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  • 251.
    Kupracz, P.
    et al.
    Gdansk Univ Technol, Poland.
    Wojcik, Natalia A.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Gdansk Univ Technol, Poland.
    Barczynski, R. J.
    Gdansk Univ Technol, Poland.
    A method of determination of electrical conduction mechanisms in complex amorphous materials2018In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 498, p. 223-227Article in journal (Refereed)
    Abstract [en]

    A novel approach to determine conduction mechanisms in complex amorphous materials was presented and tested on a real system. In the first step of the presented method, total electrical admittance of the material is analyzed in order to separate a couple of processes, each of which can be described by Jonscher's universal dielectric response. In the following step, a temperature dependence of dielectric response parameters of the processes is determined and compared with known models of conduction mechanisms in structural amorphous materials. Using this approach, a presence of two different conduction mechanisms describing electrical conductivity in a two-phase glass was described.

  • 252.
    Lenarciak, A.
    et al.
    Gdansk Univ Technol, Poland.
    Wójcik, Natalia A.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Gdansk Univ Technol, Poland.
    Kupracz, P.
    Gdansk Univ Technol, Poland;Polish Acad Sci, Poland.
    Strychalska-Nowak, J.
    Gdansk Univ Technol, Poland.
    Sobczak, Z.
    Gdansk Univ Technol, Poland.
    Przesniak-Welenc, M.
    Gdansk Univ Technol, Poland.
    Karczewski, J.
    Gdansk Univ Technol, Poland.
    Barczynski, R. J.
    Gdansk Univ Technol, Poland.
    Thermal, electrical, and magnetic properties of Fe2O3-PbO-SiO2 glass prepared by traditional melt-quenching and twin roller fast-cooling methods2019In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 135, article id 109010Article in journal (Refereed)
    Abstract [en]

    In this study, Fe-Pb-Si oxide glasses containing between 12.5 and 17.5 mol% Fe2O3 were prepared using two different methods comprising traditional melt-quenching and twin roller fast-cooling techniques. The topography and structure of the materials obtained were characterized by X-ray powder diffraction and scanning electron microscopy. All of the materials were found to be amorphous. The topography of most of the glasses comprised random or evenly distributed nanostructures, where the size and amount were dependent on the iron content and preparation technique. The thermal properties of the glasses were analyzed by differential scanning calorimetry, which showed that the glass transition temperatures varied between 529 degrees C and 552 degrees C. The electric conductivity and magnetic susceptibility of the glasses were analyzed by impedance spectroscopy and with an alternating current magnetic properties measurement system, respectively. The measurements of the electrical properties indicated a relatively low activation energy for direct current conductivity (similar to 0.5-0.68 eV), which is typical of the polaron hopping mechanism. All of the materials exhibited magnetic hysteresis loops and they were ferromagnetic.

  • 253.
    Li, Junqiu
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Physical and Mechanical Properties of Medite® MDF Exterior from Acetylated Wood Fibers2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Currently, the demand for wood-based panels has been growing solidly in European countries. Medium density fibreboard (MDF) manifests the potentialities for outstanding physical and mechanical properties. However, MDF from different fiber sources is normally designed for internal applications due to the poor moisture resistant capability. This study was conducted on acetylated MDF (Medite® MDF Exterior) to evaluate how physical (i.e. density, moisture content, dimensional stability, thickness swelling) and mechanical (i.e. modulus of elasticity, internal bonding strength before and after accelerated aging, bending stiffness and bending strength) properties behave at different relative humidity (i.e. 35 %, 65 % and 85 % RH at constant temperature of 20 ℃) levels. Bending stiffness was measured non-destructively by means of resonance method. The material used for control samples was commercial MDF. The size, quantity, conditioning and test method were followed in accordance with respective standards. The results showed that physical and mechanical properties were less influenced by Medite® MDF Exterior compared to commercial MDF. Medite® MDF Exterior were superior to commercial MDF in moisture resistance. Medite® MDF Exterior had more stable mechanical properties than commercial MDF with the changes of relative humidity.

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  • 254.
    Lindström, Per
    DNV GL Materials Laboratory, Norway ; University West.
    DNV Platform of Computational Welding Mechanics2013Report (Other academic)
    Abstract [en]

    This document presents the DNV Platform of Computational Welding Mechanics, CWM, with its associated CWM-methodology. That has been developed, validated and implemented as a part of DNV’s Technology Leadership program in the field of Structural Integrity and Materials Technology.A successful CWM implementation requires that the actual organisation has gained the knowledge and understanding of the following related topics:- Welding Engineering with an emphasis on the welding process and its thermodynamics- Weld process quality control such as calibration, validation as well as DAQ, (Data Acquisition)- Transient thermo-mechanical coupled FE-analyses and constitutive modelling- Computational platforms comprising the selection of hardware, operative system and FEM-code as well as suitable pre- and post-processing toolsFrom that perspective there is a lack of reliable and/or hands-on oriented CWM Engineering Handbooks and best recommended practices available on the market. For that sake is the DNV CWM-methodology and its hands on solutions presented.The CWM-methodology described can not only be used for residual stress assessments, as presented in this report. It can also be used for various applications such as assessment of used and/or proposed WPS, Welding Procedure Specifications as well as optimisation of the manufacturing and production process of integrated metallic structures.From the results of a parametric CWM-study have three (3) factors been identified to drive and/or contribute to the magnitude of the weld residual stresses in ship steel plate materials. The contributing and/or driving factors identified are the:- Thermal- and Mechanical Boundary Conditions during the production welding- Yield stress difference between the base- and the weld filler material- Weld heat input, Q, which affects the weld cooling time

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  • 255.
    Lindström, Per
    Chalmers University of Technology.
    Heat Transfer Prediction of In-Service Welding in a Forced Flow of Fluid2009In: Journal of Offshore Mechanics and Arctic Engineering-Transactions of The Asme, ISSN 0892-7219, E-ISSN 1528-896X, Vol. 131, no 3, p. 1-6, article id 031304Article in journal (Refereed)
    Abstract [en]

    An algorithm for heat transfer prediction of in-service welding operations in a forcedflow of fluid is presented. The algorithm presented is derived from Rosenthal’s 3D heatflow equation and boundary layer approximations. This was possible by the introductionof an apparent thermal conductivity kPL, which is a function of the boundary layer’s heattransfer coefficient f and the base material’s thickness . This implies that a weldcooling time tT1 /T2 in a forced flow of fluid can now be calculated by an ordinaryengineering calculator and thus enabling suitable welding parameters to be determined.The magnitude of kPLf , was established by regression analysis of results from aparametric finite element analysis series of a total number of 112 numerical simulations.Furthermore, the result of the regression analysis was validated and verified by a weldingexperiment series accomplished on an in-house designed and constructed in-servicewelding rig. The principle design of the welding rig as well as its instrumentation, a PCbased Data Acquisition system, is described. In addition, a method to measure the weldmetals cooling time tT1 /T2 by means of thermocouple elements is described. Finally,the algorithm presented in this study proved feasible for industrial in-service weldingoperations of fine-grained Carbon and Carbon–Manganese steels with a maximum CarbonEquivalent (IIW) (CE) of 0.32.

  • 256.
    Lindström, Per
    Högskolan Väst.
    Improved CWM platform for modelling welding procedures and their effects on structural behaviour2015Doctoral thesis, monograph (Other academic)
    Abstract [en]

    A welding procedure specification is the document describing how a weld joint should be constructed. Arc weld processes are characterized by transient thermal behavior, leading to rapid changes in material properties and dynamic interaction between weld and base material. The objective of the project is to explore how the use of an improved CWM-platform affects representative stress and strain fields in order to assess welding procedure qualification records. Forthis project, the accumulated thermal and mechanical influences from the first run to the final run are brought forward, in one and the same meshed geometrical model. Both the thermal and mechanical material model of the platform are designed to be used for modelling of the base- and weld material,promoting the simulation of the intricate combination of the thermal, elastic,and plastic strains on the plastic strain hardening and the formation of residual stress fields. The output of the simulation is mainly weld cooling times, residual stresses, and deformations. This analysis is taken further by examining how residual stresses influence crack driving force under elastic and plastic loading. In addition, the output from the simulations can be used to assess the realism of the proposed welding parameters. The main experimental welding procedure examined comes from the IIW RSDP Round Robin Phase II benchmark project, where the main aim was to benchmark residual stress simulations. This work was found to contain many applicable challenges of a CWM-analysis project.

