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  • 151.
    Cai, Lili
    et al.
    Department of Material Science and Engineering, Fujian Agriculture and Forestry University, Fuzhou.
    Chen, Tingjie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. tingjie.chen@ltu.se .
    Wang, Wei
    Department of Material Science and Engineering, Fujian Agriculture and Forestry University, Fuzhou.
    Huang, Daobang
    Department of Material Science and Engineering, Fujian Agriculture and Forestry University, Fuzhou.
    Wei, Qihua
    Department of Material Science and Engineering, Fujian Agriculture and Forestry University, Fuzhou.
    Lin, Ming
    Department of Material Science and Engineering, Fujian Agriculture and Forestry University, Fuzhou.
    Xie, Yongqun
    Department of Material Science and Engineering, Fujian Agriculture and Forestry University, Fuzhou.
    Optimization of aluminum/silicon compounds on fire resistance of old corrugated container fiber foam material2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 3, p. 6505-6517Article in journal (Refereed)
    Abstract [en]

    Old corrugated container fiber foam material (OCCM) was prepared using a liquid frothing approach. The effect of the content of Al/Si compounds, the molar ratio of Al3+/SiO2, and different addition form on the limited oxygen index (LOI) and residue percentage of OCCM was optimized using an orthogonal design. The fire resistance of OCCM was best when the content of Al/Si compounds was 900 mL, the molar ratio of Al3+/SiO2 was 1:1, and the aluminum sulfate solution was added first, followed by the separately added sodium silicate solution. Under these conditions, the LOI and residue percentage of OCCM reached 32.3 and 53.51%, respectively. Thermogravimetric analysis indicated that Al/Si compounds promoted char formation and reduced the heat release of the optimized OCCMs during depolymerisation. Compared with the control group, the residue percentage of optimized OCCM was increased from 12.49% to 37.98%. Fourier transform infrared spectroscopy identified the functional groups of Al/Si compounds in the optimized OCCMs, confirming that pyrolysis of the optimized OCCMs was affected by Al/Si compounds.

  • 152.
    Cai, Lili
    et al.
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Zhuang, Biaorong
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Hang, Daobang
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Wei
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Niu, Min
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Chen, Tingjie
    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.
    Ultra-Low Density Fibreboard with Improved Fire Retardance and Thermal Stability using a Novel Fire- Resistant Adhesive2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 2, p. 5215-5229Article in journal (Refereed)
    Abstract [en]

    A novel fire-resistant adhesive made from polyvinyl alcohol, urea, phosphoric acid, and starch was demonstrated for use as a binder and fire retardant to produce ultra-low density fibreboard (ULDF) with clear environmental benefits. The results from Fourier transform infrared spectroscopy showed the presence of chemical bonding between fire- resistant adhesives and ULDFs. The limiting oxygen index (LOI), combustion behaviour, and thermal stability were characterized using a LOI text, cone calorimeter, and thermal analyzer, respectively. The results demonstrated that the LOI value of the fire-retardant ULDF can reach up to 34.2 with 300 mL of fire-resistant adhesive. It was established that the additive noticeably reduced the peak of heat release rate, total heat release, and total smoke release of ULDF. Their morphologies after combustion were elucidated using a scanning electron microscope, and a char layer in the condensed phase was observed. Thermal analysis showed that the thermal stability of ULDF improved dramatically and the residual weight increased 4-fold, to 48.32%. Therefore, such ULDFs will be tremendously attractive as renewable, sustainable, and bio-based insulating materials.

  • 153.
    Cao, Pingxiang
    et al.
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, China.
    Zhu, Zhaolong
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, China.
    Buck, Dietrich
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Xiaolei, Guo
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, China.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wang, Xiaodong Alice
    Department of Wood and Forest Sciences, Laval University, Quebec, Canada.
    Effect of rake angle on cutting performance during machining of stone-plastic composite material with polycrystalline diamond cutters2019In: Journal of Mechanical Science and Technology, ISSN 1738-494X, E-ISSN 1976-3824, Vol. 33, no 1, p. 351-356Article in journal (Refereed)
    Abstract [en]

    This study investigates the effect of rake angle on cutting performance during machining of stone-plastic composite material with diamond cutters. To that end, an orthogonal cutting experiment was designed, in which stone-plastic composite material was planed by a polycrystalline diamond (PCD) cutter to produce chips. The features studied include cutting forces, cutting heat, chip formation and cutting quality. The conclusions are as follows: Firstly, increased rake angle causes frictional force and resulting force to decrease, promoting an increase in normal force. Secondly, during planing, cutting heat is primarily distributed in the chips, with less retained in the cutting edge, and the least retained in the machined surface. The temperatures of both cutting edge and chip decline with an increase in rake angle. Thirdly, as rake angle increases, chip morphology changes from segmental to curved and then to particle chips, with chip-breaking lengths first increasing and then decreasing. Finally, an increased rake angle leads a more stable cutting process and improved cutting quality. Therefore, with the precondition of blade strength, a diamond cutter with a larger rake angle can be used to machine stone-plastic composite to improve production quality by forming a smoother machined surface.

  • 154.
    Caprolu, Giuseppe
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    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 mechanics2017In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 3, p. 165-188Article in journal (Refereed)
    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. 

  • 155.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Fujian Agriculture and Forestry University, Fuzhou, China.
    Liu, Jinghong
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wu, Zhenzeng
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Wei
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Niu, Min
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Evaluating the Effectiveness of Complex Fire-Retardants on the Fire Properties of Ultra-low Density Fiberboard (ULDF)2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 1, p. 1796-1807Article in journal (Refereed)
    Abstract [en]

    The preparation conditions of complex fire-retardant (FR) agents containing boron compounds (BF, X1), nitrogen-phosphorus compounds (NPF, X2), silicon compounds (SF, X3), and halogen compounds (HF, X4) for ultra-low density fiberboard (ULDF) were optimized using a response surface methodology. The effects and interactions of X1, X2, X3, and X4 on the fire properties of ULDF were investigated. An optimum char yield of 61.4% was obtained when the complex fire-retardant agents contained 33.9% boron, 27.2% nitrogen-phosphorus, 15.0% silicon, and 28.6% halogen. Compared with control fiberboard (CF), the heat release rate (HRR) profiles of all fiberboards with FRs were reduced. The peak HRR reduction in BF and NPF was more pronounced than for SF and HF at this stage. And the mixed fiberboard (MF) had the lowest pkHRR of 75.02 kW m−2. In total heat release (THR) profiles, all fiberboards with FRs were lower than the CF. Unlike the HRR profiles, HF had the lowest THR profile of 15.33 MJ/m−2. Additionally, Si compounds showed greater effectiveness in preventing ULDF mass loss than BF, NPF, and HF. MF showed the highest residual mass (40.94%). Furthermore, the synergistic effect between four FR agents showed more significant results in ULDFs.

  • 156.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Fujian Agriculture and Forestry University, Fuzhou, China.
    Niu, Min
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wei, Wei
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Liu, Jinghong
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Synthesis and characterization of poly-aluminum silicate sulphate (PASS) for ultra-low density fiberboard (ULDF)2015In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 113, p. 93187-93193Article in journal (Refereed)
    Abstract [en]

    The poly-aluminum silicate sulphate (PASS) for ultra-low density fiberboard (ULDF) was synthesized in the mixed aqueous solution of sodium silicate and aluminum silicate by sol-gel method. Their preparation conditions were optimized by using a response surface methodology. The effects and interactions of Si/Al molar ratio (X1), pH value (X2) and temperature (X3) on internal bond strength of ULDF were investigated. Research showed that the optimum internal bond strength (10.23 ± 0.64 kPa) was obtained under Si/Al molar ratio of 2:1, pH value of 8, and 50oC. Analyses of the Fourier transform infra-red spectroscopy spectra confirmed that Al-O-Si bonds were formed between polysilicate and Al or its hydrolysate. The particle size analysis showed that the average size of PASS was 7.52 μm. And the part of PASS entered the cell wall and made a contribution to the improvement of mechanical properties of ULDF.

