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Dissertations / Theses on the topic 'Thermomechanical processes'
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Leung, Winnie C. M. "Thermomechanical analyses of metal solidification processes." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/42561.
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Malas, James C. "Methodology for design and control of thermomechanical processes." Ohio : Ohio University, 1991. http://www.ohiolink.edu/etd/view.cgi?ohiou1173324636.
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Malas, James C. III. "Methodology for design and control of thermomechanical processes." Ohio University / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1173324636.
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Fischer, Christian E. "Forging process models for use with global optimization of manufacturing processes." Ohio University / OhioLINK, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1175269765.
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Georges, Cédric. "Improvement of the mechanical properties of TRIP-assisted multiphase steels by application of innovative thermal or thermomechanical processes." Université catholique de Louvain, 2008. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-08232008-100716/.
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For ecological reasons, the current main challenge of the automotive industry is to reduce the fuel consumption of vehicles and then emissions of greenhouse gas. In this context, steelmakers and automotive manufacturers decided for some years now to join their efforts to promote the development and use of advanced high strength steels such as TRIP steels. A combination of high strength and large elongation is obtained thanks to the TRansformation Induced Plasticity (TRIP) effect. However, improvement of the mechanical properties is still possible, especially by the refinement of the matrix. In this work, two main ways were followed in order to reach improved properties. The classical way consisting of the annealing of cold-rolled samples and an innovative way consisting of obtaining the desired microstructure by direct hot rolling of the samples. In the classical way, this refinement can be obtained by acting on the chemical composition (with such alloying elements like Cu and Nb). It was observed that complete recrystallisation of the ferrite matrix is quite impossible in presence of Cu precipitates. In addition, if the ferrite recrystallisation is not completed before reaching the eutectoid temperature, the recrystallisation will be slowed down by a large way. An innovative heat treatment consisting in keeping the copper in solid solution in the high-Cu steel was developed. Therefore, ferrite recrystallises quite easily and very fine ferrite grains (~1µm) were obtained. In the innovative way, the effects of hot-rolling conditions on TRIP-assisted multiphase steels are of major importance for industrial practice and could open new dimensions for the TRIP steels (i.e. thanks to precipitation mechanisms leading to additive strengthening). Impressive mechanical properties (true stress at maximum load of 1500 MPa and true strain at uniform elongation of 0.22) were obtained with a relatively easy thermomechanical process, the role played by Nb being essential.
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Kumar, Abhimanyu. "Comprehensive Modeling of Shape Memory Alloys for Actuation of Large-Scale Structures." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1289883464.
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Ajmal, Mohammed. "Thermomechanically processed dual-phase steel : effects on hardenability and mechanical properties." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328761.
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Stancy, Steven L. "Assessment of grain refinement by microtexture analysis in thermomechanically processed Al 2519 alloy." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA306238.
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Liu, Zhidan [Verfasser]. "Thermomechanically processed magnesium-silver alloys as antibacterial and biodegradable implant materials / Zhidan Liu." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1155420748/34.
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Rogers, Stephen Andrew. "The role of particles in recrystallization of a thermomechanically processed A1-Mg alloy." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/24029.
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Liu, Jie. "Characterization of New Rotary Endodontic Instruments Fabricated from Special Thermomechanically Processed NiTi Wire." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244643081.
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Buergy, Alexandra. "Modulation de la texture et de la fragmentation tissulaire de fruits lors de traitements thermiques par les modes de culture et la maturation : impact sur la texture des purées Pectin modifications in raw fruits alter texture of plant cell dispersions Apple puree’s texture is independent from fruit firmness Pectin degradation explains tissue fragmentation of fruits during thermomechanical processes for puree production." Thesis, Avignon, 2021. http://www.theses.fr/2021AVIG0282.
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L’objectif de cette thèse était de comprendre comment les caractéristiques structurales des pommes peuvent être liées aux facteurs structurels des purées après cuisson et fragmentation tissulaire. Les caractéristiques structurales du fruit ont été modulées par les cultivars, les pratiques culturales et la maturation, et les conditions du procédé (thermique : 50–95 °C et mécanique : 100–3000 tr/min) ont été modulées grâce à un cuiseur-broyeur. La structure de la purée (volume occupé par les particules, taille des particules, viscosité du sérum) et la texture (viscosité, seuil d’écoulement, G’ et G’’) ont ensuite été analysées et comparées entre les matières premières et les conditions du procédé. Les pectines ont été extraites et leur composition chimique ainsi que leur structure ont été corrélées à la structure de la purée. La taille des particules s´est montré être le déterminant majeur de la texture des purées en absence de dilution ou de concentration. Le degré d’adhésion cellulaire (défini par la structure et la composition des pectines) a eu un impact plus important sur la taille des particules que la taille des cellules individuelles (définie par les cultivars ou les pratiques culturales). D’autres facteurs structuraux, tels que la viscosité du sérum ou la quantité de pulpe, n’ont contribué à la texture des purées qu’à taille de particules constante. La fragmentation tissulaire, déterminant la taille des particules pendant le procédé, a été principalement affectée par l’intensité du cisaillement. Le stockage post-récolte des pommes et des températures élevées (95 °C) ont induit une dégradation et une solubilisation des pectines, en particulier par l'hydrolyse des chaînes latérales des rhamnogalacturonanes I. Cela a réduit l’adhésion cellulaire et la fragmentation tissulaire a ainsi été favorisée. Ces résultats ont permis d´approfondir la compréhension de la fragmentation tissulaire et des changements de texture au cours du procédé ce qui permettra de fournir des directives à l’industrie pour mieux gérer la diversité et l’hétérogénéité des fruits pendant le procédé de transformation des fruits en puréeThe objective of this thesis was to understand how structural characteristics in raw apples can be linked to structural factors in purees after cooking and tissue fragmentation. Structural characteristics of the fruit were modulated by cultivars, agricultural practices and maturation, and process conditions (thermal: 50–95 °C and mechanical: 100–3000 rpm) were modulated in a cooker-cutter during processing. Puree’s structure (volume occupied by particles, particle size, serum viscosity) and texture (viscosity, yield stress, G’ and G’’) were then analysed and compared between raw materials and process conditions. Pectins were extracted and their chemical composition and structure were correlated to puree’s structure. Particle size appeared to be the most important determinant of puree’s texture when there is no dilution or concentration of the fruit tissue. The extent of cell adhesion (defined by pectin structure and composition) determined particle size more than individual cell size (defined by varietal effects or agricultural practices). Other structural factors only contributed to puree’s texture once particle size was constant. Tissue fragmentation, determining particle size during processing, was principally affected by shear intensity. Post-harvest maturity of the raw apples and high temperatures (95 °C) induced pectin degradation, especially rhamnogalacturonan I side chain hydrolysis, and solubilisation. This led to reduced cell adhesion and tissue fragmentation was additionally favoured. The results deepened the understanding of tissue fragmentation and textural changes during processing and provided guidelines for industry to manage diversity and heterogeneity of raw fruits during processing
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Vena, P. F. "Thermomechanical pulping (TMP), chemithermomechanical pulping (CTMP) and biothermomechanical pulping (BTMP) of bugweed (Solanum mauritianum) and Pinus Patula." Thesis, Link to the online version, 2005. http://hdl.handle.net/10019/1283.
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Quint, Karsten [Verfasser]. "Thermomechanically coupled processes for functionally graded materials : experiments, modelling, and finite element analysis using high-order DIRK-methods / Karsten Quint." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2012. http://d-nb.info/1024717844/34.
