Dissertations / Theses on the topic 'Propriétés à température finie'
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Sinito, Chiara. "Propriétés magnéto-optiques de nanocristaux de CdSe individuels à basse température." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0282/document.
Full textThe development of emerging applications of CdSe nanocrystals requires a detailed understanding of the band-edge exciton fine structure and relaxation pathways. This thesis is focused on cryogenic spectroscopy of single nanocrystal with a remarkable photostability. Photoluminescence spectra as a function of temperature and under external magnetic fields provide a spectral fingerprint of the low energy sub-levels, revealing the morphology and the crystal structure of individual nanocrystals. In order to probe the entire band-edge exciton fine structure, a high resolution luminescence excitation technique has been developed. Zeeman and anisotropy-induced splittings are used to reveal the entire 8-state band-edge fine structure, enabling complete comparison with band-edge exciton models. State selective excitation allows the preparation of single quantum states. It is also used to map the hole spin relaxation pathways between the fine structure sub-levels.Charged quantum dots provide an important platform for a range of emerging quantum technologies. Double shell CdSe nanocrystals are engineered to efficiently ionize at cryogenic temperatures, resulting in trion emission with a single sharp zero-phonon line and a near-unity quantum yield. Zeeman splitting of this line enables direct determination of electron and hole g-factors. Spin relaxation is observed in high fields, enabling identification of the trion charge. Importantly, we show that spin flips are completely inhibited for Zeeman splittings below the low-energy bound for confined acoustic phonons. This charac- teristic unique to colloidal quantum dots has potential applications in single spin coherent manipulation
Stern, Anthony. "Comportements métallurgique et mécanique des matériaux de gainage du combustible REP oxydes à haute température." Paris, ENMP, 2007. http://www.theses.fr/2007ENMP1506.
Full textZirconium alloys are used as cladding materials in PWR. As they are submitted to very extreme conditions, it is necessary to check their behaviour and especially to make sure they meet the safety criteria. They are therefore studied under typical in service-loadings but also under accidental loadings. In one of these accidental scenarios, the cladding temperature may increase above 800°C, in a steam environment, and decrease before a final quench of the cladding. During this temperature transient, the cladding is heavily oxidised, and the metallurgical changes leads to a decrease of the post quench mechanical properties. It is then necessary to correlate this drop in residual ductility to the metallurgical evolutions. This is the problem we want to address in this study. As oxygen goes massively into the metallic part - a zirconia layer grows at the same time – during the high temperature oxidation, the claddings tubes microstructure shows three different phases with various mechanical properties. In order to reproduce the behaviour of this multi-layered material, the first part of this study consisted in creating samples with different oxygen contents, similar to those observed in the different phases of the real cladding. The study was especially focused on the phase transformation upon cooling. A mechanism was proposed to describe this phase transformation. Then, these materials were mechanically tested at various temperatures and for various mean oxygen contents. It was thus possible to start some preliminary finite element calculations to describe the cladding behaviour under the standard technological ring compression test
Korchagina, Kseniia. "Etude par dynamique moléculaire des propriétés structurales, dynamiques et thermodynamiques d'agrégats moléculaires." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30227/document.
Full textWater clusters constitute an important class of chemical species due to their central role in many physico-chemical and biological processes, in particular, atmospheric processes. Their physical and chemical properties are particularly sensitive to size and finite-temperature effects, which makes them particularly difficult to characterize experimentally. This thesis focused on the theoretical investigation of the structural, dynamical and thermodynamical properties as well as on the reactivity of various water clusters with the aim to implement appropriate modeling tools to enable a more detailed description of these systems. To do so, we used the paralleltempering molecular dynamics approach that was coupled with calculations of energies and gradients carried out by the Self-Consistent-Charge Density-Functional based Tight-Binding (SCC-DFTB) method.Three main areas were addressed during the work. In the first part, a detailed analysis of the structure of water clusters (H2O)nSO24- and (H2O)nH2SO4 with n=1-20 is performed. This study highlights the influence of the nature of the sulfur impurity on the hydrogen bond network of these species.The second part of this thesis focuses on the study of the "solid-liquid" phase transition in various water clusters. In addition to the sulfur-containing water clusters mentioned above, we also investigated protonated water clusters containing from 19 to 23 water molecules. To better understand the phase transition mechanism, we considered various structural changes associated with the transition, such as the evolution of the distributions of intermolecular angles and the evolution of the number of molecular rings in the cluster. We also characterized the phase transition through dynamical indicators such as the crossover frequency of the excess proton. The last part of this thesis is devoted to the study of the influence of small water clusters (from 1 to 10 water molecules) on the recombination reaction between the H atom and the CO molecule. This reaction is the first step in the formation of simple oxygenated organic molecules in the interstellar medium. It is therefore of particular interest. Due to the analysis of collisional dynamics between H and CO and the calculation of effective reaction cross sections we showed that the presence of water molecules plays an important role in the HCO radical formation
Debord, Régis. "Développement d'une cellule haute pression haute température dans la presse Paris-Edimbourg pour la mesure de propriétés élastiques et de densité : application sur les oxydes de fer." Paris 6, 2004. http://www.theses.fr/2004PA066448.