  • 157.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Fujian Agriculture and Forestry University, Fuzhou, China.
    Wu, Zhenzeng
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Niu, Min
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wei, Qihua
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Rao, Jiuping
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Effect of polyvinyl alcohol (PVA)/Si-Al hybrid composites on the mechanical properties of ultra-low density fiberboard (ULDF)2016In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225Article in journal (Refereed)
    Abstract [en]

    The microstructure and properties of ultra-low density fiberboard (ULDF) were affected by the different contents of polyvinyl alcohol (PVA). They were tested by using scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), thermogravimetric analyzer (TGA), and microcomputer control electronic universal testing machine, respectively. The SEM result showed that the microstructure of ULDFs was affected by the PVA. The FTIR and XRD results showed that there were two forms between PVA and Si-Al sol. They were combining with chemical bond and physical cross linking. The TGA results revealed that the thermostability of ULDF was decreased with the increasing content of PVA. Combined with the TGA and mechanical properties results, the reasonable content of PVA which was 30% was obtained. Under this condition, the modulus of rupture, modulus of elasticity, and the internal bond strength of ULDF were significantly improved from 0.13, 16.09, and 0.021 MPa to 0.35, 24.86, and 0.038 MPa, respectively.

  • 158.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Fujian Agriculture and Forestry University, Fuzhou, China.
    Wu, Zhenzeng
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Niu, Min
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Effect of Si-Al Molar Ratio on Microstructure and Mechanical Properties of Ultra-low Density Fiberboard2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, no 2, p. 151-160Article in journal (Refereed)
    Abstract [en]

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

  • 159.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wu, Zhenzeng
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wei, Wei
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Niu, Min
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wei, Qihua
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Rao, Jiuping
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Hybrid composites of polyvinyl alcohol (PVA)/Si-Al for improving the properties of ultra-low density fiberboard (ULDF)2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 25, p. 20706-20712Article in journal (Refereed)
    Abstract [en]

    The hybrid composites of polyvinyl alcohol (PVA)/Si-Al were synthesized to improve the thermostability and mechanical properties of ultra-low density fiberboard (ULDF). Their physical and chemical properties were tested by using scanning electron microscopy, Fourier transform infrared spectrometry, X-ray diffractometry, thermogravimetric analysis (TGA), and a microcomputer control electronic universal testing machine. Microstructure results indicated that the distribution of inorganic fillers on the surface of ULDF was improved by the PVA. Analysis of chemical bonds and crystallinity of materials showed that part of the PVA reacted with Si-Al sol, and the other was physically crosslinked in the composite. The thermostability of ULDF decreased with the increasing content of PVA, but the mechanical properties increased. Combined with the TGA and mechanical properties results, a reasonable content of PVA (30%) was obtained. Under this condition, the modulus of rupture, modulus of elasticity, and the internal bond strength of ULDF were 0.35, 24.86, and 0.038 MPa, respectively

  • 160.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wu, Zhenzeng
    College of Material Engineering, Fujian Agricultural and Forestry University.
    Wei, Wei
    College of Material Engineering, Fujian Agricultural and Forestry Universit.
    Xie, Yongqun
    College of Material Engineering, Fujian Agricultural and Forestry Universit.
    Wei, Qihua
    College of Material Engineering, Fujian Agricultural and Forestry Universit.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Optimizing Refining Conditions of Pinus massoniana Cellulose Fibers for Improving the Mechanical Properties of Ultra-Low Density Plant Fiber  Composite (ULD_UFC)2017In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 1, p. 8-18Article in journal (Refereed)
    Abstract [en]

    Response surface methodology was used to optimize the refining conditions of Pinus massoniana cellulose fiber and to improve the mechanical properties of ultra-low density plant fiber composite (ULD_PFC). The effects and interactions of the pulp consistency (X1), the number of passes (X2), and the beating gap (X3) on the internal bond strength of ULD_PFC were investigated. The results showed that the optimum internal bond strength (91.72 ± 2.28 kPa) was obtained under the conditions of 8.0% pulp consistency, two passes through the refiner, and a 30.0 μm beating gap. Analysis of the physical properties of the fibers and handsheets showed that the fibrillation of fibers with optimum refining conditions was improved. Also, the tear index of the optimal specimen was 13.9% and 24.5% higher than specimen-1 with a lowest beating degree of 24 oSR and specimen-6 with a highest beating degree of 73 oSR, respectively. Consequently, the optimal refining conditions of the fibers are valid for preparing ULD_PFCs.

  • 161.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Department of Wood Science & Technology, Fujian Agriculture and Forestry University, Fujian Agriculture and Forestry University, Fuzhou, China.
    Cai, LiLi
    Fujian Agriculture and Forestry University, Department of Wood Science & Technology, Fujian Agriculture and Forestry University, Fuzhou, China.
    Zhuang, Biaorong
    Fujian Agriculture and Forestry University, Fuzhou, China, College of Material Engineering, Fujian Agriculture and Forestry University.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wu, Zhenzeng
    Fujian Agriculture and Forestry University, Fuzhou, China, College of Material Engineering, Fujian Agriculture and Forestry University.
    Niu, Min
    Fujian Agriculture and Forestry University, Fuzhou, China, College of Material Engineering, Fujian Agriculture and Forestry University.
    Lin, Ming
    College of Material Engineering, Fujian Agriculture and Forestry University.
    Mesoporous Aluminosilicate Material with Hierarchical Porosity for Ultralow Density Wood Fiber Composite (ULD_WFC)2016In: A C S Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 4, no 7, p. 3888-3896Article in journal (Refereed)
    Abstract [en]

    This study investigates the application of mesoporous aluminosilicate material with hierarchical porosity to ultralow density wood fiber composite (ULD_WFC) for improving their mechanical properties. A 300 nm thickness Si–Al inorganic film was applied to the surface of the fibers. The mesoporous aluminosilicate material with many mesopores ranging from 2 to 20 nm was obtained. Their total pore volume and Brunauer–Emmett–Teller surface area were 0.193 cm3/g and 355.2 m2/g, respectively. Thermogravimetric analysis indicated that the thermostability of ULD_WFCs was affected by Si–Al compounds. But the residual weight of ULD_WFC with Si–Al compounds was 23.87% greater than composite without Si–Al compounds. The X-ray diffraction analysis indicated partial conversion of SiO2 to α-SiC. These conditions attributed to improving the mechanical properties of ULD_WFC. The modulus of elasticity, modulus of rupture, and internal bond strength of composite with Si–Al compounds increased by 547.4%, 240.0%, and 400.0%, respectively, as compared with uncoated ULD_WFC.