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Entringer, Jannik [Verfasser], and Norbert [Akademischer Betreuer] Huber. "Microstructure evolution and stress corrosion cracking behavior in short-term thermomechanically processed Al-Cu-Li alloys / Jannik Entringer ; Betreuer: Norbert Huber." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2019. http://d-nb.info/1194464661/34.
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Pilch, Jan. "Studium funkčních vlastností tenkých vláken NiTi pro aplikace v smart strukturách a textiliích." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-233961.
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PhD thesis focuses the field of textile application of modern functional materials, namely metallic shape memory alloys with unique thermomechanical properties deriving from martensitic transformation in solid state. Particularly, it deals with the development of a nonconventional thermomechanical treatment of thin NiTi filaments via Joule heating by electric current and related basic research involving thermomechanical testing and modeling of functional properties of the filaments, investigation of martensitic transformations and deformation processes in NiTi and investigation of the fast recovery and recrystallization processes in metals heated by short pulses of controlled electric power. The method was developed and called FTMT-EC. In contrast to conventional heat treatment of metallic filaments in environmental furnaces, this method allows for precise control of the raise of the filament temperature and filament stress during the fast heating (rate ~50 000 °C/s). As a consequence, it is possible to precisely control the progress of the fast recovery and recrystallization processes in heat treated filaments. In this way it is possible to prepare filaments with desired nanostructured microstructure and related functional properties. A prototype equipment for application of the method for heat treatment of continuous SMA filaments during respooling in textile processing was designed and built. Comparing to the conventional heat treatment of SMA filaments in tubular environmental furnaces, this approach is faster, saves energy and allows for preparation of filaments with special functional properties. International patent application was filed on the method. It is currently utilized in the research and development of smart textiles for medical applications.
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Boyle, Kevin P. "The role of particle cracking in dilatation during tensile straining of a cast and thermomechanically processed 6061 Al - 20 volume percent Al2O3 metal matrix composite." Thesis, Monterey, California. Naval Postgraduate School, 1996. http://hdl.handle.net/10945/8929.
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Approved for public release; distribution is unlimited.In this work, the dilatation during tensile straining of a cast and thermomechanically processed 6061 Al - Al2O3 metal matrix composite (MMC) containing 20 volume percent of Al2O3 particles was examined. Standard tensile samples of the MMC and unreinforced 6061 Al were machined. Precise diameter measurements were made of both composite and unreinforced samples prior to and immediately following tensile straining. Tension tests were conducted to various strains as well as to fracture and an extensometer was employed to obtain accurate measurement of the axial strain. The MMC material exhibited a continuously increasing dilatation during tensile straining while the unreinforced 6061 control material deformed plastically at constant volume. Careful metallographic preparation revealed particle cracking in all MMC samples throughout the range of strains examined. A clear trend of increased frequency of particle cracking was observed. Void formation and growth due to cracking of the particles was analyzed and shown to correlate with the dilatation observed during tensile straining of the composite. Linkage of such voids is proposed as the mechanism of crack propagation at failure of the MMC.
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Collomb, Jean. "Optimisation du processus de dimensionnement thermomécanique de Moule Autonome à Transfert Thermique Efficient pour transformation rapide des matériaux composites à renforts continus." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAA019/document.
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L’enjeu du projet MATTE est de proposer à terme un mode de transformation novateur utilisant des technologies parfaitement maîtrisées, pour la production haute cadence de structures composites hautes performances à fibres continues et résines thermoplastiques (composites TPFC) ou thermodure. Ce système fait partie des techniques dites Heat&Cool, bien connues dans le domaine de l’injection plastique. Il s’agit ici d’étendre ces techniques au domaine des matériaux composites structuraux. Par rapport aux moyens existant, ce procédé permettra d’intégrer en production : de nouvelles fonctions de contrôle, de réduire les consommations énergétique de l’ordre de 80%, les investissements périphériques de 30% et de tendre vers un temps de cycle complet inférieur à 3 minutes. Le procédé similaire dans les composite déjà existant est le RTM lourd, cependant il est très énergivore et ne permet de faire que de la moyen cadence dû à des cycles de cuisson assez long. Il est donc la référence pour quantifier les performances de la technologie MATTEThe issue of MATTE project is to propose an innovative process using perfectly controlled technologies for the production of structural composites high speed high performance with continuous fibers and thermoplastic resins (composites TPFC) or thermoset. This system is one of the techniques known as Heat & Cool, well known in the field of plastic injection. The aim of this technology is to extend these techniques to the field of structural composites. Compared to existing resources, this process will integrate in production: new monitoring functions, reduce energy consumption by about 80%, peripheral investments by 30% and to pursue a complete cycle time of less than 3 minutes. The similar method in the existing composite is the RTM, however, it is high energy consumption technology and do not allow high production rate. It is therefore the reference to quantify the performance of the MATTE technology
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Boyle, Kevin P. "The role of particle cracking in dilatation during tensile straining of a cast and thermomechanically processed 6061 Al - 20 volume percent Al₂O₃ metal matrix composite /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA324274.
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Thesis (M.S. in Mechanical Engineering) Naval Postgraduate School, September 1996.Thesis advisor(s): T.R. McNelley. "September 1996." Includes bibliographical references (p. 47-49). Also available online.
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AMORIM, Fernando Andrade. "Comportamento termomecânico de fios superelásticos de NiTi Soldados pelos processo TIG." Universidade Federal de Campina Grande, 2014. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/509.
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Ligas de NiTi têm possibilitado revolucionar muitos projetos tradicionais de engenharia com suas propriedades únicas de superelasticidade (SE) e efeito de memória de forma (EMF). Com o interesse em incorporar esses materiais em diferentes aplicações e dispositivos, o desenvolvimento de tecnologia eficaz para soldagem de ligas NiTi torna-se necessário, devido ao fato de esse tipo de união proporcionar a fabricação das mais diferentes formas geométricas e combinações entre materiais similares e dissimilares. Nesse contexto, este estudo teve como objetivo geral determinar as variações das propriedades termomecânicas em juntas soldadas de fios de NiTi. Para o trabalho, fios superelásticos de uma LMF NiTi (ASTM F2063) com 0,4 e 0,9 mm de diâmetro, foram divididos em dois grupos: (a) fios sem tratamento térmico (NiTiA) e (b) fios com tratamento térmico a 400 °C durante 20 minutos (NiTi400). Em seguida estes fios foram soldados pelo processo TIG autôgeno, utilizando a soldadora Micromelt (EDG Equipamentos e Controles). A caracterização termomecânica dos fios íntegros e soldados foi realizada utilizando ensaios de calorimetria diferencial de varredura (DSC), análise dinâmico-mecânica (DMA), ensaios de tração uniaxial em diferentes temperaturas (30°C a 70°C), microscopia óptica (MO), microscopia eletrônica de varredura (MEV) e micro indentação Vickers. Os resultados obtidos demonstraram uma boa eficiência do processo TIG ao soldar os fios NiTi de ambos os grupos. Ensaios de DSC relevaram que o processo de soldagem pode promover modificações de natureza metalúrgica aos fios de NiTi, de maneira a reduzir as temperaturas de transformações de fase. Já no que diz respeito ao aspecto mecânico, os fios soldados apresentaram resistência a ruptura por tração de até 750 MPa (NiTiA ~ 70 °C) e valores de deformações de até 8,5 % (NiTiA).
