Teses / dissertações sobre o tema "Matériaux – Propriétés mécaniques – Microscopie"
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Odoni, Ludovic. "Propriétés mécaniques et effets d'échelle". Ecully, Ecole centrale de Lyon, 1999. http://bibli.ec-lyon.fr/exl-doc/TH_T1884_lodoni.pdf.
Texto completo da fonteThis dissertation tries to conjugate the comprehension and measurement work to decrypt mechanical properties of solids at micrometric and nanometric scales. The underlying questions are both to locate the limits of bulk properties (frontier of continuous medium mechanic) when the analysis window is narrowed and furthermore to describe new properties related to the decrease in measurement scale, if any. The non-linear mechanical analysis of Intermittent Contact Mode in AFM enables the monitoring of local mechanical properties of polymer such as storage and loss modulus or adherence. The surprising result of this analysis concerns the loss modulus whose measured value is greater than the macroscopic bulk one by one order of magnitude. The nanoindentation tests operated at a constant strain rate confirm and enrich this result : a 'characteristic heterogeneity length' has been introduced to define for this material the dimension under which the mechanical response differs from the one of homogeneous matter. This concept is canonical for heterogeneous materials at micrometer scale (i. E. Polymer blends) and is extended to material which are homogeneous in composition. Beyond this characteristic length, materials can only be described through statistical means. Another development of this study concerns the macroscopic description of materials using bulk constitutive equations. A particular effort has been held to describe viscoplastic behavior of glassy polymers (PMMA and PS). The viscoplastic data obtained by nanoindentation experiments and scratch tests may be interpreted with the help of Eyring molecular theory of activation energy. The results obtained at small strain rate (<0. 1 Hz) enables the computation of an activation volume of the polymeric material (lnm3 for PMMA et 0. 4nm3 for PS). These activation volumes are in good agreement with the theoretical ones and those obtained by macroscopic analytical methods. The scratch test experimental data are showing that at high strain rate (>0. 1Hz) the viscoelastic loss in contact increases and the calculated activation volume decreases. The phenomenon is interpreted as a transition to a B type relaxation of the polymeric material. The origin of the characteristic homogeneity length is still to be enlighten. Should this be understood as an evolution of the mechanical properties due to the narrowing of the analysis window? Is this length related to intrinsic properties of surface? In this case, surface mechanical properties would thus be heterogeneous
Nounah, Hassan. "Modélisation et caractérisation des matériaux à gradient de propriétés mécaniques par des méthodes microacoustiques". Montpellier 2, 1995. http://www.theses.fr/1995MON20117.
Texto completo da fonteSong, Xinling. "Experimental characterization, modelling and simulation at the microscale of the mechanical behavior of fibre bundles". Electronic Thesis or Diss., Orléans, 2024. http://www.theses.fr/2024ORLE1014.
Texto completo da fonteThe mechanical behaviour of a fibrous reinforcement is fundamental during its shaping for the manufacturing of composite materials. To predict this behaviour, mechanical tests alone are not sufficient. It is therefore necessary to obtain a true behaviour law of the reinforcement based on the parameters of the fibrous structure.The objective of this thesis is to study the mechanical behaviour of an assembly of quasi-parallel fibers. To achieve this objective, it is essential to understand and quantify the influence of the fibrous architecture's parameters on its mechanical behaviour. A mixed experimental/numerical approach is proposed. The numerical strategy involves conducting finite element simulations using explicit dynamics, where each fiber is modelled as a B31 beam, in contact with the others. Experimentally, using assemblies of a few dozen model fibers of 500 microns, compaction/compression tests are conducted under tomography. These tests allow for the observation of the evolution of the fibrous architecture depending on the imposed load and the applied boundary conditions. Microstructure evolution indicators are then defined to analyse and process the results. A reconstruction algorithm enables the creation of a representative numerical model of the tested assembly, where each fiber is modelled by a B31 beam. The identification of the fiber's behaviour law then allows for the simulation of the tested structure. Comparisons across several types of samples validate the numerical approach, thus enabling the development of a virtual estimator that can simulate the behaviour of non-existent assemblies. Subsequently, a strategy for creating virtual fibrous architectures is developed for parametric studies. This strategy allows for the rapid creation of various architectures with controlled parameters. With all the preceding steps, a parametric study can be conducted, establishing the influence of certain parameters : initial microstructure parameters, fiber diameter, fiber/fiber friction factor, and loading path. This final step demonstrates the effectiveness of the proposed approach and also opens up numerous future perspectives
Chovelon, Eurydice. "Etude de l'influence de la microstructure, caractérisée par microscopie électronique en transmission et nano-usinage ionique "FIB", sur les propriétés mécaniques d'aciers bainitiques". Aix-Marseille 3, 2003. http://www.theses.fr/2003AIX30058.
Texto completo da fonteSince few years, new families of steels like dual-phase steels (ferrite/martensite), with interesting mechanical properties have been developed for automobile industry. Nevertheless, some applications need higher mechanical properties, upper than 800 MPa. This is why we have developed, in collaboration (TECSEN – Arcelor), new steels with multiphase microstructure microalloyed with vanadium. In order to do that, it was essential to understand the influence of both the chemistry and the thermomechanical processes on microstructure and precipitation, which determinate the mechanical properties of steels. Four bainitic steels and two simulation products have been made to understand the contribution of each constituant on mechanical properties. The principal tool employed for this work was the transmission electron microscope coupled with an EDX analyzer and an electron energy loss filter. Classical techniques of sample preparation was used and for the first time, focused ion beam FIB was also used to prepare samples. It was found that this tool has played major role to identify all the phases present in the steel. We have showed that the microstructure of these steels consists of inferior bainite containing martensite in variable amounts (4 to10 %). In all the studied steels, the bainite contains ferrite grains and globular cementite. However, the amount of vanadium carbides and intra granular cementite depends on the thermomechanical process applied. The precipitation of small intra granular cementite is present only for particular cooling speed and entry in bainitic region. In this kind of multiphase and microalloyed steels, more than the contribution of the microstructure, the vanadium carbide allowed to reach mechanical properties of about 900 MPa. To reach 1000 MPa, the fine intragranular cementite (1 to 3 nm) is absolutly necessary
Martinez, Rémi. "Modélisation multi-échelles des propriétés mécaniques d'un alliage d'aluminium de fonderie". Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST1148.
Texto completo da fonteThis work highlights the results of a theoretical Al$_2$Cu particles coarsening model in a T7 thermal treated 319 aluminum alloy. As an input of the model, the experimental and discretised size distribution of the precipitates, in a 1$mu$m$^3$ representative volume element of the alloy, is used and coupled to a flux equation. The use of a numerical implicit scheme allows us to solve the problem by the inversion of a tridiagonal matrix. Thus, the evolution of the critical radius of coarsening, of the total number and of the volumical fraction of particles are modeled in a range of temperature going from 23°C to 300°C up to 1000h ageing time. Results were then compared to transmission electron microscope observations and are in good agreement with experimental measurements. Hence, the model was then coupled to a micro-mechanical model which is based on the theory of dislocations. It determines the real yield stress of the alloy generated by the interaction of the dislocations with the lattice (Peierls stress), with the precipitates (Orowan stress) and with the atoms in solid solution. Both models were then combined into a mechanical macro-scale model in order to represent the LCF behavior of the material. An elasto-viscoplastic law has been used and all the internal variables were experimentally determined using LCF stress/strain loops for the mechanical steady state. The simulation results are in good agreement with the experiments. Finally, 1D and 3D finite element computations could be run, taking into account the evolution of the microstructure during ageing and its impact on the evolution of the mechanical properties, to determine the head cylinder behavior under thermomechanical fatigue
Delmas, François. "Influence des traitements thermiques sur les propriétés mécaniques d'un alliage AIMgSiCu". Toulouse 3, 2002. http://www.theses.fr/2002TOU30141.
