WorldCat Identities

École doctorale Mécanique, énergétique, génie civil et procédés (Toulouse)

Overview
Works: 726 works in 1,005 publications in 2 languages and 1,018 library holdings
Roles: Other, Degree grantor, 996
Publication Timeline
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Most widely held works by énergétique, génie civil et procédés (Toulouse) École doctorale Mécanique
Investigation of crack propagation in X38CrMoV5 tool steel at room temperature and 600°C on small scale specimens by Sayyid Masoodur Rahman Shah( Book )

2 editions published in 2010 in English and held by 3 WorldCat member libraries worldwide

Les outillages de mise en forme à chaud, sont soumis à des chargements thermomécaniques sévères, qui endommagent leur surface. Une nouvelle méthode de caractérisation de l'endommagement par fatigue est proposée. Des éprouvettes de dimensions réduites, représentatives de la surface, ont été utilisées. Les essais de propagation de fissure en fatigue sur l'acier à outil X38CrMoV5 traité à 47 HRC sont réalisés à la température ambiante et à 600°C. Les effets de l'épaisseur de l'éprouvette, du rapport de charge et de la température ont été étudiés. Différents paramètres de propagation de fissure ont été établis à l'aide de la simulation numérique. Une méthode de mesure de l'ouverture en fond de fissure, utilisant une caméra numérique et un microscope à longue portée, a été développée. Les images acquises sont ensuite traitées par corrélation d'images pour mesurer l'ouverture de fissure. Un modèle de propagation de fissure basé sur l'ouverture en fond de fissure a été développé
Comment la durée de vie des bâtiments peut-elle influencer les performances en termes de développement soutenable? by Marc-André Mequignon( )

2 editions published in 2011 in French and held by 3 WorldCat member libraries worldwide

The purpose of this thesis is to highlight the importance of the lifespan of the buildingand its components and and as well as to see it in the light of constraints imposed bysustainable development criterias. The focuse of our paper is to characterize the behavior inthis approach, namely environmental, economic and social features.After presenting and analyzing the state of art concerning the lifespan of the building andapproach the building in terms of sustainable development, we characterize the impact of theformer on the latter. Our method is based on two objects of study :- The first is a wall unit outside. This allows us to define precisely the function of useand the technical solutions more specifically for this function;- The second study is a housing-type building. This method is based on that of the wallunit, but we can check behaviour of each technical solutions in the use stage. Thus, we caneasily produce results commensurate.The first approach involves assumptions of lifetimes of technical solutions with which wemake the simulations. In a second step, the analysis takes into account the lifespan as avariable and we analyze the consequences in terms of sustainable development.To promote the exploitation of knowledge produced and to situate them within theproject approach, we propose a schematic modification of current tools for assessingperformance
Vers des outils d'aide à la conception pour intégrer les dimensions techniques, écologiques et sensibles des matériaux de construction by Nathalie Tornay( )

2 editions published in 2011 in French and held by 3 WorldCat member libraries worldwide

The choice of materials and way of implementation is known and will be known as a significant growth in the world of architecture. Actually, changes are largely induced by technical dimension, but also representations and precepts that appear with the emergence of the concept of sustainable development in our society.Design support tools about materials scale focus on the physical dimensions (thermal, life cycle, refreshments, etc.). Our work is questioning the integration of technical, environmental and sensible dimensions in a design support tool based on reference. The referential activity is a specific approach in the initial phases of designing on a project. These phases correspond to crucial choice, which remain poorly assisted by digital tools.Our work aims to highlight the different characteristics of materials, but also their interactions. This study differs from conventional approaches of materials, which generally, constructive solutions are presented material by material. Indeed, we rely on a data structure and interdisciplinary knowledge (architecture, urbanism, landscape, aesthetic, technical, cognitive, perception approach, environmental approach, etc.).This research tends to be a first proposal for a design support tool named DILEM'MAtériaux that takes into account materials in their contribution to origin of founding ideas and definition of concept, in the initial phases of designing on a project
Effect of gravity on convective condensation at low mass velocity by Lan Phuong Le Nguyen( Book )

2 editions published in 2017 in French and held by 3 WorldCat member libraries worldwide