NiTi alloys enabled revolutionize many traditional engineering projects with uniques properties of superelasticity (SE) and shape memory effect (SME). Interested on incorporating these materials in different applications and devices, developments of efficient welding technology for NiTi alloys becomes necessary due to the fact that this type of process can provide many differents geometric shapes and combinations of similar and dissimilar materials. In this context, this study had as main objective to determine variations in thermomechanical properties for NiTi welded wires. For this work, superelastic NiTi SMA wire (ASTM F2063) with 0.9 to 0.4 mm in diameter were divided into two groups: (a) wires without heat treatment (NiTiA) and (b) heat treated wires at 400 ° C for 20 minutes (NiTi400). Then, these wires were welded by autogenous welding process, using the Micromelt machine (EDG, Equipment and Controls). The thermomechanical characterization of as received and as welded wires was performed by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) uniaxial tensile test at different temperatures (30°C to 70°C), optical microscopy (OM), scanning electron microscopy (SEM) and Vickers micro indentation. The results showed a good efficiency of TIG welding for every NiTi wire studied groups. DSC curves demonstrates that welding process can cause a metallurgical changes into NiTi wires, promoting changes in phase transformation temperatures. The mechanical properties of the welded wire presented a tensile rupture strength of 750 MPa (NiTi~70 °C) and strain values up to 8.5% (NiTiA).
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Cuevas, Assunta Mariela. "Microstructure characterization of friction-stir processed nickel-aluminum bronze through orientation imaging microscopy." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02sep%5FCuevas.
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Fall, Ameth Maloum. "Etude de la rhéologie à chaud et des évolutions microstructurales de l'alliage Ti-5553." Thesis, Saint-Etienne, EMSE, 2015. http://www.theses.fr/2015EMSE0801/document.
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L’alliage Ti-5553 destiné à la fabrication des trains d’atterrissage suit au cours de sa mise en forme, un schéma thermomécanique assez complexe composé par des étapes de forgeage successives dans les domaines monophasé β et biphasé α+β. Ainsi dans le but de rendre possible l’optimisation de ses gammes de forgeage, un important développement des connaissances sur la rhéologie et sur les évolutions microstructurales au cours du traitement thermomécanique est donc nécessaire pour l’entreprise Messier Bugatti Dowty. L’objectif ici est de déterminer expérimentalement la rhéologie et de modéliser le comportement mécanique ainsi que la caractérisation des microstructures de l’alliage Ti-5553 au cours des séquences de déformations dans les domaines et. La détermination expérimentale de la rhéologie à chaud de l’alliage Ti-5553 a été réalisée d’une part au moyen d’essais de compression uniaxiale dans les domaines biphasé et monophasé, ce qui a permis d’identifier une loi de comportement du matériau dans le domaine pour les deux états "billette" et "pièce forgée", de décrire le comportement rhéologique du Ti-5553 dans les domaines de température, de vitesse et de déformation comprises respectivement entre 720 et 990 °C ; 0,001 et 1 s–1 ; 0,1 et 1,2. C’est ainsi qu’un modèle rhéologique a été proposé, basé sur la Loi de Hansel et Spittle qui prend en compte l’évolution de la contrainte d’écoulement du matériau en fonction de la vitesse de déformation et de la température.Par ailleurs, les analyses microstructurales réalisées en microscopie optique, aux rayon X, au MEB et en EBSD ont permis de caractériser les tailles des grains et , des textures des états initiaux et de déformés, et de mettre en évidence un phénomène de précipitation dynamique de la phase Ti-5553 alloy used for landing gear manufacturing has a complex thermomechanical diagram during hot working process which consists of successive forging steps in the single phase β and the two phase α+β regions. For this purpose, in order to optimize theTi-5553 forging process in Messier-Bugatti-Dowty Company, significant development of knowledge of rheology and the microstructural evolution during thermomechanical processing is necessary. The aims of this work are: i) to find out experimentally the rheology, ii) to model the mechanical behavior, and iii) to characterize the microstructural changes during different strain sequences in theα+β and β regions.Uniaxial compression tests were carried out in order to determine the rheology of the Ti-5553 alloy in the single and the two-phase region. The latter provide the behavior of the alloy in the two initial states, “billet” and “as forget”. This information was used to determine the rheological behavior of the material in the temperature range 720 to 990 ˚C, strain rate range 0.001 to 1 s-1 and strains in the range 0.1 to 1.2. A rheological model of the material behavior based on Hansel-Spittle equations was proposed which takes into account the dependence of the flow behavior of the material with strain rate and temperature.Moreover, characterisation methods such as optical, scanning electron microscopies, X-rays and EBSD analyses were used to examine the microstructures in the initial state (undeformed) and the deformed material. These techniques allowed the measurement of alpha and beta grain sizes as well as the texture of the material at different conditions (undeformed and deformed material). The results also indicated that a dynamic α-phase precipitation phenomenon in the material can take place during the hot working process
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Charfeddine, Yasmine. "Contribution à l’étude de l'intégrité des surfaces fonctionnelles induites par un procédé thermomécanique-mécanique combiné : rectification-galetage." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEE008.
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Le procédé « REGAL » est une approche originale combinant deux procédés de fabrication différents, l’un thermomécanique (la rectification) et l’autre purement mécanique (le galetage), mis en œuvre simultanément. Pour cela, des modélisations et des simulations numériques 3D des différents procédés de rectification, de galetage et de rectification/galetage combiné ont été réalisées dans le but de mieux comprendre la physique à l’origine de l’obtention d’une meilleure intégrité de surface que celle obtenue par chaque procédé agissant séparément. Une démarche expérimentale a été développée sur la rectifieuse utilisée afin de pouvoir rectifier et galeter simultanément et un système de fixation de l’outil de galetage sur la broche de la rectifieuse a été conçu et fabriqué. Par ailleurs, l’avance automatique transverse de la rectifieuse utilisée est de l’ordre du mm par cycle alors qu’elle devrait être de l’ordre du μm/cycle pour le procédé de galetage. Ainsi, pour assurer un recouvrement total en galetage, il a été nécessaire de développer un système entièrement automatisé qui se positionne sur la table de la rectifieuse et qui permet d’avoir les bonnes avances par cycle avec une précision du dixième de micromètre. Des caractérisations de plusieurs facteurs de l’intégrité de surface ont été réalisées et ont montré que le procédé REGAL peut améliorer la qualité de la surface et introduire des contraintes résiduelles en compression à une profondeur plus importante que celle obtenue par le procédé de galetage agissant seul. La détermination expérimentale des contraintes résiduelles a permis de valider et de discuter les résultats des simulations numériques obtenus.Le procédé « REGAL » est une approche originale combinant deux procédés de fabrication différents, l’un thermomécanique (la rectification) et l’autre purement mécanique (le galetage), mis en œuvre simultanément. Pour cela, des modélisations et des simulations numériques 3D des différents procédés de rectification, de galetage et de rectification/galetage combiné ont été réalisées dans le but de mieux comprendre la physique à l’origine de l’obtention d’une meilleure intégrité de surface que celle obtenue par chaque procédé agissant séparément. Une démarche expérimentale a été développée sur la rectifieuse utilisée afin de pouvoir rectifier et galeter simultanément et un système de fixation de l’outil de galetage sur la broche de la rectifieuse a été conçu et fabriqué. Par ailleurs, l’avance automatique transverse de la rectifieuse utilisée est de l’ordre du mm par cycle alors qu’elle devrait être de l’ordre du μm/cycle pour le procédé de galetage. Ainsi, pour assurer un recouvrement total en galetage, il a été nécessaire de développer un système entièrement automatisé qui se positionne sur la table de la rectifieuse et qui permet d’avoir les bonnes avances par cycle avec une précision du dixième de micromètre. Des caractérisations de plusieurs facteurs de l’intégrité de surface ont été réalisées et ont montré que le procédé REGAL peut améliorer la qualité de la surface et introduire des contraintes résiduelles en compression à une profondeur plus importante que celle obtenue par le procédé de galetage agissant seul. La détermination expérimentale des contraintes résiduelles a permis de valider et de discuter les résultats des simulations numériques obtenusCombining grinding with burnishing called “REGAL” is a newly developed outstanding technique consisting in grinding and burnishing operating simultaneously. The purpose behind this innovative approach is to enhance the surface integrity of the workpiece obtained by REGAL if compared to grinding and burnishing performing each one apart. REGAL process is made possible thanks to the design and manufacturing of a mechanical fixing system capable of maintaining the burnishing ball next to the grinding wheel. An automated control table is needed to make small and precise lateral feeds in order to ensure high surface recovery rates obtained by the ball burnishing tool. The most influential parameters of REGAL process were identified and their impacts on surface integrity were studied in terms of forces, roughness and residual stress results. The experimental results have shown that further from gaining time and energy by combining two processes in one, REGAL process enhances drastically the quality of the surface obtained if compared to workpiece surfaces obtained after grinding and burnishing acting separately. In addition, simultaneous grinding and burnishing introduces compressive residual stress results at the surface and beneath it reaching a deeper depth than the depth obtained by burnishing at the same manufacturing conditions thanks to the physicochemical changes obtained by the simultaneous thermomechanical/purely mechanical loads applied to the workpiece. 3D numerical simulations of grinding, burnishing and REGAL were also conducted to understand the physical phenomena occurring that is responsible of getting a more compressive residual stress layer obtained by REGAL if compared to burnishing acting separately and are in adequacy with the experimental results
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Tabalaiev, Kostiantyn. "Etude de la structure et des propriétés de l'acier à béton après déformations à froid." Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00566878.