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  • 257. Lindström, Per
    et al.
    Caprace, J.-D
    Mishra, B.
    Pires, F.
    Roland, F.
    Schipperen, I.
    Andric, J.
    Li, L
    Osawa, N
    Doig, R.
    Remes, H.
    Kim, M. H.
    Materials and Fabrication Technology: Committee v.32015In: Proceedings of the 19th International Ship and Offshore Structures Congress, Volume 2: Committee v.3 Materials and Fabrication Technology / [ed] Carlos Guedes Soares & Yordan Garbatov, EH Leiden, Nederlands: CRC Press, 2015, 1, Vol. 2, p. 619-698, article id V.3Chapter in book (Other academic)
    Abstract [en]

    Due to the past crises, the shipbuilding and offshore industry has realised that new innovative designs and design and production methods are necessary to decrease operational costs, production costs and emissions,while meeting the changing rules and regulations. This ISSC-V.3 report is discussing recent developmentin materials and fabrication technology applied to ship and offshore structures.Chapter 2 focuses on worldwide trends in materials and fabrication methods. Developments in metallicand non-metallic structural materials are dealt in Chapter 3. Advances in fabrication and joining technologiessuch as welding are increasing. Some main areas of applications and research in those areas aredescribed in Chapter 4. Innovative development about corrosion protection systems are presented inChapter 5 while Chapter 6 give an overview about the application of production simulation and virtualreality to improve the production management of ship and offshore structures.The ISSC-V.3 technical committee has performed a benchmark to define a Best Practice Guideline touse Computational Welding Mechanics tools (CWM) in shipbuilding and offshore industry. To achievethis objective various experimental welding tests have been performed in order to give a reference point.Both the residual welding distortions and residual stresses have been compared between numerical simulationsand welding experiments for a common “T” welded assembly used in the shipbuilding industry.However, it has been decided to publish the results of this study in a separate document. Nevertheless, Chapter 7 of this report presents the state of the art as well as the experimental test case that has been analysed.

  • 258.
    Lindström, Per
    et al.
    University West ; DNV GL Materials Laboratory, Norway.
    Jonsson, Anders
    DYNAmore Nordic AB .
    Jernberg, Anders
    DYNAmore Nordic AB .
    Östby, Erling
    DNV GL Materials Laboratory, Norway.
    Non-linear fracture mechanics in LS-DYNA and LS-PrePost2015In: European LS-DYNA Conference 2015: Conference Papers, Würzburg: DYNAmore GmbH , 2015Conference paper (Other academic)
    Abstract [en]

    Fracture mechanics provides an engineering framework for assessing the consequences of defects instructures. In linear elastic fracture mechanics (LEFM), stress intensity factors KI, KII and KIII are usedfor characterizing the stress singularity at the crack tip, which arises from the theory of linear elasticity.Crack growth is assumed to occur when KI exceeds the fracture toughness KC. LEFM can be usefulfor brittle materials, or when the size of the plastic zone is small compared to global dimensions. In non-linear fracture mechanics (EPFM), an energy based criterion is used for assessing the risk forcrack growth: if the energy release rate at the crack tip exceeds what is required for creating newsurfaces in the material, crack growth will occur. Under certain assumptions the energy release rate atthe crack tip can be calculated by a path independent integral, the so-called J-integral. In modernFE-based fracture mechanics applied to practical design, the structure under consideration ismodelled, including cracks at specific locations, and the J-integral values are computed and used asdesign criteria. From a numerics viewpoint, the J-integral has many appealing properties: it can beevaluated from the far-field solution, which reduces numerical errors that may arise close to the cracktip, and the expected path-independence can to some extent be used as a quick check on solutionvalidity.Evaluation of the J-integral from LS-DYNA simulation results has been implemented as a postprocessingtool in LS-PrePost, including consistent treatment of residual stresses. The implementationcovers both 2D (plane stress / plane strain) and 3D applications, using the virtual crack-tip extension(VCE) method. The tool is accessible both via the LS-PrePost GUI and via command file interface.

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  • 259.
    Lindström, Per
    et al.
    Chalmers University of Technology.
    Ulfvarson, Anders
    Chalmers University of Technology.
    An Experimental Rig For Verification of The Mechanical Properties of Welds Produced at In-Service Welding2003In: Proceedings of OMAE’03 22nd International Conference on Offshore Mechanics and Arctic Engineering, June 8 – 13, 2003, Cancun, Mexico, ASME Press, 2003, Vol. 3, p. 57-65, article id 37105Conference paper (Refereed)
    Abstract [en]

    The strength of a weld joint is determined by its geometry and its metallurgic structure, which is dependent on the cooling rate, its chemical composition and the original grain size of the base material. During in-service welding of structures affected by a forced flow of fluid on its reversed side the cooling rate depends on the fluid’s boundary layer, the material’s thickness and the heat input of the welding process. Currently, the calculation of the cooling rate during in-service welding is made by means of numerical methods such as the Finite Element Method, FEM. Through the introduction of an apparent thermal conductivity, kPL, it possible to determine the cooling rate for specific welding parameters by means of Rosenthal’s equation. This can be done with a standard pocket calculator.An experimental rig for measurement of the heat transfer during the in-service welding of structures affected by a forced flow of fluid on its reversed side has been designed and built. The physical principles of welding on plates affected by a forced flow of fluid on their reverse side are the same as for welding on the circumference of a pipe containing a forced flow of fluid. In the rig, the required boundary layer is built up in a pipe system by means of a pump. As the flow and the temperature of the fluid can be controlled to simulate the specific heat transfer, it is now possible to verify the values of the apparent thermal conductivity, kPL, that were calculated

    values of the apparent thermal conductivity, kPL, for various configurations.For the purpose of evaluation and qualification of in-service Welding Procedures Specifications, WPS, the sponsors of the research project use the experimental rig.

  • 260.
    Lindström, Per
    et al.
    Chalmers University of Technology.
    Ulfvarson, Anders
    Chalmers University of Technology.
    Weld Repair of Shell Plates During Seagoing Operations2002In: Proceedings of OMAE’02; 21st International Conference on Offshore Mechanics and Artic Engineering: June 23-28, 2002, Oslo, Norway, ASME Press, 2002, Vol. 3, p. 499-506Conference paper (Refereed)
    Abstract [en]

    An algorithm to estimate the cooling rate of welding seamson the shell plating of a ship, below the waterline, while it is onvoyage has been derived. The demand for this technique hasarisen from the wish of ship operators to make it possible forthe safe repair of ship structures without taking them out ofoperation. [1] The strength of the shell plating after welding isdetermined by its metallurgic structure, which is dependent onthe cooling rate, its chemical composition and the original grainsize of the base material. [2] The cooling rate for this type ofwelding seam depends on the velocity of the water flow, thedistance from the bow, the thickness of the plate, and the heatfrom the heat input of the welding. The algorithm makes itpossible to calculate the cooling rate for a base material affectedby a forced flow of fluid by means of Rosenthal’s equation andthus enabling suitable welding parameters to be determined.As the welding parameters can be chosen to fit the specificrepair to be made, it is now possible to determine the suitabilityof a welding procedure in advance. The algorithm is applicablewhen determining welding parameters at Hot-Tappingoperations as well, where the base material is affected by aforced flow of fluid. A number of experiments have beenperformed and the results support the theoretical model. Theresearch project continues with the aim of finding an algorithmto include the enhanced cooling rate due to the layer of boilingfluid on the back of the base material. A method to improve themeasurements of the most important parameter in the algorithmhas been developed and makes it possible to build up aquantitative database of typical values for various configurations.

  • 261.
    Lützhøft, Hans-Christian Holten
    et al.
    Technical University of Denmark, Denmark.
    Birch, Heidi
    Technical University of Denmark, Denmark.
    Eriksson, Eva
    Technical University of Denmark, Denmark.
    Mikkelsen, Peter Steen
    Technical University of Denmark, Denmark.
    Comparing chemical analysis with literature studies to identify micropollutants to be treated or upstream source controlled in a catchment of Copenhagen (DK)2012In: 6th SETAC World Congress/SETAC Europe 22nd Annual Meeting: abstract book, Berlin: Society of Environmental Toxicology and Chemistry , 2012, p. 287-288Conference paper (Other academic)
  • 262.
    Maletič, Damjan
    et al.
    University of Maribor, Slovenia.
    Lovrenčič, Viktor
    C&G D.O.O. Ljubljana, Slovenia.
    Maletič, Matjaž
    University of Maribor, Slovenia.
    Al-Najjar, Basim
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Gomišček, Boštjan
    University of Maribor, Slovenia.
    Maintenance Solutions for Cost-Effective Production: A Case Study in a Paper Mill2015In: Engineering Asset Management - Systems : Professional Practices and Certification: Proceedings of the 8th World Congress on Engineering Asset Management (WCEAM 2013) & the 3rd International Conference on Utility Management & Safety (ICUMAS) / [ed] Tse, PW; Mathew, J; Wong, K; Lam, R; Ko, CN, Springer, 2015, p. 375-385Conference paper (Refereed)
    Abstract [en]

    For companies, in order to stay competitive, it is necessary to continuously increase the effectiveness and efficiency of their production processes. Therefore the purpose of this chapter is to discuss the role of maintenance in achieving the competitive advantages using cost-effectiveness aspect of maintenance process. In this regard, the chapter illustrates/discusses the impact of mechanical and electrical failures on company’s business on an example of a paper mill where processes are running 24/7. Thus, this paper presents the role of vibration-based maintenance (VBM) in enhancing the production and maintenance performance continuously and cost-effectively. Using empirical data collected from a paper mill case study, we found that company could avoid the profit losses even to a greater extent if it would improve the effectiveness of the VBM. With respect to the electrical causes of failures, a live working technique for improving the reliability and availability of the paper machine is proposed. Therefore, maintenance solution concerning the paper machine is suggested and discussed as well as potential benefits are highlighted. The results supported the notion that there is a positive association between the reduction of the unplanned stoppages and potential savings. The results have also shown that there is a need for more systematic approach, and a more holistic view of the maintenance function for establishing and running a cost-effective maintenance policy in the paper mill under consideration.

