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  • 251.
    Lindberg, Therese
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Modelling and Evaluation of Distributed Airflow Control in Data Centers2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this work a suggested method to reduce the energy consumption of the cooling system in a data center is modelled and evaluated. Introduced is different approaches to distributed airflow control, in which different amounts of airflow can be supplied in different parts of the data center (instead of an even airflow distribution). Two different kinds of distributed airflow control are compared to a traditional approach without airflow control. The difference between the two control approaches being the type of server rack used, either traditional ones or a new kind of rack with vertically placed servers. A model capable of describing the power consumption of the data center cooling system for these different approaches to airflow control was constructed. Based on the model, MATLAB simulations of three different server work load scenarios were then carried out. It was found that introducing distributed airflow control reduced the power consumption for all scenarios and that the control approach with the new kind of rack had the largest reduction. For this case the power consumption of the cooling system could be reduced to 60% - 69% of the initial consumption, depending on the workload scenario. Also examined was the effect on the data center of different parameters and process variables (parameters held fixed with the help of feedback loops), as well as optimal set point values.

  • 252.
    Lindgren, Alexander
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    Implementeringsutmaningar vid införande av tillståndsbaserat underhåll på reglerventiler inom ett kartongbruk.: En fallstudie utförd på ett kartongbruk i Sverige.2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 253.
    Lindqvist, Camilla
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    van Stam, Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Fullerene aggregation in thin films of polymer blends for solar cell applications2018Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 11, nr 11, artikkel-id 2068Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the effects of the film morphology on the fluorescence spectra for a thin film including a quinoxaline-based co-polymer (TQ1) and a fullerene derivative ([6,6]-phenyl-C71-butyric acid methyl ester-PC70BM). The ratio between the polymer and the fullerene derivative, as well as the processing solvent, were varied. Besides the main emission peak at 700 nm in the fluorescence spectra of thin films of this phase-separated blend, a broad emission band is observed with a maximum at 520-550 nm. The intensity of this emission band decreases with an increasing degree of mixing in the film and becomes most prominent in thicker films, films with high PC70BM content, and films that were spin-coated from solvents with lower PC70BM solubility. We assign this emission band to aggregated PC70BM.

  • 254.
    Lindroos, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Copper-related light-induced degradation in crystalline silicon2015Doktoravhandling, med artikler (Annet vitenskapelig)
  • 255.
    Lindroos, Jeanette
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Department of Micro- and Nanosciences, Aalto University.
    Boulfrad, Yacine
    Yli-Koski, Marko
    Savin, Hele
    Preventing light-induced degradation in multicrystalline silicon2014Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 15, artikkel-id 154902Artikkel i tidsskrift (Fagfellevurdert)
  • 256.
    Lindroos, Jeanette
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Petter, Kai
    Hanwha Q CELLS GmbH.
    Sporleder, Kai
    Fraunhofer Center for Silicon Photovoltaics CSP.
    Turek, Marko
    Fraunhofer Center for Silicon Photovoltaics CSP.
    Pacho, Paolo
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Rinio, Markus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Light beam induced current of light-induced degradation in high-performance multicrystalline Al-BSF cells.2017Inngår i: Proceedings of the 7th International Conference on Silicon Photovoltaics, SiliconPV 2017, 3-5 April 2017, Freiburg, Germany / [ed] Ralf Preu, Elsevier, 2017, Vol. 124, s. 99-106Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Sponge-LID decreases the Al-BSF cell efficiency by up to 10 %rel. and is only partially recoverable at 200°C. This contributionshows that Sponge-LID occurs at and near most grain boundaries, but only in the centre of the affected cell.  Furthermore,Sponge-LID is not the only type of LID in the silicon bulk. High-resolution Light Beam Induced Current mapping reveals localinternal quantum efficiency losses of up to 8 %rel. at dislocation clusters and small angle grain boundaries, which recover(nearly) fully at 200°C. Nevertheless, this dislocation-related LID appears to reduce the Al-BSF efficiency by less than 1 %rel.

  • 257.
    Lindroos, Jeanette
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Finland.
    Savin, Hele
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Review of light-induced degradation in crystalline silicon solar cells2016Inngår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 147, s. 115-126Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Although several advances have been made in the characterization and the mitigation of light-induced degradation (LID), industrial silicon solar cells still suffer from different types of light-induced efficiency losses. This review compiles four decades of LID results in both electronic- and solar-grade crystalline silicon. The review focuses on the properties and the defect models of boron-oxygen LID and copper-related LID. Current techniques for LID mitigation are presented in order to reduce cell degradation and separate copper-related LID from boron-oxygen LID. Finally, the review summarizes recent observations of severe LID in modern multicrystalline silicon solar cells.

  • 258.
    Lindström, Björn
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Metodik för analys av batteriets laddningscykel i entreprenadmaskiner: Prototypbyggnad och teori2015Independent thesis Basic level (degree of Bachelor), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Volvo Construction Equipment AB, Volvo CE, är en global tillverkare av entreprenadmaskiner. Detta exjobb fokuserar på batterierna i dessa entreprenadmaskiner som försörjer maskinens elsystem och startmotor vid start.

    Med dagens teknik ställs nya krav på strömförsörjning i entreprenadmaskiner. Den största skillnaden är att förbrukare är igång när motorn är avstängd och strömförsörjningen kommer enbart från batteriet. Ett startbatteri av bly-syra typ är inte konstruerad för detta användningsfall. Volvo CE jobbar därför med att ta fram kunskap om hur laddningen i batterierna används och cyklas under drift.

    Frågeställning om vilka parametrar och trender som är relevanta för att utvärdera batteriladdning har behandlats i detta arbete. Bakomliggande teori har undersökts, förklarats och vidareutvecklats i beskrivningen av den föreslagna metodiken för analys av batteriladdningsnivå i entreprenadmaskiner.

    En metod för hur identifierad relevant mätdata skall extraheras ur entreprenadmaskinerna har beskrivits i samband med beskrivningen av den utvecklade och framtagna prototyputrustningen.

    Den i detta arbete föreslagna analysmetodiken för dimensionering av batterikapacitet och tillämpad på mätdata från batteriladdningen under driftsmässiga förhållanden för entreprenadmaskiner kan också hjälpa till att ge svar på om de batterier som idag används av Volvo CE är lämpliga i den nya generationens entreprenadmaskiner.

    Arbetet innehåller ett nyhetsvärde för Volvo CE och andra då den föreslagna analysmetodiken inte beskrivits eller tillämpats tidigare på Volvo CE. Arbetet ger också förslag på hur man kan gå vidare i kunskapsuppbyggnaden och utvecklingsarbetet kring batterier inom Volvo CE.