Full textDebord, Régis. "Développement d'une cellule haute pression haute température dans la presse Paris-Edimbourg pour la mesure de propriétés élastiques et de densité : Application sur les oxydes de fer." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2001. http://tel.archives-ouvertes.fr/tel-00189118.
Full textMassaoudi, Mohammed. "Contribution à la modélisation du comportement mécanique des matériaux biphasés γ/γ'." Toulouse 3, 2002. http://www.theses.fr/2002TOU30205.
Full textLiu, Xiongjie. "Développement de la caractérisation du comportement local à haute température des alliages métalliques par micro indentation." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2326/document.
Full textOver the past two decades, the high-temperature indentation experiment has been developed gradually to meet increasingly high industrial demand. ln order to guarantee a good level of accuracy of the measurements, it is necessary to solve the problems associated with high temperature, such as the choice of the indenter material, the thermal stability of the system, heating design, etc. This thesis aims to develop the methodology of the high-temperature indentation experiment to characterize metallic materials. Particular attention has been given to the search for candidate materials for the tip and to the determination of the force and penetration ranges used for the correct operation of an indenter. The finite element analysis helps us to study the influence of defects such as the presence of a thin film and that of a misalignment between the indentation axis and the sample surface. To find a better indenter material, it is necessary to test the geometric and chemical stability of different candidate materials that can replace the diamond at elevated temperature. The collaboration with the Swiss company Anton Paar, which specializes in the manufacture of measuring machines for the mechanical characterization of a wide variety of materials, enables the development of new high-temperature micro- and nano-indentation equipment. By using the new device, we were able to carry out the indentation tests to characterize the mechanical properties of different materials and to check the thermal stability of this new instrument
Paulin, Sébastien. "Approximations simples d'intégrales de chemins à température finie." Lyon, École normale supérieure (sciences), 2007. http://www.theses.fr/2007ENSL0445.
Full textLiu, Lihui. "Cosmologie quantique à température finie en théorie des supercordes." Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00733052.
Full textZhong, Anruo. "Machine learning and adaptive sampling to predict finite-temperature properties in metallic materials at the atomic scale." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP107.
Full textThe properties and behaviors of materials under extreme conditions are essential for energy systems such as fission and fusion reactors. However, accurately predicting the properties of materials at high temperatures remains challenging. Direct measurements of these properties are constrained by experimental instrument limitations, and atomic-scale simulations based on empirical force fields are often unreliable due to a lack of accuracy. This problem can be addressed using machine learning techniques, which have recently become widely used in materials research. Machine learning force fields achieve the accuracy of ab initio calculations; however, their implementation in sampling methods is limited by high computational costs, typically several orders of magnitude greater than those of traditional force fields. To overcome this limitation, this thesis has two objectives: (i) developing machine learning force fields with a better accuracy-efficiency trade-off, and (ii) creating accelerated sampling methods to facilitate the use of computationally expensive machine learning force fields and accurately estimate free energy. For the first objective, we enhance the construction of machine learning force fields by focusing on three key factors: the database, the descriptor of local atomic environments, and the regression model. Within the framework of Gaussian process regression, we propose and optimize descriptors based on Fourier-sampled kernels and novel sparse points selection methods for kernel regression. For the second objective, we develop a fast and robust Bayesian sampling scheme for estimating the fully anharmonic free energy, which is crucial for understanding temperature effects in crystalline solids, utilizing an improved adaptive biasing force method. This method performs a thermodynamic integration from a harmonic reference system, where numerical instabilities associated with zero frequencies are screened off. The proposed sampling method significantly improves convergence speed and overall accuracy. We demonstrate the efficiency of the improved method by calculating the second-order derivatives of the free energy, such as the elastic constants, which are computed several hundred times faster than with standard methods. This approach enables the prediction of the thermodynamic properties of tungsten and Ta-Ti-V-W high-entropy alloys at temperatures that cannot be investigated experimentally, up to their melting point, with ab initio accuracy by employing accurate machine learning force fields. An extension of this method allows for the sampling of a specified metastable state without transitions between different energy basins, thereby providing the formation and binding free energies of defective configurations. This development helps to explain the mechanism behind the observation of voids in tungsten, which cannot be explained by existing ab initio calculations. The free energy profile of vacancies in the Ta-Ti-V-W system is also computed for the first time. Finally, we validate the application of this free energy sampling method to liquids. The accuracy and numerical efficiency of the proposed computational framework, which combines machine learning force fields and enhanced sampling methods, opens up numerous possibilities for the reliable prediction of finite-temperature material properties
Wollbrett-Blitz, Judith. "Comportement mécanique longitudinal et transverse, micro-mécanismes de déformation et effet de la température sur la fibre Kevlar® 29." Thesis, Paris, ENMP, 2014. http://www.theses.fr/2014ENMP0062/document.
