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  • 1. Adlerborn, J
    et al.
    Björk, L
    Westman, Anna-Karin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Larker, H
    Particulate-reinforced ceramics densified by glass encapsulated HIP1991In: Hot isostatic pressing: Theory and applications / [ed] R J Schaefer; Melvin Linzer, Materials Park, Ohio: ASM International, 1991, 211-216 p.Conference paper (Refereed)
  • 2.
    Ah Shenga, Pedro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Luleå University of Technology.
    SAWING STRATEGIES FOR TROPICAL HARDWOOD SPECIES: Simulation studies based on industrial conditions of Mozambique2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The harvesting of Mozambique tropical hardwood species is considerable higher than the natural regrowth in the forest and the stock is decreasing drastically. Therefore, it is important to improve the material recovery when the wood is refined (i.e., in sawing and further refinement to products such as joineries, furniture etc.) to reduce the waste and to re-utilize efficiently the by-products to increase the added value. The wood processing industry is an important means to boost the industries in the rural areas and also to generate incomes for the local communities by creating jobs and business opportunities.

    The majority of the logging that can be used for sawmilling in Mozambique is exported as roundwood due to the inability of companies to meet the product standards set for export and to generate profit. The lack of capabilities of the local sawmills to generate profit, also foments the illegal logging because of the higher price of roundwood for export which contributes to increase the number of unlicensed individuals in harvesting. This threatens the law enforcement and thus the degradation of the local wood industry. An alternative to increase the profit and empower the local community could be to export more refined wood products such as sawn timber, parquet, and veneer instead of the roundwood.

    The objective of the work was to investigate alternative sawing strategies of tropical hardwood species that could increase the profitability of the Mozambique wood industry in general and at sawmill in particular. The subject was approached using a database of virtual logs and together with a sawing simulator. The thesis has two main focus areas: (1) creating the log database with the corresponding algorithms for sawing simulation, and (2) investigations of alternative sawing strategies.

    The first focus was to build the database of surface-scanned logs and develop the algorithm for the saw simulation. The results are a database of 15 logs models describing the logs outer shape in which 10 jambirre (Millettia stuhlmannii Taub.) and 5 umbila (Pterocarpus angolensis DC.), and the algorithm for the sawing simulation. The algorithm use “brute force” i.e., determines all volume yields of sawn timber from the combination of all settings of log-positioning parameters (offset, skew and rotation) and selects the maximum value of volume yield. From simulation, using three sawing patterns (cant-sawing, through-and-through sawing and square-sawing) combined with two positioning parameters (offset and rotation) it was found that the sawing pattern has great impact on volume yield and that the square-sawing gave higher yield followed by through-and-through sawing pattern.

    The second focus was on alternative sawing strategies; having in mind that the optimal volume yield is achieved by aid of computerized production systems and that these resources are not yet in use in Mozambique. Hence, the objective was to find the positioning parameters that can be set manually and improve the volume yield. The result have shown that the rotation is the most affecting parameter followed by offset and skew, and that the volume yield can decrease by between 7.7% and 12.5% from the optimal positioning when the logs are manually positioned with the knowledge about the optimal log position. In another study, using crook-up or horns-down positioning as alternative to the optimal positioning, the volume yield decreases by between 10% and 13% from the optimal positioning. By using bucked logs , the optimal volume yield increased by between 8% and 13% in relation to full lengths logs, and the volume yield of bucked logs when using crook up positioning decreases 2% in relation to optimal positioning of full length logs.

    It is concluded that there is an unexploited value potential in the wood chain which can be reached using alternative positioning and modern measurement techniques and that the grading of wood will facilitate and improve the sawing process.

  • 3.
    Ah Shenga, Pedro António
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    External Log Scanning for Optimizing Primary Breakdown of Tropical Hardwood Species2015Conference paper (Other academic)
    Abstract [en]

    The sawing of tropical hardwood species is a big challenge for sawmills in developing countries. In order to investigate sawing strategies and volume recovery of tropical hardwood species, a log shape database was created using a portable 3D laser scanner. The data were collected in Mozambique, where twelve Jambirre (Millettia stuhlmannii Taub.) and five Umbila (Pterocarpus angolensis DC) logs were scanned. The logs were selected among the most commercialized species and the crook was the main selection parameter. In addition, straight logs were incorporated as reference. A saw simulation Matlab algorithm that combines skew and rotation was developed. The results show that point cloud data from the 3D scanner provide detailed models of the external log geometry and accurately describe the log shapes and volumes. Preliminary results from breakdown simulation revealed that the through-and-through sawing pattern yields more than the cant saw pattern and that the increase in yield was almost the same for both species.

  • 4.
    Ah Shenga, Pedro António
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Simulated Breakdown of Two Tropical Hardwood Species2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, 450-456 p.Article in journal (Refereed)
    Abstract [en]

    A simulation study has been performed on a small log database of tropical hardwoods consisting of 10 Jambirre (Millettia stuhlmannii Taub.) and 5 Umbila (Pterocarpus angolensis D.C.) logs. The outer log shape was acquired by a 3D laser scanner before sawing and the heartwood content was estimated by measurement on images of the centre slabs after through-and-through sawing. Yield and value recovery using different sawing techniques and different sawing patterns, together with rotational and skew positioning errors, are presented. The results show that through-and-through sawing in the best rotation and skew positions tested improves the yield of Umbila logs by an average of 4.5 percentage points and Jambirre logs by 3.6 percentage points compared to cant sawing. It can be concluded that positioning and sawing patterns have a great influence on the yield and value recovery of these species and that log grade and species have an impact on the sawing pattern that should be used.

  • 5.
    Ah Shenga, Pedro António
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Simulation of Tropical Hardwood Processing: Sawing Methods, Log Positioning, and Outer Shape2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 4, 7640-7652 p.Article in journal (Refereed)
    Abstract [en]

    To increase understanding of breakdown strategies for Mozambican timber, simulations were carried out using different sawing patterns that can be alternatives to the low degree of refinement performed for export today. For the simulations, 3D models of 10 Jambirre and 5 Umbila logs were used. The log shape was described as a point cloud and was acquired by 3D-laser scanning of real logs. Three sawing patterns (cant-sawing, through-and-through sawing, and square-sawing) were studied in combination with the log positioning variables skew and rotation. The results showed that both positioning and choice of sawing pattern had a great influence on the volume yield. The results also showed that the log grade had an impact on the sawing pattern that should be used for a high volume yield. The volume yield could be increased by 3 percentage points by choosing alternative sawing patterns for fairly straight logs and by 6 percentage points for crooked logs, compared to the worst choice of sawing pattern.

  • 6.
    Ah Shenga, Pedro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    3D Phase-shift Laser Scanning of Log Shape2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 4, 7593-7605 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, a portable scanner to determine the 3D shape of logs was evaluated and compared with the measurement result of a computer tomography scanner. Focus was on the accuracy of the shape geometry representation. The objective is to find a feasible method to use for future data collection in Mozambique in order to build up a database of logs of tropical species for sawing simulations. The method chosen here was a 3D phase-shift laser scanner. Two logs, a birch log with bark and a Scots pine log without bark, were scanned, resulting in 450 cross sectional “images” of the pine log and 300 of the birch log. The areas of each point cloud cross section were calculated and compared to that of the corresponding computer tomography cross section. The average area difference between the two methods was 2.23% and 3.73%, with standard deviations of 1.54 and 0.91, for the Scots pine and birch logs, respectively. The differences in results between the two logs are discussed and had mainly to do with presence of bark and mantle surface evenness. Results show that the shape measurements derived from these methods were well correlated, which indicates the applicability of a 3D phase-shift laser scanning technology for gathering log data.

