Lorsqu'elle est chauffée, la roche peut subir une microfissuration thermique, qui influence ses propriétés physiques, mécaniques, thermiques, et de transport. La surveillance de la microfissuration thermique en laboratoire a été principalement réalisée pendant le chauffage, et rarement lors du refroidissement ou du chauffage cyclique que la roche subit dans les volcans et les réservoirs géothermiques. Un nouvel appareil a été élaboré pour surveiller les émissions acoustiques et mesurer les vitesses des ondes élastiques à haute température. L'état de fissuration a été évalué grâce à un nouvel algorithme d'analyse microstructurale, et l'influence des microfissures sur les propriétés des roches a été mesurée et modélisée. Selon la microstructure, la microfissuration peut avoir lieu pendant le chauffage ou le refroidissement, et les microfissures existantes peuvent s’ouvrir et se fermer de façon réversible avec des changements de température, et influencer les propriétés de la roche. / Rock may undergo thermal microcracking when heated, affecting its physical, mechanical, thermal, and transport properties. Thermal microcrack monitoring in the laboratory has mainly been performed during heating, and rarely during the cyclic heating and cooling relevant for volcanoes and geothermal reservoirs. For this, a new dedicated apparatus for the acoustic emission monitoring and wave velocity measurement at high temperatures was elaborated, building on previous designs. Microcrack damage was assessed with a new algorithm for quantitative microstructural analysis, and the influence of thermal microcracks on rock properties was measured and modelled. Depending on the rock type and initial microcrack content, microcracking occurred during either heating, cooling, or neither, and existing microcracks reversibly opened or closed with increasing temperature. In Earth's crust, the evolution of rock properties with temperature may be significant and is determined by the microstructure.

Cette étude expérimentale traite la localisation des déformations sur un grès poreux: le grès de Vosges. Un nombre des essais triaxiaux sont effectués sous des pressions de confinement (i.e., 20 MPa - 190 MPa) et des déformations axiales différentes pour mieux comprendre la réponse mécanique de ce grès. La localisation des déformations a été étudiée dans des différentes échelles en appliquant une variation de mesures de champs (full-field methods) comme la Tomographie Ultrasonore (en 2D), les Emissions Acoustiques (en 3D), les Rayons X (en 3D), et la Corrélation des Images (en 3D). Les méthodes expérimentales ont été appliquées avant, pendant et après les essais triaxiaux. Des coupes fine ont été observées sous le microscope optique et électronique (SEM). La combinaison des multiples techniques expérimentales, qui ont des différentes sensitivités et résolutions, a décrit la procédure de la formation et l’évolution des bands de déformation observées sur le grès de Vosges. Des bandes de cisaillement ont été formées sous des pressions intermédiaires et des bandes de compaction sous des pressions élevées. Des bandes de compactions pure n’ont pas été observées.Les bandes de déformations observées se sont caractérisées comme des zones de déformation de cisaillement localisée et/ou de compaction. En plus, elles se sont caractérisées comme des structures de fable vitesse ultrasonore, des places d’origine des fissures inter- ou intra- granulaires, et des places des densités de matériel élevées.Deux mécanismes principales ont été observées au niveau de grain dans les bandes de cisaillement et de bandes de compaction (shear-enhanced compaction bands): d’un cote c’est la fissuration des grains (endommagement) et de l’autre cote c’est la réduction de porosité (sur la forme de compaction). Les deux mécanismes i présent différences sur leurs proportions et leur ordre d’occurrence dans le temps. / This PhD thesis presents a laboratory study aiming at a better understanding of the stress-strain response of the Vosges sandstone (porous rock) tested at a range of confining pressures (i.e., 20-190 MPa) and different axial strain levels. Localised deformation was captured at different scales by a combination of full-field experimental methods, including Ultrasonic Tomography (2D), Acoustic Emissions (3D), X-ray Tomography (3D), and 3D volumetric Digital Image Correlation, plus thin section and Scanning Electron Microscope observations (2D). These experimental methods were performed before, during and after a number of triaxial compression tests. The combined use of the experimental techniques, which have different sensitivity and resolution, described the processes of shear band and shear-enhanced compaction band generation, which formed at low to intermediate and relatively high confining pressures, respectively. Pure compaction bands were not identified. The deformation bands were characterised as zones of localised shear and/or volumetric strain and were captured by the experimental methods as features of low ultrasonic velocities, places of inter- and intra-granular cracking and structures of higher density material. The two main grain-scale mechanisms: grain breakage (damage) and porosity reduction (compaction) were identified in both shear band and shear-enhanced compaction band formation, which presented differences in the proportions of the mechanism and their order of occurrence in time.