  • 259.
    Lindvall, Fredrik W.
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Study of the influence of contact geometry and contact pressure on sliding distance to galling in the Slider-On-Flat-Surface wear tester2013Inngår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 56, nr 6, s. 1137-1145Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the major causes of tool failure in sheet metal forming is wear in the form of galling. Galling is gradual buildup of adhered sheet material on the tool and leads to unacceptable scratches on the sheet surface and to components that fail to meet tolerances. Because it is difficult to reproduce operational and interactional conditions in laboratory test equipments it is hard to test, model, and predict galling initiation.Here the authors examine how changes from elliptical to line contact geometry influenced galling initiation under dry sliding by using a slider-on-flat surface (SOFS) wear tester. A micro clean tool steel was tested against ferritic low-strength and martensitic high-strength steel sheets.The sliding distance to galling initiation was extracted from friction data and verified by scanning electron microscopy (SEM) observations. The presence of adhesive wear on worn tools after completed tests was used as a criterion. Experimental results showed that the elliptical contact causes galling quicker than the line contact.Applicability of experimental results depends on the relevance of test conditions, so contact pressures calculated for the described tests were compared to calculated contact pressures in a semi-industrial U-bending test and to literature data relevant to industrial applications. Good agreement between values observed for SOFS and for most selected industrial applications was found, which assume that contact pressures typical for most common industrial applications can be successfully simulated by selection of tool geometry and normal load in the SOFS tester.

  • 260.
    Lundin, Lukas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Tip vortex cavitation and diffused vorticity of propeller profiles: a modelling approach: Investigation of an implemented TVI model, and  implementation and investigation of a DVH model2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    To predict fluid properties and interactions is an important task for the industry. It is plagued, however, by being close to impossible to predict analytically. Hence, it is customary to turn to numerical solutions. This in itself comes with many different methods and approaches suitable for different needs. This work focuses on two methods: Tip Vortex Index (TVI) and Diffused Vortex Hydrodynamics (DVH). TVI is a method to predict when a marine propeller will experience cavitation of tip vortices and is based on calculations from a Boundary Element Method (BEM). DVH is a particle method for simulating the circulation of a fluid in two dimensions and three dimensions. The aim is to investigate an implemented TVI model based on MPUF-3A for different marine propeller series, with different sub-designs for a total of 28 unique propellers, and implement the DVH method and test it for 3 different bodies. The results of this thesis show that the implemented TVI model is non-functional for the 28 different propellers, but the DVH method is successfully implemented and able to handle 2 different bodies.

  • 261.
    Lundskog, Måns
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Analysis of 3D design tools for tubing and piping design: Evaluating E3D and CATIA for on-machine tubing and piping design of paper machines using the analytic hierarchy process2019Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    This thesis covers a degree project for a Bachelor of Science in mechanical engineering degree and is written on behalf of Valmet AB. The purpose of the project is to evaluate and analyse the differences between CATIA and E3D and conclude which of the software is most suitable for on-machine tubing and piping design at Valmet. The tubing and piping modules in CATIA are currently used but is considered somewhat ineffective. E3D is also used at Valmet but in another branch of engineering design, namely field pipe engineering.

    The analysis is done using the analytic hierarchy process (AHP) which is a multi-criteria decision making (MCDM) methodology developed to aid in complex decision-making problems. The methodology follows a six-step process which results in a prioritized ranking or relative weight of both alternatives with respect to the established criteria and sub-criteria for selection. A total of four main criteria and 12 sub-criteria for the selection of the most suitable CAD system were identified and analysed with the help of relevant personnel in various departments such as engineering, purchasing and management

    The results of the project conclude that E3D is the preferred CAD system for on-machine tubing and piping at Valmet with regards to the given criteria and sub-criteria. The criteria that favoured E3D most were the availability of the systems, meaning the possibility that Valmet can outsource projects to consultants, as well as the more effective 3D modelling process. However, the results are not heavily one-sided which suggest that more research should be done before a final decision can be taken.

    The suggested further research includes looking at the in-direct implications of using a new CAD system such as computer updates and the usage of a new PLM system. Moreover, the actual performance of 3D modelling using the two systems is beyond the scope of this thesis and would have to be further researched in another thesis or a pilot case.

  • 262.
    Malmborg, Petter
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Engine air filter requirements: How different running conditions affect service life2019Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    The internal combustion engine requires clean air in order to operate without problems the entire service life. The air filter acts as a barrier between the ambient air ridden with particulate matter, and the sensitive interior of the engine. Several factors affect the air filter performance, such as pressure drop, efficiency, and dust holding capacity. Many external factors affect the air filter too, such as driving style, engine type, if the car is equipped with hybrid propulsion et cetera.

    The scope for this thesis work aims to extend the knowledge of air filtration for the customer, in this case, Volvo Cars. A comprehensive literature study along with benchmarking of competitors acts as a foundational approach. Regarding air filter service life, three parameters are identified as the most significant: dust holding capacity, efficiency and pressure drop over the filter element.

    Reverse engineering shows some competitor design decisions. A model of estimating air consumption is developed using a data-driven approach with real-world driving data as a basis. The model shows how much the actual air consumption varies between different markets and various engines. As a result, the service lifetime of air filters in certain cars with certain engines may be extended or allow for a smaller filter size for the same service lifetime.

  • 263.
    Maninnerby, Henrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Simulering av ett elnät med hänsyn till förnybar energi: En studie av möjliga lösningar på problemet med fler elbilar i elnätet2018Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    The purpose of this thesis is to simulate different scenarios where all vehicles are replaced by electric vehicles in the future.

     

    An addition of electric vehicles to the electric grid is not easy to handle, especially not if the consumers choose to charge their vehicles with higher power. As can be seen in the results of this report, flexible demand through power management is a good option to reduce overall power consumption. Of course, customers will have to agree to that their consumption is controlled in this manner.

     

    Using solar cells during the summer works well, but it’s harder wintertime as the largest electric demands arise during the night, when there is close to no sunlight. However, in the case of batteries, they may be helpful. Possibly by letting the solar cells charge the battery during the day and then use it to help charge the electric vehicle during the night. Unfortunately, it was not possible to include this scenario as the used software was unable to handle batteries in that way.

     

    By completely replacing the heat source, in this case with district heating, and thus releasing available power in the transformer, turned out to be the best option. In this way, virtually all predicted amounts of electric cars could be charged with optional charging strength between 3.7 and 11 kW.

     

    As for the T422 transformer, there is no choice but to replace it if a larger number of electric vehicles wants to start charging there. At present, it can handle a maximum of 10-20 electric vehicles that charge at the lowest power as there is only about 50 kW available there winter time.

    District heating cannot be applied either as the connected customers do not use electric heating.

  • 264.
    Michels, Jasper J.
    et al.
    Holst Centre/TNO, Eindhoven, The Netherlands.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Simulation of Surface-Directed Phase Separation in a Solution- Processed Polymer/PCBM Blend2013Inngår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 46, nr 21, s. 8693-8701Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation of the surface-induced stratified lamellar composition profile experimentally evidenced in spincoated layers of the photovoltaic donor–acceptor blend consisting of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole]/phenyl-C61-butyric acid methyl ester (APFO-3/PCBM), as processed from chloroform, is simulated using square gradient theory extended with terms describing the interaction of the blend components with the air and substrate interfaces. The surface energy contributions have been formulated based on an enthalpic nearest-neighbor model which allows integration of common surface tension theory and experimentally accessible surface energies of the fluid phase constituents with a mean field description of a multicomponent blend confined by substrate and air interfaces. Using estimates for the quench depth and transport properties of the blend components as a function of polymer concentration, the time-resolved numerical simulations yield results that compare favorably with experimental observations, both in terms of the number of lamellae as a function of the blend layer thickness and their compositional order. The effect of blend ratio is reproduced as well, the lamellar pattern becoming more pronounced if the amount of PCBM increases relative to APFO-3.

