Thèses sur le sujet « Projection dynamique à froid »
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Raletz, François. « Contribution au développement d'un procédé de projection dynamique à froid (P. D. F. ) pour la réalisation de dépôts de nickel ». Limoges, 2005. http://aurore.unilim.fr/theses/nxfile/default/e369083a-8453-4a2d-bb2d-08ac15a75238/blobholder:0/2005LIMO0024.pdf.
This Ph. D. Work deals with the study of the formation of cold sprayed nickel coatings. In this process, powder grains are introduced in a supersonic gas stream. For each material, beyond a specific velocity called the critical velocity, particles start to bind onto the substrate. The results of this study show that, for a powder batch, the deposition efficiency is only linked to the rate of particles that can exceed the critical velocity. An increase of the particles mean velocity (obtained by an increase of the propellant gas temperature, pressure or by the use of helium) raises the deposition efficiency. The particle velocity has been calculated with two methods (the one-dimensional isentropic theory and a 2D model). Comparison of the results with measured velocity shows that the mathematical models are consistent and accurate. Two techniques for the critical velocity determination have been developed. Values obtain with them appear to be consistent with those found in the literature. Contrary to deposition efficiency, the porosity level and hardness of the coatings are not linked to the impact velocity. The addition of a particle heater to the spraying system allows to increase slightly the deposition efficiency. Using a well adapted nozzle design can also improve it significantly
Rolland, Gilles. « Élaboration et étude de l'endommagement de dépôts composites obtenus par projection dynamique par gaz froid ("cold spray") : application aux contacts électriques ». Phd thesis, École Nationale Supérieure des Mines de Paris, 2010. http://pastel.archives-ouvertes.fr/pastel-00584319.
Kergourlay, Emmanuelle. « Apatites nanocristallines biomimétiques carbonatées pour applications médicales : de la synthèse des poudres aux revêtements par projection dynamique à froid (Cold Spray) ». Thesis, Toulouse, INPT, 2016. http://www.theses.fr/2016INPT0005.
Atmospheric plasma sprayed (APS) coatings of hydroxyapatite (HA) are considered as standard coatings in the field of orthopedic implants. However, some studies have shown that these coatings contained secondary phases resulting from the decomposition of HA during the spraying process, which could potentially limit the lifetime of implants. Moreover, nosocomial infections have been reported a few years after surgery. Although HA has osteoconductive properties, it has a different chemical composition and crystal characteristics from those of bone mineral (non-stoichiometric; carbonated and poorly crystallized). Biomimetic nanocrystralline apatites, on the contrary, offer the advantage to possess a surface hydrated layer analogous to that identified in bone mineral which can be functionalized. A carbonated nanocrystalline apatite similar to bone mineral "BNAc" and a silver doped biomimetic apatite "AgBNAc" were synthesized for this study, which could potentially accelerate osseointegration of implants (BNAc and AgBNAc) and prevent nosocomial infections (AgBNAc). In order to preserve the physicochemical characteristics of these powders, thermically unstable and very reactive, an industrial low temperature deposition process was selected: the Cold Spray. In contrast with other thermal spray processes, it has the advantage of spraying unmelted particles through a supersonic gas jet. Biomimetic apatite coatings with physicochemical properties similar to the powders were obtained by Cold Spray. Preliminary tests of biocompatibility and adhesion were also carried out on these coatings : the Cold Spray process seems to be a promising method preserving the characteristics of biomimetic nanocrystalline apatites and offering the possibility to produce industrial coatings with a potential to improve implants osseointegration and resistance to infections
Blochet, Quentin. « Influence de la rugosité de surface du substrat sur l'adhérence de revêtements à base d'aluminium élaborés par projection dynamique par gaz froid ("cold spray") ». Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0025/document.