Full textDesigning safer and lighter vehicles is a major challenge for manufacturers. Nowadays, a vehicle needs to be eco-friendly and conciliate efficiency and energy-saving. Considering these requirements, tire materials are subject to change: high performance polymers are a good replacement, in terms of weight and dissipation, for traditional reinforcements such as drawn steel. For instance, aramid strands (1000 fibres) are used because the single fibre exhibits good mechanical properties such as its high modulus (85 GPa) conferred by its anisotropy or its high temperature resistance. The mechanical performance of a Kevlar® fibre is due to its different scale organisation : the primary (molecular chains held by covalent bonds), the secondary (pleated sheets held by interactions) and the tertiary structure (sheets stacked together). Because of the cooling thermodynamics during the fabrication process, the 15 microns diameter fibre seems to have a skin/core structure with punctual more or less critical defects. To go further in the understanding of the complex structure, the contribution of the skin/core structure in the mechanical performance in the longitudinal and the transverse directions is investigated through a multi-disciplinary approach made of a numerical and an experimental study. During its use, an aramid single fibre undergoes cyclic multiaxial loading and harmful thermal treatments, at the origin of structural and mechanical properties modifications but also dissipative behaviour evolution, still misunderstood. To deal with these change in depth, an experimental and numerical multi-scale characterisation is used. Mechanical and thermal treatments are realised and their impact on the microstructure, on the deformation micromechanisms and on the mechanical properties including the dissipative behaviour are investigated. Limiting use values in terms of temperature, longitudinal and transverse stresses are highlighted in this work in order to understand modifications enhanced by the fibre life cycle
Plouffe, Dany. "Méthodes d'amas quantiques à température finie appliquées au modèle de Hubbard." Thèse, Université de Sherbrooke, 2011. http://savoirs.usherbrooke.ca/handle/11143/5152.
Full textGagnon, Anne-Marie. "Une méthode alternative pour obtenir le pouvoir thermoélectrique à température finie." Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/8847.
Full textEl, Hamidi Mohamed. "Propriétés stochastiques d'un système non-linéaire en dimension finie." Pau, 1989. http://www.theses.fr/1989PAUU3014.
Full textJullien, Jean-Baptiste. "Etude de fiabilité et définition de modèles théoriques de vieillissement en très haute température pour des systèmes électronique et microélectronique." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14604/document.
Full textThis work is performed in analysis and prediction areas of Multi-Chip Module package reliability. It presents a reliability study on wire bonding in high temperature environment from aging tests and experimental analyzes. Results permit to identify degradation mechanisms and evaluate temperature limits of these interconnections. It develops a study of the thermomechanical behavior of adhesive joints from mechanical characterization tests, accelerated aging tests and finite element simulations. These methods are used to assess the criticality of packages from the design phase
Donazzon, Benoit. "Céramiques apatitiques basse température : élaboration -propriétés." Toulouse, INPT, 1998. http://www.theses.fr/1998INPT009C.
Full textReinosa, Urko. "Renormalisation d'un schéma d'approximation auto-cohérent en théorie des champs à température finie." Palaiseau, Ecole polytechnique, 2004. http://www.theses.fr/2004EPXX0060.
Full textPrin, Elise. "Propriétés optiques fondamentales de nanocristaux de semi-conducteurs individuels aux températures cryogéniques." Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0182.
Full textSemiconductor nanocrystals exhibit outstanding optical and electronic properties due to the quantum confinement of their charge carriers, making them valuable for various applications in optoelectronics, light-emitting devices, and spin-based technologies. Understanding the physics of the band-edge exciton, whose recombination is at the origin of their photoluminescence, is crucial for developing these applications. This thesis focuses on the experimental study of the optical properties of indium phosphide and lead halide perovskites nanocrystals. Using magneto-photoluminescence spectroscopy onsingle nanocrystals at low temperatures, we reveal spectral fingerprints highly sensitive to nanocrystal morphologies and elucidate the entire band-edge exciton fine structure and charge-complex binding energies. In InP/ZnS/ZnSe nanocrystals, the evolution of photoluminescence spectra and decays under magnetic fields show evidence for a ground dark exciton level lying less than a millielectronvolt below the bright exciton triplet, findings supported by a model accounting for the shape anisotropy of the InPcore. In lead halide perovskites, we demonstrate that the ground exciton state is dark and lies several millielectronvolts below the lowest bright exciton sublevels, settling the debate on the bright-dark exciton level ordering in these materials. Combining our results with spectroscopic measurements on various perovskite nanocrystal compounds, we establish universal scaling laws relating exciton fine structure splitting, trion and biexciton binding energies to the band-edge exciton energy in lead-halide perovskitenanostructures, regardless of their chemical composition. Lastly, preliminary spectroscopy analyses on perovskite nanorods with a high aspect ratio suggest their potential as candidates for quantum light emitters due to their characteristic single emission line
Ali, Bassem. "Modèle numérique pour comportement mécanique des chaussées : application à l'analyse de l'orniérage." Lille 1, 2006. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2006/50376-2006-Ali.pdf.
Full textPlouffe, Dany. "Étude du modèle de Hubbard à température finie par la théorie des perturbations interamas." Mémoire, Université de Sherbrooke, 2004. http://savoirs.usherbrooke.ca/handle/11143/4626.
