Dissertations / Theses on the topic 'Contributions in materialism'
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Helm, M., W. Möller, E. Wieser, H. U. Jäger, and J. von Borany. "Institute of Ion Beam Physics and Materials Research; Annual Report 2000." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-29752.
Full textHelm, M., W. Möller, E. Wieser, H. U. Jäger, and J. von Borany. "Institute of Ion Beam Physics and Materials Research; Annual Report 2000." Forschungszentrum Rossendorf, 2001. https://hzdr.qucosa.de/id/qucosa%3A21802.
Full textMaguire, John F. "Contributions to materials science and engineering." Thesis, Ulster University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515891.
Full textSutton, Bradley (Bradley Jordan). "Human error contribution to nuclear materials-handling events." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41686.
Full textIncludes bibliographical references (leaves 40-41).
This thesis analyzes a sample of 15 fuel-handling events from the past ten years at commercial nuclear reactors with significant human error contributions in order to detail the contribution of human error to fuel-handling activities, emphasizing how latent conditions can directly contribute to events. In particular, procedural inaccuracies often create conditions that lead to the development of errors related to maintenance work practices. This would be of significant concern for a pre-closure safety assessment for a geologic repository for spent nuclear fuel and high-level radioactive waste, where many fuel-handling work activities would be performed. Specific emphasis is placed on fuel movement activities and control of ventilation systems, which could significantly impact worker and public health and safety in the case of a fuel-handling accident.
by Bradley Sutton.
S.B.
Carbajo, San Martín Jesús. "Contributions to the study of the acoustic properties of porous materials." Doctoral thesis, Universidad de Alicante, 2018. http://hdl.handle.net/10045/80027.
Full textMurray, Keith Russell. "Electrochromic materials their contribution to sustainability in the built environment /." Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=26226.
Full textGeppert, Benjamin [Verfasser]. "Contributions to the development of novel thermoelectric materials and systems / Benjamin Geppert." Hannover : Technische Informationsbibliothek (TIB), 2017. http://d-nb.info/1131742184/34.
Full textNelias, Daniel. "Contribution à l'étude des roulements." [S.l.] : [s.n.], 1999. http://csidoc.insa-lyon.fr/these/1999/nelias/index.html.
Full textGu, Sijia. "Contribution to broadband local characterization of materials by near-field microwave microscopy." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10175/document.
Full textNear-field microwave microscopes are emerging instruments for materials characterization. In this work, a home-made near-field microwave microscope is first described and analyzed in terms of resolution performance and frequency band of operation. Then, it is applied to the characterization of a large variety of materials such as metals, semiconductors, dielectrics, liquids and 2D nanomaterials. The system is based on an interferometric technique to improve the measurement sensitivity in the entire frequency range of operation spanning from 2 to 18 GHz. The sensitivity and the different operating modes available (contact, non-contact, liquid environment) allow addressing a large variety of application fields. The instrument allows a sub-wavelength lateral resolution which is more than two orders of magnitude smaller than the operating wavelength, opening the way to a local characterization. The cavity perturbation and transmission line approaches have been used to extract the electromagnetic properties of materials. In particular dielectric properties of saline aqueous solutions and complex impedance of graphene have been investigated in a broad frequency band. It provides a quantitative analysis of material properties in a non-destructive manner to address numerous applications in many scientific fields. Finally, all the results together show that the interferometer-based near-field microwave microscope has the potential to become an important metrology tool for characterizations in micro- and nano-electronics
Megevand, Benjamin. "Contribution of atomic force microscopy to local mechanical characterization of polymer materials." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI023/document.
Full textThis thesis work aims to show how nanomechanical characterizations in AFM can provide a better understanding of structure-properties relationships in polymers. In this context, the technique itself and the associated theoretical basis are first analyzed to implement a robust methodology in order to perform reproducible, quantitative measurements. Two main studies are carried out around a common topic: the understanding of the interactions between biopolymers and ionic liquids (ILs). First, the compatibilization of PBAT/PLA blends by two different ILs (namely il-Cl and il-TMP) is studied. Adhesion and local modulus mappings evidence the resulting microstructures, and highlight that the compatibilization mainly results from a modification of the PBAT/PLA interface, becoming a coherent interphase. This is due to specific interaction with the cations and the anions of each IL, which are preferentially located at those interphases. The second study is more specifically about the understanding of the modification of semicrystalline PBAT by the addition of small amounts of the same ionic liquids. While il-TMP forms dissipative nodules dispersed into the matrix with a cohesive interphase between both, il-Cl, miscible into the amorphous phase of PBAT, amplifies the chain mobility in the bulky MAF (i.e. Mobile Amorphous Fraction) and hinders it in the confined RAF (i.e. Rigid Amorphous Fraction), leading to interesting macroscopical properties modifications. More than showing some interesting capabilities of ILs as additives in polymers, those results also show an outstanding potential of AFM nanomechanical mappings for the in-deep understanding of structure-properties relationships in materials
Deng, Xinwei. "Contributions to statistical learning and statistical quantification in nanomaterials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29777.
Full textCommittee Chair: Wu, C. F. Jeff; Committee Co-Chair: Yuan, Ming; Committee Member: Huo, Xiaoming; Committee Member: Vengazhiyil, Roshan Joseph; Committee Member: Wang, Zhonglin. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Cruz, Matías Irving Alberto. "Contribution to structural parameters computation: volume models and methods." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/144943.