  • 162.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. tingjie.chen@ltu.se .
    Xie, Yongqun
    Department of Material Science and Engineering, Fujian Agriculture and Forestry University, Fuzhou.
    Wei, Qihua
    Department of Material Science and Engineering, Fujian Agriculture and Forestry University, Fuzhou.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Liu, Jinghong
    Department of Material Science and Engineering, Fujian Agriculture and Forestry University, Fuzhou.
    Effect of Refining on Physical Properties and Paper Strength of Pinus massoniana and China Fir Cellulose Fibers2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 3, p. 7839-7848Article in journal (Refereed)
    Abstract [en]

    To obtain a suitable refining process for Pinus massoniana cellulose fibers (PMCF) and China fir cellulose fibers (CFCF), the effects of the beating gap and the pulp consistency on the physical properties and the morphology of the two cellulose fibers were investigated. The results showed that the physical properties of the PMCF and the CFCF were well affected by the beating gap and the pulp consistency. The CFCF showed a smaller weight-average length and width than that of the PMCF. The CFCF exhibited smaller weight-average length, width, and kink index than the PMCF. It is easy to get the high beating degree, indicating it is more easily to be refined. Additionally, the tensile index and burst index of PMCFP and CFCFP increased with increasing beating degree, while the tear index decreased. Compared to the CFCF, the paper made from PMCF had superior strength properties. Consequently, the PMCF was suitable for refining with a high pulp consistency and a medium beating gap, whereas the CFCF had a medium pulp consistency and a big beating gap.

  • 163.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Xie, Yongqun
    College of Material Engineering, Fujian Agriculture and Forestry University.
    Wei, Qihua
    College of Material Engineering, Fujian Agriculture and Forestry University.
    Wang, Xiaodong (Alice)
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Liu, Jinghong
    College of Material Engineering, Fujian Agriculture and Forestry University.
    Lin, Ming
    College of Material Engineering, Fujian Agriculture and Forestry University.
    Improving the Mechanical Properties of Ultra-Low Density Plant Fiber Composite (ULD_PFC) by Refining Treatment2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 8558-8569Article in journal (Refereed)
    Abstract [en]

    To improve the mechanical properties of ultra-low density plant fiber composite (ULD_PFC), a suitable beating process to improve the fibrillation of cellulose fibers and maintain their length was investigated. The physical properties of cellulose fibers and papers, surface chemical bonds, and internal bond strength (IB) of ULD_PFCs were analyzed. The results showed that the beating degrees, degree of fibrillation, and fiber fines increased with the decreasing of beating gap, except for the fiber weight-average length, width, kink index, and curl index. The tensile index and burst index of paper showed an increasing trend with an increase in beating degree, while the tear index showed a decreasing trend. FTIR results showed that intermolecular and intramolecular hydrogen bonds in ULDF were broken. A suitable beating gap of 30 μm with a beating degree of 35 °SR was obtained. The corresponding IB was 50.9 kPa, which represented an increase of 73.1% over fibers with a beating degree of 13 °SR.

  • 164.
    Cherepanova, Ekaterina
    et al.
    Luleå tekniska universitet.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Determination of wood moisture properties using CT-scanner in a controlled environment2011In: Proceedings of the 7th meeting of the Nordic-Baltic Network in Wood Material Science and Engineering (WSE) / [ed] Erik Larnøy; Gry Alfredsen, Ås: Norsk institutt for skog og landskap , 2011, p. 137-142Conference paper (Refereed)
    Abstract [en]

    The aim of the present work was to examine the existing algorithm for the moisture content calculation and also to use this algorithm to analyze and compare the moisture flow data for high and low temperature drying. The use of the existing algorithm for the dry weight moisture content on density data from the CT-scanning during high and low temperature drying in the climate chamber showed that this method is a powerful tool for analyzing the moisture flow inside the wood piece. Furthermore, the new CT-scanner together with the climate chamber gave unique results, as it has not been possible to study high temperature drying with this method before.

  • 165. Chiorescu, Sorin
    et al.
    Berg, P.
    Swedish Institute for Wood Technology Research.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The fingerprint approach: using data generated by a 2-axis log scanner to accomplish traceability in the sawmill's log yard2003In: Forest products journal, ISSN 0015-7473, Vol. 53, no 2, p. 78-86Article in journal (Refereed)
    Abstract [en]

    Today the sawmill industry is in possession of sophisticated measuring devices for sawlogs. This equipment is employed in practice for measuring log dimensions, and the data gathered are used for sorting out sawlogs according to different criteria or for judging potential quality for future end-uses. However, a lot of these data are not fully utilized. Meanwhile, large knowledge gaps regarding the flow and the origin of the wood material persist in the sawmill's daily routine. For sawmills performing presorting of sawlogs, the most significant information gap is located between the log sorting station and the saw intake where the log batch identity disappears and the logs are mixed according to different sorting criteria. This study attempts to use the data generated by 2-axis log scanners to develop a traceability system, the fingerprint approach (a marking/reading free system), between the log sorting station and the saw intake. The originality of the fingerprint approach is based on the biological variability of the wood material; the assumption is that each sawlog is a unique individual with unique features. Measuring these features at the log sorting station and at the saw intake and then connecting them to a common database will in fact permit each individual sawlog to be followed within the sawmill and thus enable the development of an advanced raw material flow control. The results of this work entirely indicate the promising potential of the fingerprint approach, which is based on the hypothesis that logs are separate entities with individual features. Being able to separate logs at the individual level is essentially a question of taking advantage of the right log features, measuring them with high accuracy, and employing appropriate search/recognition algorithms. The log parameters and the measurement accuracy generated by the 2-axis log scanner used in this study were not enough to accomplish individual separation for more than 34 percent of the logs. An improvement of measurement accuracy by 30 percent would allow 50 percent of the logs to be individually separated.

  • 166. Chiorescu, Sorin
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Assessing the role of the harvester within the forestry-wood chain2001In: Forest products journal, ISSN 0015-7473, Vol. 51, no 2, p. 77-84Article in journal (Refereed)
    Abstract [en]

    In recent years, a lot of effort has been devoted to implementing the concept of an integrated forestry-wood chain. Good management of such a complex system requires a clear understanding of the effects that different factors involved may have on the final output of the chain. Raw material databases and simulation software capable of spanning the wood-processing operations have now been developed and are being used as a support tool in understanding and optimizing the forestry-wood chain. This paper reports results of simulation tests using the virtual SawMill software and the Swedish Pine Stem Bank database. The simulated scenario tries to mirror a very customer-oriented production philosophy. The bucking, the sawing, the crosscutting, and the board-grading procedures were simulated for different end-user requirements and a statistical model was built. The purpose of the model was to investigate the theoretical sensitivity of the final product to parameters such as external sawlog features (taper, ovality, bow), harvester measurement accuracy (for length and diameter), sawing pattern optimization, and log positioning in the saw line. Special emphasis was put on evaluating the role of the harvester within this "puzzle." The results show that small improvements of the harvester's measuring performance could lead to considerable improvements in the wood transformation chain.

