.
    Vitchev, Pavlin
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Angelski, Dimitar
    Department of Furniture Production, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Tumbarkova, Natalia
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Computing the duration of regimes for autoclave steaming of frozen wooden prisms under variable operating conditions in veneer production2022Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 17, nr 6, s. 451-458Artikel i tidskrift (Refereegranskat)
  • 29.
    Deliiski, Nencho
    et al.
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Niemz, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Institute for Building Materials, ETH Zürich, Zürich, Switzerland.
    Vitchev, Pavlin
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Angelski, Dimitar
    Department of Furniture Production, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Tumbarkova, Natalia
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Mathematical description of the operating temperature in regimes for autoclave steaming and subsequent air conditioning of wood2023Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 18, nr 5, s. 1816-1826Artikel i tidskrift (Refereegranskat)
  • 30. Dvinskikh, Sergey V.
    et al.
    Furó, István
    Sandberg, Dick
    Söderström, Ove
    Kungliga tekniska högskolan, KTH.
    Moisture content profiles and uptake kinetics in wood cladding materials evaluated by a portable nuclear magnetic resonance spectrometer2011Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, nr 3, s. 119-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 31.
    Ekevad, Mats
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Cristovao, Luis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Marklund, Birger
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Lateral cutting forces for different tooth geometries and cutting directions2012Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 3, s. 126-133Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lateral (sideways) cutting forces were measured for 6 different tooth geometries when cutting green spruce and pine heartwood. The teeth were intended for use on circular saw blades for the rip sawing of logs. The 6 tooth geometries were designated straight, pointed, bevelled, rounded, trapezoidal and hollowed out. Cutting speed was 15 m/s, feed per tooth was 0.3 mm and the cutting directions were 90°–90° (rip sawing) and 90°–0° (milling), with two different variants of growth ring angles for each direction. The tools were tested in sharp conditions, in dull conditions and in a dull condition with a corner broken off. All lateral forces were small when cutting with sharp teeth, except for the rounded and bevelled teeth. Lateral forces increased with wear, except for a period of initial wear where the lateral forces were reduced. High wear resulted in greater lateral forces, most probably due to unsymmetrical wear. Growth ring direction did not generally affect lateral forces. The teeth with acute corners, which were the straight and hollowed out tooth, were most sensitive to a broken off corner. The lateral forces in the cases of wood cutting at 90°–90° increased less with wear compared to the 90°–0° cases.

  • 32.
    Ekevad, Mats
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Cristovao, Luis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Marklund, Birger
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Wear of teeth of circular saw blades2012Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 3, s. 150-153Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Measured wear data is presented for three different carbide grades. The data were collected during rip sawing wood with a double arbour saw. The purpose of the test was to determine the suitability of different grades for sawing frozen timber. A set of circular saw blades of diameter 350 mm was equipped with teeth comprised of three different cemented carbide grades, denoted A, B and C. The double arbour saw was equipped with six saw blades for cutting two centre boards and two side boards. The six saw blades with different teeth were mounted in a mixed manner on the arbours, and after sawing a number of logs the wear of teeth was measured. The thickness of boards was also measured and the standard deviation was calculated. The results showed that grade A had the highest wear and grades B and C the lowest wear. There was no significant edge damage during the tests. Grade C did not suffer problems of chipping from cutting edges and was found to be suitable for sawing frozen timber. The thickness standard deviations were constant at about 0.2 mm, and not a function of the number of logs sawn.

  • 33.
    Ekevad, Mats
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Guo, Xiaolei
    Nanjing Forestry University, Faculty of Material Science & Engneering, Nanjing Forestry University.
    Li, Rongrong
    Nanjing Forestry University, Nanjing Forestry University, Faculty of Material Science & Engneering.
    Öhman, Micael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Curve sawing effects on board dimensions when rip-sawing with a circular saw blade2016Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 11, nr 3, s. 135-141Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Curve sawing means advantages for yield and quality of sawn boards. However, for circular saw machinery deviations of saw kerfs give losses of valuable board volume. Deviations give thinner boards but also slight cupping of the cross sections. Theoretical calculations show that even with moderate (large) curve radii, these saw kerf deviations are typically 0.2–0.6 mm for normal circular saw machinery and Swedish log material. The test sawing reported here was made in order to give experimental values that can be compared to theoretical values. Fifty normal logs and 50 curved with top diameter 236–248 mm were cut with sawing pattern 3X with center boards 51 × 149 mm. The average curve radius of the curved cants that were cut in the resaw was 132 m (bow height 19 mm) and the theoretical saw kerf deviation for this radius is 0.31 mm. The experimental results show that the thickness reduction at the measuring points for curve sawn boards compared to straight sawn boards was in average 0.19 mm to be compared with the theoretical value of 0.20 mm. Cupping was more difficult to measure but results seem to agree well between theory and experiments.