Full textEl Bio-Diseño Asistido por Computadora (Bio-CAD), y la experimentacion in-silico est an teniendo un creciente interes en aplicaciones biomedicas, en donde se utilizan datos cientificos provenientes de muestras reales para calcular par ametros estructurales que permiten evaluar propiedades físicas. Las tecnologías de adquisicion de imagen no invasivas como la TC, TC o IRM, y el crecimiento constante de las prestaciones de las computadoras, permiten la adquisicion, procesamiento y visualizacion de datos científicos con creciente grado de complejidad. El calculo de parametros estructurales esta basado en la existencia de dos fases (o espacios) en la muestra: la solida, que puede corresponder al hueso o material, y la fase porosa o vacía, por tanto, tales muestras son representadas como volumenes binarios. El modelo de representacion mas comun para estos conjuntos de datos es el modelo de voxeles, el cual es una extension natural a 3D de los mapas de bits 2D. En esta tesis se utilizan el modelo Extreme Verrtices Model (EVM) y un nuevo modelo propuesto, the Compact Union of Disjoint Boxes (CUDB), para representar los volumenes binarios en una forma mucho mas compacta. El modelo EVM almacena solo un subconjunto ordenado de vertices de la frontera del objeto mientras que el modelo CUDB mantiene una lista compacta de cajas. En esta tesis se proponen metodos para calcular los siguientes parametros estructurales: distribucion del tamaño de los poros, conectividad, orientacion, esfericidad y redondez. La distribucion del tamaño de los poros ayuda a interpretar las características de las muestras porosas permitiendo a los usuarios observar los rangos de diametro mas comunes de los poros mediante picos en un grafica. La conectividad es una propiedad topologica relacionada con el genero del espacio solido, mide el nivel de interconectividad entre los elementos, y es un indicador de las características biomecanicas del hueso o de otros materiales. La orientacion de un objeto puede ser definida por medio de angulos de rotacion alrededor de un conjunto de ejes ortogonales. La esfericidad es una medida de que tan esferica es una partícula, mientras que la redondez es la medida de la nitidez de sus aristas y esquinas. En el estudio de estos parametros se trabaja con muestras reales escaneadas a alta resolucion que suelen generar conjuntos de datos enormes, los cuales requieren una gran cantidad de memoria y mucho tiempo de procesamiento para ser analizados. Por esta razon, se presenta un nuevo metodo para simpli car vol umenes binarios de una manera progresiva y sin perdidas. Este metodo genera una secuencia de niveles de detalle de los objetos, en donde cada objeto es un volumen englobante de los objetos previos. Ademas de ser utilizado como apoyo en el calculo de parametros estructurales, este metodo puede ser de utilizado en otras tareas como transmision progresiva, deteccion de colisiones y calculo de volumen de interes. Como parte de una investigacion multidisciplinaria, se han desarrollado dos aplicaciones practicas para calcular parametros estructurales de muestras reales. Un software para la deteccion automatica de puntos de viscosidad característicos en muestras de rocas de basalto y vidrios, y una aplicacion para calcular la esfericidad y redondez de formas complejas en un conjunto de datos de sílice.
Hofmeyr, Andrew Mark. "Factors contributing to successful supplier client collaboration in South African companies." Diss., University of Pretoria, 2006. http://hdl.handle.net/2263/23638.
Full textDissertation (MBA)--University of Pretoria, 2006.
Gordon Institute of Business Science (GIBS)
unrestricted
Dufalla, Michele (Michele Helene). "Processing factors contributing to growth and decline in the steel industry." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/44825.
Full textIncludes bibliographical references (p. 16-17).
During the second half of the twentieth century, a technological shift occurred in the steel industry. A different mix of refining and melting furnaces were used, with increasing use being made of basic oxygen and electric arc furnaces as compared to the basic open hearth. Additionally, continuous casting began to replace ingot casting. Iron ore price, scrap steel price and electricity price were examined as predictor variables for these technological shifts. For the furnace shift, iron ore price and scrap steel price seemed to play a role, though much smaller than the role of time. For the casting shift, only time seemed to be correlated.
by Michele Dufalla.
S.B.
Afsordegan, Arayeh. "A contribution to multi-criteria decision making in sustainable energy management based on fuzzy and qualitative reasoning." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/333328.
Full textLos problemas de la energía son problemas graves causados por los recursos limitados y las actividades humanas como la deforestación, contaminación del agua y otras prácticas con efectos a largo plazo. Estas prácticas tienen un gran impacto ambiental y dan lugar al efecto invernadero, que ocasiona el calentamiento global y cambio climático. Los problemas complejos implican generalmente múltiples criterios contradictorios y múltiples decisores. Requieren el uso de métodos toma de decisiones multicriterio para evaluar diferentes tipos de variables con respecto a factores de sostenibilidad, incluyendo aspectos conflictivos económicos, tecnológicos, sociales y ambientales. Estos factores, especialmente los sociales, no siempre son precisos, dado que la imprecisión y la incertidumbre son características del mundo real. Por lo tanto, con el fin de proporcionar datos útiles a partir de evaluaciones de expertos, en esta tesis se presenta un nuevo método de toma de decisiones multicriterio, como una herramienta útil en la planificación de la energía. Este método permite a los decisores utilizar valores con imprecisión en todas las etapas de la toma de decisiones. En esta tesis se ha realizado una revisión exhaustiva de la literatura sobre el análisis de la decisión multicriterio y la planificación de la energía. En primer lugar, se presenta el estudio a fondo de los criterios e indicadores en el área de planificación de la energía. Se introducen algunos de los métodos más conocidos de toma de decisiones multicriterio y sus aplicaciones. En estos problemas, a menudo es difícil obtener valores numéricos exactos para algunos criterios e indicadores. Para superar esta deficiencia, la integración de técnicas de razonamiento cualitativo en métodos de decisión multicriterio permite representar la incertidumbre, emular el trabajo de seres humanos cualificados y manejar situaciones vagas. Este estudio propone un método TOPSIS cualitativo (Q-TOPSIS), que es un nuevo método de ranking de alternativas para la toma de decisiones multicriterio en grupo. Este nuevo método, toma en cuenta los datos cualitativos proporcionados por los juicios lingüísticos individuales de los decisores sin necesidad de previa agregación o normalización. Se presentan tres aplicaciones del método propuesto en la planificación de la energía. En el primer caso, se presenta la aplicación del método Q-TOPSIS en un caso práctico de selección de alternativas de energías renovables. Una simulación de treinta escenarios utilizando diferentes pesos demuestra que la simplicidad y la interpretabilidad de Q-TOPSIS proporcionan una mejora general del TOPSIS clásico en el caso de evaluaciones ordinales. En segundo lugar, se presenta un estudio de un caso real para decidir el lugar apropiado para ubicación de parques eólicos en una zona de Cataluña. En este caso, las distintas alternativas fueron propuestas en base a las preferencias de los actores sociales sobre la ubicación de los parques eólicos deseados en una región entre los condados del Urgell y la Conca de Barberà. El ranking obtenido de las alternativas concluye que la mejor opción es una alternativa que combina dos proyectos iniciales diferentes. La utilización del método propuesto para la decisión en grupo permite manejar un alto grado de conflicto entre conceptos multidimensionales y simplifica las mediciones de los expertos. Por último, se presenta una aplicación a la eficiencia de la energía en edificios mediante la plataforma SEMANCO (Herramientas semánticas para la reducción de carbono en la planificación urbana) para evaluar la eficiencia de la energía y las emisiones de CO2 de planes urbanísticos proyectados en la ciudad de Manresa. En este caso estudio, la aplicación de Q-TOPSIS ayuda a los decisores a realizar el ranking de los diferentes proyectos con respecto a criterios cuantitativos y cualitativos multi-granulares y ofrece resultados fácilmente inteligibles para los decisores.
Milenkovic, Nenad. "Contribution to the development of an additive for bulk waterproofing of cement-based materials." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/262355.
Full textDoctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
Macarulla, Martí Marcel. "Contributions to rework prevention in construction projects." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/134697.
Full textSpong, Andrew. "The repertory of the Rose : a contribution to an historical materialist critique of early modern English drama." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421202.