Full textZhang, Ludi. "Etude de fiabilité des modules d'électronique de puissance à base de composant SiC pour applications hautes températures." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2012. http://tel.archives-ouvertes.fr/tel-00988235.
Full textAdes, Claude. "Propriétés optiques des verres silicatés à haute température." Toulouse 3, 1989. http://www.theses.fr/1989TOU30164.
Full textLow, Zi Kang. "Matériaux cellulaires isolants haute température : Relation microstructure-propriétés." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI122.
Full textThis CIFRE doctoral study, performed in collaboration with Saint-Gobain Research Provence, aims to model the thermal properties of NorFoam XPure®, an alumina foam designed for high temperature thermal insulation (1200°C–1700°C). The goal is to develop and validate multiscale numerical models to compute the conductive and radiative heat transfer through the foam from 3D tomography-reconstructed microstructures and the intrinsic properties of each constituent phase. Specific attention is given to the complex porosity in the studied foam: in addition to the open-cell network, smaller pores are also found within the foam skeleton. Novel approaches are proposed in the present work to take into account the influence of this dual-scale porosity. Firstly, effective heat conduction through the foam is modeled with finite element homogenization techniques. It is demonstrated that the commonly used periodic boundary conditions are unsuitable for tomography-reconstructed foams, and that a set of mixed boundary conditions gives more accurate and precise results for such foams. As radiative transfer through the porous foam skeleton is characterized by high volume scattering and significant wave effects, a novel physical optics approach based on the discrete dipole approximation is next developed to model the influence of these phenomena. The radiative properties of the foam are then determined through a ray tracing method that takes into account the complex radiative behavior of the porous foam skeleton. The influence of non-specular reflection and refraction at the interfaces between the foam cells and skeleton is studied. Finally, the homogenized properties are applied to simulate the coupled conductive and radiative heat transfer through the foam. The model predictions are systematically compared to thermal and spectroscopic measurements performed on samples of the foam and the foam skeleton material. The good agreement between numerical and experimental results confirms the predictive capabilities of the models developed in this study
Poizat, Didier. "Singularités infrarouges et singularités de masse dans les théories quantiques des champs relativistes à température finie." Nice, 1990. http://www.theses.fr/1990NICE4419.
Full textMey, Sébastien. "Absorbeur solaire volumique haute température à propriétés optiques contrôlées." Thesis, Perpignan, 2016. http://www.theses.fr/2016PERP0014/document.
Full textSolar-to-electricity power plants appear to be the most promises way for large electricity production in the future, in terms of costs as well as environmental impacts. Thus, reaching the required technology level still requires research and innovations in order to implement such power plants at large scale.In this context, volumetric solar receivers/absorbers could allow us to reach higher temperatures in comparison to surface receivers (actual concentrating solar power technology used in solar towers), leading to high efficiency thermodynamical cycles such as Brayton cycles. With the ANR-OPTISOL project, this thesis tends to give new answers on volumetric solar absorbers using ceramic foams:- Experimental studies of open pores ceramic foams used as high temperature volumetric solar absorber have been conducted at CNRS-PROMES laboratory (UPR 8521), with designed of a dedicated experiment for 5cm diameter samples operating under quasi-1D conditions submitted to concentrated solar power at the focal point of a vertical axis solar furnace;- A numerical code has been developed in order to solve coupled heat transfers in porous medium using the “equivalent homogeneous medium” hypothesis, then validated on the experimental campaigns;- Finally, an optimization algorithm has been used (“particle swarm optimization”) aiming the identification of the optimal geometrical characteristics maximizing the solar-to-thermal efficiency of ceramic foams
Zavala, Quiñones Israël. "Prédiction des distorsions dans le cas du soudage TIG de l'acier 17-4 PH : élaboration d'un modèle avec prise en compte des phénomènes de durcissement par précipitation." Lorient, 2006. http://www.theses.fr/2006LORIS059.
Full textThe aim of this thesis is the prediction of distortions in welded assemblies. Therefore, a thermo-mechanical and metallurgical model, describing the effects of welding for the 17-4PH steel (X5CrNiCu17-4 martensitic precipitation hardening stainless steel) at the T1 condition has been developed. This model takes into account the following metallurgical transformations: the precipitation hardening/coalescence phenomena, the austenitic transformation during heating and the martensitic transformation during cooling. A set of short isothermals experiences at different temperature, were made on T1 condition samples to linking up the hardness to the precipitation state. The experiences allowed, by an additive approach, to taken it into account the precipitation/coalescence phenomena, using an equivalence times-temperature parameter, set it in a Johnson-Mehl-Avrami form. The mechanical behaviour of all different phases is described by two models, elasto-plastic and Elasto-Visco-Plastic. Besides, a refined exploitation of dilatometric essays allowed the determination of different expansion coefficients for each phases. In addition, the transformation induced plasticity during phase transformation was measured by dilatometric constrained essays. The models are implemented in the fined elements code Sysweld, which allows a 3D numerical simulation, and the results confronted to the experimental from an instrumented welding test. We were able to verify that in the case of the steel 17-4PH a refined metallurgical model that takes in to account precipitation phenomena needs to be used, to get a pertinent distortion prediction during welding
Mauchin, Agnès. "Comportement mécanique à haute température de composites carbone/carbone." Bordeaux 1, 1997. http://www.theses.fr/1997BOR10676.