  • 7.
    Ah Shenga, Pedro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield2017In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 4, 257-262 p.Article in journal (Refereed)
    Abstract [en]

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

  • 8.
    Ah Shenga, Pedro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The Effect of Log Position Accuracy on the Volume Yield in Sawmilling of Tropical Hardwood2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, 9560-9571 p.Article in journal (Refereed)
    Abstract [en]

    This study investigated the effect of the positioning of the log before sawing on the volume yield of sawn timber from tropical hardwood species. Three positioning parameters were studied, the offset, skew, and rotation, combined with two sawing patterns of cant-sawing and through-and-through sawing. A database consisting of two tropical hardwood species with very different outer shapes, jambirre (Millettia stuhllmannii Taub.) and umbila (Pterocarpus angolensis DC.), was used to simulate the sawing process. The result of the simulation revealed that, according to the combined effect of offset, skew, and rotation positioning, the positioning of the log before sawing is extremely important to achieve a high volume yield of sawn timber. The positioning parameter that has the highest effect on the volume yield is the rotation, and the variation in the volume yield associated with a deviation in the positioning can reduce the volume yield of sawn timber by between 7.7% and 12.5%.

  • 9.
    Ah Shenga, Pedro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cristovao, Luis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A review of Mozambican wood exploitation: map of the processing chain2013In: Proceedings of the 21th International Wood Machining Semina: August 4th – 7th, Tsukuba International Congress Center, Japan, 2013, 293-301 p.Conference paper (Other academic)
  • 10.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cloutier, Alain
    Wood Research Center (CRB), Department of Wood and Forest Sciences, Faculty of Forestry, Geography and Geomatics, Laval University, Quebec.
    Fang, Chang-Hua
    Wood Research Center (CRB), Department of Wood and Forest Sciences, Faculty of Forestry, Geography and Geomatics, Laval University, Quebec.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Anatomical properties and process parameters affecting blister/blow formation in densified European aspen and downy birch sapwood boards by thermo-hygro-mechanical compression2013In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 48, no 24, 8571-8579 p.Article in journal (Refereed)
    Abstract [en]

    Approximately, 13.5 % of the standing volume of productive forest land in Sweden is covered by birch and aspen, which provides the vast potential to produce value-added products such as densified wood. This study shows whether it is possible to densify those species with a thermo-hygro-mechanical (THM) process using heat, steam, and pressure. In this process, transverse compression on thin European aspen (Populus tremula) and downy birch (Betula pubescens) boards was performed at 200 ºC with a maximum steam pressure of 550 kPa. To obtain a theoretical 50 % compression set, the press’s maximum hydraulic pressure ranged from 1.5 to 7.3 MPa. Preliminary tests showed that ~75 % of the birch boards produced defects (blisters/blows) while only 25 % of the aspen boards did. Mainly, radial delamination associated with internal checks in intrawall and transwall fractures caused small cracks (termed blisters) while blows are characterized by relatively larger areas of delamination visible as a bumpy surface on the panel. Anatomical investigations revealed that birch was more prone to those defects than aspen. However, those defects could be minimized by increasing the pre-treatment time during the THM processing.

  • 11.
    Ahmed, Sheikh Ali
    et al.
    Department of Forestry and Wood Technology, Faculty of Technology, Linnaeus University.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Blom, Åsa
    Department of Forestry and Wood Technology, Faculty of Technology, Linnaeus University.
    Effect of oil impregnation on water repellency, dimensional stability and mold susceptibility of thermally-modified European aspen and downy birch wood2017In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 63, no 1, 74-82 p.Article in journal (Refereed)
    Abstract [en]

    Conventional chemical wood preservatives have been banned or restricted in some applications due to human and animal toxicity and their adverse impact on the surrounding environment. New, low-environmental-impact wood treatments that still provide effective protection systems are needed to protect wood. Thermal modification of wood could reduce hygroscopicity, improve dimensional stability and enhance resistance to mold attack. The aim of this study is to investigate if these properties enhanced in thermally-modified (TM) wood through treatments with oils. In this study, TM European aspen (Populus tremula) and downy birch (Betula pubescens) wood were impregnated with three different types of oil: water-miscible commercial Elit Träskydd (Beckers oil with propiconazole and 3-iodo-2-propynyl butylcarbamate, IPBC), a pine tar formulation and 100% tung oil. The properties of oil-impregnated wood investigated were water repellency, dimensional stability and mold susceptibility. The treated wood especially with pine tar and tung oil, showed an increase in water repellency and dimensional stability. However, Beckers oil which contains biocides like propiconazole and IPBC, showed better protection against mold compared with pine tar and tung oil. To enhance the dimensional stability of the wood, pine tar and tung oil can be used, but these oil treatments did not significantly improve mold resistance rather sometimes enhanced the mold growth. Whereas, a significant anti-mold effect was observed on Beckers oil treated samples.

  • 12.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Dynamics of some vibro-impacting systems with amplitude constraints1995Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns the dynamics of some vibro-impacting systems with fixed or moving amplitude constraints. It is based on and includes five papers, marked A to E. Simple models of three different vibro-impacting systems with applications in the fields of impact hammers, granular flow and disk brakes in vehicles are analysed. A 2-DOF (two-degree-of-freedom) model of a threshold-limited impact hammer is studied (Paper A). The stability of a class of periodic motions is analysed. For some parameter values these periodic motions are found to be qualitatively similar to the ones observed for a corresponding 1-DOF system. At other parameter combinations, however, new kinds of periodic or chaotic motions can be observed. For low damping, phenomena resembling antiresonance for linear systems can also be observed. Granular shear flows show a transitional behaviour in the rapid flow regime as the shear speed or the concentration of the grains is varied. The motion can, for example, change from smooth and orderly to erratic and turbulent. Some aspects of this transitional behaviour in granular shear flow are studied numerically, analytically and experimentally (Papers B, C and D). Simple vibro-impacting models are suggested to get some analytical insight into the dynamics of shear layers. Results from a 1-DOF model show that for high forcing frequencies, which correspond to high shear speeds, periodic as well as chaotic motions can exist, whereas, for low forcing frequencies the vibrations are completely damped out to a stationary state (Paper B). Stability of this stationary state is studied analytically (Paper C), and experimentally (Paper D), where the motions of granular particles in a transparent shear cell are followed by using video techniques. For low shear speeds a single shear layer adjacent to the bottom boundary of the shear cell is observed. As the shear speed is increased, a transition to a random like state involving many layers is found to occur. In order to understand the phenomenon of squeal in disk brakes, a 3-DOF model is suggested to simulate the dynamics of a brake pad. The region of contact between the brake pad and the disk is described by using a coefficient of friction and distributed stiffness. The brake pad is allowed to have adjustable support locations and possibilities of impacts with its surroundings. The equilibrium state of the pad is determined by using a static analysis. The assumption is that the instability of this stationary state is a possible explanation of squeal, therefore, the stability is analysed in detail. Examples of different kinds of pad motions are presented. A rich variety of motions are found to exist including periodic, seemingly chaotic, stationary behaviour in slip, vibrations with full contact with the disk, stick-slip and impacts.