Liquid-vapor two-phase flows have common applications in many fields including space thermal management systems. The performances of such systems are entirely associated to the coupling between thermal and hydrodynamic phenomena. Therefore, two-phase flows in microgravity condition have emerged as an active research area in the last decades. In order to complete the state of the art and to contribute to the increase in the knowledge of hydrothermal behavior of two-phase thermal management systems, the present study was conducted on convective condensation inside a mini tube, both in normal and micro gravity conditions. To analyze the effect of gravity on such flows, a preliminary transient modeling of the two-phase flow has been established. Simultaneously, an experimental investigation was carried out on the hydrodynamic and thermal behaviors of condensation flows in two test sections of 3.4 mm inner diameter at low and intermediate mass velocities. The first experiment was conducted during the 62nd ESA parabolic flights campaign. The test section was made with copper and allowed measurements of the quasi-local heat transfer coefficient. A glass tube was also inserted in the middle of the test section for the visualization of the two-phase flow regime. From this study, the changes in heat transfer coefficient and flow regime according to gravity variations were determined. The second experiment was carried out on ground in a sapphire tube installed vertically considering downward flow. The set-up was designed in order to measure simultaneously the local heat transfer coefficient and the thickness of the liquid film falling down along the tube wall
Etude multi-échelle du couplage matériau-procédé pour l'identification et la modélisation des variabilités au sein d'une structure composite by Yves Angel Davila Montano( Book )

3 editions published in 2015 in English and held by 3 WorldCat member libraries worldwide

Une des problématiques liées à l'utilisation des matériaux composites dans les structures tient à la difficulté de prévoir l'effet des variabilités inhérentes à ce type de matériau sur le comportement mécanique. Les propriétés d'une structure composite dépendent non seulement du procédé, mais aussi des matières premières et des choix de conception. Dans le but d'introduire des variabilités géométriques dans le calcul numérique des pièces composites, on part dans ce travail de l'hypothèse que les variations des grandeurs géométriques ne sont pas distribuées totalement aléatoirement, mais que celles-ci suivent des évolutions spatiales continues. Pour que les valeurs d'entrée qui nourrissent le modèle numérique soient basées sur la réalité du matériau, l'identification et la quantification des plages de variabilités et de leurs évolutions sont réalisées sur la période de la fabrication de plaques composites CFRP comptant ici 16 plis avec une stratification quasi isotrope et polymérisées en autoclave. Parmi les sources de variabilité identifiées et quantifiées, l'étude de la répartition des désalignements des fibres dans le plan et de l'évolution des variations des épaisseurs des plis a mené à la proposition de lois mathématiques d'évolution spatiale basées sur la réalité du matériau dans la pièce. Ces lois mathématiques sont ensuite utilisées pour récréer numériquement plusieurs structures composites différentes de la structure observée mais qui possèdent des valeurs de dispersions des propriétés similaires aux plaques réelles. Enfin, les structures numériques sont analysées dans un modèle éléments finis pour évaluer l'impact des dites variabilités géométriques et matériaux sur les propriétés mécaniques de la structure finale au travers de plusieurs études de cas
Stéréo corrélation d'images numériques éléments finis : application à la validation de modèles de structures composites sous sollicitations complexes by Jean-Emmanuel Pierré( Book )

2 editions published in 2016 in French and held by 3 WorldCat member libraries worldwide

VERTEX Project, to which this thesis belongs, aims to validate composite models by multi-axial static tests on specimens at the level of structural details. The positioning on this scale requires the development of both new instrumentation techniques and tools for the test/simulation dialogue, which are at the heart of this thesis. Given the complexity of this type of experiments, we focus here on Stereo Digital Image Correlation (SDIC) since it yields 3D displacement fields on the surface of the specimen. However, if we stick to conventional approaches, it is difficult to make quantitative comparisons between a measured field and a Finite Element (FE) simulated field. Thus, in this work, a framework is developed to make a measurement by SDIC in the physical coordinate system based on an FE model (calibration of non-linear camera models , FE shape measurement, FE field measurement). This method gives access to experimental displacement fields directly expressed both in the coordinate system and support of the FE simulation, which considerably simplifies validation. To validate a model at the scale of structural details, the question of boundary conditions is fundamental. This question is even more complex since the kinematic measurement is limited to the visible surface. In addition to this surface measurement, it is here envisioned to estimate additionally the boundary conditions in the thickness of the specimen relying on a plate/shell-like model (classic or volume). Different approaches are considered depending on the confidence giving to this model. This methodology is implemented in an academic software and is applied to synthetic tests. The development of a dedicated instrumentation also allowed the analysis of tests performed on the VERTEX bench
Valorisation de sédiments traités en techniques routières : contribution à la mise en place d'un protocole d'acceptabilité by Christelle Tribout( Book )

2 editions published in 2010 in French and held by 3 WorldCat member libraries worldwide

Dredging sediments is necessary to ensure navigation but extracted sediments are often polluted. The Solvay Company has been working on the development of a treatment: the Novosol® process. It allows fixing heavy metals and eliminating organic matter. This article reports on the characteristics of a treated sediment and on its use in road building techniques. From mechanical point of view, the mixtures incorporating sediments are standard. The environmental tests carried out on the mixtures show that the release of heavy metals and other species is the same whether the materials incorporate the treated sediment or not. These results suggest that the beneficial use of treated sediments in road building techniques is relevant
Modélisation du procédé de cuisson de composites infusés par chauffage infra rouge by Sawsane Nakouzi( Book )