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Les propriétés généralement demandées aux armatures pour béton armé doivent répondre à des exigences particulières précisées dans des normes nationales, européennes et internationales. Actuellement, dans la pratique de la production de l'acier à béton, on tend à substituer différentes nuances d'armature par une armature unifiée ayant une valeur de limite d'élasticité minimale de 500 MPa. Le remplacement des ronds à béton de nuance 400MPa par cette armature conduit à une économie de métal de l'ordre de 10-20 % d'après les estimations de différents spécialistes.Il existe, généralement, plusieurs techniques de fabrication des armatures, dont la déformation à chaud suivie d'un refroidissement accéléré sous flux d'eau (traitement thermomécanique ou Thermomechanical Control Process - TMCP), ainsi que la déformation à froid (tréfilage â travers une filière conique et une filière à rouleaux, microlaminage...), qui se heurte cependant â l'impossibilité de satisfaire aux exigences des Normes vis-à-vis des propriétés de résistance (Re > 500MPa) et de plasticité.Le présent travail a pour but le développement d'un procédé combiné de production d'acier à béton profitant des aspects positifs de deux types de déformation à chaud ainsi qu'à froid, sous forme du traitement combiné mécano-thermomécanique (post déformations à froid après le TMCP). et d'étudier la possibilité de production d'aciers à béton de qualité 500 MPa (B(A)500), de petits diamètres, en couronne, répondant aux exigences des Normes modernes. L'objectif scientifique de ce travail est d'étudier les mécanismes microstructuraux qui se produisent lors de la déformation à froid de l'acier préalablement traité thermomécaniquement et leurs conséquences sur l'évolution des propriétés mécaniques.Plusieurs nuances d'acier bas carbone de différents diamètres ont été étudiées. De nombreuses techniques de caractérisation macroscopique et microscopique de la structure de l'acier ont été utilisées: traction monotone, essais de microdureté, microscopie optique, microscopie électronique â balayage (MEB) et en transmission (MET), diffraction des rayons X. spectrométrie mécanique..Les résultats des essais montrent qu'il est possible d'obtenir avec assurance l'armature de qualité B(A)500, possédant des propriétés mécaniques qui dépassent les exigences des nonnes, à l'aide d'une déformation par torsion avec un cisaillement maximal de 22%, pour des aciers à 0.15 -0.2 % C(en poids), faiblement alliés en Mn et Si et traités themomécaniquement. La déformation par torsion provoque une augmentation de dureté en surface mais aussi au cœur de l'armature. Cette augmentation de dureté à cœur peut être amplifiée par le traitement thermique de vieillissement à 100°C correspondant à l'utilisation en Génie Civil. Cet effet, lié aux interactions dislocation-impuretés interstitielles, a été expliqué grâce â la MET et à l'étude du frottement intérieur.
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Hamaguchi, Marcelo. "Análise do circuito de água em processo de fabricação de papel imprensa integrada com produção de pastas termomecânicas." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-09012008-175600/.
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A indústria de papel e celulose passa por constantes desafios para solucionar problemas relacionados ao alto consumo de água industrial. Uma alternativa é utilizar ferramentas como a Integração de Processos, onde é possível aplicar técnicas gráficas como o \"Water Pinch\" ou técnicas com programação matemática para otimizar o circuito de água. Para contribuir com o setor, as técnicas foram aplicadas no presente trabalho utilizando-se dados reais coletados em uma unidade produtora de polpa termomecânica e papel imprensa. Com os dados, um caso base em um simulador foi desenvolvido para iniciar a análise por Integração de Processos. A análise é baseada no aproveitamento das correntes de águas residuais em outras etapas do processo sob restrições na concentração limite de contaminantes, especificamente finos e sólidos dissolvidos. Diferentemente dos trabalhos apresentados na literatura que alegam que a solução encontrada trata-se de valores otimizados, os resultados mostram que os valores encontrados através da programação matemática e do método Pinch são teoricamente corretos, porém, quando novamente simuladas sob estas novas condições obtidas por Integração de Processos, as condições operacionais da unidade industrial mostram-se inadequadas. As concentrações limites de contaminantes previamente estabelecidos pelas técnicas utilizadas são frequentemente ultrapassadas nos resultados de recálculo por simulação, e portanto, as soluções de Integração de Processos devem ser corrigidas antes de implantação. Por isso, os valores previstos, por exemplo, de redução de consumo de até 38% no projeto realístico atinge o valor de 23%, o que ainda é um bom resultado. O trabalho ainda mostra que a programação matemática é eficaz e rápida para encontrar soluções com múltiplos contaminantes, enquanto o método Pinch é mais voltado para casos com contaminante simples.The Pulp and Paper industry has constantly struggled to solve problems related to high water consumption. One alternative is to use tools like Process Integration, where graphical methods and mathematical programming can be applied to optimize the water circuit. To contribute to the Pulp and Paper sector, the methods were applied in the present work using real process data that have been collected in an integrated thermomechanical and newsprint mill. With these data, a base case simulation was developed to initiate the analysis by Process Integration. The analysis is based on residual water reuse in other process stages under propriety constraints like contaminants concentration limits, specifically the dissolved solids and fine fibers. Differently from works presented in the references that claim that solutions found are optimized values, the results of this work show that values found by mathematical programming and pinch method are theoretically correct, however, the operational conditions of the mill become inadequate when simulated under new conditions achieved by Process Integration. The concentration limits of contaminants previously established for the methods have their values frequently exceed after recalculation by simulation, and thus, the solutions by Process Integration must be corrected before using them. So, if the predicted value for reduction of fresh water consumption is, for example, 38%, in the realistic project this value will reach only 23%, which is still a good result. The work also shows that mathematical programming is efficient to find solutions when there are multiple contaminants, while pinch method is more adequate for those cases with single contaminant.