Full textKlande, Tobias [Verfasser]. "Contributions to the development of oxygen-transporting materials as ceramic membranes for gas separation / Tobias Klande." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2013. http://d-nb.info/1035470306/34.
Full textKaraca, Mehmet. "Contribution To The Development Of Implicit Large Eddy Simulations Methods For Compressible Turbulent Flows." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12614063/index.pdf.
Full text32×
128 to 256×
256×
1024, using a 5th order WENO scheme. Physical LES are carried out with the Smagorinsky and the Selective Structure Function models associated to molecular diffusion. Implicit LES are performed with and without molecular diffusion, by solving either the Navier-Stokes or the Euler equations. In the nonreacting case, the Smagorinsky model is too dissipative. The Selective Structure Function leads to better results, but does not show any superiority compared to ILES, whatever the grid resolution. In the reacting case, a molecular viscous cut-off in the simulation is mandatory to set a physical width for the reaction zone in the ILES approach, hence to achieve grid-convergence. It is also found that ILES/LES are less sensitive to the inlet conditions than the RANS approach. The first chapter is an introduction to the context of this study. In the second chapter, the governing equations for multispecies reacting flows are presented, with emphasis on the thermodynamic and transport models. In the third chapter, physical LES equations and explicit sub-grid modeling strategies iv are detailed. Some properties of the numerical scheme are also investigated. In chapter four, the numerical scheme and some aspects of the solver are explained. Finally, non-reacting and reacting numerical experiments are presented and the results are discussed.
Kanj, Hassan. "Contribution to risk analysis related to the transport of hazardous materials by agent-based simulation." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT060/document.
Full textDangerous Goods Transport (DGT) represents a source of danger to the crossed areas. This danger can produce serious consequences for the environment, property or human beings. Due to the importance of these products (gasoline, first material, medicines) in everyday life and the increasing demand on these products, it is important to analyze and assess the level of risk related to DGT in order to minimize it. This risk depends on the followed route, the quantity of transported products, the time of day, the weather conditions and the population density of crossed areas. It is characterized by the targets that are exposed for a given time, and by the risk level that varies with time and space.The purpose of this thesis is to evaluate and assess the risk level related to an accident and especially risk related to DGT. Several methods to calculate the risk level, related to DGT, have been proposed in the literature. In most of these methods, the temporal aspect has not been taken explicitly into account in spite of its importance. Indeed, the volume of traffic, the building occupancy rates or weather conditions could greatly change depending on the time of day.The first part of this thesis summarizes the state of the art on risk analysis. Next, we present two approaches for assessing risk related to DGT systems: the former serves to evaluate the risk level of an accident and it is based on Monte Carlo Simulation, while the latter aims at assessing the risk level along a trajectory.The second part focuses on the temporal aspect and due to the complexity of our system (several entities, distributed systems, entities with multiple levels of abstraction, etc.), we are turned to a multi-agent simulation approach and we define a meta-model agent with a risk facet, a generic facet. This facet allows us to represent the risk analysis and failure propagation in an agent model.The third part of this thesis illustrates a proposed approach to assess the risk level related to DGT. Firstly, we propose formulas to assess the accident frequency and severity. Then, we present the implementation of both simulation approaches proposed in the first part using the agent based model proposed in the second part. Secondly, as decision-making is affected by the economic and temporal aspects (cost of shipping and travel time), we are facing a multi-criteria decision making problem (MCDM). In addition, to take into account the fact that several parameters used in risk analysis are uncertain, we have used fuzzy numbers. Next, we have proposed an approach, which integrates MCDM methods with fuzzy numbers, to identify the best route for DGT among a set of alternatives. The purpose of this approach is to provide decision support for decision makers such as, public authorities and emergency services in case of emergency.A simulation tool is developed in Eclipse, which allows us to analyze the level of risk and realizes maps that show the instantaneous position of the truck with the impacted areas in the case of accident. This work is a part of the GEOTRANS-MD project
Rahoui, Hafsa. "Contribution to understanding the action of shrinkage reducing admixtures in cementitious materials : experiments and modelling." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1166.
Full textConcrete shrinkage and the cracking that it causes represent a fundamental problem in construction, which may have consequences on the structutal, aestheticand durability aspects. Shrinkage Reducing Admixtures (SRA) are organic chemicals that can be used to minimize the drying shrinkage of Portland-cement-based concretes.The major objective of this work is to set up a methodology for observing and ideally also modeling the behavior of the SRA during the hydration and drying processes. So the PhD will include experimental work able to highlight some features missing in the litterature and to develop a new methodology for investigating the SRA mechanism. The PhD will also include a modeling part involving poromechanics and physico-chemical theories
Li, Yan. "Contribution of ceramic food contact materials to the exposure of consumers to metals in Belgium." Doctoral thesis, Universite Libre de Bruxelles, 2018. https://dipot.ulb.ac.be/dspace/bitstream/2013/277640/4/text.pdf.
Full textLes articles en céramique à vocation alimentaire sont régulés en Europe par la Directive 84/500/EEC, qui établit les limites maximale autorisées de plomb et de cadmium cédées par ces objets en céramiques, sous des conditions d'essai décrites dans la Directive. Depuis 1984, date de la Directive, les données scientifiques concernant les effets néfastes du Pb et du Cd mais aussi d'autres métaux sur la santé se sont accumulés. Une révision de la Directive est donc en discussion, avec pour objectif de réduire les limites autorisée en Pb et Cd, et d'en étendre la portée à d'autres éléments. Dans ce contexte, la présente thèse discute le contenu de la Directive en vue d'une protection adéquate des consommateurs. Ce travail comprend une partie expérimentale dédiée à la cession du Pb, du Cd et d'autres éléments par des objets en céramique, une étude d'exposition au Pb et au Cd, et une analyse de risques. Sur cette base, de nouvelles limites autorisées sont proposées.Dans la partie expérimentale, une méthode analytique permettant la quantification simultanée du Pb, du Cd et jusqu'à 17 autres éléments a été implémentée et validée. Afin d'évaluer à quel point les conditions d'essai de la Directive sont représentatives d'une utilisation réelle des céramiques à usage alimentaire, l'influence de différents paramètres sur la quantité de métaux cédés a été examinée en détail. En particulier, la nature du simulant alimentaire (acide acétique vs. acide citrique), le pH, la température et les modes de chauffage ont été étudiés, de même que des essais de migration successifs, plus à même de représenter l'usage répété des céramiques dans la vie courante. Le protocole de la Directive actuelle est représentatif d'un usage de type remplissage par des liquides chauds (thé, café, soupe). Cependant, pour des usages de type cuisine à plus haute température, les quantités cédées sont beaucoup plus importantes et il est donc suggéré d'établir de nouveaux protocoles représentatif de ces conditions. Un protocole alternatif permettant d'accélérer l'essai de migration à température ambiante est également proposé.A la suite de cette partie expérimentale, une étude d'exposition au Pb et au Cd par le biais d'articles en céramique a été effectuée suivant trois approches incrémentales, à savoir une évaluation par criblage, une évaluation déterministe raffinée, et une évaluation probabiliste. Enfin, une analyse de risque intégrant d'autres sources alimentaires d'ingestion de métaux est développée. Une attention particulière a été accordée aux groupes vulnérables tels que les enfants.Sur base de ce travail, de nouvelles limites maximales autorisées sont proposées pour le plomb et le cadmium. En outre, il est proposé d'intégrer l'aluminium, le barium, le fer, le nickel, le lithium, le manganèse, le cobalt, le cuivre, le zinc, le chrome et l'arsenic dans l'objet de la Directive, et des limites autorisées sont proposées pour ces éléments.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Clénet, Jocelyn. "A contribution to the understanding of chemical phenomena occuring during the formation of a biobased resin at high-temperature." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI114.