2 editions published in 2012 in French and held by 3 WorldCat member libraries worldwide

L'utilisation des matériaux composites dans les secteurs aéronautique et aérospatial a évolué au cours des dernières années. Ces matériaux à hautes performances présentent des propriétés mécaniques et physiques élevés. Une nouvelle méthode de mise en œuvre de ces matériaux qui pourrait amener un gain en temps et d'énergie est la polymérisation du composite à l'aide d'un four infrarouge. Cette technique de chauffage infrarouge peut s'appliquer en particulier au processus d'infusion de résine LRI (Liquid Resin Infusion) où la résine est infusée à pression atmosphérique dans un demi moule qui contient le renfort fibreux et ayant une surface de recouvrement semi-transparente aux rayons infrarouges. L'injection se fait à l'aide d'une pompe à vide et le composite est placé face aux émetteurs infrarouges. Ces émetteurs sont de type halogène et sont fournis par la société TOSHIBA LIGHTING. Le chauffage commence après injection totale de la résine et sa stabilisation dans le moule. Par conséquent, le composite est soumis à un flux radiatif incident, lequel est absorbé par le premier pli de carbone présent à sa surface. Ceci est due au fait que les fibres de carbone présentent une absorptivité assez élevée qu'on peut donc considérer le composite opaque vis-à-vis de l'infrarouge. Un modèle de calcul par éléments finis basé sur la méthode des radiosités a été développé afin de prédire le flux radiatif absorbé par le composite. Ce modèle a été validé par une solution référence basée sur les algorithmes de lancer de rayons. Ce flux radiatif absorbé est imposé comme condition aux limites dans le logiciel commercial COMSOLMULTIPHYSICS. Celui ci résout par la méthode des éléments finis l'équation de chaleur couplée avec la cinétique de réticulation de la résine afin de modéliser la polymérisation par infrarouge. La température et le degré de réticulation au sein du composite sont ainsi calculées. Un algorithme d'optimisation a été couplé avec le modèle radiatif afin d'obtenir une distribution de température optimale dans le composite. Ces données issues de l'optimisation en été utilisée dans le protocole expérimental. Ce montage expérimental permettant le chauffage infrarouge du composite instrumenté a été réalisé au laboratoire afin de valider les résultats numériques de l'étape de chauffage à l'aide de thermocouple et de la thermographie infrarouge pour le cas d'une plaque composite et le cas d'une pièce 3D
Comportement des matériaux composites à renforts tricotés élaborés par injection de résine by Laura Baléa( Book )

2 editions published between 2011 and 2019 in French and held by 3 WorldCat member libraries worldwide

Les textiles tricotés présentent un grand intérêt pour le renforcement de composites et notamment pour la mise en oeuvre de pièces de formes complexes, cependant, l'orientation non alignée des fibres confère au composite des propriétés mécaniques limitées. L'amélioration de ces propriétés nécessite une optimisation de la contexture fibreuse. Dans ce contexte, le travail de thèse vise à étudier le comportement des composites à renforts tricotés et le mettre en relation avec l'architecture du tricot, la nature de la fibre et le comportement du textile sec. Dans un premier temps, le comportement des tricots secs a été étudié en fonction de leur architecture et de la nature de la fibre (verre, basalte et carbone) en se consacrant d'abord aux contextures de référence (côte et jersey), puis en insérant des mèches non tricotées dans la rangée du jersey. Dans une seconde phase, des composites renforcés de ces même contextures ont été élaborés par injection de résine et soumis à des essais de traction. La stéréo-corrélation d'images a été utilisée pour mettre en évidence l'hétérogénéité des déformations due au renfort fibreux et pour expliquer les différences de comportement en fonction de la direction de sollicitation. L'endommagement a été étudié par l'observation des faciès de rupture. Dans une dernière phase, une modélisation semi-analytique du comportement des tricots jersey secs basée sur la théorie de l'élasticité permet d'obtenir un modèle géométrique de la maille jersey quel que soit l'état de déformation du tricot. L'orientation des fibres calculée est utilisée pour alimenter un modèle d'estimation des propriétés élastiques des composites basé sur le principe d'homogénéisation. Les résultats sont comparés avec l'expérience et montrent une bonne corrélation. Ce modèle permet en outre de prendre en compte la présence des mèches insérées dans la rangée du jersey ainsi qu'une prétension initiale du renfort avant mise en oeuvre et ainsi, de définir une architecture du renfort optimisée pour améliorer les propriétés du composite
Modification of surface properties of biopowders by dry particle coating by Serkan Otles( Book )