  • 13.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Multiple solutions in a rub-impact Jeffcott rotor2004In: Extended abstracts, proceedings: 10th international symposium on transport phenomena and dynamics of rotating machinery / [ed] Dieter Bohn, Aachen: Inst. of steam and gas turbines, RWTH , 2004Conference paper (Refereed)
  • 14.
    Aidanpää, Jan-Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Gustavsson, Rolf K.
    Vattenfall, VRD.
    Lundström, Niklas L. P.
    Umeå university.
    Karlsson, Martin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Calleecharan, Yogeshwarsing
    Nässelqvist, Mattias
    Karlberg, Magnus
    Lundin, Urban
    Uppsala University.
    Developments in rotor dynamical modeling of hydropower units2009In: Proceedings of the IUTAM Symposium on Emerging Trends in Rotor Dynamics: held in New Delhi, India, March 23 - March 26, 2009 / [ed] Kshitij Gupta, Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag, 2009Conference paper (Refereed)
  • 15.
    Aidanpää, Jan-Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Shen, Hayley
    Clarkson University, Potsdam, NY.
    Onset of transition for cohesive and viscous granular flows1998In: Journal of engineering mechanics, ISSN 0733-9399, E-ISSN 1943-7889, Vol. 124, no 10, 1073-1079 p.Article in journal (Refereed)
    Abstract [en]

    A theory for determining the onset of rapid flow or termination of quasi-static flow in a cohesive granular material mixed in a viscous interstitial fluid is presented. This theory is based on a one-dimensional model introduced in an earlier paper. Linear stability analysis is used to find the combination of material properties and flow rate for which a quasi-static flow becomes unstable, indicating the onset of rapid flow. This theory yields a quantitative criterion to select appropriate constitutive laws for viscous and cohesive granular material. This criterion is a linear approximation of the theoretical result. While it provides the critical condition for quasi-static flow to terminate, it does not give the transitional constitutive law before a rapid flow is fully developed, for which a second power law dependence on the strain rate applies. Nonetheless, the analysis and modeling effort presented in this work are necessary first steps toward a general quantification of how granular materials, with identical physical composition, can behave in drastically different ways.

  • 16. Alberg, Henrik
    Material modelling for simulation of heat treatment2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Heat treatment of materials is a fundamental metallurgical process. Materials are subjected to heat treatment to relieve internal stresses, reduce brittleness and to improve machinability. The properties of materials can also be altered such as hardness, strength, toughness, and wear resistance to suit particular applications. Nevertheless, heat treatment can generate unwanted stresses and deformations, a fact that has to be taken into consideration when designing or changing the sequence of manufacturing for a given component. One way to decrease cost and reduce time in product development can be to use simulation tools that can reliably predict the final properties and shape of a component caused by the used manufacturing process. A decrease in cost and better knowledge of final properties already in product development can give the company a better market position and competitiveness. The objective of the work presented in this thesis is to develop efficient and reliable methods and models for simulation of heat treatment using the Finite Elements Method. The result of the simulation must be sufficiently accurate and completed within an acceptable time when the manufacturing simulation is to be used in product development. The models would enable us to predict residual stresses, distortion, final shape, and amount material phases after a heat treatment process. The formulation of constitutive equations for elasticity, plasticity, and creep is discussed, along with three unified models, bringing together plasticity/viscoplasticity, and creep into one model. There are many materials models to choose among but material parameters are usually lacking An approach where the same numerical algorithm for the implementation of a constitutive model in the finite element code is also used for material parameter identification is presented. A parameter fitting using a viscoplastic model with nonlinear isotropic hardening is performed. Combined welding and heat treatment simulation is performed on a geometrical complex shaped aerospace component. Efforts to accurately determine the boundary conditions have been made. During the cooling sequence most of the heat transfer is carried out by convective heat transfer. Therefore, a method is developed and a CFD analysis is carried out to obtain this convective heat transfer Moreover, comparisons how the use of different material models affects the response from combined welding and heat treatment on an aerospace component is made. The material models include different effects; rate-independent and viscoplastic models including microstructure calculation and transformation induced plasticity. Different creep models and different ways to apply them has also been investigated.

  • 17. Alberg, Henrik
    Simulation of welding and heat treatment: modelling and validation2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Many aerospace components with complex geometry are fabricated from smaller parts using joining techniques such as welding. Welding and the heat treatment which usually follows, can result in unwanted deformation and stresses. Expensive materials, tight geometrical tolerances and the need to decrease product and manufacturing development time, cost and associated risks have motivated the development of models and methods for the simulation of manufacturing processes. The work presented concerns methodologies and modelling techniques for the simulation of welding and heat treatment of fabricated aircraft-engine components. The aim of the work was to develop modelling practices to enable the use of finite element analysis for the prediction of deformation, residual stresses and material properties such as microstructure during and after welding and heat treatment. Achieving this aim has required investigation of geometrical discretisation, modelling of boundary conditions and material behaviour for these processes. The case study components were made of a martensitic stainless steel, Greek Ascoloy. Phase evolutions models and models for rate-independent, rate-dependent, and creep were used as the material models in the welding and heat treatment simulations. The work also includes discussion of numerical considerations in material modelling. A toolbox for evaluation of constitutive models and to obtain material parameters for the plasticity models was developed. The heat transfer coefficient is an important parameter for describing energy transfer between the component and a gas. Due to the complexity of the gas flow in the heat treatment furnace during cooling, a method using computational fluid dynamics was developed to obtain an approximate distribution of the heat transfer coefficient. Due to the impact that modelling and simulation predictions can have, the creditability of the computational results are of great concern to engineering designers, managers and other affected by decisions based on these predictions. In this work, a validation methodology for welding and post weld heat treatment models was developed. The model used for welding simulations gives results with the accuracy required for predicting deformation and residual stresses at all stages of the product and manufacturing development process. The heat treatment model predicts deformations and residual stresses resulting from stress relief heat treatment of sufficient accuracy to be used in the concept and preliminary stages of product and manufacturing development. The models and methodology have been implemented, tested and are in use at Volvo Aero.

  • 18. Alberg, Henrik
    et al.
    Berglund, Daniel
    Comparison of an axisymmetric and a three-dimensional model for welding and stress relief heat treatment2004In: Materials Processing and Design: Modeling, Simulation and Applications. Proceedings (NUMIFORM 2004 ) / [ed] Somnath Ghosh, Melville, NY: American Institute of Physics (AIP), 2004, Vol. 2, 1230-1235 p.Conference paper (Refereed)
    Abstract [en]

    This work is part of a project dedicated to find accurate and reliable tools for prediction of welding and post weld heat treatment. In other parts of the project, a simulation method for combined welding and heat treatment simulations of the component was developed and different plastic/viscoplastic material models have been compared, these models included effects of phase changes. These simulations were made using an axisymmetric finite element model. The current paper presents welding and heat treatment simulations of the same aerospace component but now using a three-dimensional shell model. The results are compared with the previously used axisymmetric model. The simulations revealed that the two first welds have the greatest influents on a 'key dimension'. From the simulation, it can be concluded that the three-dimensional model give better prediction of the dimension based on measurement performed but not presented here. The simulation presented in this paper is part of an aerospace component called Turbine Exhaust Case which is a fabricated structure made of a martensitic stainless steel.