Full textPiedra-Cueva, Jose Carlos Ismael. "Contribution à l'étude des mécanismes de transport des sédiments cohésifs." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10200.
Full textAmziane, Sofiane. "Contribution à l'étude des matériaux cimentaires à l'état frais." Habilitation à diriger des recherches, Université de Bretagne Sud, 2005. http://tel.archives-ouvertes.fr/tel-00069705.
Full textLe malaxage en camion bétonnière, la pression sur les coffrages, l'étude de la structuration du matériau et enfin une modélisation théorique du comportement expérimental constituent l'ossature des travaux de recherche exposés dans ce rapport.
Les méthodes expérimentales employées ont permis d'investiguer l'évolution de la rhéologie et de la maturation des matériaux cimentaires à travers l'observation de l'état de l'eau dans la matière. L'étude de l'évolution de la pression interstitielle et de la pression totale exercées par une colonne de matériau sur un coffrage, couplée à des expériences de rhéologie, de retrait endogène et de conductivité hydraulique nous a permis de tirer plusieurs enseignements :
o Il est possible de mesurer correctement à l'aide d'une bétonnière portée (camion toupie) les caractéristiques rhéologiques d'un béton, en appliquant les principes de la rhéomètrie rotative.
o Après malaxage et mise en œuvre dans un coffrage, la pression interstitielle et la pression totale des bétons sont égales jusqu'à annulation de la pression totale. Les contraintes effectives sont nulles sur cette phase. Une dépression interstitielle est ensuite observée. L'annulation de la pression interstitielle se produit à rupture des ponts capillaires.
o Le processus physico-chimique d'hydratation du ciment est à l'origine de la chute de pression interstitielle y compris en zone dépressionnaire. La formation des produits d'hydratation induit ensuite l'annulation de la pression interstitielle.
o Dans le cas des bétons, l'augmentation de la concentration granulaire induit une baisse de la pression maximale initiale, comparée à la pression hydrostatique, d'un fluide de masse volumique équivalente. C'est le résultat de la mobilisation des frottements aux parois des coffrages.
o Le comportement des bétons en termes de cinétique de pression interstitielle est calqué sur celui des pâtes de ciment équivalentes tant que la pression totale est positive. Une influence granulaire sur la zone dépressionnaire due à la reprise d'une partie des contraintes par les granulats est en outre enregistrée.
o La chute de pression interstitielle induit un accroissement de la contrainte seuil de cisaillement et du retrait, ainsi qu'une réduction de la conductivité hydraulique.
o L'analyse des variations instantanées de pression interstitielle consécutives à un cisaillement à taux de déformation constante montre un comportement opposé suivant que le milieu est granulaire (sable dense saturé par exemple) ou analogue à un fluide visqueux (pâte de ciment par exemple). La dilatance induit une chute de pression interstitielle (cas des milieux granulaires). A l'opposé, un accroissement de pression interstitielle est observé lors du cisaillement de la pâte de ciment.
o La modélisation de la variation de la pression interstitielle en phase plastique fondée sur l'adaptation et l'intégration d'une équation d'état de l'eau dans le matériau, a montré la prépondérance d'un terme source qui rend compte du changement de l'état de l'eau lors de la phase d'hydratation du ciment. Ce terme est identifié à une gaussienne dont les paramètres sont déterminés par analyse inverse. Les résultats de la simulation sont majoritairement très proches de ceux de l'expérimentation.
Finalement, l'ensemble des résultats obtenus montre qu'à l'aide du seul capteur de pression interstitielle, il est possible de détecter précisément la structuration des matériaux cimentaires. A ce titre, une des applications possibles concerne la détermination d'une valeur discrète du temps de prise.
Une conclusion incluant mon projet de recherches est enfin présentée.
McKean, Christopher R. "Relative contributions of the lumbar spine and pelvis to trunk motion during sagittal plane manual materials handling." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ40429.pdf.
Full textDjofack, Dongfack Jacques. "Contribution à l'étude du comportement thermomécanique d'une résine époxy-amine aux jeunes âges." Phd thesis, Ecole Nationale des Ponts et Chaussées, 1992. http://tel.archives-ouvertes.fr/tel-00869143.
Full textYang, Gang. "Contribution to modelling of magnetoelectric composites for energy harvesting." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066731/document.
Full textCurrently, the "Internet of Everything" (IoE) technologies have attracted significant researchers in the international scientific community. The IoE is based on the idea that identifiable objects are located and controlled via the Internet. To achieve this goal, it is necessary to design embedded systems in millimeter/micrometer scales composed of wireless sensor nodes while overcoming a major drawback of the excessive use of batteries which are limited in lifetime and yield pollutants. The problem calls for the supply of green energy harvesting for wireless sensors. To utilize mechanical vibrations and electromagnetic energy more efficiently, it would be necessary to get simultaneously both energies using materials sensitive to the electromagnetic field and the mechanical vibration such as magnetoelectric materials (ME) that combine the magnetostrictive and piezoelectric effects. Experimental results of ME coefficients from the fabricated ME composites have confirmed the possibility to obtain a few of V/(cm∙Oe) in no-resonant regime and few tens of V/(cm∙Oe) in resonant regime. In case of classical laminate bulk material (Terfenol-D/PZT/Terfenol-D), the delivered powers into optimal impedance are in the order of mW/ cm3. Thus in this context the research work in this thesis focuses on the establishment and assessment of the modelling approaches. The contribution includes analytical numerical methods and a 2D multiphysics finite element method to estimate the performance of the ME materials according to different polarizations and parameters
Wang, Bing-wu. "A study of the role and contribution of amorphous materials in marine soils of eastern Canada /." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74567.
