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Simulation du contrôle de la fréquence des transducteurs dans les liquides en présence de cavitation
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A Fatigue Damage Propagation Model Based on Locally Periodic Micro-crack Growth
No full textInternational audienceThis paper develops a new micro-mechanical damage model for fatigue crack propagation in tensile (Mode I) cyclic loading. The double-scale fatigue damage model is entirely obtained through small-scale yielding descriptions of micro-crack propagation. Based on the Paris fatigue crack growth law, the stress intensity factor range is expressed thanks to an appropriate micro-mechanical energy release rate analysis coupled with asymptotic homogenization developments. The macroscopic fatigue crack evolution law is established. Numerical simulations are presented. The reliability of the model to reproduce stress-strain shielding is demonstrated. The influence of the microstructural length on fatigue damage evolution is illustrated. The numerical results are compared with fatigue crack propagation tests performed on Ti-6Al-4V titanium fashioned by additive layer manufacturing (ALM). Through the calibration process, the model agrees with the experimental results
Évaluation de l'impact du broyage à sec de molécules hydrophobes sur les propriétés biopharmaceutiques et pharmacocinétiques
No full textThe solubility and dissolution kinetics of pharmaceutical molecules are the two main factors limiting their bioavailability. According to the biopharmaceutical classification system, class II compounds are renowned for their low solubility in aqueous media. There are many strategies to overcome this disadvantage and improve the bioavailability of class II molecules. This thesis project focuses on the use of a top-down approach, i.e., particle size reduction through the application of dry milling and co-milling techniques, to overcome the obstacles restricting bioavailability. This PhD thesis is organised in two parts. The first part, which was carried out at the RAPSODEE Laboratory at IMT Mines of Albi, concerns the evaluation of the impact of dry grinding and co-grinding on model molecules. For this purpose, several characterization techniques were set up in order to evaluate the effect of the milling process on the physico-chemical properties (PSD, MEB) the crystallinity of the powders (DRX, DSC), their surface properties (FTIR, DVS) and the biopharmaceutical properties (solubility, dissolution kinetics) of the actives pharmaceutical ingredients selected. Thus, in order to obtain a size reduction of particle, two different ball mills were used : a vibratory ball mill, the Pulverisette 0® and an oscillatory ball mill, the CryoMill®. Finally, in a second part, specific approaches, in collaboration with the UMR 454 MEDIS Laboratory of Clermont-Ferrand, were employed in order to characterize the dissolution kinetics of the particles and to allow the evaluation of the improvement of the bioavailability, with the support of in vitro cell culture models using Caco-2 cells.La solubilité et la cinétique de dissolution des molécules pharmaceutiques sont les deux facteurs principaux limitant la biodisponibilité de ces dernières. En effet, les composés appartenant à la classe II, selon le système de classification biopharmaceutique, sont connus pour leur faible solubilité en milieux aqueux. Il existe de nombreuses stratégies qui ont pour but de contourner cet inconvénient et permettre d’améliorer la biodisponibilité des molécules de classe II. Ce projet de thèse s’intéresse à l’utilisation d’une approche Top-down à savoir, la réduction de la taille des particules par des techniques de broyage et co-broyage à sec, pour permettre de surmonter les obstacles limitant la biodisponibilité. Cette thèse se divise en deux parties. Une première partie, réalisée au Laboratoire RAPSODEE à l’IMT Mines d’Albi, concerne l’évaluation de l’impact du broyage et du co-broyage à sec sur les molécules modèles. Pour cela de plusieurs techniques de caractérisations ont été mises en place en vue d’évaluer l’effet du processus de broyages sur la cristallinité des poudres (DRX, DSC), leurs propriétés de surfaces (FTIR, DVS) et les propriétés biopharmaceutiques (solubilité, cinétique de dissolution) des actifs choisis. Ainsi, dans le but d’obtenir une réduction de tailles des particules, deux broyeurs à billes différents ont été utilisés. Un broyeur à bille vibrant la Pulverisette 0® et un broyeur à bille oscillant le CryoMill®. Enfin, dans une seconde partie, des approches spécifiques, en collaboration avec le Laboratoire UMR 454 MEDIS de Clermont-Ferrand, ont été utilisées afin de caractériser la cinétique de dissolution des particules et permettre l’évaluation de l'amélioration de la biodisponibilité, à l'aide de modèles de culture cellulaire in vitro en utilisant des cellules Caco-2