Texto completo da fonteTravaillot, Thomas. "Caractérisation mécanique des matériaux élastiques à l'échelle locale par microscopie à pointe vibrante : Approche multimodale et mesure de champs". Thesis, Besançon, 2014. http://www.theses.fr/2014BESA2011/document.
Texto completo da fonteThis work proposes an improvement of the Scanning Microdeformation Microscope (SMM), a scanningprobe microscope, for the mechanical elastic characterization of materials at local scale. It demonstratesthat using n > 2 SMM resonance frequencies allows to decouple Young’s modulus andPoisson’s ratio values for an isotropic material.The mechanical description of the resonator has been enriched in order to allow for an accuratemodeling over a wide frequency range. Procedures have been developed to identify the modellingparameters and the elastic constants of the materials from n > 2 resonant frequencies. Finally, theseprocedures have been applied to the characterization of various materials at local scale in order tovalidate the method and to present possibilities and limits.To improve robustness and move towards the characterization of anisotropic materials, a polarizedlightimaging interferometer was developed to measure the rotation field of reflecting surfaces in aparticular direction. The sensitivity to the rotation originates from a homemade birefringent prism withuniaxial gradient of refractive index. This system is able to measure a localized rotation field as it isinduced in the vicinity of the tip of the SMM. Its interest is also demonstrated in cases in which scaleeffects make the rotation measurement preferable to the out-of-plane displacement measurement
Keller, Clément. "Etude expérimentale des transitions volume/surface des propriétés mécaniques du nickel polycristallin de haute pureté". Phd thesis, Université de Caen, 2009. http://tel.archives-ouvertes.fr/tel-00403216.
Texto completo da fonteWahyudi, Herman. "Étude des propriétés mécaniques des matériaux argileux en relation avec leur organisation à différentes échelles". Châtenay-Malabry, Ecole centrale de Paris, 1991. http://www.theses.fr/1991ECAP0205.
Texto completo da fonteMegevand, Benjamin. "Contribution of atomic force microscopy to local mechanical characterization of polymer materials". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI023/document.
Texto completo da fonteThis thesis work aims to show how nanomechanical characterizations in AFM can provide a better understanding of structure-properties relationships in polymers. In this context, the technique itself and the associated theoretical basis are first analyzed to implement a robust methodology in order to perform reproducible, quantitative measurements. Two main studies are carried out around a common topic: the understanding of the interactions between biopolymers and ionic liquids (ILs). First, the compatibilization of PBAT/PLA blends by two different ILs (namely il-Cl and il-TMP) is studied. Adhesion and local modulus mappings evidence the resulting microstructures, and highlight that the compatibilization mainly results from a modification of the PBAT/PLA interface, becoming a coherent interphase. This is due to specific interaction with the cations and the anions of each IL, which are preferentially located at those interphases. The second study is more specifically about the understanding of the modification of semicrystalline PBAT by the addition of small amounts of the same ionic liquids. While il-TMP forms dissipative nodules dispersed into the matrix with a cohesive interphase between both, il-Cl, miscible into the amorphous phase of PBAT, amplifies the chain mobility in the bulky MAF (i.e. Mobile Amorphous Fraction) and hinders it in the confined RAF (i.e. Rigid Amorphous Fraction), leading to interesting macroscopical properties modifications. More than showing some interesting capabilities of ILs as additives in polymers, those results also show an outstanding potential of AFM nanomechanical mappings for the in-deep understanding of structure-properties relationships in materials
Youssef, namnoum Carol. "Etude de l'influence des additions minérales sur l'auto-cicatrisation des matériaux cimentaires : caractérisation expérimentale et modélisation des propriétés visco-élastiques". Thesis, Ecole centrale de Nantes, 2021. http://www.theses.fr/2021ECDN0020.
Texto completo da fonteThe mechanical and environmental loads undergone by concrete can lead to cracking threatening the durability of infrastructure. Self-healing, defined as the ability of a structure to repair itself without human intervention, is increasingly emerging as a promising solution to increase the durability of structures. In this work, the focus was primarily on the physico-chemical process of autogenous self-healing for mixtures composed of cement and mineral additions increasingly used with the objective of reducing the carbon footprint of concrete. The healing potential has been evaluated on different compositions to analyze their mechanical behavior by three-point bending tests. In parallel, the chemical nature of the products formed within the artificially created cracks are monitored by various microscopic analysis and imaging techniques (SEM, XRD, TGA). The detailed interpretation of the results allowed clear conclusions to be drawn on the self-healing capacity of the materials and on the mineralogy of the healing products depending on the initial composition. Secondly, the visco-elastic behavior of healed or healing mortars have been investigated. To our knowledge, this is pioneering work in this field whose objective is to provide additional elements on the interaction between the continuity of hydration of the healing material and the presence of mechanical load. The experimental approach consisted both in monitoring the flexural creep of healed materials as well as their residual mechanical behavior after unloading. By combining the two results, we concluded that the evolutionary aspect of the mechanical properties with the continuity of hydration of cement during healing leads to a relationship between mechanical regains and the rate of creep deformation. Then, a microscopic scale modeling has been established to identify and evaluate the physical mechanisms of the creep-healing coupling. In the proposed approach, the evolution of mechanical regains by self-healing of virtual cement pastes has been simulated and confirmed the experimental hypotheses of the influence of mechanical regains on the creep displacement of healed materials
Leblond, Edith. "Nitruration de l'aluminium par voies ioniques". Ecully, Ecole centrale de Lyon, 1998. http://www.theses.fr/1998ECDL0005.
Texto completo da fontePachon-Rodriguez, Edgar-Alejandro. "Étude de l’influence de la dissolution sous contrainte sur les propriétés mécaniques des solides : fluage du plâtre". Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10284/document.
Texto completo da fonteThe huge enhancement of the creep of plasterboard by humid environments is an old problem in the building industry, but its origin remains unknown. To understand this mechanism a three scales study (macro : mechanical behavior, micro : dissolution kinetics, nano : atomic observation) has been done. There is a strong correlation between wet plaster creep and gypsum dissolution kinetics. The concordance between this correlation and the law of deformation by pressure solution, well-known in geology, permits to propose pressure solution as one of the mechanisms responsible of wet plaster creep. The topological evolution of the cleaved surface of a gypsum single crystal during its dissolution in a flowing under-saturated aqueous solution has been observed with an atomic force microscope. The kinetics of step migration strongly depends on the saturation state of the solution, the force applied by the tip on the surface, as well as the used additives. The study of the influence of the force applied by the tip on the step velocity evidence two different dissolution enhancement regimes. At high forces (> 15 nN) a corrosive wear behavior is observed, while at low forces (< 10 nN) pressure solution is the observed mechanism. The step velocity evolution with the force obeys the known kinetic law of pressure solution
Bytebier, Karl. "Etude du comportement mécanique de la paroi cellulaire du bois par Microscopie à Force Atomique". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2009. http://tel.archives-ouvertes.fr/tel-00648700.
