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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Crystallographic characterization of deformation twinning in commercially pure Titanium / Caractérisation cristallographique des macles de déformation dans le titane de pureté commerciale

Wang, Shiying 29 August 2014 (has links)
Le titane et ses alliages sont devenus des matériaux incontournables dans l'aéronautique, le domaine biomédical et l'industrie chimique et ce depuis le début des années 1950 en raison de haut rapport résistance/poids, une excellente biocompatibilité et une bonne résistance à la corrosion. La structure hexagonale du titane conduit à une anisotropie intrinsèque, due à la configuration atomique particulière et à une anisotropie extrinsèque, due à une texture marquée produite lors de leur élaboration. Le but de cette étude est d'améliorer la compréhension des mécanismes de déformation (glissement et maclage) dans le titane conduisant à cette anisotropie extrinsèque. Une technique d’essais interrompus in situ en MEB / EBSD a été utilisée lors la déformation plastique d’un alliage de titane T40 commercialement pur afin de suivre l'évolution de l'orientation cristalline et de la morphologie des grains au cours de la déformation sous différents types de chargement (traction, laminage, cisaillement). Cette technique permet de suivre l’apparition du maclage, la croissance et la forme des macles, l’interaction des variants de macles avec les grains voisins. Le Facteur de Schmid, l’orientation cristallographique, l'énergie de déformation plastique, et la déformation localisée liée à l’accommodation ont été calculés pour analyser l'activation du maclage, la croissance des macles, et la sélection de variant de macle. Des variants de macles avec un faible facteur Schmid, facteur qui exprime la force appliquée externe sur le plan de maclage et le long de la direction de maclage, ont été observés. Cela indique le facteur Schmid n'est pas très approprié pour prédire le maclage. Une règle de sélection de variant de maclage a été proposée sur la base de la consommation maximale d'énergie plastique. L'énergie plastique (on suppose le matériau comme étant rigide parfaitement plastique) consommée est calculée de la façon suivante : la déformation que produit chaque variant est exprimée du repère cristal au repère macroscopique ; la contrainte suit une loi de type Hall Petch, le diamètre des grains est alors défini comme la longueur maximale que peut prendre chaque variant dans le grain. Le variant qui consomme le plus d’énergie est activé le premier. Ces calculs sont en bon accord avec l'observation expérimentale : Les variants de macles sélectionnés étaient ceux conduisant à une consommation maximale de l'énergie plastique. Le libre parcours que peut prendre chaque variant est un critère pertinent puisque cela permet d’expliquer les différences observées dans un grain équiaxe ou un grain allongé en terme de nombre de variants présents et croissance des macles. Les essais interrompus in – situ montrent des chaines de macles ou paires de macles (propagation dans 2 ou plusieurs grains voisins). Une macle est activée en premier dans un grain, avec sa croissance, elle impose un champ de contrainte et un champ de déformation dans les grains voisins ce qui peut activer une macle dans les grains voisins. Les paires de macles ont un paramètre de Luster - Morris relativement élevé, ce qui traduit une bonne compatibilité entre les macles et une propagation facile de macle dans les grains voisins. Par une simple transformation du tenseur gradient de déplacement du variant utilisé dans le grain considéré on obtient la déformation imposée dans le grain voisin. Le variant de macle dans ce grain voisin pouvant accommoder le plus facilement la déformation imposée sera activé. Ceci montre que la déformation locale peut influencer l’activation et la sélection de variant de macle / Titanium and its alloys have become backbone materials for aerospace, biomedical field and chemical industries since the early 1950s because of the high strength-weight ratio, excellent biocompatibility, and good corrosion resistance. The hexagonal structure of titanium leads to an intrinsic anisotropy of the particular atomic configuration and extrinsic anisotropy of the texture to a product marked in their elaboration. The purpose of this study is to improve understanding of the deformation mechanisms (slip and twinning) in the titanium leading to the extrinsic anisotropy. Technical testing interrupted in situ SEM / EBSD was used in the plastic deformation of a commercially pure titanium alloy T40 to follow the crystal orientation and morphology of the grains during deformation under different types of loading (tension, rolling). This technique allows following the occurrence of twinning, growth and shape of the twins, the interaction of the twin variants with neighboring grains. Schmid factor, crystallographic orientation, plastic deformation energy, and localized strain accommodation were calculated to analyze the twin activation, the twin growth, and twin variant selection. Twinning variant with relatively low global Schmid factor, which resolves the externally applied force onto the twinning plane and along the twinning direction, were observed. That indicates the global Schmid factor is not very appropriate to predict twinning. A twinning variant selection rule was proposed based on the maximum plastic energy consumption. The plastic energy ( the material is assumed to be perfectly rigid plastic) consumed is calculated as follows: the deformation produced by each variant is expressed from crystal frame to macro frame; stress follows a Hall Petch type rule, the grain diameter is then defined as the maximum length that can take each variant in the grain. The variant which can consume the maximum of the externally imposed energy is expected to twin first. The calculation results show good agreement with the experimental observation: The selected twin variants were the one leading to maximum plastic energy consumption. The variant free path length relevant criterion so indicates the reason why the equiaxed grains and elongated grains have the difference in twin variant number and twinning variant growth. The interrupted in-situ investigation shows that the twin chains or twin pairs observed in this work are a sequential twinning behavior. A twin activated first, with its growth, it imposes a strain field and a stress field into its neighboring grains and possibly stimulate a twin in the neighboring grain. The twin pairs show a good alignment with a relatively high Luster-Morris parameter, which is a measure of the compatibility of twinning systems through a grain boundary. By the displacement gradient tensor transformation, the imposed strain into the neighboring grain was obtained. The twinning variant which can better accommodate the imposed strain can be activated. It indicates that the local strain can influence the twinning activation and variant selection
52