  • 263.
    Mukherjee, Debasis Pradip
    et al.
    University of Calcutta, India.
    Kumar Das, Sudip
    University of Calcutta, India.
    Influence of TiO2 content on the crystallization and microstructure of machinable glass-ceramics2016In: Journal of Asian Ceramic Societies, ISSN 2187-0764, Vol. 4, no 1, p. 55-60Article in journal (Refereed)
    Abstract [en]

    Glasses based on the SiO2–Al2O3–MgO–K2O–B2O3–MgF2 system added with TiO2were synthesized and characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The results showed that by increasing the TiO2content, glass transition temperature (Tg), both the crystallization peak temperature (TpIand TpII) and activation energy (E) increased. The interconnected large blocky card-like crystals were identified as fluorophlogopite as a major crystalline phase for all three glass-ceramic specimens by (XRD) and subsequently confirmed by SEM. The Vickers hardness (Hv) value for glass-ceramic specimens decreases with progressively increasing TiO2 content (1–10 wt%) and Titania containing MGT-3 glass-ceramic specimen with interconnected large blocky card-like fluorophlogopite mica crystals possess lower Hv (4.26 GPa) as well as good machinability (m = 0.12) useable for machinable applications. The study shows that Titania promoted initial crystallization of glass and can be used as an effective nucleting agent.

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  • 264.
    Mukherjee, Debasis Pradip
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Univ Calcutta, India .
    Molla, Atiar Rahaman
    CSIR Cent Glass & Ceram Res Inst, India.
    Das, Sudip Kumar
    Univ Calcutta, India.
    The influence of MgF2 content on the characteristic improvement of machinable glass ceramics2016In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 433, p. 51-59Article in journal (Refereed)
    Abstract [en]

    The influence of MgF2 on the various properties like crystalline behavior, microstructure phases, hardness etc. in the SiO2-Al2O3-MgO-K2O-B2O3 glass system has been investigated. Three batches of glass system were synthesized and characterized by differential scanning calorimetry (DSC), coefficient of thermal expansion (CTE), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) equipped with energy dispersion X-ray spectroscopy (EDS). DSC study reveals that with the increase in MgF2 content the glass transition temperature (T-g) and first crystallization peak temperature (T-p(I)) decreased whilst the second crystallization peak temperature (T-p(II)) slightly increased. The CTE of the glasses is found to be in the ranges 634-6.40 x 10(-6) K-1 (50-400 degrees C). The activation energy (E-c) and frequency factor (v) both increase with increasing MgF2 content. The three-dimensional crystal growth is observed. The mica crystals are identified as fluorophlogopite, the predominant crystal phase for all the three glass specimens heat treated at 1050 degrees C. Vickers hardness values decrease with increasing amount of fluorine content and it gives better machinability. (C) 2015 Elsevier B.V. All rights reserved.

  • 265.
    Murin, Justin
    et al.
    Slovak Univ Technol Bratislava, Slovakia.
    Aminbaghai, Mehdi
    Vienna Univ Technol, Austria.
    Hrabovsky, Juraj
    Slovak Univ Technol Bratislava, Slovakia.
    Balduzzi, Giuseppe
    Vienna Univ Technol, Austria.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Mang, Herbert A.
    Vienna Univ Technol, Austria;Tongji Univ, Peoples Republic of China.
    Torsional warping eigenmodes of FGM beams with longitudinally varying material properties2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 175, p. 912-925Article in journal (Refereed)
    Abstract [en]

    In this paper, the influence of torsional warping of thin-walled cross-sections of twisted Functionally Graded Material (FGM) beams with a longitudinal polynomial variation of the material properties on their eigenvibrations is investigated, considering the secondary deformations due to the angle of twist. The transfer relations needed for the transfer matrix method are derived. Based on them, the local finite element equations of the twisted FGM beam are established. The warping part of the first derivative of the twist angle, caused by the bimoment, is considered as an additional degree of freedom at the beam nodes. The focus of the numerical investigation, with and without consideration of the Deformation due to the Secondary Torsional Moment (STMDE), is on modal analysis of straight cantilever FGM beams with doubly symmetric open and closed cross sections. The influence of the longitudinal variation of the material properties and the secondary torsion moment on the eigenfrequencies is investigated. The obtained results are compared with the ones calculated by a very fine mesh of standard solid and warping beam finite elements.

  • 266.
    Möncke, Doris
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Alfred University, USA;Theoretical and Physical Chemistry Institute, Greece.
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Kamitsos, Efstratios
    Theoretical and Physical Chemistry Institute, Greece.
    Anion polarizabilities in oxynitride glasses: Establishing a common optical basicity scale2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084Article in journal (Refereed)
    Abstract [en]

    Inspired by the work of John Duffy on optical basicity of oxyfluoride glasses, we apply here the conceptof optical basicity to oxynitride systems. While in the original work of Duffy and Ingram the basicity of amedium could be probed by s2 ions like Pb2+, the low energy intrinsic absorption edge of nitridecontainingsystems does not allow the use of such probe ions. This study uses therefore experimentaldata on refractive index and density of alkaline earth and rare earth containing silicate oxynitride glasses,prepared by the authors or taken from the literature. In addition, literature reports on experimental orcalculated refractive index, density and polarizability data are used to compare pure nitride systems, e.g.bulk or thin film materials that are either crystalline or glassy. We compare simple and complex nitridesystems with their oxygen counterparts, by calculating their optical basicity using the chemicalcomposition as well as the established relationship between optical basicity, L, and electronicpolarizability in oxide systems. Our results on oxynitride systems are in good agreement with Duffy’sprevious work on oxyfluoride glasses and indicate that the optical basicity varies for the isoelectronicanions in nitrides, oxides and fluorides (N3:O2:F) of a cation Mm+ as follows: L(MFm) = 1/2L(M2Om) =1/3L(M3Nm). Using this relation for CaO, for which the optical basicity was set as unity by Duffy andIngram, one has L(CaF2) = 0.50, L(CaO) = 1.00 and L(Ca3N2) = 1.50. The optical basicity of complexnitrides can therefore be calculated by the same method established for oxides using the equivalentfractions and the basicity of the constituent nitrides. The relationship between nitride polarizability aNand basicity L(nitride) was found to be linear, with L(nitride) = 0.39aN 0.14 where aN is given in Å3.

  • 267.
    Möncke, Doris
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, Greece.
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Wójcik, Natalia A.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Gdańsk University of Technology, Poland.
    Palles, Damitris
    National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, Greece.
    Kamitsos, Efstratios
    National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, Greece.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    IR and Raman study of oxy-nitride glasses2018In: Presented at Glass and the Meeting of Minds  (SGT18), Cambridge, UK (2nd -5th September 2018), 2018, p. 54-Conference paper (Refereed)
  • 268.
    Möncke, Doris
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Fed Univ Sao Carlos UFSCar, Brazil;Natl Hellen Res Fdn, Greece.
    Jiusti, Jeanini
    Fed Univ Sao Carlos UFSCar, Brazil.
    Silva, Lais Dantas
    Fed Univ Sao Carlos UFSCar, Brazil.
    Martins Rodrigues, Ana Candida
    Fed Univ Sao Carlos UFSCar, Brazil.
    Long-term stability of laser-induced defects in (fluoride-)phosphate glasses doped with W, Mo, Ta, Nb and Zr ions2018In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 498, p. 401-414Article in journal (Refereed)
    Abstract [en]

    Laser-induced defects in glasses are of considerable interest for many applications from optics to photonics. The importance of low-level impurities of polyvalent ions in aiding defect formation has been identified early on. (Fluoride-)phosphate glasses are used today as laser materials, waveguides, amplifiers and luminescing materials, all sensitive to a change of the materials transmission by the interaction with light during application. To better understand the processes of defect generation and recovery, a systematic comparison of defect formation in various glasses and for various radiation sources and dopants has been conducted over the last decades. Here we will focus on (fluoride-) phosphate glasses doped with 50 to 5000 ppm of the 4d and 5d ions Zr, Nb, Ta, Mo and W. Glasses were melted under air or under reducing conditions in order to shift the redox equilibrium of the dopants before irradiation with either the 193 nm or 248 nm excimer laser. Only for W, Mo and Nb reduced ion species were confirmed by optical and/or ESR spectroscopy in the pre-irradiated glasses. However, irradiation showed for all metaphosphates the presence of reduced dopant species (W5+, Mo5+, Ta4+, Nb4+, Zr3+), acting as extrinsic hole centers (HC) after being photo-oxidized by laser irradiation to the fully oxidized d ions (Mn+)(+)-HC. Only for Ta5+ with its (Ta5+)(-)-electron center (EC), photo-reduction to the tetravalent ion was observed. Defect recovery was followed up to 16 years after the irradiation experiments, showing that most (Mn+)(+)-HC were very stable, while intrinsic HC either recombined with EC or converted into extrinsic (Mn+)(+)-HC. Due to ubiquitous iron impurities, even these high purity glasses with iron levels of 5-10 ppm or less, showed the formation of (Fe2+)(+)-HC.

