Dissertations / Theses on the topic 'Poudres (pharmacie) – Propriétés mécaniques'
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Dupont, Anthony. "Cinétiques de transformations de produits pharmaceutiques sous broyage." Electronic Thesis or Diss., Université de Lille (2022-....), 2022. https://pepite-depot.univ-lille.fr/LIBRE/EDSMRE/2022/2022ULILR020.pdf.
The objective of this thesis is to improve the understanding of the fundamental microscopic mechanisms that govern the phase transformations induced directly in the solid state by mechanical milling. In particular, three key issues have been addressed: (i) We evaluated the influence of the milling temperature on the effective amorphization rate of a crystalline material. (ii) We determined the influence of monotropic and enantiotropic characters on the mechanisms of polymorphic transformations under milling. (iii) We have shown that the polymorphic transformations under milling are not direct but involve, on the contrary, a transient amorphization mechanism. Our strategy consisted in studying these different problems through a detailed analysis of the transformation kinetics which are the direct reflection of the physical mechanisms that govern them. For this purpose, we have studied in detail the transformation kinetics of physical states of several carefully chosen compounds. These include hydrochlorothiazide, sorbitol, glycine and their mixtures. The investigations were mainly carried out by X-ray diffraction and differential scanning calorimetry (DSC). Moreover, some experimentally demonstrated transformation mechanisms could be modelled and validated by numerical simulations. In summary, all our work indicates that, in general, the transformations under milling seem to result systematically from a competition between an amorphization mechanism due to mechanical shocks and a recrystallization mechanism whose nature depends on both the milling temperature and the crystalline specificities of the material
Blaszczyk, Franck. "Étude du comportement mécanique des pulvérulents en écoulement." Tours, 1994. http://www.theses.fr/1994TOUR4018.
Chassaigne, Jean-Christophe. "Fissuration à hautes températures du superalliage base nickel N18 élaboré par métallurgie des poudres : Etude du couplage mécanique-environnement en pointe de fissure." Paris, ENMP, 1997. http://www.theses.fr/1997ENMPA001.
Lubert, Mylène. "Aptitude à l'écoulement d'un milieu granulaire : exploitation des instabilités de cisaillement et évaluation du vieillissement." Aix-Marseille 1, 2000. http://www.theses.fr/2000AIX11033.
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.
Kryze, Jana. "Méthode d'élaboration et propriétés mécaniques de composites duralumin / fibres ou particules céramiques, obtenus par métallurgie des poudres et filage." Châtenay-Malabry, Ecole centrale de Paris, 1995. http://www.theses.fr/1995ECAP0444.
Giguère, Nicolas. "Développement de nouvelles formulations de poudres métalliques pour la fabrication de composantes de haute performance." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27211/27211.pdf.
Robert-Perron, Etienne. "Contributions à l'amélioration des propriétés mécaniques de pièces fabriquées par métallurgie des poudres ayant subi une opération d'usinage à cru." Doctoral thesis, Université Laval, 2007. http://hdl.handle.net/20.500.11794/19159.
Robert-Perron, Étienne. "Contributions à l'amélioration des propriétés mécaniques de pièces fabriquées par métallurgie des poudres ayant subi une opération d'usinage à cru." Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24635/24635.pdf.
Zouggar, Mostapha. "Effets du broyage sur les propriétés structurales et mécaniques de poudres de fer pur et sur l'activation de la nitruration." Poitiers, 2000. http://www.theses.fr/2000POIT2283.
Adamiec, Pierre. "Contribution à l'étude de la manutention des charbons fins et humides : application à l'écoulement en silos." Lille 1, 1986. http://www.theses.fr/1986LIL10166.
Guiderdoni, Christophe. "Nanocomposites nanotubes de carbonne-cuivre : élaboration des poudres, consolidation par Spark plasma sintering et études de propriétés." Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1622/.
The first objective was to study the preparation of carbon nanotubes (CNTs) - copper composite powders by two different methods: the first is to synthesize in situ the CNTs into the copper matrix. The synthesis conditions, by combustion or decomposition of the oxalate mixtures to obtain copper oxide with an oxide of cobalt, nickel or molybdenum were determined. Their selective reduction in a gas mixture H2-C2H4, to form Cu-CNT powders was studied. The second method is based on the mixture of CNTs with copper powder. For this second approach, different types of CNTs have been used. The influence of their characteristics (number of walls, carbon,. . . ) of the composites has been demonstrated. The second objective was to study the consolidation and densification by spark-plasma-sintering of Cu-CNT nanocomposites. The mechanical properties and wear of dense materials were measured
Langlois, Cyril. "Le Cuivre nanostructuré massif : élaboration par métallurgie des poudres et étude du comportement mécanique." Phd thesis, Université Paris XII Val de Marne, 2003. http://tel.archives-ouvertes.fr/tel-00007715.
Nous avons montré qu'il est possible d'obtenir un cuivre nanostructuré massif et de dimensions significatives à partir de la métallurgie des poudres nanocristallines. Les étapes de l'élaboration sont détaillées dans ce travail. Il s'agit de la synthèse des poudres nanocristallines de cuivre, leur compaction, le frittage et l'extrusion hydrostatique différentielle. La microstructure du matériau à chaque étape de l'élaboration est ici étudiée par diffraction des rayons X et microscopie électronique à balayage et en transmission. La caractérisation après extrusion montre que la déformation engendrée repose sur l'activité de dislocations.
A partir des échantillons massifs obtenus, nous avons étudié les propriétés mécaniques du matériau. En traction, il apparaît que la déformation se fait à un niveau de contrainte élevé (400 MPa) et de manière homogène sans voir apparaître de striction. L'élongation maximum obtenue est de 12 %, avec une rupture ductile, sur une éprouvette de dimensions conventionnelles. La sensibilité de la contrainte à la vitesse de déformation a été étudiée en compression. Le cuivre nanostructuré montre un comportement très dépendant de la vitesse de déformation en comparaison avec du cuivre microstructuré. Cette tendance est confirmée par des expériences de nanoindentation.
La microstructure après essai mécanique, étudiée en microscopie électronique en transmission, permet de préciser l'activité des dislocations dans le matériau. Le rôle des dislocations dans les joints de grains est prépondérant, ainsi que la présence majoritaire de sources de dislocations dans les joints de grains. Cette étude a permis l'ébauche d'un mécanisme de déformation.
Dumont, Alice. "Effet des paramètres de traitements thermiques sur la microstructure et les propriétés mécaniques d'un superalliage base nickel élaboré par métallurgie des poudres." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2013. http://pastel.archives-ouvertes.fr/pastel-00963714.