The cold spray process is based on high-speed spraying of a powder onto a substrate. The formation of a more or less dense coating depends on sprayed particle adhesion and coating build-up. The repair of metallic or composite aircraft / aerospace components is a recent application of cold spraying. The particle-substrate bond strength is due to various mechanisms, including mechanical anchoring. Substrate material hardness and surface topography governs the degree of mechanical anchoring. This thesis study is centered on the influence of these two contributions. Pure metallic and composite systems with different mechanical properties are selected. Particle deposition onto rough surfaces is investigated through the development of pure aluminium coating of harder aluminum alloy substrates. Plastic deformation and build-up mechanisms are studied for Al-SiC coatings onto ductile substrate. All the coatings resulted from an optimization stage where process parameters and materials properties are considered (gas temperature, gas pressure, particle size). Particle impact conditions are also determined by particle speed experimental measurements (using a DPV 2000 system). Substrate temperatures are determined using thermocouple and particle temperatures are studied by numerical simulation. Mechanical anchoring of particles is investigated by cross-section observation of the coating-substrate interface. Hardness gradient is also quantified. An analysis of sand-blasted surfaces morphology is performed to correlate particle size and roughness parameters. A model of particle impact is established from a finite element analysis of interface plastic deformation as a function of surface topography. Lastly, dynamic adhesion testing using a laser shock (LASAT®) are undertaken to study the potential role of interface roughness on the fracture thresholds in the light of a numerical analysis
Bunel, Margaux. « Influence du traitement thermique des poudres sur le dépôt sur projection dynamique par gaz froid (« cold spray ») d’alliage d’aluminium 2024 pour la fabrication additive ». Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM051.
Cold spray is a process where powder particles are sprayed at a high speed onto a substrate. From deformation the powder particles adhere to the substrate, which result in deposition build-up. The cold sprayed coatings show high mechanical properties, are very dense, can be thick and have a high deposition efficiency, which makes cold spray an ideal process for additive manufacturing. However, deposition efficiency for aluminum alloys such as those commonly used in different industrial sectors, are insufficient for additive manufacturing to be economically viable. In this study, a heat treatment of the powder is carried out in order to modify the properties of the powder particles to improve the deposition efficiency. The influence of the type of cold spray facilities and of spraying parameters was studied from the measurement of the particle velocity (DPV2000) and from assessing the properties of the various coatings. The coatings made of the heat treated powders compared with those made of untreated powders using similar conditions for both were used to show the influence of the modification of the particles. Additive manufacturing requires the understanding of how powder particle build-up to achieve given shapes. A model of deposition, at a macroscopic scale, based on experimental data was developed to predict the shape of the deposit. The results of these simulations were compared to experimental deposits to check thickness, shape and the surface state
Leger, Pierre-Emmanuel. « Rôle de la microstructure sur les mécanismes de corrosion marine d’un dépôt à base d’aluminium élaboré par projection dynamique par gaz froid (« cold spray ») ». Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM005.
Cold spray process is based on spraying particles carried by a gas at a supersonic speed onto a substrate. Particle deformation during impact with the substrate creates a coating. This spraying process can retain particle microstructure and produce very dense coating. This property is crucial for anticorrosion applications. The aim of this work is to understand the effect of cold spray aluminum coating microstructure on marine corrosion mechanisms. To achieve this goal, several aluminum powders (including pure aluminum, aluminum alloys and mixtures with alumina) are sprayed onto a steel substrate. Coating microstructure is studied down to a nanoscale (TEM). The coating-substrate bond strength is determined using pull-off testing. From a thorough microstructure study, various mechanisms are proposed to explain multiscale porosity formation in coatings. A numerical study using finite elements modeling complements this microstructure analysis. From particle speed (DPV-2000) and temperature (thermal camera) measurements during impact, new material models are optimized to model aluminum and alumina behavior at particle impact. Moreover, corrosion tests are conducted (including immersion and salt spray tests). The study of corroded coating microstructures is used to identify corrosion mechanisms which occur in the coating. A relationship between coating porosity and its corrosion behavior is particularly brought into light. Finally, a first approach to a technological transfer of this process to an industrial application is proposed
Delloro, Francesco. « Méthodes morphologique et par éléments finis combinées pour une nouvelle approche de la modélisation 3D du dépôt par projection dynamique par gaz froid (« cold spray ») ». Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0017/document.