Texto completo da fonteSimon, Anne. "Intérêt de la microscopie de force atomique sur la biofonctionnalisation de matériaux : caractérisation du greffage et de l'adhésion cellulaire". Bordeaux 1, 2002. http://www.theses.fr/2002BOR12583.
Texto completo da fonteChermaneanu, Raducu. "Représentation de la variabilité des propriétés mécaniques d’un CMO à l’échelle microscopique : Méthodes de construction des distributions statistiques". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14485/document.
Texto completo da fonteNowadays, composite materials are very widely used, notably in the domain of aeronautical structures, thanks to their numerous functional benefits. Their specific mechanical properties (properties/density) far superior to those of conventional materials, such as steel or aluminum and the realization of complex shapes, make these materials perfect candidates in many areas beyond aviation. However, these materials present at different observation scales sources of variability peculiar to each one. The manufacturing process and the properties of the elementary constituents are in fact the principal cause of these sources of variability. Three levels (or scales) of observation are usually considered regarding composite materials: the microscopic scale (fibers and matrix), the mesoscopic scale (ply) and finally the macroscopic scale (laminate material). The sources of variability propagate trough the scales and finally generate dispersed mechanical behaviors at the structure scale. Taking into consideration these sources is proved to be a relevant work by the designer, which in turn will allow him to calculate an indicator of the composite structure reliability that he is conceiving. To be able to do the latter work, it is necessary to transfer this variability at a lower computational cost from the microscopic level up to the structure scale. The construction of equivalent mechanical properties distributions according to the variability present at each scale is then essential. The objective of this research work was to build statistical distributions of the homogenized behavior of the material at the scale of fibers and matrix, according to the existing variability at this scale. Minimizing the computation time required for obtaining these distributions was another important objective. From a microscopic observation made on a section of a CMO, the morphological variability of the heterogeneous medium has been characterized and six different types of arrangements patterns of fibers grouped into cells have then been identified. Physically reasonable virtual cells have been developed and suggested, in order to build the equivalent behavior distribution by cell type, according to the relevant variables selected at this scale. Now, in order to minimize the computing time required for the creation of these distributions, an approach based on neural networks was proposed. This approach was used for a type 6 cell and for a number of 1000 FE calculations, in order to evaluate the quality of the approximation as well as the reduction of computation time. Hence, the reduction of the computation time was significant, at an approximate rate of 95 %
Scida, Daniel. "Étude et modélisation du comportement mécanique de matériaux composites à renforts tisses hybrides et non hybrides". Compiègne, 1998. http://www.theses.fr/1998COMP1168.
Texto completo da fonteJean, Aurélie. "Etude d'un élastomère chargé, de sa nanostucture à son macro-comportement". Paris, ENMP, 2009. http://pastel.paristech.org/5215/01/Thèse_A-Jean.pdf.
Texto completo da fonteIn mechanics of materials, a current issue is to better understand macroscopic phenomena by the study of microstructure. This approach is possible thanks to several developments of homogenization techniques in multiscale mechanics. In this PhD-Thesis, rubber with carbon black fillers is considered. Several mechanical properties of this material are strongly linked to the scattering of carbon black particles and aggregates in the elastomeric matrix at macroscopic scale. Two main objectives are pursued in this thesis. The first one consists in modeling the 3D microstructure of material. For that purpose, we establish a mathematical random morphological model of different scales of the microstructure. A dedicated parameter identification of this model on transmission microscopy images is presented. The originality of this method resides in the optimization process that we develop where a comparison of statistical moments between computed numerical transmission microscopy images and experimental data is carried out. We are able to compute microstructure morphologies very close to real ones. The second objective consists in determining the effective material properties, namely the elastic moduli and the electrical conductivity, of this material. Finite element simulations and the notion of Representative Volume Element (RVE) are used. The latter can be obtained by Monte Carlo evaluation of apparent properties on randomly generated microstructures of growing size. Several tools like finite element meshing and parallel computations applied to heterogeneous materials with high contrast were investigated for that purpose
Declairieux, Charles. "Etude microstructurale et thermomécanique d'alliages à mémoire de forme de type HfPdX et TiAuX à hautes températures de transformation". Paris 6, 2011. http://www.theses.fr/2011PA066266.
Texto completo da fontePlanes, Nicolas. "Propriétés physiques de 3C-SiC sur substrats SOI : perspectives d'application". Montpellier 2, 1999. http://www.theses.fr/1999MON20156.
Texto completo da fonteDubois, Jean-Baptiste. "Conducteurs nanocomposites métalliques élaborés par déformation plastique sévère : formation et stabilité thermo-mécanique des nanostructures, propriétés induites". Poitiers, 2010. http://theses.univ-poitiers.fr/26782/2010-Dubois-Jean-Baptiste-These.pdf.
Texto completo da fonteThis thesis concerns the study of metallic nanocomposite copper/niobium (Cu/Nb) wires, combining high electrical conductivity and high strength, as required for the design of high magnetic field resistive coils. The reinforced continuous nanocomposite Cu/Nb conductors are fabricated via a severe plastic deformation process (SPD), which consists in repeated extrusion, drawing and bundling cycles (Accumulative Drawing and Bundling : ADB) and leads to the nanostructuration of the Nb reinforcements and a multi-scale Cu matrix. In order to optimize the process, the effect of heat treatments on texture and its development during the process were analysed by means of laboratory X-ray diffraction. Complementary in-situ heat treatments under synchrotron radiation gave a better insight into the elementary annealing mechanisms and enabled defining optimized heat treatments. These experiments also revealed that the thermal stability of Cu/Nb conductors is extremely dependent of the microstructure size: recovery, recrystallization, grain growth and all relaxation processes are frustrated in the case of nanocomposites. From these results, optimized “co-axial” conductors reinforced by Nb nanofilaments and nanotubes were processed. Their microstructure and physical properties have been characterized and compared to those of previous Cu/Nb nanocomposite conductors. With the possibility to produce long wires with improved properties, these new Cu/Nb nanocomposites offer a great alternative to existing conductors for future high magnetic field applications
Paredes, Guerrero Germercy. "Development of new probes based on carbon nanocones for near-field microscopies". Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30206.