  • 265.
    Mikael, Olsson
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Framtagning och implementering av arbetssätt för utveckling av kostnadseffektiva reservdelar2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Detta examensarbete har utförts som en del av civilingenjörsprogrammet i maskinteknik vid Karlstads Universitet i samarbete med Valmet. För Valmet är försäljning av reservdelar är en vital del av deras totala affär. I avsikt att stärka konkurrenskraften mot kunder i framförallt lågkostnadsländer vill Valmet erbjuda mer kostnadseffektiva lösningar genom att utveckla konstruktionen på befintliga reservdelar. Målet med examensarbetet var därför att ta fram ett systematiskt arbetssätt för produktutveckling av kostnadseffektiva reservdelar och validera det genom implementering på en befintlig produkt i Valmets reservdelssortiment.

     

    Underlaget till det framtagna arbetssättet samlades in genom att utföra en litteraturstudie, en nulägesanalys på Valmet och en intervju på ett företag som är framgångsrikt inom eftermarknad. Arbetssättet syntetiserades som en process med stöttande riktlinjer genom att utgå från Valmets befintliga utvecklingsprocess och integrera teoretiska modeller, principer och verktyg ur vetenskaplig litteratur. Arbetssättet testades sedan på lutmunstycken för sodapannor.

     

    Grunden för det framtagna arbetssättet bestod av en kombination av Value Management och Design to Cost. Fokus i arbetssättet ligger vid att utveckla en reservdel som återställer systemet till sitt normala arbetstillstånd, för ett pris som kunden är beredd att betala, och som balanserar tillförlighet med tillgänglighet så att den totala kostnaden för kunden minimeras.

     

    Genom att implementera det framtagna arbetssättet på lutmunstycken för sodapannor kunde ett förslag på en lösning med 66 % lägre pris och med 50 % lägre total kostnad för kunden tas fram. Implementeringen visade att arbetssättet praktiskt kan användas på enklare reservdelar men att det behöver testas på komplexa produkter av ett tvärfunktionellt team innan det används av Valmet.  Arbetssättet stärker Valmets förutsättningar för att erbjuda ett mer kostnadseffektiv reservdelsortiment.

  • 266.
    Milesson, Joel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Karlstad Universiy.
    Simulering av hydrodynamisk kraftverkan på vattenkolven i ett punktabsorberande vågkraftverk2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Vågenergi är en nära helt oanvänd förnybar energiresurs med enorm potential och många fördelar jämfört med andra förnybara energikällor. Men havsmiljön är hård och krafterna kan bli mycket stora vilket ställer höga krav på vågkraftverkets konstruktion. Detta har förhindrat ett kommersiellt genombrott för vågkraften.

    Waves4Power har utvecklat ett vågkraftverk, WaveEL, som består av en flytboj och en vertikal cylinder med vattenkolv. Vattenpelaren i cylindern oscillerar i takt med vågorna och driver vattenkolven. Ett hydraulsystem bromsar vattenkolvens rörelser och utvinner energi ur vågorna. Mellanrummet mellan vattenkolv och cylindervägg kallas läckspalt och varierar i storlek över kolvens slaglängd.

    Hur kraftverkan på kolven ser ut vid olika flöden i cylinder och läckspalt är mindre känt. Om läckspalten är för stor förlorar kraftverket i effektivitet medan kraftverkan på kolven minskar. Är läckspalten istället för liten medför detta att geometrisk orundhet kan leda till skador. Det är också möjligt att kavitation uppstår runt kolven vilket innebär påfrestningar för konstruktionen.

    Simulering av kraftverkan genomfördes i COMSOL Multiphysics för att kartlägga kraftverkan och finna ett samband mellan kraftverkan på vattenkolven och andra variabler samt undersöka kavitationsrisken.

    Ett linjärt, dimensionslöst samband mellan kraftverkan på vattenkolven och en funktion beroende av flödeshastighet, kolvradie, periodtid och läckspaltens storlek togs fram.

    De områden som under vissa givna förutsättningar kan utsättas för kaviterande ångblåsor har sammanställts och resultatet visar hög risk för kavitation då kolven befinner sig i övre bypass-sektionen.

  • 267.
    Mogren, Anna
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Sund, Per
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013). Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013), Science, Mathematics and Engineering Education Research (SMEER).
    The work of higher education institutions to promote sustainable development2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In March 2016, the Swedish Higher Education Authority (UKÄ) was tasked by the Swedish government to conduct an evaluation of how universities and university colleges promote sustainable development, pursuant to the provisions of the Higher Education Act (1992:1434) introduced ten years earlier, 2006. The evaluation has resulted in a unique collection of empirical material that would have been difficult for an individual researcher to collect independently. The evaluation includes an analysis, but is related to background theory not a strict scientific study.  The empirical material could, however, form a basis for numerous interesting studies on, for example, the important factors for successfully working to integrate sustainable development into higher education. A comparison between nations is also possible to conduct based on the methodology of self-reporting by Higher Education institutions, HEI:s. 

     

    The evaluation defined sustainable development by the Bruntland detention, that the present and future generations are ensured a healthy and good environment, financial and social welfare, and justice. The evaluation was limited to the educational area of sustainable development, education for sustainable development ESD. 

     

    The purpose of the evaluation was to contribute with knowledge and a national comparison of HEIs, work with ESD,  and also to present the results that have been achieved so far. The evaluation was further conducted to give support to the HEIs development work on ESD.

     

    Success factors of a positive ESD implementation due to pre-defined criteria were identified in the  evaluation; the significance of management and control, building institutional support and providing support in implementation.  Apart from investigated criteria, factors that showed effects on a positive ESD implementation was also identified in the evaluation. An example is that several of the large and medium-sized HEIs referred their ESD work from teaching- and engineering programmes, which is the only two programmes where sustainable development is included in the national qualitative programme targets. Central bodies with specific responsibilities for sustainable development was also appointed an important structure in translating ESD policy document to the local context and practice. An interesting finding  was the link between HEIs rated high in this evaluation, to institutions with an environmental management system intended to improve the organisation’s environmental performance and contribute to national environmental goals and to the achievement of UN global goals for sustainable development. Such system takes a wider responsibility of sustainable development than education but seems influential and important in HEIs ESD work. A remaining challenge for a majority of HEIs in Sweden is the process of sustainable development in education where the ESD perspective is not only accounted for as a specific content in education but also a driving force to reach high quality education and society transformation.