2 editions published in 2008 in English and held by 3 WorldCat member libraries worldwide

L'enrobage des poudres est un procédé important dans le monde industriel. Ce procédé consiste en la modification des propriétés de surface et/ou des propriétés fonctionnelles de poudre qui ne possède pas ces propriétés initialement. La modification de la surface des particules peut être effectuée par enrobage en voi humide ou sèc. Cependant, l'enrobage humide devient de moins en moins souhaitable en raison de préoccupations environnementales due au reject de COV. Ainsi, l'enrobage à sec paraît être la technologie alternative adaptée pour éviter les inconvénients précédents tout en ayant des avantages tel qu'un faible temps de traitement, un faible coût énergétique ou encore d'être plus respectueux de l'environnement. L'enrobage à sec met en avant trois termes importants : le couple de poudre, le procédé et les propriétés d'usage des particules composites. L'objectif de cette étude est d'ameliorer connaissance fondamentale du procédé d'enrobage à sec pour mieux comprendre les interactions entre ces termes et aussi de classifier les critères qui affectent les propriétés d'usage des particules composées. Dans ce travail, deux différents couples modèls ont été traités avec différents équipements et les propriétés d'usage des particules ainsi obtenus ont été étudiées grâces à des techniques de caractérisation diverses. Dans la première partie de ce travail, nous avons d'une part, étudié le procédé et les conditions opératoires qui influencent le phénomène d'enrobage et d'autre part développé la technique AFM pour obtenir des informations sur la nature de l'enrobage effectué. La seconde partie quant à elle, traite de l'influence de la taille des particules hôtes et invitées sur les proprétés d'usage
Contribution à l'étude des variabilités des propriétés des stratifiés fabriqués par infusion de résine liquide by Alvine Njionhou Kepnang( Book )

2 editions published in 2011 in French and held by 3 WorldCat member libraries worldwide

The aeronautical sector is now very interested by the development of out-of-autoclave processes and low cost structures. The question is to find the possible links between the parameters of these new processes and mechanical properties of composite parts obtained. In this study, experimental plan method by Taguchi tables is used to establish the possible relationships between the process parameters of liquid resin infusion and the ultimate tensile strengths, ultimate compressive strengths and interlaminar shear strengths, and also the properties in impact and compression after impact of infused laminates. Laminates are infused using the quadriaxial Non-Crimp-Fabrics (NCF) stitched and unstitched with epoxy resin RTM 6. The possible links with the process parameters and morphological properties of these laminates such as fiber volume fraction, void contents, glass transition temperature and thickness of the structure have also been investigated. Eight process parameters (number of NCF layers, stitching, number of High Porous Media (HPM) layers, plate side during the infusion, vacuum level, injection temperature, mould temperature, curing temperature) and an interaction between the number of NCF layers and HPM layers have been identified by literature review. Statistical analysis using multilinear regression method was performed on the properties of infused laminates stitched and unstitched to find influence of parameters on each property. Stitching has a good effect on ultimate compressive strength and compression after impact strength. It contributes also to increase interlaminar shear strength and to reduce damage propagation inside material. Microscopic observations were done to complete and improve the comprehension of statistical analysis results. They allowed detecting presences, sizes, localisations, and number of residual voids inside laminates. Different damages modes caused by impact were also observed. Voids content obtained in infused laminates made is generally lower (less than 1%) with higher fiber volume fraction (greater than 60%). These results allow using this process for aircraft parts. The presence of macro voids goes to the reduction of ultimate strengths of infused laminates. These defects cause increase of residual indentation. The link established by experimental plan method seems to ensure the explication about the creation of the blocking debris of this indentation
Etude in situ sous gradient thermique de l'écaillage d'alliages alumino-formeurs et de barrières thermiques aéronautiques by Julien Sniezewski( Book )

2 editions published in 2008 in French and held by 3 WorldCat member libraries worldwide

Spallation of the alumina layer grown at high temperature at the surface of the alumina forming alloy PM2000 or that of EB-PVD thermal barrier coatings (TBCs) coated on Ni based alloys is studied using a dedicated equipment specially designed in the laboratory. The equipment is capable of imposing a thermal gradient through the sample thickness in order to test the materials in conditions as close as possible to real service condition. The equipment has also the capacity to monitor in situ the spalling events that occur during the cooling phase of samples using high resolution camera, high speed camera or infrared camera. The analysis of images performed with a dedicated software allows a accurate description of the mechanisms of spallation during the successive cycles as well as the spallation kinetics or the morphology of the spalled particules. The effects of various parameters on spallation are studied for alloy PM2000. Namely, a particular focus is placed on i) the surface roughness of the substrate ii) the oxide scale thickness, iii) the cooling rate, iv) the crystal orientation of grains, v) the number of oxidation cyles. The life of TBC is studied as a function of the oxidation temperature as well as the imposed thermal gradient. In addition, a attempt is made to determine the apparent toughness at the interface between the substrate and the TBC as well as its evolution with ageing time
Contribution à la modélisation de l'écoulement de résine dans les procédés de moulage des composites par voie liquide by Renaud Gantois( Book )