Dans un contexte automobile électrique et hybride, la part des machines synchrones à aimants permanents s'est accrue exponentiellement. Cette évolution s'accompagne d'exigences en termes d'émissions vibro-acoustiques. En termes de dimensionnement de la chaîne de traction, l'analyse multiphysique du moteur s'avère être un enjeu crucial pour son développement. La nécessité de disposer de codes informatiques de conception possédant des temps de calcul faibles pour une précision maximale se fait ressentir pour l'exploration de solutions potentiellement performantes dans les premières étapes du processus de dimensionnement. A ce titre, les aspects vibratoires et acoustiques sont modélisés analytiquement et par éléments finis dans la présente thèse. Ainsi, au moyen du modèle magnétique, l'analyse magnéto-vibro-acoustique faiblement couplée (résolution itérative des différentes physiques) peut être réalisée.La thèse est découpée en quatre parties. La première expose un état de l’art sur les émissions vibro-acoustiques des machines et notamment la modélisation du bruit d’origine magnétique. Les problématiques de la modélisation sont détaillées. Dans une deuxième partie, les modèles sont largement décrits. Les modèles éléments finis sont validés expérimentalement. Une troisième partie se propose de valider les modèles analytiques par éléments finis, en complexifiant progressivement la géométrie d’une machine à aimants montés en surface à flux radial. Enfin, la dernière partie utilise les modèles éléments finis pour étudier des machines non-conventionnelles comme les machines à commutation de flux et les machines à aimants en surface à flux axial. / The proportion of permanent magnets synchronous motors used for electric and hybrid automotive traction has exponentially increased during the past decade. This evolution comes with ever-demanding low noise and vibrations requirements. Multi-physics analysis of the motor is a decisive issue for the development of the powertrain. For the exploration of potentially efficient motor solutions in first design steps, it is thus a necessity to have at disposal fast and accurate computer codes. In this respect, acoustic and vibratory aspects are modeled using finite element and analytical models in this thesis. As a result, using an electromagnetic model, the weakly-coupled magneto-vibro-acoustic analysis (iterative solving of each physic) can be performed.The thesis is divided into four parts. The first part states the art on machine vibro-acoustic emissions and focuses on noise of magnetic origins modeling. Issues of modeling are detailed. Then, models are described to a great extent in the second part. Finite element models are favorably compared to experimental measures. A third part validates analytical models in comparison to finite element analysis, by gradually complicating the geometry of a surface permanent magnets radial flux machine. Finally, a fourth part uses finite element models to study non-conventional machines such as flux switching radial flux machines and surface permanent magnets axial flux machines.