Étude des mécanismes de plasticité lors de la mise en forme de l'alliage de titane Ti-6Al-4V : influence de la microstructure initiale et des conditions de sollicitations thermomécaniques
No full textThe aim of this thesis is to better understand the influence of temperature, strain rate and initial microstructure on the mechanisms involved during hot forming of Ti-6Al-4V titanium alloy sheets. To achieve this, two initial microstructures with different alpha grain sizes (2 µm-FG and 0,4 µm-UFG) were tested in tension at different temperatures (T=650°C, 750°C et 920°C) and strain rates (10-2 s-1, 2x10-3 s-1 and 10-4 s-1). The microstructural evolutions (fraction, size, morphology and preferential orientation of phases, subgrains) were studied for different deformation levels by complementary microstructure characterisation techniques (SEM and image analysis, EBSD, X-ray and synchrotron diffraction). In addition, original high-temperature tensile tests combined with high-energy synchrotron diffraction (PETRA III-Hamburg) made it possible to monitor the in-situ evolution of crystallographic parameters. Deformation mechanisms are thus proposed and discussed as a function of the temperature, the strain rate and the initial microstructure. For the FG microstructure a condition of 750°C 10-2 s-1 favours the intragranular dislocations motion in alpha. A decrease of the strain rate allows an additional contribution from GBS which seems to be accommodated by the dislocations motion in beta. With increasing the temperature, significant changes of the phase fraction and distribution related to the alpha-beta phase transformation induce the activation of rather diffusive mechanisms, especially at low strain rate. Moreover, the use of an initial ultrafine grained microstructure is a major advantage for SPF forming, due to microstructural modifications induced at the beginning of the deformation (globularization) which lead to a large number of beneficial interfaces for the contribution of intergranular mechanisms (GBS). Thus, the UFG microstructure favours a superplastic behaviour at lower temperatures and higher stain rates. All these investigations have thus provided new understanding elements of the hot and superplastic behaviours.L'objectif de ce travail de thèse est de mieux comprendre l'influence de la température, de la vitesse de déformation et de la microstructure initiale sur les mécanismes de déformation mis en jeu, lors de la mise en forme à chaud de tôles d'un alliage de titane Ti-6Al-4V. Pour y parvenir, deux états microstructuraux, présentant des tailles de grains alpha différentes (2 µm-FG et 0,4 µm-UFG), ont été sollicités en traction à différentes températures (T=650°C, 750°C et 920°C) et vitesses de déformation (10-2 s-1, 2x10-3 s-1 et 10-4 s-1). Les évolutions microstructurales (fraction de phase, taille et morphologie des phases, sous-structure granulaire, orientation cristallographique des phases) ont été étudiées, à l’issue de différents taux de déformation, par des outils complémentaires de caractérisation (MEB et analyse d’image, EBSD, diffraction des rayons X et synchrotron). De plus, des essais originaux de traction en température, combinés à de la diffraction synchrotron haute énergie (PETRA III-Hambourg), ont permis de suivre in-situ l’évolution de plusieurs grandeurs cristallographiques. Des mécanismes de déformation sont ainsi proposés et discutés en fonction de la température, de la vitesse de déformation et de la microstructure initiale. Pour la microstructure FG déformée en traction à 750°C à une vitesse de déformation de 10-2 s-1, le mouvement intragranulaire de dislocations dans la phase alpha est favorisé. Une diminution de la vitesse de déformation permet une contribution additionnelle du glissement aux joints de grains probablement accommodé par le mouvement de dislocations dans la phase beta. Avec l’augmentation de la température, d’importantes modifications de fraction et de répartition spatiale des phases liées à la transformation de phases alpha-beta induisent l’activation de mécanismes majoritairement diffusifs en particulier pour une faible vitesse de déformation. Par ailleurs, l’utilisation d’une microstructure initialement ultra-fine et hétérogène présente un atout majeur pour la mise en forme SPF, en raison des modifications microstructurales induites en début d’essai (globularisation) qui conduisent à un nombre important d'interfaces bénéfiques pour la contribution de mécanismes intergranulaires (GBS). Ainsi, la microstructure UFG favorise un comportement de type superplastique à plus basse température et pour des vitesses de déformation plus importantes. L’ensemble des investigations a ainsi permis d'apporter des éléments nouveaux pour la compréhension des mécanismes de déformation contrôlant le comportement à chaud et superplastique