2 editions published in 2012 in French and held by 3 WorldCat member libraries worldwide

Liquid Composite Molding (LCM) is more and more used in industry for its ability to produce complex and large parts at low cost. However, this process needs a special care to anticipate properly the impregnation of the fibrous reinforcement, which remains a challenging task important to achieve. This work is divided into an experimental and a numerical study. It aims to model the resin flow through the fibrous reinforcement occurring during the mold filling stage. An experimental setup has been designed to measure both plane and transverse permeabilities of the reinforcement. The numerical study is focused on the simulation of the flow at macroscopic and microscopic scales. At macro scale, our main contribution is the coupling between BEM and Level Set methods, which has been achieved for both 2D and 3D problems. At micro scale, a stationary BEM solver has been developed to evaluate the transverse permeability of a 2D fibrous microstructure
Elaboration et étude des propriétés mécaniques et thermiques de matériaux constitués de nanotubes de carbone verticalement alignés by Jonathan Bouillonnec( Book )

2 editions published in 2015 in French and held by 3 WorldCat member libraries worldwide

Vertically aligned carbon nanotube carpets are potential candidates for applications such as interconnections or thermal interface materials (TIMs). This research work deals with the synthesis of aligned carbon nanotube carpets from the aerosol assisted chemical vapour deposition (CVD) technique, with the elaboration of nanocomposites made of different grades of epoxy matrix infiltrated within these carpets, as well as the study of both longitudinal and transverse mechanical and thermal properties of dry carpets themselves and 1D-nanocomposites separately. The synthesis conditions notably enable to vary characteristics of the differents carpets such as their thickness, their density, the mean external diameter of the carbon nanotubes (CNT), the intertube space and the CNT volume fraction, whereas their crystalline structure can be modified with a high temperature thermal treatment. The main goal of this work is to prove and quantify the effect of some of the characteristics of the carbon nanotubes carpets on both mechanical and thermal properties of the different kinds of CNT carpets and resulting composite materials. The two impregnation methods used, liquid way and infusion, lead to dense CNT carpets with a preserved alignment of the CNT and an homogeneous distribution of these latest within the epoxy system. The CNT volume content is evidenced as the key-parameter exacerbating the mechanical and thermal properties mainly in the longitudinal direction compared with the alignment axis of the CNTs. Moreover the mechanical and thermal conduction properties of the CNT carpets and the 1D-nanocomposites are clearly increased when the crystalline structure of the CNT is improved. The significant increasing of the properties brought by the vertically aligned CNT within these anisotropic 1D-nanocomposites compared with the only organic matrixes is promising and opens new pathways aiming to meet the latest specifications related to multifunctionnality in fields such as aeronautics and aerospace
Etude multi-échelle d'un écoulement fluide/poreux avec réaction hétérogène : application à la dépollution en textile lumineux photocatalytique by Robin Degrave( )

2 editions published in 2015 in French and held by 3 WorldCat member libraries worldwide

The photocatalysis is known as an advanced oxidation process and its use is common for the water treatment. This thesis deals with the water depollution within an original reactor integrating the UV-light photocatalytic textile. The textile is composed of parallel optical fibres located on a side of a fibrous fabric. The unity of the system is ensured by bonding points periodically distributed fixing the optical fibres to the fabric. A microtexturization treatment is applied to the optical fibres and a multitude of punctual light sources are thus created on their lateral surface. A light emission macroscopically homogeneous is provided by the connection of optical fibres to an UV lamp. The coating of catalyst, such as titanium dioxide, associated with UV irradiation generates photocatalytic activity. This thesis consists in studying phenomena which occurs within a setup containing the UV-light photocatalytic textile. In this model plane reactor, the textile is confined between two plates and a unidirectional flow parallel to optical fibres is applied. The fluid depollution results of the coupling between several mechanisms : fluid flow, transport and reaction. Numerical models are thus developed on a representative volume element of the textile (called RVE) to simulate at the microscopic scale the depollution of water containing a test molecule. This geometry is designed by taking account the structural characteristics of the photocatalytic textile. The first stage is the analysis of the hydrodynamic within the textile that combines free flow regions and porous medium flows. A preliminary experimental study allows the acquisition of data necessary to a realistic representation of the porous medium flow. Secondly, the transport is characterized by a study of the residence time distribution (RTD) within the reactor. Successive simulations using pseudo-periodic boundary conditions are performed to numerically calculate the RTD. They are validated by experimental measurements using dye tracing. Finally, the degradation of a test molecule is analysed experimentally and numerically. The numerical study presents both approaches macroscopic and microscopic. The study at the macroscopic scale allows to globally quantify the reactor performances. On the other hand, kinetic constants necessary to simulations at the microscopic scale are determined by fitting of the macroscopic model with experimental measurements. An accurate analysis is thus realized within the RVE. It points the advantages and limitations of the model reactor in terms of depollution efficiency and functioning homogeneity. Suggestions of structural improvement are proposed and especially a reactor integrating a stack of photocatalytic textiles
Etude et modélisation du comportement en fatigue de l'alliage d'Aluminium 2618 anodisé soumis à des chargements multiaxiaux by Benaïssa Malek( Book )