  • 167. Chiorescu, Sorin
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The fingerprint approach: using data generated by a 3D log scanner on debarked logs to accomplish traceability in the sawmill's log yard2004In: Forest products journal, ISSN 0015-7473, Vol. 54, no 12, p. 269-276Article in journal (Refereed)
    Abstract [en]

    Technological advances in the area of optical scanning have made sophisticated equipment such as three-dimensional (3D) log scanners available to the sawmill industry. In a typical Swedish sawmill, the measurements obtained from the 3D log scanner placed at the log sorting station is used exclusively for scaling and sorting the sawlogs. In the same way, the information obtained from the 3D log scanner placed at the saw intake is used exclusively for optimal positioning of the sawlog into the headrig. Meanwhile, large knowledge gaps regarding the flow and the origin of the sawlogs persist in the sawmill's daily routine. For the Swedish sawmills performing presorting of sawlogs, the most critical information gap exists between the log sorting station and the saw intake, where the forest log batch identity disappears, and the logs are mixed according to various sorting criteria. This study attempts to use the data generated by 3D log scanners together with advanced recognition algorithms to develop a traceability system, marking/reading free, between the log sorting station and the saw intake when working with debarked logs. The originality of the fingerprint approach rests on the hypothesis that logs are separate entities with individual features. Measuring these features with the same type of measuring device at both the log sorting station and at the saw intake and then connecting the data to a common database will permit each individual sawlog to be tracked within the sawmill and will thus make it possible to develop an advanced raw material flow control.

  • 168. Chiorescu, Sorin
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The fingerprint method: using over-bark and under-bark log measurement data generated by three-dimensional log scanners in combination with radiofrequency identification tags to achieve traceability in the log yard at the sawmill2004In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 19, no 4, p. 374-383Article in journal (Refereed)
    Abstract [en]

    In the forestry-wood chain the concept and the technologies of traceability are in a mature development phase. Important advances in marking and reading techniques have been made in different parts along the forestry-wood chain. For Swedish sawmills the most critical information gap is located between the log sorting station and the saw intake, where the forest log batch identity disappears and the logs are mixed according to different sorting criteria. This study utilizes radiofrequency identification tags for automatic log marking/reading to develop a traceability system for logs, which is free of marking/reading, between the log sorting station and the saw intake, i.e. the fingerprint method. The originality of the fingerprint approach rests on the hypothesis that logs are separate entities with individual features. The results show that the log parameters and the search algorithm developed, combined with the negative influence of the measurement uncertainty due to bark thickness and bark damage, made it possible to achieve an individual separation for 57% of the tested logs.

  • 169. Chiorescu, Sorin
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The visual grading system for Scots pine logs in relation to the quality of sideboards produced2003In: Forest products journal, ISSN 0015-7473, Vol. 43, no 1, p. 53-60Article in journal (Refereed)
    Abstract [en]

    Presorting logs in the sawmill's log yard is one of the strategies used by the Swedish sawmilling industry in order to maximize profits. Almost 96 percent of Swedish sawmills perform the presorting of logs according to their dimension, most commonly by the top diameter. Only a very small number of sawmills use log grade information as a sorting criterion. However, the grade information at individual log level, together with the estimated volume, is always used for the calculation of log payment. The quality assessment of the log is done on a visual basis, i.e., the measurer grades the log on what he/she sees on the outside of the log. This judging should correspond to the expected quality of the Centerboards produced after sawing. Current studies have only related the centerboards' quality to the log quality grade arrived at by visual inspection. In view of the economic importance of the sideboards in the lumber yield and in the entire functioning of a sawmill, a real need for information on the recovery of sideboards in relation to log and centerboard quality is now arising and becoming a key issue. In this study, with the help of the entire Swedish Pine Stem Bank material, the relationship between the sideboard's quality and the log's quality and the relationship between the quality of sideboards and of centerboards were studied. Results show that sideboard quality cannot be predicted from the visual quality assessment of the logs. Nevertheless, fairly good correlation exists between sideboard quality and the quality of the corresponding centerboards. A financial analysis focusing on the relationship between the commercial values of the sawlogs and the corresponding lumber output for the Swedish Pine Stem Bank material is also included in this study. The study shows that the actual Swedish log pricing system should be improved because the commercial values of the logs are not in accord with the real values of the lumber produced.

  • 170. Chiorescu, Sorin
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Validation of a CT-based simulator against a sawmill yield2000In: Forest products journal, ISSN 0015-7473, Vol. 50, no 6, p. 69-76Article in journal (Refereed)
    Abstract [en]

    Over the past decade, the sawmill sector has made significant advancements in developing methods for measuring inner properties of sawlogs. Noninvasive scanning, e.g., x-ray scanning, has proven to have good prospects for on-line implementation in sawmills. When the internal scanning technique does come on-line in sawmills, software able to utilize the scanned information becomes a useful tool to control the sawing process. Thus, the validation of such a computed tomography (CT)-based software against sawmill cutting becomes an important step in the development of the whole scanning approach. This paper presents the results of an effort to simulate the 1-year lumber production of a medium-sized Swedish sawmill with the aid of a CT-based simulator, the virtual SawMill (vSM). This saw simulation program is able to utilize the parametrical description of the logs achieved from x-ray CT-scanning. When performing the simulation, the vSM used 625 Scots pine (Pinus sylvestris L.) logs from the Swedish Stem Bank as raw material supply for the sawing process. The simulated sawing process was adjusted to keep, as much as possible, the same attributes as the sawing process from the sawmill. The output data collected from the sawmill was compared with the simulated one with respect to the quality and the length distribution of the yielded boards. The results showed good agreement between the real and the simulated cutting for both quality and length criteria. This study suggests that the Swedish Stem Bank along with the vSM software could be used as an efficient tool in further research and strategic production planning.

  • 171.
    Cibecchini, Daniele
    et al.
    GESAAF - Department of Agricultural, Food and Forestry Systems, University of Florence, Italy.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sousa, Hélder
    ISISE - Department of Civil Engineering, University of Minho, Guimarães, Portugal.
    Jorge, Marco
    ISISE - Department of Civil Engineering, University of Minho, Guimarães, Portugal.
    Branco, Jorge
    ISISE - Department of Civil Engineering, University of Minho, Guimarães, Portugal.
    Repairing of a timber truss through two different techniques using timber elements and screwed metal plates2015In: Historical Earthquake-Resistant Timber Framing in the Mediterranean Area: HEaRT 2015, 2015, p. 371-381Conference paper (Refereed)
    Abstract [en]

    Structural reinforcement of timber buildings may be needed due to different reasons such as change of use, deterioration, lack of maintenance, exceptional damaging incidents or loading, to comply with regulatory changes and being retrofitted, or interventions to increase structural resistance.In this work, two different techniques were considered for repair of a timber truss, subjected only to vertical loads, that was previously assessed on laboratory (test facilities of University of Minho) and taken up to failure during a load-carrying test. A collar beam truss, with more than one hundred years, was tested carrying a vertical point load on each main rafter. Failure of the timber truss was located in the sections of the rafters near the loading positions by bending.Repairing techniques, based on the use of timber elements for one of the rafters and on screwed metal plates for the other rafter, were evaluated and compared to the original unstrengthened condition. The efficiency of the combined repairing techniques was evaluated taking into consideration the structural performance of the collar truss, namely its displacement and ultimate load capacity.In this paper, the results of the experimental tests are discussed attending to the analytical calculation of the contribution of the repairing techniques. Also, the different failure scenarios, for original and strengthened truss, were analyzed and compared.