Guichard, Jean-Louis. "Élaboration et caractérisations de cermets alumine-métal à partir de poudres obtenues par mécanosynthèse." Vandoeuvre-les-Nancy, INPL, 1998. http://docnum.univ-lorraine.fr/public/INPL_T_1998_GUICHARD_J_L.pdf.
Ropars, Ludovic. "Composites à matrice titane et renforts TiB élaborés par métallurgie des poudres : cinétique de transformations des phases, formation des microstructures et propriétés mécaniques." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0327/document.
The work done in this PhD thesis aims at the understanding of, on the one hand, the structural and microstructural evolutions of a TiB reinforced titanium matrix composite during the various steps and treatments of the powder metallurgy route used to produce it, and, on the other hand, the link between the microstructures and the mechanical properties for this material. The phase transformation kinetics, in the matrix and in the reinforcement, were characterised using in situ high energy XRD, during these treatments. Microstructural analysis, using SEM, SEM-EBSD and TEM (EDX and EELS) complete the XRD analysis. The matrix phase transformation kinetics were shown to be highly impacted by the processing route (a 300°C shift toward the high temperatures is found for the ß transus temperature). This shift has been linked with an increase in interstitial elements, coming from the powder mechanical alloying and from the interstitials in the TiB2 powder used to produce the TiB. The in situ study also helped in clarifying the transformation sequence of the TiB2 into TiB-27, via the formation of the metastable phase TiB-Bf. SEM and TEM analysis allowed to get access to and discuss the morphological and spatial evolutions of the phases (matrix and borides) during the various treatments and to characterise the chemical composition of the borides. A transformation sequence has been proposed. Finally, in a last part, composite materials were elaborated and submitted to defined heat treatments. The link between the static mechanical properties and the morphological and texture evolutions in the matrix and in the borides, was discussed. Some treatments were proposed to reach optimum mechanical properties
Housaer, François. "Elaboration et caractérisation de composites Aluminium/Nanotubes de Carbone obtenus par métallurgie des poudres." Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10003/document.
Powder metallurgy routes allow the synthesis below the melting temperature of composites with notable properties. Due to the combination of the aluminum (Al) low density and the excellent mechanical properties of carbon nanotubes (CNT), Al/CNT composites might be promising materials for various fields such as aerospace and automotive. However, the improvement of mechanical properties requires the control of the microstructure and especially of grain boundaries. Indeed, high density and uniform distribution of carbon nanotubes in the matrix are necessary conditions for mechanical strengthening. A protocol was developed in order to ensure the nanotubes disentanglement and dispersion within the aluminum powder. Its high efficiency was characterized by microscopy technics and its impact on the composites mechanical properties was highlighted. The powders are sintered by two methods: hot pressing and spark plasma sintering. The study of grain boundaries highlights the influence of sintering parameters (time, temperature, technique) on the Al-CNT system reactivity. Thus, an aluminum carbides formation mechanism involving crystallization and cracking of the oxide layer at the aluminum grains surface is proposed. Finally, various parameters such as the CNT content, sintering conditions and techniques used and the prior ball milling of the composite powders are related to the improvement of the aluminum mechanical strength
Housaer, François. "Elaboration et caractérisation de composites Aluminium/Nanotubes de Carbone obtenus par métallurgie des poudres." Electronic Thesis or Diss., Lille 1, 2015. http://www.theses.fr/2015LIL10003.
Powder metallurgy routes allow the synthesis below the melting temperature of composites with notable properties. Due to the combination of the aluminum (Al) low density and the excellent mechanical properties of carbon nanotubes (CNT), Al/CNT composites might be promising materials for various fields such as aerospace and automotive. However, the improvement of mechanical properties requires the control of the microstructure and especially of grain boundaries. Indeed, high density and uniform distribution of carbon nanotubes in the matrix are necessary conditions for mechanical strengthening. A protocol was developed in order to ensure the nanotubes disentanglement and dispersion within the aluminum powder. Its high efficiency was characterized by microscopy technics and its impact on the composites mechanical properties was highlighted. The powders are sintered by two methods: hot pressing and spark plasma sintering. The study of grain boundaries highlights the influence of sintering parameters (time, temperature, technique) on the Al-CNT system reactivity. Thus, an aluminum carbides formation mechanism involving crystallization and cracking of the oxide layer at the aluminum grains surface is proposed. Finally, various parameters such as the CNT content, sintering conditions and techniques used and the prior ball milling of the composite powders are related to the improvement of the aluminum mechanical strength
Bui, Quang-Hien. "POLYCRISTAUX A GRAINS ULTRAFINS ELABORES PAR METALLURGIE DES POUDRES : MICROSTRUCTURE, PROPRIETES MECANIQUES ET MODELISATION MICROMECANIQUE." Phd thesis, Université Paris-Nord - Paris XIII, 2008. http://tel.archives-ouvertes.fr/tel-00439533.
Dutel, Guy Daniel. "Comportement mécanique et mécanismes de déformation et d'endommagement de polycristaux de nickel mono- et bi-modaux élaborés par SPS." Paris 13, 2013. http://www.theses.fr/2013PA132027.
Ultra-fine grained materials present a high mechanical resistance, but a very weak ductility. The Powder Metallurgy is then used to conceive innovative microstructures and optimize their properties. In this work, nickel samples were developed by Spark Plasma Sintering (SPS) and/or by Cold Isostatic Pressing (CIP) from blends of nano- and micrometer-sized powders. The obtained microstructures are dense and mono- or bi-modal. The volume fractions of ultrafine grains (UFG<1μm) and micrometric grains (MC>1μm) were controlled. Having stabilized the average sizes of UFG grains and MC grains, it was shown that the mechanical properties in compression and in-situ tensile tests (synchrotron) depend essentially on the UFG/MC fraction. So, the elastic limit grows with the UFG fraction. On the contrary, the ductility increases with the MC fraction. The mechanical properties were improved by varying the UFG/MC fraction. The synchrotron analyses revealed a late élasto-plastic transition for bimodal samples. It was shown in agreement with the literature, that the deformation and damage mechanisms were generally: decrease of the density of twins and Σ3 boundaries (interaction with the partial dislocations), cracking in the UFG matrix (stopped by the MC grains), interfacial decohesion which we attributed to the deformation incompatibilities between UFG matrix UFG and MC grains. Besides, the high stresses at the head of the cracks were at the origin of the mechanical twining in some UFG grains
Sadek, Céline. "Mécanismes de formation des grains et propriétés des poudres laitières associées : influence de la composition du concentré et des paramètres de séchage." Thesis, Rennes, Agrocampus Ouest, 2015. http://www.theses.fr/2015NSARB264.