Full textSans, Morgan. "Caractérisation des propriétés thermophysiques de mousses céramiques à haute température." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0192.
Full textSince the end of the twentieth century, research and development has increasingly focused on the use of solid ceramic foams for a myriad of high-temperature applications because of their advantageous thermal, mechanical, chemical or optical properties. In a global energy context that is tending to reduce the consumption of fossil fuels and greenhouse gas emissions, they appear to be a promising solution due to their ability to absorb, recover and convert a large radiative flux. In particular, they are the subject of growing interest in the field of solar thermal energy, while LEMTA is interested in these materials as a recover of fatal heat present in high-temperature industrial processes (glassware, cement, metallurgy, etc.). However, some studies have shown that improving current and future systems requires a better understanding of the relationship between the structural/thermal/optical properties associated with these heterogeneous media (geometry, porosity, pore diameter, conductivity, emissivity, etc.) and heat transfers. The objectives of this work are to provide relevant modelling and characterization tools that allow the description of conductive, convective (forced) and radiative heat transfers. Three characterization methods are studied and detailed in this manuscript. 1. In the case of conductive and radiative transfer, the main difficulty lies in the ability to separate the contribution of each heat transfer mode. In order to exceed these limits, a transitional method based on the principle of the flash method was used. The ceramic foam, placed between two ceramic soleplates and in the centre of a tubular furnace, is thermally excited while the thermal elevation is measured on the side opposite the latter. In parallel, a direct model resolving the Energy Balance Equation by the Finite Volume Method while the Radiative Transfer Equation by an optimized reciprocal Monte Carlo method was implemented. The latter method allows, while maintaining reasonable calculation time, to solve radiation transfers more generally than the method usually used. A simultaneous identification of equivalent phononic conductivity and optical thickness was performed on a wide variety of structured and stochastic foams composed of SiC or SiSiC up to 800 °C. Compared to simplified models such as Rosseland's, this study provides a better understanding of the validity of the diffusion approximation and guides the choice of modeling and parameters to be used. 2. Another difficulty lies in the ability to numerically solve a coupled problem directly on the 3D heterogeneous geometry of the porous medium. A Monte Carlo method allowing the resolution of both transfer modes in a single algorithm has been employed. The flash method was performed thanks to the latter in a entirely numerical manner. It allows the solution to be obtained quickly with the increase in radiation transfer. The proposed procedure allowed the identification of the equivalent properties of structured foams (Kelvin's cells). 3. A method for characterizing axial and radial thermal dispersion coefficients has been implemented. the experimental bench is composed of 5 sections of 20 cm SiC foams separated by flanges for temperature measurement. A hot air flow is applied to the porous medium at equilibrium with the ambient temperature. In parallel, a one-temperature model allows a 2D axisymmetric and multilayer resolution of the thermal problem. The application of an inversion algorithm allows the estimation of the two coefficients for different flow rates
Pocheron, Mickaël. "Life-time prediction of solder joints used in surface mount assemblies during thermo-mechanical and isothermal aging." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0245.
Full textBecause of ROHS or WEEE directives, in a close future, lead materials will be banned from electronicindustry. Unfortunately, Schlumberger is using high-lead content solders for surface mount devices forhigh temperature applications. Considering this issue, Schlumberger puts in place high amount of investments to replace these solders by lead-free solders. The topic of the work is to study lead free candidates destined to support Schlumberger high temperature mission profiles. The device under test chosen for this project is a surface mount device composed of a passive component connected to a ceramic substrate by solder joints. The predictive study of reliability of these new assemblies for high temperature applications needs two complementary analyses. The first study is to characterize, experimentally, the life time of surface mount assemblies using these new lead free solders submitted to accelerated thermomechanical and isothermal aging tests. Hence, the first benefits for Schlumberger are knowledge on thecompatibility of these new alloys with their current finishes with the microstructure and intermetallic compounds evolution. More over, the main effects due to aging are investigated like failure sites and mechanisms. The second goal of the project is to perform thermo-mechanical simulations of surface mount assembly under thermal cycling. Simulations help to understand local phenomena and estimatefatigue parameters under other thermal conditions. Then, a correlation between experimental results about failure and calculated fatigue leads to an estimation of the life time of the assemblies. Thus, simulations have the advantage to reduce the number of time-consuming and expensive thermo-mechanical agingtests. To perform a simulation, the physical parameters of each solder material are needed like elastic,plastic and creep data. Additional benefits for Schlumberger involve mechanical properties which are, at the moment, unknown for these new high temperature lead free materials
QiAO, Jianghao. "Modélisation des propriétés thermomécaniques effectives de dépôts élaborés par projection thermique." Thesis, Belfort-Montbéliard, 2012. http://www.theses.fr/2012BELF0186/document.