  • 19. Alberg, Henrik
    et al.
    Berglund, Daniel
    Comparison of plastic, viscoplastic, and creep models when modelling welding and stress relief heat treatment2003In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 192, no 49-50, 5189-5208 p.Article in journal (Refereed)
    Abstract [en]

    A major concern when carrying out welding and heat treatment simulations is to accurately model material behaviour as it varies with temperature and composition. Early in the product development process, a less sophisticated material model may be suitable to compare different concepts where less accuracy in deformation and residual stress is acceptable. At later stages in the product development process, more sophisticated models may be used to obtain more accurate predictions of deformations and residual stresses. This paper presents a comparison of five different material models applied to the simulation of a combined welding and heat treatment process for a fabricated martensitic stainless steel component.

  • 20. Alberg, Henrik
    et al.
    Berglund, Daniel
    Corrigendum to: "Comparison of plastic, viscoplastic, and creep models when modelling welding and stress relief heat treatment"2004In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 193, no 45-47, 5063-5067 p.Article in journal (Other academic)
  • 21.
    Alhalaweh, Amjad
    et al.
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Alzghoul, Ahmad
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Kaialy, Waseem
    Chemistry and Drug Delivery Group, Medway School of Pharmacy, University of Kent.
    Data mining of solubility parameters for computational prediction of drug–excipient miscibility2014In: Drug Development and Industrial Pharmacy, ISSN 0363-9045, E-ISSN 1520-5762, Vol. 40, no 7, 904-909 p.Article in journal (Refereed)
    Abstract [en]

    Computational data mining is of interest in the pharmaceutical arena for the analysis of massive amounts of data and to assist in the management and utilization of the data. In this study, a data mining approach was used to predict the miscibility of a drug and several excipients, using Hansen solubility parameters (HSPs) as the data set. The K-means clustering algorithm was applied to predict the miscibility of indomethacin with a set of more than 30 compounds based on their partial solubility parameters [dispersion forces , polar forces and hydrogen bonding ]. The miscibility of the compounds was determined experimentally, using differential scanning calorimetry (DSC), in a separate study. The results of the K-means algorithm and DSC were compared to evaluate the K-means clustering prediction performance using the HSPs three-dimensional parameters, the two-dimensional parameters such as volume-dependent solubility and hydrogen bonding , and selected single (one-dimensional) parameters. Using HSPs, the prediction of miscibility by the K-means algorithm correlated well with the DSC results, with an overall accuracy of 94%. The prediction accuracy was the same (94%) when the two-dimensional parameters or the hydrogen-bonding (one-dimensional) parameter were used. The hydrogen-bonding parameter was thus a determining factor in predicting miscibility in such set of compounds, whereas the dispersive and polar parameters had only a weak correlation. The results show that data mining approach is a valuable tool for predicting drug–excipient miscibility because it is easy to use, is time and cost-effective, and is material sparing.

  • 22.
    Almefelt, Lars
    et al.
    Chalmers University of Technology.
    Brännström, Oskar
    The network as an asset: reflections on an industrial case2004Report (Other academic)
  • 23.
    Alonso-Rasgado, Teresa
    et al.
    University of Manchester.
    Thompson, G.
    University of Manchester.
    Elfström, Bengt-Olof
    The design of functional (total care) products2004In: Journal of engineering design (Print), ISSN 0954-4828, E-ISSN 1466-1837, Vol. 15, no 6, 515-540 p.Article in journal (Refereed)
    Abstract [en]

    Total care products (functional products) are integrated systems comprising hardware and support services. The functional product supplier provides all the support systems that are required to keep the hardware operable. The support systems are often referred to as 'services'. The success of total care products depends upon both hardware and services. Well established methods exist for the design of hardware. In comparison, design processes and methods for services are not so well developed. This paper is concerned with the definition and design of functional products, in particular design of services in the context of total care products. Literature from the service sector is reviewed extensively to identify the principal components of service design. The information required for the execution of each component of the process, and outputs of each component, are considered with respect to the design of total care products. Of particular interest is the customer-supplier relationship throughout the design process. The design of a total care product may involve the creation of a new service system or there may be an existing system that may be adapted or developed. Similarly, hardware may be mature or be a completely new product. There are therefore number of permutations of novelty and maturity in the hardware and service components of a new total care product. The design processes and methods employed must take into account the required degree of novelty in each component. Typically a customer will be given a guarantee of a certain level of availability of the total care product. This brings into sharp focus the reliability and maintainability of the total system. Further research directions in total care product design are identified especially related to functional reliability

  • 24.
    Alsyouf, Imad
    et al.
    Växjö university.
    Alzghoul, Ahmad
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Soft computing applications in wind power systems: a review and analysis2009Conference paper (Other academic)
    Abstract [en]

    This paper reviews, analyses, discusses and summarises the recent research and development and trends in the applications of soft computing in the field of wind power systems. We show the usage and the influence of soft computing on the different aspects of wind power systems especially in the field of operation and maintenance. This work provides the state of the art in this area which will be a good guidance for future research work. The main results achieved from the study show that the soft computing techniques are adequate for solving the different challenges at the different phases of the life cycle processes of wind power systems. Using the various soft computing techniques with wind power systems proved to be useful for the wind energy business. Using these tools contribute by improving the robustness of the decisions at different phases of the system's life cycle. Soft computing can enhance the efficiency and effectiveness of the operation and maintenance of offshore wind power systems through improving the availability levels. Thus, providing secure, sustainable and competitive energy supply for the future.

  • 25.
    Alzghoul, Ahmad
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Improving availability of industrial products through data stream mining2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Products of high quality are of great interest for industrial companies. The quality of a product can be considered in terms of production cost, operating cost, safety and product availability, for example. Product availability is a function of maintainability and reliability. Monitoring prevents unplanned stops, thus increasing product availability by decreasing needed maintenance. Through monitoring, failures can be detected and/or avoided. Detecting failures eliminates extra costs such as costs associated with machinery damage and dissatisfied customers, and time is saved since stops can be scheduled, instead of having unplanned stops. Product monitoring can be done through searching the data generated from sensors installed on products.Nowadays, the data can be collected at high rates as part of a data stream. Therefore, data stream management systems (DSMS) and data stream mining (DSM) are being used to control, manage and search the data stream. This work investigated how the availability of industrial products can be increased through the use of DSM and DSMS technologies.A review of the data stream mining algorithms and their applications in monitoring was conducted. Based on the review, a new data stream classification method, i.e. Grid-based classifier was proposed, tested and validated. Also, a fault detection system based on DSM and DSMS technologies was proposed. The proposed fault detection system was tested using data collected from Hägglunds Drives AB (HDAB) hydraulic motors. Thereafter, a data stream predictor was integrated into the proposed fault detection system to detect failures earlier, thus gaining more time for response actions. The modified fault detection system was tested and showed good performance. The results showed that the proposed fault detection system, which is based on DSM and DSMS technologies, achieved good performance (with classification accuracy around 95%) in detecting failures on time. Detecting failures on time prevents unplanned stops and may improve the maintainability of the industrial systems and, thus, their availability.

