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  • 301.
    Montibon, Elson
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Modification of Paper into Conductive Substrate for Electronic Functions: Deposition, Characterization and Demonstration2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The thesis investigates the modification of paper into an ion- and electron-conductive material, and as a renewable material for electronic device. The study stretches from investigating the interaction between the cellulosic materials and the conducting polymer to demonstrating the performance of the conductive paper by printing the electronic structure on the surface of the conductive paper. Conducting materials such as conducting polymer, ionic liquids, and multi-wall carbon nanotubes were deposited into the fiber networks.

    In order to investigate the interaction between the conducting polymer and cellulosic material, the adsorption of the conducting polymer poly(3,4-ethylenedioxythiophene): poly(4-styrene sulfonate) (PEDOT:PSS) onto microcrystalline cellulose (MCC) was performed. Electroconductive papers were produced via dip coating and rod coating, and characterized. The Scanning Electron Microscopy (SEM) / Energy Dispersive Spectroscopy (EDS) images showed that the conducting polymer was deposited in the fiber and in fiber-fiber contact areas. The X-ray Photoelectron Spectroscopy (XPS) analysis of dip-coated paper samples showed PEDOT enrichment on the surface. The effects of fiber beating and paper formation, addition of organic solvents and pigments (TiO2, MWCNT), and calendering were investigated. Ionic paper was produced by depositing an ionic liquid into the commercial base paper. The dependence to temperature and relative humidity of the ionic conductivity was also investigated. In order to reduce the roughness and improve its printability, the ionic paper was surface-sized using different coating rods.  The bulk resistance increased with increasing surface sizing. The electrochemical performance of the ionic paper was confirmed by printing PEDOT:PSS on the surface. There was change in color of the polymer when a voltage was applied. It was demonstrated that the ionic paper is a good ionic conductor that can be used as component for a more compact electronic device construction.

    Conductive paper has a great potential to be a flexible substrate on which an electronic structure can be constructed. The conduction process in the modified paper is due to the density of charge carriers (ions and electrons), and their short range mobility in the material. The charge carrying is believed to be heterogeneous, involving many charged species as the paper material is chemically heterogeneous.

  • 302.
    Montibon, Elson
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Preparation of Electroconductive Paper by Deposition of Conducting Polymer2009Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The thesis describes an investigation into the interaction between the conducting polymer and cellulosic materials, and the preparation of electroconductive paper. The adsorption behavior of the conducting polymer onto cellulosic materials was characterized. Poly(3,4-ethylenedioxythiophene) doped with poly(4-styrene sulfonate) (PEDOT:PSS) was used as conducting polymer because of its attractive properties in terms of conductivity, water solubility, and environmental stability. The model substrate used for adsorption was microcrystalline cellulose (MCC). Various pH levels and salt concentrations were explored to completely understand the adsorption behavior of PEDOT:PSS. The variation in surface charge characteristics when the pH and salt concentration were changed was monitored by polyelectrolyte titration and zeta potential measurement. The adsorption isotherm showed a broad molecular distribution of the conducting polymer and considerable interaction between the polymer and MCC. As the pH of the solution was increased, the adsorbed amount decreased. With varying salt concentrations, the adsorption passed through a maximum. The extent of deposition of PEDOT:PSS on the surface of cellulosic fibers was investigated using X-ray Photoelectron Spectroscopy (XPS) with a commercial base paper as substrate. XPS analysis of dip-coated paper samples showed PEDOT enrichment on the surface. The degree of washing the dip-coated paper with acidic water did not significantly affect the PEDOT enrichment on the surface.

     

    A base paper was coated with PEDOT:PSS blends to produce electroconductive papers. The bulk conductivities (σdc) of the coated papers were measured using a four-probe technique and impedance spectroscopy. One-side and two-side coating gave comparable conductivity levels. Various organic solvents added to the PEDOT:PSS dispersion at different concentrations showed various effects on the bulk conductivity of the coated paper. Blends containing sorbitol and isopropanol did not enhance the bulk conductivity of the coated paper, and at high concentrations these organic solvents lowered the conductivity. Paper samples coated with a PEDOT:PSS blend containing N-methylpyrrolidinone (NMP) and dimethyl sulfoxide (DMSO) exhibited a higher conductivity than when coated with pure PEDOT:PSS, due to conformational changes and their plasticizing effect. The effect of calendering was investigated and only the sample subjected to 174 kN/m line load after coating showed significant conductivity enhancement. The addition of TiO2 pigment lowered the bulk conductivity of the paper. Contact angle measurements were made to monitor the effect of coating the paper with PEDOT:PSS blends on the hydrophilicity of the paper samples. The amount of PEDOT:PSS deposited in the fiber network was determined using total sulfur analysis. Thus, this study makes use of conventional paper surface treatment as method for achieving bulk conductivity of paper in the semi-conductor range without significantly decreasing the paper strength.

  • 303.
    Muntean, Adrian
    Eindhoven University of Technology.
    Continuum Modeling: An Approach Through Practical Examples2015Bok (Annet vitenskapelig)
  • 304.
    Muntean, Adrian
    et al.
    Technische Universiteit Eindhoven.
    van Noorden, T. L.
    University of Erlangen-Nürnberg, Martensstraße 3, Erlangen 91058, Germany .
    Corrector estimates for the homogenization of a locally periodic medium with areas of low and high diffusivity2013Inngår i: European journal of applied mathematics (Print), ISSN 0956-7925, E-ISSN 1469-4425, Vol. 24, nr 5, s. 657-677Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We prove an upper bound for the convergence rate of the homogenization limit epsilon -> 0 for a linear transmission problem for a advection-diffusion(-reaction) system posed in areas with low and high diffusivity, where epsilon is a suitable scale parameter. In this way we rigorously justify the formal homogenization asymptotics obtained in [37] (van Noorden, T. and Muntean, A. (2011) Homogenization of a locally-periodic medium with areas of low and high diffusivity. Eur. J. Appl. Math. 22, 493-516). We do this by providing a corrector estimate. The main ingredients for the proof of the correctors include integral estimates for rapidly oscillating functions with prescribed average, properties of the macroscopic reconstruction operators, energy bounds, and extra two-scale regularity estimates. The whole procedure essentially relies on a good understanding of the analysis of the limit two-scale problem.

  • 305.
    Mussa, Abdulbaset
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Failure analyses and wear mechanisms of rock drill rods: a case study2019Inngår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 102, s. 69-78Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rock drill rod failure is a big concern for the mining industry. The tough conditions required to break down rock material into small pieces subject rock drill components to high mechanical stresses and corrosion that lead to the failure of the drill rods. This paper describes a detailed examination of rock drill rods failed during field operations. The drill rods were manufactured from a high strength, hardened and tempered steel 22NiCrMo12-5F, carburized for better surface performance. The examination was carried out by means of light optical microscopy and scanning electron microscope. Microhardness profiles were performed for the studied rods. The focus of the present case study was to characterize the failure mechanisms and surface damages of the failed drill rods. The examined drill rods failed due to the initiation and propagation of fatigue microcracks at the outer surface of the thread. Surface cracks propagated to a certain crack length until the fracture toughness of the drill rod was exceeded and the final failure occurred. Multiple short cracks were observed on the fracture surface of the failed rods. The observed cracks propagated perpendicularly to the impacting direction towards the inner surface of the rods. Two different crack initiation mechanisms were observed in the present study, crack initiation from pits and crack initiation from severe plastic surface deformation. Sliding and abrasive wear damage, severe plastic deformation and pitting corrosion were observed on the threaded portion of the rods. Sliding wear was the most common wear damage mechanism observed in the thread joint. Pitting corrosion and severe plastic deformation, made the worn surface susceptible to crack initiation.