Spray drying is a well-established process but certain aspects of droplet-particle transition are not yet fully understood, resulting in variability in terms of powder quality and performance. Therefore, understanding precisely how the particle is formed and how it can be controlled still remain a major challenge. This PhD project aims to break down the complexity of the drying phenomenon using an exploratory multi-scale approach. Particle formation of milk proteins (whey proteins and casein micelles) was investigated using different experimental systems (single pendant droplet, confined droplet, mono-dispersed droplets and spraying cone droplets) in controlled drying environments (drying temperature: 20°C to 190°C and relative humidity: 40% to 2%).The results showed that the drying of a single protein droplet included three distinct stages highlighted with the occurrence of specific morphological events (constant rate shrinkage, buckling instability, vacuole nucleation). According to the type of proteins, these drying stages differed in drying kinetics and droplet dynamics, leading to characteristic and reproducible particle shapes whatever the droplet configuration and the drying conditions. These different kinds of drying behaviour were related to specific skin formation conditions and different responses of the protein material to internal stress. Finally, by means of this multi-scale approach, this work highlighted the particular signature of milk proteins in a concentrated state and in general the impact of the matter in the droplet drying process
Stef, Jonathan. "Fusion Laser Selective de poudres de TA6V : microstructure et mécanismes de formation des porosités en lien avec les paramètres du procédé SLM et les propriétés structurales." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0433/document.
Selective Laser Melting (SLM) is an additive manufacturing process of metallic parts based on powder bed fusion (PBF). SLM is part of the industry 4.0 concept and is opposed to conventional manufacturing processes where the material is either subtracted, deformed or molded. From a numerical model, parts are built by material addition layer by layer. The SLM process has incontestable advantages as it offers the possibility of making small parts with complex shapes and reducing transportation costs. It also promotes mass customization and relocation of factories close to customers. However, the SLM process suffers of a lack of repeatability and control of manufactured parts which hinders its development on a larger scale. Among the possible reasons, the control of part properties is made difficult since it depends on many complex interactions between the input powders, the process parameters and microstructural features.In this work, we propose to investigate the relationships between manufacturing process parameters of Ti-6Al-4V titanium alloy parts, the mechanisms of formation of their voids, their microstructure and their structural properties. In this purpose, a parametric study was conducted to evaluate the influence of laser power, scanning speed and hatch-spacing parameters. Three energy densities were considered (50, 75 and 100J/mm3), and a rotative scanning strategy was chosen.From an original approach based on 2D fracture surface and 3D-Xray tomography analysis of parts, two mechanisms of pore formation were identified and investigated. For 50J/mm3, the spatial distribution of voids is shown to be dependent to the scanning strategy. The volume fraction and density of pores depend on the laser power and the scanning speed. For higher energy densities (75 and 100 J/mm3), two new mechanisms of pore formation were identified corresponding to over-melting and gas trapping.Concerning the microstructure, the whole characterized specimens have shown a weakly textured α’ martensitic structure. For a same energy density, prior-β grain morphology and α’ needle size were revealed to be dependent to the process parameters. Fine investigations carried out by Transmission Electron Microscopy underscored the presence of un-identified twins in literature. They are first, twins of type {01̅11} <2̅111̅>a’ or {01̅11} <21̅1̅1>’ with a rotation of 57° around the [21̅1̅0]a’ zone axis and a twinning shear of 0,542, and secondly, twins of type {011̅1}<7̅ 21 14 11>a’ or {1̅011}<11 14 1̅ 0>a’ with a rotation of 63° around the [12̅2̅1]a’ zone axis and a twinning shear of 0,963. These twins would indicate that a stress relaxation phenomenon takes place, induced by the high cooling rates and the martensitic transformation.Concerning mechanical properties, porosity affects the material ductility. Its behavior is more brittle even when the volume fraction of voids is small (<1%). 3D reconstruction of a tensile broken specimen attests a one to one relationship between the spatial distribution of pores and the crack path. Finally, pores formed by a lack of fusion and denudation are more detrimental for mechanical properties than over melting ones. This analyze is also performed by comparison with the volume fraction and the morphology of voids corresponding to each mechanism of formation
Augustins-Lecallier, Isabelle. "Conception de nouveaux superalliages MdP base nickel pour disques de turbines." Phd thesis, Paris, ENMP, 2011. https://pastel.hal.science/pastel-00710579.
In order to upgrade the SNECMA M88 engine, new specifications were issued for the material of the parts that are currently made by forging and machining N18 superalloy, including, essentially, turbine discs. This study focuses on the development of new Nickel base polycrystalline superalloys which meet these specifications, i. E. Which generally exhibit mechanical properties and microstructural stability better than that of alloy N18, in spite of a significant reduction of the γ' volume fraction. Refering to the state of the art on the specific role of each of the various alloying elements and of heat treatments on the microstructural and mechanical characteristics of the superalloys, new compositions are explored. The microstructures of these experimental alloy compositions are analysed. Tensile, creep and crack propagation tests are performed in order to compare the properties of these new alloys with those of reference, industrially used, superalloys. Among the evaluated alloys, those exhibiting a remarkable tensile and creep resistance were examined by transmission electron microscopy in order to identify the various deformation mechanisms: an interpretation of the outstanding resistance to deformation is presented
Augustins-Lecallier, Isabelle. "Conception de nouveaux superalliages MdP base nickel pour disques de turbines." Phd thesis, École Nationale Supérieure des Mines de Paris, 2011. http://pastel.archives-ouvertes.fr/pastel-00710579.
Ouabbas, Yamina. "Procédés mécaniques d'élaboration à sec de particules composites à propriétés d'usage contrôlées. Caractérisation et stabilité d'un gel de silice." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2008. http://tel.archives-ouvertes.fr/tel-00276411.
Dans ce travail trois différents dispositifs, l'Hybridizer (enrobage par impact mécanique élevé), le Cyclomix (mélangeur par cisaillement élevé) et le Turbula, ont été utilisés. Pour comparer ces techniques, un couple modèle de poudres ayant des propriétés très différentes a été alors choisi. À cette fin, une poudre de gel de silice (GS, 55 µm) hydrophile a été traitée avec de fines particules de stéarate de magnésium (StMg, 5 µm) hydrophobe dans des proportions massiques variables.