This study on the cold spray process aimed at achieving an original coating build-up model, capable of predicting the resulting microstructure as a function of powder morphology and process parameters. The work focused on three main interrelated subjects: 3D powder characterization, simulation of individual impacts on a flat substrate by the finite element method and deposition build-up modeling.An innovative method based on microtomographical observations was used for 3D characterization of the powder. Image analysis allowed to separate single powder particles and to gather them into a 3D collection containing approximatively 18 000 objects. Their size and shape were quantitatively measured. A cluster analysis method (K-means) was then applied to this data set to divide the particles into 7 classes based on their shape.The second main research topic consisted in performing particle impact simulations on a flat substrate by the finite element method (using the commercial software Abaqus). The use of dedicated meshing tools allowed to simulate the impact of real particles, as observed by microtomography. Scripting techniques were used to carry out a large number of these simulations but, due to limited robustness of the procedure, only few of them were successfully conducted.The third research area focused on the development of a deposition build-up model (in 2D to allow a simpler implementation). Data from finite element results were interpolated and used in an iterative simulation, where impacting particles were deposited one by one. Different approaches were tested but the development of the model could not be completed in the framework of this thesis.Model validation could be performed on finite element simulations. The two kinds of splats (Ta on Cu and Ta on Ta) were considered separately. Concerning the first, direct microtomographical imaging could be applied, due to the heterogeneity of materials. Splats were observed, individually separated and gathered in a 3D collection as done before with powder particles. Simulated and observed splats could then be compared on a statistical basis. No particular discrepancy was observed, confirming the impact simulation method used. The second kind of splats (Ta on Ta) was complicated by the homogeneity of the materials, preventing the use of microtomography. The deposition (before spraying) of a contrast layer between Ta substrate and Ta particle was tried by different techniques. The only method giving exploitable results was the chemical vapor deposition of a Fe layer onto the powder particles. However, the small number of adherent particles and the weak contrast obtained in the images prevented the use of the methods already applied to powder particles and Ta splats onto Cu.The optimization of powder granulometry and shape (towards a specific application) is one of the main expected applications of the deposition build-up model, together with the simulation of composite powders (typically, metal and oxide). The involvement of phase transformation phenomena into the model could extend its application to the whole family of thermal spray processes (plasma, HVOF, etc.) or to other additive manufacturing techniques. In general, the philosophy behind our modeling approach could be applied to every manufacturing/coating technique where the supply material is in powder form and undergoes a certain transformation during the process. Finally, the coupling of such a model with homogenization techniques would allow the prediction of macroscopic properties depending on deposit microstructure (e.g. thermal or electrical conductivity)
Weiller, Sébastien. « Etude de la relation entre porosité et étanchéité à l'ultra-vide de dépôts à base d'aluminium obtenus par projection dynamique par gaz froid ("cold spray") ». Thesis, Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLM004.
Cold Spray is a thermal spray process, a key advantage of which is its capability to achieve highly-dense coatings. The practical objective of the study is to fully exploit this asset to obtain a metallic coating which exhibit gas-tightness in ultra-high vacuum conditions as requested for the targeted application. The thesis work consists in studying cold spray conditions to result in suitable properties. The study will focus on porosity formation mechanisms when spraying. A major objective is to determine a critical size for porosity above which gas-tightness no more meets the required specifications for the application. For this, relevant characteristics of pores (size, distribution, shape, ... ) will be assessed. More basically, the work aims to correlate, including using numerical simulation, these characteristics with the previously-mentioned formation mechanisms as a function of spraying conditions. The influence of the substrate (a metal or a polymer) onporosity will be studied in particular, through the study of modifications in the coating build-up. Coating-substrate bond strength will be determined, based on the study of adhesion mechanisms since an influence of these on gas-tightness can be expected
Bortolussi, Vincent. « Etude expérimentale et numérique de la conductivité de revêtements composites métal-polymère déposés par projection dynamique par gaz froid sur substrat composite à matrice organique ». Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM075/document.
The Cold Spray process allows to manufacture metallic coatings onto Carbon Fiber-Reinforced Composite (CFRP). This process relies on the spraying of high-velocity powder particles to result in high deformation and build up to form a dense coating. However, forming a coating made of copper particles onto a substrate containing carbon fibers was achieved out only by mixing metallic powder with a polymer powder. Although the polymer allow to build up the coating onto CFRP, it is highly electrically insulating. It would therefore decrease the electrical conductivity of the coating drastically. Investigations were carried out on the influence of the coatings microstructure on electrical conductivity. Various copper powders, with different morphologies, granulometry and oxygen contents were mixed with PEEK powder, i.e. a thermoplastic polymer. Cold spray of these powders leads to homogeneous coatings onto CFRP. The characteristics of these coatings were studied as a function of the influence of powder characteristics and spraying parameters. The deformation of the PEEK was also investigated as it governed the build up of the coating. Mechanical testing of PEEK samples and in-situ spraying measurements were performed to feed impact simulations. Then, simulated and experimental impact morphologies of copper particles onto PEEK were compared. The PEEK behavior under impact also prevented sound contacts between copper particles, which decreased the coatings electrical conductivity significantly. A morphological model of the microstructure of the coating was developed to reproduce microstructures in 3D numerically. It allows to investigate numerically the influence of the copper phase morphology on coating conductivity. This conductivity was measured experimentally for various starting copper powders. A carefully selected blend of copper and PEEK powders and optimized spraying parameters lead to homogeneous coatings onto CFRP with an acceptable electrical conductivity but still below bulk copper conductivity
Gojon, Sébastien. « Etude sur l’élaboration et la caractérisation de revêtements en alliages d’aluminium et de magnésium par projection dynamique à froid pour la réparation de pièces aéronautiques ». Thesis, Belfort-Montbéliard, 2015. http://www.theses.fr/2015BELF0272/document.