  • 306.
    Müller, Christian
    et al.
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Bergqvist, Jonas
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Vandewal, Koen
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Tvingstedt, Kristoffer
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Anselmo, Ana Sofia
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Magnusson, Roger
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Alonso, M. Isabel
    Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Esfera UAB, ES-08193 Bellaterra, Spain.
    Moons, Ellen
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Arwin, Hans
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Campoy-Quiles, Mariano
    Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Esfera UAB, ES-08193 Bellaterra, Spain.
    Inganäs, Olle
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Phase behaviour of liquid-crystalline polymer/fullerene organic photovoltaic blends: thermal stability and miscibility2011Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, s. 10676-10684Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The thermal behaviour of an organic photovoltaic (OPV) binary system comprised of a liquidcrystalline fluorene-based polymer and a fullerene derivative is investigated. We employ variabletemperature ellipsometry complemented by photo- and electroluminescence spectroscopy as well as optical microscopy and scanning force nanoscopy to explore phase transitions of blend thin films. The high glass transition temperature correlates with the good thermal stability of solar cells based on these materials. Furthermore, we observe partial miscibility of the donor and acceptor together with the tendency of excess fullerene derivative to segregate into exceedingly large domains. Thus, for charge generation less adequate bulk-heterojunction nanostructures are poised to develop if this mixture is exposed to more elevated temperatures. Gratifyingly, the solubility of the fullerene derivative in the polymer phase is found to decrease if a higher molecular-weight polymer fraction is employed, which offers routes towards improving the photovoltaic performance of non-crystalline OPV blends.

  • 307.
    Naqvi, Muhammad
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013). Department of Energy, Building, and Environment, Mälardalen University, Sweden.
    Dahlquist, E.
    Department of Energy, Building, and Environment, Mälardalen University, Sweden.
    Yan, J.
    Department of Energy, Building, and Environment, Mälardalen University, Sweden & Department of Chemical Engineering, Royal Institute of Technology (KTH), Sweden.
    Naqvi, S. R.
    School of Chemical & Materials Engineering, NUST, Pakistan.
    Nizami, A. S.
    Center of Excellence in Environmental Studies, King Abdulaziz University, Saudi Arabia.
    Salman, C. A.
    Department of Energy, Building, and Environment, Mälardalen University, Sweden.
    Danish, M.
    State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, ECUST, China.
    Farooq, U.
    State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, ECUST, China.
    Rehan, M.
    Center of Excellence in Environmental Studies, King Abdulaziz University, Saudi Arabia.
    Khan, Z.
    Systems Power and Energy, School of Engineering, University of Glasgow, UK.
    Qureshi, A. S.
    Institute of Biotechnology and Genetic Engineering, University of Sindh, Pakistan.
    Polygeneration system integrated with small non-wood pulp mills for substitute natural gas production2018Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 224, s. 636-646Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study aims to examine the potential substitute natural gas (SNG) production by integrating black liquor gasification (BLG) island with a small wheat straw-based non-wood pulp mills (NPM), which do not employ the black liquor recovery cycle. For such integration, it is important to first build knowledge on expected improvements in an overall integrated non-wood pulp mill energy system using the key performance indicators. O2-blown circulating fluidized bed (CFB) gasification with direct causticization is integrated with a reference small NPM to evaluate the overall performance. A detailed economic analysis is performed together with a sensitivity analysis based on variations in the rate of return due to varying biomass price, total capital investment, and natural gas prices. The quantitive results showed considerable SNG production but significantly reduced electricity production. There is a substantial CO2 abatement potential combining CO2 capture and CO2 mitigation from SNG use replacing compressed natural gas (CNG) or gasoline. The economic performance through sensitivity analysis reflects significant dependency on both substitute natural gas production and natural gas market price. Furthermore, the solutions to address the challenges and barriers for the successful commercial implementation of BLG based polygeneration system at small NPMs are discussed. The system performance and discussion on the real application of integrated system presented in this article form a vital literature source for future use by large number of small non-wood pulp industries.

  • 308.
    Nilsson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper.
    Stepwise Development of a Mathematical Model for Air Flow in Vacuum Dewatering of Paper2014Inngår i: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 32, nr 13, s. 1587-1597Artikkel i tidsskrift (Fagfellevurdert)
  • 309.
    Nilsson, Lars
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Stenström, Stig
    Lunds universitet.
    Predicting water removal during vacuum dewatering from fundamental fibre property data2015Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, nr 2, s. 265-271Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Control of the solids content after vacuum dewatering is vital for efficient control and energy use of the paper machine. Dewatering is a complex function of many parameters such as fibre and pulp properties as well as settings on the paper machine and a predictive model for dewatering will require extensive and detailed studies of the occurring physical phenomena. The hypothesis investigated in the present study is that fibre width and fibre length density measured for fibres suspended in water can be used for estimating the achievable dryness in vacuum dewatering. The hypothesis was tested by comparing model predictions to experimental data for 11 different pulps. The results show that the dryness after vacuum dewatering can be estimated from the fibre length density and the fibre width for the fresh pulps using an elliptical fibre cross-section model with a ratio of 0.48 between the short and long axes. For the dried pulps a lower value was needed to reach a good agreement.

  • 310.
    Nilsson, Lars
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Tysén, Aron
    Innventia AB.
    Vomhoff, Hannes
    Innventia AB.
    The influence of grammage and pulp type on through air drying2015Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, nr 4, s. 651-659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of grammage and pulp type on through air drying was studied. The temperature of a sample was measured during the drying process and the observed temperature changes were used to evaluate the drying process. Laboratory sheets with grammages 15- 60 g/m², from two softwood and two hardwood bleached chemical pulps were used. All samples were analysed with respect to formation, flow resistance, modified permeability, mean drying time, non-uniformity of drying time, and area- and mass-specific drying rate. The pulps had different modified permeabilities but showed similar behaviour when analysed as a function of grammage. A constant value was found for higher grammages, while an increase in modified permeability was found at decreasingly low grammages. Almost all pulp and grammage combinations had similar area-specific drying rates, but the mass-specific drying rates decreased with grammage. However, the samples with lower grammages had mass specific drying rates independent of modified permeability, where samples with increasing grammage showed an increasing dependency. This implies that the drying efficiency at low grammages was not controlled by the volume flow of the drying air. A good correlation was found between energy needed to evaporate water and energy supplied by the drying air as estimated from the surface temperature and air flow measurement. The surface temperature can therefore be used to quantify the drying process.

  • 311.
    Nilsson, Rickard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Optimization of pneumatic activity sensor: Development of a low friction seal2019Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis, the development of a new type of seal is presented along with the steps taken to attain the conclusive design. The results are presented in this paper as a cross-sectioned CAD-model along with the selection of materials and suggestions for future work. The project was commissioned by the multi-discipline engineering consultancy company Projektengagemang AB in Karlstad, Sweden, and carried out as a master’s thesis at Karlstad University. The commission was due to a demand for a new type of sealing solution, as friction is a problem within the field of micro-pneumatics. The work done consists of a study of different low-friction materials where a 30/70 PTFE/PEEK compound was selected as it displayed promising friction and wear properties. The material was then implemented into a design concluded by employing a product development process. The result rendered a prototype for a new kind of low-friction seal which uses the fluid pressure to achieve a sealing contact load between a piston/rod and the seal, which also was the goal set to achieve at the start of the project. Additionally, a design of experiments study was conducted to settle what design parameters were significant with respect to the contact load. For proceeding, making the concept a product ready for production, additional work is needed in the form of experimental material testing, development of a leakage model to optimize the contact load, determination of temperature and creep behaviour, as well as sufficient field testing. Lastly, a die tool must be designed for manufacturing with injection moulding as well as determining if any further processing is required.