  • 268.
    Moletsane, M G
    et al.
    Cent Univ Technol, Dept Mech & Mech Engn, Bloemfontein, Free State, South Africa.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Kazantseva, N
    Urals Branch Acad Sci, Inst Met Phys, Ekaterinburg, Russia.
    du Plessis, Anton
    Univ Stellenbosch, CT Scanner Facil, Stellenbosch, South Africa.
    Yadroitsava, I
    Cent Univ Technol, Dept Mech & Mech Engn, Bloemfontein, Free State, South Africa.
    Yadroitsev, I
    Cent Univ Technol, Dept Mech & Mech Engn, Bloemfontein, Free State, South Africa.
    Tensile properties and microstructure of direct metal laser-sintered TI6AL4V (ELI) alloy2016Inngår i: South African Journal of Industrial Engineering, ISSN 1012-277X, E-ISSN 2224-7890, Vol. 27, nr 3, s. 110-121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Direct metal laser sintering (DMLS) is an additive manufacturing technology used to melt metal powder by high laser power to produce customised parts, light-weight structures, or other complex objects. During DMLS, powder is melted and solidified track-by-track and layer-by-layer; thus, building direction can influence the mechanical properties of DMLS parts. The mechanical properties and microstructure of material produced by DMLS can depend on the powder properties, process parameters, scanning strategy, and building geometry. In this study, the microstructure, tensile properties, and porosity of DMLS Ti6Al4V (ELI) horizontal samples were analysed. Defect analysis by CT scans in pre-strained samples was used to detect the crack formation mechanism during tensile testing of as-built and heat-treated samples. The mechanical properties of the samples before and after stress relieving are discussed. 

  • 269.
    Mollaei, Yaghoub
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Shahmohammadi, Kaveh
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Design and Simulation of Nano-plasmonic Filter based on Nonlinear Nanocavity2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 270.
    Mossberg, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    On the use of two sampling strategies for solving an errors-in-variables problem2015Inngår i: 2015 EUROPEAN CONTROL CONFERENCE (ECC), IEEE, 2015, s. 1778-1783Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Two sampling strategies are used for solving an errors-in-variables problem where the system as well as the white measurement noises are of a continuous-time nature. The sampling strategies are integrated sampling, and lowpass filtering followed by instantaneous sampling. Covariance relations are derived and systems of equations are formed for the data obtained from the two sampling strategies, and parameter estimators based on these relations and equations are proposed.

  • 271.
    Mossberg, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Performance analysis and filter choice for an errors-in-variables method2016Inngår i: 2016 EUROPEAN CONTROL CONFERENCE (ECC), IEEE, 2016, s. 1371-1376Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An errors-in-variables problem where the system as well as the white measurement noises are in continuous-time is considered. Due to the intrinsic nature of the measurement noises, a strategy of lowpass filtering followed by instantaneous sampling is used for obtaining data from the system. A previously developed covariance function based parameter estimation method is first slightly improved. Thereafter, it is analyzed by evaluating the covariance matrix of the estimated parameter vector. Three different expressions for a generic element of an intermediate matrix in the expression for the covariance matrix are derived. One exact but computationally demanding, one approximate valid for small sampling intervals, and one exact for the case when the sampling interval tends to zero. The covariance matrix can be used for studying the influence of some user parameters, including the choice of the lowpass filter, on the quality of the estimated parameter vector.

  • 272.
    Mossberg, Magnus
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Irshad, Yasir
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Closed-loop Identification of Stochastic Models from Filtered Data2008Konferansepaper (Fagfellevurdert)
  • 273.
    Mossberg, Magnus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Sinn, Mathieu
    Cross-correlations of zero crossings in jointly Gaussian and stationary processes with zero means2017Inngår i: 2017 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 5-9 March 2017, New Orleans, LA, IEEE, 2017, s. 4286-4290Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Zero crossing data contain information of a process in compact form and is therefore of interest in wireless sensor networks where only reduced amounts of data can be transmitted. When analyzing the properties of certain algorithms using zero crossing data, the cross-covariance between the zero crossing rates of two jointly Gaussian and stationary processes is needed. The evaluation of such a cross-covariance is considered in the paper and an exact numerical expression as well as an asymptotic expression are presented.

  • 274.
    Mossberg, Magnus
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Söderström, Torsten
    Uppsala University.
    Covariance matching for continuous-time errors-in-variables problems2011Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 56, nr 6, s. 1478-1483Artikkel i tidsskrift (Fagfellevurdert)
  • 275.
    Mossberg, Magnus
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Söderström, Torsten
    Uppsala University.
    On covariance matching for multiple input multiple output errors-in-variables systems2012Inngår i: IFAC Proceedings Volumes / [ed] Kinnaert, Michel, Elsevier, 2012, Vol. 45, s. 1371-1376Konferansepaper (Fagfellevurdert)
  • 276.
    Mousavi, Mahmoud
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Tehran Polytechnic, Iran.
    Fariborz, Shahriar
    Tehran Polytechnic, Iran.
    Anti-plane elastodynamic analysis of cracked graded orthotropic layers with viscous damping2012Inngår i: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 36, nr 4, s. 1626-1638Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stress analysis is carried out in a graded orthotropic layer containing a screw dislocation undergoing time-harmonic deformation. Energy dissipation in the layer is modeled by viscous damping. The stress fields are Cauchy singular at the location of dislocation. The dislocation solution is utilized to derive integral equations for multiple interacting cracks with any location and orientation in the layer. These equations are solved numerically thereby obtaining the dislocation density function on the crack surfaces and stress intensity factors of cracks. The dependencies of stress intensity factors of cracks on the excitation frequency of applied traction and material properties of the layer are investigated. The analysis allows the determination of natural frequencies of a cracked layer. Furthermore, the interactions of two cracks having various configurations are studied.

  • 277.
    Mussa, Abdulbaset
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    Wear characterization and wear mapping of a coated cutting tool: Development of cutting tool test fixture and wear testing2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Wear mechanisms of the cutting tools are well investigated worldwide. Usually researchers use the cutting process itself, turning by single point cutting, as their investigation method, which includes turning a metal cylinder with a pre-selected work-material and predetermined cutting conditions. Thereafter the tool worn surface is examined by scanning electron microscopy in order to characterize the tool wear mechanisms and tool failure. However, this may be the most appropriate way to investigate the wear mechanisms which occur during machining since it simulates the real operation. Metal cutting involves extreme conditions such as high temperature and high-pressure and the different condition results in different wear modes on the insert’s surface. The wear modes are overlapping and the transition boarder between them are not sharp making it difficult to obtain a detailed information of wear mechanisms. Because of these reasons many researchers try to refine the machining to a single condition e.g; high pressure, at the laboratory level in order to characterize the wear mechanisms and to get a more detailed information.

    In this thesis the wear tests of the cutting tool are performed by using a slider-on-flat-surface (SOFS) wear tester. SOFS involves a normal load, which applies to the sample and a tangential force that enables the sliding of the sample against a counterface. To enable conducting the wear tests in SOFS a newly design of tool holder was prepared. The wear tests were performed at different contact conditions and the stainless steel EN 1.4310 was used as the counterface material. After the tools were tested, the worn surface of the tool was examined by optical light microscopy and scanning electron microscopy in order to identify the wear rate and wear mechanisms.

    At low load the dominating wear mechanism was adhesive wear. The adhesive wear was induced by material pick-up during sliding i.e. material from the counterface was transferred to the insert’s surface. Further sliding results in delamination of the insert surface and removal of a part of the coatings material.

    At high load the dominating wear mechanism was a combination of severe adhesive wear and fracture of the coating material. The fracture of the coating material occurred because of overloading. Coating defects promote crack formation under high load and these cracks propagate through the coating during sliding movement and result in microchipping of the coating material.