La morphologie de surface des particules de gel de silice enrobées à été examinée par la microscopie électronique à balayage environnemental (MEBE). L'utilisation de l'AFM en mode contraste de phase mode Tapping a permis de mettre en évidence la présence très localisé du StMg à la surface du gel de silice. Les forces d'adhésion entre du StMg collé à une pointe AFM et les différentes poudres, ont été mesurées en mode contact. L'effet du traitement mécanique sur l'affinité vis-à-vis de l'eau des particules de GS a été évalué par le test de la goutte d'eau posée et la DVS. La modification de la coulabilité du gel de silice après traitement a été analysée par un voluménomètre.
L'étude de la stabilité des particules de gel de silice enrobées a montré l'effet de l'humidité relative sur le vieillissement de l'enrobage. Ce phénomène est accompagné par une diminution du volume spécifique des pores du GS. Un mécanisme de diffusion du StMg depuis la surface externe des particules de GS vers la surface interne des pores est proposé.
Carabajar, Sarah. "Etude des mécanismes microscopiques d'endommagement d'un acier fritte sous sollicitations monotone et cyclique." Lyon, INSA, 1998. http://www.theses.fr/1998ISAL0017.
This work investigates the relationships between the microstructure and the microscopic damage mechanisms of sintered steel submitted to monotonic and cyclic stresses. The initial microstructure was characterized bath from phases and porosity point of views. The mechanical properties were determined. Then the chronology of the damage mechanisms under monotonic stresses was identified by in situ tensile tests in a scanning electron microscope. The pores act as crack initiation sites. Nevertheless, their noxiousness is influenced by their micro structural environment. The interfaces appear to be critical parameters because they present coarse particles of cementide. The austenitic phase seems to be interesting for the material strength. During the fatigue tests, the details of crack initiation and crack propagation were surveyed by light and scanning electron microscopy followed by fractographic analysis. The initiation occurs on non metallic inclusions near the sample surface. Then, two slow crack propagation modes were identified and their crack growth rate determined. First, the crack propagates in the I mode. Then, it forks off to follow the sintered bridges preferentially. The change of the crack propagation path was linked to the formation of secondary microcracks in the sintered bridges in front of the main crack during cycling. The interest of the austenitic nature of the sintered necks for the material life was shown. Finally, the slow propagation stage was described by a simple model based on the linear fracture mechanic taking into account the microstructural features. The differences between the monotonic and the cyclic mechanical behavior of the material were analyzed
Beaunac, Élodie. "Étude du lien entre les caractéristiques physico-chimiques des poudres et leur comportement lors des phases de transfert." Thesis, Compiègne, 2021. http://www.theses.fr/2021COMP2650.
The development of the future fast nuclear reactors is being considered with the goal of optimizing uranium resources, in particular through the multi-recycling of plutonium. These reactors are expected to save resources and reduce nuclear wastes. In France, the nuclear fuel for future sodium-cooled fast nuclear reactors is called MOX fuel (Mixed OXides). It is composed of uranium oxide UO2 and plutonium oxide PuO2 up to 35%wt. The manufacturing process should allow the use of multi-recycled plutonium, which would lead to an increase in the radiological activity of the raw materials used. This process must then minimize the generation of dust and limit equipment maintenance operations, thanks to a good flowability of powders, while obtaining pellets fulfilling the various specifications. To this end, the conditioning method is a key step of the manufacturing process in order to produce agglomerates with appropriate characteristics, which should lead to an improvement of the flowability of the initial powder. In this thesis, the impact of the conditioning method on the physical, mechanical and rheological characteristics of powders was studied in order to establish a link between physical characteristics and rheological behaviour. Also, a modelling approach (DEM) was initiated in order to simulate the rheological behaviour of powders during the transfer operations of the industrial process. Two conditioning methods were investigated to determine the conditions that improve the flowability of the same initial ground powder: one method using a V-blender and another method using a Frewitt oscillating and rotating mill. Beforehand, the establishment of a characterization methodology was necessary in order to be able to perform a maximum number of measurements with a minimum amount of powder. The conditioning method leading to the best flowability improvement was the Frewitt conditioning method with a 250 μm sieve, followed by stirring and lubrication steps. The study of the impact of this conditioning method on powders with different initial characteristics showed a certain robustness of this method. Also, a study by multiple linear regression highlighted the relative importance of the powders physical and mechanical characteristics on their rheological properties. Finally, an optimized calibration method of the simulation parameters by LHS-Krigeage-EGO was implemented
Mondet, Mathieu. "Élaboration de composites base magnésium pour des applications d’allègement de structures et de protection balistique dans le secteur des transports." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0043/document.
The present PhD thesis falls within a structure lightweighting issue in the transport field for civil and military applications. Today, the metallic structural parts in transports are mainly composed of aluminum alloys and steels. With an inferior density and a similar specific mechanical strength to these metals, the AZ91 alloy appears to be a promising alternative. Despite its precipitation strengthening, its relative low mechanical properties limit its current use as engineering material. An improvement could be reached via microstructure refinement and ceramic particle strengthening. Powder metallurgy, involving Spark Plasma Sintering (SPS), will be used as an effective way to improve the AZ91 properties using these two approaches. AZ91 alloys were produced by SPS and reinforced by SiC particles. Their mechanical properties were optimized by microstructure control. This control was carried out by adjusting the SPS processing parameters to optimize the alloy densification, its grain size and its precipitate content. The mechanical properties of the materials were evaluated via hardness testing, compression tests in quasi-static and dynamic conditions as well as quasi-static tensile tests. The tensile tests were carried out after an up-scaling of the production process from Ø30 mm cylindrical pieces to Ø80 mm pieces. In addition to the tensile tests, the up-scaling step allowed to study the repeatability of the process conditions. While the mechanical optimization of the SPS processed materials was paid on their compressive properties, their tensile properties gave information on their cohesion and ductility. In order to highlight the mechanical improvement got by microstructure refinement and particle strengthening, the SPS processed materials were compared with cast AZ91 alloys
Malaplate, Joël. "Etude du fluage à 750ʿC d'alliages Ti48 AI48Cr2Nb2 obtenus par les voies métallurgie des poudres et fonderies." Toulouse 3, 2003. http://www.theses.fr/2003TOU30060.
Song, Bo. "Nouvelles voies de fabrication d'alliages métalliques à hautes performances à partir de poudres." Phd thesis, Université de Technologie de Belfort-Montbeliard, 2014. http://tel.archives-ouvertes.fr/tel-01004824.
Tougas, Bernard. "Caractérisation de la diffusion du nickel à partir de particules nano et micrométriques prémélangées et son impact sur la microstructure des aciers au nickel utilisés en métallurgie des poudres." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29670/29670.pdf.