  • 26.
    Alzghoul, Ahmad
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Mining data streams to increase ‎industrial product availability2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Improving product quality is always of industrial interest. Product availability, a function of product maintainability and reliability, is an example of a measurement that can be used to evaluate product quality. Product availability and cost are two units which are especially important to manage in the context of the manufacturing industry, especially where industry is interested in selling or buying offers with increased service content. Industry in general uses different strategies for increasing equipment availability; these include: corrective (immediate or delayed) and preventive strategies. Preventive strategies may be further subdivided into scheduled and predictive (condition-based) maintenance strategies. In turn, predictive maintenance may also be subdivided into scheduled inspection and continuously monitored. The predictive approach can be achieved by early fault detection. Fault detection and diagnosis methods can be classified into three categories: data-driven, analytically based, and knowledge-based methods. In this thesis, the focus is mainly on fault detection and on data-driven models.Furthermore, industry is generating an ever-increasing amount of data, which may eventually become impractical to store and search, and when the data rate is increasing, eventually impossible to store. The ever-increasing amount of data has prompted both industry and researchers to find systems and tools which can control the data on the fly, as close to real-time as possible, without the need to store the data itself. Approaches and tools such as Data Stream Mining (DSM) and Data Stream Management Systems (DSMS) become important. For the work reported in this thesis, DSMS and DSM have been used to control, manage and search data streams, with the purpose of supporting increased availability of industrial products.Bosch Rexroth Mellansel AB (formerly Hägglunds Drives AB) has been the industrial partner company during the course of the work reported in this thesis. Related data collection concerning the functionality of the BRMAB hydraulic system has been performed in collaboration with other researchers in Computer Aided Design at Luleå University of Technology.The research reported in this thesis started with a review of data stream mining algorithms and their applications in monitoring. Based on the review, a data stream classification method, i.e. Grid-based classifier, was proposed, tested and validated (Paper A). Also, a fault detection system based on DSM and DSMS was proposed and tested, as reported in Paper A. Thereafter, a data stream predictor was integrated into the proposed fault detection system to detect failures earlier, thus demonstrating how data stream prediction can be used to gain more time for proactive response actions by industry (Paper B). Further development included an automatic update method which allows the proposed fault detection system to be able to overcome the problem of concept drift (Paper E). The proposed and modified fault detection systems were tested and verified using data collected in collaboration with Bosch Rexroth Mellansel AB (BRMAB). The requirements for the proposed fault detection system and how it can be used in product development and design of the support system were also discussed (Paper C). In addition, the performance of a knowledge-based method and a data- driven method for detecting failures in high-volume data streams from industrial equipment have been compared (Paper D). It was found that both methods were able to detect all faults without any false alert. Finally, the possible implications of using cloud services for supporting industrial availability are discussed in Paper F. Further discussions regarding the research process and the relations between the appended papers can be found in Chapter 2, Figure 4 and in Chapter 5, Figure 21.The results showed that the proposed and modified fault detection systems achieved good performance in detecting and predicting failures on time (see Paper A and Paper B). In Paper C, it is shown how data stream management systems may be used to increase product availability awareness. Also, both the data-driven method and the knowledgebased method were suitable for searching data streams (see Paper D). Paper E shows how the challenge of concept drift, i.e. the situation in which the statistical properties of a data stream change over time, was turned to an advantage, since the authors were able to develop a method to automatically update the safe operation limits of the one-class data-driven models.In general, detecting faults and failures on time prevents unplanned stops and may improve both maintainability and reliability of industrial systems and, thus, their availability (since availability is a function of maintainability and reliability). By the results, this thesis demonstrates how DSM and DSMS technologies can be used to increase product availability and thereby increase product quality in terms of availability.

  • 27. Alzghoul, Ahmad
    et al.
    Backe, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Löfstrand, Magnus
    Uppsala universitet.
    Byström, Arne
    Uppsala University, Department of Information Technology, Division of Computing Science.
    Liljedahl, Bengt
    Bosch Rexroth Mellansel AB.
    Comparing a knowledge-based and a data-driven method in querying data streams for system fault detection: A hydraulic drive system application2014In: Computers in industry (Print), ISSN 0166-3615, E-ISSN 1872-6194, Vol. 65, no 8, 1126-1135 p.Article in journal (Refereed)
    Abstract [en]

    The field of fault detection and diagnosis has been the subject of considerable interest in industry. Fault detection may increase the availability of products, thereby improving their quality. Fault detection and diagnosis methods can be classified in three categories: data-driven, analytically based, and knowledge-based methods. In this work, we investigated the ability and the performance of applying two fault detection methods to query data streams produced from hydraulic drive systems. A knowledge-based method was compared to a data-driven method. A fault detection system based on a data stream management system (DSMS) was developed in order to test and compare the two methods using data from real hydraulic drive systems. The knowledge-based method was based on causal models (fault trees), and principal component analysis (PCA) was used to build the data-driven model. The performance of the methods in terms of accuracy and speed, was examined using normal and physically simulated fault data. The results show that both methods generate queries fast enough to query the data streams online, with a similar level of fault detection accuracy. The industrial applications of both methods include monitoring of individual industrial mechanical systems as well as fleets of such systems. One can conclude that both methods may be used to increase industrial system availability

  • 28.
    Alzghoul, Ahmad
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Löfstrand, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Increasing availability of industrial systems through data stream mining2011In: Computers & industrial engineering, ISSN 0360-8352, E-ISSN 1879-0550, Vol. 60, no 2, 195-205 p.Article in journal (Refereed)
    Abstract [en]

    Improving industrial product reliability, maintainability and thus availability is a challenging task for many industrial companies. In industry, there is a growing need to process data in real time, since the generated data volume exceeds the available storage capacity. This paper consists of a review of data stream mining and data stream management systems aimed at improving product availability. Further, a newly developed and validated grid-based classifier method is presented and compared to one-class support vector machine (OCSVM) and a polygon-based classifier.The results showed that, using 10% of the total data set to train the algorithm, all three methods achieved good (>95% correct) overall classification accuracy. In addition, all three methods can be applied on both offline and online data.The speed of the resultant function from the OCSVM method was, not surprisingly, higher than the other two methods, but in industrial applications the OCSVMs' comparatively long time needed for training is a possible challenge. The main advantage of the grid-based classification method is that it allows for calculation of the probability (%) that a data point belongs to a specific class, and the method can be easily modified to be incremental.The high classification accuracy can be utilized to detect the failures at an early stage, thereby increasing the reliability and thus the availability of the product (since availability is a function of maintainability and reliability). In addition, the consequences of equipment failures in terms of time and cost can be mitigated.

  • 29.
    Alzghoul, Ahmad
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Löfstrand, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Backe, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Data stream forecasting for system fault prediction2012In: Computers & industrial engineering, ISSN 0360-8352, E-ISSN 1879-0550, Vol. 62, no 4, 972-978 p.Article in journal (Refereed)
    Abstract [en]

    Competition among today’s industrial companies is very high. Therefore, system availability plays an important role and is a critical point for most companies. Detecting failures at an early stage or foreseeing them before they occur is crucial for machinery availability. Data analysis is the most common method for machine health condition monitoring. In this paper we propose a fault-detection system based on data stream prediction, data stream mining, and data stream management system (DSMS). Companies that are able to predict and avoid the occurrence of failures have an advantage over their competitors. The literature has shown that data prediction can also reduce the consumption of communication resources in distributed data stream processing.In this paper different data-stream-based linear regression prediction methods have been tested and compared within a newly developed fault detection system. Based on the fault detection system, three DSM algorithms outputs are compared to each other and to real data. The three applied and evaluated data stream mining algorithms were: Grid-based classifier, polygon-based method, and one-class support vector machines (OCSVM).The results showed that the linear regression method generally achieved good performance in predicting short-term data. (The best achieved performance was with a Mean Absolute Error (MAE) around 0.4, representing prediction accuracy of 87.5%). Not surprisingly, results showed that the classification accuracy was reduced when using the predicted data. However, the fault-detection system was able to attain an acceptable performance of around 89% classification accuracy when using predicted data.