    This procedure does not simulate the metal cutting but it still gives an understanding of the behavior of the coating material when it is exposed to a high mechanical stress.

  • 278.
    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.

  • 279.
    Möllberg, Nadine
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Retractable Boarding Step to Scania Crew Cab: Product Development, Design, FEM Simulations and Verification2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis treats the development of a new solution for a retractable boarding step to Scania trucks, which is a part of the modular system.

    Some customers have the need to transport additional passengers. For such applications, Scania provides trucks featuring a Crew Cab, which is an extended cab with rear doors. Easy exit through the rear doors is important for many customers who use this type of cabin. Therefore, there is a possibility to get a retractable boarding step, equipped with an upper step and a lower foldable, that enables easy entry and exit. This function is especially important for fire fighters carrying heavy equipment and therefore has more difficulties exiting the truck. The robustness and dependability of the function is critical to ensure the safety. If it fails, the legal requirements are not met while driving or even worse, injury may occur. Pneumatics is used for the fold out of the step and a spring folds it in.

    The current boarding step needs improvement in order for it to be dependable and robust. If the boarding step have not been folded out, the entry and exit of the cab is not possible.

    This thesis covers the product development, simulations and verification of a new boarding step concept that shall improve the entry- and exit function, making it more robust and dependable. Through problem identification, a product specification and a thorough concept generation and development process a final concept has produced.

    Simulations were made in order to verify that the step could be stepped on when entering and exiting the cab.

    The result was a lower step, sliding on linear bearings in a linear motion. This enabled egress and ingress independent of the extraction or retraction of the step. This makes it more reliable than the current product. The sliding mechanism need to be tested in order to ensure the robustness. A prototype was made in order for the function to be tested. 

  • 280.
    Neale, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Byggkonstruktion i förskolan.: En studie om 4-5 åringars intresse och förkunskaper till byggkonstruktion.2014Independent thesis Advanced level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Denna studie syftar till att se på hur barn tar sig an konstruktionsritningar i jämförelse med fritt byggande i en lekfull gruppmiljö. Tidigare forskning visar skillnad mellan mängden män och kvinnor i tekniska yrken och även män och kvinnors inställning till de tekniska ämnena. Vissa forskare visar också på åldersskillnader mellan hur barn lär sig tekniska ämnen. Tar fyra- och femåringar frivilligt sig an konstruktionsritningar, följer dem och färdigställer de konstruktionen? Studien har särskilt tittat på om det fanns skillnader mellan flickorna och pojkarna när de byggde? Hur påverkar barnens eget intresse hur de bygger? Om barn, fyra och fem år gamla kan följa bygginstruktioner?

    Resultatet av denna studie, i viss mån, stödjer tidigare forskning om att det finns en genus aspekt redan i förskoleåldern, pojkarna var mer försekomna och hade lättare för att följa lego instruktioner än flickorna, men frågan kvarstår; varför finns denna skillnad? Förutom genusaspekten fanns det också ett tydligt resultat som visade på skillnad i byggkunskap mellan fyraåringar och femåringar. Fyraåringarna utforskade främst byggmaterialet, medan många av femåringarna kunde följa en Legobygginstruktion näst intill perfekt.

  • 281.
    Ng, Amos
    et al.
    Högskolan i Skövde.
    Adolfsson, Josef
    Sundberg, Martin
    De Vin, Leo
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Virtual Manufacturing for Press Line Monitoring and Diagnostics2008Inngår i: International journal of machine tools & manufacture, ISSN 0890-6955, E-ISSN 1879-2170, Vol. 35, s. 565-575Artikkel i tidsskrift (Fagfellevurdert)
  • 282.
    Nilsson, Frida
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013), Science, Mathematics and Engineering Education Research (SMEER).
    Hole transport layers in organic solar cells: A study of work functions in nanofilms2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Organic solar cells have been showing promise as a way of producing renewableenergy with the help of light, flexible, and production effective materials.The efficiencies and lifetimes reached in organic solar cells have steadily beenincreasing over the years as more research in the field is being conducted.One way of increasing the efficiency in organic solar cell devices is introducingan interlayer between the photoactive material and the anode, referred toas the ’hole transport layer’. Most commonly used as a hole transport layer isthe material PEDOT:PSS, which offers desired properties such as transparency,simple processing and good ohmic contact between anode and photoactive material.PEDOT:PSS is also known to be a degradation site in organic solar cells,as it will corrode the electrode in the presence of water.This project has consisted of investigating PEDOT:PSS along with two othercandidates that may one day come to replace PEDOT:PSS as the most commonlyused material, molybdenum trioxide (MoO3) and phosphomolybdic acid(PMA). The aim was to investigate how the different materials energy bandstructure would be affected upon exposure to sunlight, air and annealing, byobserving the work function under different conditions.

  • 283.
    Nordin, Adam
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Översyn av bältessträckning i ViscoNip-vals2018Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    The report was a finalization part of the thesis bachelor work in mechanical engineering at Karlstad University. A review of the ViscoNip roll belt stretch was made to Valmet. The background to the project was that the belts became resistant to wear, which meant that it was no longer necessary to adjust the machine direction. Previously the belt was moved in the machine direction to expose a new and fresh surface to even the wear. The increased quality of the belt has led to the possibility of applying a fixed side. The goal with the thesis work was to minimize the cost of the belt tension. 

    The project has gone thru a development process where project planning, product specification, concept generation, concept evaluation and layout design was included. Through a cost analysis and input from the relevant fitters and service staff, it was found that a trapezoidal screw was a highly rated solution for the head adjustment. Due to the requirement for continuous belt tension, the trapezoidal screw and a fixed end could not be combined.  As there were several advantages with the trapezoidal screw, a solution was created that was to combine a trapezoidal screw with a spring. These along with a fixed head became the winning concept.

    Before the thesis work, the cost of the ViscoNip roll belt stretch was 226 321 kr. In that price was installation, hydraulics, trapezoidal screw and displacement components.  Upon completion of the thesis, a fixed side was applied to the driving side together with a trapezoidal screw combined with a driver's spring. The estimated cost was instead 155 477 kr, a saving of 70 845 kr.

  • 284.
    Norstedt, Rickard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Verktyg för tillskärning av nätisoleringsmatta: Produktutvecklingsprojekt för en effektivare och mer användarcentrerad metod för tillskärning av nätisoleringsmattor2013Independent thesis Advanced level (professional degree), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    This report covers a product development project conducted as Bachelor of Science thesis forthe Innovation & design engineer program at Karlstad University.The assignment was supplied by MMB Consulting, Kristinehamn. The purpose of this projectwas to find an alternative way of shaping wire-net insulation mats. This insulation product isused for fire and thermal insulation of technical installations. The insulation consists of stoneor glass wool with a sewn on steel wire netting on the out facing side. This netting has thepurpose to enable fastening to e.g. ventilation ducts and to provide bounding of joints. Thiswire netting makes regular methods for fitting stone or glass wool non applicable. Theexisting method for shaping wire-net insulation has flaws due to not being designed for thisapplication. These flaws include poor ergonomics, efficiency and low result quality.The objectives with this project is to find a new method that makes fitting of wire-netinsulation more efficient and safer for the user regarding personal safety and ergonomics.The work has been conducted according to the methods of the industrial product developmentprocess and the design methodology.The project resulted in a motor driven tool for shaping wire-net insulation that according to atheoretical foundation has proven to be more user adapted through being designed for goodergonomics and by offering a simpler handling. This solution is also considered to be moreefficient and to give better results than the present solution. Some correlation betweenreductions in energy losses from technical installations and the new method is detectable.