Lapierre-Boire, Louis-Philippe. "Impact de l'ajout de nanoparticules sur l'écoulement de mélanges de poudre à base de fer." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27117/27117.pdf.
Stein, Julien. "AA5083 aluminium alloys reinforced with multi-walled carbon nanotubes : microstructure and mechanical properties." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20002.
The overall goal of this thesis is to process new metal matrix composites reinforced by CNT with enhanced mechanical properties. The main part of this work was achieved using CVD-grown multi-walled CNT as reinforcement and a high-performance light aluminium alloy, AA5083, as the matrix. Dense and homogeneous CNT/AA5083 composites were processed by the powder metallurgy route, followed by an extrusion forming process. A homogeneous dispersion of the CNT in the composites at the micron scale appears to be a key parameter for improving the mechanical properties. This could be achieved using high energy ball milling through the mechanisms of plastic deformation and cold-welding, and was demonstrated from Raman spectroscopy cartography studies. Yield strength, ultimate tensile strength and micro-hardness of the homogeneous composites were increased by up to 55%, 61% and 33%, with respect to raw alloys processed in the same conditions, and the coefficient of thermal expansion was decreased by 10%. Optimal results were obtained with a CNT con-tent of 1.5 wt.-%. The material strengthening was principally attributed to load transfer at the CNT/matrix interface
Ramezani, Kakroodi Adel. "Production and characterization of thermoplastic elastomers based on recycled rubber." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/30327/30327.pdf.
This Ph.D. work is devoted to the production and characterization of polymer compounds based on thermoplastic matrix filled with waste rubber powder. The main applications include: (A) the production of thermoplastic elastomer (TPE) resins containing high ground tire rubber (GTR) contents (50% and higher), and (B) impact modification of thermoplastic composites using low concentrations of GTR. In the first part of the work, maleated polyethylene (MAPE) is proposed as a matrix to produce MAPE/GTR blends having excellent characteristics as thermoplastic elastomers. Then, the effects of different degradation mechanisms (weathering, thermal degradation and reprocessing) on the properties of MAPE/GTR compounds were extensively investigated to determine their potential for further recycling. Finally, the reinforcement of GTR filled TPE was investigated using different types of solid particles (wood flour and talc) for more demanding applications (mechanical characteristics). In the second part of the work, a new approach is proposed for impact modification of polypropylene based composites based on organic (hemp) and inorganic (talc and glass) reinforcements. The effective improvement of the impact properties of these composites is performed through the addition of a masterbatch based on maleated polypropylene (MAPP)/waste rubber powder (GTR or waste EPDM) containing high concentrations (70% by weight) of waste rubber.
Gilmas, Margaux. "Εndοmmagement des aciers frittés utilisés dans la cοnceptiοn autοmοbile : optimisatiοn de l'élabοratiοn et de la tenue mécanique." Caen, 2016. http://www.theses.fr/2016CAEN2017.
The goal of this PhD is to understand damage and fracture mechanisms in sinter-hardened steels for applications in automotive industry. Their martensito-bainitic structure gives them high mechanical properties in static loading such as compression or contact. However, the huge amount of surface porosity leads to anomalies in the behavior. In order to anticipate the degradation of sintered parts and to predict their durability, it is necessary to better grasp damage mechanisms leading to the deterioration of these materials. This PhD is divided into two main axes: one part is more industrial and the other more academic. All this work has provided the company Faurecia advanced scientific expertise on sintered steels used in their products. Thanks to a global structural characterization, selection criteria for sintered materials have been revealed and a characterization protocol defined. Those studies also constitute an academic support for the comprehension of the relation between microstructure and damage in tension as well as the determination of the origin of the fracture and of the strain in sintered steels
Karrad, Sahnoune. "Mélanges composites PEHD/PS/Talc : application au recyclage." Montpellier 2, 1995. http://www.theses.fr/1995MON20036.
Dupas-Langlet, Marina. "De la déliquescence au mottage des poudres cristallines : cas du chlorue de sodium." Thesis, Compiègne, 2013. http://www.theses.fr/2013COMP2094/document.
Caking or undesired agglomeration of deliquescent crystals is a recurrent phenomenon in industry, especially during transportation and storage. The variation of environmental conditions is often pointed out as a cause of the degradation of this kind of powders. More precisely, the fluctuations of ambient humidity lead to the formation of a saturated solution by deliquescence followed by the formation of solid bridges when water evaporates. Sodium chloride is chosen as a model substance in this study. The equilibrium with water vapor and the kinetics of water uptake and loss are analyzed and related to the mechanical macroscopic behavior of crystals. The contact with crystals of different nature such as sucrose highlights the phenomenon of mutual deliquescence. The model of regular solutions applied to ternary systems containing NaCl, sucrose and water allows a better understanding of deliquescence lowering. The presence of water molecules and capillary condensation at low relative humidity lead to the deliquescence of NaCl and sucrose simultaneously. Water evaporation and recrystallization of solid from such solution is compromised, especially at the solid composition of the “eutonic point”. The singular behavior at this composition which resembles to the one of a pure substance shows a partial recrystallization of the “eutonic” mixture and the formation of an amorphous phase under the experimental conditions applied. In order to avoid caking reinforcement, the study of differentanti-caking agents reveals the efficiency of magnesium stearate
Stasiak, Tomasz. "High Entropy Alloys with improved mechanical properties." Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R050.