  • 269.
    Nicklisch, Felix
    et al.
    Technische Universität Dresden, Germany.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Weller, Bernhard
    Technische Universität Dresden, Germany.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Joint study on material properties of adhesives to be used in load-bearing timber-glass composite elements2014In: Glass | Facade | Energy / [ed] Jens Schneider, Bernhard Weller, Technische Uni Dresden , 2014, p. 271-280Conference paper (Refereed)
    Abstract [en]

    Beyond its transparency, glass offers a large potential to fulfill load-bearing functions. Timber-glass composite elements take advantage of the high stiffness and strength of glass. At the same time the post-breakage behavior of the composite element increases significantly compared to the brittle failure of a pure glass. The current study relates to timber-glass composites where the composite action is obtained via a linear bondline connecting the glass pane to a timber frame. The full potential of these composite elements arises from the use of adhesives of medium and high stiffness which exhibit rather small deformations compared to e.g. structural silicones. A central objective of the research is the assessment and the optimization of the bondline properties with respect to stiffness of the adhesive. The paper summarizes the results of an in-depth study on commercially available adhesives and evaluates their general suitability in timber-glass composites.

    The material properties of the adhesives were determined by thorough mechanical testing of the bulk material in the first place under varying conditions, typically encountered in façades. The potential use in glass-timber composites was then evaluated using small bonded specimens comprising birch plywood or massive pine wood in combination with soda-lime glass. Failure modes were categorized in order to ascertain the influence of the timber strength on the load-bearing capacity.

    In order to guarantee reliable results from various sources, parts of the tests were executed repeatedly at different laboratories. Results were compared and validated throughout the project. Hence the results of this study provide a reliable basis for material models used in e.g. numerical analysis and engineered design solutions. The study presented here is part of the WoodWisdomNet project “LBTGC - Load Bearing Timber Glass Composites”

  • 270.
    Nielsen, Katrine
    et al.
    Technical University of Denmark, Denmark.
    Mikkelsen, Peter Steen
    Technical University of Denmark, Denmark.
    Baun, Anders
    Technical University of Denmark, Denmark.
    Eriksson, Eva
    Technical University of Denmark, Denmark.
    Sorption of PAHs to humic acid- and iron(III)carbonate particles by using passive dosing vials for investigating the transport of organic contamination in stormwater runoff2013In: Interdisciplinary Discourse on Current Environmental Challenges, Krakow: SETAC , 2013Conference paper (Other academic)
    Abstract [en]

    During the last decades, the growing urbanisation a nd increasing anthropogenic activities in urban areas have turned urban stormwater runoff int o a surface water quality contamination problem. The concerns of urban stormwater runoff as a source of contamination in the receiving surface water (lakes, rivers or sea) have been raised by researchers throughout the world (e.g. Broman et. al., 1987, and Xanthopoulos et. al., 1990), and have in Europe gained increased interest in relation to the implementatio n of the Water Framework Directive (WFD, 2000/60/EC). Particles (often defined as >0.45 μm) has been foun d to facilitate transport of organic contaminants and metals in stormwater runoff system s, but little is known about the role of the colloidal fraction including nano-sized particl es (0.001-1 μm). Based on the large specific surface area of colloids and nanosized particles, t heir abundance, and knowledge about their facilitated transport of persistent organic polluti on in natural waters, they are likely to diminish the efficiency of engineered treatment sys tems unless appropriately accounted for. In this work organic and inorganic nanosized partic les were investigated for their ability to sorb polycyclic aromatic hydrocarbons (PAH’s) in an aqueous solution. These particles were used as indicators for stormwater particles which a re diverse in size and composition. For controlling the sorption onto the particles, passiv e doing vials were used (Birch et. al., 2010). Using passive dosing vials gives the possible to co ntrol freely dissolved analyte by equilibrium partitioning from a preloaded silicone membrane. It has been found that the presence of humic acid particles (80 nm) leads to an increasing amount of two PAHs (fluoranthene and phenanthrene) in the suspension. For iron(III)carbo nate particles (22 nm) sorption experiments are ongoing. Based on these results and a literature review, the importance of including particulate fractions for surface water q uality assessment in relation to the WFD will be discussed.

  • 271.
    Nilsson, Erik
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Kling, Kristoffer
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Konceptutveckling åt Kompostföretaget Balans2007Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The following rapport deals with the product development and construction of a compost reactor. The work started in late March 2007 to be concluded in early June.

    Since the construction group were given relatively free hands and was striding to come up with something revolutionary. Traditional brainstorming and a method called “Morphological chart” were used when developing the first basic concepts. These concepts were reviewed before the company, which picked out one of the ideas. Because of the size of the project the development was broken down in to single components. This way a basic structure for development has been created to make it easier for a new construction team to continue the work.

    This work resulted in a highly developed concept with the possibility for further construction. Some of the composts parts are still in a basic development stadium. Because material, surface roughness and tolerances not have been chosen, any construction drawings could not be made. These have been replaced with detailed sketches.

  • 272.
    Nilsson, Josefin A.
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Characteristics of un-barked small-dimensioned birch for furniture and interior applications2015In: Proceedings of the XXVIIth International Conference Research for Furniture Industry, September 2015, Turkey, Gazi University , 2015, p. 175-181Conference paper (Other academic)
    Abstract [en]

    Many interior and furniture applications today use the natural aspects of wooden materials as a sales advantage. Defects such as knots, colour variations and rough surfaces are called rustic, natural or vintage and will be considered as an appreciated feature by the consumers. This approach changes the traditional view of wood quality for technical uses, and also the industrial processing of the material. As a consequence, more variables of the material than before must be handled in the production. A specific challenge in the furniture industry is to treat the raw materials under this view with as small volume losses as possible. One way of decreasing losses could be achieved by fewer processing steps. The present study aims at exploring the possibility to relate the dimensions of the trees already in the forest in relation to specific furniture components, and furthermore to leave the bark on for creating specific aesthetical characteristics to the end product. In Nordic countries, birch wood has gained interest in furniture and interior applications due to its unique aesthetic qualities. In today’s forestry industry, the small-dimensioned material from harvesting operations of birch forests is normally used by the pulp industry or as fire-wood. For the interior and furniture industries these fractions may be a new source of raw material supply. However, a proper utilization of the material requires a better knowledge of its properties. The potential of using un-barked material in round form also sets special requirements in the process. The present study presents results from initial testing concerning the behaviour of the bark in round wood pieces. For the experiments, round specimens of downy birch (Betula pubescens Ehrh.) measuring 450 mm in length and with varying diameters from 30 to 80 mm at the top were used. The green wood was dried with and without bark as to study the drying velocity in relation to dimensions. The bark was studied in respect of changes in bonding to the wood and its characteristics. The preliminary results are promising for using the material in interior and furniture applications. However, there are still some shortcomings to be addressed in the future, such as the impact of the bark in the drying process as well as the bark bonding.

  • 273. Olek, Wiesław
    et al.
    Kifetew, Girma
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Bonanski, Jan T.
    Marklund, Erik
    Effects of cell wall ultrastructure on the transverse anisotropy of wood shrinkage2012In: Experimental and Computational Micro-Characterization Techniques in Wood Mechanics –COST Action FP0802, 2012Conference paper (Refereed)
  • 274.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology. SP Technical Research Institute of Sweden.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Prediction of timber bending strength and in-member cross-sectional stiffness vartiation on basis of local wood fibre orientation2013In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, no 3, p. 319-333Article in journal (Refereed)
    Abstract [en]

    Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3600 mm, a coefficient of determination as high as 0.68-0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.