Full textSoil properties and behavior are not only controlled by the quantity, but also by the composition or type of amorphous materials. The mass ratio, defined as Fe$ sb2$O$ sb3$/(Fe$ sb2$O$ sb3$ + SiO$ sb2$) in units of mass, can be used as a parameter to evaluate the effect of amorphous composition. By changing the mass ratio, which in effect changes the composition, soil properties/behavior can be altered. Shear strength, consistency limits and suction all increase with an increase in amorphous content, but vary with mass ratio. Maximum shear strength and minimum consistency limits and suction are observed for soils with amorphous material composed at a critical mass ratio of 0.40. Soil properties are significantly related to the soil's acidity/alkalinity (pH), due directly to the pH dependency of surface charges of amorphous solid particles.
The basic mechanism that governs the soil's performance arises primarily from the very active surface characteristics, i.e. the large surface area and high surface charge, of the amorphous material complex. The roles played by this special soil constituent can be generalized in two functions: water holding capacity and bonding action. While the large surface area necessitates a rise in the soil's water holding capability, the high surface charge enhances the bonding action in-between clay particles. Significant cation bridging and hydrogen bonding, and strong electro-static attractive force established in the silica-iron amorphous complex, especially at the mass ratio 0.40, contribute to the high shear strength observed in the soil.
The laboratory-prepared soil samples showed a good behavioral simulation to the natural marine soils in East Canada and, hence, a much clearer picture for understanding the sensitivity of such soils as Quebec Champlain Sea clays, as well as the general soil problems related to the roles played by the amorphous materials, is achieved. (Abstract shortened by UMI.)
Pittala, Narsimhulu. "Contribution to the Triazole-Based Fe(II) Spin-Crossover (SCO) materials : some achievements and new questions." Thesis, Brest, 2016. http://www.theses.fr/2016BRES0084/document.
Full textIn recent years, the spin-crossover (SCO) materials have attracted much interest because of their potential applications such as sensors or electronic displays; these complexes typically exhibit - via an external disturbance (e.g. temperature, radiation) - a reversible “High Spin (HS) Low Spin (LS)” spin transition. In this context, the present work has focused on the design and the magneto-structural investigations of single crystals of novel FeII SCO systems based on 4-R-1,2,4-triazole ligands including an alkyl spacer - with either (i) inorganic tetracyanometallates ([M(CN)4]2-, M = NiII, PtII, PdII) or (ii) specific organic cyanocarbanions ((tcnsR’)-: 1,1,3,3-tetracyano-2-thioalkylpropenide anions) - in order to ultimately understand the physicochemical origin of the strong cooperativity in such striking materials, but also to rationalize the tuning of the SCO properties. At first, a new 1D polymer [Fe(bntrz)3][Pt(CN)4].H2O (1) salt - exhibiting an abrupt spin transition and an exceptional resilience upon repeated switching - has been synthesized; the accurate single crystal investigations of both HS and LS states of the latter clearly revealed the impact of the longrange interactions on SCO properties in this system. Then, the substitution of the ‘rigid’ [Pt(CN)4]2- tetracyanometallate anion by the more ‘flexible’ (tcnset)- entity lead us to the first example of triazole-based SCO FeII trinuclear neutral complex [Fe3(bntrz)6(tcnset)6] (2) exhibiting a complete one-step spin transition above room temperature. The systematic variation of the R’ substituent from the functionalized (tcnsR’)- anion resulted in two new FeII SCO systems, i.e. the neutral trinuclear complex [Fe3(bntrz)6(tcnspr)6] (3) and the 1D [Fe3(bntrz)8(tcnsme)4](tcnsme)2.4H2O (4) derivative, with distinct structural characteristics and SCO behaviours. Finally, with the purpose to further evaluate the impact of different substituents at the 4th position onto 1,2,4-triazole ligand, two new 3D materials based on the functionalised triazole 2-(3-(4H-1,2,4-triazol-4-yl)propyl)isoindoline-1,3-dione (phtptrz) - {Fe3(μ2-phtptrz)6[μ2-Pt(CN)4]3}.C2H5OH,5.5H2O (5) and {Fe(phtptrz)[Pt(CN)4].H2O} (6) - have been synthesized and characterized; a two-step SCO behaviour is observed only in 5, while 6 shows a characteristic paramagnetic behavior
Kranz, Julian [Verfasser], and M. [Akademischer Betreuer] Elstner. "Methodological contributions to the simulation of charge and energy transport in molecular materials / Julian Kranz ; Betreuer: M. Elstner." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1162544058/34.
Full textHumeau, Corentin. "Contribution to the study of coupling between moisture diffusion and mechanical stress, in high performance marine materials." Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4070/document.
Full textThe aim of the study was to understand the impact of coupling on water diffusion and mechanical stress on marine installations. Moreover, we identified the key phenomena involved during this type of exposure. When we look to these type of applications we can distinguish two type of materials used: one for the structure and another for mooring facilities. The best performing structural materials appear to be composites, while the most effective mooring devices are made with synthetic ropes. Therefore, we decided to investigate both materials with the same method: first the properties uncoupled, second, as semi-coupled behaviours and finally as one coupled phenomenon. The present work highlights the divergences between uncoupled, semi-coupled and coupled behaviours for the two main types of material used for marine and offshore applications. The need to perform coupled tests to dimension the offshore systems is fully justified. Moreover, this study proposes an important number of hypotheses to explain these differences when we test the materials coupled. For these reasons, additional work should be performed on the subject for other types or composites and fibre materials in order to increase the data base on coupled behaviour
Redondo, Foj María Belén. "A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/59457.
Full text[ES] El desarrollo de nuevos materiales poliméricos de mayor complejidad produce un desafío cada vez mayor en el área de las ciencias básicas. La relación entre la estructura y la dinámica molecular resulta de gran importancia para el desarrollo de nuevas tecnologías basadas en estos materiales poliméricos. Así, una mayor comprensión de cómo pequeños cambios en la estructura química afectan a las propiedades de los materiales resulta esencial para el progreso científico y tecnológico. Un análisis en profundidad de la movilidad molecular permite establecer las relaciones estructura-propiedades. Partiendo de esta base, el principal objetivo del presente trabajo es el estudio de la movilidad molecular de dos familias diferentes de materiales poliméricos. Para ello, las técnicas experimentales utilizadas fueron principalmente la Calorimetría Diferencial de Barrido (DSC) y la Espectroscopia de Relajación Dieléctrica (DRS). La primera familia de polímeros caracterizada fue una serie de copolímeros entrecruzados químicamente compuestos por los monómeros Vinilpirrolidona (VP) y Acrilato de Butilo (BA). En primer lugar, se estudió la influencia de la proporción molar de monómero (XVP/YBA) en las propiedades del copolímero. A través de un análisis por Espectroscopia de Infrarrojo por Transformada de Fourier (FTIR), se verificó la existencia de interacciones dipolo-dipolo entre los grupos amida. Mediante el análisis por DSC, DRS y Análisis Dinamomecánico (DMA), se evidenció la influencia de estas interacciones en diferentes parámetros relacionados con la movilidad molecular. En segundo lugar, se analizó el efecto de la densidad de entrecruzamiento en la dinámica molecular de los copolímeros 60VP/40BA usando DSC y DRS. A través de las medidas de DSC se observó una única transición vítrea para todos los entrecruzamientos. El análisis por DRS mostró como el incremento en entrecruzante produjo el típico efecto en la dinámica del proceso alpha, pero sin embargo, el proceso beta, que tenía las características típicas de una relajación JG, perdió de forma inesperada su carácter intermolecular para el mayor contenido en entrecruzante. El proceso gamma no se vio afectado. La segunda familia de materiales poliméricos estudiada fue una serie de poliuretanos segmentados (PUPH) modificados con diferentes cantidades de grafito expandido (EG), utilizado como relleno conductivo (desde 0 a 50% en peso). El análisis de los resultados obtenidos mediante Microscopía Electrónica de Barrido (SEM), Difracción de Rayos X y FTIR demostró la homogénea dispersión del relleno de EG en la matriz de PUPH. La técnica DRS se usó para estudiar las propiedades dieléctricas de los materiales compuestos PUPH/EG. La permitividad dieléctrica de los materiales mostró una transición de percolación desde aislante a conductor al incrementarse el contenido en EG (rango de 20-30% en peso). La adición de grafito expandido a la matriz de PUPH causó un incremento significativo en la conductividad dieléctrica de diez órdenes de magnitud, lo que indica el comportamiento de percolación.