2 editions published in 2020 in French and held by 2 WorldCat member libraries worldwide

Les alliages d'aluminium anodisés sont largement utilisés dans la construction aéronautique en raison de leurs bonnes propriétés mécaniques, leur résistance à la corrosion et leur faible densité. Cependant, le processus d'anodisation conduit souvent à une réduction de la résistance en fatigue. De plus, les pièces sont généralement soumises à des sollicitations multiaxiales en service et il apparaît donc nécessaire d'étudier, non seulement l'effet de l'anodisation, mais également de le corréler à la nature du chargement.L'objectif de la thèse est donc d'identifier et de caractériser les différents mécanismes impliqués dans l'effet de l'anodisation de l'alliage 2618-T851 sur sa tenue en fatigue et de déterminer l'impact de la nature du chargement. Dans un premier temps, des essais de fatigue uniaxiale en traction et torsion ont été effectués sur des éprouvettes à l'état brut présentant différentes rugosités de surface et sous différents rapports de contrainte. Il a été constaté que la rugosité de surface n'avait aucun effet quelle que soit la nature du chargement. En revanche, une contrainte moyenne normale ou de cisaillement non nulle réduit la durée de vie en fatigue. Les essais effectués sur les éprouvettes décapées, anodisées, imprégnées et finalement colmatées ont montré qu'en traction, l'abattement de la durée de vie est dû principalement à l'étape d'oxydation anodique. Par contre, en torsion, la tenue en fatigue de l'alliage n'est pas sensible au processus d'anodisation.Ensuite, le matériau a été étudié en fatigue multiaxiale, en traction-torsion sous différents rapports de contrainte et différents angles de déphasage à l'état usiné et anodisé. Nous avons constaté que l'anodisation a un effet néfaste comme dans le cas de la traction pure et que le matériau n'est pas sensible au déphasage quel que soit le rapport d'amplitude de contrainte. L'alliage a été étudié sous chargements multiaxiaux intégrant la pression interne pour analyser le comportement en fatigue de l'alliage sous ce type de chargement. L'analyse des faciès de rupture a montré qu'en général, nous retrouvons un amorçage de fissures à partir de particules intermétalliques Al9FeNi avec la présence d'un site unique pour l'alliage à l'état brut d'usinage et un amorçage à partir de la couche d'oxyde avec la présence de multi-sites dans le cas des éprouvettes anodisées.Concernant les prévisions de la durée de vie, nous avons utilisé différentes approches de type plan critique (Morel, Fatemi-Socie, Findley, Kluger et Macha) pour prédire les durées de vie sous différentes combinaisons de chargement. Finalement, un modèle inspiré du modèle de Kluger a été proposé
Extrusion assistée par CO2 supercritique appliquée au moussage d'un biopolymère, le poly(acide lactique), seul ou en mélange à de l'amidon : étude expérimentale et modélisation by Margot Chauvet( )

2 editions published in 2017 in French and held by 2 WorldCat member libraries worldwide