  • 285.
    Nyflött, Åsa
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Meriçer, Çağlar
    Bologna University.
    Minelli, Matteo
    Bologna University.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Jarnstrom, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Giacinti Baschetti, Marco
    Bologna University.
    The influence of moisture content on the polymer structure of polyvinyl alcohol in dispersion barrier coatings and its effect on the mass transport of oxygen2017Inngår i: JCT Research, ISSN 1547-0091, E-ISSN 2168-8028, s. 1345-1355Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a study of the effect of moisture on the gas permeability of polyvinyl alcohol (PVOH) and PVOH–kaolin dispersion barrier coatings. The oxygen permeability was measured at different humidity levels, and the material properties were characterized under the same conditions: polymer crystallinity, kaolin concentration, and kaolin orientation were all evaluated. The experimental results revealed that the water plasticizes the PVOH material of the coatings, and the presence of kaolin filler is unable to affect such behavior significantly. The PVOH crystallinity was affected drastically by the humidity, as water melts polymer crystallites, which is a reversible process under removal of water. The permeability data were analyzed using a thermodynamicbased model able to account for the water effect on both the solubility of the gas and the diffusivity coefficients in the polymer and composite. The results showed good agreement between the model’s predictions and the experimental data in terms of the overall permeability of the material.

  • 286.
    Nyflött, Åsa
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Petkova-Olsson, Yana
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Bonnerup, Chris
    Stora Enso.
    Järnström, Lars
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Carlsson, Gunilla
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013), Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Minelli, Matteo
    Bologna University.
    Modelling of oxygen permeation through filled polymeric layers for barrier coatings2017Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 134, nr 20, artikkel-id 44834Artikkel i tidsskrift (Fagfellevurdert)
  • 287.
    Ogenvall, Mikael
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Solceller och elbilars påverkan på lokala elnätet2019Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Detta examensarbete har genomförts i samarbete med Arvika Teknik AB. Rapporten undersöker två bostadsområden i Arvika lokalnät, där syftet är att ge vägledning om framtidens energibehov för elbilar samt om solceller kan hjälpa till och minska effekttoppar. Rapporten visar på att lokalnät i vissa fall har stora effektutrymmen som kan användas till laddning av elbilar. Ytterligare visas att solceller endast kan ha en marginell inverkan på effekttoppar. Utmaningarna för nätbolagen innefattar många andra faktorer än de som berörs i denna rapport. Rapporten ger viss vägledning men mycket arbete återstår. Problem med elbilsladdning kommer inte komma de närmaste åren men på sikt kommer det vara viktigt att utveckla metoder att styra elbilsladdningen.

  • 288.
    Oka, T.
    et al.
    Tokyo Institute of Technology, Tokyo, Japan.
    Matsuura, D.
    Tokyo Institute of Technology, Tokyo, Japan.
    Sugahara, Y.
    Tokyo Institute of Technology, Tokyo, Japan.
    Solis, Jorge
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Lindborg, A. L.
    Camanio Care AB, Nacka, Sweden.
    Takeda, Y.
    Tokyo Institute of Technology, Tokyo, Japan.
    Chopstick-type gripper mechanism for meal-assistance robot capable of adapting to size and elasticity of foods2019Inngår i: Mechanisms and Machine Science, ISSN 2211-0984, E-ISSN 2211-0992, Vol. 66, s. 284-292Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposed a chopstick-type gripper for a meal-assistance robot, which is capable of adapting its shape and the contact force with the target food according to the size and the elasticity of the food. Solely using position control of the driving motor for the mechanism, this feature was enabled without relying on force sensors. The gripper was designed based on the concept of under-actuation and a planar mechanism with 2 DOF composed of a combination of 2 four-bar mechanisms having a torsion spring in a passive joint. To clarify the gripping motion and relationship among the contact force, food’s size and elasticity, a simulation based on kineto-elasto-static analysis was performed. Finally, to verify the theoretical analysis, a simple prototype was manufactured and an experiment to measure the contact force has been conducted.

  • 289.
    Opitz, Andreas
    et al.
    Humboldt Univ, Inst Phys, D-10099 Berlin, Germany.;Humboldt Univ, IRIS Adlershof, D-10099 Berlin, Germany..
    Wilke, Andreas
    Humboldt Univ, Inst Phys, D-10099 Berlin, Germany.;Humboldt Univ, IRIS Adlershof, D-10099 Berlin, Germany..
    Amsalem, Patrick
    Humboldt Univ, Inst Phys, D-10099 Berlin, Germany.;Humboldt Univ, IRIS Adlershof, D-10099 Berlin, Germany..
    Oehzelt, Martin
    Humboldt Univ, Inst Phys, D-10099 Berlin, Germany.;Humboldt Univ, IRIS Adlershof, D-10099 Berlin, Germany.;Helmholtz Zentrum Berlin Mat & Energie GmbH, Bereich Erneuerbare Energien, Berlin, Germany..
    Blum, Ralf-Peter
    Humboldt Univ, Inst Phys, D-10099 Berlin, Germany.;Humboldt Univ, IRIS Adlershof, D-10099 Berlin, Germany..
    Rabe, Juergen P.
    Humboldt Univ, Inst Phys, D-10099 Berlin, Germany.;Humboldt Univ, IRIS Adlershof, D-10099 Berlin, Germany..
    Mizokuro, Toshiko
    Natl Inst Adv Ind Sci & Technol, Osaka, Japan..
    Hoermann, Ulrich
    Univ Augsburg, Inst Phys, D-86159 Augsburg, Germany..
    Hansson, Rickard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Koch, Norbert
    Humboldt Univ, Inst Phys, D-10099 Berlin, Germany.;Humboldt Univ, IRIS Adlershof, D-10099 Berlin, Germany.;Helmholtz Zentrum Berlin Mat & Energie GmbH, Bereich Erneuerbare Energien, Berlin, Germany..
    Organic heterojunctions: Contact-induced molecular reorientation, interface states, and charge redistribution2016Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikkel-id 21291Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We reveal the rather complex interplay of contact-induced re-orientation and interfacial electronic structure-in the presence of Fermi-level pinning-at prototypical molecular heterojunctions comprising copper phthalocyanine (H16CuPc) and its perfluorinated analogue (F16CuPc), by employing ultraviolet photoelectron and X-ray absorption spectroscopy. For both layer sequences, we find that Fermi-level (E-F) pinning of the first layer on the conductive polymer substrate modifies the work function encountered by the second layer such that it also becomes E-F-pinned, however, at the interface towards the first molecular layer. This results in a charge transfer accompanied by a sheet charge density at the organic/organic interface. While molecules in the bulk of the films exhibit upright orientation, contact formation at the heterojunction results in an interfacial bilayer with lying and co-facial orientation. This interfacial layer is not EF-pinned, but provides for an additional density of states at the interface that is not present in the bulk. With reliable knowledge of the organic heterojunction's electronic structure we can explain the poor performance of these in photovoltaic cells as well as their valuable function as charge generation layer in electronic devices.