High Entropy Alloys (HEAs) are a new type of multicomponent alloys. They contain at least five elements with the content of each between 5 and 35 at. %. The high configuration entropy, which is the source of the name of the whole family of alloys, together with other parameters, such as mixing enthalpy, atomic size difference, electronegativity difference, or valence electron concentration, stabilize a solid solution instead of complex intermetallic compounds. Promising properties and interesting microstructures focus the attention of the scientific community to HEAs.In this work, the novel Al-Cr-Fe-Mn-Mo high entropy alloy family was studied. The microstructural and chemical analyses were performed by XRD, Mössbauer spectrometry, SEM, TEM, EDX, EBSD. In the first stage, parametric approach calculations were carried out to optimize the chemical composition of the alloy. The selected compositions were prepared by mechanical alloying in different devices. The optimized conditions that ensure maximum chemical homogeneity of powder and the small contamination from balls and vial materials were chosen. In most of the powders, two bcc phases form during mechanical alloying with the lattice parameters about 3.13 Å (bcc#1) and 2.93 Å (bcc#2). The heat treatment of powder results in several phase transformations (e.g., the formation of the χ phase). The annealing at 950 °C for 1 h promotes the significant increase of volume fraction of the bcc#2 phase, while the bcc#1 and χ disappear. Nevertheless, small fractions of carbides and oxides were found. The bulk samples were fabricated by hot press sintering of the optimized mechanically alloyed powders. The conditions of consolidation were evaluated and optimized to promote the formation of the bcc phase and reduce the formation of carbides and oxides resulting from the contamination during mechanical alloying and sintering. The optimized bulk samples present a major disordered body-centered cubic phase (> 95 % of volume fraction) with a lattice parameter of 2.92 Å and a very small fraction of carbides (M6C, M23C6) and oxides (Al2O3). The bcc phase is stable after annealing at 950 °C for 10 h. Moreover, the alloy presents very high hardness up to 950 HV2N. The compression tests of the optimized bulk sample from room temperature to 800 °C reveal promising properties, especially between 600 and 700 °C. The alloy shows brittle behavior between room temperature and 400 °C. However, the alloy starts to demonstrate some degree of plasticity at 500 °C. At 600 °C, the yield strength is 1022 MPa, while strain to failure is about 22 %
Stasiak, Tomasz. "High Entropy Alloys with improved mechanical properties." Electronic Thesis or Diss., Université de Lille (2018-2021), 2020. http://www.theses.fr/2020LILUR050.
High Entropy Alloys (HEAs) are a new type of multicomponent alloys. They contain at least five elements with the content of each between 5 and 35 at. %. The high configuration entropy, which is the source of the name of the whole family of alloys, together with other parameters, such as mixing enthalpy, atomic size difference, electronegativity difference, or valence electron concentration, stabilize a solid solution instead of complex intermetallic compounds. Promising properties and interesting microstructures focus the attention of the scientific community to HEAs.In this work, the novel Al-Cr-Fe-Mn-Mo high entropy alloy family was studied. The microstructural and chemical analyses were performed by XRD, Mössbauer spectrometry, SEM, TEM, EDX, EBSD. In the first stage, parametric approach calculations were carried out to optimize the chemical composition of the alloy. The selected compositions were prepared by mechanical alloying in different devices. The optimized conditions that ensure maximum chemical homogeneity of powder and the small contamination from balls and vial materials were chosen. In most of the powders, two bcc phases form during mechanical alloying with the lattice parameters about 3.13 Å (bcc#1) and 2.93 Å (bcc#2). The heat treatment of powder results in several phase transformations (e.g., the formation of the χ phase). The annealing at 950 °C for 1 h promotes the significant increase of volume fraction of the bcc#2 phase, while the bcc#1 and χ disappear. Nevertheless, small fractions of carbides and oxides were found. The bulk samples were fabricated by hot press sintering of the optimized mechanically alloyed powders. The conditions of consolidation were evaluated and optimized to promote the formation of the bcc phase and reduce the formation of carbides and oxides resulting from the contamination during mechanical alloying and sintering. The optimized bulk samples present a major disordered body-centered cubic phase (> 95 % of volume fraction) with a lattice parameter of 2.92 Å and a very small fraction of carbides (M6C, M23C6) and oxides (Al2O3). The bcc phase is stable after annealing at 950 °C for 10 h. Moreover, the alloy presents very high hardness up to 950 HV2N. The compression tests of the optimized bulk sample from room temperature to 800 °C reveal promising properties, especially between 600 and 700 °C. The alloy shows brittle behavior between room temperature and 400 °C. However, the alloy starts to demonstrate some degree of plasticity at 500 °C. At 600 °C, the yield strength is 1022 MPa, while strain to failure is about 22 %
Vinson, Pierre. "Fusion sélective par laser de lits de poudre : Étude sur le recyclage de la poudre et détection de défauts au cours de la fabrication par imagerie thermique." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0068.
Direct and additive manufacturing regroups several new technologies that are very different from conventional manufacturing processes such as casting. Aeronautic and space industries are really interested in those new processes such as the selective laser melting of metallic powder beds know as the SLM process. This PhD thesis report will show the issues of additive manufacturing and will describe some processes. A bibliography study has been done on two aeronautical alloys used in this work: titanium alloy TA6V and nickel-based superalloy Nimonic 263. This work also presents powder characterization (granulometry, morphology chemical composition) for the gas atomized powder. Besides, study has been done on the recyclability of the TA6V powder for the SLM process, for the powder itself and the mechanical properties of parts built from recycled powder. Moreover, this works deals with a powder bed consolidation model to estimate the productivity of the process. Then, a parametric and thermal study has been done on the Nimonic 263. The coaxial system for thermal visualization is described such as the image processing algorithm used. Finally, this reports deals with the study of thermal signature of typical SLM defects
Abdelmoula, Nouha. "Comportement élasto-plastique incrémental des poudres ductiles : simulation de l'écoulement plastique par la méthode des éléments finis multi-particules." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI036/document.
This thesis is concerned with the modelling of the mechanical behaviour of ductile powders during cold compaction process. A numerical method was implemented, in which a powder sample was assimilated to an assembly of 50 meshed particles in a cubic box which was submitted to compressive loadings simulated by means of the finite element method. Each particle was meshed and assigned an elastic-plastic constitutive behaviour. Particles interacted through mechanical, frictional contact and underwent large transformation during loading.The method developped in the thesis consisted in imposing boundary conditions as displacements or forces on the bounding walls of the numerical sample. The mechanical response of the sample was averaged to obtain the equivalent response of a continuum in terms of stress and strain. Various loading paths, including loading paths that are technically not attainable by experimental means, were applied up to different values of relative densities, from low (60%) to high values (98%). Much information on the phenomenological behaviour of the numerical sample could be obtained, in relation with the morphology of deformed particles and the evolution of contact surfaces.The results were interpreted based on the concepts of classical elasto-plasticity, i.e., yield surface and flow rule. The main focus of the study was the analysis of incremental plastic flow and the existence of a plastic potential. Results showed that the flow rule postulate, based in the plastic potential, could be considered as valid for stress states relatively far from the loading point. In the vicinity of the loading point, the direction of the plastic strain increment vector ceases to be unique. This behaviour, which is an original feature of ductile powders mechanical behaviour, was attributed to the anisotropic strain-hardening processes at stake, related to the anisotropic formation of contact surfaces between particles. The drop in mechanical properties related to dilatancy was also studied
Lê, Van Nha Phuong. "Influence des propriétés physicochimiques du principe actif et du transporteur sur la performance aérodynamique des mélanges de poudre pour inhalation." Phd thesis, Université du Droit et de la Santé - Lille II, 2011. http://tel.archives-ouvertes.fr/tel-00647318.