  • 312. Nordström, Johan
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Cemented carbides and high speed steels in green wood cutting2005Annet (Annet (populærvitenskap, debatt, mm))
  • 313. Nordström, Johan
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Modelling of tooth edge wear in green wood cutting2005Annet (Annet (populærvitenskap, debatt, mm))
  • 314. Nordström, Johan
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    The influence of tooth bite and cutting speed on wear of swaged saw teeth in timber cutting2002Konferansepaper (Fagfellevurdert)
  • 315. Nordström, Johan
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Wear testing of saw teeth in timber cutting2001Annet (Annet (populærvitenskap, debatt, mm))
  • 316.
    Norrby, Alexander
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Nanotribological characterization of advanced tool steels2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

       Tribological  problems  of  tool–work  piece  interaction  is  a  key  aspect  influencing  product quality,  process  performance  and  tool  lifetime.  For  example,  in  sheet  metal  forming operations, sliding contact may cause adhesive wear of sheet materials with build up of worn material on the tool surface. This tribological problem often resulted in loss of tolerance and product quality and is called galling.  

       It  was  demonstrated  that  tendency  to  adhesive  wear  depends  on  the  steel  grade,  which means high importance of chemical- and phase-constitution of the tool steel. It was suggested that  adhesion  to  the  matrix  is  critical  due  to  metal  to  metal  contact  while  carbide  phase prevent adhesion of conterbody materials. Nevertheless, in macroscale tests it is difficult or even impossible to separate contribution of each phase into the wear mechanism.   

       In the present work, selected steels are to be investigated  at nanoscale by means of AFM facilities. Main attention will be paid on adhesion and frictional properties of steel matrix and primary  phase.  As  expected  and  reported  in  several  articles,  carbides,  carbonitrides  and nitrides   may   behave   differently,   contributing   into   the   final   performance   differently. Additional  attention  will  be  paid  on  phase  size  and  distribution,  meaning  they  are  also important parameters influencing tribological behaviour.

  • 317.
    Nyflött, Åsa
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Development of an Image Processing Tool for Fluorescence Microscopy Analysis of Paper Chemistry2010Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Paper making today is, to some extent, based on empirical knowledge. It is wellknown that fines, pH, charge and ion strength affect the manufacture of paper. One way of extending knowledge of the mechanisms of paper chemistry is to follow the trajectories of fines and additives in the paper suspension to gather information as to the manner in which they react. Four tracking algorithms adapted to the needs of this particular problem were implemented in order to track particles effciently. The tracking algorithms include two variants of the well-known "Lucas-Kanade algorithm" and template matching techniques based on cross-correlation and least squares matching. Although these techniques are similar in principle, the actual tracking can nevertheless differ; the Lucas-Kanade algorithms were found to be more invariant to noise, whereas the cross-correlation and least squares methods are more rapid to execute in Matlab. The tracking methods have been evaluated using a simulator to generate image sequences of synthetic particles moving according to Brownian motion. Tracking has also been evaluated on microscope images of real latex particles where the results have been compared to manual tracking. Tracking of both the simulated particles and the latex particles resulted in similar results when compared to known position and manual tracking, respectively.

  • 318.
    Nyflött, Åsa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Structure-Performance Relations of Oxygen Barriers for Food Packaging2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Food packaging should ensure the safety and quality of food, minimize spoilage and provide an easy way of storing and handling it. Barrier coatings are generally used to meet the demands placed on fibre-based food packages, as these have the ability to regulate the amount of gases that can enter them. Some gases are detrimental to food quality: oxygen, for example, initiates lipid oxidation in fatty foods. Using both experimental data and computer modelling, this thesis explains some aspects of how the structure of barrier coatings influences the mass transport of oxygen with the aim of obtaining essential knowledge that can be used to optimize the performance of barriers.

    Barrier coatings are produced from polyvinyl alcohol and kaolin blends that are coated onto a polymeric support. The chemical and physical structures of these barriers were characterized according to their influence on permeability in various climates. At a low concentration of kaolin, the crystallinity of polyvinyl alcohol decreased; in the thinner films, the kaolin particles were orientated in the basal plane of the barrier coating. The experimental results indicated a complex interplay between the polymer and the filler with respect to permeability.

    A computer model for permeability incorporating theories for the filled polymeric layer to include the polymer crystallinity, addition of filler, filler aspect ratio and surrounding moisture was developed. The model shows that mass transport was affected by the aspect ratio of the clay in combination with the clay concentration, as well as the polymer crystallinity. The combined model agreed with the experiments, showing that it is possible to combine different theories into one model that can be used to predict the mass transport.

    Four barrier coatings: polyethylene, ethylene vinyl alcohol + kaolin, latex + kaolin and starch were evaluated using the parameters of greenhouse gas emissions and product costs. After the production of the barrier material, the coating process and the end-of-life handling scenarios were analysed, it emerged that starch had the lowest environmental impact and latex + kaolin had the highest.

  • 319.
    Nöbauer, Henrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    En utvärdering av metoder för att bestämma den förhöjda arbetstemperaturen vid svetsning av S355J22015Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    En vanlig orsak till brott i svetsade kolstålskonstruktioner kan härledas till små sprickbildningar som uppstår i svetsgodset eller det område av grundmaterialet som har påverkats strukturellt av energin från svetsprocessen, även kallad HAZ. Dessa sprickor uppstår ofta timmar eller dagar efter avslutad svetsning och beror på en kombination av väte, en hård och spröd mikrostruktur och närvaro av spänningar.

    För att undvika dessa sprickor kan man förvärma materialet innan svetsning. Den förhöjda arbetstemperaturen ger en långsammare svalning vilken minskar risken för martensitbildning och låter väte diffundera ut från svetsförbandets kritiska delar. Det finns olika beräkningsmodeller för att räkna ut den förvärmningstemperatur som krävs för att motverka dessa sprickor. De flesta av dem är grafiska men försök har gjorts att översätta dessa till matematiska algoritmer. Beräkningsmodellerna kan ge väldigt varierande temperaturer och olika modeller kan anses vara bäst tillämpade till olika stål. I denna rapport har det undersökts vilken beräkningsmodell som är bäst lämpad för konstruktionsstålet S355J2. Modellerna som har använts är den matematiska CET, de grafiska CEIIW och CEN samt matematiska tolkningar av de två sistnämnda. Utvärderingen har gjorts genom att svetsa upp prover på plåtar med en godstjocklek på 30 mm med en stegvis ökande förhöjd arbetstemperatur. Dessa prover har sedan genomgått både oförstörande och förstörande provning för att undersöka hur sprickbenägna de är. En analys av svetsförbandets mikrostruktur har också genomförts för att identifiera de mest kritiska zonerna.

    Det visade sig att de matematiska tolkningarna av de grafiska metoderna skiljde sig såpass mycket från sina grafiska motsvarigheter att de inte kan rekommenderas för användning.

    Det visade sig även att det inte fanns en beräkningsmodell av ursprungsmodellerna som var bäst lämpad för S355J2 utan valet berodde helt och hållet på vilken sträckenergi som användes då modellerna tar olika mycket hänsyn till denna. För en sträckenergi på över 1,6 kJ/mm rekommenderas CET-metoden som beräknade en temperatur som gav goda materialparametrar. För sträckenergier under 0,9 kJ/mm beräknar ingen metod en tillräckligt hög temperatur, men CEIIW är den som beräknar den högsta förhöjda arbetstemperaturen och rekommenderas därför för användning. Man bör dock ha i åtanke att den inte var tillräckligt hög och bör därför ses som en lågt räknad rekommendation.

