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Bourgés, Cédric. "Synthèses, analyses structurales et propriétés thermoélectriques de matériaux sulfures". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC237/document.
Pełny tekst źródłaThe work presented in this thesis focuses on the synthesis and the structural/physicochemical characterizations of sulfide compounds with thermoelectric properties. Several families of sulphide compounds have been studied with the aim of developing and/or optimizing their thermoelectric performances.A binary compound, TiS2, was synthesized by mechanical alloying followed by a densification using Spark Plasma Sintering (SPS). The structural characterizations have revealed the effect of the elaboration on the microstructure and stoichiometry of the compound. This process induces a considerable reduction in the thermal and electrical conductivity of the material which hindered the optimization of the figure of merit. The ternary compound Cu4Sn7S16 was then developed according to two synthetic routes (conventional and mechanical alloying). It has been demonstrated that this semiconductor compound has a complex structure which promotes an intrinsic low thermal conductivity. The influence of the non-stoichiometry on the thermoelectric properties has been reported. Finally, the CuCoxTi2-xS4 and Cu26V2Sn6S32 compounds were the last interesting results presented. These compounds show metallic transport properties with high power factors. The synthesis and the influence of the Co content on the electronic transport properties have been discussed on the CuCoxTi2-xS4 compound. The effect of mechanical alloying and densification conditions were related to the transport properties of the Cu26V2Sn6S32 compound. Substantial improvement of the thermoelectric performances as reported.These various studies open interesting perspectives for the development and optimization of sulfide compounds for industrial application
Lorrain, Olivier. "Analyses expérimentales et numériques du procédé de soudage par friction malaxage fsw". Paris, ENSAM, 2010. https://pastel.archives-ouvertes.fr/pastel-00515112.
Pełny tekst źródłaThe Friction Stir Welding (FSW) is a solid state welding process, without melting. The weld is fabricated thanks to the action of tool made of a shoulder and a pin, positioned at the interface of the two pieces to be welded. The tool as two roles : heating of the material by friction of the shoulder, mixing of the material due to the pin. This thesis work is made within the partnership between Arts et Métiers ParisTech and Institut de Soudure. Its goal is to develop a FSW simulation model in order to decrease experimental trials required to optimize the process. Therefore, some points have been treated in this manuscript. Experimental analysis of thermal cycles and material movements in the case of unthreaded tools has been carried out. This situation allows (1) to make the comparison with numerical simulation easier and (2) to be in the case of worn tools. Formulations (lagrangian, eulerian, ALE) analysis in order to choose the more appropriate to take material flow into account has allowed to select an eulerian formulation (implemented in the FLUENT software) to estimate thermal and kinematical fields in the steady state. The set up of the numerical model in the FLUENT software is presented. We have studied the influence of numerical parameters on the results and proposed an identification strategy for some parameters which are not reachable experimentally. A detailed comparison between our experimental results and the ones from our simulations have been performed with success. The study of the influence of the process parameters (feed rate, rotating speed) and of the pin geometry on the kinematical and thermal fields has highlighted the link between velocity field and the presence of tunnel type defects
Barichard, Anne. "Enregistrement et analyses physico-chimiques de réseaux dans des matériaux composites polymères-points quantiques". Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28504/28504.pdf.
Pełny tekst źródłaKedowide, Yannick-Ariel. "Analyses expérimentales et numériques du comportement hygrothermique d’une paroi composée de matériaux fortement hygroscopiques". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAA015/document.
Pełny tekst źródłaMore stringent thermal regulations, made necessary the inclusion of mass transfer in building walls and their interaction with heat transfer, particularly for those composed of porous and highly hygroscopic materials.The experimental device consists of two walls mounted and tested on PASSYS orientable cells, with controlled indoor environment, located on the CEA-INES site in Le Bourget du Lac. The wood framed walls, with a wood fiber insulation were tested under different internal and external conditions, depending respectively on internal monitored temperature and humidity, or orientation. The one-year long experimental measurements have shown the influence of moisture fluctuations on the thermal behavior of the tested walls, and also the influence of temperature on the moisture in the walls.A numerical model was used to simulate the phenomena observed in experimental conditions. The model, developed on DYMOLA was firstly validated by a comparison with other existing numerical models, during a benchmark on experimental measurements under controlled conditions. It was then used to simulate experimental sequences on external conditions of this work. Comparing the numerical and experimental results have shown a correlation of the temperature measurements, but a difference for the moisture measurements. Parametric adjustments showed an overestimation of the Hygric inertia combined with an underestimation of the vapor permeability of the numerical model compared to experimental sequences. A mismatch of material properties such as reflected generally in the numerical models with the experimental conditions in which they are recorded is underlined
Massué, Nicolas. "Optimisation de l'outil de galetage des vilebrequins par simulation numérique et analyses expérimentales". INSA de Rouen, 2006. http://www.theses.fr/2006ISAM0023.
Pełny tekst źródłaCohen, Zina. "Analyses de la composition de matériaux d’écriture dans des manuscrits de la Génizah du Caire". Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLP024.
Pełny tekst źródłaThis doctoral project addresses the composition of writing materials in a group of manuscripts written during the 11th century, found in the Cairo Genizah. This study sheds light on the production of the manuscripts and uncovers patterns in the use of different writing materials in a statistically relevant number of documents. This study is based on an interdisciplinary strategy: using disciplines coming from the humanities coupled with scientific observations using a non-invasive, transportable protocol. The examination protocol consisted of near-infrared imaging to identify the type of ink used, and X-ray fluorescence spectroscopy for the elemental characterisation. After processing, the results were compared with the available descriptive information for each manuscript to reveal patterns of use
Ledru, Yohann. "Etude de la porosité dans les matériaux composites stratifiés aéronautiques". Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT048G/document.
Pełny tekst źródłaLong fiber reinforced epoxy matrix composite laminate manufacturing process is divided into several stages. The most critical one is the polymerization stage. If not optimized, defects in the bulk material such as voids can occur. The aim of this work is to investigate the void formation and evolution processes in order to improve the thermoset laminates quality in minimizing the void ratio. Two phenomena causing void formation have been identified. The first is the mechanical entrapment of gas bubbles between prepreg plies during the lay up. Second is a thermodynamical one. Solvents and humidity absorbed by the prepreg during its manufacturing can be evaporated by increasing the temperature. Then, it has been shown that the vaccum bag lay up permeability in combination with the vaccum pressure could favour the gas washing out. In parallel, thermo-mechanical and diffusion models are coupled to obtain an accurate void size prediction along temperature and pressure applied during the polymerisation. In fact, these two parameters induce variations of the gas bubble radius inside resin. The first experimental results seem to validate qualitatively the calculated void size behaviour. Indeed, hydrostatic pressure imposed during polymerization plays a very important role on gas bubble shrinkage. Finally, a new experimental setup using image analyses has been developed to measure as accurate as possible the volume void ratio. Under specific conditions, stereology allows to extrapolate 2D results to 3D ones. Void ratios obtained with this method are in good agreement with acid digestion results. Complementary morphometric studies on void shapes have given new information about the heterogeneous void distribution in the specimen and also on the statistical void size distribution versus polymerization conditions
Halitim, Foudil. "Etude des propriétés mécaniques et analyses physicochimiques de l'alumine polycristalline implantée par différents ions métalliques (Ti,Cr,Ni)". Lyon, INSA, 1994. http://www.theses.fr/1994ISAL0005.