Full textIn the present study, the thermal conductivity and elastic modulus of thermal spray YPSZcoatings were predicted by 2D and 3D finite differences and finite elements numericalmodeling based on cross-sectional images.The influence of the image resolution, size and threshold on the predicted properties of thecoating was studied. Moreover, the effects of the numerical method and of the boundarycondition were investigated. In particular, the quantification of the Knudsen effect(rarefaction effect) on the heat transfer through a porous structure was realized by numericalmodeling in combination with image analysis. The predicted thermal conductivities obtainedby 3D modeling were found to be higher than those obtained by 2D modeling, and in betteragreement with the measured results. A 2D/3D correlation was sucessfully found for themodeling of thermal conductivity: this correlation allows predicting 3D computed valuesfrom 2D ones
Ren, Zheng. "Contribution au développement du transistor bipolaire à fort gain et d'un interrupteur bidirectionnel à quatre quadrants." Thesis, Tours, 2018. http://www.theses.fr/2018TOUR4031/document.
Full textIn order to meet the requirement of more efficient electrical energy management for intelligent buildings, a new 600V bidirectional switch, named as TBBS, has been proposed by the GREMAN laboratory. Previous studies have validated the current and voltage bidirectionality of this newly proposed topology. The research work carried out in this thesis deals with a deeper and more comprehensive study of this bidirectional switch and its elementary component - the High-gain bipolar juncion transistor. The first chapter introduces the operation of the TBBS and its physical modeling in a finite element simulation environment. The second chapter presentes the research work related to the experimental caracterisation of the TBBS and the High-gain bipolar junction transistor. At last the third chapter deals with the electrical modeling of these two bipolar components
Biadala, Louis. "Propriétés optiques de nanocristaux de CdSe/ZnS individuels à basse température." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00654493.
Full textBlanchart, Philippe. "Thermistances BaTi03 à coefficient de température positif microstructure et propriétés électriques." Limoges, 1990. http://www.theses.fr/1990LIMO0083.
Full textWeck, Gunnar. "Etude des propriétés de l'oxygène sous haute pression et haute température." Paris 6, 2001. http://www.theses.fr/2001PA066251.
Full textChen, Anne-Sophie. "Propriétés magnétiques nucléaires de l'3He superfluide à ultra-basse température." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10095.
Full textNeuville, Daniel R. "Propriétés thermodynamiques et rhéologiques des silicates fondus." Paris 7, 1992. http://www.theses.fr/1992PA077141.
Full textTchofo, Dinda Patrice. "Étude d'un réseau bidimensionnel à maille hexagonale à deux sites dans un substrat double-quadratique : diagramme de phase, structure et dynamique des parois, effets de taille finie." Dijon, 1991. http://www.theses.fr/1991DIJOS061.
Full textDevineau, Karine. "Déstabilisation haute température de poudres granitiques : évolution des propriétés minéralogiques et physiques." Vandoeuvre-les-Nancy, INPL, 2002. http://docnum.univ-lorraine.fr/public/INPL_T_2002_DEVINEAU_K.pdf.
Full textLarrouturou, Florent. "Amélioration des propriétés radiatives des récepteurs solaires surfaciques haute température par microstructuration." Thesis, Perpignan, 2015. http://www.theses.fr/2015PERP0030.
Full textConcentrated solar power (CSP) technology is an alternative for renewable thermal energy generation and a promising source of energy. Managing the optical properties of a cavity solar receiver to create spectral and directional selectivities is a solution to improve receiver and solar power plant efficiencies in order to reduce cost. The two main steps of the development are to quantify the potential gain that may result from theoretical selectivities and then the optimization of microstructuration to increase as possible the spectral selectivity. At first, a calculation code was built in order to quantify the influence of receiver on the global solar power plant efficiency. Then a parametric study which takes into account thegeometry, the material, the roughness and the microstructure of the receiver was conducted. At last, an optimization of microstructuration with uniperiodic and biperiodic structures was studied. As a conclusion the best structure is a biperiodic pyramidal relief which offers a huge gain of absorptivity
Audouard, Lisa. "Conception et caractérisation de matériaux ultra haute température à gradient de propriétés." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2023. http://www.theses.fr/2023UBFCA019.