    Mellan 0,9 kJ/mm och 1,6 kJ/mm har inga prover svetsats men rekommendationen är att använda sig av CET-metoden då den är enkel och beräknar högst temperatur.

    Vad det gäller svetsförbandets kritiska zoner så visade det sig att korntillväxtzonen var området där vätesprickor har störst förutsättningar för att uppstå. 

  • 320.
    Ohlsson, Jonas
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Effects of different heat treatments on hardness of Grade 91 steel2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    CCI Valve Technology AB is a company located in Säffle, Sweden, that manufactures and installs bypass valves. Due to requirements outside normal standards on the valve's hardness values, some measurements have had difficulties meeting such requirements. During this thesis work, tests were carried out to determine how to overcome the difficulties. The experiments focused on five different areas that may affect the components hardness, welding method, soaking temperature during post weld heat treatment, measuring procedure, component thickness and number of heat treatment cycles. The Grade 91 steel specimens that were examined consisted of five solid cylinders and three various pipes that were welded together by using shielded metal arc welding (SMAW) or gas tungsten arc welding (GTAW). Each pipe was sawed apart into three equal parts. All specimens were hardness tested and eight of the specimens' microstructure was studied with an optical microscope. The hardness measurement instruments used, LECO V-100-C2 and GE-MIC 10, are Vickers hardness testers, one stationary and the other one portable. The measuring results contain a vast number of different hardness measurement data. From the analyzed data, the conclusions were drawn that the most suitable soaking temperature during post weld heat treatment were 750° C, that the SMAW method creates a more stable hardness profile than the GTAW method, and that one heat treatment cycle is more beneficial than two or more.

  • 321.
    Ohlsson, Richard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Variations in hardness and microstructure in cartridge cases at annealing2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The thesis work is performed at Norma Precision AB, a company that manufactures ammunition for hunting and competitive shooting. Two types of cases called 300 Winchester Magnum and 308 Winchester are examined on how their hardness were prior to and after the two annealing’s of the neck they experience during the manufacturing. The cases vary in hardness and an investigation will be made to draw connections to the microstructure of the cases in order to understand the variations and possibly avoid the variations in the future.

    The cases were selected at different days, the 300 Winchester Magnum were chosen at three different days with some properties varying and the 308 Winchester were taken at two different days. At each day twenty cases were selected, five prior to the first neck annealing, five after the first neck annealing, five after the shaping and calibrating of the cases and the final five after the second neck annealing.

    The selected cases were first measured by a hardness test, where they were measured at 1mm, 3mm and 6mm from the nuzzle and five times around the case at each measurement. After that, the variations were analyzed and the two most varying cases from each day and step were taken into the laboratory at Karlstad University. In the laboratory, the cases were measured by a microhardness tester. The cases were measured at even distances between them all throughout the cases to make a hardness profile. The next step was to etch the cases and examine them in an optical microscope, where the grain size was measured in micrometer and ASTM.

    The results from the regular hardness measurements and the microhardness tests showed similar tendencies. Variations was found in each step and each day during both hardness measurements the two types of cases behaved similarly. The grain size results showed that after annealing, the grain size increased. Although there was no clear relation between grain size and hardness since the results varied, some cases with higher hardness had a smaller grain size than a case with lower hardness.

    Using the grain size of the brass could work to get an idea of the hardness, but to get a sincerer perception of the material properties, more properties needs to be investigated.

  • 322.
    Olsson, Oskar
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Research Of Non-Stick Materials For Applications In Tissue Machines2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis have investigated a few materials that exhibits non-stick

    properties for applications in tissue machines. In the process of making

    tissue there is problems with build up of fibres and glue. To

    overcome these problems Valmet AB are looking to find coatings that

    will facilitate cleaning.

    The main problem area is the drying section where glue is used to

    help the sheet to stick to the steam filled Yankee cylinder which is

    performing the final drying of the sheet.

    A basic discussion of the theory behind surface properties is made

    before the materials are chosen, experiments are conducted and results

    presented. The materials are ranked in order of performance based on

    the experimental data. To ensure that the top performing materials

    can be applied to usage in a real tissue machines a few possible future

    studies is suggested.

    The top performing materials were fluoropolymers. These materials

    are very expensive which making their usage limited to critical parts.

    Two silicon based materials performed at a surprisingly high level

    making them highly attractive for wider usage in less critical areas in

    a tissue machine.

  • 323. Ottosson, Martina
    Investigation of wear behavior of different sliding bearing materials in an alkaline environment2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In sliding bearing wear is a very common problem and can be affected by several factors. The wear in a bearing can lead to total failure of the component and lower the lifetime. In a sliding bearing used in a machine in the pulp and paper industry large wear has been detected, but no clear evidence of what the wear depends on. The environment in the machine is strong alkaline (pH 14), a solution of white liquor and lime mud. The penetration of this solution into the bearing might lead to increased wear. A wear study and test were done to see if a better material choice could reduce the wear.

    In this project an investigation of the wear for seven different bearing materials was done. Two cobalt-based alloy Stellite 6 and Stellite 12, two different precipitation hardened martensitic stainless steel with different number of alloying elements, 17-4PH and Endotec 04. The different metals were welded on the pin with a minimum of 3mm. The other material was three different PEEK polymer composites. PEEK HPV reinforced with carbon fiber, PTFE and graphite. PEEK CA30 with carbon fibers and PEEK GF30 with glass fiber.

    The method used for the wear test was grinding machine that was reconstructed to a pin-on-disc tribology test. The tests were executed in room temperature with sliding speed of 150rpm and duration of 20 minutes. The metals were tested with the solution of white liquor mixed with lime mud, at two different loading conditions of 300N and 550N. The polymer composites were tested at the load of 300N but with different solution present, white liquor mixed with lime mud and with water. All the pins were sliding against a disc of austenitic stainless steel.

    Equipment used to investigate the wear mechanisms was a scanning electron microscope. The wear rate was measured by weighing of the pin before and after each test. How the material was affecting the roughness of the austenitic steel countersurface was done with the profilometer.

    The results of this work showed that both Stellite 6 and Stellite 12 was almost wear resistance in the condition similar to the bearing. Endotec 04 also showed low wear and 17-4PH had the highest of the metals. The dominant wear mechanism seemed to be different severity of adhesive wear. The polymer composite showed all higher wear than the metals, the reason to the high wear rate was harder to decide. It might be a combination between adhesive wear, pulverization of fibers, adsorption of calcium carbonate and matrix/fiber interfacial removal. The alkaline liquid was also believed to increase the wear of the polymer and adhere to some of the metals. The metals seemed to increase the roughness of the countersurface, but the polymers seemed to have more of a polishing effect. 

  • 324.
    Pavlopoulou, E.
    et al.
    University Bordeaux, France.
    Fleury, G.
    University Bordeaux, France.
    Deribew, Dargie
    University Bordeaux, France.
    Cousin, F.
    CEA Saclay, France.
    Geoghegan, M.
    University Sheffield, England.
    Hadziioannou, G.
    University Bordeaux, France.
    Phase separation-driven stratification in conventional and inverted P3HT:PCBM organic solar cells2013Inngår i: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 14, nr 5, s. 1249-1254Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have used neutron reflectivity to investigate the stratification of poly(3-hexylthiophene) (P3HT) and phenyl-C-61-butyric acid methyl ester (PCBM) blend films. Films were spun-cast on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) and titanium oxide (TiOx) layers to mimic the procedures followed for the fabrication of conventional and inverted organic photovoltaics respectively. The resultant scattering length density profiles reveal a PCBM-rich layer is formed in the vicinity of PEDOT: PSS or TiOx, while PCBM is depleted at the free surface of the film. PCBM segregation close to the substrate is further enhanced by annealing. This stratification is considered to be favorable only for inverted devices. (C) 2013 Elsevier B. V. All rights reserved.