Product Development and Finite Element Analysis of Polyurethane Press Shoe : Produktutveckling och finit element analys av press-sko i polyuretan

Bergström, Mikael January 2021 (has links)
The press-section of a paper machine holds several different types of press rolls. One of the many press roll variants is the Valmet produced press roll, ViscoNip. This press roll utilizes an extended nip in order to increase the amount of water removed. The extended press nip in ViscoNip is special since it is controllable by a pressurized polyurethane press shoe. The press shoe runs through the body of the press roll. Due to limits of the current production process, new manufacturing methods and construction solutions are needed. In cooperation with another thesis, the current design and manufacturing process was reviewed and a plan intended to improve the current solution was formulated. The plan was to, by working together in a project, perform a product development process intended to create concepts able to utilize new methods of manufacturing. By using established methods of concept generation, such as Brainwriting 6-3-5, 11 concepts were created. Some of these concepts involved a redesign of the press shoe, leading to a need for construction and performance analysis. With the other thesis focusing on researching new possible and available manufacturing solutions. The work of this thesis fully committed to the structural and mechanical performance evaluation of the new concepts. This was performed by creating a model of the technical application using Finite Element Modelling in ABAQUS. The model included a hyperelastic material model for the polyurethane material as well as cohesive zone modelling to account for partitioning of the part. The model was then used to simulate the different concepts as they were subjected to a challenging load case. The results of which were used as the basis for structural and performance analysis. The analysis showed proof of sufficient structural stability and mechanical performance for all evaluated concepts. Then, in cooperation with the other thesis, a final concept choice was made. All in all, three different redesigned concepts were deemed as having potential for further development. The current solution was also deemed as having potential for future development but only when new manufacturing methods or techniques were considered.
53

Teplovodná deska s řízeným teplotním polem / Thermal conductive plate with controlled thermal field

Masár, Pavol January 2010 (has links)
This work deals with design of thermal source of panel shape for scientific biological application. Panel has adjustable surface temperature and thermal gradient. The first part of this work concern with design and numerical modeling of the thermal system, application of materials and arrangement of thermal and cooling devices – Peltier elements. Second part of this work is about construction of the panel and experimental measurement.
54

