Experimentelle und theoretische Untersuchungen zu Inkompatibilitäts- und Versetzungsaufstauungsspannungen an Korngrenzen unter Berücksichtigung der elastischen und plastischen Anisotropie

Die mechanischen Eigenschaften von metallischen Materialien hängen stark vom Versetzungsverhalten ab, wie z.B. der Dichte, der Verteilung, der Nukleation und der Beweglichkeit von Versetzungen, sowie den Wechselwirkungen zwischen Versetzungen und Korngrenzen (KG). Das Hauptziel dieser Arbeit ist die Untersuchung der Auswirkungen von elastischen und plastischen Anisotropien auf die Versetzungs-KG Wechselwirkung unter Berücksichtigung der komplexen Eigenschaften von KG, sowie der Einflüsse der Misorientierung und der freien Oberflächen. Um dieses Ziel zu erreichen, wurde ein auf dem L-E-S-Formalismus basierender analytischer Ansatz verwendet, der die elastischen Felder einzelner gerader Versetzungen und unterschiedlicher Versetzungskonfigurationen an KG in anisotropen homogenen Medien, Halbräumen, Bi- und Tri-Materialien unter möglicher Berücksichtigung freier Oberflächeneffekte liefert. Die Tri-Material-Konfiguration erlaubt die Berücksichtigung einer KG mit der Dicke ungleich Null im Nanometerbereich und eines spezifischen Steifigkeitstensors für die KG. Die Konfiguration mit zwei freien Oberflächen wurde zur Untersuchung von Größeneffekten verwendet. Die Auswirkungen der anisotropen Elastizität, der kristallographischen Orientierung, der KG-Steifigkeit und der freien Oberflächen wurden für den Fall einer einzelnen Versetzung sowie für einen Versetzungsaufstau in einem Ni-Bikristall mit Bildkraft- bzw. Aufstaulängenanalysen untersucht. Parallel dazu wurden in-situ Mikrodruckversuche an Ni und α-Messung Bikristallen, welche durch FIB-Bearbeitung hergestellt wurden, kombiniert mit SEM, AFM und EBSD Untersuchungen durchgeführt. Die Druckversuche wurde mit einer geringen Dehnung durchgeführt, bis Gleitlinien beobachtet wurden oder die Fließspannung erreicht wurde. Dann wurden die räumlichen Variationen der Gleitstufenhöhe an den lokalisierten Gleitbändern, welche an der KG endeten, mittels AFM gemessen und die Verteilung der Burgers-Vektoren in dem Versetzungsaufstau bestimmt. Diese Versetzungsverteilung wurde dann mit den experimentell gemessenen Parametern simuliert, indem die Auswirkungen von Misorientierung, KG-Steifigkeit, freien Oberflächen, Inkompatibilitätsspannungen und kritischer Kraft berücksichtigt wurden. Insbesondere wurden die Inkompatibilitätsspannungen mit Hilfe von CPFEM-Simulationen analysiert und die Dicke der KG wurde mit atomistischen Simulationen mittels LAMMPS bestimmt.Les propriétés mécaniques des matériaux métalliques dépendent fortement du comportement des dislocations, telles que la densité, la distribution, la nucléation et la mobilité des dislocations ainsi que les interactions entre les dislocations et les joints de grain (JDGs). L'objectif principal de cette thèse est d'étudier les effets des anisotropies élastiques et plastiques sur l'interaction de dislocations-JDG en considérant les propriétés complexes des JDGs, les effets de désorientation et les effets de surfaces libres. Pour atteindre cet objectif, une approche analytique basée sur le formalisme L-E-S a été étudiée, qui fournit les champs élastiques des dislocations droites simples et des différents empilements de dislocations aux JDGs dans des milieux homogènes anisotropes, des demi-espaces, des bi- et tri-matériaux tout en considérant éventuellement les effets de surface libre. La configuration tri-matériaux permet d'envisager une épaisseur non nulle de l'ordre du nanomètre et un tenseur de rigidité spécifique pour la région du JDG. La configuration à deux surfaces libres a été utilisée pour étudier les effets de taille. Les effets de l'élasticité anisotrope, de l'orientation cristallographique, de la rigidité du JDG et des surfaces libres ont été étudiés dans le cas d'une seule dislocation et des empilements de dislocations dans un bi-cristal de Ni avec l'analyse des forces images et de la longueur d'empilements, respectivement. En parallèle, des essais in-situ de compression sur des bi-cristaux de Ni et de α-laiton de taille micronique réalisés par usinage au FIB et des observations couplant MEB, AFM et EBSD ont été effectués. L'essai de compression a été réalisé avec une faible déformation jusqu'à ce que les lignes de glissement soient observées ou que la limite d'élasticité soit atteinte. Ensuite, les variations spatiales de la hauteur des marches dûs aux bandes de glissement localisées se terminant au JDG ont été mesurées par AFM pour déterminer la distribution du vecteur de Burgers dans l'empilement de dislocations. Cette distribution a ensuite été simulée par la configuration de l'empilement de dislocations dans des bi-cristaux avec les paramètres mesurés expérimentalement en considérant l'effet de la désorientation, de la rigidité du JDG, des surfaces libres, des contraintes d'incompatibilités et de la force critique. En particulier, les contraintes d'incompatibilités ont été analysées à l'aide de simulations CP-MEF et l'épaisseur du JDG a été simulée à l'aide de simulations atomistique avec LAMMPS.The mechanical properties of metallic materials strongly depend on the dislocation behavior, such as the density, the distribution, the nucleation and the mobility of dislocations as well as the interactions between dislocations and grain boundaries (GB). The main objective of this thesis is to study the effects of elastic and plastic anisotropies on the dislocation-GB interaction considering complex properties of GBs, misorientation effects and free surfaces effects. To reach this objective, an analytical approach based on the L-E-S formalism was investigated, which provides the elastic fields of single straight dislocations and different dislocation pile-ups at GBs in anisotropic homogeneous media, half-spaces, bi- and tri-materials while possibly considering free surface effects. The tri-material configuration allows considering a non-zero thickness in the nanometer range and a specific stiffness tensor for the GB region. The configuration with two free surfaces was used to study size effects. The effects of anisotropic elasticity, crystallographic orientation, GB stiffness and free surfaces were studied in the case of a single dislocation and dislocation pile-ups in a Ni bi-crystals with image forces and pile-ups length analyses, respectively. In parallel, in-situ compression tests on micron-sized Ni and α-Brass bi-crystals produced from FIB machining and observations coupling SEM, AFM and EBSD were performed. The compression test was performed with a low strain until slip lines were observed or yield stress was reached. Then, step height spatial variations due to localized slip bands terminating at GB were measured by AFM to determine the Burgers vector distribution in the dislocation pile-up. This distribution was then simulated by dislocation pile-up configuration in bi-crystals with the experimentally measured parameters by considering the effect of misorientation, GB stiffness, free surfaces, incompatibility stresses and critical force. In particular, the incompatibility stresses were analyzed using CPFEM simulations and the thickness of GB was simulated using atomistic simulations with LAMMPS.French Ministry of Higher Education and Scientific Research, French-German University (UFA-DFH), Experimental Methodology in Materials Science (MWW) in Saarland University, French State (ANR) through the program “Investment in the future” (LabEx “DAMAS” referenced as ANR-11-LABX-0008-01), Deutsche Forschungsgemeinschaft DFG for the financing of the AFM microscope, Grant No. INST 256/455-1 FUG