  • 172.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Avramidis, Stavros
    University of British Columbia.
    Automatic knot detection in coarse resolution cone-beam CT images of softwood logs2019In: Forest products journal, ISSN 0015-7473Article in journal (Refereed)
  • 173.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Avramidis, Stavros
    University of British Columbia.
    Knot detection in coarse resolution CT images of logs2017In: International Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    The use of X-ray computed tomography (CT) scanning of logs in sawmill is becoming a reality in the last few years, usually with rather costly and complex machines resembling medical scanners. However, a scanning solution has been developed that is less costly and more robust, and therefore more suited for sawmill needs. The rather coarse data from this machine has not been fully evaluated regarding possibilities to detect internal features such as knots. In this study, a knot detection algorithm developed for medical scanners was applied to images from a coarse resolution scanner, from four different logs of various species, and with different image resolution. The objective was to see if it was possible to detect knots automatically in the images. If so, the aim was to calculate the knot detection rate and the accuracy of detected knot size and position. These numbers were calculated compared to manually measured reference knots. This resulted in a knot detection rate of about 53 % overall, and a well detected knot position, but poorly detected knot size. It is possible to observe a certain difference between species and reconstruction resolution, however the material is too small to draw any definite conclusions. As a preliminary study, it provides input for further investigation on knot detection in coarse resolution X-ray CT images. Future work involves scanning more logs to get more data, and to pinpoint the resolution needed for accurate knot detection using the current algorithm.

  • 174.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Stephen, James D
    Queen’s University.
    Mabee, Warren E
    Queen’s University.
    Avramidis, Stavros
    University of British Columbia.
    Bull, Gary Q
    University of British Columbia.
    An Integrated Forest Products Cluster for Off-Grid Lumber Production Using Biomass CHP in Remote Indigenous Communities2017Conference paper (Refereed)
  • 175.
    Couceiro, José
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wood shrinkage in CT-scanning analysis2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Computed tomography (CT) can be used to study wood-water interactions in differentways, such as by determining wood moisture content (MC). The determination of MCrequires two CT images: one at the unknown moisture distribution and a second one ata known reference MC level, usually oven-dry MC. The two scans are then compared.If the goal is to determine the MC in local regions, when studying moisture gradients forinstance, wood shrinkage must be taken into account during the data processing of theimages. The anisotropy of wood shrinkage creates an obstacle, however, since theshrinkage is not uniform throughout the wood specimen.

    The objective of this thesis was to determine the shrinkage in wood in each pixel of aCT image. The work explores two different methods that estimate from CT images, thelocal shrinkage of a wood specimen between two different MC levels. The first methoddetermines shrinkage for each pixel using digital image correlation (DIC) and isembedded in a wider method to estimate the MC, which is the parameter verifiedagainst a reference. It involves several steps in different pieces of software, making ittime-consuming and creating many sources of possible experimental errors. The MCdetermined by this method showed a strong correlation with the gravimetricallymeasured MC, showing an R2 of 0.93 and the linear regression model predicted MCwith a RMSE of 1.4 MC percentage points.

    The second method uses the displacement information generated from the spatialalignment of the CT images in order to compute wood shrinkage in the radial andtangential directions. All the required steps are combined into a single computeralgorithm, which reduces the sources of error and facilitates the process. The RMSEbetween this method and the determination of shrinkage measured in the CT imagesusing CAD has shown acceptable small differences.

    Both methods have proved to be useful tools to deal with shrinkage in different ways byusing CT images. In one case MC was successfully estimated, being the shrinkagecalculation a necessary step in the process, and in the other case the radial and tangentialshrinkages were successfully estimated for each pixel. Nevertheless, the difficulty incomparing the shrinkage coefficient calculated for local regions with a reference valuesuggest that more research must be carried out in order to be able to draw reliableconclusions.

  • 176.
    Couceiro, José
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    X-ray computed tomography to study moisture distribution in wood2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    X-ray computed tomography (CT) has been used as an analysing tool for different features in wood research since the beginning of the1980s, but it can also be used to study wood-water interactions in different ways, such as by determining wood moisture content (MC). The determination of wood MC with CT requires two CT images: one at the unknown moisture distribution and a second one at a known reference MC level, usually at oven-dry condition. The two scans are then compared, and the MC is calculated based on the differences between the images. If the goal is to determine the MC in local regions within the wood volume, e.g. when studying moisture gradients in wood drying, wood shrinkage must be taken into account during the data processing of the images. The anisotropy of wood shrinkage creates an obstacle, however, since the shrinkage is not uniform throughout the wood specimen. The technique is thus limited in two ways: it cannot measure MC in local regions and it cannot do it in real time.

    The objective of this thesis was to study methods to overcome these two limitations. The work explores up to three different methods to estimate local MC from CT images in real time. The first method determines shrinkage for each pixel using digital image correlation (DIC) and is embedded in a broader method to estimate the MC, which verified against a reference. It involves several steps in different pieces of software, making it time-consuming and creating many sources of possible experimental errors. The determination of shrinkage within this method is further explored to enable the implementation of all steps in a unique piece of software. It is shown that it is possible to calculate MC through this method with a root mean square error of prediction of 1.4 percentage points for MC between 6 and 25%.

    The second method studied succeeds in determining the MC distribution in research applied to wood drying, but the calculation of shrinkage differs from the previous method: instead of calculating shrinkage in the radial and tangential directions, it does so by using the displacement information generated from the spatial alignment of the CT images. Results show that the algorithm can provide consistent data of internal MC distribution of wood at the pixel level that entail continuing researching wood drying processes with an improvement in the accuracy of the MC determination. It represents an improvement regarding the first method because the calculation is fast and highly automatized in a single piece of software.

    The third method studied is the application of dual energy CT (DECT) to moisture. DECT would provide means for MC calculation at the pixel level and, potentially, in real time, which would mean an important breakthrough in wood drying research. Previous research shows promising results, but its implementation in medical CT, the tool used throughout this work, has shown poor predicting ability. Nevertheless, further research is encouraged.

    The work done in this thesis proves that it is possible to measure local distribution of MC in wood using CT with accuracy and precision. It also shows that further research could potentially provide a means for MC estimation in real time.

  • 177.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Implementation of Computer Aided Tool for Non-Destructive X-Ray Measurement of Moisture Content Distribution in Wood2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 330-336Article in journal (Refereed)
    Abstract [en]

    This paper reports recent attempts for implementing non-destructive measuring of moisture contentin wood based on computed tomography technology. The study focus onan image analysis method that has been already proposed and validated in the literature, but ithas not been tested for measuring low moisture content variations below fibre saturation point.The computed tomography method was tested against the oven-dry method.The results show thatit is possible to apply this technology to measure low levels of moisture content based on a regression model, where therootmean square error of the modelwas 1,4percentage points of moisture content. The method can still be improved because the density differences between samples are relatively small in relation to the experimental error and the computed tomography precision.

  • 178.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Ocean Operations and Civil Engineering. Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Ahec, Ambroz
    University of Ljubljana.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    CT-scanning of the drying process of Eucalyptus nitens.2018In: Proceedings of 21st International Drying Symposium. / [ed] Cárcel JA, Polo GC, García-Pérez JV, Mulet A, Rosselló C.,, Valencia: Editorial Universitat Politècnica de València , 2018, p. 1269-1276Conference paper (Refereed)
    Abstract [en]

    The drying of Eucalyptus nitens is a troublesome process as the species is extremely prone to drying defects. This paper reports ongoing research toimprove the understanding of surface checking and cell collapse in Chilean grown Eucalyptus nitens during drying. Computed tomography (CT) scanning was used as a powerful tool for studying the internal changes in the wood-material during the drying process. Different levels of temperatures have been tested with the same equilibrium moisture content (EMC) conditions and low air velocity. The results confirm that a low drying temperature and a low air velocity, which results in a slow rate of drying, reduce internal cell collapse and surface checking .