Texto completo da fonteNear-field microscopy allows studying the topography and the physical properties (electrical, mechanical, etc.) of a material surface at nanoscale. For such a purpose, the sample surface is scanned by a probe (or tip) which geometric characteristics (such as the apex radius and the aspect ratio) and the physical properties (mechanical, electrical, etc.) must be suitable to ensure a sufficient resolution and a reliable representation of the surface. However, the current probes have significant limitations regarding the resolution, the possible imaging artifacts, as well as their ability to be used in different modes (conductive and non-conductive). These limitations are caused mainly by the type of material used (for example silicon or silicon nitride, for standard probes, or carbon nanotubes), as well as by the manufacturing processes used to structure the geometry of the probes. In this work, we study the potential of carbon nanocones (graphenic carbonaceous morphology with conical shape with high aspect ratio and nanosized apex) for different modes of near-field microscopy. These nanocones exhibit excellent mechanical (strong C-C bond) and electrical properties. They have already been successfully tested and patented as electron emitters for the cold-field-emission guns which equip the most performing transmission electron microscopes. These various characteristics of the nanocones (aspect ratio, nanosized apex, conductivity, mechanical stability, strong atomic cohesion) and others (hydrophobicity, chemical inertia, multiscale micro-nano morphology...), make that they could also constitute a promising solution for designing probes potentially superior to existing probes, either standard or more specific such as those in carbon nanotubes, for various types of near-field microscopy, in particular in terms of spatial resolution and durability. In the first part, this thesis is dedicated to the synthesis of individual carbon nanocones using an original synthesis method called ToF-CVD (Time of Flight Chemical Vapor Deposition). The work reveals complex formation mechanisms involving the heterogeneous phase nucleation mechanisms specific of the CVD deposition of pyrolytic carbon on the one hand, and well-known wetting mechanisms such the Plateau-Rayleigh instability on the other hand. The mounting of the nanocones on dedicated supports as probes for near-field microscopies is then carried out, followed by characterization studies (SEM, TEM, RAMAN spectroscopy) to assess their starting characteristics from the geometry and structure point of view, and their evolution under the operating conditions required for both the probe fabrication and for the different near-field microscopy modes studied. In a second part, the potentiality of carbon nanocones as probes for non-conductive modes such as topographic mode (atomic force microscopy - AFM) and "Peak Force Quantitative Nano Mechanical" (PF-QNM) mode, as well as for conductive modes such as scanning tunneling microscopy (STM), conductive atomic force microscopy (c-AFM), and Kelvin force microscopy (KFM) is evaluated. This evaluation is made on the basis of (i) performances; (ii) durability; (iii) versatility. The final goal is to compare the performance of the carbon nanocone probes with other commercial probes. Carbon nanocones reveal to truly be multimode probes with few existing counterparts nowadays. Improvements are needed and possible, for which directions are proposed
Biaye, Moussa. "Caractérisation de propriétés électroniques et électromécaniques de nanocristaux colloïdaux par microscopie à force atomique en ultravide". Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10231/document.
Texto completo da fonteUnderstanding the electronic, electrical and mechanical properties of nanostructures is a key issue in nanoscience and nanotechnology. Scanning probe microscopy is an essential tool to probe and understand these properties at the nanoscale. The objective of this thesis was to characterize the electromechanical and electrostatic properties of individual or assembled colloidal nanocrystals using atomic force microscopy in ultra-high vacuum environment.The first part of the manuscript deals with the transport properties of assemblies of gold and indium tin oxide nanoparticles, forming the active areas of resistive strain gauges. Current-bias spectroscopies are measured as a function of the force applied on the cantilever and as a function of temperature. Tunneling transport is evidenced and measured from the linear regime to the Fowler Nordheim regime. The mechanical characteristic (effective Young modulus) of ligands is extracted.The second part of the thesis is devoted to the characterization of the electrostatic properties of individual indium arsenide (InAs) colloidal doped nanocrystals with sizes in the 2-8 nm range, using non-contact atomic force microscopy coupled to Kelvin probe force microscopy. This aim was to understand the charge transfer mechanisms between doped or undoped nanocrystals and their environment, in a physical regime of strong quantum and Coulomb confinement. Experimental results enable to measure a doping level of and a defect density of about . Kelvin probe force microscopy measurements were in addition performed on colloidal perovskite (CsPbBr3) semiconductor nanocrystals in order to explore the photo-generation mechanisms of carriers
Heinze, Karsta. "From grain to granule : the biomechanics of wheat grain fractionation with a focus on the role of starch granules". Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS072/document.
Texto completo da fonteThe wheat grain is a natural composite material of worldwide importance. The major part of the grain is the starchy endosperm. To obtain food products, such as flour, the endosperm’s compact structure needs to be disintegrated, which is achieved by milling the grains under high forces. The quantity and quality of the milling products notably depend on the fragmentation behaviour of the endosperm.Due to the endosperm’s composite nature, this behaviour depends strongly on the mechanical properties of its components and their interaction. The main components of the endosperm are carbohydrates and proteins. The carbohydrates are deposited as starch in the form of granules of micro-meter size, whereas proteins form a network (gluten), which surrounds the starch granules. The interactions between starch and proteins is believed to be influenced by certain non-gluten proteins (puroindolines), whose presence and allelic state are genetically controlled. If puroindoline genes are present in the wild-type form, grain hardness is low, which have been related to low starch-protein adhesion. The complete absence of puroindolines in the durum wheat species leads to very high grain hardness and indicates a strong adhesion.The aim of this thesis was to investigate the biomechanics of wheat grain fractionation with a focus on the role of the starch granules therein, which was pursued with a multi-disciplinary approach. Different size scales were considered, from the micro meter-sized structures of starch and protein, the complexity of their arrangement in the endosperm, up to the millimeter-sized grains. In this work, grain-scale milling experiments were combined with nano-mechanical measurements by atomic force microscopy (AFM) and numerical simulations.The milling behaviour of a transgenic durum wheat line, which contained puroindoline genes, was determined by grain scale milling experiments and compared to the milling behavior of non-modified durum wheat. A significant change of milling behavior of the transformed durum wheat grains was observed in terms of milling energy, flour yield and starch damage, which was solely attributable to the presence of puroindolines. The observed changes were consistent with the hypothesis of a lower adhesion between starch granules and protein matrix due to the presence of puroindolines and confirmed the significant effect of puroindolines on the fragmentation behaviour, independent of the grain’s genetic background.The change of fragmentation behaviour is a result of modifications of the mechanical properties of the endosperm’s components and/ or their interaction. Such modifications can be investigated by AFM nano-mechanical measurements. Based on previous work illuminating the global nano-mechanical properties of starch and gluten, contact-resonance AFM (CR-AFM) was applied to obtain maps of the nano-mechanical properties inside the grains. Due to the high topography variations of grain section surfaces and the non-trivial correlation between surface slope and contact resonance-frequency, which hindered a straight-forward interpretation of CR-AFM measurements, a practical method based on existing analytical models of the cantilever vibration was developed to correct the measurements. CR-AFM studies of the endosperm were then focused specifically on the mechanical properties of starch granules and the link to starch structure, and applied to the study of starches from wheat in comparison to plants from different botanical origin (other cereals and legumes).Finally, the role of starch granules, their size distribution, and mechanical properties on endosperm fragmentation was analysed by parametric numerical studies. The influence of the bi-modal size distribution of granules on the mesoscale mechanical properties was shown, as well as the governing role of granule toughness and interface adhesion on the granule damage
Huvier, Corine. "Consolidation de poudres métalliques par compression isostatique et chocs laser : microstructures et propriétés d'agglomérés obtenus avec des poudres de cuivre allié". Poitiers, 1994. http://www.theses.fr/1994POIT2266.