Pełny tekst źródłaIon implantation is among the most recent technics for surface treatment used to improve mechanical properties of ceramics materials. The study of ion implantation in polycristalline alumina with titanium, chromium and nickel, has been undertaken for two principal objectives : The first one, the study of the mechanical properties such as the hardness and the toughness by Vickers indentation method, show the improve of these properties in relation with the different parameters used ( fluence, temperature of heat treatment ). The second one, a physico-chemical study of the treated surface using SEM and XRD techniques to explain the evolution of the mechanical properties of ion implanted surface and correlate them with the hardness and toughness parameters obtained from Vickers indentation of the sample
Haddad, Mohamed. "Développement d'un procédé d'enroulement filamentaire adapté aux matériaux composites sandwich et caractérisation mécanique des matériaux". Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0031.
Pełny tekst źródłaComposite materials, and especially sandwich structures, have been studied for decades. Indeed, the association between lightness and resistance of these structures leads to the development of their use. Their manufacturing method and their characterization remain as essential points in most studies. This work is part of the FUI SOLLICITERN project, which aims to design a composite water treatment tank for vehicles intended for this purpose. As a first step, and based on the classical filament winding principal, we aim to search designs that are best adapted to the fabrication of a curved sandwich material on a cylindrical mandrel, while respecting the process parameters of and their influence on structural properties. Since an optimal solution was validated, the constituent materials were studied by measuring mechanical properties. The objective is to help our industrial partner to validate a manufacturing solution and verify that such properties are the expected ones. For that, several static and dynamic characterizations were carried out on curved samples manufactured by the optimized process designed for our application. This part includes various experimental tests in order to validate the structure behavior with the most appropriate dimensions and material combinations, taking into account the manufacturing process. At the end, the best structural configuration is retained for the first tank prototype fabrication
Chabchoub, Manel. "Contributions à la mécanique de la rupture des matériaux composites thermoplastiques à haute température : analyses expérimentales et numériques". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMIR18/document.
Pełny tekst źródłaThe present work was aimed at investigating the fracture mechanics in woven-ply TP (PPS) based laminates at T > Tg/c/pps. A fractography analysis and microscopic observations of fracture surfaces were used to apprehend the damage mechanisms in C/PPS at high temperature (HT) in the presence of a crack. For quasi-isotropic laminates (elastic brittle behavior), several techniques were used to investigate the tenacity at initiation and propagation. In particular, the acoustic emission showed to be particularly relevant as it allows to detect the crack initiation, propagation but also to follow the evolution of the damage. For cross-ply laminates (ductile behavior), an approach based on the calculation of integral J using the load separation method was used. This method showed its capability to provide the J-R curves of composites with very ductile HT behavior for different crack length over specimen width ratios a/W. Numerically, a linear spectral viscoelastic model and a generalized Norton viscoplastic model were used to account for the time-dependent behavior of C/PPS composite laminates at HT. To precisely evaluate the fracture parameters in TP-based laminates, a study on the mesh type and its refinement was carried out. Finally, based on the selected mesh and using the finite element code Cast3m, the Gθ method was applied in order to test its capability to determine J for different loading levels
Brach, Stella. "Strength properties of nanoporous materials : theoretical analyses and molecular dynamics computations". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066618.
Pełny tekst źródłaThe main objectif of the thesis consisted in investigating strength properties of nanoporous materials by means of theoretical and numerical approaches. In the framework of homogenization methods, novel macroscopic strength criteria have been established via a non-linear homogenization procedure and a kinematic limit-analysis approach. Resulting yield functions allowed to take into account void-size effects on nanoporous materials strength properties, thereby resulting in a strong enhancement of available estimates. Furthermore, aiming to funish effective benchmarking evidence for the calibration and/or the assessment of theoretical models, molecular-dynamics based computations have been carried out on in-silico single crystals embedding spherical nanovoids, simulation domains undergoing multiaxial strain-rate boundary conditions. With respect to available numerical studies, proposed results clearly showed the influence of all the three isotropic stress invariants on computed material strength surfaces. Finally, with the aim to account for physical indications coming from numerical simulations, a ductile nanoporous material with a general isotropic plastic matrix has been investigated via a limit analysis approach, by referring to a modified version of the bigoni strength criterion. The limit state of a hollow-sphere model undergoing isotropic loadings has been exactly determined. Correspondigly, a novel strength criterion has been analytically established in the case of axysimmetric boundary conditions
Draidi, Zakia. "Renforcement et réparation des coques métalliques par matériaux composites (TFC) : étude du comportement au flambage : analyses expérimentales et numériques". Lyon, INSA, 2005. http://theses.insa-lyon.fr/publication/2005ISAL0032/these.pdf.
Pełny tekst źródłaExperience has shown that, steel or reinforced concrete shells structures, exposed to severe environmental attacks such as corrosion, or to cyclic load-induced stresses greater than design stresses, or to accidental overloads, are hence subject to damage. The serious deterioration of materials, coupled to design errors or/and to accidental overload can lead to catastrophic failures; or at least, because of the propagation of the damage, to diminution of the structure’s lifetime. It is now of a fairly common practice to repair structures as it is non- expensive and non obstructive upgrading procedure. One of the common techniques for repairing and strengthening steel shells is to weld rings, stringers or local steel reinforcement. Carbon fiber reinforced polymer (CFRP) has established a strong position as an effective mean for the repair and rehabilitation of infrastructures. Composite materials, thanks to their high strength, high stiffness, resistance to corrosion and low weight, can be of great interest in civil engineering structures (generally concrete beams). Their use is particularly interesting, especially in order to increase the structural performance, but also because of the ease to forming, the speed of installation, the optimization possibility (direction’s reinforcement choice) and the multifunctional (strength, anti-corrosion, tightness). However, the use of CFRP in the repair and reinforcement of steel or concrete shells is a new concept that has the potential to improve the way we repair shells. In our studies we show the benefits of using CFRP for the reinforcement of shells submitted to axial compression or combined loads like internal pressure, axial compression and bending. A large experimental and numerical study is carried out on steel cylindrical shells reinforced with the CFRP at different radius to thickness ratio. We show that the load capacity can be enhanced more than 50%. Numerical simulations are also conducted using finite element approach
Bimbault, Laurent. "Analyses des contraintes résiduelles, de la microstructure et des constantes élastiques de multicouches métalliques élaborées par PVD". Poitiers, 1998. http://www.theses.fr/1998POIT2251.
Pełny tekst źródłaPriser, Mathieu. "Analyses multi-échelles du comportement en fluage d'alliages de zirconium". Phd thesis, Université de Bretagne Sud, 2011. http://tel.archives-ouvertes.fr/tel-00642008.
Pełny tekst źródłaBerdoulay, Maïté. "Analyses physico-chimiques et microbiologiques de façades en pierre exposées aux embruns marins du golfe de Gascogne". Pau, 2008. http://www.theses.fr/2008PAUUA001.
Pełny tekst źródłaDuring this thesis, we developed a DNA-based molecular method adapted to the genotyping of microorganisms living on building stone. Once calibrated, the method was tested by characterizing microbial biofilms from two stony types of construction frequently encountered on the coast of the golfe de Gascogne. This analysis showed that the method is effective to reveal the microbial biodiversity of biofilms. It was also used to better understand the evolution of the microbial biodiversity during stone colonization, on a period of 2 years. This analysis allowed us to identify pioneer microorganisms, some of them being unexpected, as well as secondary colonizers
Livingstone, Smith Alexandre. "Chaîne opératoire de la poterie: références ethnographiques, analyses et reconstitution". Doctoral thesis, Universite Libre de Bruxelles, 2000. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211722.
Pełny tekst źródłaCaurant, Adrien. "Développement d'une méthode de production de matériaux de référence pour le contrôle de la qualité des analyses des composés organiques volatils réalisées en air intérieur". Paris 7, 2011. http://www.theses.fr/2011PA077036.