  • 325.
    Pernefur, Emil
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Extremvärdesanalys (SEV) av högkvalitativt verktygsstål: Uppskattning av maximal inneslutningsstorlek i pulverstål2017Independent thesis Basic level (degree of Bachelor), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    This work were requested by Uddeholms AB. Uddeholm is the worldś leading manufacturer of high performance tool steel for industrial tools. The company exists worldwide and is present in over 100 countries. One of the company’s main production processes is manufacturing powder steels with extremely high quality. In this work, one of these steels has been analyzed to evaluate the presence and distribution of non-metallic inclusions.

    Higher demands on quality and more global competition worldwide means that you always have to strive towards perfection in the manufacturing processes. Non-metallic inclusions have severe effects on the mechanical properties of steels. That's why it's of utmost importance to investigate their presence in the tool steel and especially their size. The reason for this is because it's the largest inclusions that's the most dangerous for the material.

    To obtain a statistically number of certainty of the largest of inclusions, very vast areas of steel have to be examined. Therefore a theoretical method of extrapolation is often used instead to approximate the distribution of the largest inclusions. The precision of this method is still very uncertain. Different methods of this kind of analysis do exist. The method applied in this work of degree is extreme values analysis by statistics of extreme values (SEV).

    To ensure the pre-conditions of the extreme values analysis, a large quantity of powder steel was analyzed. This was done by light-optic microscopy (LOM) and exclusively performed by Uddeholms AB at their R&D-facility (Research and development-facility) in Hagfors.

    At Karlstad Universityś test-facility specimens were subjected to ultrasonic fatigue testing at 20 kHz. The specimens derived from the same material as the ones examined in LOM. The result from the ultrasonic fatigue testing were that the largest inclusions in the material were found. This was done by applying very high cycle fatigue (VHCF).

    To calculate the maximum theoretical inclusion size, SEV was used. The extreme values analysis was performed on gathered data from both LOM and VHCF.

    All fracture surfaces from the ultrasonic fatigue testing were then examined in scanning electron microscope (SEM) at Karlstad University. In SEM, the largest inclusion in every fractured surface was identified and measured.

    The maximum real inclusion size from the fractured surfaces was then compared to the maximum theoretically calculated inclusion size from the extreme values analysis. As it turned out the real inclusion size proved to be slightly larger than the theoretical. The difference between them was found to be 3,25 µm.

    Conclusions drawn were that Uddeholms powder steel exhibits very high purity and that extreme values analysis as an analytical method is recommended. However, the analysis should be repeated to underline the chosen solution methodology.

  • 326. Persson, A
    Thermomechanical Fatigue and Corrosive Wear of Hot Work Tool Steels in Die Casting2000Rapport (Annet vitenskapelig)
  • 327. Persson, A.
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Burman, Christer
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Evaluation of heat checking damage in die casting1999Konferansepaper (Fagfellevurdert)
  • 328. Persson, A
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Burman, Christer
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Hogmark, S
    Experimental Investigation n thermal fatigue of a surface engineered hot work tool steel2001Konferansepaper (Fagfellevurdert)
  • 329. Persson, A
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Burman, Christer
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Hogmark, S
    Influence of deposotion temperature and time during PVD coating of CrN on corrosive wear in liquid aluminium2001Inngår i: Surface and coatings Technology, 146-147, 2001, 42Artikkel i tidsskrift (Fagfellevurdert)
  • 330. Persson, A
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Hogmark, S
    Influence of surface engineering on the performance of tool steels for die casting2002Inngår i: / [ed] J Bergström, G Fredriksson, M Johansson, O Kotik, F Thuvander, 2002Konferansepaper (Fagfellevurdert)
  • 331. Persson, A
    et al.
    Hogmark, S
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Failure modes in field-tested brass die casting dies2003Annet (Annet (populærvitenskap, debatt, mm))
  • 332. Persson, A
    et al.
    Hogmark, S
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Simulation and evaluation of thermal fatigue cracking of hot work tool steels2004Inngår i: International Journal of Fatigue, Volume 26, Number 10, 2004Artikkel i tidsskrift (Fagfellevurdert)
  • 333. Persson, A
    et al.
    Hogmark, S
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Temperature profiles and conditions for thermal fatigue cracking in brass die casting dies2004Inngår i: Journal of Materials Processing Technology, v 152, n2, 2004Artikkel i tidsskrift (Fagfellevurdert)
  • 334. Persson, A
    et al.
    Hogmark, S
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Thermal fatigue cracking of surface engineered hot work tool steels2005Inngår i: Surface and Coatings Technology, volume 191, Issues 2-3, 21 February 2005Artikkel i tidsskrift (Fagfellevurdert)
  • 335.
    Pettersson, Viktor
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Study of the effect of process parameters in laser blown powder with superalloys: Varying laser power and scanning speed, analyzing material properties2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Additive manufacturing (AM) is a growing process interesting many companies in many industries. Thereare multiple processes within the familty of AM, but this study focuses on laser blown powder (LBP). LBP involves a laser beam focused on the substrate with powder being blown into the laser beam. The laser beam melts both the powder and the surface of the substrate and as the laser beam moves and the melt pool solidies it leaves a bead of solid material behind. These beads are placed next to each other creating a layer which are then stacked, building the wanted geometry. As the method develops new materials are tested and this study analyses Haynes 282 powder onto Inconel 718 substrate. Multiple process parameters are involved in the LBP method and this study focuses on the impact of laser effect and scanning speed. Each value on the process parameters was inspired by previous reports with similar equipment and process. The laser effect ranges from 1600 W to 700 W, scanning speed ranges between 900 mm/min to 300 mm/min and the powder feeding rate was also varied from 4 g/min to 3 g/min. Each sample was built as a single bead and a multilayer specimen, which is ve layers and 16 beadswide at the bottom and 12 beads wide at the top. When analyzing the samples images from microscopes were mostly used for obtaining results. An image software called ImageJ allowed measurements in an image to obtain penetration depth or primary dendrite arm spacing. ImageJ also allowed measurements of porosity by turning the image binary and calculate the fraction of white and black. The results consists of numerical values and visual analysis of the bead geometry, minimum and maximum penetration, microstructure, porosity, hardness and cracks. The results show an increased bead width around 2 mm to 4 mm and decreased bead height around 0,2 mm to 0,7 mm of single beads with increased laser effect. Increased maximum penetration depth around, 200 μm to 500 μm, withincreased laser effect. More remelt between each deposited layer causing longer dendrites with increasinglaser effect. Porosity is decreased with an increased laser power, going from 0,04 % to 0,15 %. No distinct difference in hardness is observed between the samples, ranging between 255 HV to 310 HV. It is believed that aging causes the increased hardness right above the fusion zone. Cracks were found between dendrites and is believed to be caused by Laves-phases. Most results are comparable to previous similar studies, both as trends and numerical values. The statistics of the study is limited, meaning that all results should not be taken as granted but as a general guide line for more studies. The purpose and goals of the study has been met and completed.