  • 275.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Förfarande och anordning för utvärdering av en bräda av trä2014Patent (Other (popular science, discussion, etc.))
    Abstract [sv]

    Föreliggande redogörelse avser en metod och en anordning för utvärdering av en bräda av trä med en ländriktning. Data som indikerar fiberorienteringen över brädans yta inhämtas och för ett antal underpartier hos brädan bestäms en nominell, lokal elasticitetsmodul, MOE, på basis av nämnda fiberorienteringsdata och en nominell materialparameter. En nominell global MOE i längdriktningen för träbrädan i sin helhet genereras och jämförs med en sekundär global MOE. På basis av nämnda fiberorienteringsdata och denna jämförelse genereras en uppskattad lokal elasticitetsmodul, MOE, i nämnda längdriktning för ett flertal underpartier. Dessa data kan användas för exempelvis tillförlitlig hållfasthetsgradering av träbrädor.

  • 276.
    Olsson, P. A. T.
    et al.
    Malmö University.
    Kese, K.
    Studsvik Nuclear Corporation.
    Kroon, Martin
    Malmö University ; Royal Institute of Technology.
    Holston, A-M Alvarez
    Studsvik Nuclear Corporation.
    Ab initio-based fracture toughness estimates and transgranular traction-separation modelling of zirconium hydrides2015In: Modelling and Simulation in Materials Science and Engineering, ISSN 0965-0393, E-ISSN 1361-651X, Vol. 23, no 4, article id 045015Article in journal (Refereed)
    Abstract [en]

    In this work we report the results of an ab initio study of the transgranular fracture toughness and cleavage of brittle zirconium hydrides. We use the Griffith–Irwin relation to assess the fracture toughness using calculated surface energy and estimated isotropic Voigt–Reuss–Hill averages of the elastic constants. The calculated fracture toughness values are found to concur well with experimental data, which implies that fracture is dominated by cleavage failure. To investigate the cleavage energetics, we model the decohesion process. To describe the interplanar interaction we adopt Rose's universal binding energy relation, which is found to reproduce the behaviour accurately. The modelling shows that the work of fracture and ductility decreases with increasing hydrogen content.

  • 277.
    Olsson, Pär A.T.
    et al.
    Malmö University.
    Mrovec, Matous
    b Fraunhofer Institute for Mechanics of Materials (IWM), Germany ; Karlsruhe Institute of Technology, Germany .
    Kroon, Martin
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. Malmö University ; Royal Institute of Technology, (KTH).
    First principles characterisation of brittle transgranular fracture of titanium hydrides2016In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 118, p. 362-373Article in journal (Refereed)
    Abstract [en]

    In this work we have studied transgranular cleavage and the fracture toughness of titanium hydrides by means of quantum mechanical calculations based on density functional theory. The calculations show that the surface energy decreases and the unstable stacking fault energy increases with increasing hydrogen content. This is consistent with experimental findings of brittle behaviour of titanium hydrides at low temperatures. Based on Griffith-Irwin theory we estimate the fracture toughness of the hydrides to be of the order of 1 MPa⋅m1/2, which concurs well with experimental data. To investigate the cleavage energetics, we analyse the decohesion at various crystallographic planes and determine the traction-separation laws based on the Rose's extended universal binding energy relation. The calculations predict that the peak stresses do not depend on the hydrogen content of the phases, but it is rather dependent on the crystallographic cleavage direction. However, it is found that the work of fracture decreases with increasing hydrogen content, which is an indication of hydrogen induced bond weakening in the material.

  • 278.
    Ormarsson, Sigurdur
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Chalmers University of Technology, Sweden.
    Johansson, Marie
    Chalmers University of Technology, Sweden.
    Finite element simulation of growth stress formation and related board distortions resulting from sawing and forced drying2006In: New Zealand Journal of Forestry Science, ISSN 0048-0134, E-ISSN 1179-5395, Vol. 36, no 2, p. 408-423Article in journal (Refereed)
    Abstract [en]

    Matching timber quality with end-user requirements is a major research issue and lack of straightness in timber is the most frequent complaint worldwide. The final distortion of timber boards is caused mostly by moisture-related deformations and growth stresses that develop during growth of the tree, but how much the growth rate and growth stresses affect the final shape stability is not fully understood. A finite element analysis in which stress development during tree growth was simulated was performed with the aim of better understanding how growth stresses are generated. The tree growth model was formulated in terms of large strain settings (large changes in volume), whereas the material model for stress development was based on the theory of small strains. An earlier three-dimensional distortion model was developed further for studying the influence of growth stresses on final distortion of the board. The results showed that growth stresses clearly vary during tree growth and they also form a large stress gradient from pith to bark. This itself can result in significant bow and crook deformation when the log is sawed into boards.

  • 279.
    Paz-Garcia, Juan Manuel
    et al.
    Technical University of Denmark, Denmark.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Ottosen, Lisbeth M.
    Technical University of Denmark, Denmark.
    Ribeiro, A. B.
    New University of Lisbon, Portugal.
    Rodriguez-Maroto, J. M.
    University of Málaga, Spain.
    Influence of the Chemical Interactions on the Removal Rate of Different Salts in Electrokinetic Desalination Processes2011In: Salt Weathering on Buildings and Stone Sculptures, University of Cyprus , 2011, , p. 8p. 373-380Conference paper (Other academic)
    Abstract [en]

    Electrokinetic desalination techniques have been successfully applied for the prevention of salt-induced deterioration problems of masonry and other construction materials. A mathematical model for electrochemical desalination treatments is described, based on the Poisson-Nernst-Planck system of equations and accounting for the chemical interactions between the species in the pore solution and the solid matrix. Due to their high abundance in the natural environment, chlorides, nitrates and sulfates are considered the main ions responsible to the salt decay processes in buildings materials and sculptures. Simulations of the desalination treatment of brick samples contaminated with these target contaminants are shown. The influence of the chemical interactions on the efficiency is highlighted in the results.

  • 280.
    Pivnenko, Kostyantyn
    et al.
    Technical University of Denmark, Denmark.
    Eriksson, Eva
    Technical University of Denmark, Denmark.
    Astrup, Thomas Fruergaard
    Technical University of Denmark, Denmark.
    Presence of potentially critical substances in waste paper2013In: Proceedings Sardinia 2013: fourteenth international waste management and landfill symposium, Cagliari, Italy: CISA Publisher , 2013Conference paper (Refereed)
    Abstract [en]

    The paper industry accounts for a significant share of the chemicals consumed by the industrial sector. Most of the chemicals used are additives, i.e. chemical substances added during pulp and paper preparation and final product manufacturing (conversion and printing) in order to facilitate the process itself as well as the quality or functionality of the final product. Such additives may be re-introduced to the paper production process once waste paper is recycled, leading to their accumulation and spreading in newly manufactured paper and board products. This study aimed at identification of the critical additives potentially present in paper products and quantification of a selected group of additives (Mineral Oil Hydrocarbons) in waste paper and board source segregated from Danish municipal solid waste.

  • 281.
    Qian, Yang
    et al.
    Luleå University of Technology.
    Karlsson, Olov
    Luleå University of Technology.
    Ahmed, Sheikh Ali
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Dimensional Stability and Water Repellency of European Aspen Improved by Oxidized Carbohydrates.2013In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 1, p. 487-498Article in journal (Refereed)
    Abstract [en]

    Small samples from European aspen (Populus tremula L.) were impregnated with carbohydrates oxidized by Fenton's reagent using water in a vacuum, followed by heating in an oven at 103 °C. An antiswelling efficiency (ASE) of around 45% for wood treated with oxidized glucose and 35% for wood treated with oxidized sucrose was obtained. Samples treated with oxidized carbohydrates gave water repellent effectiveness (WRE) values over 35%. The decrease in cell wall thickness during impregnation was about 18% less in the presence of oxidized glucose than samples only treated with Fenton's reagent. An ASE of 20% for the wood samples that had been treated with oxidized glucose was obtained after 7 days of soaking in water. The reasons for the improvement in dimensional stability are discussed in this work.

  • 282.
    Risonarta, Victor Yuardi
    et al.
    Darma Cendika Catholic University, Indonesia.
    Anggono, Juliana
    Petra Christian University, Indonesia.
    Suhendra, Yosias Michael
    Petra Christian University, Indonesia.
    Nugrowibowo, Setyo
    Walisongo Gempol School of Technology, Indonesia.
    Jani, Yahya
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Strategy to improve recycling yield of aluminium cans2019In: E3S Web of Conferences / [ed] R.H. Setyobudi, F.D. Suprianto, M. Mel, O. Anne, P. Soni, T. Turkadze, Y. Jani & Z. Vincēviča-Gaile, EDP Sciences, 2019, Vol. 130, p. 1-8, article id 01033Conference paper (Refereed)
    Abstract [en]

    Millions of canned drinks are consumed everyday globally and their wastes create an enviromental issue. Fortunately, the cans are made from aluminium (Al) so that it can be recycled. There are two main keypoints existing during the recycling process of Al cans, i.e. the aluminium loss or low Al-yield and low recycling yield. This work outlines the strategies to improve the recycling perfomance for Al beverage cans, i.e. by adding drossing flux, applying improved melting strategy, and cans decoating prior to melting. Drossing flux was added to assist the detachment of Al from the slag. Another improved melting strategy was worked out by decreasing exposure time cans to the furnace atmosphere during melting. All those above strategies result in an increase of recycle yield in a range of 4 % to 5 %.