Jet impingement cooling using fluidic oscillators: an experimental study
No full textInternational audienceA growing portion of the thermal load on board airplanes is due to densely packed electronic systems. This increased thermal load along with constraints on weight and volume have made simple and reliable cooling solutions an urgent need in the aerospace industry. There is a wealth of cooling solutions available in order to meet these demands, the simplest and most adaptable of which is probably jet impingement cooling. In this study, fluidic oscillators capable of producing pulsating jets were used to cool a heated surface and were then compared to equivalent steady jets. Although pulsating jets can be produced using a number of devices, fluidic oscillators offer the advantage of not having any moving parts. These oscillators are sustained by a self-induced internal flow instability and can function at different scales. Although the major part of this work is based on prototypes that produce jets with sub-millimetric widths, designs at one tenth that scale, i.e. with an exit slot width of 50 µm, are also presented. Reynolds numbers ranging from Re D = 3500 to 5250 and jet-to-plate spacing from 1 D to 10 D were studied (where D is the initial width of the jet). The Nusselt number distribution is found for each case and a comparison is made between the performance of equivalent steady and pulsating jets based on the average Nusselt number
Multi-scale characterization of material and surface integrity of Inconel 718 when milling by Abrasive Water Jet process: Context of repair application
No full textInternational audienceInconel 718 (IN718) is a precipitation hardened nickel-base super-alloy exhibiting poor machinability and used in the hot section of aircraft engines. These components are subjected to severe thermo-mechanical loads in a highly corrosive environment, limiting their service life due to cracks and wear. Due to their high added-value, repair of damaged IN718 components is an interesting alternative instead their replacement. Repair process involves material removal of the damaged zone and subsequent cavity refill. Nevertheless, material removal of IN718 by conventional methods is a challenging task. Abrasive Water Jet (AWJ), a non-conventional machining process, offers a potential alternative to mitigate IN718 machining problems. However, research on the impact of AWJ process parameters during IN718 milling on the surface and material integrity is limited in the literature. Furthermore, in repair context, no study proposes AWJ machining as material removal process. The present work focuses on a multi-scale characterization of the influence of AWJ process parameters (pressure, traverse speed, step-over distance and abrasive size) on surface roughness, depth of cut, abrasive embedment and residual stress, during milling of untreated IN718. Surface integrity characterization on the milled surfaces was conducted through 3D optical microscopy, profilometry and SEM techniques. Residual stress measurements were performed in longitudinal and transverse directions with respect to the machining path using XRD technique. The results showed that all milled surfaces presented abrasive embedment and a compressive residual stress state with similar values in both directions. Up to 15% of the area of a milled surface consisted of abrasive embedment. The tool path has not influenced the residual stresses. Furthermore, surface roughness is dependent on pressure and traverse speed; depth of cut is influenced by pressure, traverse speed and grit size; abrasive embedment depends on pressure, step-over distance and grit size; whilst, residual stresses are influenced by traverse speed and grit size
Towards a Collaborative and Open Supply Chain Management Operating Services Platform
No full textPart 16: Sentient Immersive Response NetworkInternational audienceSupply Chain (SC) uncertainty perspectives must now be translated into practice. SC entities must accept crises and catastrophes as normal situations and increase significantly their culture of SC risk management. They should adapt their decision-support systems to be able considering disruptions as regular inputs, whether small, large or huge. Collaboration should not be limited to few entities of a SC, but to the whole SC. Concrete tools allowing entities to share vital information to give visibility, ensure synchronization of the material flows, align management of emergencies and use of critical resources must be developed and used. That is the purpose of this paper. Practically, aframework for SC risk and opportunity management and a Collaborative and Open Supply Chain Management Operating Services (COSMOS) platform are presented. An illustrative case is developed to highlight the potential benefits of the proposal on one service example