<p>Probing the subsurface for evidence related to the degradation of porous mediums and the evolution of damage mechanisms has been a long-standing challenge in geophysics. As such imaging and predicting fracture network development has remained a difficult area for subsurface science for decades despite the seminal and significant works put forward by many researchers. While this has provide great understanding about the behaviours and properties of natural porous media, there is still much that needs to be explored particularly in regard to the mineralogical composition and chemistry of clay-rich rocks. Despite the fact that argillaceous rocks which consist of different types of clays and varied mineral composition are ubiquitous in nature and are often the target of several technologies (e.g. geotechnical engineering, nuclear waste storage and disposal,hydrocarbon exploration and extraction, carbon capture and sequestration, etc.), many studies focus primarily on the bulk properties or the percentage of components in the matrix. For these reason and due to the problems that can be encountered with natural rocks that contain a swelling clay component whether randomly distirbuted or localized in consolidated globs in zones of the matrix, the influence of clay chemistry in relation to fracture development which is not well characterized, especially during desaturation is investigated with analogue rock samples which were systematically fabricated for this purpose.</p> <p><br></p> <p>The research performed in this dissertation investigated, the applicability of  the fabrication protocol for developing synthetic rocks with desirable rock like features and behavior, the impact and relationship between the rock properties, the microstructural composition, water loss, and the macroscopic behavior of the analogue rocks, focusing on the structure and chemistry of the constituent clay materials. Synthetic rocks were fashioned with the necessary geometries, properties, and material compositions. On the macroscopic scale the fracture and drying behavior of the synthetic rocks were examined with 3D X-ray microscopy and further evaluated through the utility of acoustic emission monitoring, water loss monitoring, and unconfined compressive testing. On the finer scale (nano-microscale), the chemical and mechanical properties, and behavior of select clays was explored by exploiting several methods of material characterization which also included cation exchange experiments coupled with inductively coupled plasma – optical emission spectrometry (ICP-OES). </p> <p><br></p> <p>For the finer scale, experiments verified that calcined kaolinite clay had a different mineral structure and negligible to non-existence shrinkage abilities. In contrast, the montmorillonite clays possessed higher and similar moisture contents but, owing to the different principal cations these clays interacted a bit differently in the highly akaline environment, experienced varying degrees of shrinkage, and had observedly minor structural dissimilarities. For the relatively larger scale, the emergence of damage, extent of the damage network, and the patterns of the crack network mainly depended on the microstructural composition of the analogue rocks, particularly it's clay chemistry and/ or distribution. The location of damage depended on the emplacement and percentage of swelling clay in the matrix, and numerical investigations with peridynamics revealed that the observed damage was a consequence of the action of the swelling and non-swelling components of the matrix. Furthermore, if the microstructure consisted of no clay or calcined kaolinite the AE activity was solely attributed to interfacial processes that occurred during fluid front movement. If the microstructure consisted of a particular montmorillonite, the cracks propagated in the direction of the drying front. Conversely, for montmorillonite clay predominated by a different principal cation, the crack network developed and propagated differently during water loss. Additionally, on the laboratory core scale, properties and behavior similar to natural rocks were confirmed and the rock strength, porosity, AE activity, and velocities were primarily affected by the microstructural composition of the analogue rocks. </p> <p><br></p> <p>An added challenge for investigating and monitoring evolving systems and processes, whether on the laboratory or field scale, is the problem of extracting useful information from the physical data that can be used to identify signatures of developing processes, and changes in the properties or the behavior of a system. Here, data driven machine learning modeling and clustering techniques were undertaken to build a mechanistic understanding of the AE activity generated during drying. The intent is for this work to add to the fundamental research aimed at developing methods that will robustly detect and extract signatures related to evolutionary processes or features in the AE signals, and group them according to some degree of similarity. Such research will support reliable interpretations of the physical data for predictions of the behavior of systems, development of engineering controls, and improvement of the understanding of intrinsic dynamics related to complex processes particularly those that occur in clay-rich systems.</p> <p><br></p> <p>Combined chemical and mechanical investigations have great potential for unraveling practical challenges in subsurface science, especially regarding damage processes in clay-rich rock systems, and identifying and interpreting the presence of discontinuities from geophysical data. The present findings are useful for establishing a link between the constituent clay and observed damage, and improving our understanding of the development of damage in clay-bearing systems. These results provide insight on the influence of swelling clay and the chemistry of such clays on the generation of cracks and crack networks in rock like materials which can be useful for the characterization of damage in both laboratory and the field. The work presented here can also be a basis for further experiments that aim to uncover methods and protocols that will help with the indirect characterization of evolutionary processes, damage mechanisms, and damage in clay rich porous media. Additionally support for the use of analogue rocks in experimental rock physics, architected with specific material compositions, pore structures, crack systems, or clay fractions, is provided here. </p>