  • 283.
    Sanati, Mehri
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Bioenergiteknik.
    Synthesis, Properties, and Applications of Oxide Nanomaterials: Gas Sensors2007Book (Other academic)
  • 284.
    Sanati, Mehri
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Strand, Michael
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Nanoparticles for long-term stable, more selective MISiCFET gas sensors2005In: Sensors and Actuators B, ISSN 0925-4005, Vol. 107, no 2, p. 831-838Article in journal (Refereed)
    Abstract [en]

    Synthesis of metal-oxide nanoparticles and utilization of these particles as gate materials for field-effect sensor devices is reported. Improved

    selectivity to specific gases is expected by modulating the size of the oxide nanoparticles or impregnating them with catalytic metals. Another

    objective is to improve the long-term thermal stability of the sensors, since the metal loaded nanoparticles may prevent thermally induced

    restructuring of the gate layer, which is often a problematic issue for the catalytic metal layers. Because of its reasonably high electrical

    conductivity, which is especially important for the capacitive gas sensors, ruthenium dioxide has been identified to be one of the potential

    candidates as gate material for the field-effect sensor devices. Interestingly, this material has been found to change its resistivity in different

    gaseous ambients. When used as a gate material, sensitivity to reducing gases has been observed for the RuO2/SiO2/4H-SiC capacitors.

    Changes in the resistivity of the films due to various gas exposures have also been recorded. Morphological studies of nanoparticles (SiO2

    and Al2O3), loaded or impregnated with catalytic metals (e.g. Pt), have been performed.

  • 285.
    Schweigler, Michael
    Vienna University of Technology.
    A numerical model for slip curves of dowel connections and its application to timber structures2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wood as a natural and renewable material currently experiences a revival as structural building material. New technologies and a new design standard request appropriate, modern design methods for timber structures. Particularly, the design of modern timber connections is of importance since more challenging timber constructions demand ambitious connections. Most connections in timber structures are compliant in the sense that relative deformations between the connected structural elements occur during load transfer. In particular dowel connections exhibit this behavior since load transfer in dowel connections is based on the compliant embedment behavior of stiff steel dowels in wood.

    The aim of this thesis is to develop a model for a consistent calculation of the load-deformation relationship of connections. Additionally, this model is applied to timber structures to study the influence of compliant connections on the structural behavior. As a basis for the modeling of dowel connections, properties of single-dowel connections are presented. Different responses of wood in case of different loading directions, as well as several models for the calculation of single-dowel slip curves are discussed. Significant differences in the predicted load-deformation behavior of single-dowels can be observed among these approaches. A sub-model is used to determine realistic single-dowel slip curves for arbitrary connection configurations. Furthermore, the state-of-the-art approach for the determination of connection slip curves of multi-dowel connections is discussed. The restriction of this approach to some specific design situations is highlighted. These limitations of the current design approach are the motivation to develop a model for the calculation of slip curves of multi-dowel connections. This model enables a straight forward determination of member forces and connection slip curves for an arbitrary set of deformations. The single calculation steps and the feasibility of application on arbitrary connection configurations are discussed. Furthermore, a modification of the model to determine the deformation and force distribution within the connection for specific member forces is presented.

    Finally, the model is applied to different connections to illustrate their behavior for simple design examples. Moreover, connection slip curves have been implemented in the structural analysis of a static indetermined system in order to illustrate the necessity of considering the compliance of connections in the design of timber structures. It is shown that negligence of the connection slip may lead to uneconomic or even unsafe timber structures. Furthermore, the importance of an exact definition of the connection slip curves is discussed. Even insignificant differences from standard configurations may lead to remarkable changes in the connection behavior and, consequently, in the behavior of the structure. Moreover, a considerable influence of the used method to describe the single-dowel behavior on the behavior of the connection and, consequently, on the structural behavior has been found.

  • 286.
    Schweigler, Michael
    Vienna University of Technology.
    Nonlinear modeling of reinforced dowel joints in timber structures: a combined experimental-numerical study2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Steel dowels are indispensable elements for the design of joints in modern timber structures. Dowels are broadly used because of their flexibility in design and easy assembling on-site, as well as due to their advantageous mechanical behavior. Recent developments in reinforcement techniques allow for designing ductile dowel joints, which exhibit nonlinear slip behavior. However, currently applied limit state approaches for calculation of connection strength are not able to fully exploit the potential of dowel joints. This calls for development of more advanced calculation methods, which was aimed for in this thesis.

    For thorough understanding of the complex mechanical behavior of dowel connections, application of a so-called multiscale approach is advantageous. Thereby, nonlinear loaddeformation behavior of dowel connections is studied on different length scales, from the scale of connection components, up to the joint level. The aim of this thesis was to exploit knowledge from lower scales in models that finally allow for nonlinear analysis of timber structures. In the work at hand, this was achieved by a combined experimental-numerical analysis.

    Experimental studies on the nonlinear embedment slip of ductile dowel connections, and its relation to the orthotropic material behavior of wood, was one of the objectives of this work. Breaking new ground by testing up to large dowel displacements, at various angles to the grain, for unconstrained and constrained lateral displacement conditions, required development of new testing procedures and test setups. Test results gave access to nonlinear embedment slip curves and showed their dependence on loading direction and lateral displacement conditions.

    In the next step, embedment slip data were exploited in modeling of single-dowel connections. Beam-on-nonlinear foundation modeling was applied for this purpose. Validation of connection tests and a parameter study not only highlighted suitability of the calculation method, but allowed for gaining insight into limit states. Thus, beam-on-foundation modeling was found to be an attractive alternative to advanced 3D FEM models for engineering design.

    Parameterized equations for regression analysis of nonlinear slip curves, and interaction curves describing the grain angle dependence of mechanical parameters, were summarized in a literature review. With these equations at hand, a multi-dimensional parameterization method for the nonlinear slip as a function of the load-to-grain angle was developed. This method was applied to experimental data derived in embedment and single-dowel connection tests as well as in simulations. Analytical equations for connection slip are expected to facilitate engineering modeling at the single-dowel connection and joint level, respectively.

    Joint modeling aimed at establishing a calculation method suitable for engineering design with an attractive trade-off between modeling effort, calculation time and accuracy. This was tackled by a semi-analytical model based on nonlinear elastic springs for the dowel slip and rigid connection members. Thereby, global joint slip, and thus stiffness and strength of joints, as well as local load distribution within joints can be predicted. This model proved to be suitable for single-dowel-based and joint-based design concepts. Calculation examples showed pronounced influence of loading direction dependence and nonlinearity of dowel slip on local load distribution, as well as on global joint slip. Influence of interaction between internal forces on the joint stiffness became obvious from structural analysis with nonlinear joint slip.

    This work covers a combined experimental-numerical analysis of the slip behavior of ductile dowel joints, from the wood embedment and steel dowel bending behavior, the single-dowel slip, to the joint behavior, with final application in nonlinear structural analysis. Presented models predicted nonlinear slip with suitable accuracy and efficiency. Application of nonlinear joint slip in structural analysis showed the potential of ductile dowel joints, which could be exploited in engineering design by the herein presented multiscale modeling strategy.

  • 287.
    Silva, Ana
    et al.
    University West, Sweden.
    De Backer, Jeroen
    University West, Sweden.
    Bolmsjö, Gunnar
    University West, Sweden.
    Analysis of Plunge and Dwell Parameters of Robotic FSW Using TWT Temperature Feedback Control2016In: Proceedings of 11th International Symposium on Friction Stir Welding, Cambridge: TWI Ltd , 2016, p. 1-11Conference paper (Other academic)
    Abstract [en]

    Friction stir welding (FSW) and variants of the process have generated high interest in many industries due to its several advantages such as low distortion, superior mechanical properties over arc welding and the possibility of joining dissimilar materials. Increased complexity of industrial applications require a better control of the welding process in order to guarantee a consistent weld quality. This can be achieved by implementing feedback control based on sensor measurements. Previous studies have demonstrated a direct effect of weld temperature on the mechanical properties of FSW joints, [1], and therefore, temperature is chosen as primary process variable in this study.A new method for temperature measurement in FSW referred to as the Tool-WorkpieceThermocouple (TWT) method has recently been developed by De Backer. The TWT method is based on thermoelectric effect and allows accurate, fast and industrially suitable temperature monitoring during welding, without the need for thermocouples inside the tool [2]. This paper presents an application of the TWT method for optimisation of the initial weld phases, plunge and dwell, operation in conventional FSW, which can also be applied to friction stir spot welding (FSSW). An analysis of the operation parameters by using feedback temperature control is presented aiming to better control of the initial weld phases through temperature feedback.