Vliv modifikace na pevnost lepení buku

Šmíd, Pavel January 2019 (has links)
This diploma thesis is focused on the influence of thermal modification on the strength of bonded joint in tension according to ČSN EN 205. For the purpose of this work was used beech wood. The thermal modification of the test samples was performed at temperatures of 160 °C, 180 °C and 200 °C. The selected bond strength adhesives were melamine-urea formaldehyde adhesives (MUF), phenol-resorcinol formaldehyde adhesives (PRF) and one-component polyurethane adhesives (PUR). In addition to the thermal modification the effect of plasma modification on bond strength is also determined. The test lamellas were plasma treated (DCSBD) prior to gluing and pressing. The result is the determination of the tensile strength of the bonded joint in all the above-mentioned modifications and comparation of the results.
55

Attention et vulnérabilité dans Le pur et l'impur de Colette : la perspective du care

Champagne, Jeremy 08 1900 (has links)
Ce mémoire mobilise les notions et le vocabulaire propres aux éthiques du care pour tenter de mesurer la place qu’occupe l’attention aux vulnérabilités d’autrui dans Le Pur et l’impur (1932) de Colette, autant dans l’ordre de ses représentations que sur le plan du geste d’écriture envisagé comme une prise de parole collective de la part d’une communauté de la mélancolie. Après une brève contextualisation théorique, nous mettons les notions d’attention et de vulnérabilité à l’épreuve du texte en analysant les rapports entre la narratrice et certains de ses personnages – notamment de Charlotte, dont les confidences viennent créer, dès l’abord du texte, une dynamique de la voix et du silence qui rappelle le modèle de l’épistémologie du care. L’analyse des aspects éthiques du geste d’écriture révèle quant à elle un art à la fois éthique et politique de l’attention, fondé sur une écriture dont les aspects interventionnistes permettent de mettre en lumière l’expérience de personnages marginaux ou subalternes. / This thesis mobilizes both the notions and vocabulary associated with the ethics of care to uncover the roles played by attention to the others’ vulnerabilities in Colette’s Le Pur et l’impur (1932), and the way it manifests as both a representation within the text as well as a component of the act of writing itself, which takes the form of a community of melancholy’s collective act of “speaking out”. After a brief theoretical contextualization, the notions of “attention” and “vulnerability” are analyzed within the context of the narrator’s relationship with her own characters, and most notably with Charlotte, whose confidences come to create, from the outset of the text, a dynamic of voice and silence that is also characteristic of the epistemology of care. In the end, through analysis of the ethical aspects of the act of writing, we come to find that attention itself is both an ethical and a political act within a narrative that seeks to shed light on marginalized and subaltern communities.
56

Further development of manufacturing method for polyurethane shoe press / Vidareutveckling av tillverkningsmetod för skopress i polyuretan

Berg, Jonathan January 2021 (has links)
The press-section of a paper machine holds several different types of press rolls. One of the many press roll variants is the Valmet produced press roll, ViscoNip. This press roll utilizes an extended nip in order to increase the amount of water removed. The extended press nip in ViscoNip is special since it is controllable by a pressurized polyurethane press shoe. The press shoe runs through the body of the press roll. Due to the limits of the current production process, new manufacturing methods and construction solutions are needed. In cooperation with another thesis, the current design and manufacturing process was reviewed and a plan intended to improve the current solution was formulated. The plan was to, by working together in a project, perform a product development process intended to create concepts able to utilize new methods of manufacturing. By using established methods of concept generation, such as Brainwriting 6-3-5, 11 concepts were created. Some of these concepts involved a redesign of the press shoe, leading to a need for construction and performance analysis. The other thesis focusing on the structural and mechanical performance evaluation of the new concepts. The work of this thesis focusing on researching new possible and available manufacturing solutions. The new concepts were analyzed with new and possible manufacturing methods to fulfill all the requirements. With all data, a document was created and market research was made to get feedback from more knowledgeable in the subject. Moreover, sequence analysis between the concepts with the current and those new manufacturing methods was made to further explain which manufacturing method that could solve the main problem. All in all, one different redesigned concept was deemed as having potential for further development. The current solution was also deemed as having potential for future development but only when new manufacturing methods or techniques were considered.
57

Structure, propriétés électriques et travail de sortie de couches doubles indium / or .