[CAT] El desenvolupament de nous materials polimèrics de major complexitat produeix un desafiament cada vegada major en l'àrea de les ciències bàsiques. La relació entre l'estructura i la dinàmica molecular resulta de gran importància per al desenrotllament de noves tecnologies basades en aquests materials polimèrics. Així, una major comprensió de com petits canvis en l'estructura química afecten a les propietats dels materials, resulta essencial per al progrés científic i tecnològic. Un anàlisis en profunditat de la mobilitat molecular permet establir les relacions estructura-propietats. Partint d'aquesta base, el principal objectiu del present treball és l'estudi de la mobilitat molecular de dues famílies diferents de materials polimèrics. Per a això, les tècniques experimentals utilitzades van ser principalment la Calorimetria Diferencial de Rastreig (DSC) i l'Espectroscòpia de Relaxació Dielèctrica (DRS). La primera família de polímers caracteritzada va ser una sèrie de copolímers entrecreuats químicament compostos pels monòmers Vinilpirrolidona (VP) i Acrilat de Butilo (BA) . En primer lloc, es va estudiar la influència de la proporció molar de monòmer (XVP/YBA) en les propietats del copolímer. A través d'una anàlisi per Espectroscòpia d'Infraroig per Transformada de Fourier (FTIR), es va verificar l'existència d'interaccions dipol-dipol entre els grups amida. Mitjançant l'anàlisi per DSC, DRS i Anàlisi Dinamomecánico (DMA), es va evidenciar la influència d'aquestes interaccions en diferents paràmetres relacionats amb la mobilitat molecular. En segon lloc, es va analitzar l'efecte de la densitat d'entrecreuament en la dinàmica molecular dels copolímers 60VP/40BA mitjançant DSC i DRS. A través de les mesures de DSC es va observar una única transició vítria per a tots els continguts d'agent entrecreuant . L'anàlisi per DRS va mostrar com l'increment en agent entrecreuant va produir l'efecte esperat en la dinàmica del procés alfa. En canvi, el procés beta, que tenia les característiques típiques d'una relaxació JG, va perdre de forma inesperada el seu caràcter intermolecular per al major contingut en agent entrecreuant. El procés més ràpid gamma no es va veure afectat. La segona família de materials polimèrics estudiada va ser una sèrie de poliuretans segmentats (PUPH) modificats amb diferents quantitats de grafit expandit (EG) , utilitzat com a farcit conductiu (des de 0 a 50% en pes). L'anàlisi dels resultats obtinguts per mitjà de Microscòpia Electrònica de Rastreig (SEM), Difracció de Rajos X i FTIR va mostrar la dispersió homogènia del EG en la matriu de PUPH. La tècnica DRS es va utilitzar per a estudiar les propietats dielèctriques dels materials compostos PUPH/EG. La permitivitat dielèctrica dels materials va mostrar una transició de percolació des d'aïllant a conductor amb l'increment de contingut en EG (20-30% en pes). L'addició d'EG a la matriu de PUPH va causar un increment significatiu en la conductivitat dielèctrica, de deu ordes de magnitud.
Redondo Foj, MB. (2015). A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59457
TESIS
Fourmond, Erwann. "Contribution au photovoltaïque de première génération : du matériau silicium aux couches diélectriques." Habilitation à diriger des recherches, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00660319.
Full textRonza, Andrea. "Contributions to the risk assessment of major accidents in port areas." Doctoral thesis, Universitat Politècnica de Catalunya, 2007. http://hdl.handle.net/10803/37919.
Full textThis thesis is structured as a series of papers, all but one already published in international journals, preceded by a series of introductive sections. 1. Introduction. Port areas are described as related to risk assessment, handling of hazardous materials, accidents, relevant regulations and international conventions, and security. 2. Bibliographic survey. References are collected above all on port-HazMat topics, i.e. oil spills and risk assessment of port accidents, touching various risk assessment techniques. 3. Objectives, methodology and main results. This chapter defines the objectives of the research, i.e. to analyse port systems from the point of view of risk assessment of HazMat handling and to design proper risk assessment tools. Moreover, it lists the methodology followed and the major results obtained for each of the papers included in the thesis. 4. Conclusions. Papers Paper 1 – A Survey of Accidents in Ports (Loss Prevention Bulletin, 183, pp. 23-28, 2005). A historical analysis of 1,000+ port accidents was carried out allowing for various aspects (type and cause of accidents, consequences on people, etc.). The relative importance of diverse types of accidents was studied. Paper 2 – Predicting the Frequency of Accidents in Port Areas by Developing Event Trees from Historical Analysis (Journal of Loss Prevention in the Process Industries, 16, pp. 551–560, 2003). Historical analysis of a sample of port accidents similar to that of Paper 1 was used to identify accident sequences, i.e. general port accident scenario event trees. The frequency of some typical port accidents was then determined, showing that the event trees proposed can be used in QRA. Paper 3 – Using Transportation Accident Databases to Investigate Ignition and Explosion Probabilities of Flammable Spills (Journal of Hazardous Materials, 146(3), pp. 106–123, 2007). Literature analysis of ignition and explosion probability data is performed. The results of a scrutiny of some tens of thousands of records obtained from two vast spill databases are reported. Equations are proposed to predict the ignition and explosion probability as a function of the amount and the substance spilled. Paper 4 – A Quantitative Risk Analysis Approach to Port Hydrocarbon Logistics (J. Haz. Mat., 12 (1), pp. 10-24). A method is presented to perform QRA on hydrocarbon terminals. The approach accounts for minor and massive spills due to loading arm failures and hull ruptures. A shortcut approach for frequency calculation is proposed. An example application is given, based on a pilot study conducted in the Port of Barcelona. Paper 5 – Consequences of Major Accidents: Assessing the Number of Injured People (J. Haz. Mat., 133(1-3), pp. 46-52). QRA usually requires the estimation of the number of fatalities of accidents. The number of people injured, although important, is seldom evaluated, since this entails significant effort. A set of accident records were used to define a relationship between the number of people killed and the number of people injured. Principal component and clustering analyses were applied, thus obtaining expressions estimating the probable number of injured people as a function of the number of fatalities. Paper 6 – Economic Valuation of Damages Originated by Major Accidents in Port Areas (J. Loss Prev. Proc. Ind., in press). A procedure is presented to estimate the cost of damages suffered by people, equipment and the environment in consequence of port accidents. Economic compensation is proposed for damage to people, including fatal victims, injured victims and evacuees. Environmental harm is also considered, allowing for damage to the atmosphere, soil, water and fauna. Subsequently, estimates of the cost of the equipment and buildings affected are proposed. Finally, an assessment of the loss of profits due to activity breakdown and indirect costs is analysed.