  • 290.
    Ouakad, Hassen M.
    et al.
    King Fahd University of Petroleum and Minerals, Saudi Arabia.
    El-Borgi, Sami
    Texas A&M University, Qatar.
    Mousavi, Mahmoud
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Friswell, Michael I.
    Swansea University, UK.
    Static and dynamic response of CNT nanobeam using nonlocal strain and velocity gradient theory2018Inngår i: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 62, s. 207-222Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper examines the length-scale effect on the nonlinear response of an electrically actuated Carbon Nanotube (CNT) based nano-actuator using a nonlocal strain and velocity gradient (NSVG) theory. The nano-actuator is modeled within the framework of a doubly-clamped Euler–Bernoulli beam which accounts for the nonlinear von-Karman strain and the electric actuating forcing. The NSVG theory includes three length-scale parameters which describe two completely different size-dependent phenomena, namely, the inter-atomic long-range force and the nano-structure deformation mechanisms. Hamilton's principle is employed to obtain the equation of motion of the nonlinear nanobeam in addition to its respective classical and non-classical boundary conditions. The differential quadrature method (DQM) is used to discretize the governing equations. The key aim of this research is to numerically investigate the influence of the nonlocal parameter and the strain and velocity gradient parameters on the nonlinear structural behavior of the carbon nanotube based nanobeam. It is found that these three length-scale parameters can largely impact the performance of the CNT based nano-actuator and qualitatively alter its resultant response. The main goal of this investigation is to understand the highly nonlinear response of these miniature structures to improve their overall performance.

  • 291.
    Pacho, Aleo Paolo
    et al.
    Karlstads universitet.
    Petrelius, Beppe
    Karlstads universitet.
    Rinio, Markus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Quantifying the impact of grain boundaries on standard and high performance mc-silicon solar cells2018Inngår i: Proc. 35th European Photovoltaic Solar Energy Conference, Brussels, EU PVSEC , 2018, s. 535-538Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Crystal defects such as grain boundaries affect the overall performance of a solar cell. The light beam induced current method allows for the localized quantification of the impact on the internal quantum efficiency of such defects. This work presents a method to estimate the separate impact of grain boundaries on the internal quantum efficiency (IQE) of multicrystalline silicon solar cells by correlating LBIC topographs with optical images of etched samples. Segmenting the impact of the grain boundaries on the IQE against those of other defects in our samples showed that the grain boundaries remain the most detrimental. The average IQE at 826 nm was reduced by up to 1.29 % (vs 0.25 % for other defects) absolute for standard multicrystalline and up to 1.15 % (vs 0.28 % for other defects) absolute for high performance multicrystalline silicon.

  • 292.
    Pluto, Malin
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Tank Shell Design According to Eurocodes and Evaluation of Calculation Methods2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Tanks are storage vessels for liquids. They can have different appearances; some are short and wide, others are tall and slim, some are small, others are large. In this thesis a tank of 6 m in both diameter and height has been used to obtain numerical results of the stresses in the tank. Tanks are most often thin-walled with stepwise variable shell thickness with thicker wall sections at the bottom of the tank and thinner at the top. Since they are thin-walled they are susceptible to buckling and there are conditions the shell construction must meet. The conditions that has to be met are determined by the laws and regulations that govern tank design. The National Board of Housing, Building and Planning (Boverket) is the new Swedish authority for rules of tank design and the Eurocodes are the new family of standards that should be followed. Sweco Industry AB is the outsourcer of this thesis and wants to clarify what rules that apply now when the Eurocodes are to be followed. The thesis project has produced a calculation document in Mathcad for tank shell design according to the Eurocodes with stress calculations according to membrane theory and linear elastic shell analysis. This thesis has also produced a comparison of stresses calculated using membrane theory, linear elastic shell analysis and finite element method (FEM). The comparison has been made for numerical results given for an arbitrarily designed tank wall. The loads acting on the tank included in the description were self-weight, internal and hydrostatic pressure as well as wind and snow loads. The loads were described in accordance with the Eurocodes. Some assumptions had to be made where the standard was vague or deficient in order to make calculations by hand possible. For example, the wind load had to be described as an axisymmetrically distributed load rather than an angularly varying. The stresses in the tank wall were calculated through creating free-body diagrams and declaring equations for force and moment equilibrium. The loads and boundary conditions were set in a corresponding manner in the FEM software Ansys as in the calculation document in order to obtain comparable results. When compared, the stress results calculated with membrane theory and FEM were quite similar while the stresses calculated with linear analysis were a lot larger. The bending moments were assumed to be too large which make the results of the linear analysis dominated by the moments. The arbitrarily dimensions set for the tank did thus not fullfill the conditions when linear analysis was used but did so for membrane theory and FE-analysis. Since the results calculated with membrane theory were very close to FEM in most cases, even without expressions for local buckling, it was assumed to be an adequate method in this application. Expressions for local buckling are although needed for the meridional normal stress. The conclusions of the results obtained are that membrane theory is a simple and adequate method in most cases. Linear analysis thus becomes redundant since it is more complicated and more easily leads to faulty results. Furthermore it cannot be used for higher consequence classes than membrane theory. FEM, with a computer software such as Ansys, is although the most usable calculation method since it can conduct more complicated calculations and is allowed to be used for all consequence classes.

  • 293.
    Qvick, Axel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Produktutveckling av transportlösning för interntransport av kompressorer: Koncept generering, evaluering, design och prototyptillverkning2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Detta examensarbete behandlar produktutvecklingen av en ny transportlösning för interntransport av kompressorer, vid Volvo Cars motortillverkning i Skövde. Dagenstransportlösning består av plasttråg som är svårhanterliga för monteringspersonal och har en låg transportkapacitet. En framtida planerad volymsökning i produktionen ställer krav på logistikeffektivisering relaterat till denna transport. Därför vill Volvo Cars ta fram en transportlösning som har högre kapacitet och samtidigt ha fokus på bättre ergonomi och effektivitet i monteringslinan.

    Examensarbetet omfattar produktutvecklingsprocessen från identifiering av kundbehov till prototyptillverkning. Kundbehoven identifierades genom intervjuer med berörd personal och observationer av dagens arbetssätt. Utifrån de identifierade kundehoven sammanställdes en kravspecifikation. Ett antal nya koncept genererades med hjälp av kreativa metoder. Koncepten utvärderades sedan genom en evalueringsmatris där koncepten jämförs mot varandra utifrån hur väl de uppfyller kundbehoven.

    Ett slutgiltigt koncept togs sedan vidare i den detaljerade designfasen för att modelleras i CAD. Ritningar togs fram för att konstruera en funktionell prototyp som sedan utvärderades i produktionen.