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Guenoun, Gabriel. "Frittage de pièces de Polytétrafluoroéthylène (PTFE) compacté : Mécanismes physiques et modèles." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN054.
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Le polytétrafluoroéthylène (PTFE) est un polymère semi-cristallin ayant de nom- breuses propriétés remarquables avec notamment une excellente tenue thermique, un coeffi- cient de frottement extrêmement faible et une grande résistance à la corrosion. Ces atouts lui valent d’être utilisé dans de nombreuses applications.Sa mise en forme s’effectue par des procédés similaires à ceux utilisés pour les poudres métalliques. Dans l’un d’eux, la poudre de PTFE est compactée uniaxialement en pièces cylin- driques. L’étape suivante est le frittage de la poudre compactée, au cours de laquelle les pièces sont chauffées au-delà de la température de fusion du polymère. Durant ce cycle thermique, les pièces subissent de grandes déformations causées notamment par la fusion et la recristallisation du PTFE. Les gradients thermiques couplés à ces déformations peuvent engendrer des incom- patibilités mécaniques pouvant conduire à l’endommagement, voire à la rupture des pièces.Cette thèse a permis d’apporter une compréhension plus fine des phénomènes physiques à l’œuvre durant le frittage du PTFE compacté par des observations et analyses microstruc- turales, et des essais de caractérisation thermique et mécanique. La relaxation de contraintes résiduelles, la fermeture de porosités et un phénomène de cristallisation secondaire ont ainsi été mis en évidence et génèrent des déformations libres de contraintes macroscopiques. Les propriétés mécaniques du matériau en température ont également été déterminées lors du frit- tage. Un modèle a été développé pour rendre compte de ces observations. Il a été intégré dans une simulation thermomécanique du procédé de frittage d’une pièce de référence. Le modèle a été validé par comparaison des résultats de la simulation à des mesures réalisées sur des expériences de laboratoire.Enfin, un outil de simulation numérique par éléments finis a été développé. Il permet de déterminer les états de contrainte et déformation ainsi que la répartition des taux de cristalli- sation et des propriétés thermomécaniques au sein d’une pièce de PTFE compacté durant le cycle de frittage. A terme, cet outil pourrait permettre d’optimiser les paramètres du procédé industriel pour, par exemple, réduire le temps de frittage tout en s’assurant d’avoir des pièces non-endommagées et possédant les propriétés requisesPolytetrafluoroethylene (PTFE) is a semi-crystalline polymer with many outstand- ing properties including excellent thermal resistance, extremely low friction coefficient and high corrosion resistance. These advantages make it suitable for many applications.It is shaped by processes similar to those used for metal powders. In one of them, the PTFE powder is uniaxially compacted into cylindrical parts. The next step is the compacted powder sintering process, in which the parts are heated above the melting temperature of the polymer. During this thermal cycle, the parts undergo large strains caused by the melting and the recrystallization of PTFE. Thermal gradients coupled with these strains induce mechanical incompatibilities that can lead to damage or even failure of the parts.This study provides a more detailed understanding of the physical mechanisms at work dur- ing the sintering of compacted PTFE through microstructural observations and analyses, and thermal and mechanical characterization tests. The relaxation of residual stresses, the closure of porosity and a secondary crystallization mechanism have thus been highlighted and generate macroscopic stress-free strain (called eigenstrain). The mechanical properties of the material as function of temperature have been also determined during sintering. A model has been devel- oped to take into account these observations. It has been integrated into a thermomechanical simulation of the sintering process of a reference part. The model has been validated by com- paring the simulation results with measurements from a laboratory experiments.Finally, a finite element numerical simulation tool has been developed. It is used to determine the stresses and strains as well as the distribution of crystallization rates and thermomechanical properties within a PTFE part compacted during the sintering cycle. In the long term, this tool could make it possible to optimize the industrial process parameters to reduce sintering time, for example, while ensuring that the parts are undamaged and have the required properties
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Lu, Ye. "Construction d’abaques numériques dédiés aux études paramétriques du procédé de soudage par des méthodes de réduction de modèles espace-temps." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI103/document.
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Le recours à des simulations numériques pour l’étude de l’influence des paramètres d’entrée (matériaux, chargements, conditions aux limites, géométrie, etc.) sur les différentes quantités d’intérêt en soudage (contraintes résiduelles, distorsion, etc.) s’avère trop long et coûteux vu l’aspect multi-paramétrique de ces simulations. Pour explorer des espaces paramétriques de grandes dimensions, avec des calculs moins coûteux, il parait opportun d’utiliser des approches de réduction de modèle. Dans ce travail, d’une façon a posteriori, une stratégie non-intrusive est développée pour construire les abaques dédiées aux études paramétriques du soudage. Dans une phase offline, une base de données (‘snapshots’) a été pré-calculée avec un choix optimal des paramètres d'entrée donnés par une approche multi-grille (dans l’espace des paramètres). Pour explorer d’autres valeurs de paramètres, une méthode d’interpolation basée sur la variété Grassmannienne est alors proposée pour adapter les bases réduites espace-temps issues de la méthode SVD. Cette méthode a été constatée plus performante que les méthodes d’interpolation standards, notamment en non-linéaire. Afin d’explorer des espaces paramétriques de grandes dimensions, une méthode de type décomposition tensorielle (i.e. HOPGD) a été également étudiée. Pour l’aspect d’optimalité de l’abaque, nous proposons une technique d’accélération de convergence pour la HOPGD et une approche ‘sparse grids’ qui permet d’échantillonner efficacement l’espace des paramètres. Finalement, les abaques optimaux de dimension jusqu’à 10 à précision contrôlée ont été construits pour différents types de paramètres (matériaux, chargements, géométrie) du procédé de soudageThe use of standard numerical simulations for studies of the influence of input parameters (materials, loading, boundary conditions, geometry, etc.) on the quantities of interest in welding (residual stresses, distortion, etc.) proves to be too long and costly due to the multiparametric aspect of welding. In order to explore high-dimensional parametric spaces, with cheaper calculations, it seems to be appropriate to use model reduction approaches. In this work, in an a posteriori way, a non-intrusive strategy is developed to construct computational vademecum dedicated to parametric studies of welding. In an offline phase, a snapshots database is pre-computed with an optimal choice of input parameters given by a “multi-grids” approach (in parameter space). To explore other parameter values, an interpolation method based on Grassmann manifolds is proposed to adapt both the space and time reduced bases derived from the SVD. This method seems more efficient than standard interpolation methods, especially in non-linear cases. In order to explore highdimensional parametric spaces, a tensor decomposition method (i.e. HOPGD) has also been studied. For the optimality aspect of the computational vademecum, we propose a convergence acceleration technique for HOPGD and a “sparse grids” approach which allows efficient sampling of the parameter space. Finally, computational vademecums of dimension up to 10 with controlled accuracy have been constructed for different types of welding parameters (materials, loading, geometry)
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Serebriakov, Ivan. "Tribologie à haute température : analyse expérimentale et numérique du comportement interfacial tenant compte de l'influence des conditions de contact thermomécaniques." Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2021. http://www.theses.fr/2021UPHF0009.