  • 336.
    Rahman, H.
    et al.
    Mittuniversitetet.
    Engstrand, P.
    Mittuniversitetet.
    Sandström, P.
    SCA R&D.
    Sjöstrand, Björn
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Dewatering properties of low grammage handsheets of softwood kraft pulps modified to minimize the need for refining2018Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, nr 3, s. 397-403Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous paper (Rahman et al. 2017) showed that the yield of softwood kraft pulp increased by the addition of either polysulfide or sodium borohydride because of higher hemicellulose retention. An increase in hemicellulose content can make dewatering more difficult as WRV of the pulp increases, but instead, an overall increase in pulp yield could improve dewatering as a sheet of a certain weight will contain fewer fibres, giving a more open sheet structure. It was therefore of interest to measure the dewatering properties of low grammage handsheets (20 g/m2) under conditions mimicking the tissue paper machine dewatering processes, and sheet strength properties, WRV, °SR and fibre dimensions were also studied. The results showed that the positive influence of overall yield increase dominated over the negative influence of an increase in hemicellulose content on the dewatering properties, particularly at lower refining energy levels. Moreover, higher yield and higher hemicellulose content pulps had a higher tensile index at the same dryness. A given tensile index was achieved with less refining energy. The results indicate that increased yield and hemicellulose content by modification of the kraft pulping process will result in a pulp with a potential to improve tissue paper quality.

  • 337.
    Rashid, Lezan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Overlay welding of FeCrAl alloys2016Independent thesis Advanced level (degree of Master (Two Years)), 300 hpOppgave
    Abstract [en]

    In this master thesis different overlay welding methods suitable for boiler application has been investigated.

    The purpose of this project is to define advantages and disadvantages for each overlay welding methods and suggest some evaluation criteria on some commercial and experimental alloys aimed for overlay welding material.

    Many components in a boiler are made of low alloy steel and the atmosphere in the furnace region can be very complex; therefore many different types of corrosion can occur. Weld overlay is a process where one or multiple layers of corrosion resistant material are applied to a base material.

    The two overlay welding methods investigated in this study were Tungsten Inert Gas welding and Metal Inert/Active Gas welding. Tests were performed with FeCrAl alloys (Kanthal A, Kanthal D and some experimental alloys). FeCrAl alloys in general are ferritic iron-based steels with a typical concentration of 20-23 wt. % chromium and ~5 wt.% aluminum.

    Different overlay welding evaluation was made; visual examination, dye penetrant inspection, macro/micro examination, side bend test and short term corrosion test (~50hours).

    Conclusion of this thesis is that MIG welding is a more productive method than TIG, but more defects such cracks and lack of fusion can be produced for MIG welding. These defects can be “fixed” if welding parameters is optimized. If repairing a certain place TIG welding is a better option. A conclusion about number of layers; one layer with MIG welding is almost as thick as three layers with TIG welding with welding wire Ø 1mm.

    Three welding evaluation that is really important is visual examination, dye penetrant testing and corrosion test in order to choose which overlay welding method is suitable in boiler application.

  • 338.
    Rasmusson, Gunnar
    Karlstads universitet, Institutionen för ingenjörsvetenskap, fysik och matematik.
    Analys av tryckslag i rörsystem2006Independent thesis Basic level (professional degree), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Sammanfattning

    När en rörledning skall dimensioneras måste den designas för att tåla de tryck som uppstår under stationära förhållanden. Ledningen måste också klara de tryck som kan uppstå under instationära förhållanden, t ex då en ventil stänger eller öppnas. Om en ventil stänger och flödet minskar så omvandlas vätskans rörelseenergi till tryckenergi. Om detta sker snabbt så kallas detta för tryckslag. De tryck som uppstår då kan leda till skador på rörledningar och annan utrustning i ett system.

    Dessa tryck kan simuleras med hjälp av datorprogram. Det finns också förenklade metoder för att beräkna dessa tryck. Dessa förenklade metoder är dock bara giltiga under speciella omständigheter.

    En ca 6000 m lång råvattenledning mellan sjön Hällungen i Stenungsunds kommun och en reservoar i Stenungsund har nyligen dimensionerats med hjälp av en förenklad beräkningsmetod för tryckslag. Det finns dock en misstanke att dessa metoder ger felaktiga resultat, vilket kan göra att ledningen blir över eller underdimensionerad.

    Studiens syfte är att ta reda på hur mycket resultaten från de förenklade beräkningsmetoderna skiljer sig från mer noggrannare simuleringar, samt under vilka förutsättningar dessa metoder gäller.

    Två förenklade metoder beskrivs i rapporten. Rapporten beskriver även en metod som kallas karakteristikmetoden, som är en metod som de flesta kommersiella programvaror använder.

    Dessa metoder tillämpas på det aktuella fallet och resultaten jämförs.

    Resultaten visar att de förenklade metoderna bara gäller under vissa speciella fall.

    Rapporten bekräftar att dessa ekvationer bara kan användas under speciella fall och med stor försiktighet. De kan dock ofta fungera som en första koll för att få reda på ungefärliga värden.

    När dessa förenklade metoder går att använda är bl a kopplad till hur fort en ventil stänger samt ledningens periodtid, d.v.s. den tid det tar för en tryckvåg att gå fram och tillbaka i en ledning.

  • 339. Razaz, Ghadir
    Casting practices influencing inclusion distribution in Al-billets2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 340.
    Renaud, Cedric
    et al.
    University Bordeaux, France.
    Mougnier, Sebastien-Jun
    University Bordeaux, France.
    Pavlopoulou, Eleni
    University Bordeaux, France.
    Brochon, Cyril
    University Bordeaux, France.
    Fleury, Guillaume
    University Bordeaux, France.
    Deribew, Dargie
    University Bordeaux, France.
    Portale, Giuseppe
    University Bordeaux, France.
    Cloutet, Eric
    University Bordeaux, France.
    Chambon, Sylvain
    University Bordeaux, France.
    Vignau, Laurence
    University Bordeaux, France.
    Hadziioannou, Georges
    University Bordeaux, France.
    Block Copolymer as a Nanostructuring Agent for High-Efficiency and Annealing-Free Bulk Heterojunction Organic Solar Cells2012Inngår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 24, nr 16, s. 2196-2201Artikkel i tidsskrift (Fagfellevurdert)
  • 341.
    Rixen, Alexandra
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Energieffektivisering i ett reningsverk för skogsindustriellt avloppsvatten genom förfällning av extraktivämnen2011Independent thesis Basic level (university diploma), 20 poäng / 30 hpOppgave
    Abstract [en]

    Pulp- and papermills expend vast amounts of water in order to produce pulp, paper and cardboard. Hence, they alsocreate vast amounts of waste water which has to be cleaned before it can be released into the receiving body of water. Insuch a wastewater treatment plant, tremendous amounts of energy are expended by the aeration in the biologicalcleaning process. This aeration is necessary to supply the microorganisms that shall decompose organic material withoxygen, which they need for their metabolism. The transfer of oxygen from the gas phase to the liquid phase isprimarily inhibited by surface-active substances in the waste water like resin acids or fatty acids. The purpose of thisthesis has been to determine if the surface-active substances can be removed by means of chemical pre-precipitationbefore the waste water enters the biological cleaning step. Thus, the efficiency of the aeration shall be improved.In the laboratory, aeration tests were performed for plain water, water with added surface-active substances and CTMPwastewaterfrom Stora Enso Skoghalls Bruk. The test for water with added surface-active substances showed clearlythat these substances have a big influence on the aeration efficiency, which was impaired considerably compared withplain water.In order to determine how chemical precipitation influences the content of surface-active substances, screening trialswere performed with the CTMP waste water. The concentration of surface-active substances was estimated bymeasuring the surface tension of the waste water. The surface tension sinks with increasing concentration of thesesubstances. 250 ml CTMP-wastewater was precipitated with three different chemicals: PAX-XL60, PGA and AVR. Inorder to determine the optimal dosing as well as the optimal pH-value for goal-oriented precipitation of the surfaceactivesubstances, the precipitation was performed with different pH-values between 4 and 8 as well as for differentdoses of the precipitation chemicals. It was discovered that the optimal pH-value for precipitation with PAX-XL60 is7,5 while the precipitation with PGA had the optimal pH-value of 6. The optimal dosage for PAX-XL60 was 10 g/cm3,while the optimal dosage for PGA could not be determined because of the small waste water volume used in thescreening trials. The screening trials showed that the surface tension increased after precipitation with both PAX-XL60and PGA which leads to the assessment that the concentration of surface-active substances has decreased.Precipiation- and aeration trials in big lab-scale were performed at pH 7,5 and the optimal dosage of PAX-XL60. ForPGA, the precipitation and aeration trials were performed at pH 6 and the lowest dosage of the screening trials. Theaeration trials showed that precipitated CTMP-wastewater could be aerated more energy efficient than the samewastewater without precipitation.Calculations showed that energy costs can be reduced by nearly 90% by using the tested precipitation chemical PAXXL60respectively nearly 65% by using the tested precipitation chemical PGA according to the lab-scale trials. Thecosts for the chemicals are not included.