Nowadays, foams of thermoplastic polymers (or expanded plastics) are used in many applications of day life. They can be found in insulation, shock absorption, packaging or biomedical specific applications. One of the major drawbacks lies in the use of synthetic materials. To overcome this problem, the use of biobased and biodegradable polymers represents an interesting alternative.The aim of this work is to elaborate foams with the biopolymer poly(lactic acid), PLA. To manufacture such a porous material, the process of extrusion assisted by supercritical CO2 is an efficient solution. Indeed, depending on operating conditions and CO2 solubility in the biopolymer, its injection in the barrel of an extruder modifies the rheological behaviour of the polymer. It also plays the role of an expansion agent during the depressurization undergone by the polymer while flowing through the die. The main advantages in comparison with traditional methods, are that, here, the physical blowing agent (CO2) is not toxic, environmentally friendly while leaving no residue in the final product. This process shows great potential for the creation of porous materials with different morphologies. Foams with porosity as high as 95 % have been produced. For such a high porosity, two structures have been observed: foams with a large radial expansion with only open cells of large size, or foams with a large longitudinal expansion with low content of open cell having small size. A parametric study (T, P, CO2 %) was conducted with PLA both pure and mixed with starch in various forms. The latter makes it possible to improve the biodegradability of the PLA and to modify its behaviour during the foaming. Modelling of the process could allow a better understanding. A model based on the coupling between the polymer flow in the die with the nucleation and growth phenomena, has been developed. It has been validated by comparison with the experimental results previously obtained
Sustainable design of oilseed-based biofuel supply chains : the case of Jatropha in Burkina Faso by Arnaud Chapuis( Book )

2 editions published in 2014 in French and English and held by 2 WorldCat member libraries worldwide

The development of biofuel production in Burkina Faso, raises high expectations regarding the development of rural energy access and the substitution of imported fossil fuels. Several initiatives for biofuel production from Jatropha oilseeds were launched in recent year by NGOs and private operators.The government is planning to define a policy framework to support the development of this sector. To this end, the potential benefits from this activity needs to be carefully investigated in regard to sustainable development objectives.The goal of this work was to investigate these opportunities by determining the technical possibilities regarding the context and in what conditions and to what extent they can contribute to sustainable development objectives. The approach was based on the modelling and simulation of production processes coupled with environmental and economic assessment tools. Specific experiments were also led whenever data were not available, as for the determination of the oil yield of a screw press. Economic efficiency was assessed using value chain analysis, which consists in calculating the value added generated by the different activities involved in a supply chain, and the distribution of this value in the form of income to the employees, the supply chain players, the state and the banking institutions. Environmental impacts, including greenhouse gas emissions and fossil energy consumption, are evaluated using a partial life-cycle assessment. The production of three different final products was investigated, i.e. straight vegetable oil (SVO), refined oil aimed to be used for stationary applications (power generation, shaft power, pumping...) and biodiesel dedicated to transportation. The analysis of individual processes allowed to identify the most sensitive parameters at a local level. As a general trend for all processes, the price of feedstock dramatically affects the production cost. For SVO production, the oil recovery and the seeds oil content are of paramount importance. The economic performances of the refining and transesterification processes are largely conditioned by the processing capacity, due to economies of scale, and to a lesser extent by the solution employed for energy supply. In the case of biodiesel production, the price of methanol is also a crucial factor. The developed assessment method was applied to several prospective biofuel supply chains, all relying on the production of Jatropha seeds by smallholders. The results have shown that the method can bring crucial information to policy makers. Based on a seed market price of 100 FCFA/kg, any type of biofuel can be produced in a cost effective way. In some cases, the implementation of advanced technologies for energy supply and by-product valorisation is needed to reach the required production cost. This could also be a solution to increase the price of seeds so as to provide higher incomes to farmers. The production of refined oil for power generation appears to be rather expensive relatively to the target, which imposes large processing scales. Supply chains involving a biodiesel plant supplied by several decentralised SVO plants constitute a solution for addressing at the same time rural energy access and the substitution of fossil fuels. Then the income perceived by the State is directly determined by the value and the profits generated by biofuel producers. Eventually, the environmental impacts related to seed processing, in terms of GHG emissions and fossil energy consumption, is relatively low especially when energy requirements are supplied from a renewable resource. By contrast, the impacts of biodiesel production are systematically impaired by the use of methanol of fossil origin in the process
Electro-hydro-dynamique pour les systèmes diphasiques capillaires : étude des interactions entre un champ électrique et un fluide diélectrique pouvant être sous forme liquide ou liquide-vapeur by Baptiste Blaineau( Book )

2 editions published in 2018 in French and held by 2 WorldCat member libraries worldwide