    Det nya konceptet består av en lastbärare med 3 lager med 8 kompressorer per lager. Kompressorerna lastas på uppfällbara hyllplan som möjliggör åtkomst med traverslyft ovanifrån. Den nya designen ger en 3 gånger så hög kapacitet, samt effektivare hantering vid transport och monteringslina genom en halvering av frekvensen för manuell emballagehantering. Även ergonomin har förbättrats då den manuella hanteringen av emballagen i monteringen och av truckförare minimerats.

  • 294.
    Rombo, Oskar
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Software Benchmark and Material Selection in an Exhaust Manifold: Thermo-mechanical fatigue simulation of an exhaust manifold in AVL Fire M2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Today, there is a great focus on downsizing the engines, this means that the engines are made smaller in size but retain the same power. This in combination with the drive to increase the power of the engines has led to the engine components being exposed to high thermal loads. Today’s engines also use very high cylinder pressure. The high thermal loads in combination with the high cylinder pressure have led to that the engine components are often very close to their material limits, so close that damage is common. This places high requirements on the materials, which makes the material selection a critical part of the engineering process.The main focus in this thesis work has been to develop and investigate a FEM model that can be used to quickly evaluate materials in an exhaust manifold that is exposed to thermo-mechanical fatigue (TMF). The model was then used to verify a material selection made for an existing exhaust manifold. One of AVL’s own software programs has also been evaluated, to see if it is a viable alternative to ABAQUS when preforming TMF simulations.The material selection made in this master thesis had the restriction that the exhaust manifold should not fail due to low cycle fatigue (LCF) when exposed to TMF. The goal has been to minimize the mass of the exhaust manifold by selecting a strong material with low density. The reason for this is because today there is a big focus on energy efficient cars with low emission levels. The simplest way to achieve this is to minimize the mass of the vehicle.The simulations conducted in this work has been performed in two different software’s, ABAQUS and AVL Fire M. In AVL Fire M flow simulations and steady-state heat transfer simulations have been performed. In ABAQUS, steady-state and transient heat transfer simulations and stress-strain simulations have been performed.The material selection process showed that Inconel 601 is the most suitable material for an exhaust manifold exposed to TMF. The simulations using Inconel 601 showed that this material will not fail due to LCF.The FEM model that was developed in this thesis was a lot faster compared to the existing TMF model used at AVL.CPU time for the existing model: 14 days 13 hours 14 minutes and 30 seconds (Core time).CPU time for the model developed in this thesis: 1 day 6 hours 37 minutes and 49 seconds (Core time).Two alternative models have been proposed for TMF simulations, one that uses the model developed in this thesis and one that is a combination of the existing model and the model developed in this work.

  • 295.
    Ruth, Therese
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Att göra det enklare att öppna plastpåsar: Ett produktutvecklingsprojekt på uppdrag av Binar Elektronik AB2013Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Rapporten behandlar ämnet att göra det enklare att öppna plastpåsar och görs på uppdrag av Leif Gustavsson vid Binar Elektronik AB i Trollhättan. Arbetetet utförs i kursen Examensarbete för högskoleingenjörsexamen i innovationsteknik och design, MSGC12 vid fakulteten för hälsa, natur- och teknikvetenskap på Karlstad universitet under våren 2013.

    Idag sker öppnandet av påsar ofta genom att ett tumme-pekfingergrepp skjuvar isär påsens väggar. Informationssökningen visar att behovet av en lösning som gör det enklare att öppna olika typer av plastpåsar i butik och inom hushåll är mycket stort för människor både med och utan funktionsnedsättning. Dels ur ett användningsperspektiv, då operationen kräver en hög motorisk förmåga men även ur ett smittspridningsperspektiv, då fingrarna ofta måste blötas med saliv för att åstadkomma tillräckligt hög friktion mot påsen för att skjuva upp den. Eftersom individen då får i sig de bakterier hon har på handen och för sina munhålebakterier vidare när hon tar i ett annat föremål. Även om ett fåtal patent påträffas inom området finns inga lösningar tillgängliga på marknaden för föreskrivna hjälpmedel eller för produkter inom egenansvar.

    Utifrån uppdragsgivarens krav, egna premisser, vad som observeras i butik och framkommit från intervjuer med butiksvan säljare, hygiensköterska, arbetsterapeut, utredare vid socialtjänsten samt vid samtal med Reumatikerförbundet har en produktspecifikation gjorts. Specifikationen ställer bland annat krav på användarvänlighet, att kunna brukas i butik och inom hushåll, att minimera smittspridning, att hjälpa funktionsnedsatta samt att tillåta storserietillverkning till låg kostnad.

    Konceptgenerering sker tillsammans med kurskamrater som är bekanta med den kreativa processens metodik och med reumatiker som är väl bekanta med behovet. Det leder till att ett trettiotal konceptuella lösningar tas fram som sedan utvärderas med hjälp av eliminerings-, relativ besluts- och kriterieviktsmatriser samt spindelvävsdiagram som bygger på den kravspecifikation som tidigare definierats.

    Den valda lösningen konfigureras och testas vid prototyptillverkning med återkoppling till den slutliga användaren, för att sedan få sin slutkonstruktion och mönsterskyddas. Lösningen är en produkt som orsakar skjuvning med sin osymmetriska u-form genom att armarna i sträcks i olika riktningar vid kompression samtidigt som dess gap är försett med friktionsmaterial som gör att påsens väggar skjuvas isär.

    Produktens enkla form gör det enklare att öppna plastpåsar samtidigt som den minimerar smittspridning och tillåter storserietillverkning till låg kostnad. Enkelheten gör det även möjligt att ge indirekt skydd av den tekniska funktionen genom mönsterskydd av form. Produktens material, tillverkning och dimension behöver dock specificeras noggrannare genom produkttest så att konstruktionen tillåter lämplig skjuvning för att kunna öppna en plastpåse.

  • 296.
    Rysz, Jakub
    et al.
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Josiek, Monika
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Marzec, Mateusz M.
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, 30–059 Krak.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Pattern Replication in Blends of Semiconducting and Insulating Polymers Casted by Horizontal Dipping2013Inngår i: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 51, nr 19, s. 1419-1426Artikkel i tidsskrift (Fagfellevurdert)
  • 297.
    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.

  • 298.
    Rönn, Pernilla
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Gud har bröd i molnen!: Kenyanska barns tankar och kunskaper om vatten2014Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Abstract

    The purpose of this study was to find out what ideas and knowledge Kenyan children have about water, what they know about the properties of water and its natural cycles and how they work on and with the water at the preschool. To get an idea of this, I have for two weeks participated in the activities of a preschool located in a rural community in Kenya. Observations of the water resources they have at the preschool and the extent to which children were playing with water has been made. Interviews with twelve children of five years and their teachers have been implemented. The study shows that these children´s assets to water are limited, they only did theoretical research on water. The study also shows that children have a great knowledge of which ones need water. When it comes to water use the kids said the way they use water in the home and in school that is only personal experience of water use. Children´s knowledge of water´s different physical evaporation, melting, freezing and evaporation were scarce. 68 % of the children had an initial awareness of the water cycle that is to say that they had an understanding of that rain water does not cease to exist when it hit the ground. Many of the children had a sense that God is behind much.

  • 299.
    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.

  • 300.
    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.

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