  • 34.
    Ekevad, Mats
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Lundgren, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Flodin, Jens
    SP Technical Research Institute of Sweden, Wood Technology, Skeria 2, SE-931 77, Skellefteå, Sweden.
    Drying shrinkage of sawn timber of Norway spruce (Picea abies): Industrial measurements and finite element simulations2011Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, nr 1-2, s. 41-48Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Industrial measurements of green and dry cross-section dimensions were performed for 189 Norway spruce (Picea abies) centre-yield boards with dry dimensions 51 times 149 mm. Two, three or four boards were sawn from each log, depending on log size. Different approaches were used for simulations of cross-section shrinkage during drying. An analytical model, an elastic, an elastic- mechanosorptive and an elastic- plastic finite element simulation model were tested. Thickness and width shrinkage and deformation were simulated. Shrinkage results were compared with each other and with the experimental results. All simulation models gave roughly the same degree of agreement with experimental results except for the centre board from the three-board sawing pattern. For the other boards, the analytical model was not generally better or worse than the results from the finite element models. Shrinkage deformations in finite element models that included mechanosorption or plasticity were nearly the same as for the elastic finite element model except for the centre board of the three-board sawing pattern. The mechanosorptive model was the best model for the shrinkage of the centre board of this sawing pattern except for mid-thickness shrinkage. Comparison between the different finite element simulation models of stresses in the centre board revealed large differences.

  • 35.
    Ekevad, Mats
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Marklund, Birger
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Wood-chip formation in circular saw blades studied by high-speed photography2012Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 3, s. 115-119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Films of wood-chip formation were captured with a high-speed camera during rip sawing of wood with a circular saw blade. The saw blade diameter was 400 mm and the rotational speed was 3250 rpm. The saw blade had four teeth with rake angles of 0°, 10°, 20° and 30° to ascertain the influence of different rake angles. Wooden boards were cut along the side so that the camera could record the cutting sequence without any interference from material between the cutting teeth and the camera. Tests were made for green, dry and frozen green pine boards, for both counter-cutting and climb-cutting cases. In addition, some Mozambican wood species were cut. The films, recorded at 40,000 frames s−1, show the cutting sequence along the trajectory of the tooth in question and the creation of the wood chip. Details such as the compression of the wood chip in the gullet, the movement of the wood chip inwards and outwards in the gullet and finally the exit from the gullet are visible. The chip size and chip movement depend strongly on the rake angle and on whether the wood is green, dry, frozen or unfrozen.

  • 36.
    Ekevad, Mats
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Salin, Jarl-Gunnar
    Grundberg, Stig
    Nyström, Jan
    Grönlund, Anders
    Modelling of adequate pretwist for obtaining straight timber2006Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 1, nr 2, s. 76-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic-ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists

  • 37. Elustondo, Diego
    Lumber quality model: The theory2010Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 5, nr 3-4, s. 162-172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new model for predicting moisture content, distortion and shrinkage distribution after lumber drying has been designed, implemented and tested. The model was implemented using Monte Carlo simulation, and it involves three empirical equations that were developed on the basis of experimental data. The model is referred as the Lumber Quality Model, and it is designed to be calibrated by knowing the initial and final moisture content, distortion and shrinkage distribution for a reference drying run. After calibration, the model can be used to predict the same information for other hypothetical drying scenarios. The present study explains the theoretical aspects of the model and the methodology for implementation. The model was validated with experimental data measured in a laboratory kiln. A full-scale industrial validation will be reported in a future paper.

  • 38. Elustondo, Diego
    et al.
    Oliveira, Luiz C De S
    FPInnovations-Wood Products, Vancouver, British Columbia.
    Moisture content target optimization in lumber drying2011Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, nr 4, s. 190-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A Lumber Quality Model developed to predict lumber grade after drying was applied and validated in industry. The model was calibrated with a 198-piece lumber package that was dried at a local sawmill in British Columbia, Canada, and 30 sawmill grade reports were recorded from 2008 to 2010. The calibrated model was then used to predict the target moisture content that would result in the maximum lumber value. It was predicted that lumber value should increase by approximately 17 CAD (Canadian dollars) m -3 if the target moisture content were reduced from the historic 17% to an optimum of approximate 13%. The sawmill implemented the recommendations and the predictions were validated with another seven industrial drying runs