  • 30.
    Alzghoul, Ahmad
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Löfstrand, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Karlsson, Lennart
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Karlberg, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Data stream mining for increased functional product availability awareness2011In: Functional Thinking for Value Creation: Proceedings of the 3rd CIRP International Conference on Industrial Product Service Systems, Technische Universität Braunschweig, Braunschweig, Germany, May 5th - 6th, 2011 / [ed] Jürgen Hesselbach; Christoph Herrmann, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2011, 237-241 p.Conference paper (Refereed)
    Abstract [en]

    Functional Products (FP) and Product Service Systems (PSS) may be seen as integrated systems comprising hardware and support services. For such offerings, availability is key. Little research has been done on integrating Data Stream Management Systems (DSMS) for monitoring (parts of) a FP to improve system availability. This paper introduces an approach for how data stream mining may be applied to monitor hardware being part of a Functional Product. The result shows that DSMS have the potential to significantly support continuous availability awareness of industrial systems, especially important when the supplier is to supply a function with certain availability.

  • 31.
    Ananías, Rubén A.
    et al.
    Department of Wood Engineering, Faculty of Engineering, University of Bío-Bío, Concepcion.
    Mena, Marcelo
    Department of Wood Engineering, Faculty of Engineering, University of Bío-Bío, Concepcion.
    Elustondo, Diego
    Díaz-vaz, Juan Eduardo
    ITPF, Faculty of Forest Sciences, Austral University.
    Valenzuela, Luis
    Faculty of Forest Sciences, University of Concepción.
    Salinas, Carlos T S
    Department of Mechanical Engineering, Faculty of Engineering, University of Bío-Bío, Concepción.
    Testing New In-Kiln Meter for Monitoring Lumber Moisture Content during Drying2013In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 31, no 3, 277-281 p.Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to test a new in-kiln sensor for monitoring lumber moisture content during industrial drying. The theoretical foundation of the technology was already known, because it is based on electrical conductivity, but the mechanism of implementation was new and required validation. For this reason, the technology was compared with two other widely used methods for assessing lumber moisture content, namely, the oven-drying and electrical capacitance methods. The tests were performed in a 120-m3 industrial kiln operated by a sawmill in the eighth region of Chile, and the results showed that the average moisture content at the end of drying was satisfactorily determined by the new in-line sensor. As predicted by theory, the sensor was not able to accurately measure moisture content above 25%, but it was still able to provide the equivalent of a drying curve for monitoring of the drying process

  • 32.
    Ananías, Rubén A.
    et al.
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Perez, Patricio
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Salinas, Carlos
    Department of Mechanical Engineering, University of Bío-Bío, Concepción.
    Elustondo, Diego
    Drying Schedules for Canelo Wood2013In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 31, no 3, 282-285 p.Article in journal (Refereed)
    Abstract [en]

    Canelo wood is a highly valued native species in Chile that shows delicate marbling patterns with a pinkish soft silver luster. Due to its decorative qualities, canelo wood is dried for the manufacture of furniture and musical instruments. However, canelo wood lacks vessels cells that typically transport the water in hardwoods. Per its drying behavior, canelo wood is considered a transition species between hardwoods and softwoods. Therefore, this article reports drying schedules that were developed for drying 25-mm and 50-mm canelo lumber. In addition, this article reports experimental overall mass transfer coefficients, so that drying times for each of the drying stages can be easily estimated

  • 33.
    Ananías, Rubén A.
    et al.
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Ulloa, J.
    Aserraderos Arauco S.A., Arauco.
    Elustondo, Diego
    Salinas, Carlos T S
    Mechanical Engineering Department, University of Bío-Bío, Concepción.
    Rebolledo, Pamela
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Fuentes, C.
    Aserraderos Arauco S.A., Arauco.
    Energy Consumption in Industrial Drying of Radiata Pine2012In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 30, no 7, 774-779 p.Article in journal (Refereed)
    Abstract [en]

    This article reports the results of an exploratory study designed to reduce heat and electricity consumption in industrial drying of radiata pine. The experiments were performed with slight modifications of the standard drying schedules used by the sawmill to dry radiata pine in 100-m 3 industrial kilns. The heat and electricity consumption were determined with data collected during the drying runs and calculations based on mathematical models. The results showed that depending on the case, heat and power consumption were respectively reduced by up to 14 and 35%.

  • 34.
    Ananías, Rubén A.
    et al.
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Venegas, Rodrigo
    CMPC Maderas S.A., 5 camino a Laja, Cabrero, Bucalemu.
    Salvo, Linette
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Elustondo, Diego
    Kiln schedule certification for industrial drying of radiata pine2013In: Wood and Fiber Science, ISSN 0735-6161, Vol. 45, no 1, 98-104 p.Article in journal (Refereed)
    Abstract [en]

    This is a summary of a study carried out in Chile to certify industrial kiln drying of radiata pine to comply with the international phytosanitary standard ISPM 15. The drying tests were performed in 100-m3 industrial kilns located at four different sawmills of the VIII region in Chile. The objective was to develop a standard protocol to certify industrial drying of radiata pine depending on the drying schedule and wood thickness. In part, the results were used to develop a multiple regression equation that permits sawmills to select their drying schedules in such a way that the lumber can be officially stamped as both kiln-dried and heat-treated for international trade

  • 35. Andersson, Börje
    et al.
    Karlsson, Lennart
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Thermal stresses in large butt-welded plates1981In: Journal of thermal stresses, ISSN 0149-5739, E-ISSN 1521-074X, Vol. 4, no 3-4, 491-500 p.Article in journal (Refereed)
    Abstract [en]

    In shipyard panel-production lines several rectangular plates ae butt welded to form large panels. One problem is the tendency of hot cracking in the end portion of the butt weld. In this paper transient temperature fields and stress fields in butt-welded plates are calculated using the finite-element method. The calculations are performed for different welding speeds, for different heat inputs, and for one-sided and two-sided welding.