The Optimization of Interconnection Networks in FPGAs

Scaling technology enables even higher degree of integration for FPGAs, but also brings new challenges that need to be addressed from both the architecture and the design tools side. Optimization of FPGA interconnection network is essential, given that interconnects dominate logic. Two approaches are presented, with one based on the time-multiplexing of wires and the other using hierarchical interconnects of high-speed serial links and switches. Design tools for both approaches are discussed. Preliminary experiments and prototypes are presented, and show positive results

Static analysis of dynamic servo tool rest considering the influence of precision error

The analysis of the reliability of dynamic servo tool rest using traditional methods is inaccurate because the influences of the accuracy of gear machining and assembly are not considered. In this study, a static analysis method for dynamic servo tool rest is conducted considering the influence of accuracy error. Firstly, the working principle of tool rest is analysed, and its working process is divided into two actions, namely, initial positioning and locking. Secondly, the error sources of dynamic servo tool rest are investigated, and the transmission angle error is divided into two kinds, namely, assembly error of shafting and machining error of gear. The static analysis of tool rest is performed by considering the influence of the transmission error of the tool rest. Results show that the assembly, machining and locking forces of the fixed tooth disc of the dynamic servo tool rest have important effects

Cross-cultural L2 learning exchange: A qualitative examination of strategies, tools, cognition and translation outcomes