  • 39.
    Forsman, Samuel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Laitila, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Applicability of as-built 3-D sensing technologies for improved efficiency when supplying joinery products2016Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With currently used surveying methods, the on-site assembly of joinery products often consumes half the supplier budget. Due to spatial uncertainties, the manual product-to-room fitting of components is a major consumer of time and labour resources. With reliable as-built construction site geometrical information, this fitting could be moved to the design stage early in the supplier process. In this study, the currently used manual surveying methods were compared with two different 3-D sensing surveying methods, a portable wire-bound coordinate measuring machine (CMM) and a laser-scanning machine. The comparison evaluates the applicability of the on-site surveying methods and their potential for improving the current surveying process, moving the product-to-room fitting to the design stage. Results show that currently used manual surveying methods leave uncertainties regarding the dimensions of a construction site and are insufficient for moving the product-to-room fitting to the design stage. CMM surveying has the potential to supply coordinate registrations on a par with desired accuracy requirements, but it has limitations at the practically possible detailing level. Laser scanning seems to be applicable for the surveying for a joinery products supplier, but the accurate and detailed 3-D reconstruction of the point cloud data is difficult and requires extensive processing. It can be concluded that the concept of digitized measurement of the as-built spatial dimensions of a construction site to enable product-to-room during the design stage has the potential to succeed with currently available digitizing technologies, but that some challenges remain.

  • 40.
    Forsman, Samuel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Laitila, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Three-dimensional, as-built site verification in supplying engineer-to-order joinery products to construction2015Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, nr 4, s. 353-367Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With currently used surveying methods, the on-site assembly of joinery products often consumes half the supplier budget. Due to spatial uncertainties, the manual product-to-room fitting of components is a major consumer of time and labour resources. With reliable as-built construction-site geometrical information, this fitting could be moved to the design stage early in the supplier process. In this study, the currently used manual surveying methods were compared with two different three-dimensional (3-D) sensing surveying methods, a portable wire-bound coordinate measuring machine (CMM) and a laser-scanning machine. The comparison evaluates the applicability of the on-site surveying methods and their potential for improving the current surveying process, moving the product-to-room fitting to the design stage. Results show that currently used manual surveying methods leave uncertainties regarding the dimensions of a construction site and are insufficient for moving the product-to-room fitting to the design stage. CMM surveying has the potential to supply coordinate registrations on a par with desired accuracy requirements, but it has limitations at the practically possible detailing level. Laser scanning seems to be applicable for the surveying for a joinery products supplier, but the accurate and detailed 3-D reconstruction of the point-cloud data is difficult and requires extensive processing. It can be concluded that the concept of digitized measurement of the as-built spatial dimensions of a construction site to enable product-to-room during the design stage has the potential to succeed with currently available digitizing technologies, but that some challenges remain

  • 41.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Log Sawing Position Optimization using Computed Tomography Scanning2014Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, nr 2, s. 110-119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When disjoining a log, several factors affect the value of the sawn timber. There are log features, such as outer shape, knots, rot, and so on. There are also sawing parameters, such as sawing pattern, log position, and so on. If full information about log features is available, sawing parameters can be adapted in order to maximize product value in sawmills. This is soon possible, since computed tomography (CT) scanners for the sawmill industry are being realized. This study aimed at investigating how CT data can be used to choose rotational position, parallel displacement, and skew of sawlogs, to maximize the value of the sawn products. The study was made by sawing simulation of 269 CT scanned logs of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] H. Karst.). The results showed that value recovery could be improved by 13% in average, compared to a sawing position based on log outer shape, and 21% compared to sawing logs centered and horns down. It can be concluded that a CT scanner, used in a sawline to optimize sawing parameters, has a large potential for increasing value recovery and thus profit.

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  • 42.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Persson, Fredrik
    SP Trä.
    Axelsson, Ann
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ah Shenga, Pedro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Rotational Position of Curved Saw Logs and Warp of the Sawn Timber2014Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, nr 1, s. 31-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the development of scanning technology in sawmills, it is possible to optimise log rotational position when sawing. However, choosing a different rotational position than horns down might be detrimental for the board shape after drying, especially for curved logs. Thus, there is a need to investigate at what level of log curve it is possible to freely rotate logs without causing board warp. This study was carried out through a test sawing that was conducted at a sawmill situated in the middle of Sweden. The tests were made on 177 Norway spruce logs, with varying amount of curve. Half of the logs were sawn in the horns-down position, half were sawn rotated perpendicular to horns down. Log shape and warp of the dried boards were measured. The results indicated a relationship between board spring, log curve and choice of rotational position. Furthermore, board bow was related to log curve but not rotational position. It can be concluded that for straight logs, with a bow height of less than 15 mm, an unconventional rotational position does not cause excess spring in the boards. Bow and twist are not affected by the rotational position at all.