  • 36.
    Andersson, Karl
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Lundahl, Carl-Gustav
    Lundmark, Martin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Nordvik, Enar
    Pantze, Anna
    Förslag till handlingsplan för utveckling av LTU Skellefteå: Att synas med stolthet2008Report (Other academic)
  • 37. Andersson, Mikael
    Drivhusmodellen i teori och praktik: ett verksamhetsintegrerat forsknings- och utvecklingsarbete för integration av utbildning, forskning och samverkan vid Luleå tekniska universitet2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns the development of a model for integration of education, research and cooperation intended for university use. The thesis builds on a research and development work integrated in the daily educational activity of the university. The model; the Green-house model combines experience-based learning with theory-based learning dialectically. The model and it's correspondent activities and practice is developed at the Luleå Technical University inside the four green-houses started in the Arena for Innovative Technology and Business. The purpose of the green-house is to introduce a cross-functional knowledge- building which is characterised by multidisciplinarity, the participation of different professions, the cooperation with actors from the surrounding society, that all actors are active and a cooperation that is based on equality between actors. Students and researchers participate in a green-house activity through a role/function related to a profession. In this activity situations occur that generates the need of action. If this need can be satisfied through re- creational actions these can be made the subject of reflection. If not the situation has generated a problem. In this case the acting unit, a person or a group must use their imagination (and creativity) to create innovative action. The starting point of the action can be found in the following areas of knowledge: the activity, the situation (needs, related problems and phenomena) and the actors function (role and/or group). The knowledge can be viewed out of the following aspects of knowledge: declarative and familiar knowledge, judgment and ability. These aspects can be discerned in connection with all these areas of knowledge. Put together this describes the learning process in the Green-house model. The long-term aim of the integration of experience-based learning with theory-based learning and the applied learning-process according to the green-house model is to enhance the possibility for development-oriented learning (which is closely related to Engeströms's Learning by expanding) in (later) working life. Development-oriented learning is defined as the individuals (or groups) own ability to interpret action, situation and his/her own function in a way that can go beyond the limits of the conditions at hand. Development- oriented learning is in its ideal form characterised by independent development of goal/task, choice of method and evaluation of outcomes. A activity-integrated frame of interpretation is developed in this thesis. It is characterised by the following critical aspects concerning model and practice: activity and practice, informal model (goal documents etc.), prescriptive model (an ideal type controlled by the researcher/developer), activity-related theory (scientific theories that can be more or less directly related to the activity) and other theories. In this work the foundation of an activity-integrated r&d program is laid. The knowledge of the model and activity/practice is developed by the participation in the following roles: operator, developer and researcher. Data has been collected inspired ethnographic method and the reflection on data has a connection to hermeneutic method. The activity-related theory, together with the activity-related frame of interpretation has been applied to the analysis of model and activity/practice. As a part of the analysis recommendations have been made to activity/practice. The recommendations and the reactions on those is an important part of the activity-integrated method. The learning process follows the characteristics of the learning process of the green-house model. The activity-integrated r&d model can be seen as an alternative to action research or other forms of research close to practice. Words in Italic represent concepts of central importance to this thesis and are defined in its text.

  • 38. Andersson, Mikael
    Hur kan akademi organisera samverkan för tillväxt?: Deliberativ Organiserad Samverkan, DOS, en ny styrningsmodell2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Within research and education policies of later decades, a clear trend can be seen in expanded attempts to stimulate growth-concentrated cooperation between government, academia and industry. With economic financing, channelled to academia through different kinds of research and development councils, follows a responsibility to operationally organize the actors' cooperation. This task is rather complex. The cooperative process is expected to be equal, provided that the participating actors have different professional identities, belong to different organizations, have different values and ideas of norms, and satisfy different interests. With present research and education policies, follows the idea of academia acting as a potential growth engine that should be directly used to develop society's innovation system, production system and markets. In connection with this, discussions regarding academic capitalism, commercialisation of research results, incubation processes, etc., are being conducted. The traditional role of academia as a research university has also been complemented by the roles of organizer for growth-concentrated cooperation and entrepreneur.Pursuing independent research, being an organizer for similar cooperation, and satisfying their personal interests all at the same time is contradictory. A way for academia to prevent their own interests from getting out of hand during cooperation is to avoid all forms of external management, and instead focus on stimulating the participating actors to evaluate, develop and manage their cooperation themselves. Conventional education, research and project models are developed for purposes other than this. Desipte this, their usage with the cooperative task is rather widespred. For cooperative actors to understand and handle their activities in an aware, collective and flexible manner, they need to use some form of management model that allows for communicative coordination, evaluation and development of organizational action. As an alternative to those conventional models, a new management model has been developed in this thesis, called Deliberative Organized Cooperation, DOC. The model is developed with inspiration from deliberative theory. Simply put, the actors' cooperation is expected to occur through repeated dialectic movements between deliberative phases (management process), where actors produce valid action alternatives and legitimate interpersonal and systematic relations, and systematic phases (operational activities), where the actors transform the gained validity and legitimacy in systematic action and resulting factuality. While the deliberative phase corresponds to evaluation and development orientated logic with open rationality conditions, the systematic phase corresponds to production orientated logic with closed rationality conditions.The primary empirical results of the thesis are collected from activities that have been driven or are driven within or closely connected to two competence centres located at Luleå Univeristy of Technology. The first competence centre, the Polhem Laboratory, is presently being phased out and replaced by the Faste Laboratory. Both operations can be described with help from the Triple Helix model. Simply stated, the government contributes with direct economic funding for R&D as well as the overall rules of the game regarding the actors' cooperation, the industry with supplementary economic funding and direct turnover of the developed knowledge. The economic funding also goes to academia with an organizing of the cooperation process, knowledge development and commercialisation of interesting spin-off knowledge. An essential element in the operations of the Polhem and Faste Laboratories constitutes the so-called Sirius Project, an industrially oriented product development project conducted by fourth year students in the mechanical engineering program. This project is primarily conducted in cooperation between academia and large companies. Closely connected to this activity, Arena innovative technology and business, organizes multi-science undergraduate studies. An important part of this education is to cooperate in so-called greenhouse projects. Here, students from various study years and majors, meets researchers/teachers from different subject fields, and actors from different companies and development firms. The over-all aim of the projects is to stimulate entrepreneurship and starting of new robust companies. DOC comprises an attempt to solve management problem identified in connection to the above activities.The activities have been investigated through participating observations. Individual events have been worked upon and weaved together into a cohesive and anonymous scenario that is told by giving voices to a variety of the participating actors. In the theoretically oriented chapter of the thesis, events are problematised from the scenario through analytical and pragmatic reflections. With help of these reflections, the DOC model is successively built up.

  • 39. Andersson, Mikael
    et al.
    Jonsson, Mikael
    Söderlund, Anders
    Luleå University of Technology, Department of Arts, Communication and Education, Education, Language, and Teaching.
    The Greenhouse learning concept: a new pedagogical approach2002In: The Renaissance engineer of tomorrow: proceedings of the 30th SEFI annual conference, 2002Conference paper (Refereed)
  • 40.
    Andreasson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Validation of Friction Estimating System2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 41. Angantyr, Anders
    Constrained optimization of rotor-bearing systems by evolutionary algorithms2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the design of mechanical components and systems, nature has often been the source of inspiration. It is easy to point out solutions in nature that are optimal in some sense. One example is the structure of the surface of a shark's skin. This is designed by nature to minimize the resistance when the shark swims in the water. Another example is the shape of an egg shell. This is an optimal load carrying structure that often is found in engineering design applications. An even more fascinating question is how nature has found these optimal solutions? The answer to this question is evolution. Instead of just analyzing and copy optimal structures invented by nature it seems reasonable to mimic the process how nature has come up with these solutions. Research on how these ideas can be interpreted and used in engineering design started in the early seventies and has now become a large field known as Evolutionary Algorithms (EAs). During the past decade these methods have emerged as potent tools for engineering design optimization. Some of these methods are especially suited for problems that involve multiple objectives such as almost all real engineering design problems. Just until recently, these methods have seldom been used in the area of rotordynamical design. This thesis deals with the question how these methods can be adapted and applied in order to improve the design and design process of large rotor-bearing system. A hypothesis for this work is that EAs are suitable to use in the late design process of these systems. The aim of this work is to evaluate this hypothesis by studying real applications found in industry. This thesis comprises an introductory part and four appended papers. The introductory part is divided into three different sections. In the first section the concept of engineering design optimization is introduced. In the second part Genetic Algorithms (GAs) is presented. Finally, the analysis and design of rotor-bearing systems is discussed in more general terms. The purpose with the introductory part is to introduce and prepare the reader to the concepts discussed in the papers. The introductory part may serve as a survey or start point for newcomers interested in these areas. This overview is also the most important contribution of the introductory part of the thesis. The appended papers cover selected problems of constrained rotor- bearing system optimizations. In the papers A the multiobjective optimization of a generator is presented and discussed. Paper B introduces a constraint handling technique based on concepts found in multiobjective GAs. In paper C and D this techniques is used for two different rotor-bearing system optimization problems where the actual geometry parameters of the bearings are used as design variables.