Wen, Zhongmeng. "Contribution à l'étude des contraintes résiduelles sur le comportement mécanique des composites stratifiés ±θ." Thesis, Troyes, 2015. http://www.theses.fr/2015TROY0019/document.
Full textThis thesis work consists of two main parts: Deter-mination of residual stresses in composites laminates ±θ, introduced by the thermal cycle during the manufacturing process of laminates and Study of their influences on the mechanical behavior of these laminates. Limited by the current theory, the exper-imental determination of residual stresses in the laminates ±θ was very difficult. In this work, the incremental hole drilling method was performed for the residual stresses relaxation and then the gener-ated strains around the hole were measured with strain gages. The new approach proposed in this thesis allows associating the strains around the hole and the residual stresses in the laminates ±θ. The calibration coefficients were determined by the numerical simulation. With this approach, we found a linear relationship between the residual stresses and the fiber orientation angle θ for the composite laminates [02/θ2]s. By adapting a thermoelastic ma-terial model, the results obtained by our new ap-proach were modelized by the numerical study. Then we studied the influence of laminate thickness, curing cycle and hydrothermal ageing on the distri-bution of residual stresses. With the help of acoustic emission technique, the influences of the residual stresses on the damage and the mechanical behavior of composite laminates were studied through tensile tests. Finally, the importance of the residual stresses on the transverse failure of composite laminates was demonstrated comparing with the theoretical results
Geslin, P. A. "Contribution à la modélisation champ de phase des dislocations." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-01009892.
Full textYehya, Alissar. "Contribution to the experimental and numerical characterization of phase-change materials : consideration of convection, supercooling, and soluble impurities." Thesis, Artois, 2015. http://www.theses.fr/2015ARTO0207/document.
Full textOver the past two decades, the economic context has changed significantly due to the rise in energy prices. The building sector has become the main consumer of energy. Thereby, reducing the latter is now an economic, societal and environmental necessity. Accordingly, this topic mobilizes many researches. Phase Change Materials (PCMs) represent an innovative solution, which could improve buildings' energy performance. They are primarily used for temperature regulation, and their high storage capacity can reduce energy consumption.Our study aims at characterizing, via a complementary approach of experimental and numerical simulation, the behavior of a PCM (n-Octadecane). For this, we have developed and implemented a numerical model that corroborates the experimental results, and hence improves the prediction of the PCM performance.In this work, our main concern is to highlight the common errors or simplifications taken in the traditional numerical model, which can result in an overall discrepancy compared to the actual behavior of PCMs. Those discrepancies lead to wrong estimation of the fusion times and amount of energy stored. The major improvement of our model is the consideration of the natural convection, the supercooling, and the use of real enthalpy curves of the considered PCM. The actual temperature-enthalpy relationship takes into account the presence of a fraction of soluble impurities in the material. The originality of this work is to handle these physical phenomena via a lattice Boltzmann method (known by the acronym LBM), which leans on double distribution functions and coupled with the enthalpy formulation. Such an approach overcomes the non-linearity in the governing equations of fluid flow and heat transfer. Its simplicity and local character allow adding complexity to the model. Thereby, one can cover up the phase change problems, including those, which may occur in heterogeneous matrices. This last point has been also covered in this thesis.Finally, it turned out that the approach implemented here for phase change problems supports both, our experimental results and those available in the literature
Löbermann, Florian Wolfgang [Verfasser], and Dirk [Akademischer Betreuer] Trauner. "Contributions to the chemistry of polyhydroxylated aromatic compounds : methodology, natural products and materials science / Florian Wolfgang Löbermann. Betreuer: Dirk Trauner." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1051258987/34.
Full textSicsic, Paul. "Modeling and simulation of the nucleation and propagation of damage in quasi-brittle materials: Contribution of the variational approach." Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/docs/00/90/33/60/PDF/13_these_sicsic.pdf.
Full textThis thesis explores the use of damage models to predict the onset and propagation of cracks in a coherent manner. The results are based on the definition of a bulk energy density and a stability principle. Firstly, we study the nucleation of cracks in a notched domain. The limit loading can be decomposed as the product of three stress intensity factors: a scale effect, a geometry induced factor, function of the angle of the notch, and one due to the damage model. The cracks that appear have a characteristic profile whose width is of the order of the internal length. When the latter is small in front of the dimensions of the structure, by separating scales, and using a local minimum principle, we prove that the length of these damage bands follow Griffith's law. This fundamental results extends those based on global minimization but with a sounder physical base. A thorough investigation of the thermal shock problem leads to a better understanding of the nucleation of cracks. Especially the global property of crack periodicity is exhibited. These results are based on the variational approach and the properties would probably be lost for models developed in an other framework. Finally, numerical results based on an alternate minimization algorithm are established. The nucleation phase is controlled by the critical stress whereas the propagation is governed by the toughness. Size effects in two and three dimensions are captured. These numerical simulations are then confronted to experimental results
Ovalle, Carlos. "CONTRIBUTION A L'ETUDE DE LA RUPTURE DES GRAINS DANS LES MATERIAUX GRANULAIRES." Phd thesis, Ecole centrale de nantes - ECN, 2013. http://tel.archives-ouvertes.fr/tel-00979827.
Full textKoutsawa-Tchalla, Adjovi Abueno Kanika C.-M. "Contribution à la modélisation multi-échelle des matériaux composites." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0119.