Pełny tekst źródłaAir quality is a major social issue. Among the many compounds that could be harmful for Human health, Volatile Organic Compounds (VOCs) belong to the most monitored and regulated pollutants. They are present in indoor air, often at concentrations higher than those encountered in ambient air. Therefore, man national and international studies have emerged to ensure their monitoring in enclosed spaces. They usually use common analytical methods: sampling on sorbent tube and analysis by thermal desorption and gas chromatography. To ensure traceability and comparability of measurement results, it is essential to have common references: it is the role of matrix certified reference material (CRM). However, few CRM fully traceable to the International System of Units (SI), containing VOCs at concentrations encountered in indoor air are available. The purpose of this thesis has been to develop a production method for this kind of CRM. After having developed, optimized and validated the analytical method (thermal desorption / gas chromatography / flame ionization detecter), two methods for loading sorbent tubes have been developed. First, an automated loading method by vaporizing a standard solution, allowing the deposit of 500 ng ± 5%of benzene. Then, a method by sampling a standard gas mixture has enabled the production of a CRM containing 500 ng ± 2% of benzene. Studies of stability, homogeneity and an interlaboratory comparisons allowed the validation the produced CRM
Zhiou, Seifeddine. "Réaction à l'état solide d'un film mince de Ni(Co) avec InGaAs : analyses microstructurales". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY067/document.
Pełny tekst źródłaThis thesis focuses on the microstructural analysis of intermetallics formed by solid-state reaction between a thin layer of Ni (Co) metal and an InGaAs substrate and was carried out in the framework of contact development for sub-10 nm MOSFET but have also photonic applications. This work includes a part related to the development of an X-ray diffraction methodology adapted to highly textured compounds and two distinct parts in which we describe and discuss the experimental results.The microstructural study (phase, texture ...) of intermetallics obtained by solid-state reaction is complicated due to the formation of transient metastable, often non-stoichiometric and mechanically stressed phases. These phases have generally very marked crystalline orientations (crystallographic texture). Because of this microstructural complexity, these intermetallic have often been not fully characterized and there is little knowledge about their structure and formation. Moreover, and to fully characterize the Ni-In-Ga-As system without omitting phases or textures, we have contributed to the development of a comprehensive method of rapid measurement by X-ray diffraction to reconstruct large 3D maps of the reciprocal space. The collected data through this method are reconstructed to extract either diffraction diagrams called "detextured" diagrams or pole figures ... which allows a semi-quantitative analysis of the intermetallic microstructure.In the first part of the experimental results, we focus on the characterization of intermetallic formed through Ni / InGaAs / InP stacks and annealed ex situ at different temperatures. We describe the formation of the intermetallics, textures, and structural parameters. We note some aspects which vary depending on the annealing temperature such as the texture anisotropy, the stoichiometry of intermetallic and range of thermal existence and propose hypotheses that can explain the evolution of these phenomena. The studies on InP substrates were compared to results obtained for similar intermetallic made on GaAs / Si substrates. Indeed, the Si substrates are targeted for industrials to achieve logic compounds III-V channel large-scale (on 300 mm wafers). Then, we compared the metallization of the InGaAs layer in the case of pure Ni metallization with the results when an alloying element (cobalt) was added to the Ni layer. The microstructural analysis revealed several differences especially texture differences. These differences were interpreted on the basis of thermodynamic considerations, but also on the basis of structural alignment of the two layers together which are also linked to more kinetic aspects.In the second part of this work, we present the analysis results of studies performed by in situ 3D Reciprocal Space Mapping on the ESRF synchrotron in Grenoble. We followed the formation and stability of the intermetallics by real-time X-ray diffraction measurements, for different kind of samples: Ni (7 nm and 20 nm) / InGaAs / InP and Ni0.9Co0.1 (20nm) / InGaAs / InP, using ramp annealing... Then, we performed isothermal annealings for Ni(20 nm) / InGaAs / InP samples. These measurements, coupled with assumptions on the intermetallic growth, allowed us to extract the kinetic parameters for the formation of the first phase of the intermetallic. The observed textures and their evolution during in situ thermal annealings are different than ex situ annealing. This can be explained by a different mode of annealing in the case of in situ where the kinetics of the system is slower, thus favoring the most stable structures and textures
Graja, Fatma. "Influence des conditions d'interfaces d'un milieu poreux saturé sur la propagation des ondes ultrasonores : analyses acoustique et diélectrique". Thesis, Le Mans, 2017. http://www.theses.fr/2017LEMA1032/document.
Pełny tekst źródłaThis work is part of a collaboration between the University of Sfax and the University of Maine. The thesis entitled "Influence of the interface conditions of a saturated porous medium on the propagation of ultrasonic waves: acoustic and dielectric analysis". The work presented in this dissertation examines theme chanisms that can be reproduced in a porous medium saturated by an incompressible fluid when subjected to a pressure gradient for the acoustic studyand an electromagnetic field gradient for the dielectricstudy. Consequently, the present paper is interested in presenting two techniques of characterization:i) Acoustic characterization where Biot's theory was adopted to understand the mechanisms of propagation of ultrasonic waves in saturated porous materials and to study the influence of changing interface conditions onreflection and transmission coefficients. The presence of a flat defect in the volume of the material has be entreated. The study of the influence of the presence of several spherical inclusions on the modification of the lines of velocity fields was presented by proposing a model of tortuosity adapted according to the nature of the inclusion and the porous medium host (homogeneityand anisotropy).ii) The dielectric analysis which allows to describe the internal structure and the interaction between the solidand the saturating fluid. Dielectric measurements were carried out on porous silica ceramics identical to thoseused in ultrasonic characterization in order to study the influence of the state of the lateral surfaces of the sample on the interaction between the saturating fluid and the surfaces of the porous structure.The results make it possible to demonstrate an analogy between the behavior of the inclusion in the velocity field of the fluid and that of a dielectric sphere in a uniformelectric field. Acoustic experiments and dielectric measurements (spectroscopy) were carried out and compared with numerical simulations and theoretical models in both parts of the study
Picot, Florent. "Optimisation des conditions de mise en oeuvre de la jonction Ti/Al par FSW : influences des propriétés mécaniques et metallurgiques des interfaces". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC283/document.
Pełny tekst źródłaThese PhD works are about heterogeneous friction stir welding between titanium (Ti grade II) and aluminum (AA1050). Research is focused on lap joining configuration in order to limit the process stress. Taguchi's design of experiments determined parameters influence for a defectless welded junction. The rotational speed of the tool has been identified as the parameter which influences the most the defects generation. Parameters combinations are linked to a heat input coefficient. The thermal conductivity difference between the two material leads to a thermal gradient in the thickness up to 80°C. No junction mechanical strength optimization has been revealed by tensile and bending tests.Microstructural analyses were performed on the welded junction in order to understand the mechanical properties. One single intermetallic compound TiAl3 nucleates in the titanium volume and ensures interface chemical continuity. Further analyses with EBSD (SEM) supplemented by ASTAR™ (TEM) method for the smaller scales have completed the observations. The process generates aluminum severe plastic deformation which induces a grain size reduction with a gradient following the configuration thicknessAll observations brought clues to understand friction stir welding phenomenon leading to microstructural evolution to realize a better link between resulting microstructure and macroscopic properties
Cintosun, Esen. "Analyses expérimentale, numérique et optimisation de traitements acoustiques multicouches à base de matériaux viscoélastiques et poreux pour réduire le bruit à bord de l’avion". Thèse, Université de Sherbrooke, 2011. http://hdl.handle.net/11143/8769.