Behloul, Mouloud. "Analyse et modélisation du comportement d'un matériau à matrice cimentaire fibrée à ultra hautes performances : bétons de poudres réactives, du matériau à la structure." Cachan, Ecole normale supérieure, 1996. http://www.theses.fr/1996DENS0026.
Royer, Alexandre. "Etude, caractérisations et développement de mélanges de polymères biosourcés chargés de poudre d'Inconel 718 pour l'élaboration de composants et micro-composants via moulage par injection de poudres métalliques." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2058/document.
The works done during this PhD focuses on the study of the thermo-physical behavior of bio sourced polymer blends loaded with Inconel 718 powder (feedstock) to be shaped by the Metal Injection Molding process (MIM). First, a review of the researches related to the MIM process was conducted to identify innovative materials and processes that can improve the MIM process. Thus, the use of polyethylene glycol (PEG), selected for its properties of solubility in water, and bio sourced polymers, in order to reduce the environmental impact, were selected. The bio sourced polymers have been selected in accordance with the conditions of the injection molding process, and the choice was made to use polylactic acid (PLA) and polyhydroalkanoates (PHA and PHBV). Similarly, the supercritical CO2 as solvent was chosen to reduce the time of binder removal as well as increasing the quality of components produced. Thermo-physical, mechanical and rheological characterizations were made to determine the behavior of the different feedstock formulations. The results showed a degradation of the PEG and of the stearic acid under the conditions of use of the biopolymers, during the mixing and the injection stages. The use of feedstock made of bio sourced polymers have improved the homogeneity of the injected components, but they have generated defects during the debinding step. These defects have been eliminated by the use of CO2 in the supercritical state as solvent of the PEG. This method has significantly decrease the time of binder removal and improved the quality of the final components. Finally, densified components have the mechanical properties corresponding to Inconel 718
Simondon, Esther. "Etude de l’élaboration d’aciers renforcés par dispersion d’oxydes par procédé alternatif de mécanosynthèse." Thesis, Rennes, INSA, 2018. http://www.theses.fr/2018ISAR0023/document.
This study concerns the development of an innovative manufacturing process for oxidedispersion strengthened steel (hereafter referred to as “ODS”) by mechanosynthesis. As part of materials development for Sodium-cooled Fast Reactors (SFR), the aim is to prevent the growth of undesirable micrometric precipitates which can drastically degrade steel’s mechanical properties. This new process introduces Y2Ti2O7 pyrochlore oxide nanoparticles directly into Fe-Cr metallic powder through mechanical milling. To achieve this, a process has been set up to synthesize Y2Ti2O7 pyrochlore oxides via mechanical alloying of nanosized Y2O3 and TiO2 powders. Optimization of the milling parameters enabled the production of a pure nanostructured powder of the desired nature. Thereafter, the innovative ODS steel manufacturing process was validated on a small and then semiindustrial scale. This new process was used to study the impact of milling parameters and chemical composition on the produced material’s features and enabled the establishment of a link between milling conditions, microstructure and mechanical properties. This study first enables the validation of the method of introducing precipitates in the form of Y2Ti2O7 oxides as an efficient way to obtain competitive ODS steel. Moreover, it reveals the importance of the features of the manufacturing process, particularly milling conditions, on the microstructure and mechanical properties of ODS steel. The results reveal promising perspectives concerning the features of ODS steel manufacturing
Sow, Mourtada Aly. "Alliages à Haute Entropie (AHE) pour revêtements hautes performances." Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR026.
This thesis aims to develop high performance coatings from high entropy alloys powders (HEA) and to characterize them. This work is divided in two parts. The first part consists in the synthesis of HEA powders for a family of alloy elements Al, Cr, Fe, Mn and Mo by mechanical alloying.These powders were characterized by XRD, SEM and Mössbauer spectrometry. These powders have a CC1 and CC2 type crystal structure. The heat treatment of the powders (500, 650, 800 and 950 °C) allowed to obtain a structural stability at 650 °C/ 1h, at 800 °C/ 1h and 950°C/ 1h and 4h, a structural evolution of the powders was noticed. The CC1 phase disappears in favor of the CC2 phase and the M23C6 et M6C type carbides. At the result of these characterizations, the chemical composition 19Al-22Cr-34Fe-19Mn-6Mo powder was preserved and produced in suffering quantities by mechanical synthesis (powder A) and by mixing (powder B).In the second part of this work, thick and thin HEA coatings were developed by laser fusion and magnetron sputtering respectively from A and B powders. The thick laser-melted coatings were deposited on steel substrate. The structure and microstructure of the deposits were carefully characterized by XRD, SEM, EDS, EBSD and TEM. The results of these characterizations revealed that the thick deposits are chemically heterogeneous. Moreover, these coatings showed different structures and microstructures of solidification depending on the deposition conditions and the powders (A or B) pre-deposited to realize these coatings.The HEA thin film were deposited on silicon wafer and steel substrate. The deposition conditions of the thin films were optimized and the chemical composition was controlled. The heat treatments of the thin films revealed good structural and microstructural stability up to 800 °C/ 72h. Corrosion resistance, mechanical properties and tribological performances were evaluated
Zouaghi, Ala. "Étude de la compaction isostatique à chaud de l'acier inox 316L : Modélisation numérique à l'échelle mésoscopique et caractérisation expérimentale." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2013. http://pastel.archives-ouvertes.fr/pastel-00823612.
Florez, Parra Daniela Carolina. "Effects of the presence of recycled tire powders on the kinetics of the radical polymerization of styrene and the properties of the resulting materials." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0347.