Texto completo da fonteMasquelier, Nicolas. "Caractérisation et modélisation de transformations microstructurales pour la mise au point d'une nouvelle génération d'alliages d'aluminium pour conducteurs électriques". Rouen, 2012. http://www.theses.fr/2012ROUES011.
Texto completo da fonteNew aluminium alloy had been developed for electrical cable application. This alloy has good mechanical properties at high temperature, and also good electrical properties. Its microstructure had been characterized at atomic scale with the goal to link microstructure and physical properties. Thanks to this correlation, microstructure was adjusted to optimize the physical properties of this alloy. Microstructure of the alloy was also modelized to predict the evolution of physical properties with time. Finally, linking characterization and modelling, thermodynamical datas had been determined. These datas was unknown for this particular alloy and could be useful for the future
Somera, Audrey. "On the effective elasticity of quasi-periodic lattice materials : From microscopic foundations to experimental validation". Electronic Thesis or Diss., Ecole centrale de Nantes, 2022. http://www.theses.fr/2022ECDN0037.
Texto completo da fonteArchitectured materials have received increasing interest over the years, especially by allowing new areas of the Ashby diagrams to bereached. Quasi-periodic lattices combine the advantages of both random and periodic structures: they are deterministic structures, their behaviour is isotropic, and they have better toughness than periodic lattices. However, the study of the mechanical behaviour of such structures is still in its infancy. Thus, this thesis proposes to study the effective elastic behaviour of quasi-periodic lattices. First, the local deformation mechanisms of different patterns have been studied. It is shown that the patterns could be separated into three categories: the completely stretching and bendingdominated patterns and the variable dominance ones. The influence of these local mechanisms on the overall mechanical behaviour was then investigated. For this purpose, an identification procedure of the lattice equivalent effective behaviour, based on a FEMU-type method, was implemented. First performed using a numerical twin, an experimental set-up was then designed to carry out the procedure and validate the numerical results experimentally. It is shown that the most suitable behaviour model depends on the pattern considered. While a classical Cauchy-type law seems sufficient to describe the behaviour of completely stretching-dominated and variable dominance patterns, it is necessary to use a Cosserat-type model for completely bending-dominated ones
Dubromez, Vincent. "Amélioration des performances du polycarbonate et des mélanges polycarbonate/polystyrène par des copolymères à blocs ABC". Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10139.
Texto completo da fontePolycarbonate (PC) is a widely used thermoplastic polymer for numerous industrial and biomedical applications, due to its exceptional use properties (transparency, mechanical and thermal behavior). Nevertheless, the PC exhibits two major defects: high viscosity and poor notch impact properties. The goal of the present study was to propose a solution for these two issues, while preserving the PC transparency. Three ways were investigated: (i) the decrease of viscosity via adding polystyrene (PS), (ii) the improvement of notch impact behavior by adding poly(styrene-b-butadiene-bmethylmethacrylate) block copolymers (SBM) and (iii) simultaneous use of PS and SBM. Adding PS to a PC matrix does decrease its viscosity, while preserving the transparency. However, the mechanical properties of PC/PS blends are inferior to those of the neat PC. The experimental study on binary PC/SBM blends point out the great influence of the nature and proportion of the copolymer in the blend, as well as of the matrix viscosity, on the final properties of the blends. The investigation of the ternary PC/PS/SBM blends demonstrate that it is possible to obtain an improvement of the notch impact properties, while preserving the PC transparency – by generating a homogeneous and well dispersed blend morphology. This requires an optimal combination between the matrix fluidity, the nature and the proportion of block copolymers and PS, and also an appropriate choice of the processing conditions
Kaouache, Belkhiri. "Analyse multiéchelles de la transformation martensitique induite par contrainte dans les alliages à mémoire de forme: corrélation contraintes-microstructure". Phd thesis, Paris, ENSAM, 2006. http://pastel.archives-ouvertes.fr/pastel-00002209.
Texto completo da fonteLe, Clerc Christophe. "Mécanismes microstructuraux impliqués dans la fatigue des fibres thermoplastiques". Phd thesis, École Nationale Supérieure des Mines de Paris, 2006. http://tel.archives-ouvertes.fr/tel-00164759.
Texto completo da fonteapplications dans des domaines de plus en plus variées du textile technique : le renforcement de structure, les
cordages, le géotextile... Les différents usages présentent des conditions mécaniques, thermiques et
environnementales de plus en plus sévères. Au cours de ce travail, nous avons exploré différentes sollicitations
mécaniques en particulier la fatigue et différentes températures dans une gamme de 20°C à 180°C comprenant la température de transition vitreuse.
Cette étude est construite autour d'essais mécaniques sur fibre unitaire d'un diamètre de 18 à 27μm en
traction, fluage et fatigue et des essais de fatigue sur mèche de fibres. La compréhension des mécanismes
microstructuraux est passée par l'utilisation de nombreuses techniques d'observation (MEB, microscopie
optique, coupe microtome), d'analyse de la microstructure (diffraction des rayons X aux grands angles et aux petits angles) et de caractérisation thermomécanique (DSC, DMTA).
Le couplage des essais de fatigue et des observations aux différentes échelles a mis en évidence une
évolution de l'organisation globale avec une meilleure orientation de la structure. Parallèlement, à cette
amélioration paradoxale des propriétés, un endommagement local critique apparaît sous forme d'une fissure de fatigue caractéristique. Les paramètres mécaniques, et en particulier, la contrainte minimale du cycle ont été étudiés en corrélation avec les mécanismes de dissipation d'énergie observés lors de la sollicitation cyclique. Ce travail a aussi été l'occasion de déterminer des paramètres matériaux pertinents justifiant la localisation de la fissuration tels que les inclusions solides et la structure coeur / peau.
La sollicitation cyclique au dessus de la température de transition vitreuse a fait apparaître un nouveau mode de fissuration en fatigue conduisant à un faciès original. Cette morphologie de rupture très particulière
observée sur des monofilaments correspond à la morphologie souvent observée sur des fibres extraites de structures complexes soumises à des sollicitations cycliques.
Nozahic, Vincent. "Vers une nouvelle démarche de conception des bétons de végétaux lignocellulosiques basée sur la compréhension et l'amélioration de l'interface liant / végétal : application à des granulats de chenevotte et de tige de tournesol associés à un liant ponce / chaux". Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00809816.
Texto completo da fonteBalan, Alexandre. "Modélisation isotherme et anisotherme de la limite d'élasticité précipitation-dépendante de l'Inconel 718". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI003/document.