Pełny tekst źródłaAbstract : The project is made up of three main parts. The first part involves a comprehensive experimental and numerical analysis of viscoelastic damping materials as acoustic treatments to aircraft fuselage structures. The second part involves numerical and experimental acoustic comparison of viscoelastic damping material to equivalent mass. And the third part is a parametric study of equivalent mass for the effects of mass location, density and size. The goal of the project is to identify the vibroacoustic effect of viscoelastic material damping of fuselage skin, and develop possible alternatives to damping. The insulation systems (typically used on aircraft) that are made up of porous materials with or without viscoelastic damping material or equivalent mass were called sound packages throughout this document. The viscoelastic damping material and equivalent mass both incorporated in sound packages were acoustically compared. Fiberglass and open cell foam were used as porous materials. The viscoelastic damping material used in this study is constraining layer damping and abbreviated as CLD. The equivalent mass was an impervious screen. Both representative Aluminum and carbon composite fuselage skin structures were treated with sound packages as part of the comparison. The vibroacoustic performance indicators were used to characterize the sound packages. The indicators were airborne insertion loss (ABIL), structure borne insertion loss (SBIL), turbulent boundary layer insertion loss (TBLIL), average quadratic velocity (AQV), damping loss factor (DLF), absorption coefficient, and radiation efficiency. Diffuse field acoustic excitation was used to obtain the vibroacoustic indicators of ABIL and absorption coefficient. Mechanical excitation was used to obtain SBIL, AQV, DLF, absorption coefficient, and radiation efficiency. Turbulent boundary layer excitation was modeled to obtain TBLIL. The numerical methods of finite element method (FEM) and transfer matrix method (TMM) were used to calculate all of the above vibroacoustic performance indicators. Experimentally, ABIL, SBIL, AQV, DLF and radiation efficiency were measured. Experimental modal analysis was also performed to characterize representative Aluminum and carbon composite fuselage skin structures. Based on the numerical analysis, equivalent mass generated a double or multiple (in case of double wall layer configuration) wall effect and hence became an effective acoustic insulator as part of sound packages at mid to high frequencies. Even at coincidence frequencies (in case of the representative carbon composite fuselage skin), the equivalent mass layer was more effective than viscoelastic damping material. However, the drawback was the occurrence of the double wall resonance at lower frequencies which compromised the effectiveness. Nevertheless, the parametric study of equivalent mass revealed that equivalent mass is superior to viscoelastic damping material at reduced weight in term of vibroacoustic performance indicators of overall ABIL/SBIL/TBLIL in the frequency range of 100 to 6300 Hz and mean ABIL/SBIL/TBLIL in SIL (octave lk, 2k, 4k Hz) frequency range.
Licenziati, Francesca. "Recherche sur les matériaux et les techniques mis en œuvre dans les mosaïques en Méditerranée Orientale : les tesselles vitreuses des mosaïques hellénistiques de Délos : l’apport des analyses archéométriques". Thesis, Paris 10, 2016. http://www.theses.fr/2016PA100122.
Pełny tekst źródłaThis theses has comprised an experimental part involving the application of archaeometric analyses on glass and faience tesserae of the Hellenistic mosaics from Delos both in situ and in laboratory. Moreover it has involved a bibliographic research concerning on the one hand the use of vitreous materials in the Hellenistic mosaics in the Mediterranean and on the other hand the archaeometric studies on glass and faience of the considered period. This research allowed to enrich the knowledge about the mosaics from Delos through the physico-chemical characterisation of their vitreous tesserae and to contribute to the question concerning the supply of glass and faience by the mosaicists. In addition, as regards glass, the combination and comparison of the compositional data obtained on the tesserae from Delos during this study and those concerning coloured glass found in the bibliography has permitted to formulate some hypotheses concerning the production organisation/system of coloured glass during the Hellenistic period. The analyses of a large number of glass tesserae highlighted a peculiarity of blue and turquoise tesserae which allowed us to hypothesise that a lead-rich antimony ore was used for their opacification.Finally, the application of non-invasive analytical methods using portable instruments permitted to evaluate the limits and advantages of this type of approach in the study of vitreous tesserae. To overcome some problems in the calculation of weathered tesserae composition provided by the software of the XRF instrument used, an alternative calculation procedure involving the use of PyMca software has been developed
Leroy, Stéphanie. "Circulation au moyen âge des matériaux ferreux issus des Pyrénées ariégeoises et de la Lombardie. : Apport du couplage des analyses en éléments traces et multivariées". Phd thesis, Université de Technologie de Belfort-Montbeliard, 2010. http://tel.archives-ouvertes.fr/tel-00598796.
Pełny tekst źródłaMerle, Guillaume. "Modélisation algébrique des arbres de défaillance dynamiques, contribution aux analyses qualitative et quantitative". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2010. http://tel.archives-ouvertes.fr/tel-00502012.
Pełny tekst źródłaDaher, Céline. "Analyse par spectroscopies Raman et infrarouge de matériaux naturels organiques issus d'objets du patrimoine : méthodologies et applications". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00742851.
Pełny tekst źródłaParis, Céline. "Méthodologies spectroscopiques pour l'étude de matériaux : objets du patrimoine de la fin du 19ème au début du 20ème siècle". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2004. http://tel.archives-ouvertes.fr/tel-00711236.
Pełny tekst źródłaBouyon, Yenda Tracy Christ. "Synthèses, analyses et applications de systèmes à base de nanoparticules hybrides Or/Thiol". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4761.
Pełny tekst źródłaThis Ph.D. work developed the controlled synthesis and purification of hybrid gold nanoparticles AuNPs, stabilized by organic thiols that are tuning their surface properties. The targeted applications are the catalysis and in the biomedical field, requiring a thorough control of the introduced nanoobjects. Syntheses of the organic AuNPs were developed from the Brust method, using 4-hydroxymercaptophenol or 4-methylmercaptophenol, leading to stable hybrid gold nanoparticles of size 2 nm. Purified fractions were characterized using TEM, UV-visible, NMR and TG analysis, issuing key data about the gold core, the organic layer and their interactions. Among the different fractions of AuNPs, the organic thiol ligands appeared to be assembled either as a monolayer or a multilayer pattern. A new direct route for synthesis of aqueous AuNPs of size 4 nm, stabilized by 4-hydroxymercaptophenol, has been developed. The AuNPs were purified using dialysis and characterized by TEM, UV-visible, NMR and TG analysis. Organic AuNPs, exhibiting different surface properties, were impregnated into SBA-15 mesoporous silica. Adsorption isotherms and nitrogen adsorption/desorption studies were in good agreement with the homogeneous distribution of AuNPs and the significant incorporation into the porosity. Finally, exploration of the targeted applications was started. The use of organic AuNPs for alkene oxidation tends to improve the selectivity of manganese salt catalyst. In the biomedical field, the aqueous AuNPs exhibited good dispersibility into biocompatible aqueous solvents. First in-vitro assays involving human sarcoma cells line showed limited cytotoxicity and good cellular uptake
Plougonven, Erwan. "Lien entre la microstructure des matériaux poreux et leur perméabilité : Mise en évidence des paramètres géométriques et topologiques influant sur les propriétés de transport par analyses d'images microtomographiques". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2009. http://tel.archives-ouvertes.fr/tel-00440189.
Pełny tekst źródłaPlougonven, Erwan Patrick Yann. "Lien entre la microstructure des matériaux poreux et leur perméabilité : mise en évidence des paramètres géométriques et topologiques influant sur les propriétés de transport par analyses d’images microtomographiques". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13847/document.