    The introduction of the TWT temperature sensor provides additional process information during welding. Fast data acquisition gives opportunity to differentiate different process phases: contact of probe tip with workpiece surface; plunge phase; dwell phase. This would be followed by tool retraction for FSSW or tool traverse phase for FSW.The effect of the plunge parameters on weld temperature and duration of each phase were studied for the purpose of optimising the process with respect to process (i) robustness, (ii)time, (iii) robot deflection and (iv) quality. By using temperature feedback, it is possible to control the plunge phase to reach a predefined weld temperature, avoiding overheating of the material, which is known to have a detrimental influence on mechanical properties. The work presented in this paper is an important step in the optimization of robotic FSSW and FSW.

  • 288.
    Silva, Ana
    et al.
    Högskolan Väst, Sweden.
    De Backer, Jeroen
    Högskolan Väst, Sweden.
    Bolmsjö, Gunnar
    University West, Sweden.
    TWT method for temperature measurement during FSW process2015In: The 4th international Conference on scientific and technical advances on friction stir welding & processing, 2015, p. 95-98Conference paper (Refereed)
    Abstract [en]

    Friction stir weld (FSW) has generated a high interest in many industry segments in the past 20 years. Along with new industrial challenges, more complex geometries and high quality demands, a better control of the welding process is required. New approaches using temperature controlled welding have been proposed and revealed good results. However, few temperature measurement methods exist which are accurate, fast and industrially suitable. A new and simple sensor solution, the Tool-Workpiece Thermocouple (TWT) method, based on the thermoelectric effect was recently developed.This paper presents a calibration solution for the TWT method where the TWT temperature is compared to calibrated thermocouples inside the tool. The correspondence between both methods is shown. Furthermore, a calibration strategy in different aluminium alloys is proposed, which is based on plunge iterations. This allows accurate temperature monitoring during welding, without the need for thermocouples inside the tool.

  • 289.
    Sjöberg, Daniel
    et al.
    Lund University, Sweden.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Gustafsson, Mats
    Lund University, Sweden.
    Convex optimization for optimal realization of material properties2014In: 2014 International Conference on Electromagnetics in Advanced Applications (ICEAA), 3-8 Aug. 2014, Palm Beach, IEEE Press, 2014, p. 782-785Conference paper (Refereed)
    Abstract [en]

    We show how the best passive approximation to a given target material or structure can be found byconvex optimization. The approach is based on a representation of positive real functions, where some of the parameters can be given physical relevance by comparison to low- and high-frequency asymptotics of the material or structure under study. A number of different optimization problems can be formulated, which generalizes previous approaches using sum rules.

  • 290.
    Sjökvist, Tinh
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Niklewski, Jonas
    Lund university, Sweden.
    Blom, Åsa
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Effect of wood density and cracks on the moisture content of coated Norway spruce (Picea abies (L.) Karst.)2019In: Wood and Fiber Science, ISSN 0735-6161, Vol. 51, no 2, p. 160-172Article in journal (Refereed)
    Abstract [en]

    A protective coating is often used on the cladding of wooden facades to limit the absorption of moisture. Low wood moisture content (MC) is essential to obtain satisfactory durability performance. Wood density is known to influence the water sorption and crack formation of uncoated wood. However, the effect of density on the aforementioned behaviors of coated spruce is not yet fully understood. Six-years of data on the crack formation and the MC variation of outdoor exposed panels are analyzed in this article. The outdoor test was complemented by a subsequent laboratory experiment, wherein the MC variation was monitored at different depths on the board during artificial water spraying. The aim of this research was to increase the knowledge about how wood density and aging affect the water sorption of coated spruce through the crack formation. The results indicated that wood density had an impact on the overall sorption behavior of coated spruce. Low-density spruce contributed to faster water absorption and desorption processes than coated samples with higher density. However, the observed correlation to density was limited to a condition with an intact coating. High-density characteristics contributed to more crack formation, and the density–sorption relationship reversed with a cracked coating. A cracked coating caused a strong local increase in the MC of the wood at the location of the cracks. Weather-exposed replicates without cracks had a higher MC in the core of the board compared with the value beneath the coating. The higher MC is probably due to the water sorption of the uncoated backside of the panel. Such an occurrence raised awareness for future studies to account for multidimensional sorption behavior from all sides of the panel. The local difference in MC also raises awareness for future studies to investigate local MC variations (as opposed to the global average of the panel) in research on the durability of coated wood.

  • 291.
    Stendahl, Matti
    et al.
    Swedish University of Agricultural Sciences, Uppsala.
    Eliasson, Lars
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Integrated production of semi-finished components in sawmills, part II: Management of internal operations.2013In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, no 1, p. 12-30Article in journal (Refereed)
    Abstract [en]

    Recently, several Swedish sawmills have taken over production of components from customers in the furniture, joinery and house-manufacturing industries. The purpose of this study was to identify key factors in management of internal operations for sawmills with this strategy. A multiple case study design, based on face-to-face interviews with Swedish sawmill practitioners and on various forms of secondary data, produced comprehensive research information. Starting integrated production of components is a demanding strategy for sawmills. It requires deep knowledge about the customer and qualified skills in advanced further-processing of sawn wood. The complexity of quality management, production planning and cost calculation increases, and investments in processing equipment and customer relations reduce strategic flexibility. The diverging material flow complicates sawmills' possibilities to economize on scale, and they must instead economize on other factors, such as scope, combined operations and internal control. New tools for production follow-up and control, for production planning, for analysis of product profitability and for strategic partnership analysis are requested by practitioners. But, even if new analysis tools would facilitate better analysis and management of operations, the willingness and ability to innovate and learn among the personnel emerges as a key factor for success.

  • 292.
    Stendahl, Matti
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    McCluskey, Denise
    Swedish University of Agricultural Sciences, Sweden.
    Eliasson, Lars
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Integrated production of semi-finished components in sawmills, part I: External interactions2013In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, no 4, p. 253-270Article in journal (Refereed)
    Abstract [en]

    In a changing business landscape, where globalization and new customer requirements create new business opportunities, some Swedish sawmills have taken over the production of components from their industrial customers. In light of the emerging network-centric perspective on business, sawmill managers' perceptions about component customers' operational requirements, customer interaction processes, and their sawmills' offerings are researched and discussed in this article. A multiple case study design, based on face-to-face interviews with Swedish sawmill managers and on various forms of secondary data, produced comprehensive information about sawmills' interaction processes with component purchasing customers. Thematic data coding facilitated the assessment of the research information in relation to the conceptual and empirical findings of previous research. The findings of the study indicate that more process orientation in housing-, joinery-, and furniture-manufacturing implies an opportunity for sawmills to make service-based offerings including not only physical goods, but also administrative services, logistics, and expert advice. The results of the study confirm the network-centric perspective on business where value is created through the interaction between firms. However, noteworthy barriers in the form of process-, culture-, as well as socially related factors at customer firms must be considered.

  • 293.
    Stenudd, Stefan
    Member, Forest Products Society.
    Color response in silver birch during kiln-drying2004In: Forest products journal, ISSN 0015-7473, Vol. 54, no 6, p. 31-36Article in journal (Refereed)
    Abstract [en]

    Color change in silver birch caused by kiln-drying is a major down-grading factor and has substantial economical impact on high value furniture and flooring production. This study investigates the color responses to process parameters at different stages in the drying process. Samples were dried in a climate chamber and laboratory kilns and the color of dry wood was registered according to the CIE L*C*h color system. The results show that during the capillary drying phase (moisture content > 55 %) time is more important than temperature. Swift initial drying even at elevated temperatures increases the lightness and decreases the saturation. The major color changes occur later on, during the diffusive drying phase from approximately 30 to 20 percent moisture content. Here a combination of temperature, time, and initial moisture content is decisive for the final wood color. Swift drying in both stages even at moderately elevated temperatures results in a highly desirable brighter color.