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Dans la mise en forme à chaud des composants en acier, les conditions de frottement àl'interface pièce/outil sont sévères en particulier à cause des niveaux de températures (850°C-1250 ℃) et des charges appliquées dans ces opérations. Dans ces conditions de mise en forme,en plus du film lubrifiant, une couche d’oxyde se crée à l’interface pièce/outil qui va perturberles conditions de contact. Les objectifs de cette thèse sont non seulement d'analyser l’impacttribologique de la couche d’oxyde sur le procédé de forgeage à chaud, mais aussi d’observerl’interaction oxyde/lubrifiant. Dans le cadre du laboratoire commun SWITLab entre la sociétéMG-Valdunes, le LAMcube et le LAMIH UMR CNRS 8201, la mise en forme d’une roueferroviaire à grande vitesse a été choisie comme application.Les effets rhéologiques de la couche d'oxyde et du film lubrifiant sur l'acier ont étépréalablement estimés au moyen d'essais de compression à chaud à partir de cylindres degéométries standards et de cylindres de géométries Rastegaev. Des essais complémentaires decompression axisymétriques et de traction ont été réalisés afin de déterminer le comportementmécanique de l'outil à des températures relativement basses.Une analyse originale multi-échelle du contact pièce/outil à haute température a ensuiteété développée. Les principaux paramètres de contact ont été extraits, à macro-échelle, parobservation du procédé industriel et par une première modélisation numérique de la mise enforme. Des essais de compression-translation, ainsi que des tests roll-on-disc ont ensuite étéréalisés à méso et micro-échelle, basés sur les conditions de contact déterminées à macroéchelle.Les essais de compression-translation ont montré la présence à la fois d’oxydes écraséset incrustés sur la surface des échantillons testés. Au niveau micro-échelle, le phénomène deStick-Slip qui se produit en raison de l'accumulation des oxydes écrasés, transforment lesconditions de contact d'une configuration lubrifiant/oxyde en une condition oxyde/oxyde.Enfin, une simulation par éléments finis du procédé de forgeage à chaud de la roueferroviaire, prenant en compte les caractéristiques thermiques de la couche d'oxyde, lecoefficient de frottement déterminé à échelle méso et le comportement du matériau de l'outil, aété développée. Ce modèle permet de prédire correctement les efforts de forgeage et leremplissage des outilsIn hot-working of steel components, friction conditions at the tool/workpiece interfaceare severe due to the relatively high temperatures (850°C-1250℃) and loads involved in theseoperations. Under these processing conditions, the tool/workpiece interface usually involvesthe presence of an oxide layer and a lubricant film. The objective of this research is to analyzethe tribological effect of the oxide layer and its interaction with the lubricant used. As part ofthe joint SWITLab laboratory bringing together the industrial group MG Valdunes, theLAMcube of Lille and the LAMIH UMR CNRS 8201, the hot forging process of a railwaywheel for high-speed trains was chosen for the analysis.The rheological effect of the oxide layer and lubricant film on the steel were previouslyanalyzed by means of hot compression tests with standard cylinders and cylinders with aRastegaev design. Additionally, axisymmetric compression and tensile tests were carried out inorder to characterize the mechanical behavior of the tool material at relatively low temperatures.An original multi-scale analysis of the billet/tool contact conditions at high temperaturewas then developed. At macro-scale, the main contact parameters were extracted by means ofthe industrial forging process observations and its FE modeling. Then, upsetting-sliding testsas well as roll-on-disc tests were conducted based on the macro-scale contact conditions. Afterthe upsetting sliding both crushed and embedded oxides were found to be present on the crosssection of the tested samples. At the micro-scale level, the stick-slip phenomenon occurs due toaccumulation of the crushed oxides, which transform the interfacial contact conditions from alubricant/oxide configuration to an oxide/oxide condition.Finally, a FE model of the railway wheel hot forging process, taking into account thethermal characteristics of the oxide layer, the coefficient of friction determined at meso-scaleand the behavior of the tool material, has been developed. This model can correctly predict theforging forces and the filling of tools
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Dusserre, Gilles. "Sollicitations thermomécaniques dans un moule en acier inoxydable martensitique moulé au cours du cycle de pressage de verre." Toulouse 3, 2006. http://www.theses.fr/2006TOU30216.
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Le procédé de pressage de verre consiste à mettre en forme une paraison de verre par écrasement entre deux outils. L'utilisation de moules en acier inoxydable moulé permet une réduction du prix de revient de l'outillage, mais cela s'effectue au détriment de la durée de vie des moules creux qui s'endommagent à partir de défauts de fonderie, des micro-retassures présentes aux points triples des joints inter-dendritiques. Cette thèse est une contribution à l'amélioration de la durée de vie de ces outillages. L'objectif est de déterminer les sollicitations thermomécaniques dans le moule au cours du cycle de pressage de verre Pyrex®. Les sollicitations sont de deux types : les contraintes dues au gradient de dilatation thermique lors du transfert de chaleur du verre au moule et les contraintes de surface générées par l'écoulement du verre. L'instrumentation d'un moule industriel en vue de la mesure in-situ de températures en service fournit des informations sur le procédé (temps de cycle, températures de service…) et permet, par méthode inverse, d'estimer le flux de chaleur reçu ou cédé par le moule au cours du cycle. Une loi viscoélastique en grandes déformations est proposé et identifié à partir d'essais de compression d'échantillons cylindriques de verre. Le procédé industriel de mise en forme est ensuite simulé en utilisant le modèle identifié précédemment dans le but de déterminer les contraintes normales et tangentielles exercées par le verre sur le moule au cours du pressage. Un modèle de comportement est identifié pour prendre en compte l'adoucissement caractéristique des aciers martensitiques lorsqu'ils sont soumis à un chargement mécanique cyclique. Les modèles, mesures et résultats de calculs mentionnés ci-dessus sont enfin utilisés pour calculer l'évolution du champ de contraintes dans le moule au cours du cycle de pressage en tenant compte au mieux des conditions réelles d'utilisation du moule. Cette mise en données est le point de départ d'une étude paramétrique numérique destinée à étudier l'influence des conditions d'utilisation de l'outillage sur les sollicitations thermomécaniques dans le mouleGlass pressing process is a forming process in which a glass gob is squeezed between two tools. The use of cast stainless steel moulds instead of wrought steel allows a decrease of the tooling costs, but the life time of the hollow mould is consequently decreased. The damages usually take place at the triple junction of dendrites. This thesis is a contribution to the improvement of these tools life time. The aim is to determine the thermomechanical loads of the mould during a glass pressing cycle. Two types of loading exist : the thermal stresses caused by the gradient of thermal dilatation caused by the heat transfer at the glass and mould interface and the superficial stresses caused by the flow of the glass along the surface of the die. An instrumentation of an industrial mould has been realized in order to measure the temperatures in the industrial context and inform about the process (time cycle, use temperature…). An inverse method has been used to estimate the heat flux density at the surface of the tool during the cycle. A high strain viscoelastic law is proposed and identified from compression tests with cylindrical glass samples. The industrial forming process is then simulated using this new rheological law in order to determine the normal stresses on the mould while pressing
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Cabrol, Elodie. "Étude et compréhension des mécanismes d'endommagement de surface de matrices de forgeage à chaud rechargées." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2015. http://www.theses.fr/2015EMAC0012.