Texto completo da fonteThis thesis manuscript presents the results of work concerning the effects of thermal transients on the precipitation of intermetallic phases in the nickel-based superalloy Inconel 718® and the consequences of this precipitation on the mechanical properties of this alloy. This work focuses on a coupled approach capable of describing the evolution of the precipitation of the γ'' phase and its consequences on the yield strength of the Inconel 718®. The precipitation state is modeled thanks to the implementation of the equations of the classical germination and growth theory, modified to take into account the platelet geometry of the γ'' precipitates. This precipitation model is then validated by experimental data from the literature but also from transmission electron microscope observations and small angle neutron scattering tests. The size distribution of the γ'' phase thus simulated is used as the input data of a model for predicting the precipitation-dependent elasticity limit. These simulated elasticity limits are finally compared with experimental results from tensile tests. A welding model was then made to test the elastic yield prediction model for thermal transients in an industrial case
Villegas, Randolfo. "Genèse de la ferrite aciculaire dans les aciers à moyen carbone microalliés au vanadium. Morphologie fractale en relation avec les propriétés mécaniques". Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL086N/document.
Texto completo da fonteMedium carbon vanadium microalloyed steels have been developed to obtain new microstructures, mainly formed of acicular ferrite (AF). Controlling the chemical composition and (0.1-0.3 % V) and the cooling rates (2.0 °Cs-1) lead to AF fractions up to 80 %. An empirical parameter, the ferritisant power, P, has been introduced to evaluate the combined effect of chemical composition and cooling conditions. Scanning (SEM) and transmission (TEM) electron microscopy investigations indicate that AF develops from proeutectoid ferrite enveloping MnS inclusions. An interphase precipitation of vanadium carbo-nitrides, V(C,N) has been identified. It is suggested that this precipitation is at the origin of carbon depletion in the austenitic matrix surrounding the AF plates. The formation of the AF is then enhanced by an autocatalytic effect. The fractal nature of AF has been determined by SEM and TEM characterisations. Fractal dimensions, D, and cut off lengths have been derived by the counting box method applied to SEM images. Mechanical tests conducted in isothermal and quasistatic conditions reveal that mechanical properties of AF are of the same grade of that of bainitic microstructures. Experimental strain-stress curves are described by the Hollomon law. The work hardening of the studied microstructures increases with the AF fraction. The mechanical properties have been linked to the fractal dimension by the following exponential relation : [delta]M = c exp [[alpha] (D -2)], where M represents the mechanical property (Re, Rm, etc.) and c and [alpha] are constants parameters
Gong, Xiao Lu. "Développement d'une méthodologie expérimentale associée à une approche analytique pour la compréhension du comportement de plaques composites non-trouées et trouées sous chargement simple et combiné de traction-torsion". Compiègne, 1994. http://www.theses.fr/1994COMPD741.
Texto completo da fonteMataveli, Suave Lorena. "High Temperature Durability of DS200+Hf Alloy". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2017. http://www.theses.fr/2017ESMA0032/document.
Texto completo da fonteThe anisotropy in mechanical behavior of the directionally solidified DS200+Hf alloy and the damage mechanisms have been investigated between 650°C and1100°C. Single-crystalline specimens of the same alloy have also been used to get a better understanding of the anisotropy in mechanical properties and durability. Tension, creep, low-cycle fatigue (LCF), dwell-fatigue and crack propagation tests have been performed and analyzed by SEM observations to better understand the damage modes in this alloy. At 650°C, a considerable creep (and LCF) life anisotropy is observed while almost no anisotropy remains at 1100°C in creep. The γ rafting is mainly responsible for this decrease in creep anisotropy and for theincrease in creep rate in dwell-fatigue. An intergranular fracture mode has been observed for ail kind of solicitation along transverse direction, mainly due to the presence of grain boundary particles such as carbides. These carbides are also the main crack initiation sites in LCF at 650°C and at 900°C. At high temperature (900°C), oxidation not only controls the crack initiation mechanisms by inducing surface carbides cracking, but it also affects the crack propagation through a combined localized γ depletion and crack tip blunting, leading ove ra li to a higher crack propagation threshold. Such a behavior is not observed in high vacuum and surface carbides are no more the main crack initiation sites. lt is shown that at low temperature during transverse creep testing (750°C), highly misoriented grain boundaries, having one grain favorably oriented for single slip and lattice rotation, are the most critical ones
Croston, Tania. "Etude expérimentale du comportement d'une poutre en béton armé en flexion trois points réparée par matériaux composites (approche probabiliste)". Phd thesis, Paris, ENSAM, 2006. http://pastel.archives-ouvertes.fr/pastel-00002602.
Texto completo da fonteDuchaussoy, Amandine. "Déformation intense d'alliages d'aluminium à durcissement structural : mécanismes de précipitation et comportement mécanique". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR135.
Texto completo da fonteThe combination of two mechanisms to increase mechanical strength, namely precipitation and grain size reduction, has been explored in this thesis in the aim of increasing the properties of age hardenable aluminum alloy from the 7### series.Manufacturing by severe plastic deformation makes it possible to obtain nanostructured alloys with high density of grain boundaries, which allows increasing the yield strength according to the Hall-Petch law. However, the high density of defects (dislocations, vacancies, grain boundaries ...) and the internal stresses generated by this deformation results in inherently unstable nanostructures when precipitation heat treatment is performed. These nanostructures experience rapid grain growth and drastic changes in precipitation mechanisms (heterogeneous precipitation, accelerated kinetics).In this work we have studied nanostructures obtained by severe plastic deformation using HPT and HPS (High pressure torsion / sliding) on a model alloy, Al-2% Fe and a commercial alloy AA7449 enriched with iron. The strategy was to stabilize the ultra-fine grain structure by intermetallic iron-rich nanoparticles (Zener pinning) to allow homogeneous precipitation hardening and thus combine the two mechanisms to increase the yield strength. In this context, we have particularly investigated: 1) the influence of solutes on the physical mechanisms leading to dynamic recrystallization nanostructuring; 2) specific mechanisms involved in co-deforming phases with very different mechanical behaviors; 3) the phase transformations that may lead either to the formation of a supersaturated solid solution or, on the contrary, to the decomposition of a solid solution by deformation-induced precipitation; 4) the relationship between the nanostructures thus generated, their thermal stability and related mechanical properties.The observation of the microstructures and understanding of the mechanisms induced by the deformation and relations with the mechanical behavior has been undertaken with many techniques: scanning and transmission electron microscopy (SEM/TEM), ASTAR (orientation mapping by TEM), and atom probe tomography. The study of precipitation was carried out by DSC (differential scanning calorimetry), SAXS (small angle X-ray scattering) and in-situ TEM. Finally, the relationship with the mechanical behavior has been established on the basis of tensile tests and micro-hardness measurements
Seghini, Maria Carolina. "Mechanical Analysis and Fibre/Matrix Interface Optimization for Next Generation of Basalt-Plant Fibre Hybrid Composites". Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0003.