Pełny tekst źródłaThe objective of this work is to develop 3D image analysis tools to study the micronic pore structure of porous materials, obtained by X-ray microtomography, and study the relation between microgeometry and macroscopic transport properties. From a binarised image of the pore space, a complete sequence of processing (artefact filtration, skeletonisation, watershed, etc. ) is proposed for positioning and delimiting the pores. A comparison with available methods is performed, and a methodology to qualify the robustness of these processes is presented. The decomposition is used, firstly for extracting geometric parameters of the porous microstructure and studying the relation with intrinsic permeability; secondly to produce a simplified pore network on which to perform numerical simulations
Souton, Emilie. "Utilisation de biotests in vitro, en complément d’analyses chimiques, pour l’évaluation du danger lié aux matériaux papiers-cartons recyclés destinés au contact alimentaire". Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCK057.
Pełny tekst źródłaFood contact materials (FCM) are a major issue of concern for European packaging and food companies as FCM must be produced in accordance with the good manufacturing practices and be in compliance with European Regulation 1935/2004/UE. FCM could be a potential source of food contamination because they could release chemicals by a phenomenon called migration. Among FCM, paperboards are the most common materials after plastics and the recycling rate of paperboards is high and was 72% in Europe in 2015. In addition to started substances also called Intentionally Added Substances (IAS), Non-Intentionally Added Substances (NIAS) such as impurities, degradation products, contaminants from recycled materials etc, are also able to migrate from the FCM to food and many of them are not always fully characterized. Assessing the risk of recycled paperboards FCM is difficult because of NIAS and as recycled paperboards can be complex mixtures of substances. This thesis project uses a methodology combining chemical analysis and in vitro bioassays to evaluate the potential hazard of recycled food contact paperboard extracts. For this study, recycled paperboards have been sampled at different steps a food packaging production chain (the starting paperboard of the beginning of the production chain and the end paperboard issued from the recycling process), extracted with water and the dry matter content was recovered by freeze-drying. Chemical analysis of the extracts was performed by spectrophotometry and by chromatographic methods (HPLC, GC-MS, LC-MS and ICP-MS). Chemical analysis showed the presence of a higher number of substances in the starting paperboard than the end paperboard issued from the recycling process. Among these substances, several natural substances were detected in both extracts such as wood extractives (polymers of cellulose, hemicellulose and lignin, fatty acids, sugars, resin acids and phenols). Other substances identified as additives and contaminants were characterized in both extracts such as bisphenols, phthalates, aromatic amins or mineral oil saturated hydrocarbons. It is important to precise that a large number of the substances of the starting paperboard were not detected in the end paperboard. In parallel to chemical characterization, bioassays were used as relevant tools to identify mechanisms of action and potential “cocktail effects”. A battery of bioassays has been performed using different human cell lines (two hepatic cell lines HepG2 and HepaRG, the hERα-HeLa-9903 cell line and the MDA-kb2 cell line) to check toxicological endpoints which are relevant to low exposure: cytotoxicity, genotoxicity and potential endocrine disruption. No cytototoxic effects of both extracts were observed on both human hepatic cell lines HepG2 and HepaRG neither on the HeLa 9903 cell line; whereas the end paperboard extract had cytotoxic effects on MDA-kb2 cells at the highest tested concentration. However, in the same conditions, the starting and the recycled end paperboard extracts were able to induce oxidative stress in the used cell lines. The results of the genotoxicity study showed genotoxic effects of the starting paperboard and the end paperboards. The DNA damage induced by the starting paperboard in the used cellular models might be repaired by cell repair systems. In contrast, data of this study suggest that the end paperboard was able to induce DNA damage that might turn into chromosomal mutations. Data of the endocrine disruption potential showed that the tested FCM paperboard extracts induced significant agonist and dose dependent estrogenic and antiandrogenic activities in the used cell lines. The correlation of the results of the in vitro toxicological study and chemical analysis offers a relevant strategy for hazard assessment of FCM in order to help manufacturers to manage the risk of NIAS
Buvignier, Amaury. "Caractérisation du rôle de l'aluminium dans les interactions entre les microorganismes et les matériaux cimentaires dans le cadre des réseaux d'assainissement". Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0022/document.
Pełny tekst źródłaAn important part of the deterioration observed in concrete sewer networks is due to biological activity. In this context, calcium aluminate cement (CAC) based material has shown a better durability than ordinary Portland cement, usually used in such context. In literature, hypothesis explaining the better resistance are focused on aluminium. The aim of the project is to characterize the role of aluminium in the interactions between cementitious material and microorganisms. Reactor study and Lab scale aggressive biodeterioration protocol of cementitious material revealed that the better resistance of CAC is due to their lower reactivity and not to a bacteriostatic effect of the material on the microorganisms
Gariani, Gianluca. "Déchiffrer les matériaux, l'origine, et les procédés de fabrication des "Madonne di gesso" : étude technique de reliefs en stuc des maitres sculpteurs de la Renaissance Italienne". Thesis, Cergy-Pontoise, 2019. http://www.theses.fr/2019CERG1027.
Pełny tekst źródłaThe production of devotional reliefs flourished in 15th century Florence, where original marble models from Renaissance Masters were moulded to be reproduced in series. Among the materials mostly used to this purpose was the so-called “stucco”. Despite the wide diffusion of stucco reliefs, details concerning their constitutive materials and manufacturing processes are fragmentary and poorly studied. In the framework of a multidisciplinary project fostered by the Louvre Museum, this thesis explored three research lines in order to: 1) identify and characterise stucco mineral constituents; 2) determine raw material provenance; 3) investigate manufacturing techniques and serial casting processes.A multi-analytical approach was devised to investigate composition (SEM-EDX, PIXE, LA-ICP-MS) and structure (XRD, FEG-SEM, SµCT) of micro samples obtained from 30 representative artworks attributed to 7 Florentine Masters.Results showed that all the artworks are made of a gypsum based stucco (40-44 wt% CaO and 52-56 wt% SO3) with secondary mineral phases (anhydrite, calcite, dolomite, celestine and clay minerals) in few weight percentage maximum.PIXE and LA-ICP MS trace elements analyses, the study of W/P ratio and pores morphology by SEM-EDX and SµCT, pointed out that about 20 reliefs present similar compositional and structural parameters. This confirms the hypothesis of common practices and of a common production centre according to the Florentine attribution of the artworks.A geological survey was performed in 3 quarries in the surroundings of Florence and the provenance of the raw gypsum was investigated by means of geochemical and isotopic composition. In particular synsedimentary clay minerals with variable amounts of K, Mg and Fe, related trace elements (e.g. Ti and REE), and multi isotopic fingerprint (S, O, Sr) have been tested as provenance markers. Usefulness and pitfalls of the approach were verified through a first promising comparison with data obtained on stucco reliefs. Miocene quarries seems to have compatible signature with the ones measured on artworks.Nonetheless, small differences related both to accessory minerals proportions, to trace element contents, and to pores microstructures suggest that some of the stucco reliefs after models of Donatello and A. Rossellino might have been produced following different practices or particularly by using different raw materials. These evidences, corroborated by the activity of these artists in many Italian regions, raise the hypothesis of the production of these casts outside the Florentine area.In parallel, THz-TDI, Xray radiography and Computed Tomography were tested for the non-invasive investigation of the internal stratigraphy of plaster layers possibly revealing different manufacturing techniques.Finally, serial manufacturing techniques were investigated on 3 groups of replicas belonging to 3 models after Donatello & B. Bellano, D. da Settignano and A. Rossellino. Structured light 3D scanner and mesh comparison of the 3D models obtained on stucco casts proved to be a very useful tool. The method allowed to measure millimetric differences of shapes and topography among reliefs stored at the Louvre, Bargello and Bardini Museum. This helped to find direct correlations between casts, to verify which ones were most likely produced with the same mould, and to propose a chronology within the same casting series.Results obtained disclosed new and important insights on the practices of 15th century Florentine botteghe and on the manufacturing of these artworks. This work and the large set of data produced will also provide solid basis for further investigations and will hopefully prompt interest on this topic worth to be studied with increased attention
Yao, Wei-Zhen. "Analyses thermomécaniques multi-échelles expérimentale et numérique pour des empilements de couches minces en microélectronique". Thesis, Tours, 2018. http://www.theses.fr/2018TOUR4023.