  • 42. Angantyr, Anders
    Rotordynamic optimization of large turbo systems using genetic algorithms2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In engineering design, nature has often been the source of inspiration. It is easy to point out solutions in nature that are optimal in some sense. One example is the roughness of the surface of a shark's skin. This is designed by nature to minimize the resistance when the shark swims in the water. Another example is the shape of an egg shell. This is an optimal load carrying structure which often is found in engineering design applications. An even more fascinating question is how nature has found these optimal solutions? The answer to this question is evolution. Instead of just analyzing and copying optimal structures invented by nature it seems reasonable to mimic the process how nature has came up with these solutions. Research on how these ideas can be interpreted and used in engineering design started in the early seventies and has now become a large field known as Evolutionary Algorithms (EAs). During the past decade these methods have emerged as potent tools for engineering design optimization. Some of these methods are especially suited for problems which involve multiple objectives such as almost all real engineering design problems. Just until recently, these methods have seldom been used in the area of rotordynamical design. This thesis deals with the question how these methods can be adapted and applied in order to improve the design and design process of large rotor-bearing system. A hypothesis for this work is that EAs are suitable to use in the late design process of these systems. The aim of this work is to evaluate this hypothesis by studying real applications found in industry. This thesis comprises an introductory part and five appended papers. The introductory part is divided into four different chapters. In the second chapter the concept of engineering design optimization is introduced. In the third chapter Genetic Algorithms (GAs) is presented. Finally, the analysis and design of rotor-bearing systems are introduced and discussed. The purpose with the introductory part is to introduce and prepare the reader to the concepts presented in the papers. The introductory part may serve as a start point for newcomers interested in these areas. The appended papers deal with different rotor-bearing system optimization problems and how these can be formulated and solved with GAs. Paper A introduces a constraint handling technique based on concepts found in multiobjective GAs. In Paper B the multiobjective optimization of a generator is presented and discussed. In Paper C and Paper D the constraint handling technique introduced in Paper A is used for two different rotor- bearing system where the actual bearing geometry parameters are used as design variables in the optimizations. In Paper E the feasibility of site balancing rewinded turbo generators is investigated by the use of a multiobjective GA.

  • 43. Angantyr, Anders
    et al.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    A pareto-based genetic algorithm search approach to handle damped natural frequency constraints in turbo Generator rotor system design2004In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 126, no 3, 619-625 p.Article in journal (Refereed)
    Abstract [en]

    The detailed design of a turbo generator rotor system is highly constrained by feasible regions for the damped natural frequencies of the system. A major problem for the designer is to find a solution that fulfills the design criterion for the damped natural frequencies. The bearings and some geometrical variables of the rotor are used as the primary design variables in order to achieve a feasible design. This paper presents an alternative approach to search for feasible designs. The design problem is formulated as an optimization problem and a genetic algorithm (GA) is used to search for feasible designs. Then, the problem is extended to include another objective (i.e., multiobjective optimization) to show the potential of using the optimization formulation and a Pareto-based GA in this rotordynamic application. The results show that the presented approach is promising as an engineering design tool

  • 44. Angantyr, Anders
    et al.
    Aidanpää, Jan-Olov
    Constrained optimization of gas turbine tilting pad bearing designs2006In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 128, no 4, 873-878 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents the constrained optimization of the tilting pad bearing design on a gas turbine rotor system. A real coded genetic algorithm with a robust constraint handling technique is used as the optimization method. The objective is to develop a formulation of the optimization problem for the late bearing design of a complex rotor-bearing system. Furthermore, the usefulness of the search method is evaluated on a difficult problem. The effects considered are power loss and limiting temperatures in the bearings as well as the dynamics at the system level, i.e., stability and unbalance responses. The design variables are the bearing widths and radial clearances. A nominal design is the basis for comparison of the optimal solution found. An initial numerical experiment shows that finding a solution that fulfills all the constraints for the system design is likely impossible. Still, the optimization shows the possibility of finding a solution resulting in a reduced power loss while not violating any of the constraints more than the nominal design. Furthermore, the result also shows that the used search method and constraint handling technique works on this difficult problem.

  • 45. Angantyr, Anders
    et al.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Optimization of a rotor-bearing system with an evolutionary algorithm2004In: 10th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery: ISROMAC-2004 / [ed] Dieter Bohn, Aachen: Inst. of steam and gas turbines, RWTH , 2004Conference paper (Refereed)
  • 46. Angantyr, Anders
    et al.
    Andersson, Johan
    Linköping University.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Constrained optimization based on a multiobjective evolutionary algorithm2003In: The 2003 congress on evolutionary computation: CEC 2003, Piscataway, NJ: IEEE Communications Society, 2003, 1560-1567 p.Conference paper (Refereed)
    Abstract [en]

    A criticism of Evolutionary Algorithms (EAs) might be the lack of efficient and robust generic might be the lack of officient and robust generic methods to handle constraints. The most widespread approach for constrained search problems is to use penalty methods. EAs have received increased interest during the last decade due to the ease of handling multiple objectives., A constrained Optimization problem or an unconstrained multiobjective problem may in principle be two different ways to pose the same underlying I problem. In this paper an alternative approach for the constrained optimization problem is presented. The method is a variant of a multiobjective real coded Genetic Algorithm (CA) inspired by the penalty approach. It is evaluated on six different constrained single objective problems found in the literature. The results show that the proposed method performs well in terms of efficiency, and that it is rohust for a majority of the test problems.

  • 47.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Microwave drying of hardwood: potentials for moisture flux1993Licentiate thesis, monograph (Other academic)
  • 48. Arfvidsson, J.
    et al.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wiberg, P.
    Luleå tekniska universitet.
    The development of a moisure sorption model to predict moisture within solid wood based on non-destructive moisture gradient measurements using CT-scanning and digital ...1997In: International Conference on Wood-Water Relations, 16 - 17 June 1997, Copenhagen, Denmark: [COST Action E8, Mechanical Performance of Wood and Wood Products] / [ed] Preben Hoffmeyer, Copenhagen: Technical University of Denmark , 1997Conference paper (Refereed)
  • 49.
    Asplund, Christer
    et al.
    Luleå tekniska universitet.
    Karlsson, Lennart
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    MacPherson strut wheel suspension dynamics1989Report (Other academic)
  • 50.
    Atashipour, Seyed Rasoul
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A simple closed-form approximation for shear buckling of long narrow laminated generally orthotropic plates2016In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243Article in journal (Refereed)
1234567 1 - 50 of 1381
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