Texto completo da fonteGlobal awareness of environmental issues has resulted in the emergence of “green” composites, in which natural fibres are used to replace synthetic ones. However, in semi-or structural applications, it can be inconvenient to use composites based on natural fibres. A possible solution to this problem is the development of hybrid composite materials, combining together plies of natural and synthetic fibres. In this framework, the aim of this research project was to develop basalt-flax fibre hybrid composites with a view to obtaining more environmentally friendly composites for semi-structural applications. Hybrid composites were produced through vacuum infusion molding with epoxy matrix.For comparison purposes, 100% flax fibre composites and 100% basalt fibre composites were also manufactured. A quasi-static and dynamic mechanical characterization showed that the hybridization allows the production of a composite with intermediate mechanical performances compared to those possessed by flax and basalt composites. However, the damage analysis has revealed the need to optimize the fibre/matrix interface adhesion quality, in order to increase the mechanical properties of the resulting hybrid composites. For this reason, different surface modification treatments have been specifically designed and investigated for flax and basalt fibres. Flax and basalt fibres were treated by the physical process of Plasma Enhanced Chemical Vapor Deposition. Flax fibres were also subjected to two chemical treatments using enzymatic species and supercritical CO2. The effects of the surface modification treatments on the thermal stability, morphology and mechanical properties of flax and basalt fibres have been investigated. The degree and extent of fibre/matrix adhesion were analyzed by micromechanical fragmentation tests on monofilament composites. The adhesion quality between fibres and both epoxy and vinylester matrices has been assessed in terms of critical fragment length, debonding length and interfacial shear strength. High-resolution μ-CT has been used to support the analysis of the damage mechanisms during fragmentation tests. For both flax and basalt fibres, the best results were obtained after the plasma polymer deposition process. This process was able to produce a homogeneous tetravinylsilane coating on the surface of basalt and flax fibres, which resulted in a significant increase in the fibre/matrix adhesion, thus paving the way for the next generation of more environmentally friendly hybrid composites for semi-structural applications
Boulnat, Xavier. "FAST high-temperature consolidation of Oxide-Dispersion Strengthened (ODS) steels : Process, microstructure, precipitation, properties". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0139/document.
Texto completo da fonteThis work aims to lighten the understanding of the behavior of a class of metallic materials called Oxide-Dispersion Strengthened (ODS) ferritic steels. ODS steels are produced by powder metallurgy with various steps including atomization, mechanical alloying and high-temperature consolidation. The consolidation involves the formation of nanoparticles in the steel and various evolutions of the microstructure of the material that are not fully understood. In this thesis, a novel consolidation technique assisted by electric field called "Spark Plasma Sintering" (SPS) or "Field-Assisted Sintering Technique" (FAST) was assessed. Excellent mechanical properties were obtained by SPS, comparable to those of conventional hot isostatic pressed (HIP) materials but with much shorter processing time. Also, a broad range of microstructures and thus of tensile strength and ductility were obtained by performing SPS on either milled or atomized powder at different temperatures. However, SPS consolidation failed to avoid heterogeneous microstructure composed of ultrafine-grained regions surrounded by micronic grains despite of the rapid consolidation kinetics. A multiscale characterization allowed to understand and model the evolution of this complex microstructure. An analytical evaluation of the contributing mechanisms can explain the appearance of the complex grain structure and its thermal stability during further heat treatments. Inhomogeneous distribution of plastic deformation in the powder is argued to be the major cause of heterogeneous recrystallization and further grain growth during hot consolidation. Even if increasing the solute content of yttrium, titanium and oxygen does not impede abnormal growth, it permits to control the fraction and the size of the retained ultrafine grains, which is a key-factor to tailor the mechanical properties. Since precipitation through grain boundary pinning plays a significant role on grain growth, a careful characterization of the precipitation state was performed on consolidated ODS steels. The experimental data obtained by transmission electron microscopy, small angle neutron scattering and atom-probe tomography evidenced the presence of dense and nanosized particles in SPS ODS steels, similarly to what is observed in conventional ODS steels. This is of great importance since it proves that the precipitation is very rapid and mainly occurs during the heating stage of the consolidation process. Using a thermodynamic model, the precipitation kinetics of Y2O3 and Y2Ti2O7 were successfully reproduced at various consolidation temperatures. Both experimental and numerical findings agree with the rapid precipitation of nanoparticles that are then extremely stable, even at high temperature. Consequently, this model can be an efficient tool to design ODS steelsby the optimization of the precipitation state
Meng, Liang. "Reduced shape-space : approach to material characterization instrumented indentation test case". Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2377/document.
Texto completo da fonteThe thesis lies at the intersection of three disciplines : numerical methods, experimental techniques, and machine learning. The primary aim of this work is to develop a group of algorithms for characterization by inverse analysis of a material’s constitutive law. In the field of material characterization, indentation test is especially attractive since it is considered non-destructive, and may be performed even on a structure in service. The test, similar to a hardness test, consists in penetrating an indenter into the surface of the material. The force exerted on the indenter is recorded against the penetration depth over a series of time instants, leading to a force-displacement (P-h) curve, which is the most frequently used source of information for the identification of material properties. However, the inverse problem based solely on this curve tends to be ill-posed, leading to nonunique identification solution, i.e., the "mystical material pair", for whom the corresponding force-displacement curves are almost identical despite the very different material properties. The basic idea is then to complete the identification process with innovative experimental measurements, such as laser microscope, which allows measuring the 3D residual imprint after the withdrawal of the indenter. To address the advantage of this measurement over P-h curve, we propose to construct, within a reduced affine space, a manifold of shapes admissible to the postulated constitutive law, experimental and simulation setups, based on synthetic data. The intrinsic dimensionality of the manifold limits the number of identifiable parameters allowing to validate numerically experimental procedures. Considering both the model and measurement errors, we develop a series of local manifold learning algorithms to solve the inverse problem iteratively for experimental results obtained in cooperation with INSA de Rennes. This approach allows us to characterize diverse metallic materials of increasing complexity, based on actual experimental measurements. For example, for the Hollomon’s law, the mystical pair is alleviated in using a single imprint, while for the Voce law, a multi-depth experimental protocol is proposed to differentiate mystical siblings
Murat, Denis. "Oxyde d'yttrium : élaboration et propriétés mécaniques". Limoges, 1995. http://www.theses.fr/1995LIMO0007.
Texto completo da fonteBergonnier, Sandra. "Relations entre microstructure et propriétés mécaniques de matériaux enchevêtrés". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00136408.
Texto completo da fonte- Une analyse du procédé de crêpage à partir de vidéos numériques permettant de déterminer localement les champs de taux de déformations au sein de la crêpeuse et de quantifier la cinématique d'une crêpeuse.
- Une analyse du produit fini : à partir de photos de produit texturé, un outil de détermination de l'anisotropie locale a été mis en place. Cette anisotropie est liée aux performances mécaniques du produit. Cette interaction a été mise en évidence expérimentalement et une modélisation du comportement mécanique élastique anisotrope du matériau étudié a été proposée.
Bergonnier, Sandra. "Relation entre microstructure et propriétés mécaniques de matériaux enchevêtrés". Paris 6, 2005. https://tel.archives-ouvertes.fr/tel-00136408.
Texto completo da fonteVilfayeau, Jérôme. "Modélisation numérique du procédé de tissage des renforts fibreux pour matériaux composites". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0026/document.