  • 342. Rättö, P.
    et al.
    Barbier, Christophe
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Rigdahl, M.
    An investigation of the friction properties of coated paper2000Inngår i: Nordic Pulp and Paper Research JournalArtikkel i tidsskrift (Fagfellevurdert)
  • 343. Rättö, Peter
    et al.
    Hornatowska, Joanna
    Barbier, Christophe
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Influence of the distribution of the shape and size distribution of pigment particles on cracking in coating layers during creasing2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 4, s. 714-720Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The crack area on a coated board was measured after creasing and folding and the crack area on a coated copy paper was measured after folding. A clay pigment and two Ground Calcium Carbonate (GCC) pigments were used. The GCC pigments differed in their particle size distribution. The binder was either an S/B latex or an S/B latex combined with starch. The type of pigment seemed to have the greatest influence on the crack area in creased and folded board. Clay showed a larger crack area than the GCC with a broad particle size distribution. The GCC with a narrow particle size distribution showed a considerably larger crack area than both the clay pigment and the GCC with a broad particle size distribution. The coatings containing starch generally showed a larger crack area than the coatings that only contained the S/B latex. After the folding of the copy paper, the crack area showed a slightly different pattern. Here, it seemed that the binder was of greater importance than the type of pigment, with the coatings containing only latex showing a considerably lower crack area than the coatings containing starch. The coatings that were based on the clay pigment showed similar values as the coatings based on the GCC pigment with the broad particle size distribution. The coatings based on the GCC with the narrow particle size distribution showed displayed considerably higher crack areas than the coatings based on the other two pigments. The cracking tendency of the coatings, based on the GCC with the narrow particle size distributions was probably due to a greater demand for latex, i.e. smaller particles in the GCC with broad particle size distribution would probably fill in the voids and the GCC with the broad particle size distribution will therefore demand less binder. It was further suggested that the different loadings on the coating layer during the creasing and folding of the board, compared to the folding of copy paper, explain the different results obtained with the two base-substrates. 

  • 344.
    Rådberg, Malin
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    Design of Experiment for Laser cutting in Superalloy Haynes 2822016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This project aims to investigate the effect of varying different laser cutting parameters on the laser cut surface. The parameters that were varied were cutting speed, beam effect, gas pressure and focal point. The statistical method Design of Experiment was used to plan the experiments and two full factorial test plans were set up, one with argon as cooling and protective gas and one with nitrogen. Sheet metal consisting of the superalloy HAYNES ® 282 with a thickness of 2,54 mm was investigated. Samples from the material were cut with different laser cutting parameters according to the test plans. The samples were evaluated by measuring cracks, recast layer thickness, surface irregularity, burr height and distance to beam deflection point on the cut surface. The resulting data was inserted as responses into the statistical program Modde 10.1 for analysis.

    Modde 10.1 provided models of high significance for the responses of Recast layer, Tav; Recast layer, Tmax; Burrheight, max and Distance to deflection point for the argon series and Recast layer, Tav and Recast layer, Tmax for the nitrogen series.

    The results showed that both recast layer thickness and burr height decreases with increased values of cutting speed, gas pressure and focal point as well as decreased values of beam effect within the parameter window investigated. They also showed that distance to deflection point increased with increasing values of gas pressure and focal point and with decreased values of cutting speed and beam effect within the parameter window.

    The results also showed that for the samples cut with argon as cooling and assistant gas the parameters that affects the recast layer thickness the most are focal point and gas pressure, whereas for the nitrogen series it is gas pressure and beam effect. The parameter with greatest effect on burr height is the cutting speed and for the distance to deflection point it is focal point and gas pressure that have the greatest effect.

    When comparing the argon and the nitrogen series to each other it can be seen that the argon series generate less recast layer from the entry of the cut until between 60 – 80 % into the cut, after which the argon series bypasses the nitrogen series in amount of recast layer produced in the cutting process in the majority of the places measured.

  • 345.
    Sadek, Mohamed
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Hallbäck, Nils
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Burman, Christer
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    20 kHz 3-point bending fatigue of automotive steels2018Inngår i: MATEC Web of Conferences, EDP Sciences, 2018, Vol. 165, s. 1-7, artikkel-id 22020Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The 20 kHz load frequency enables fatigue tests for very high cycle fatigue life, 109-1013 cycles, within conveniently short time. In automotive applications, many components are subjected to flexural loading and hence bending fatigue is an important test mode. Ultrasound fatigue test instruments have been used successfully in several assessments of fatigue strength and more commonly in uniaxial loading. Here, a 3-point bending fatigue test rig operating in resonance at 20 kHz load frequency has been designed to test plane specimens at R=0.1 loading. The test rig design and stress calculations are presented. Testing for fatigue strength was conducted using the staircase method with 15 specimens of each steel grade, specimens reaching 108 cycles were considered run-outs giving fatigue strength at 108 cycles. Additional 15 specimens of each grade were tested for S-N curves with the upper limit above 109 cycles. Two different common automotive steels, 38MnSiV5, a micro-alloyed ferritic-pearlitic steel, and 16MnCr5, a carburizing martensitic steel, were tested. The fatigue strengths achieved from the staircase testing are 340 and 419 MPa stress amplitudes for the 38MnSiV5 and 16MnCr5 steels, respectively. The S-N curves of the steels appear to be quite flat in the tested life range 107 - 109.