  • 43.
    Fredriksson, Maria
    et al.
    Division of Building Materials, Lund University.
    Lindgren, Owe
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    End grain water absorption and redistribution in slow-grown and fast-grown Norway spruce (Picea abies (L.) Karst.) heartwood and sapwood2013Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, nr 4, s. 245-252Artikel i tidskrift (Refereegranskat)
    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.

  • 44.
    Han, Lei
    et al.
    Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Koper, Slovenia; InnoRenew CoE, Izola, Slovenia.
    Kutnar, Andreja
    Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Koper, Slovenia; InnoRenew CoE, Izola, Slovenia.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Creep behaviour of densified European beech and Scots pine under constant climate2022Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 17, nr 6, s. 1025-1027Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermo-hydro-mechanical (THM) densification is a well-known procedure for improving the properties of low-density wood species, but the long-term behaviour of the densified wood under constant load has not been reported and may restrain its use in construction. This study has investigated the influence of THM densification on the creep behaviour in bending of beech and pine under constant climatic conditions. The specimens were loaded in three-point bending at applied stress level of 35% of the ultimate strength for 14 days at 20 +/- 2 °C and 65 +/- 5% relative humidity (RH), and the bending deformation was registered. The THM densification doubled the density, increased the modulus of elasticity and the modulus of rupture, and reduced the equilibrium moisture content and creep compliance. The results demonstrate that THM densification can be an effective method to improve the short-term and long-term performance of wood in constructions.

  • 45.
    Han, Lei
    et al.
    InnoRenew CoE, Izola, Slovenia; Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Koper, Slovenia.
    Schwarzkopf, Matthew
    InnoRenew CoE, Izola, Slovenia; Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Koper, Slovenia.
    Pečnik, Jaka Gašper
    InnoRenew CoE, Izola, Slovenia; Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Koper, Slovenia.
    Rojas-Alva, Ulises
    Department of Fire-Safe Sustainable Built Environment, Slovenian National Building and Civil Engineering Institute (ZAG), Logatec, Slovenia.
    Lucherini, Andrea
    Department of Fire-Safe Sustainable Built Environment, Slovenian National Building and Civil Engineering Institute (ZAG), Logatec, Slovenia.
    Kutnar, Andreja
    InnoRenew CoE, Izola, Slovenia; Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Koper, Slovenia.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Exploratory study on the bending performance of thermo-hydro-mechanically densified Scots pine (Pinus sylvestris L.) at elevated temperatures2024Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 19, nr 3, s. 829-832Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermo-hydro-mechanical (THM) densification is a well-known wood modification procedure for improving the mechanical properties of low-density wood species, but its performance at elevated temperatures is not well understood. The objective of this study was to determine the bending behaviour of densified Scots pine at elevated temperatures. A total of 48 specimens (200 mm (longitudinonal) × 20 mm (radial) × 20 mm (tangential)) were tested to investigate the bending performance under constant temperatures at 25, 50, 125 and 175°C, respectively. It was found that the modulus of rupture (MOR) and modulus of elasticity (MOE) of both un-densified and densified pine decreased with increasing temperature. However, the densified wood exhibited more brittle shear failure but retained higher MOR and MOE than the untreated specimens treated at the same temperature level. In general, the results demonstrate that densification can be a potentially effective method to retain the mechanical properties of wood at elevated temperatures, thereby having a potential maintain the load-bearing capacity during and after fire.

  • 46.
    Hansson, Lars
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Cherepanova, Ekaterina
    Luleå tekniska universitet.
    Determination of wood moisture properties using a CT-scanner in a controlled low-temperature environment2012Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 2, s. 87-92Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of the present work was to examine an advanced image-processing algorithm for moisture content (mc) calculation and also to use this algorithm to analyse moisture loss data for low temperature drying. Since wood starts to shrink below the fibre saturation point during drying, the geometrical shape of the wood piece will change. The dry wood image was thoroughly transformed to the shape of the wet wood image prior to calculating the dry weight mc. The results show that the algorithm for the dry weight mc on density data from the CT-scanning during low-temperature drying in the climate chamber is a powerful tool for analysing the moisture loss inside the wood piece. This method can make it possible to get a higher quality on the product