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Dans le domaine du forgeage à chaud de pièces aéronautiques, les matrices en acier sont couramment rechargées, sur quelques millimètres d’épaisseur, par un alliage base cobalt (Stellite 21) déposé par procédé de soudage à l’arc (MIG). Dans le cadre de ce travail de thèse, ce rechargement « classique» est comparé à des rechargements Stellite 21 et Stellite 6 déposés par deux procédés émergents dans ce domaine, le PTA et le LASER. L’objectif est d’apporter des éléments de compréhension aux mécanismes d’endommagement de surface, notamment par écoulement plastique, de ces différents rechargements afin de dégager des voies d’amélioration pour augmenter la durée de vie des matrices. Pour cela, des essais tribologiques (semi-industriels et laboratoire) ont été mis en œuvre pour créer des endommagements de surface comparables à ceux observés sur matrices industrielles. Associées à ces essais, des investigations microstructurales, structurales et mécaniques multi-échelles ont été réalisées (traction, flexion, microdureté, MO, MEB, MEB-STEM, DRX, EBSD). Selon les couples « nuance/procédé » de rechargement, des mécanismes de déformation plastique par glissement des dislocations parfaites et par transformation de phase CFC en HC ont été identifiés. L’activation de ce dernier a pu être reliée à la température de transformation allotropique CFC/HC du cobalt. Cette température dépend à la fois (i) des éléments d’addition, variant en fonction de la nuance déposée (Cr, C,...), (ii) de la dilution (variation de la teneur en Fe) liée aux paramètres de soudage et (iii) du nombre de couches déposées. De plus, une influence significative de la transformation de phase sur l’évolution du coefficient de frottement a été mise en évidence. En effet, dans le cas où la transformation de phase n’est pas observée, le coefficient de frottement est stable durant l'essai alors qu'une chute de la courbe de coefficient de frottement a été reliée avec la transformation de phase CFC en HC. Parallèlement, l'écoulement plastique des dendrites est observé en extrême surface sur quelques dizaines de micromètre d'épaisseur dans la direction de glissement. Cet écoulement est associé à une forte texturation morphologique et cristallographique de la phase identifiée (CFC ou HC), avec une orientation des plans de plus grande densité atomique parallèlement à la surface de glissement. Les résultats montrent également que sous sollicitations tribologiques, un important durcissement est observé en surface (jusqu'à 90%) et une corrélation a pu être établie entre l'augmentation de la microdureté et le taux de déformation plastiqueIn the field of hot forging of aeronautical parts, the steel dies are commonly hardfaced, on few millimeters thick, by a cobalt-based alloy (Stellite 21) deposited by arc welding (MIG). As part of this thesis, this "classic" hardfacing is compared to Stellite 21 and Stellite 6 hardfacings deposited by two emerging processes in this area, the PTA and the LASER one. The objective is to assess surface damage mechanisms, especially induced by plastic strain, of these various hardfacings. Tribological tests (laboratory and semi-industrial) were used to create surface damage comparable to those observed in industrial dies. Associated with these tests, multiscale microstructural, structural and mechanical investigations have been performed (tensile, bending, microhardness, OM, SEM, STEM, XRD, EBSD). According to the « material/process » couple, plastic strain mechanisms by perfect dislocation glide and by FCC to HCP phase transformation have been identified. The activation of the latter has been connected to the temperature of the allotropic phase transformation (FCC/HCP) in cobalt. This temperature depends on (i) the alloying elements, varying according to the deposited grade (Cr, C, ...), (ii) the dilution (Fe content evolution) connected to the welding parameters and (iii) the number of deposited layer. Moreover, a significant influence of the phase transformation on the evolution of the friction coefficient has been evidenced. Indeed, if the phase transformation is not observed, the friction coefficient is stable during the test, while a drop of the friction coefficient curve is connected with the FCC to HCP phase transformation. Moreover, the plastic flow of dendrites is observed at the extreme surface, on a few tens of micrometres in thickness, in the direction of sliding. It is associated with a high morphologic and crystallographic texturing of the identified phase (FCC or HCP), with the highest atomic density planes mostly oriented parallel to the sliding surface. The results also show that, under tribological laodings, a significant hardening is observed on the surface (up to 90%) and a correlation has been established between the increase in the microhardness and the plastic deformation ratio
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Ching-Yuan, Huang, and 黃慶淵. "Effects of Thermomechanical Processes on the transformation of." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/18020687191621176223.
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博士國立臺灣大學
材料科學(工程)研究所
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In this work,a series of thermomechanical processes had been carried out in the deformation dilatometer in order to study the effects of prior compressive deformation on the transformation behavior of ULCB steels.It is found that prior deformation of austenite significantly enhances the bainitic transformation.At the same cooling rate the specimen with the prior deformation has a higher bainite start temperature (Bs) than the specimen without the prior deformation; in addition , the difference of Bs temperature becomes much larger at the higher cooling rate.The strain energy accumulated by the compressive deformation the driving force for bainitic transformation.Hence,the formation of bainitic ferrite can proceed further even until the content of carbon of the austenite exceed To'' curve boundary,and the volume fraction of bainitic ferrite is expected larger.A analysis has been proposed to explain the experimental results relating to the effect of prior deformation of austenite.On the other hand, an isothermal experiment has been utilized to investigate the stability of the deformed austenite.It is suggested that the kinetics of precipitation of Nb(C,N) in deformed austenite influences the hardenbility of bainite in local regions of the austenite matrix. This reason can explain why the deformed austenite grains produce finer allotriomorphic ferrite grains in a relatively slow cooling condition.
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"Improvement of the mechanical properties of TRIP-assisted multiphase steels by application of innovative thermal or thermomechanical processes." Université catholique de Louvain, 2008. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-08232008-100716/.
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Sob, Peter Baonhe. "Modelling stain rate sensitive nanomaterials' mechanical properties: the effects of varying definitions." Thesis, 2016. http://hdl.handle.net/10352/332.
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M. Tech. (Mechanical Engineering, Faculty of Engineering and Technology): Vaal University of TechnologyPresently there exist a lot of controversies about the mechanical properties of nanomaterials. Several convincing reasons and justifications have been put forward for the controversies. Some of the reasons are varying processing routes, varying ways of defining equations, varying grain sizes, varying internal constituent structures, varying techniques of imposing strain on the specimen etc. It is therefore necessary for scientists, engineers and technologists to come up with a clearer way of defining and dealing with nanomaterials’ mechanical properties. The parameters of the internal constituent structures of nanomaterials are random in nature with random spatial patterns. So they can best be studied using random processes, specifically as stochastic processes. In this dissertation the tools of stochastic processes have been used as they offer a better approach to understand and analyse random processes. This research adopts the approach of ascertaining the correct mathematical models to be used for experimentation and modelling. After a thorough literature survey it was observed that size and temperature are two important parameters that must be considered in selecting the relevant mathematical definitions for nanomaterials’ mechanical properties. Temperature has a vital role to play during grain refinement since all severe plastic deformation involves thermomechanical processes. The second task performed in this research is to develop the mathematical formulations based on the experimental observation of 2-D grains and 3-D grains deformed by Accumulative Roll-Bonding and Equal Channel Angular Pressing. The experimental observations revealed that grains deformed by Accumulative Roll-Bonding and Equal Channel Angular Pressing are elongated when observed from the rolling direction, and transverse direction, and equiaxed when observed from the normal direction. In this dissertation, the different experimental observations for the grain size variants during grain refinement were established for 2-D and 3-D grains. This led to the development of a stochastic model of grain-elongation for 2-D and 3-D grains. The third task was experimentations and validation of proposed models. Accumulative Roll-Bonding, Equal Channel Angular Pressing and mechanical testing (tensile test) experiments were performed. The effect of size on elongation and material properties were studied to validate the developed models since size has a major effect on material’s properties. The fourth task was obtaining results and discussion of theoretical developed models and experimental results. The following facts were experimentally observed and also revealed by the models. Different approaches of measuring grain size reveal different strains that cannot be directly obtained from plots of the corresponding grain sizes. Grain elongation evolved as small values for larger grains, but became larger for smaller grains. Material properties increased with elongation reaching a maximum and started decreasing as is evident in the Hall-Petch to the Reverse Hall-Petch Relationship. This was alluded to the fact that extreme plastic straining led to distorted structures where grain boundaries and curvatures were in “non-equilibrium” states. Overall, this dissertation contributed new knowledge to the body of knowledge of nanomaterials’ mechanical properties in a number of ways. The major contributions to the body of knowledge by his study can be summarized as follows: (1) The study has contributed in developing a model of elongation for 2-D grain and 3-D grains. It has been generally reported by researchers that materials deformed by Accumulative Roll-Bonding and Equal Channel Angular Pressing are generally elongated but none of these researchers have developed a model of elongation. Elongation revealed more information about “size” during grain refinement. (2) The Transmission Electron Microscopy revealed the grain shape in three directions. The rolling direction or sliding direction, the normal direction and the transverse direction. Most developed models ignored the different approaches of measuring nanomaterials’ mechanical properties. Most existing models dealt only with the equivalent radius measurement during grain refinement. In this dissertation, the different approaches of measuring nanomaterials’ mechanical properties have been considered in the developed models. From this dissertation an accurate correlation can be made from microscopy results and theoretical results. (3) This research has shown that most of the published results on nanomaterials’ mechanical properties may be correct although controversies exist when comparing the different results. This research has also shown that researchers might have considered different approaches to measure nanomaterials’ mechanical properties. The reason for different results is due to different approaches of measuring nanomaterials’ mechanical properties as revealed in this research. Since different approaches of measuring nanomaterials’ mechanical properties led to different obtained results, this justify that most published results of nanomaterials’ mechanical properties may be correct. This dissertation revealed more properties of nanomaterials that are ignored by the models that considered only the equivalent length. (4) This research has contributed to the understanding of nanomaterials controversies when comparing results from different researchers.