PLA-based biocomposites foaming by supercritical CO2 assisted batch process
No full textInternational audienceIn many industrial fields, the development of porous and light polymer composite structure is of great interest. These structures may have several advantages compared to a massive solid of the same chemical nature, such as better mechanical properties, cushioning, insulation, sound and heat absorption. As an example, foams are used in the sport, pharmaceutical, aeronautic and packaging industries. For these applications, petroleum based thermoplastics are widely used as polymer matrix, but, due to the shortage of fossil resources and the rise of environmental concerns, biopolymers (bio-based, bio-degradable and/or bio-compatible polymer) are more and more used.There are two main routes to produce biopolymer foams depending on the blowing agent used, which can be either chemical (CBA) or physical (PBA). CBA are able to release a gas upon thermal decomposition, but they have some drawbacks, among which the necessity of high process temperatures, the solid residues on the foam and their toxicity. PBA appear as an alternative to these chemical agents, supercritical CO2 and N2 being the most used.Batch foaming of polymers is a process which can be carried out in an autoclave. The samples are saturated in a pressure vessel a certain time, and their foaming is achieved by inducing an instability into the system. Pressurised gas solubility in polymers increases with pressure but decreases with temperature. Therefore, in the batch foaming process, the instability can be induced by a sudden drop in pressure (pressure quenching) or by a raise in temperature thus causing polymer foaming.This foaming technology has been largely used for different polymers such as polystyrene [2], polycaprolactone [3], polyethylene/polypropylene [4] and, polyethylene terephthalate [5]; among others. This work is focused on the foaming of PLA-based biocomposites using (ligno-)cellulosic fibres by supercritical CO2 assisted batch process by pressure quenching, the study of the operating conditions, the influence of the nature of the fibres and their characteristics on the porosity and morphology of the obtained foams
Foaming of PLA-based Biocomposites by Supercritical CO2 Assisted Batch Process : Effect of Processing and Cellulose Fibres on Foam Microstructure
No full textInternational audienceIn many industrial fields, the development of porous and light polymer composite structures is of great interest because of their several advantages compared to a massive solid of the same chemical nature. Batch foaming of polymers is a discontinuous process carried out normally in an autoclave. The samples are saturated in a pressurised vessel, and their foaming is achieved by inducing an instability into the system. Gas solubility in polymers increases with pressure but decreases with temperature. Therefore, in the batch foaming process, the instability can be induced by a sudden drop in pressure (pressure quenching) or by a raise in temperature thus causing polymer foaming1. Pressure quenching is largely used for its ease of implementation. This foaming technology has been used for different polymers including PLA-based composites. Silk, cellulose1, jute, and wood flour have been studied as fillers in PLA foams. The operating conditions have a great influence on final foam morphology, as well as fillers nature and content. In general, fillers enhance the crystallization kinetics and PLA melt strength. Foams with reduced cell size and expansion ratio and increased cell density can be obtained compared to pure PLA foams2. This work is intended to explain the effects of size and aspect ratio of fibres as well as its content, on the characteristics of PLA foams obtained by supercritical CO2-assisted batch process by pressure quenching, which have not been studied until today. Cellulose fibres (Rettenmaier France) of different aspect ratios were compounded with PLA by extrusion and, then injected in discs, to be analysed and foamed afterwards. A complete characterisation of the crystallisation phenomenon of composites through isothermal and non-isothermal DSC, microscopic and rheological studies have been made in order to understand the effect of fibre characteristics on the solidification and crystallisation phenomena. The initial fibres size and aspect ratio and the ones within the composites have been evaluated through image analysis; in the case of the fibres embedded in the composites, an extraction process was necessary. Temperatures going from 100 °C to 140 °C have been employed at a CO2 pressure of 15 MPa, firstly for pure PLA foaming, in order to determine the most appropriate operating conditions for the composites. An analysis of fibre effects on foam morphology, crystallinity, and foaming temperature is ongoing. Figure 1 shows first foams of pure PLA obtained at different temperatures. Understanding the role of the filler size and aspect ratio, as well as the effect of supercritical CO2 and operating conditions on cell morphology of a composite foam, will allow to control its microstructure and therefore its characteristics