Full textThe development of a new green ergol prototype for satellite repositioning engines requires more severe thermal and environmental conditions for combustion chamber materials than is currently the case. As a result, alternative materials known as functionally graded materials (FGM) have been developed for several years as part of an ONERA-CNES-ICB study. The aim of this thesis is to pursue the development of this type of ceramic/metal gradient material, in order to optimize its design and ensure that it can be used up to 2400 °C in the presence of water vapor. Firstly, different configurations of FGM developed by air plasma thermal spraying (APS) were tested under vacuum laser heat flux up to 2350 °C. By modelling the cracking of these materials when subjected to thermal shock, the link between the observed degradations and the FGM configurations was better established. In particular, it has been shown that increasing the thickness of the ceramic on the FGM surface is responsible for the appearance and propagation of deeper, deviated cracks.Secondly, the possibility to use such FGM under an oxidising atmosphere at ultra-high temperature was studied through two experimental set ups. The first one is a laser test bench which allowed to assure the resistance of the materials submitted to repeated thermal schocks up to 1800 °C in presence of water vapour. The tested materials presented an appropriate behaviour under the tested conditions. The degradation mechanisms related to FGM oxidation have been identified and compared from one FGM configuration to another and linked to the tested conditions. The second one permits to qualify the behaviour of FGM in the H2/O2 flame of a combustion chamber. Thus, the tested conditions were relatively close to the ones of the intended application. No major degradation was observed after the combustion chamber tests, which demonstrates the potential of this type of FGM for the application.In parallel, a study was carried out about the improvement of the ceramic part of the FGM. Indeed, the thermal expansion coefficient of the chosen metal is twice lower than the one of the chosen ceramic. Thus, and despite the presence of graded layers in-between the metal and the ceramic, high thermomechanical stresses occur at the interfaces between the different layers of the FGM. Thus, a key point of this study consisted in the understanding of the influence of the ceramic composition, and in particular of the amount and nature of the rare earth oxide, on the thermal expansion coefficient. In addition, ionic conductivity and thermal conductivity measurements most accurately reflect the role of thermal and environmental barrier coating of the pure ceramic layer upon the FGM. It has been shown that high content Lu2O3 based compositions are the most promising to be used for the ceramic composition of the FGM. The last part of this thesis was dedicated to study the possibility to heal the cracks observed in the ceramic, which came either from the thermal treatment, either from the thermal tests. Thus, an yttrium disilicate was introduced in the pure ceramic layer of the FGM directly during the elaboration process with APS. Its influence on the resistance of FGM under harsh thermal and environmental conditions was finally reported. In particular, the presence of this disilicate is responsible of chemical transformations in the FGM during high temperature tests
Fiquet, Guillaume. "Propriétés thermodynamiques de minéraux du manteau supérieur. Calorimétrie à Haute Température et Spectroscopie Raman à Haute Pression et Haute Température." Phd thesis, Université Rennes 1, 1990. http://tel.archives-ouvertes.fr/tel-00626851.
Full textCorniglion, Isabelle. "Synthèse et propriétés de revêtements polyuréthane pour film polyester." Lyon, INSA, 1991. http://www.theses.fr/1991ISAL0049.
Full textThe purpose of this work is to synthesize a polyurethane coating for polyester film to facilitate their processing. The polyurethanes (PU)are chemically cross linked and contain a small amount of siloxane additives which are expected to give sliding properties to the products. Initially, the PU is synthesized without siloxane and the bulk properties, glass transition temperature and dynamic mechanical properties, are studied. The products were found to be homogeneous. The surface properties are characterized by measuring the surface tension and the friction factor. These two parameters are studied as a function of the chemical composition and the bulk properties of the PU. The modification of the surface properties is obtained by the incorporation of siloxane additives in the form of a copolymer. These additives are covalently bound to the network. We studied the influence of the chemical structure comparing the results obtained with a polydimethylsiloxane, PDMS, and a polyphenylmethylsiloxane, PPMS. The influence of the PDMS chain length and the PDMS chain mobility is studied. The measure of the atomic compositions at the surface and of the contact angles between the polymer and water, indicate a siloxane surface enrichment with siloxane concentrations as low as 0. 5% by weight. We found that the friction factors are connected to the bulk and surface properties, and the morphology of the polymers
Bouhanek, Karima. "Oxydation à haute température de superalliages monocristallins." Toulouse, INPT, 1997. http://www.theses.fr/1997INPT016G.
Full textKremer, Stefan. "Propriétés électriques et thermiques des delafossites : le scénario du liquide de Fermi apparent et l'extension de la méthode DMRG aux températures finies." Caen, 2011. http://www.theses.fr/2011CAEN2023.
Full textThis work aims to propose techniques to access physical properties at intermediate temperature scales. These methods include both numerical ones on the one hand and analytic ones on the other. The former ones operate within the framework of the density matrix renormalization group aiming to characterize a system depending on temperature by a set of states. The latter ones are applied to the density of states of slightly modified two-dimensional systems which are believed to describe the delafossite compounds. These materials recently attracted a huge interest due to their thermoelectric properties, but have revealed a behavior at intermediate temperatures resembling a Fermi liquid one. This behavior is examined with the proposed methods. Furthermore, it is shown that properties of the density of states as well as the charge carrier density of those materials can be extracted from a careful study
Feraille-Fresnet, Adélaïde. "Le rôle de l'eau dans le comportement à haute température des bétons." Marne-la-vallée, ENPC, 2000. http://www.theses.fr/2000ENPC0007.