Les systèmes diphasiques à pompage capillaire sont couramment utilisés pour contrôler la température de l'électronique embarquée. Ces systèmes sont fiables et performants, mais ils présentent certaines limites associées essentiellement à la vaporisation dans le milieu poreux (limite capillaire, limite d'ébullition). Une façon d'étendre leurs performances en termes de longueur de transport de la chaleur et d'intensification des transferts serait de les coupler avec un système mécaniquement actif. Un des moyens pour réaliser cela est d'utiliser les forces électro-hydro-dynamiques (EHD) se développant dans le fluide lorsqu'on applique un champ électrique. Les travaux proposés sont une contribution à la compréhension de l'interaction entre une interface liquide-vapeur et un champ électrique afin de déterminer quels sont les mécanismes qui dans ces conditions contrôlent le pompage et le transfert de chaleur. La première partie se focalise sur l'étude expérimentale d'une interface liquide-vapeur sous un champ électrique avec ou sans flux de chaleur dans une configuration très académique (deux électrodes planes et verticales) tout en étant proche de ce qui se passe dans une cannelure de caloducs par exemple. L'objectif est d'observer, de quantifier et d'analyser les effets (forces, structures, instabilités) se développant sur l'interface. Une analyse a ensuite été menée à partir de modèles 1D et 2D. Nous avons ainsi pu vérifier que parmi l'ensemble des forces s'exerçant sur l'interface, la force diélectrophorétique est celle qui contrôle sa position et sa forme avec ou sans vaporisation. On a montré cependant qu'il existait des effets de couplage avec la conduction électrique dans le liquide pouvant sensiblement agir sur la courbure de l'interface. Enfin, les résultats en vaporisation ont confirmé que le champ électrique, en donnant des moyens de contrôle de la position et de la structure de l'interface de vaporisation, peut être effectivement mis à profit pour une intensification des transferts de chaleur proches d'une paroi chauffée. Dans un dernier volet, les travaux se sont concentrés sur la mise en mouvement d'un liquide diélectrique en mettant à profit le régime de conduction. Une étude expérimentale permettant d'étudier l'influence des différents paramètres (géométrie des électrodes, distance inter électrodes, nombre de modules) a été réalisée dans les fluides HFE-7000 et HFE-7100. Les résultats ont montré une faible reproductibilité des performances de la pompe pour ces fluides suggérant une forte sensibilité des phénomènes à l'état de surface des électrodes et aux régimes parasites d'injection de charge
Clogging dynamics of particles and bacteria in microfluidic systems mimicking microfiltration processes by Zenamarkos Bantie Sendekie( Book )

2 editions published in 2016 in English and held by 2 WorldCat member libraries worldwide

The aim of the PhD is to progress in the understanding of the fouling phenomena during filtration of soft matter (colloidal particles and bacteria) and to examine the efficiency and feasibility of microfluidic separators. These studies are realized with microfluidic devices constituted of micrometric channels having the same size range as the materials being filtered. These devices, which mimic membrane dead-end and cross-flow microfiltration processes, allow in-situ and direct microscopic observations of the fouling mechanisms. The microfluidic system is equipped with flow rate and pressure measurement devices allowing a dynamic cross analysis of the observations with the variations of permeability. Experiments have been realized for different hydrodynamic conditions (flow rate, filtration mode) and for different colloidal interactions (by varying the ionic strength) in order to analyse their interplay in the clogging mechanism by soft matter (interacting particles). The results evidenced the importance of clogs formation, fragility and sweeping out dynamics during the fouling process. These dynamic events at bottlenecks induce important permeability fluctuations. The particle-particle and particle-wall interactions also play important roles on the clogging dynamics. Three different scenarios are discussed by analogy to crowd swarming: panic scenario (0.01 mM) where repulsion between particles induce pushing effects leading to the creation of robust arches at pore entrances; herding instinct scenario (10 mM) where the attraction (in secondary minima) between particles enhances the transport in pores and delays clogging; sacrifice scenario (100 mM) where the capture efficiency is high but the aggregates formed at the wall are fragile. These analyses illustrate the importance of collective behaviour exhibited by interacting particles during fouling. The fouling phenomena by biological particles (bacteria) are analysed in terms of the streamer formation conditions and mechanisms. The streamer formation phenomena are in turn analysed by playing with the cultivation conditions (the carbon to nitrogen ratio in the substrate) in order to study the effect of extracellular polymeric substances (EPS) on the process. The results show that EPS (and hence the bacterial cultivation conditions) play crucial role in streamer formation by microorganisms under flow in constrictions. Furthermore, the presence of non-EPS producing bacterial species along with EPS producing species in a mixed culture enhances the streamer formation. On the other hand, filtration of mixed particles and bacteria suspensions show that the presence of bacteria substantially modifies the clogging dynamics. Microfluidic devices with specific configurations have also been developed for fractionation in order to maximize performances of these processes. The preliminary results with these chips in cross-flow conditions show that it is possible to limit the clogging impact by working below a critical flux; their use for continuous microparticles fractionation could be then considered
 
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Alternative Names
ED 468 (Toulouse)

Institut national polytechnique de Toulouse. École Doctorale Mécanique, énergétique, génie civil, et procédés (Toulouse)

MEGEP (Toulouse)

Université Paul Sabatier. École Doctorale Mécanique, énergétique, génie civil, et procédés (Toulouse)

Languages
French (31)

English (10)