Intégration d'un stockage de chaleur de type thermocline à des procédés énergétiques
No full textThe main obstacle to waste heat recovery and to the development of renewable energies is a lack of storage solutions, which enable to solve the mismatch between production and consumption of energy. This PhD offers to integrate a thermocline thermal storage coupled with energy converter (heat to power, power to heat) to those energy processes to order to improve and diversify the range of energy services available, and therefore enhance the expansion of a robust and low cost solution.Mixing both academic and industrial interest (TRL 8 to 9), an experimental campaignhas be led on the Eco-Stock, the first industrial unit developed by Eco-Tech Ceram (Startup originating from CNRS PROMES). This scale 1 unit has an original horizontal geometry, favoring an industrial plug and play system. This experimental campaign enabled to validate to performances of the first thermocline storage developed for waste heat recovery. Other tests of academic interest were also carried out with degraded operating conditions (temperature and flowrate variations, stand-by periods) to assess the robustness of the technology to an industrial level. The limits of the storage regarding conception and usage were also identified. All these experimental tests enable to validate a comprehensive numerical model, but also reduced models to facilitate the storage sizing and optimization.Thermal storage coupled with energy converters can be a key technology to diversify energy services regarding electricity network, such as the conversion of electricity over production from renewable to high temperature heat (power to heat), or the conversion of waste heat to electricity (heat to power). For each service, an industrial case is proposed to carry a technical study out, to showcase the sizing or operating constraints regarding to the storage. These studies result in an economic perspective to assess the viability of those processes into a sustainable growth. The storage integration relevance to an multi energy network is highlighted.Le principal obstacle à la valorisation de chaleur fatale industrielle et au développement des énergies renouvelables est un éventail très réduit de solutions de stockage, permettant de pallier le déphasage entre production et consommation. Cette thèse propose l’intégration à ces procédés énergétiques d’un stockage thermocline couplé à des convertisseurs (power to heat, heat to power) afin d’améliorer et de diversifier les services énergétiques rendus, et ainsi favoriser l’essor d’une solution de stockage robuste et à bas coût.Mêlant un fort intérêt à la fois académique et industriel (TRL 8 à 9), une campagne expérimentale a été menée sur l’Eco-Stock, première unité industrielle développée par Eco-Tech Ceram (start-up issue de PROMES). Cette unité échelle 1 possède une géométrie horizontale atypique, favorisant son intégration industrielle. La campagne expérimentale a ainsi permis de valider les performances du 1er stockage thermoclinedéveloppé pour la valorisation de chaleur industrielle. D’autres essais d’intérêt académique ont également pu être menés sur le stockage lors de conditions de fonctionnement dégradées (variation de température, débit, stand-by) afin d’évaluer la robustesse de la technologie à échelle industrielle. Les limites de la conception et de l’utilisation de cette solution de stockage ont aussi été identifiées. L’ensemble de ces essais a permis la validation d’un modèle numérique complet, ainsi que le développement de modèles réduits permettant de faciliter le dimensionnement du stockage et son optimisation.Le stockage thermique couplé à des convertisseurs peut être une technologie clef pour diversifier certains services liés au réseau électrique, comme la conversion de surproduction d’électricité renouvelable en chaleur haute température (power to heat), ou la conversion de chaleur fatale en électricité (heat to power). Pour chaque type de service rendu, un cas réel provenant de gisements industriels est proposé afin de réaliser une étude technique, mettant en avant les contraintes propres au dimensionnement ou au pilotage du stockage et des convertisseurs. L’ensemble de ces études techniques aboutit à une mise en perspective économique afin d’évaluer la viabilité de ces procédés dans une démarche de développement durable. La pertinence de l’intégration d’un stockage à un réseau multi-énergie est ainsi mise en évidence