Sökning: "Defekter"

Visar resultat 1 - 5 av 116 avhandlingar innehållade ordet Defekter.

  1. 1. On the influence of imperfections on microstructure and properties of recycled Al-Si casting alloys

    Författare :Anton Bjurenstedt; Salem Seifeddine; Anders E.W. Jarfors; Arne Dahle; Johan Moverare; Jönköping University; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Imperfections; Recycled Al-Si alloys; Fe-rich intermetallics; Melt quality; Fractography; Defekter; Återvunna Al-Si legeringar; Fe-rika intermetaller; Smältakvalité; Fraktografi;

    Sammanfattning : There are great energy savings to be made by recycling aluminium; as little as 5% of the energy needed for primary aluminium production may be required. Striving to produce high quality aluminium castings requires knowledge of microstructural imperfections, which is extra important when casting recycled aluminium that generally contains higher levels of imperfections compared to primary aluminium. LÄS MER

  3. 2. Ultrasonic testing of components produced with additive manufacturing : Towards improved detection and classification of defects

    Författare :Mikael Sahl; Håkan Wirdelius; Erik Lindgren; Oskar Tofeldt; Madis Ratassepp; Högskolan Väst; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Non-Destructive Testing NDT ; Super alloys; Microstructure; Ultrasonic Testing UT ; Productivity Enhancement; Production Technology; Produktionsteknik;

    Sammanfattning : The focus in this work is on the use of ultrasonic testing as a method for inspecting components manufactured through additive manufacturing (AM) processes. The research is rooted in the need for effective non-destructive testingtechniques that can adapt to the unique challenges posed by AM-produced materials, including complex defect geometries and surface conditions. LÄS MER

  4. 3. Carrier dynamics in blue and green InGaN LED structures

    Författare :Rinat Yapparov; Saulius Marcinkevičius; Ulrich Theodor Schwarz; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; InGaN quantum wells; interwell transport; near-field scanning optical microscopy; internal quantum efficiency; V-defects; InGaN-kvantbrunnar; transport mellan brunnar; optisk mikroskopi med närafältsskanning; intern kvanteffektivitet; V-defekter; Physics; Fysik; Optics and Photonics; Optik och fotonik;

    Sammanfattning : This thesis focuses on effects that are critical to achieving high internal quantum efficiency (IQE) in GaN-based light-emitting diodes (LEDs) that emit in a broad spectral range, from violet to green-yellow. These effects include interwell carrier transport in multiple quantum well (QW) structures, lateral transport in the QW plane, and radiative and nonradiative recombination. LÄS MER

  5. 4. Defects in E-PBF Ti-6Al-4V and their Effect on Fatigue Behaviour : Characteristics, Distribution and Impact on Life

    Författare :Viktor Sandell; Marta-Lena Antti; Pia Åkerfeldt; Thomas Hansson; Hans Andersson; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Defects; Additive Manufacturing; Ti-6Al-4V; Probabilistic Modelling; Fatigue; Materialteknik; Engineering Materials;

    Sammanfattning : Layer by layer manufacturing (additive manufacturing, AM) of metals is emerging as an alternative to conventional subtractive manufacturing with the goal of enabling near net-shape production of complex part geometries with reduced material waste and shorter lead times. Recently this field has experienced rapid growth through industrial adaptation but has simultaneously encountered challenges. LÄS MER

  7. 5. Insights into Materials Properties from Ab Initio Theory : Diffusion, Adsorption, Catalysis & Structure

    Författare :Andreas Blomqvist; Rajeev Ahuja; Christopher Wolverton; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Density functional theory; Molecular dynamics; Diffusion; Catalysis; Adsorption; Random structure search; Hydrogen-storage materials; Phase-change materials; Defects and diffusion; Defekter och diffusion; Surfaces and interfaces; Ytor och mellanytor; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

    Sammanfattning : In this thesis, density functional theory (DFT) calculations and DFT based ab initio molecular dynamics simulations have been employed in order to gain insights into materials properties like diffusion, adsorption, catalysis, and structure. In transition metals, absorbed hydrogen atoms self-trap due to localization of metal d-electrons. LÄS MER