  • 179.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    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.
    In situ CT-scanning for detection of internal checking and cell collapse during drying of hardwood species2016In: The 7th European Conference on Hardwood, Eco-efficient resource wood with special focus on hardwoods / [ed] Teischinger A., Németh R., Rademacher P., Bak M. & Fodor F. (Eds.), Sopron: University of West Hungary , 2016, p. 58-59Conference paper (Refereed)
    Abstract [en]

    During the drying of sawn timber, hydrostatic tension forces within the cell may exceed the compressive strength perpendicular to the grain of the thin cell wall and the cell then collapses. This phenomenon is common in hardwoods such as Sequoia sempervirens, Thuja plicata, Tsuga heterophylla, Juglans nigraand many species of eucalyptus and oak. Usually, this leads to severe surface deformation, and both surface and internal checking(honeycombing) may occur. The quality of the final product is lowered by these cracks and deformations. The aim of this study was to investigate, by CT-scanning samples throughout the drying process, whether it is possible to detect when and how cracking and deformation occurs and develops in specimens of Eucalyptus nitens. Based on this knowledge, better drying schedules can be developed to improve the yield and ensure a higher quality of the sawn timber. Three specimens, one specimen in each drying run, of Eucalyptus nitens were used for the tests. Their cross-sectional dimensions, prior to drying, were 105x23 mm2 and their length was 70 cm. A specially designed laboratory drying kiln that fits within the gantry of a Siemens Somatom Emotion medical CT-scanner was used (Fig. 1). With this equipment, it is possible to scan the inside of the kiln without interrupting the drying process.

  • 180.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Sehlstedt-Persson, Margot
    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.
    CT-studies during the Conditioning phase of the Wood Drying Process2018Conference paper (Other academic)
    Abstract [en]

    Computed tomography (CT) during drying of sawn timber is an excellent non-destructivetechnique to study the moisture flux as a function of drying time. In this study, a climatechamber combined with a medical CT- scanner has been used for non-destructive studies ofdensity changes in sawn timber during drying and conditioning.Green sawn timber contains large amounts of water and has to be dried before it can befurther processed and used in various building applications. The most common dryingmethod is convective air-circulation drying in large industrial kilns, where the relativehumidity (RH) of the hot circulating air is gradually reduced until the timber reaches thetarget moisture content (MC).Drying of sawn timber is driven by the existence of a difference in MC between the coreand the surface, so that moisture moves from the wet inner region towards the drier outerregion. During the early capillary stages of drying, the drying rate is high while, at the laterstages when all liquid water has evaporated, the drying rate is slow and diffusioncontrolled.At the end of the drying process, the timber surface is always drier than its core.In addition to this moisture gradient, internal stresses develop within the cross section withcompression stresses in the timber surface and tension in the inner regions. To avoidunwanted distortions, both these stresses and the moisture gradient, need to be eliminatedbefore the timber is further processed. This is achieved in a final conditioning stage withinthe drying process by moistening the circulating air through steaming or water spraying.The aim of the present work was to optimize the conditioning stage by developing amethod for studying of moisture gradients, deformations and internal and externaldimensional changes in sawn timber during the conditioning phase by using a CT-scannercombined with a drying unit for in-situ measurements of moisture flow.The results show that it is possible to detect the moisture gradient between the surface andcore of the timber with satisfactory reliability, but not the internal and external dimensionalchanges. However, this method creates a potential for increasing the knowledge andunderstanding of the conditioning phase and makes it possible to optimize and develop thisstep in the drying process to improve the yield and ensure a higher quality of the sawntimber.

  • 181.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The use of X-ray computed tomography in timber construction research2016In: New Horizons for the Forest Products Industry: 70th Forest Products Society International Convention, June 26-29, Portland, Oregon, USA, Madison: Forest Products Society, 2016Conference paper (Other academic)
    Abstract [en]

    powerful tool for the non-destructive measurement of dynamic processes in wood. For more than 20 years, CT has been used in wood research at Luleå University of Technology. The uniqueness of the CT equipment means that processes such as drying, modification, water absorption, internal and external cracking and material deformation can be studied in temperature- and humidity-controlled environments. The data recorded by the CT during the process is converted into two- or three-dimensional images that for instance can show dynamic moisture behavior in wood drying.This paper gives an overview of the possibilities of using CT in timber construction research, and shows examples of applications and results which can be particularly difficult to achieve using other methods. A specific focus is on studies on wood products for construction, and how to deal with different material combinations such as wood and metal.The practical application of the result is that CT-scanning, combined with image processing, can be used for non-destructive and non-contact 3-D studies of exterior constructions elements during water sorption and desorption, to study swelling and shrinking behaviour, delamination phenomena, crack development, etc.

  • 182.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Estimation of miosture content in wood using dual x-ray energies in a medical CT-scanner2016In: Process Technologies for the Forest & Biobased Products Industries: PTF BPI 2016, 2016, p. 22-Conference paper (Other academic)
  • 183.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Söderström, Ove
    c Professor Emeritus of Building Materials, Stockholm, Sweden.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Real-time wood moisture-content determination using dual-energy X-ray computed tomography scanning2019In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Article in journal (Refereed)
    Abstract [en]

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

  • 184.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Neyses, Benedikt
    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.
    In-situ moisture content and density measurements in surface densified wood using dual X-ray absorptiometry in medical CT-scanning2016In: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium, Bio-based composites for a sustainable future., Concepción: University of Concepción , 2016, Vol. 2, p. 92-, article id NA01Conference paper (Refereed)
  • 185.
    Couceiro, José
    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.
    The use of X-ray computed tomography in bio-composite research2016In: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium : Bio-based composites for a sustainable future,, Conceptión: University of Concepción , 2016, p. 42-45Conference paper (Refereed)
    Abstract [en]

    X-ray computed tomography (CT), which was introduced in the medical field in the early 1970s, is also a powerful tool for the non-destructive measurement of dynamic processes in wood. For more than 20 years, medical CT has been used in wood research at Luleå University of Technology. The uniqueness of the CT equipment allowsprocesses such as drying, modification; water absorption; internal and external cracking; and material deformation to be studied in temperature- and humidity-controlled environments. The data recorded by the CT scanner during the process is converted into two or three dimensional images that, for instance, can show dynamic moisture behaviour in wood drying and crack formation. This paper provides an overview of the possibilities of using CT in bio-composite research, and shows examples of applications and results that can be particularly difficult to achieve using other methods. A specific focus is on studies on wood products that use combinations with materials such as metal and especially about how to deal with the difficulties that this entails.The practical application of the result is that CT scanning, combined with image processing, can be used for non-destructive and non-contact three-dimensional s tudies of exterior construction elements during water sorption and desorption, to study parameters such as swelling and shrinking behaviour; delamination phenomena; and crack development.

  • 186.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Norwegian University of Science and Technology (NTNU), Department of ICT and Natural Sciences, Norway.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    CT scanning of capillary phenomena in bio-based materials2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 181-187Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) is a powerful tool for the non-destructive study of dynamic moisture processes in wood and other bio-based materials. In the CT facilities at Luleå University of Technology, it is possible to study wood-moisture relations such as water absorption, drying and related material deformation under a temperature- and humidity-controlled environment.An increase in the use of bio-based materials in building construction has led to an increased interest in capillary phenomena in these materials, because of an increasing number of moisture-related damage in timber and hybrid-timber buildings. This article shows some examples of how different bio-materials used in construction interact with liquid water over time. The overall purpose has been to develop the CT technique as a powerful tool for the determination and visualization of capillary flow that can be a base for modelling and an increased understanding of moisture flow in new bio-based building materials.Early-stage observation of the behaviour of different traditional and new bio-based building materials shows that CT scanning, combined with image processing, has a high potential to be used in performing non-destructive and non-contact tests that can help to increase the knowledge of water-material interactions and develop building materials with an optimized performance.