Pełny tekst źródłaThe aim of this work is to understand and predict the warpage of silicon wafers during the fabrication process of PTIC microelectronic components. The warpages are partially responsible for several productivity problems. This study is done by coupling analytical calculation, finite element modeling and experimentation. The mechanical characterization of thin films constituting the multi-layered stack has been carried out by an experimental method nanoindentation with the help of a finite element model. The intrinsic stress in the thin films has been determined by coupling measurements of the wafer warpage and a finite element model. The obtained Young’s modulus and intrinsic stress are used to feed the database for calculating the wafer warpage by analytical and numerical approaches. The complexity of the structures (thousands of components in the wafer) required the use of homogenized models to calculate the wafer warpage. These results obtained allow the prediction of the wafer-level warpage in order to optimize the fabrication process flow and therefore reduce the risk of the mechanical problem
Suavet, Clément. "Contribution à la caractérisation physique et isotopique des micrométéorites". Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2009. http://tel.archives-ouvertes.fr/tel-00408022.
Pełny tekst źródłaYang, Jie. "Analyses numériques de la problématique multi-physique des fontis au voisinage d’une digue ou d’un ouvrage linéaire". Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0016/document.
Pełny tekst źródłaGeo-structures such as dams and levees or dikes are subjected to seepage varying in time and space. The water flowing through these porous media can lead to the detachment and transport of part of the soil particles within the structures or their foundations. This problem is usually called internal erosion. The term suffusion, one type of internal erosion, refers to the detachment and transport of finer particles through a coarser porous soil matrix due to seepage flow. Suffusion can modify with time the hydraulic and mechanical properties of the soils and may trigger significant damage on such structures and lead eventually to their collapse. This research attempts to contribute to the design and sustainability of geotechnical and hydraulic engineering structures, with a particular focus on embankment dams, levees, and dikes. It aims to develop a numerical model of suffusion by introducing, on the one hand, the coupling of the hydraulic and mechanical phenomena and, on the other hand, the coupling of erosion and filtration
Rival, Guilhem. "Vieillissement sous irradiation électronique du PolyEtherEtherKetone : optimisation des propriétés électriques pour applications en environnement spatial". Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30073.
Pełny tekst źródłaThis thesis is part of a research concerning the behaviour of polymers in space environment. It has two goals: to study the ageing of PolyEtherEtherKetone (PEEK) under electronic irradiation and to optimise its electrical properties in order to limit surface charge phenomena. For this purpose, PEEK/Short Carbon Fibre composites have been developed. The electrical percolation threshold of the fibres was determined at a volume content of 9 %. As space applications of PEEK require an electrical insulating behaviour, a filler content of 3 %vol was selected. The presence of the fibres improves electronic conductivity at room temperature, even below the electrical percolation threshold. Samples were then subjected to a high-energy electron beam to simulate their ageing in a space environment. Analysis of the irradiated samples revealed two simultaneous ageing phenomena: cross-linking of the amorphous phase and amorphisation of the crystalline phase. Irradiation near the glass transition (165 °C) leads to a higher cross-linking density due to a higher recombination rate of radicals. In composites, fibres limit amorphisation and stabilise the mechanical behaviour evolution. With regard to the electrical properties, ageing induces a decrease in ionic conductivity above Tg. In composites, this decrease is amplified. At room temperature, irradiation at 25 °C and at 165 °C leads to opposite evolutions in electronic transport which are associated with competition between cross-linking and amorphisation. In composites, fibres stabilize the evolution of potential relaxation and always allow a faster flow of electrons
Carré, Méline. "Développement de nouveaux polymères fonctionnels et intelligents, ayant des propriétés optiques modifiables sur demande". Thesis, Mulhouse, 2021. http://www.theses.fr/2021MULH4570.
Pełny tekst źródłaThermoplastics are a class of polymers widely used in industry because of their low processing costs. Pellets of thermoplastic are heated and then the melted thermoplastic can take every shape. Several methods can be used like injection molding, extrusion, thermoforming or 3D printing to give the shape. No solvent is required during the process. The interesting characteristic is that thermoplastics are recyclable, unlike the other class of polymer called thermoset. In fact, the material could be reheated to be remolded several times without affecting the chemical structure. All of these attract the interest of several sectors like medicine, aeronautics or automobile. The aim of this work is to develop smart thermoplastics with new additional properties. Additives are incorporated into the thermoplastic to give stimuli responsive properties. Usually additives are mixed with resin and the ink is applied to the surface or thermoplastics are solved to be mixed with additives. In this study, we want to avoid coating and solvent in order to obtain intrinsic properties by cleaning way. Therefore, additives are mixed with melted thermoplastic. The difficulty is to incorporate the additive and mold thermoplastics at high temperature (from 150 °C to 300 °C) without damaging additives
Pouyet, Emeline. "Nouvelles méthodes de préparation et d'analyse par combinaison de techniques synchrotron hyperspectrales pour l'étude de micro-fragments de peintures et d'autres matériaux du patrimoine culturel". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY088/document.
Pełny tekst źródłaThis project aims at developing a new methodological approach, providing a more efficient and synergetic use of FTIR and X-ray microscopies, for the analysis of painting fragments. Usually, painting fragments are prepared as polished sections and analyses are carried out on the cross-section surface. This sample preparation is easy to handle, however ends into critical constraints regarding feasibility and efficiency of micro-analyses. We propose to explore a different strategy: preparation and analysis of thin sections. These preparation procedures were first optimized and validated with µFTIR, µXRF, µXRD and µXANES. Besides, new methodological capabilities based on full-field/µXANES were assessed. Paintings were ideal candidates for estimating pros and cons of this new strategy for CH materials in general
Monnier, Judith. "Corrosion atmosphérique sous abri d'alliages ferreux historiques : caractérisation du système, mécanismes et apport à la modélisation". Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00369510.
Pełny tekst źródłaWang, Biyun. "Application des analyses par RMN/IRM et gammadensimétrie à la réparationdu béton âgé : étude des transferts hydriques, de l’impact sur l’hydratation du mortierde réparation et sur la durabilité du béton réparé". Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1159/document.
Pełny tekst źródłaThe coating area of steel reinforced concrete structures is subjected during service life time to various aggressive agents (carbon dioxide, chloride ions, etc.), which causes corrosion of steel rebars. Concerning the maintenance, repair works of degraded concrete cover are generally imposed to ensure its integrity and structural safety, and to extend long-term durability. This research aims in exploring moisture transfers which limit the efficiency of repair work during mortar hydration. Microstructure evolution and water profiles are obtained by non-destructive techniques such as Magnetic Resonance Imaging (MRI) and Gamma-Ray Attenuation (GRA) since casting until 28 days. The durability of repaired concrete is involved after the repair procedure. The effect of drying is avoided in this research. Sealed mortar of the same formula is prepared to compare its hydration performance with the repair mortar. Various conventional techniques help to supplement the results obtained by MRI and GRA. The configuration of designed repair systems is shown. Moisture transfers at the interface between the repair mortar and the old concrete are investigated during the repair procedure (0 - 28 days), which allows exploring the mechanisms of physico-chemical couplings. Efficient repair work can be determined for various repair materials, various substrates (initially-saturated or initially-dried), various environmental conditions, etc. Furthermore, total porosity is measured by GRA or by Mercury Intrusion Porosimetry (MIP) after the repair procedure (1 - 2 months). Pore size distribution (PSD) is also investigated by MIP at different positions within the repair systems. Durability indicators (Cl- and CO2) after the repair procedure (> 2 months) present a prevention of chloride penetration and a non-evident influence on carbonation. Evolution is followed during penetration, in order to explore repair efficiency during prolonged service life time. This methodology could also be applied on various systems where exist moisture transfers. For example, a protective layer of Ultra High Performance Fiber-Reinforced Concrete (UHPFRC) on conventional concrete. In conclusion, this methodology is a tool to investigate the repair systems in a systematic and quantitative way, by combining non-destructive and destructive techniques. It is interesting to compare aforementioned systems. Repair efficiency is investigated in order to ensure a long-term durability
Fellah, Clémentine. "Influence de la nature des interfaces carbonées au sein des composites SiC/SiC à renfort Hi-Nicalon S et Tyranno SA3 sur leur comportement mécanique". Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM078.