Recycling of end-of-life tire-derived materials is considered a sustainable approach to managing these wastes. The rubber phase of these tires is considered as a valuable source because it consists of a sulfur-crosslinked reinforced elastomer phase which displays interesting mechanical properties such as high extensibility and elasticity. One of the alternatives for used tire rubber recycling consists in grinding it into fine powders, commercially called ground tire rubber or GTR. The latter can be dispersed in thermoplastic polymers in order to improve some of their properties such as impact strength. This work aims to use GTR as a reinforcing agent to toughen brittle polymers such as polystyrene (PS). It is composed of three parts. In the first part, the effect of the presence of GTR on the kinetics of the free-radical polymerization of styrene is studied by DSC. During the polymerization of styrene in the presence of GTR, styrene is partly homopolymerized, leading to free PS, and partly grafted onto GTR, leading to PS grafted onto GTR. Benzoyl peroxide and 2,2-azobis(2-methylbutyronitrile) are used as free radical initiators. In general, the presence of GTR shows a negative effect on the ultimate monomer conversion to polymer. Moreover, it may have a positive or negative impact on the rate of polymerization. These effects can be more or less pronounced, depending on the type of initiator used. In the second part of the work, a mechanistic model is developed to describe the free-radical polymerization of pure styrene in a batch reactor. The model allows predicting the evolution of the total monomer conversion and that of the average molecular weight of PS. The validity of the model is demonstrated via comparison with experimental data generated through a series of DSC analyses as well as pilot-scale reactor runs. Subsequently, the same model is modified to take into account the reactions occurring in the presence of GTR. The third part of the work addresses the development of a new methodology combining two processes to prepare GTR toughened PS. These processes involve the free-radical polymerization of styrene in the presence of GTR and compounding of the resulting product in a twin-screw extruder. The grafting of styrene onto GTR ensures good interfacial adhesion between PS and GTR and compounding favors fine dispersion of GTR in the PS matrix. Results show that the notched Charpy impact strength of neat PS can be increased by a factor of 2 by adding 50 wt% of GTR. Moreover, a PS/GTR blend containing 70 wt% of GTR displays a performance similar to that of a thermoplastic elastomer vulcanizate (TPV) and its strain at break can reach 120%
Delcuse-Robert, Laura. "Processing effects on the structure and behavior of Nickel based alloys produced by additive manufacturing." Electronic Thesis or Diss., Université de Lorraine, 2021. https://docnum.univ-lorraine.fr/public/DDOC_T_2021_0355_DELCUSE.pdf.
Regarding its high strength at high temperature, Inconel 718 is widely used in aerospace field. With additive manufacturing, novel structure such as auxetic structure should be produced in Inconel 718 and offered new opportunities in a wide range of industrial application. Under impact loading, the high energy absorption capacity of auxetic material allows new possibilities mainly on safety issues for transport vehicles. The current work is developed through this problematic. First, the geometrical parameters of a re-entrant honeycomb structure were optimised by applying a Taguchi method and a parametrical study on computational modelling. The influence of the laser powder bed fusion parameters (L-PBF) were also tackled on thin-walled cellular structures in Inconel 718. The building direction and the laser energy density were varying to determine their effect on the porosity and print accuracy on thin strut. Then, the mechanical behaviour of the optimised re-entrant honeycomb structures was studied under tension and compression loading to identify the kinetic of deformation of the structure. To reproduce this mechanical behaviour, the compression behaviour of the Inconel 718 printed into horizontal (XY) and vertical (ZX) building direction was investigated using quasi-static and dynamic strain rates, between 10-3 s-1 and 2500 s-1. A Johnson-Cook model was determined considering the effect of the building direction on the mechanical properties. The anisotropy of the printed Inconel 718 depends on the building direction and was revealed by a microstructural study. By using EBSD orientation map and BSE micrographs, it was found that the horizontal building direction (XY) mainly provided equiaxed grain as compared to columnar grain for vertical building direction (ZX). In addition, a microstructure gradient was observed for both building directions from the border to the volume, divided into three zones (i) border, (ii) transition and (iii) centre. According to the microstructural analysis, a novel modelling approach on the yield stress was developed based on the grain size of the Inconel 718. A numerical model of the auxetic structure was developed using Abaqus software, under dynamic compression loading. The behaviour law of the printed Inconel 718 is then validated by this model, reproducing the mechanical behaviour of the auxetic structure at the macroscopic scale
Chakravarty, Somik. "Mechanical properties of cohesionless and cohesive bulk solids : transition from non-cohesive to cohesive powders." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2423.
Handling and processing of granular material release fine solid dust particles, which in an occupational setting, can severely affect worker health & safety and the overall plant operation. Dustiness or the ability of a material to release dust particles depends on several material and process parameters and is usually measured by lab-scale dustiness testers. Dustiness tests remain mostly experimental studies and lack reliable predictive ability due to limited understanding of the dust generation mechanisms and the complex interactions between the particles, wall and fluid, occurring simultaneously during dust generation. In the framework of EU ITN project T-MAPPP, this thesis uses an experimental approach to understand the dust generation mechanisms by studying: a) the effects of key bulk and particle properties on powder dustiness; b) the nature and magnitude of inter-particle, particle-wall and particle-fluid interactions; c) the evolution of dustiness and generation mechanisms for long duration powder applications. The results indicate that the dust generation mechanisms differ based on particle size and size distribution of the powder. For the given test samples and experimental conditions, the differences in powder dustiness and dust emission patterns can be characterized by three different groups of powders; powders containing fine cohesive particles, bi-modal (consisting of fine and large particles) powders and lastly, powders consisting of only large particles. While bulk cohesion, especially that stemming from van der Waals forces (measured using shear testers) determines the level of dustiness for the fine powders (in such a way that higher bulk cohesion leads to lower dustiness), both the fraction of fine particles and cohesion determine the dustiness of bi-modal powders. The large particles can emit dust only through attrition of the primary particles into smaller aerosolizable fine particles. Analysis of a traced particle motion inside a cylindrical tube agitated by a vortex shaker dustiness tester shows the cyclic nature of the particle motion. The motion (position and velocity) is symmetric and isotropic in the horizontal plane with lowest radial velocities close to the tube centre and highest at the boundary wall of the test tube. The particles tend to rise up slowly in the middle of the tube while descending rapidly close to the wall. The highest values of the velocity are found at the highest heights and close to the wall of the test tube, where the population densities are lowest. Increasing particle size and vortex rotation speeds tends to increase particle velocity whereas increase in powder mass leads to a decrease in particle velocity for rotation speeds up to 1500 rpm. For the given samples (silicon carbide, alumina and acetylene coke) and the experimental conditions, the initial dustiness is determined by the fraction of fine respirable particles present in the powder but the long-term dust generation patterns and levels are influenced by the material attrition behaviour. Dust is generated by the fragmentation and/or abrasion of primary particles, which may lead to the production and emission of fine daughter particles as dust. The samples with large irregularly shaped particles are likely to show high dustiness by shedding angular corners through inter-particle and particle-wall collisions, thus becoming more spherical in shape. On the contrary, the smaller particles are more resistant to abrasion and generate relatively less dust. While the vortex shaker dustiness tests show similar trends as an attrition tester, our study using alumina and acetylene coke indicate that the results are not interchangeable. Results from this thesis help understand the influence of powder and process parameters which may be manipulated to reduce dust generation. Furthermore, experimental results can be used to develop and validate numerical models to predict dustiness