  • 294.
    Stenudd, Stefan
    Linköping University.
    Colour changes in birch and beech during kilndrying2001In: Proceedings of the 7th International IUFRO Wood DryingConference, 2001, p. 300-305Conference paper (Refereed)
    Abstract [en]

    The aim of this study was to investigate the colour responses of Silver Birch (Betula pendula Roth.) and Beech(Fagus sylvatica L.) during conventional kiln-drying at industrial used conditions. The response of dryingtemperature, relative humidity, initial moisture content and board thickness on wood colour was investigated in two24 factorial designed experiments. The method was used to investigate and rank the effects of the variables and allpossible combinations of the variables with a minimum of tests. A total number of 224 clear green sapwood samplesdivided in to 32 groups were kiln-dried below 20% in a climate chamber, followed by room climate drying toapproximately 8%. Colour measurements were conducted on dry planed samples using a photoelectric colorimeterand results were expressed in the CIE L* (lightness) C* (chroma) h (hue) colour space. A comparison was also madewith 32 samples dried in room climate from green to 8%, differences were calculated and expressed as CIE (ΔE*ab)effects. The factorial experiments used high and low level for investigating the variables: temperature (60/30C),relative humidity (82/62%), initial moisture content (green/30%) and wood thickness (16/10 mm).Experimental results showed that drying temperature is the most important factor for the colour responses in theinvestigated intervals for both birch and beech. The second most important factor, for both species, was thickness ofthe wood. Relative humidity was found to be the third most important factor. Both species reacted in a similar way toincreasing temperature, thicker dimensions and high relative humidity. The wood colour became darker, moresaturated and redder compared to the reference material. The colour response effects were larger on birch comparedto beech.

  • 295.
    Stenudd, Stefan
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Colour Response in Drying of Nordic Hardwoods2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Colour and appearance of hardwood are of great importance for the interiorand furniture industry. The widespread use of transparent surface treatmentand a fashion that prescribe light colour on many species, means that deviationfrom the ideal have considerable impact on the industrial operations. Kilndrying is generally regarded as the process that has the greatest impact on thecolour of Nordic hardwood species. The lack of satisfactory explanation modelsfor many types of discoloration, however, complicates the control of the dryingprocess.This thesis is an attempt to increase the knowledge of which factors thatcontrol the appearance of some commonly found discolorations associated withdrying of beech, birch and oak. The main focus is on convection drying but alsothe influence of timber storage, pre-steaming and press drying has beeninvestigated for individual species. The studies have been conducted ascomparative studies based on design of experiments in which the colour wasdetermined using a colorimeter.Results show that reddish and dark discoloration of beech and birch duringconvective drying is mainly dependent on the temperature and time of exposurewhen the local moisture content exceeds the fibre saturation point. Theconversion of naturally occurring substances in birch into coloured compoundsis not due to active precursors created at high moisture content levels duringthe subsequent drying at low moisture content levels. Interior grey stain inbeech is caused by slow initial drying at low temperatures. Log storage in coldwinter and spring climate does not cause discoloration in beech. Birch becomeslighter when press-dried at high temperatures, resulting in a colour comparableto that of traditionally kiln dried wood. Steaming of oak before kiln dryingreduce the presence of brown discoloration, a general darkening of the woodoccurs at temperatures above 50°C.

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  • 296.
    Stenudd, Stefan
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Colour response of Silver birch to press drying2003In: Proceedings of the 8th International IUFRO Wood DryingConference, 2003, p. 449-454Conference paper (Refereed)
    Abstract [en]

    Press drying is a rapid drying technique capable of reducing deformation, but also known to cause discolourationin some wood species. The colour of Silver birch is of great importance to the furniture and flooring industry, wherethe blond colour is highly appreciated. This study investigates the colour response in the core of 36 mm Silver birchsamples to the process variables: plate temperature, plate pressure and air pressure and to the material variable initialmoisture content. Short samples were press dried in a electrically heated laboratory press to approximately 10%moisture content and the interior colour of dry wood was registered according to the CIE L*C*h colour system. Theresults show that plate temperature is the most influential process variable controlling the wood colour. Hightemperature results in brighter more yellowish colour and reduced drying time. Other process and material variablesalso have some influence on the final colour but their contributions are smaller. Press drying of green wood at 170Cin normal atmospheric air pressure gave a wood colour comparable to that of conventionally kiln dried birch wood,only slightly darker and more reddish. The study indicates that press drying of Silver birch is possible from a colourperspective by careful selection of process parameters.

  • 297.
    Stenudd, Stefan
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Influence of moisture content, temperature and air humidity during kiln drying on the lightness of Silver birch (Betula pendula Roth.)2013Manuscript (preprint) (Other academic)
    Abstract [en]

    Discoloration of birch wood during kiln drying is a considerable problem for theindustry, since any deviation from the preferred bright whitish colour reduces theusability and value of the sawn timber. This study was conducted in an effort toincrease the understanding of how MC, temperature and air humidity influence silverbirch lightness. The air humidity was represented by the equilibrium moisturecontent (EMC). Within the investigated intervals of 20-70°C and 9-20% EMC, theCIELAB colorimetric responses, were measured at the surface and at depths of 1 and5 mm below the surface. The results showed that lightness reduction was mainlycontrolled by temperature when long as the local moisture content of wood (MC)exceeded the fibre saturation point (FSP). High temperature in combination withhigh EMC levels promote lightness reduction. Transformation of naturally occurringwood constituents into coloured substances takes place within hours and does notappear to be caused by process related precursors. This study showed that visuallydetectable darkening occurred in samples with a local MC exceeding the FSP whenexposed to drying temperatures higher than 40°C in combination with EMC levelsabove 15%.

  • 298.
    Stenudd, Stefan
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Influence of Pre-heating on Brown Discoloration whenDrying Oak Heartwood2005In: Proceedings of the 9th InternationalIUFRO Wood Drying Conference, 2005, p. 127-130Conference paper (Refereed)
    Abstract [en]

    General loss of lightness and brown discoloration of oak heartwood are major problems to the European woodindustry. In this investigation has the effect of pre-heating timber to 100°C prior to conventional kiln drying at 15, 35and 50°C been studied. Pre-heating significantly reduced the level of local brown discolouring streaks and spots aswell as slightly increasing the general lightness. Drying temperature has a major impact on the development of localbrown discoloration as higher temperature cause more discoloration. The thermal effect on general lightness is lessdistinct and a turning point seams to exist in the 40-50°C range above which the lightness is distinctly reduced.

  • 299.
    Sterley, Magdalena
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Characterisation of green-glued wood adhesive bonds2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The gluing of unseasoned wood, called green gluing, is a relatively new sawmill process, implying a radically changed order of material flow in the production of value-added wood-based products. It facilitates the enhancement of raw material recovery and value yield by integrating defect elimination and gluing already before kiln drying. The present study evaluates green glued adhesive bonds in flatwise glued beams and finger joints. The main part of this work deals with green gluing using a moisture curing polyurethane adhesive (PUR). Standardised test methods and specially designed, small scale, specimens were used for the determination of the strength, fracture energy and the ductility of both dry- and green glued bonds in tension and in shear. Using the small scale specimens it was possible to capture the complete stress versus deformation curves, including also their unloading part. An optical system for deformation measurement was used for the analysis of bond behaviour. The influence of moisture content during curing and temperature after curing on the adhesive chemical composition and on the mechanical properties was investigated. Furthermore, the moisture transport through the adhesive bond during curing was tested. Finally, microscopy studies were performed for analysis of bond morphology and fracture. The results show that two significant factors influence the shear strength of green glued bonds: wood density and adhesive spread rate. Bonds which fulfil the requirements according to EN 386 could be obtained within a wide range of process parameters. The small specimen tests showed that green glued PUR bonds can reach the same strength and fracture energy, both in shear and in tension, as dry glued bonds with the same adhesive amount. The local material properties of the bonds could be determined, thanks to the failure in the tests taking place within the adhesive bond itself and not in the wood. Following process factors were shown to cause lower bond strength: a) a low adhesive spread rate, b) high pressure and c) short pressing time in combination with low wood density and high moisture content. Moreover, the heat treatment of the cured PUR adhesive during drying influenced the chemical composition of the adhesive, providing for higher strength, stiffness and Tg of the adhesive, caused by an increased amount of highly ordered bidentate urea.

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  • 300.
    Sterley, Magdalena
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Gustafsson, Per Johan
    Lund University.
    Shear Fracture Characterisation of Green Glued Polyurethane Wood Adhesive Bonds at Various Moisture and Gluing Conditions2012In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, no 2, p. 93-100Article in journal (Refereed)
    Abstract [en]

    The shear fracture properties of green-glued one-component polyurethane (PUR) wood adhesive bonds subjected to kiln drying were investigated. The local shear strength and fracture energy of the wood adhesive bonds were determined from experimentally recorded complete shear stress versus deformation curves of the bond line. A stable test set-up and small specimens that were anti-symmetrically loaded were used in order to get a uniform and pure state of shear stress. Different moisture contents (MCs) and pressing times were investigated. The fracture properties of conventionally dry-glued wood adhesive bonds and of solid wood were used as reference. The results show that the fracture energy of green-glued bonds with PUR adhesive is dependent on the MC of wood and on the pressing time. The same fracture energy and strength can be obtained by green gluing as by dry gluing, but there seems to exist a maximum MC of sapwood, in the range between 78% and 160%, and a minimum pressing time, in the range between 3 h and 48 h, for which it can be achieved. Both dry- and green-glued polyurethane adhesive bonds were more ductile than solid wood.

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