Full textWe propose in this thesis several approaches for improving the multiscale modeling and simulation of composites’ behavior. Accurate and reliable modeling of the mechanical response of composite materials remains a major challenge. The objective of this work is to develop simplified methodologies based on existing homogenization techniques (numerical and analytical) for efficient prediction of nonlinear behavior of these materials. First choice has been focused on the Mean-field homogenization methods to study the elasto-plastic behavior and ductile damage phenomena in composites. Although restrictive, these techniques remain the best in terms of computational cost and efficiency. Two methods were investigated for this purpose: the Incremental Scheme Micromechanics (IMS) in One-site modeling and the Mori-Tanaka model in multi-site modeling (MTMS). In the framework of elastoplasticity, we have shown and validated by finite element method that the IMS homogenization results are more accurate, when dealing with high volume fraction composites, than the Mori-Tanaka model, frequently used in the literature. Furthermore, we have extended the Mori-Tanaka's model (MT) generally formulated in One-site to the multi-site formulation for the study of elasto-plastic behavior of composites with ordered microstructure. This approach shows that the multi-site formulation produces consistent results with respect to finite element and experimental solutions. In the continuation of our research, the Lemaître-Chaboche ductile damage model has been included to the study of elasto-plastic behavior in composite through the IMS homogenization. This latest investigation demonstrates the capability of the IMS model to capture damage effects in the material. However, the issue on the loss of ellipticity was not addressed. Finally we develop a numerical homogenization tool based on computational homogenization. This novel numerical tool works with 2D and 3D structure and is fully integrated in the conventional finite element code ABAQUS through its subroutine UMAT. The (FE2) method offers the advantage of being extremely accurate and allows the handling of more complex physics and geometrical nonlinearities. Linear and non-linear cases were studied. In addition, its combination with ABAQUS allows the use of major resources provided by this software (a panel of toolbox for various mechanical, thermomechanical and electrical analysis) for the study of multi-physics problems. This work was validated in the linear case on a two-scale analysis in bending and compared to the multi-scale method ANM (Nezamabadi et al. (2009)). Extensive work will be needed later with applications on non-linear problems to highlight the value of the developed tool
Rochdi, El Houssain. "CONTRIBUTION A L'ANALYSE DU COMPORTEMENT MECANIQUE DE DALLES EN BETON ARME RENFORCEES PAR MATERIAUX COMPOSITES." Phd thesis, Université Claude Bernard - Lyon I, 2004. http://tel.archives-ouvertes.fr/tel-00138446.
Full textDans ce contexte, un protocole expérimental a été mis au point afin d'évaluer les performances des diverses théories développées pour prédire la rupture des composites. Cette étude a démontré l'efficacité du critère de Tsai-Wu à prédire la résistance du composite stratifié carbone/époxy étudié.
Dans un second temps, nous avons élaboré une procédure théorico-expérimentale portant sur l'évaluation du gain en résistance des dalles renforcées par matériaux composites ainsi que les paramètres influençant le comportement en rigidité. L'ensemble des résultats a mis clairement en évidence l'influence du composite en particulier sur la capacité portante de la dalle qui peut être augmentée jusqu'à cinq fois.
L'analyse des modes de rupture obtenus expérimentalement confirme que la ruine de la structure se produit essentiellement par poinçonnement. En conséquence, notre travail s'est orienté vers l'analyse du comportement des dalles renforcées vis-à-vis du poinçonnement. Parmi les différents modèles proposés pour prédire la résistance au poinçonnement des dalles BA, les prédictions du modèle de Menètrey approchent le mieux les valeurs expérimentales. La dernière partie de l'actuel travail concerne la modification du modèle de Menétrey afin de considérer l'effet du composite sur la résistance des dalles renforcées au poinçonnement.
Leca, Adrienne. "Contribution à l'étude de la santé-matière de préformes carbone." Thesis, Le Havre, 2015. http://www.theses.fr/2015LEHA0016/document.
Full textThis aim of this work is to characterize the damage suffered by a carbon tow in textile processing methods, and more particularly during preforms weaving for composites materials. A mechanical characterization protocol on dry tow tensile test and a non-destructive method of image analysis, have been developed to quantify this damage
Aldroe, Hassan. "Contribution au développement des techniques de marker-bands en fatigue." Thesis, Tours, 2012. http://www.theses.fr/2012TOUR4026/document.
Full textThe fracture surfaces of fatigue can represent complex aspects according to:type of material, provided mechanism of mechanical stresses, ambient environment, etc.Under complex loadings or variable ones, fracture surfaces are more difficult to analyze because such changes can cause change in mechanisms in certain materials.Under variable amplitudes, one of the important issues is the knowledge of the crack growth rate.Current techniques involve optical measurements or indirect ones that measures the kinetics of crack growth.An elegant method is to generate marker bands that can leave a mark on the fracture surface which is then identified by scanning electron microscope analysis.For this purpose one can use: - small overload, under load, cycles below the threshold, a change of temperature, etc.The aim of this thesis is to develop the technique of marker bands on three materials:an aluminum alloy, steel and synthetic rubber.The idea is to develop this technique without changing the propagation kinetics.The experiments will be conducted by fatigue cracking with or without marking marker bands to test this hypothesis.The experimental work has been carried out in LMR laboratory
Bouguerra, Kheireddine. "Contribution à l'étude du comportement de dalles de ponts en béton armé de barres en PRF soumises à des charges concentrées simulant les charges de roues." [S.l. : s.n.], 2008.
Find full textCaborgan, Rodica. "Contribution à l'analyse expérimentale du comportement thermomécanique du caoutchouc naturel." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2011. http://tel.archives-ouvertes.fr/tel-00677252.
Full textChareyron, Baptiste. "Contribution à la modélisation de paliers magnétiques actifs auto-détecteurs." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLN007.
Full textActive magnetic bearings with a self-sensing approach are electromechanical transducers. They realize two different functions at the same time: power function for moving the rotor, and sensor function for estimating the size of the air gap and the position of rotor. In this thesis, we developed an electromagnetic model for conception and optimization of these active magnetic bearing. In order to achieve this goal, different models were developed during this thesis:- A high frequency model of a laminated and polarized material builds with a reversible permeability measure and an homogenization model for high frequency;- A simulation model induced currents in a laminated rotor created by its own rotation. This one permits eddy current losses determination and the impact of rotation on the position estimation;- Finally, a high frequency impedance model for a laminated, saturated and polarized magnetic circuit. This model computes in 3 steps: nonlinear magnetostatic calculation, integration of high frequency model and linear magnetodynamic calculation. These different approaches were validated experimentally with an Epstein frame and with two different magnetic bearings. All these models were then exploited in a tool for optimal conception of active magnetic bearings with a self-sensing approach. Finally, a bi-objective multivariable optimization was realized to design an optimal active magnetic bearing to both estimate position and create force
Thomas, L. V. "Contribution à l'étude de nanostructures magnétiques : du matériau nanocristallisé à l'agrégat." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10232.
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