Texto completo da fonteThe aeronautical industry faces new challenges regarding the reduction of fossil fuel consumption. One way to address this issue is to use lighter composite materials. The ability to predict the geometry and the mechanical properties of the unit cell is necessary in order to develop 3D reinforcements in composite materials for these aeronautical applications. There is a difficulty to get realistic geometries for these unit cells due to the complexity of their architecture. Currently, existing tools which model 3D fabrics at a meso scale don't take into account manufacturing process influence on the shape modification of the textile structure. There is already some numerical tools that can model the braiding or knitting process, but none have been developed for weaving so far. Consequently, this study deals with the numerical simulation of the weaving process to obtain a deformed dry fabric structure. During the weaving process of E-glass fabrics, achieved in our laboratory, it has been observed that large deformations led to the modification of transverse section of meshes, or local density changes, that can modify the fabrics mechanical resistance. For this reason, a numerical tool of the weaving process, based on finite element modelling, has been developped to predict these major deformations and their influences on the final textile structure. The correlation between numerical results and fabrics produced with glass fibres has been achieved for plain weave and 2-2 twill
Popoff, Michka. "Étude à l’échelle du nanomètre des propriétés mécaniques et électriques de systèmes biologiques". Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10220/document.
Texto completo da fonteThe atomic force microscope (AFM) is a powerful tool for the study of biological systems. In this work, I was interested in the correlation of four types of microscopies: the atomic force microscopy, the high resolution fluorescence microscopy, the electron microscopy and the kelvin force microscopy (KFM). The correlation of the three first types of microscopies gave birth to the CLAFEM approach (Correlative Light Atomic Force Electron Microscopies). This technique allowed me to detect intracellular organelles, like the Golgi apparatus and mitochondria. Actin tails due to the infection of cells by the Shigella flexneri bacterium, and the entry site of Yersinia pseudotuberculosis bacteria were imaged with this approach. In parallel to this experimental part, I developed a software, called pyAF, for the analysis of force curves and the correlation of the different types of microscopies. In a second part, I measured electrical properties by KFM and explored the possibility to use KFM in liquid. Electrical properties of tobacco mosaic viruses were studied in air, using conventional cantilevers. I also used a new type of probe, called Kolibri, which is a quartz resonator oscillating at 1 MHz, in air and in liquid
Meukam, Pierre. "Valorisation des briques de terre stabilisées en vue de l'isolation thermique de batiments". Cergy-Pontoise, 2004. http://biblioweb.u-cergy.fr/theses/04CERG0287.pdf.
Texto completo da fonteIn this work, an experimental study was carried out in order to determine the properties of local materials used as construction materials. The thermal properties of lateritic soil based materials were deterrnined. The effect of addition of natural pozzolan or sawdust in lateritic soil brick on the thermal properties is examined. It was shown that the effect of incorporation of natural pozzolan or sawdust is the decreasing of the thermal conductivity and density. The moisture content of these materials can modify their thermal performance. Thus a study of the influence of the water content on the thermal conductivity L and the thermal diffusivity a is presented. The effect of the increasing of cement content is to increase the thermal conductivity and to decrease the thermal diffusivity. The composite materials used for building shielding present sufficient mechanical strength and are suitable for constructions. The analysis is developed for the prediction of the temperature, relative humidity and water content behaviour within the walls. A numerical model HMtrans, developed for prediction of heat and rnoisture transfer in multi-Iayered building cornponents, is used to simulate the temperature, moisture content and humidity profiles within the building envelopes. The results allow the prediction of the duration of the exposed building walls to the local weather conditions. There is therefore minimum possibility of water condensation in the materials studied. The durability of buiIding envelopes made of lateritic soil bricks with incorporation of natural pozzolan or sawdust is not strongly affected by the climate conditions in tropical and equatorial regions
Lachhab, Touria. "Etude des propriétés mécaniques d'empilements désordonnés de billes de gel". Marne-la-vallée, ENPC, 1994. http://www.theses.fr/1994ENPC9408.
Texto completo da fonteThummen, Frédéric. "Propriétés mécaniques et durée de vie de bétons réfractaires". Lyon, INSA, 2004. http://theses.insa-lyon.fr/publication/2004ISAL0027/these.pdf.
Texto completo da fonteRefractories are responsible for high and recurrent costs in CFB (Circulating Fluidised Bed) power plants. The major origins of the degradations of these materials are caused by thermal shocks and constrained dilatation during the different temperature cycles. The purpose of this study is first to better describe the mechanical behaviour and the damage of these refractories – which is still mostly unknown – and then to develop some damage prediction techniques. We have studied through non destructive techniques (acoustic emission, ultrasounds) the damage of two refractory concretes during 4-point bending tests, compression tests and tensile tests as well as their behaviour in fatigue. In order to be able to predict the service life of these materials in fatigue, we used a simple power law phenomenological model. This allowed to predict the time to failure as function of cycle amplitude and maximum stress. Acoustic emission appears to be a reliable indicator of the damage. Moreover, the acoustic emission data processing by a classificator (k-mean) enables us to separate the useful signal from the background noise. This analysis appeared effective in laboratory and simulated industrial environment. Lastly, the modeling of the lifetime in fatigue enabled us to propose various damage mechanisms during the fatigue test
Fourcade, Thibaut. "Études des propriétés mécaniques de matériaux métalliques en couches minces". Thesis, Toulouse, INPT, 2013. http://www.theses.fr/2013INPT0071/document.
Texto completo da fonteThe thin films are used in a large number of industrial fields such as Micro- and Nano- Technology (MNT) or treatment of surfaces. They can be used either as layer structures, or to provide protection functions or functionalized surfaces. There are generally two types of thin layers deposited thin films and self-supporting thin layers. The objective of the work presented in this manuscript is to develop methods for mechanical characterization of elastic-plastic behavior of free-standing thin films and deposited. First, we present a microtensile test able to work on 750 nm thick layers and associated technical means. These tools allow to characterize the elastic-plastic properties and mechanical damage freestanding thin films. In a second step, we focus on the implementation of parametric identification methods associated with implementation of instrumented indentation testing in the context of characterizing the elastic-plastic behavior of the deposited thin film materials. The layers characterized in this study are multilayer NiCo In total thickness 22 microns and thin layers of aluminum produced from several procédées with thicknesses between 1 and 1.5 microns
Mrabti, Abdelali. "Propriétés opto-mécaniques dans des matériaux nanostructurés : couplage plasmons-phonons". Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10201.
Texto completo da fonteThis thesis is focused on the elastoplasmonic coupling in periodic nanostructured systems. This interaction plasmon/phonon has been studied first for a metal nanowire inserted into a cavity of a two-dimensional crystal, consisting in a periodic array of holes in a dielectric matrix. The second investigated system is a crystal with sustaining local resonances. The crystal is formed by a square array of gold nanocylindres deposited on a non-absorbing dielectric membrane. The interest of such a system is that it can support phonon modes localized in the nanocylindre enabling thus an efficient coupling with plasmon modes. The third system is a crystal constituted by a metal nanoparticles array coupled to a metal film via an ultra thin dielectric spacer (silica). The motivation behind such a study is twofold: first, plasmon modes are sensitive to small local deformations due to their strong confinement; second such a system supports many localized phonons that can provide a local amplification of vibrations. It is then a dual cavity for phonon and plasmon modes. For the three systems studied in this thesis, we have shown that mechanical vibrations can modulate during an acoustic period the wavelength of the plasmon resonance modes supported by the structure