  • 346.
    Sadek, Mohamed
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Hallbäck, Nils
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Burman, Christer
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Computation of and testing crack growth at 20 kHz load frequency2016Inngår i: 21ST EUROPEAN CONFERENCE ON FRACTURE, (ECF21) / [ed] F. Iacoviello, L. Susmel, D. Firrao, G. Ferro,, Elsevier, 2016, s. 1164-1172Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fatigue properties are evaluated in a large span of fatigue lives ranging from a few load cycles to more than 1013 load cycles. If the interest is focused on fatigue lives above 10(7) load cycles, we speak of the very high cycle fatigue (VHCF) range. For evaluation of properties in the VHCF range one often needs to use higher load frequencies to be able to perform testing within a reasonable time. Therefore, the influence of load frequency on fatigue strength and fatigue crack growth is an important issue, both from testing and design perspectives. Within an EU-RFCS research project on the frequency influence on high strength steel fatigue properties the present study has been conducted on fatigue crack growth testing to determine threshold values and crack growth material parameters. The testing was analyzed by FE-computation to determine geometry factors for AK-determination. The testing was performed in a 20 kHz ultrasound resonance instrument. In such a system the whole load train needs to be designed to run at a resonance frequency of 20 kHz, and it implies that the specimen needs to be designed and computations performed by dynamic computational methods. As the crack grows the dynamic response of the specimen will change, and hence calculation to obtain the geometry factor is made with a progressing crack length. A uniaxial tensile load at 20 kHz frequency is applied to a single edged notched side-grooved flat specimen. The specimen dimensions are calculated in order to have a resonance frequency of 20 kHz, which is the frequency used for the experiments. Dynamic FEM computation, with a 3D-model and a quarter symmetry was used with one of the symmetry planes parallel to and in the crack growth line. To avoid crack surface interpenetration during the simulations a rigid thin sheet was introduced and used as a counter-face to the crack surface. The solution obtained was then combined with the breathing crack model proposed by Chati et. al. (1997) in order to solve for the irregularities observed when crack surface interpenetration occurs. Finally, the whole load train was considered. Thus, also the computed frequencies were very close to frequencies observed in experiments. The computation of stress intensities was made for varying crack lengths in a series of simulations. The geometry factor relation was determined and used in 20 kHz crack growth testing to control the actual stress intensity at the advancing crack tip. Comparison of computations and experimental results were made.

  • 347.
    Salvati, E.
    University of Oxford, Engineering Science Department.
    Papadaki, C.
    University of Oxford, Engineering Science Department.
    Zhang, H.
    University of Oxford, Engineering Science Department.
    Mousavi, Mahmoud
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Wermeille, D.
    ESRF European Synchrotron Radiation Facility.
    Korsunsky, A.M.
    University of Oxford, Engineering Science Department.
    Nanoscale Structural Damage due to Focused Ion Beam Milling of Silicon with Ga ions2018Inngår i: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 13, s. 346-349Artikkel i tidsskrift (Fagfellevurdert)
  • 348.
    Samuelsson, Jörgen
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Eiriksson, F. F.
    University of Iceland.
    Åsberg, Dennis
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Thorsteinsdóttir, M.
    University of Iceland.
    Fornstedt, Torgny
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Determining gradient conditions for peptide purification in RPLC with machine-learning-based retention time predictions2019Inngår i: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1598, s. 92-100Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A strategy for determining a suitable solvent gradient in silico in preparative peptide separations is presented. The strategy utilizes a machine-learning–based method, called ELUDE, for peptide retention time predictions based on the amino acid sequences of the peptides. A suitable gradient is calculated according to linear solvent strength theory by predicting the retention times of the peptides being purified at three different gradient slopes. The advantage of this strategy is that fewer experiments are needed to develop a purification method, making it useful for labs conducting many separations but with limited resources for method development. The preparative separation of met-enkephalin and leu-enkephalin was used as model solutes on two stationary phases: XBridge C18 and CSH C18. The ELUDE algorithm contains a support vector regression and is pre-trained, meaning that only 10–50 peptides are needed to calibrate a model for a certain stationary phase and gradient. The calibration is done once and the model can then be used for new peptides similar in size to those in the calibration set. We found that the accuracy of the retention time predictions is good enough to usefully estimate a suitable gradient and that it was possible to compare the selectivity on different stationary phases in silico. The absolute relative errors in retention time for the predicted gradients were 4.2% and 3.7% for met-enkephalin and leu-enkephalin, respectively, on the XBridge C18 column and 2.0% and 2.8% on the CSH C18 column. The predicted retention times were also used as initial values for adsorption isotherm parameter determination, facilitating the numerical calculation of overloaded elution profiles. Changing the trifluoroacetic acid (TFA) concentration from 0.05% to 0.15% in the eluent did not seriously affect the error in the retention time predictions for the XBridge C18 column, an increase of 1.0 min (in retention factor, 1.3). For the CSH C18 column the error was, on average, 2.6 times larger. This indicates that the model needs to be recalibrated when changing the TFA concentration for the CSH column. Studying possible scale-up complications from UHPLC to HPLC such as pressure, viscous heating (i.e., temperature gradients), and stationary-phase properties (e.g., packing heterogeneity and surface chemistry) revealed that all these factors were minor to negligible. The pressure effect had the largest effect on the retention, but increased retention by only 3%. In the presented case, method development can therefore proceed using UHPLC and then be robustly transferred to HPLC.

  • 349.
    Sandberg, Maria
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för energi-, miljö- och byggteknik.
    Rixen, Alexandra
    Chemical flocculation as pretreatment for energy efficient biological treatment2012Inngår i: 10th IWA Symposium on Forest Industry Wastewater and 8th International Conference on the fate and effect of Pulp and Paper Mill Effluents, 2012, s. 42-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Biological treatment of forest industry wastewaters uses large amounts of electrical energy. For many mills aeration is the single most energy intensive process in the wastewater treatment plant. The oxygen transfer from bubbles into the water volume is quite slow with low aeration efficiency as result. If the oxygen transfer can be improved, the efficiency can be improved and less compressed air will be needed for aeration with decreased energy costs as the result. It has been shown that surface-active extractives, such as fatty acids and resin acids, have a large impact on oxygen transfer in diffuser aeration systems. With chemical flocculation, extractives can be removed from the process streams. Trials have been made where pulp-mill process streams were pretreated with chemical flocculation before the oxygen transfer tests. When the chemical flocculation conditions were optimized to increase surface tension in the process stream, extractives were removed and the oxygen transfer rate increased in the following oxygen transfer tests. With the pretreatment also COD concentration decreased. The effect will be less need for oxygen for degradation in the following biological process. With decreased COD concentration and increased oxygen-transfer rate, energy can be saved in the biological treatment. Energy savings resulted in greater economic return than the cost for flocculating chemicals. If waste sludge can be used as energy source, one can even achieve a better result.

    Acknowledgements. This work was supported by ÅF-forskningsstiftelse and Stora Enso Skoghall mill.

  • 350.
    Sannemalm, Örjan
    et al.
    Karlstads universitet, Institutionen för ingenjörsvetenskap, fysik och matematik.
    Svensson, Magnus
    Karlstads universitet, Institutionen för ingenjörsvetenskap, fysik och matematik.
    Vibrationsanalys: Vibrationsproblem i travers2007Independent thesis Basic level (professional degree), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Som en del i Maskiningenjörsutbildningen vid Karlstads Universitet har detta examensarbete utförts under en 15 veckors period. Uppdragsgivare är Scana Steel AB:s stålverk i Björneborg och arbetet behandlar en av deras traverser. Arbetet bestod i att lokalisera och om möjligt förinta vibrationer som uppfattas som störande i förarhytten till traversen. För att lokalisera vibrationerna har olika analyser genomförts med hjälp av SpectraPro samt Vibshape, vilket är två mjukvaror tillhörande mätutrustningen Easy Viber. Dessa två program ger oss möjlighet att se animeringar av traverskroppens rörelse och visa spektran för specifika punkter.

    Analyserna visar på att förarhytten huvudsakligen rör sig vid tre olika frekvenser. Frekvenserna i hytten visar sig överensstämma med frekvenserna från det sista kuggingreppet på växellådan samt från kopplingen mellan motor och växellåda. En del resonansfenomen har tagits i beaktning.

    Metoderna för att undvika att föraren känner obehagliga vibrationer är flera och skiljer sig stort i hur omfattande operationer som krävs. Det finns dock några åtgärder som smidigt kan prövas.

    Föreslagna åtgärder för avhjälpning av vibrationerna innefattar bland annat frekvensstyrning, dynamisk dämpare och dämpande maskinfötter.

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