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Obadele, Babatunde Abiodun. "Tribocorrosion mechanisms in laser deposited titanium-based smart composite coatings." 2014. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001713.
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D. Tech. Chemical, Metallurgical and Materials Engineering.Aims to produce and improve the tribocorrosion property of Ti6Al4V by means of laser surface cladding with Ni and ZrO2. The results of this study would be useful for the design of high performance components for chemical and oil industry and potential applications in other engineering fields. The aim would be achieved through the following objectives: 1. Synthesize and characterise Ti, Ti-Ni and Ti-Ni-ZrO2 admixed powders. 2. Explore the feasibility of laser surface treatment of Ti6Al4V with Ti, Ti-Ni and Ti-Ni-ZrO2. 3. Investigate possible metallurgical interactions and phenomenon during and after laser surface cladding of the composite. 4. Evaluate the microstructural and mechanical properties of Ti based composites in terms of hardness. 5. Analyze the interaction between wear and corrosion wear as well as tribocorrosion resistance of the alloys and composites after laser surface cladding in 3.5 % NaCl and 1M H2SO4 environments.
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Daly, Matthew. "Thermomechanical response of laser processed nickel-titanium shape memory alloy." Thesis, 2012. http://hdl.handle.net/10012/6606.
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The exciting thermomechanical properties of nickel-titanium shape memory alloys have sparked significant research efforts seeking to exploit their exotic capabilities. Until recently, the performance capabilities of nickel-titanium devices have been inhibited by the retention of only one thermomechanical characteristic. However, laser processing technology promises to deliver enhanced material offerings which are capable of multiple functional responses. Presented in this thesis, is an investigation of the effects of laser processing on the thermomechanical behaviour of nickel-titanium shape memory alloys. In the context of this work, laser processing refers to removal of alloy constituents, as in the case of laser ablation, or alternatively, addition of elements through laser alloying.
The effects of laser ablation on the composition, crystallography and phase transformation temperatures of a nickel-titanium strip have been studied. Application of laser energy was shown to ablate nickel constituents, induce an austenite-martensite phase change and cause an increase in phase transformation onset temperatures, which correlated well with reported findings. Laser processing of a nickel-titanium wire was shown to locally embed an additional thermomechanical response which manifested as unique shape memory and pseudoelastic properties.
Localized alloying of ternary species via laser processing of nickel-titanium strip was investigated. Synthesis of a ternary shape memory intermetallic within the laser processing region was achieved through melting of copper foils. Results from thermoanalytical testing indicated that the ternary compound possessed a higher phase transformation temperature and reduced transformation hysteresis in comparison to the reference alloy. Indentation testing was used to demonstrate the augmented thermomechanical characteristics of the laser processed shape memory alloy.
In order to demonstrate the enhanced functionality of laser processed nickel-titanium shape memory alloys, a self-positioning nickel-titanium microgripper was fabricated. The microgripper was designed to actuate through four different positions, corresponding to activation of three embedded shape memory characteristics. Thermoanalytical and tensile testing instrumentations were used to characterize the thermomechanical performance of the laser processed nickel-titanium microgripper. Results indicated that each of the laser processed microgripper components possessed unique mechanical and shape memory recovery properties.
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Ferris, William F., Terry R. McNelley, and Stephen J. Hales. "The age hardening response of thermomechanically processed Al-Mg-Li alloys." Thesis, 1987. http://hdl.handle.net/10945/22597.
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Andrews, James N. Jr. "A calorimetric study of the microstructures of a thermomechanically processed Al-10.0% Mg-0.1% Zr alloy." Thesis, 1986. http://hdl.handle.net/10945/21701.
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(10723848), Dan Feng. "MECHANICS, VIBRATIONS, AND TENSION MEASUREMENT OF THIN WEBS IN ROLL-TO-ROLL MANUFACTURING FOR FLEXIBLE AND PRINTED ELECTRONICS." Thesis, 2021.
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Roll-to-roll processes provide a low-cost and high-throughput scheme for scalable flexible devices manufacturing. Multiple processes are used in roll-to-roll manufacturing, such as functional printing, evaporation/drying, UV curing, hot embossing, laser/heat annealing, laser ablation, plasma/ chemical growth, and sputtering. These processes change the web temperature field and/ or local properties. In addition, residual stresses by the process and web tension can destabilize the process and lead to wrinkling or undesirable performance of the products.
This dissertation investigates three different multi-physics problems relevant to the roll-to-roll processes, which are web thermomechanics, air-coupled web vibrations, and the measuring of nonuniform web tension. First, a mathematical model for predicting the in-plane temperature and heat induced stress distributions in a flexible, axially moving web under arbitrary shape of heat flux is presented. The computational approach is validated on experiments performed on moving paper and PET webs with infrared laser heating source. Second, a closed-form, semi-analytical, universal hydrodynamic functions is developed to accurately predict the lowest symmetric and anti-symmetric transverse frequency responses for any uniaxially tensioned web of arbitrary material and aspect ratio used in roll-to-roll processes with the surrounding air acting as distributed added mass. Experimental validation is carried out by using pointwise laser measurements of acoustically excited webs with different pre-tensions, web materials, and aspect ratios. Finally, we develop and test a non-contact resonance method and a gentle contact stiffness mapping method based on the first principles mechanical models of a tensioned plate to accurately measure the average web tension and its linear variation for a wide range of web properties, web path, web tension, measurement configurations, and environmental conditions. The two methods are cross-validated on a stationary test stand and the non-contact resonance method is used to study the web tension distribution within a commercial roll-to-roll system.