  • 187.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Vikberg, Tommy
    SP Technical Research Institute of Sweden .
    Hansson, Lars
    Natural Sciences and Preliminary Courses, NTNU Ålesund, Norway .
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    In Situ CT-Scanning of Checking and Collapse Behaviour of Eucalyptus nitens During Drying2016In: Proceedings of the 59th International Convention of Society of Wood Science and Technology March 6-10, 2016 – Curitiba, Brazil, 2016Conference paper (Other academic)
    Abstract [en]

    Eucalyptus nitens has become a commercially important species in Chile and it isrepresenting one of the fastest growing wood-stock in the country. Today, it is widelyused for pulp and paper production, but the interest in using the solid wood has increasedin recent years. Before the sawn timber can be utilized, its moisture content must bereduced. Often during drying, hydrostatic tension forces within the cell exceed thecompressive strength of the thin cell wall of Eucalyptus nitens and the cell collapses. Thisphenomenon usually leads to severe surface deformation and both surface and internalcracks (honeycombing). Yield and quality of the final product, and thereby sawmills’profitability, are decreased by these cracks and deformations. The aim of this study wasto investigate, by CT-scanning samples throughout the drying process, if it is possible todetect when and how cracking and deformation occurs and develops in specimens ofEucalyptus nitens from Chile. Based on this knowledge, better drying schedules canhopefully be developed to improve the yield and provide a higher end-quality of the sawntimber.

  • 188.
    Cristescu, Carmen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bonding of laminated veneers with heat and pressure only2006In: Proceedings of Ecowood 2006 / [ed] Fernando Caldeira Jorge, Porto: Fernando Pessoa University , 2006, p. 339-348Conference paper (Refereed)
    Abstract [en]

    A new engineered wood product was obtained by pressing several layers of veneers at high temperatures. Experiments with different pressing parameters were performed in a laboratory hot plate press on Fagus Sylvatica. Shear strengths test were run according to EN 314-1 and EN 314-2 “Plywood – Bonding qualities”. Samples were analysed with a digital camera to observe the change in colour and with a X-ray microdensitometry scanner to determine the density variation and profiles. Scanning Electron Microscopy (SEM) was used to study the modification of wood cell structure close to and inside the bonding zones. The results showed that the bonding properties of the laminates are good, better when veneers have the same grain direction. Beech veneer with red heartwood can improve its appearance if bonded with the technology presented.

  • 189.
    Cristescu, Carmen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bonding veneers using only heat and pressure: focus on bending and shear strength2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    A compact laminated board can be obtained by pressing layers of veneers with no other material or substance placed between them. The process does not require the use of steam pretreatment, surface activation methods, a gastight press, friction or adhesives. It strictly involves the heat and the pressure induced by the press in the veneers. The levels of temperature, pressure and time leading to the highest bending-strength values when material factors are held constant are investigated. The objective of optimizing the process is reached using response surface methodology for modelling and analysis. The parameter interactions are found to be significant.Photography, scanning, X-ray densitometry, light microscopy and scanning electron microscopy (SEM) are the methods used to visually analyse the final product. Densification and darkening are two of the effects observed.

  • 190.
    Cristescu, Carmen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Self-bonding of beech veneers2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents studies on the self-bonding of veneers, and investigations into the properties of boards obtained by hot-pressing beech veneers without adhesives. The raw material is pressed at temperatures from 200 to 250ºC, at pressures from 4 to 6 MPa and pressing times from 240 to 360 s. The hot-pressing of five layers of veneers results in a self-bonded, compressed, densified board, darker than the raw material. The manufacturing process was optimised using a statistical analysis, the response surface experimental design method. The input factors were the pressing parameters and the output factors were characteristics of the product, the raw material properties being kept constant. The results showed correlations between the pressing parameters, especially temperature, as input data and the physical and mechanical properties as responses. Resistance to water absorption and swelling as well as shear strength, bending strength, and hardness were all enhanced by more severe pressing conditions. All the samples pressed at 250ºC became water-resistant while samples pressed at 200ºC delaminated rapidly in water. It was found that the colour of the edges can be used as an indication of the hardness. Chemical investigations were performed on samples taken from veneers (raw material), bond-lines and inner parts of pressed veneer. A High-Performance Liquid Chromatography (HPLC) analysis was used to detect and compare the levels of water-soluble monosaccharides (glucose and fructose) in the veneer before pressing and the levels of 5-hydroxymethyl-furfural (HMF) and furfural in boards. From the results obtained in this thesis it is suggested, that besides other degraded compounds of hemicelluloses, the monosaccharides were transformed into hydroxymethyl-furfural during hot-pressing that could further participate in forming new browning compounds that are related to the bonding phenomenon. The UV spectroscopic analysis to evaluate the content of water-soluble phenols showed that the bond-line had a higher amount of conjugated phenols than the inner veneer suggesting a migration of degraded lignin towards the veneer surfaces during pressing. A CP/MAS 13C NMR study on the solid material showed that the presence of β-ether structures and methoxyl groups in lignin was higher in the bond-line, supporting the hypothesis of a migration of lignin and possibly a condensation reaction occurring at higher temperatures, explaining the water-resistance property acquired by the boards.In a comparative study, oxidative activation with hydrogen peroxide and ferrous sulfate as a catalyst was performed before pressing. Boards made from beech veneer subjected to the pre-treatment step showed a greater mass loss, a lower thickness swelling but also a somewhat lower shear strength. For beech veneers such an oxidative pre-treatment step could be used to gain water-resistant boards pressed at lower pressing temperatures or shorter times than those needed to bond untreated veneers. Scots pine veneers were found to be less suitable for self-bonding than beech veneers. Boards of Scots pine hot-pressed without the oxidative pre-treatment delaminated in water, whereas, under the same pressing conditions, boards made from pre-treated veneers showed a water-resistant bond-line.

  • 191. Cristescu, Carmen
    et al.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Changes in content of furfurals and phenols in self-bonded laminated boards2013In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 3, p. 4056-4071Article in journal (Refereed)
    Abstract [en]

    Pressing beech veneers at high temperatures has been shown to be a reliable method for manufacturing laminated boards without adhesives. The reasons behind the self-bonding phenomenon as well as the causes of the waterproof character gained by the boards being pressed at 250 degrees C were investigated. Water leachates from the dried and the hot-pressed veneers were analysed by UV-spectroscopy, high-performance liquid chromatography (HPLC), and solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C NMR). Press-plate temperatures during hot pressing were 200, 225, and 250 degrees C. After pressing, an increased content of 5-(hydroxymethyl) furfural (not at 250 degrees C) and conjugated phenols was observed in the bonding lines (interfaces) compared to the inner part of veneers of the self-bonded boards. Furfural contents were low and relatively similar, but 5-(hydroxymethyl) furfural (HMF) showed an abrupt decrease in the bonding line when the temperature increased from 200 degrees C to 225 degrees C and especially to 250 degrees C. The contribution of caramelization to browning and bonding is suggested. In studies with CP/MAS 13C NMR, a higher content of phenolic units in beech lignin was observed during hot pressing at 225 degrees C. Homolytical cleavage of beta-O-4 structures in lignin as well as the condensation reactions involved are discussed