  • 47.
    Hansson, Lars
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Faculty of Engineering and Natural Sciences, Norwegian University of Science and Technology (NTNU), Ålesund.
    Couceiro, José
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Fjellner, Bengt-Arne
    Luleå tekniska universitet, Verksamhetsstöd, IT-Service.
    Estimation of shrinkage coefficients in radial and tangential directions from CT images2017Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, nr 4, s. 251-256Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of the present work was to use the displacement information generated from the spatial alignment in order to compute wood shrinkage in the radial and tangential directions in computed tomography (CT) images, and to compare the results with those obtained with computer-aided design software on the same images. To estimate the shrinkage coefficients from tomography images, wood specimens in the green state, equilibrium moisture content 15% and 8% state and oven dry condition were scanned. Specimens were taken from Norway spruce and Scots pine logs. The root-mean-square-error calculations showed acceptable small differences between the two measuring methods, which means that the algorithm is a useful tool for estimating the shrinkage coefficients in radial and tangential direction from CT images. This provides an image processing tool to monitor the dimensional changes during the drying and heat treatment process. 

  • 48.
    Hassani Khorshidi, Fatemeh
    et al.
    Department of Wood Science and Technology, Faculty of Natural Resources, Tarbiat Modares University, Tehran, Iran.
    Kazemi Najafi, Saeed
    Department of Wood Science and Technology, Faculty of Natural Resources, Tarbiat Modares University, Tehran, Iran.
    Najafi, Farhood
    Department of Resin and Additives, Institute for Color Science and Technology, Tehran, Iran.
    Pizzi, Antonio
    LERMAB, University of Lorraine, Nancy, France.
    Behrooz, Rabi
    Department of Wood Science and Technology, Faculty of Natural Resources, Tarbiat Modares University, Tehran, Iran.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    The extraction of polyol for the synthesis of lignin-based polyurethane coatings – a review2024Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Artikel, forskningsöversikt (Refereegranskat)
  • 49.
    Huber, Johannes Albert Josef
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Girhammar, Ulf Arne
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Berg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Structural robustness and timber buildings: a review2019Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, nr 2, s. 107-128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Timber buildings are increasing in their dimensions. Structural robustness is imperative for all buildings and specifically important for tall buildings. Lives can be saved if disproportionate collapse can be avoided after a catastrophic event (e.g. accident, terrorism). The literature about robustness is comprehensive concerning concrete and steel buildings, but is rather limited regarding timber. This paper reviews robustness in general and robustness of timber buildings in particular. Robustness is an intrinsic structural property, enhancing global tolerance to local failures, regardless of the cause. A deterministic approach to assess robustness is to remove certain load-bearing elements from the structure and compare the consequences to given limits. Design methods for robustness may be direct by assessing effects of local failure, or indirect by following guidelines. For robust timber buildings, the connections are the key aspects. Usually, metal connectors may provide the required joint ductility. For robust light timber-frame construction, rim beams may be designed. For timber posts and beams and cross laminated timber, guidance regarding robustness is scarce, but in some aspects they seem to be similar to steel frames and precast concrete. Future research should assess the capacity of connections, and evaluate the adequacy of seismic connectors for robust timber buildings.

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  • 50.
    Huuhilo, Tiina
    et al.
    Lappeenranta University of Technology, Department of Mechanical Engineering.
    Martikka, Ossi
    Lappeenranta University of Technology, Department of Mechanical Engineering.
    Butylina, Svetlana
    Lappeenranta University of Technology, Department of Mechanical Engineering.
    Kärki, Timo
    Lappeenranta University of Technology, Department of Mechanical Engineering.
    Mineral fillers for wood-plastic composites2010Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 5, nr 1, s. 34-40Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Five mineral fillers were tested for wood-plastic composites (WPCs): calcium carbonate, two different types of wollastonite, soapstone and talc. The impact of the fillers on the mechanical properties of the composites was studied. The experiments included bending tests, tensile tests, Brinell hardness and scanning electron microscopy experiments. The amount of wood, mineral and plastic (polypropylene) was kept steady. Only the mineral type was changed during the tests. A control sample without any mineral added was also manufactured. The mineral addition improved the tensile strength of the WPCs. The hardness of the composite was also improved when the minerals were added, and along with the increasing mineral hardness, the hardness of the composite increased. The wollastonite acicular shape was crushed during the manufacturing process, so the phase of the process in which the minerals are added requires careful consideration.

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