Pełny tekst źródłaSiC/SiC composites including the third generation SiC fibers with pyrocarbon interphase (PyC) are promising candidates to improve the safety of nuclear reactors, especially for core materials such as cladding and to replace metallic alloys for these applications. Their intrinsic refractory properties, their neutron transparency and their microstructural stability when irradiated or exposed to high temperatures make them attractive for nuclear applications. However SiC fibers and SiC matrix are brittle ceramics. The integrity of the structures can be fulfilled only if the composite is damage tolerant and can acquire a pseudo-ductile mechanical behavior. An interphase is deposited between the fibers and the matrix to provide this damage tolerance of SiC/SiC composites.The ability of SiC/SiC composites to sustain damage is dictated by the fiber/matrix (F/M) coupling mode. The intensity of this coupling can be related to many parameters such as the roughness and the chemistry of the surface of the reinforcement. A carbon layer on the fiberssurface was highlighted by High Resolution Transmission Electronic Microscopy (HRTEM) and by physico-chemical analyses. The characteristics of this carbon layer vary with the fabrication process of the fibers. The impact of this carbon layer on the F/M coupling was investigated by the observation of the local damage mechanisms. To elucidate the local bonding modes governing the damage mechanisms at the F/M interface of these SiC/SiC composites, macroscopic mechanical tests have been coupled with observations of structural modifications occurring in the interface region after loading. Understanding the origin of this carbon layer allowed elucidating the local interaction mechanisms according to these studied materials. These mechanisms depend on the carbon structure of the SiC fibers surface which in turn governs the adhesion between this carbon and the PyC interphase. Thanks to this study, a surface treatment on fibers was developed to optimize the mechanical behavior of SiC/SiC composites, whatever the fibrous reinforcement chosen
Riera, Elisabeth. "Vers une construction raisonnée d’une nouvelle génération de récifs artificiels : Analyses comparatives des facteurs intrinsèques favorisant leur colonisation de la micro à la macro-échelle". Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4001.
Pełny tekst źródłaArtificial reefs are submerged structures deliberately placed on the seabed to mimic some characteristics of a natural habitat, they have been used for thousands of years by fishermen to improve their fishing practices and recently they are also used for the protection or even the restoration of certain marine habitats. Despite these various objectives, there is still a lack of scientific fundaments for determining the quality of these submerged structures in order to assess their effectiveness. The present works, focused on the study of their intrinsic characteristics, namely their materials and their structures. A combined monitoring of the biofilm and the macrofouling on different substrates, supplemented by an analysis of their heavy metal content allowed to highlight the quality of certain substrates used for the construction of artificial reefs. Simple monitoring of the biofilm has proven to be an efficient indicator for highlighting these differences to validate the use of a particular substrate.In addition, the development of a method to assess the complexity and heterogeneity of artificial reefs has enabled us to give a relevant classification of the various existing structures. This standardized method will allow to assess in situ the influence of structural parameters of artificial reefs on recruitment, abundance, distribution and/or diversity. A first study at the microscopic scale revealed the influence of substrate structure on both the abundance of biofilm and the photosynthetic activity of these communities.A more precise scientific framework is now available to guide the construction of artificial reefs on the choice of materials and the design of artificial reef structures in order to optimize the effectiveness of artificial reef immersion project
Taoufik, Sanae. "Fiabilité et analyse de défaillance des tags RFID UHF passifs sous contraintes environnementales sévères". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR009/document.
Pełny tekst źródłaNowadays, RFID has strongly developed in many industrial applications, including the aeronautics and automotive sectors, where there is a strong demand for auto-identification systems operating in severe environments. In this context, the objective of this thesis is to study the effects of thermal storage on the reliability of passive UHF RFID tags. To achieve this, we adopted a consistent methodology. The first step of this methodology was to choose the tag under test. Two types of tags Web and Tageos from two different manufacturers are aged under high temperatures. The second step was to define the parameters of the aging tests and to characterize the aged tags. Using a dedicated measurement bench, the reflected power is measured after each aging phase for all tested tags to determine the power loss caused by the high temperature storage. Reflected power decrease significantly after each aging phase with different dynamics of degradation for all aged tags. This dynamics of degradation depends on the temperature test and the type of tag. The final step involved statistical and physical failure analysis. Clear differences about modes, mechanisms and failure times between Web and Tageos tags have been observed, it seems that Tageos tags are more reliable than Web tags. Failure analysis of the samples, using an optical microscope and SEM, has revealed, cracks in the antenna metallic conductors on a part of the aged tags. In another part of the tags, no failures in the antenna have been seen, but clear deformations at the polymer matrix of the ACP have been observed, thus changing the impedance matching between the RFIC and the antenna. Simulations using the COMSOL multiphysics software have been implemented in order to reproduce the experimental failure mechanisms. This thesis work has demonstrated the importance of studying the effects of high temperature storage on the reliability of passive RFID tags. Failures appeared faster and tests cost considerably less than other types of accelerated aging tests
Azéma, Aurélia. "Les techniques de soudage de la grande statuaire antique en bronze : étude des paramètres thermiques et chimiques contrôlant le soudage par fusion au bronze liquide". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00918829.
Pełny tekst źródłaNarynbek, Ulu Kubat. "Fatigue of HNBR - Effects of formulation and thermal aging". Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0006/document.
Pełny tekst źródłaThe present PhD thesis is devoted to investigation of fatigue in elastomers, andmore particularly of carbon black-filled hydrogenated nitrile butadiene rubber (HNBR).HNBR is a high performance elastomer classically used for high temperature industrial applications, where high resistance to industrial solvents is also required.The thesis is divided into three main parts.First, major improvements of testing procedures utilized in fatigue life testing ofelastomers are proposed. An original method to prescribe the true stress throughout fatigue experiments is developed; it permits to plot the first “true” Wöhler curve, i.e. true stress vs.number of cycles, for elastomers. Then,statistical tools, widely applied in medical research, are adopted for a comprehensive probabilistic analysis of fatigue life results that exhibit high scatter and censored lifetimes.Second, these novel tools are used to investigate the effect of chemical formulation -acrylonitrile content, percent hydrogenation,and of a composite blend - on fatigue resistance of HNBR at the service temperature of 120 oC. In addition to these fatigue life tests,fatigue crack propagation experiments and microscopic fatigue damage analysis are carried out. Third, the influence of thermal aging on fatigue performances of HNBR is investigated.To this end, two additional fatigue life tests are carried out: simultaneous aging and fatigue experiments, and fatigue experiments on preaged samples.Additionally, strain-induced crystallization in HNBR is studied; for the first time, quantitative relationships between crystallization, strain,and stress are established for unfilled HNBR blends
Ganzarolli, Giovanna. "La ceramica comune dall’alto al basso medioevo in Veneto (Italia) : tipologie, commerci e analisi sui residui organici". Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0363/document.