Marliere, Christian 05 March 1985 (has links) (PDF)
Propriétés des électrons de conduction a l'interface de bicouches métalliques. La variation du travail de sortie lors du dépôt de in a 77k sur une couche mince d'or est modulée par des oscillations attribuées a un effet dimensionnel quantique. Mesure de la résistance électrique des bicouches in/au pendant les dépôts d'in et les traitements thermiques. On observe des augmentations irréversibles de la résistance électrique pendant les recuits, que l'on associe a des changements de structure localises a l'interface in/au. Ces changements de structure provoquent un accroissement de la diffusion des électrons de conduction a l'interface, et par conséquent une disparition des oscillations d'effet dimensionnel quantique observées pendant la croissance d'in.
58

Průmyslový areál s administrativní budovou / Industrial Park with Aministration Building

Krupa, Jakub January 2018 (has links)
This master thesis focuses on the design and elaboration of project documentation for the purpose of constructing Industrial park with administration building consisting of two parts, SO 01 – Administration building and SO 02 – Industrial building. The two objects are situated on the plot No. 715/1, in the cadastre unit Vrbno pod Pradědem located on an undeveloped land of the investor. The exit from the parking lot connects to the local traffic infrastructure. Public infrastructure leads in proximity to the land. The design of the construction respects local zoning plan. Project documentation was made in compliance with up-to-date requirements according to valid standards and regulations. The building is functionally divided into two objects, SO 01 and SO 02, which are operationally and structurally connected. Constructions of both objects are statically independent. The object SO 01, partially accessible to the public, is used for administrative tasks and staff facilities. Also, there is a sample room available to the public, gatehouse and warehouses. The object SO 02 is purposed for the production of plastic windows and solar panels. It mainly consists of areas used for production, but there is also an office for the master, a machine room for heating, ventilating and air conditioning (HVAC) and staff facilities. The object SO 01 is designed from a wall structural system from clay masonry, clay ceilings, strip foundation and a flat roof. The object SO 02 is designed as a full-metal prefabricated object with a saddle roof and foundation pads. The construction system of this object consists of steel columns. Plan dimensions of SO 01 are 25x14 metres. Building envelope is made from clay blocks, 440 mm in width, filled with mineral wool. Plan dimensions of SO 02 are 66,9x22,9 metres. Object’s curtain walling is made from prefabricated sandwich panels containing a core from PUR material.
59

Skladovací areál s administrativní budovou / Storage area with administrative building

Šesták, Tomáš January 2019 (has links)
This master thesis focused on the design and elaboration of project documentation for the purpose of a storage area with an administrative building, consisting of the premises SO 01 - storage hall and SO 02 - administrative building. Objects are located on parcels no. 4006/16, 4006/17, 4006/18, 4006/19, 4006/23, 4006/24, 4006/26, 4006/27, 4006/28, 4006/29, 4006/30, 4006/31, 4006/32, in the cadastre unit Dolní Bojanovice. They are located on an investor's land. Traffic connection is provided by the exit from the car park on the local road. All engineering infrastructure engineering networks are located near the site. The design of the building respects the local zoning plan. Project documentation is prepared in accordance with the current wording of applicable laws, decrees and standards. The project solves the structure functionally divided into objects SO 01 and SO 02, which are both operationally and structurally connected. The construction of objects is statically independent. The object SO 01 is designed for the storage of building material intended for storage in dry rooms. In addition to the storage space there is the air-conditioning machine room. The SO 02 facility serves administrative and staffing facilities. In the basement of the building there are rooms of technical background and archives. The SO 01 is designed as a full-metal mounted object with a counter roof and foundation pads. The design system of the SO 01 object is columnar with steel columns. The SO 02 building is designed from a wall construction system made of aerated concrete blocks with reinforced concrete ceilings, base strips and a flat roof. The SO 01 has a 65.5x20.2 m ground plan. The perimeter shell of the building consists of assembled sandwich panels with a core of pure material. The largest ground plan dimensions of the so 02 are 26.75x10.35 m. The perimeter shell is made up of 375 mm piece concrete blocks with a 150 mm contact system.
60

