Search for dissertations about: "material imperfections"

Showing result 21 - 25 of 43 swedish dissertations containing the words material imperfections.

2. 21. Rolling Contact Fatigue of Railway Rails with Emphasis on Crack Initiation

   Author : Jonas Ringsberg; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; variable amplitude; crack closure; rolling contact fatigue; crack propagation; railway rails; damage accumulation; critical plane approach; crack initiation; plasticity; multiaxial fatigue;

   Abstract : Increased traffic density and the heavier axle loads of modern trains have led to severe problems with rolling contact fatigue (RCF) which cause initiation of surface cracks in railheads. In this thesis, a specific type of surface crack, the head check, is studied numerically with emphasis on fatigue crack initiation. READ MORE

4. 22. Rotordynamic Analysis with Special Reference to Composite Rotors and Internal Damping

   Author : Håkan Wettergren; Jörgen W. Lund; Linköpings universitet; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY;

   Abstract : The present doctoral thesis is concerned with three different rotordynarnic applications; composite rotors, internal damping and microslip in a turbine generator. When a composite shaft has an imperfection, such as differences in the filament winding angle, the eigenfrequencies of the non-rotating shaft depend only on the material stiffness. READ MORE

5. 23. On hydrogen point defects in perovskite oxides

   Author : Erik Jedvik Granhed; Chalmers tekniska högskola; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; density functional theory; oxyhydride; phonon; point defects; chemical expansion; polaron; BaZrO3; proton conductor; BaTiO3;

   Abstract : Oxides based on the perovskite structure exhibit a surprisingly large diversity in materials properties and are found in many different applications, several related to clean energy technologies, such as solar cells, batteries and fuel cells. Many properties in materials are the result of lattice imperfections, commonly denoted \emph{defects}, and much effort is devoted to fine tuning materials properties through controlling the defects therein. READ MORE

6. 24. Five essays on forest raw materials use in an international perspective

   Author : Mats Nilsson; Luleå tekniska universitet; []
   Keywords : SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; Economics; Nationalekonomi;

   Abstract : This dissertation consists of an introduction and five self-contained studies analyzing different aspects of roundwood markets. Geographically it is focused on Sweden (paper 1-3) and Russia (paper 4-5). Four of the papers (1-2, 4-5) are explicitly considering international trade and its effects and possibilities in the domestic markets. READ MORE

7. 25. Between square and circle : A study on the behaviour of polygonal steel profiles under compression

   Author : Panagiotis Manoleas; Ove Lagerqvist; Efthymios Koltsakis; Leroy Gardner; Luleå tekniska universitet; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; polygonal; RCPS; plate buckling; shell buckling; towers; transmission lines; wind turbines; high strength steel; Stålbyggnad; Steel Structures;

   Abstract : The present study explores the structural properties of regular convex polygonal cross section (RCPS). Such profiles are commonly used to construct masts and towers, e.g.  transmission towers, light poles etc. READ MORE