Amidst the milieu of free and at-cost L2 language software applications coming into existence for use on mobile devices and computers, adult L2 learners are faced with the challenge of selecting their best choice for them to use in acquiring a specific second language. Their selection is based on their individual need and the context in which they plan to use the second language. More importantly, it is well known there is no single tool, resource, or strategy that adult L2 learners can use to fully acquire a second language quickly and effectively, especially for intercultural couples who lack a common language for daily communication. While there is much literature on the topic of L2 acquisition and learning, the purpose of this auto-ethnographic study is to share with readers specific aspects of our journey in acquiring each other’s native language throughout their first year together. Included are subsequent findings involving cognition and translation issues as developing skills recognized during various phases of L2 acquisition

Some remarks about deformation theory and formality conjecture

Using the algebraic criterion proved by Bandiera, Manetti and Meazzini, we show the formality conjecture for universally gluable objects with linearly reductive automorphism groups in the bounded derived category of a K3 surface. As an application, we prove the formality conjecture for polystable objects in the Kuznetsov components of Gushel--Mukai threefolds and quartic double solids.Comment: 15 pages, to appear in Annali dell'Universit\`a di Ferrara, special volume Edge Days: 2018-202

TIME-MULTIPLEXED INTERCONNECTION NETWORK FOR FIELD-PROGRAMMABLE GATE ARRAYS

Ph.DDOCTOR OF PHILOSOPH

Business plan for language and tourism academy: Language immersion trips

En España, la enseñanza del chino es un campo emergente, mientras que en China, antes de la pandemia, cada vez más chinos querían viajar y estudiar en España, y España se ha convertido en el destino preferido de la clase media china para invertir y viajar al extranjero. En la era post-pandemia, el número de estudiantes internacionales sigue manteniendo un pequeño aumento y el turismo vuelve poco a poco a su apogeo antes de la pandemia. En este contexto, se ha surgido la idea de crear una empresa que combine la enseñanza de idiomas y los servicios turísticos, y en este trabajo se desarrollará un plan de negocio para la empresa, se analizarán todos los aspectos necesarios para lograr dicho plan y, finalmente, se concluirá sobre la viabilidad de la empresa

On grain boundary migration of a high-angle-grain boundary – Effect of shear stress and energy jump-driving force in micro-bicrystals

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Atomic Force Microscopy Study of Discrete Dislocation Pile-ups at Grain Boundaries in Bi-Crystalline Micro-Pillars

Compression tests at low strains were performed to theoretically analyze the effects of anisotropic elasticity, misorientation, grain boundary (GB) stiffness, interfacial dislocations, free surfaces, and critical force on dislocation pile-ups in micro-sized Face-Centered Cubic (FCC) Nickel (Ni) and α -Brass bi-crystals. The spatial variations of slip heights due to localized slip bands terminating at GB were measured by Atomic Force Microscopy (AFM) to determine the Burgers vector distributions in the dislocation pile-ups. These distributions were then simulated by discrete pile-up micromechanical calculations in anisotropic bi-crystals consistent with the experimentally measured material parameters. The computations were based on the image decomposition method considering the effects of interphase GB and free surfaces in multilayered materials. For Ni and α -Brass, it was found that the best predicted step height spatial profiles were obtained considering anisotropic elasticity, free surface effects, a homogeneous external stress and a certain critical force in the material to equilibrate the dislocation pile-ups

Association of methylenetetrahytrofolate reductase (MTHFR) C677T and A1298C polymorphisms with the susceptibility of childhood acute lymphoblastic leukaemia (ALL) in Chinese population

BACKGROUND: The aim of this study was to investigate the relationship between the polymorphisms of the methylenetetrahytrofolate reductase (MTHFR) gene and susceptibility to childhood acute lymphoblastic leukemia (ALL). METHODS: A case–control study was conducted among 98 children with ALL and 93 age- and sex- matched non-ALL controls. Genotyping of MTHFR C677T and A1298C polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The odds ratios (ORs) of MTHFR genotypes were used to assess the associations of these polymorphisms with childhood ALL susceptibility. RESULTS: No significant differences were observed for frequencies of the 677CC, 677CT and 677TT genotypes between patients and controls. Frequencies of the 1298AA, 1298 AC and 1298CC genotypes between the two groups were significantly different. The risk of ALL with the 1298C allele carriers (AC + CC) was elevated by 1.1 times compared with the AA genotype [OR = 2.100; 95% CI (1.149; 3.837); P = 0.015]. CONCLUSIONS: The MTHFR A1298C polymorphism is associated with susceptibility to childhood ALL in the Chinese population