Low temperature epitaxy of Si, Ge, and Sn based alloys / Epitaxie basse température d'empilement à base de Si, Ge et Sn

Aubin, Joris 03 October 2017 (has links)
Les matériaux (Si)GeSn sont très prometteurs pour les composants optiques sur puce fonctionnant dans le Moyen Infra-Rouge (MIR). Lors de cette thèse de doctorat, j’ai étudié le Dépôt Chimique en Phase Vapeur d’alliages GeSn. L’épitaxie basse température de Ge pur, de Ge dopé phosphore et d’alliages GeSi a tout d’abord été explorée. L’utilisation du digermane (Ge2H6) au lieu du germane (GeH4) nous a permis d’augmenter considérablement la vitesse de croissance du germanium à des températures en dessous de425 °C. Des concentrations très importantes en atome de P électriquement actifs ont été atteintes à 350 °C, 100 Torr en chimie Ge2H6 + PH3 (au maximum 7.5x1019 cm-3). Nous avons par la suite combiné le Ge2H6 avec le disilane (Si2H6) ou le dichlorosilane (SiH2Cl2) afin d’étudier la cinétique de croissance du GeSi à 475 °C, 100 Torr. Des concentrations de Ge définitivement plus élevées (77-82%) et une meilleure qualité de surface ont été obtenues avec le SiH2Cl2. Finalement, la croissance basse température d’alliages GeSn a été étudiée dans notre bâti d’épitaxie industriel 200 mm. Le digermane (Ge2H6) et le tétrachlorure d'étain (SnCl4) ont été utilisés pour explorer la cinétique de croissance et les mécanismes de relaxation des contraintes du GeSn. Une large gamme de concentrations en Sn, i.e. 6-16%, a été sondée et ces points de fonctionnement utilisés pour épitaxier des couches épaisses de GeSn partiellement relaxées. Nous avons ainsi mis en évidence l’intérêt d’utiliser une structure dite en escalier, en termes de qualité cristalline et de morphologie de surface. Un tel empilement, avec 16% de Sn dans sa partie supérieure, a montré une structure de bande directe et a conduit à une émission laser (dans des micro-disques) à une longueur d’onde de 3.1 µm. Ce laser a fonctionné jusqu’à 180 K et a un seuil de 377 kW/cm² à 25K. / (Si)GeSn is very promising for use in Mid Infra-Red (MIR) group-IV optical components on chip. During this PhD, I have studied the Reduced Pressure Chemical Vapor Deposition of GeSn alloys. The very low temperature epitaxy of pure Ge, heavily phosphorous doped Ge and Ge-rich SiGe alloys have first of all been investigated. Using digermane (Ge2H6) instead of germane (GeH4) enabled us to dramatically increase the Ge growth rate at temperatures 425 °C and lower. Very high electrically active P concentrations were obtained at 350 °C, 100 Torr with a Ge2H6 + PH3 chemistry (at most 7.5x1019 cm-3). We have then combined digermane with disilane (Si2H6) or dichlorosilane (SiH2Cl2) in order to study the GeSi growth kinetics at 475 °C, 100 Torr. Definitely higher Ge concentrations (77-82%) and smoother surfaces have been obtained with SiH2Cl2. We have then explored the low temperature epitaxy of high Sn content GeSn alloys in our 200 mm industrial RP-CVD tool. Digermane (Ge2H6) and tin tetrachloride (SnCl4) were used to investigate the GeSn growth kinetics and strain relaxation mechanisms. Large range of Sn concentrations, i.e. in the 6-16% range, was probed and data points used to grow thick, partially relaxed GeSn layers. The benefits of using Step-Graded structures, in terms of crystalline quality and surface morphology, was conclusively demonstrated for thick GeSn layers with high Sn contents. Such a stack, with 16% of Sn in the top part, was direct bandgap and led to a laser operation (in micro-disks) up to 180 K at an emission wavelength of 3.1 µm and with a lasing threshold of 377 kW/cm² at 25K.

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