Full textSince 1996, three fires have been counted in tunnels in Europe. During each of these accidents, the temperature reached by the structure has been estimated between 800°C and 1200°C. Beside these spectacular accidenta! situations, there are many other situations in which concrete structures are submitted to high temperatures during their regular use. Several research work has been undertaken for a better understanding of the behaviour of concrete submitted to high temperatures and the physical phenomena involved. This PhD Thesis takes ddwn as part of this research work and develops, more particularly, the role of water in the material submitted to heating up to high temperatures. At first, we are interested in the role of water inside a material crack, during heating. We have established an original analytical solution giving the liquid-vapour repartition and the stress intensity factor, as fonctions of crack's length, water molecules contained in the inner of the crack and temperature. Then, we are able to study the crack stability. In the second part, we propose to approach the studied phenomena using the non saturated porous media theory. We present a thermo-hydro-chemical model which permits to describe the concrete behaviour under thermal loading. The material microstructure is defined using a "porosimetric surface". Each pore is characterised by two radii: the pore radius and the access radius into the pore. With this description, the zone of pores saturated by liquid is astate variable. We also introduce the concept of kinetic dehydration, clearly lighted by experimental studies. An hypothesis of erosion of the solid phase by dehydration permits to link the evolution of microstructure and of the zone of pores saturated by liquid to the mass of water created by dehydration
Dias, de Moraes Poliana. "Influence de la température sur les assemblages bois." Nancy 1, 2003. http://www.theses.fr/2003NAN10157.
Full textThe more generalized use of wood for building raises concern for fire safety. The current standards require the structure stability for a minimum time to ensure the building evacuation and the fire fight. Considering that the fire endurance of wood is well-known, the stability requirement is mainly reduced to the understanding of the behaviour of wood joints on fire. The aim of this work is to study the behaviour of single-dowel timber joints and it is divided into three parts. The first part is a study of the influence of temperature on the modulus of elasticity and on the embedding strength in a range between 20 and 300 °C. In the second part the wood charring and the influence of a metallic dowel embedded in wood, is studied. In the third part, the fire behaviour of single-dowel wood joints is tackled. The first two studies have provided mechanical and thermal data to allow the development of a model to simulate the joint behaviour and its fire endurance before fracture
Gelis, François. "Fonctions de corrélation en théorie des champs à température finie : Aspects formels et applications au plasma de quarks et de gluons." Phd thesis, Chambéry, 1998. http://www.theses.fr/1998CHAMS028.
Full textVerdet, Mathieu. "Etude du comportement à long terme de systèmes d’assemblages par goujons collés en conditions climatiques variables." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0447/document.
Full textGlued-in rods have successfully been used for connections or reinforcement of timber structures. With the development of tall and large timber buildings and new products such as Cross Laminated Timber (CLT), there is an increasing need for connections that provide high stiffness and strength. Timber connections using glued in rods have a general aesthetic appeal, and take advantage of the structural adhesives that provide a high stiffness and load capacity. During the last 30 years, multiple applications have been developed for renovation and new construction. In parallel, numerous investigations have characterized the mechanical performance of these connections, but harmonized design rules are not available. A lack of knowledge on the multiple-rod connections, on the choice of adhesives, on long-term effects and on the control of quality is identified by a recent study and must be investigated before a new submission to Eurocode 5. This thesis is performed in the framework of collaboration between Université de Bordeaux (France) and Université Laval (Canada). Objectives are focused on the mechanical performance of adhesives and glued-in rod connections under elevated temperature, on the development of creep tests and the investigations of multiple-rod connections. This study combines experimental and finite element modelling results, which are presented in the form of scientific articles. A Dynamic Mechanical Analysis (DMA) on one polyurethane (PUR) and one epoxy (EPX) adhesives followed by static tensile tests on the connections with small-diameter steel glued-in rods have been conducted at different temperatures. High differences in stiffness are observed between the two adhesives. Glued-in rod connections with the EPX and PUR adhesives demonstrate significant losses of stiffness and resistance beyond 40°C, before the glass transition temperature of the adhesive. Following the outside temperature, connections must be insulated to prevent excessive slip and risk of failure at the Serviceability Limits State (SLS) and at the Ultimate Limit States (ULS). Few data on the long-term effects are available in the literature. In this work, 12 campaigns of creep tests, adding time effects to previous work, have been performed. Glued-in rod connections were tested during one to two months in a conditioning room where temperature and relative humidity were controlled or in a room with a variable climate representative of service class 1. Disparities were observed between EXP and PUR. Creep tests conducted at 20°C and 50°C revealed an important role of the temperature, particularly for SLS. Creep tests in variable climate illustrated the sensibility of connections to the temperature and humidity variations. The stiffness and stress distribution in multiple-rod connections were investigated. First, a 3D model was developed to observe the influence of the wood orthotropy on the stiffness and stress distribution in a connection with a single rod. Then, the model was extended to multiple-rod connections to simulate different loads and boundary conditions. Finally, a prototype of a connection with multiple glued-in rods was tested
Nonnet, Emmanuel. "Etude de la température ambiante à 1600 °c, par méthode ultrasonore, de réfractaires monolithiques." Paris 6, 1999. http://www.theses.fr/1999PA066374.
Full textFares, Hanaa. "Propriétés mécaniques et physico-chimiques de Bétons autoplaçants exposés à une température élevée." Phd thesis, Université de Cergy Pontoise, 2009. http://tel.archives-ouvertes.fr/tel-00447159.
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