  • 192.
    Cristescu, Carmen
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Neyses, Benedikt
    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.
    Söderström, Ove
    Kungliga tekniska högskolan, KTH, KTH Byggnadsmateriallära.
    Modeling of the temperature distribution in self-bonded beech-veneer boards during hot pressing2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 97-103Article in journal (Refereed)
    Abstract [en]

    Auto-adhesion is a phenomenon that is in general related to the manufacture of wood-basedfibreboards, e.g. to the Masonite process or similar processes based on lignocellulosic raw materials.Auto-adhesion as a mechanism for the bonding of solid wood or veneer has not met with the sameindustrial success, but interest is increasing for environmental reasons and as a result of theincreasing cost of adhesives in wood products. The temperature in the laminate is crucial for the autoadhesionprocess that will result in bonding between veneers during hot-pressing. This paper presentsa model for the temperature evolution during the hot-pressing of a porous material, which wasdeveloped and verified for a five-veneer beech laminate pressed at a temperature of 250°C and apressure of 6MPa in an open system for 280 seconds. The result shows good agreement between themodel and the experimental temperature data during the hot-pressing. It can be concluded that a goodcontrol of the temperature evolution during the manufacture of adhesive-free veneer boards is of majorimportance to reach the target properties of the product.

  • 193.
    Cristescu, Carmen
    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.
    Self-bonding of veneers with heat and pressure: a full scale test2014In: 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, Skellefteå: Luleå tekniska universitet, 2014, p. 76-Conference paper (Refereed)
  • 194.
    Cristescu, Carmen
    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.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Influence of pressing parameters on mechanical and physical properties of self-bonded laminated beech boards2015In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, no 2, p. 205-214Article in journal (Refereed)
  • 195.
    Cristescu, Carmen
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Could colour predict hardness of hot-ptressed self-laminated beech boards2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 150-156Article in journal (Refereed)
    Abstract [en]

    Laminated self-bonded densified boards were obtained by pressing five veneers of beech(Fagus sylvatica L.) parallel-grain-oriented, without adhesive and without surface activation. Theboards were pressed according to an experimental design based on fifteen different combinations ofpressing parameters: temperature (200, 225, and 250°C), pressure (4, 5, and 6MPa), and time (240,300, and 360s). The image of the 40 board edges (radial sections) was analysed with ImageJ softwarein the red-green-blue (RGB) colour space. Brinell hardness tests were also performed. The resultsshow an almost linear relation between the brightness values (defined as the arithmetic mean of theRGB channels) and the Brinell hardness. It is suggested that brightness is a predictor of strength forself-bonded laminated boards.

  • 196.
    Cristescu, Carmen
    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.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Markers of quality in self-bonded beech boards2017Conference paper (Refereed)
    Abstract [en]

    A self-bonding phenomenon takes place when five layers of beech (Fagus SylvaticaL.) veneers are pressed at temperatures higher than 200ºC. If the pressing temperature between veneer surfaces reaches at least 225ºC during pressing and if the pressure applied is optimal, water-resistant bonds are formed between veneers. This study investigates the relation of thickness reduction (marker of compression) and mass loss (marker of heat treatment intensity) to boards quality. The effect of water and water vapour on the bondings between veneer in boards pressed at 200, 225 and 250ºC is studied. The conclusion is that pressing 5 layers of 2 mm rotary-cut beech veneer parallel-fibered at 225ºC, 5 MPa and 300 s leads to a thickness reduction of 33.4 % and mass loss of 1.23 %; in such boards bondings are not resistant to liquid water but are resistant to vapour after one adsorption-desorption cycle. When pressing at 250ºC, 5 MPa and 300 seconds, the thickness reduction is 50% and the mass loss 4%; in such boards no delamination was observed when soaked in water. Boards pressed athigher temperature show lower hygroscopicity. Their equilibrium moisture content (EMC) rangedbetween 3.6 and 7%. Based on the results of this study it ishypothesised that the decay resistance of self-bonded boards will increase when increasing the severity of the hot-pressing.

  • 197.
    Cristovao, Luis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Machining properties for some Mozambican wood species2010Licentiate thesis, comprehensive summary (Other academic)
  • 198.
    Cristovao, Luis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Machining properties of wood: Tool wear, cutting force and tensioning of blades2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cutting processes, in general, and wood cutting processes, in particular, are complex to explain and describe with many influencing factors. Wood, in contrast to man-made fabricated materials, is not a homogenous and distinct material, but a multifaceted and nonhomogeneous biological material. A fundamental understanding of wood cutting processes and the machining properties of wood can be obtained by investigating the interaction of wood properties, cutting tools and machining parameters. Such an understanding provides possibilities for improving product quality, increasing production efficiency, or otherwise improving the machining processes. The aim of this thesis was to find ways of improving the machining properties of some wood species, focusing on tool wear, cutting forces and the tensioning of circular sawblades. The studied wood species were five Mozambican tropical species, namely: Swartzia Madagascariensis (ironwood); Pseudolachnostylis maprounaefolia (ntholo); Sterculia appendiculata (metil); Acacia nigrescens (namuno); Pericopsis angolensis (muanga) and two main Swedish wood species: Pinus sylvestris L. (Scots pine); and Picea abies (L.) Karst. (Norway spruce). A series of experimental tests were conducted to determine the suitability of different cutting tool materials when machining these wood species. Machining tropical hardwood and Swedish frozen wood under winter conditions is still a challenge when it comes to the choice of which cutting tool material to use. Tool wear was used as a criterion to evaluate the performance of the cutting tool materials. Additionally, the relationship between tool wear and some chemical and physical properties for Mozambican tropical wood species was analysed. Different wear mechanisms were identified using a scanning electron microscope. It was concluded that tool hardness alone was not the only factor affecting tool wear; a certain amount of tool toughness was also needed to obtain low tool wear. The predominant wearing mechanisms for the tropical wood species tested were abrasion and edge-chipping. Furthermore, tropical hardwood species were subjected to cutting force tests. A standard single saw tooth, mounted on a piezoelectric load cell, was used to evaluate cutting forces. The theoretical approach used for the prediction of the main cutting forces was based on surface response methodology. Among the studied variables, chip thickness and cutting direction had the greatest effect on the main cutting force level, while wood density, moisture and rake angle had the least effect.Power consumption using double arbour circular saw machines was investigated. The experiments were carried out, under normal production, in two Swedish sawmills. The climb-sawing model in both sawmills was able to estimate the power consumption better than the counter-sawing model. Climb-sawing had higher power consumption than counter-sawing. The lowest power consumption was found using a higher overlap between circular sawblades. Finally, experimental and theoretical models to improve circular sawblade dynamic lateral stability were developed. Different methods for monitoring flatness and tensioning in circular sawblades for wood cutting were discussed. Additionally, the effects of the magnitude of the roller load, number of grooves and groove positions were tested. The roll-tensioning effects were evaluated by measuring the shift in natural frequencies of several vibration modes. Natural frequencies obtained with the finite element method were in good agreement with the experimental test results. The magnitude of the roller load, number of grooves, and groove positions all affected the natural frequencies.

  • 199.
    Cristovao, Luis
    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.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sitoe, Rui
    Eduardo Mondlane University.
    Main cutting force models for two species of tropical wood2011In: Proceedings of the 20th International Wood Machining Seminar, Skellefteå, 2011, p. 428-435Conference paper (Refereed)
  • 200. Cristovao, Luis
    et al.
    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.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Sitoe, Rui
    Main cutting force models for two species of tropical wood2012In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, no 3, p. 143-149Article in journal (Refereed)
    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.

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