Pełny tekst źródłaThe aim of this research is the study of cooking wares, founded in 4 archaeological sites of Veneto region (North-eastern Italy): the archaeological excavation near the Padua cathedral, the archaeological excavation of Rocca di Monselice Castle (PD); the archeological sites of Montagnone of Montegrotto Terme castle; and the excavation in the ex-cinema Astra in Chioggia (VE). Therefore the object of this research is to observe over long time (from 4th to 14/15th century) the cooking wares of a small territory of Veneto region, the central-eastern part, to understand the evolutional change of morphologies, the origins of raw materials and the pottery function.The pottery was studied with the exploitation of different techniques and methodologies: the archaeological and typological approach; the petrographical analysis and the organic residue analysis. This method allowed the observation of:$\begin{itemize}\item the pottery morphological evolution, over long time in a small territory, taking into account also the published ceramic datas of Veneto and the nearest regions;\item the petrographical characteristic and the different use of ceramic paste over a log term for the cooking wares;\item for the archaeological site of Padua cathedral, the functional aspect of pottery. This aspect permits to speculate on the diet habits;\item the link between the cooking and coarse wares and the historical and economical aspects of Veneto. \end{itemize}$Finally this research gives a database to better understand the production characteristics of Paduan cooking wares
Maitte, Baptiste. "Influence de l'activité bactérienne ferro-oxydante et ferriréductrice sur les propriétés minéralogiques et micromécaniques du minerai de fer dans le contexte des mines abandonnées de Lorraine". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0256/document.
Pełny tekst źródłaMine collapses occurred in Lorraine (France) because of the failure of safety pillars made of iron ore. Their failure is not only due to the mechanic stresses applied by the overburden, but also due to the various mineralogical transformations in iron ore which decrease material cohesion and resistance and thus stability of pillars. This is called mineralogical alteration/ageing of iron ore. Chemical mechanisms inducing these mineralogical transformations are now well known but the influence of microbial activity is not well understood yet. Preliminary works have raised the possible role of microbial activity, then the focus of this work was to identify the various bacterial metabolisms capable of reacting with iron ore and to characterize the physico-chemical, mineralogical and mechanical effects. The bacterial metabolism groups possibly implied in these reactions (iron-reducing (IRB), iron-oxidizing and sulfate-reducing bacteria (SRB)) were identified from the mine water. As pure strain or as consortium, these bacteria were incubated with iron ore. Under laboratory conditions, only iron-reducing, sulfate-reducing and acidophilic iron-oxidizing bacteria impacted iron ore samples by modifying the Fe(II)/Fe(III) ratio. A ferrous-carbonate phase and pyrite were formed during incubations with IRB and SRB, respectively. These minerals were characterized from analysis of the solid phase (Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Mössbauer spectroscopy and X-ray diffraction). The impact nitrate-reducing bacteria was also tested but the Fe(II)/Fe(III) ratio of iron ore was not modified significantly. Finally, mechanical properties of iron ore were measured after microbial and purely chemical redox reactions. Discernible modifications of these mechanical properties were observed. From these results, the alteration of iron ore mechanical properties by bacterial activities is a realistic assumption
Micoud, Pierre. "Etude par RPE de l'influence du talc sur le vieillissement UV du polypropylène industriel". Toulouse 3, 2005. http://www.theses.fr/2005TOU30267.
Pełny tekst źródłaThe influence of talc on the industrial polypropylene UV ageing has been studied by Electron Spin Resonance (ESR), at different irradiation and observation temperatures. The bibliographic synthesis on the structures-properties correlations in these materials and on the studies of the polypropylene photo-oxidation by ESR gives an insight on the different organization levels and on the nature of main oxidation radicals. The experimental work is focused on the composites oxidation behaviour evolution with irradiation time and post irradiation duration. Results obtained are showing that the nature of the talc and the reinforcement ratio have an influence on the oxidation of the PP-talc composites, notably on the radicals proportion trapped inside composites. Modifications of oxidation and recombination reactions obtained by the devolatilisation of compounds have been interpreted by an oxygen diffusion restriction probably due to a bigger macromolecules compaction. Moreover, the evolutions with time of radicals after the irradiation stop have shown that the atmospheric oxygen plays a key role on the composite oxidation during the darkness periods. Finally, the study of ESR spectra at different temperatures has been used to modify the kinetic of oxidation-recombination reactions and demonstrate that oxidation ratio became equivalent around the polypropylene glass transition temperature
Boisot, Guillaume. "Mécanismes et modélisation mécanique de la déformation, de l'endommagement et de la rupture du PolyAmide 11 pur et renforcé choc". Phd thesis, École Nationale Supérieure des Mines de Paris, 2009. http://tel.archives-ouvertes.fr/tel-00422223.
Pełny tekst źródłaCette thèse montre qu'une nouvelle fois le modèle de Gurson-Tvergaard-Needleman, modèle initialement développé pour l'étude de la rupture ductile des matériaux métalliques, s'applique dans le cas d'un matériau polymère semicristallin. Le modèle s'avère pertinent pour décrire le comportement endommageable du matériau. Tout comme dans le PVDF, deux critères d'amorçage apparaissent : un critère en coalescence de cavités et un critère d'élongation des fibrilles. Les polymères se déformant rarement dans des conditions d'isothermie, l'auto-échauffement du matériau a été pris en compte en rendant les paramètres intervenant dans le modèle dépendant de la température ; les résultats s'avèrent intéressants et concordent bien avec ceux obtenus expérimentalement. La thèse met également en lumière la préservation de la ductilité par l'ajout d'une seconde phase de caoutchouc en dépit du vieillissement hydrolitique, dans une zone de température inférieure à la zone de température de transition vitreuse. Cependant nous montrons que, selon les caractéristiques de cette seconde phase, les mécanismes d'endommagement peuvent varier et ainsi le critère d'amorçage changer.
Evin, Harold. "Low Cr alloys with an improved high temperature corrosion resistance". Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOS082/document.
Pełny tekst źródłaThe improvement of high temperature oxidation resistance of low chromium content steels, such as T/P91, is of great interest in regards with their application in thermal power generating plants. Indeed, they possess good creep properties, and low thermal expansion coefficient. Important needs in energy together with environmental issues place power generation plants under constraints which lead to develop high efficiency systems. A usual way to increase the efficiency consists in increasing temperature and pressure parameters of the power generating plant. Studies has shown that the total efficiency of a plant increases by nearly 8 % when changing the steam parameters from 538°C/18.5 MPa to 650°C/30 MPa. Then, the problem of corrosion resistance of 9% chromium steel in those conditions is asked. In this work, the behavior of a ferritic / martensitic 9% chromium steel has been studied at 650°C in dry air and in water vapor containing environment in both isothermal and thermal cyclic conditions. The weight gain of samples provides information on the kinetics of the oxidation reaction and the adhesion of formed oxide scale. Corrosion products were characterized by several analytical techniques in order to identify oxides with accuracy and to understand their formation mechanisms. Mixed iron and chromium oxides (Cr, Fe) 2O3 are initially formed and provide temporary protection to the substrate. For long time exposure or temperatures above 650°C, magnetite, Fe3O4 and hematite Fe2O3 are the main oxides formed, highlighting the fact that low chromium steel are inappropriate for applications in such drastic conditions. In order to increase the high temperature corrosion resistance of this alloy, various solutions have been proposed as aluminizing by pack cementation, reactive element oxides coatings of by MOCVD, or addition of alloying elements in the steel composition. These solutions were then tested at 650 ° C in dry air and in water vapor environments