The repair of light alloy parts is a major issue in aeronautics. Aluminum alloy and magnesium alloy are widely used in aircraft parts, especially for high value-added components. Their use combined to optimizing design allows to have satisfactory products meeting mass, cost and performance requirements. However, like any other life-limited components, various damages can occur not only during handling procedure but also while operating. Rectification solutions exist but do not always comply with requirements. These limitations entail high scrap rates among high value-added parts.The various advantages of the cold spray process make it an ideal candidate for suitable coatings for light alloy aircraft components as protective, retouching or repair methods. The aim is to rebuild the damaged part by a coating whose characteristics are closest to those of primary materials. This thesis proposes to optimize different cold spray parameters for several substrate-coating pairs combining different aluminum alloys, magnesium alloys and aluminum alloy-based metal matrix composites.The first step was to optimize the main parameters of cold spray process to prevent clogging phenomenon that may occur in the expansion part of the nozzle. It decreases particle kinetics and promotes porous coating. Then, adhesion optimization of substrate-coating couples was investigated. The substrate surface preparation is a key factor on coating adhesion, where the mechanical anchoring appears essential. Finally, an innovative study was conducted to develop a method to cover locally surface defects. Offline programming trajectories were used to fill up two kinds of pre-machined defaults on aluminum alloy blocks. Results are in good agreement with spray time savings and defect free coatings after machining
Giraud, Damien. « Étude des composantes mécanique et métallurgique dans la liaison revêtement-substrat obtenue par projection dynamique par gaz froid pour les systèmes "Aluminium/Polyamide6,6" et "Titane/TA6V" ». Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2014. http://pastel.archives-ouvertes.fr/pastel-01073679.
Maestracci, Raphaël. « Influence de la microstructure sur les mécanismes d'endommagement thermomécanique de revêtements à base d'acier inoxydable AISI 316L réalisés par projection dynamique par gaz froid "cold spray" ». Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM017/document.
Aluminum alloys are commonly used in the automotive industry for lightening and power gain of thermal engines. However, thermomechanical properties are not often high enough to undergo the in-service stresses while the engine is running. High performance materials are needed. A novel approach to reach these high performances is to develop specific coatings using the cold spray route. This thermal spray process is based on the plastic deformation of sprayed powders at a supersonic velocity onto a substrate resulting in so called « splats » and stick to the surface. In this thesis, thermomechanical damage of cold-sprayed 316L-matrix composite coatings are studied. Prior to the study of composites, the elaboration steps of 316L in the cold spray coatings are established. Powder and coatings are studied to determine the influence of the cold spray process. Microstructural analyse involved optical microscopy, SEM, chemical analysis EDX and image analysis. Cristallographic analyse were performed by EBSD and DRX. Interfaces between splats are specifically studies by TEM. These consist of a crucial actor in the cohesion of coatings. Then, softer powder of Cu and harder powder of Ni700 are mixed with 316L and cold sprayed to build composite coatings. Their influence on the microstructure through the creation of new interfaces is observed. Last but not least, mechanical properties of the different coatings are compared. Hardness and tensile tests are used for quasi-static loading characterization whereas impact-sliding tests are used for dynamic loading characterization. Results and the local observation of the microstructural response to these macroscopic loadings give an insight into major damage mechanisms of cold sprayed composite coatings
Zaafrani, Ibtissem. « Dynamique et stabilisation d’un plasma magnétique froid ». Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0312.
In this thesis, we consider a linearized Euler-Maxwell model for the propagation and absorption of electromagnetic waves in a magnetized plasma. Two types of boundary conditions are considered: perfectly conducting on the whole boundary and Silver-Müller, homogeneous or not, on part of it. First, I establish the equations of the model and show its well-posedness by the theory of semigroups. Then, I am interested in the stabilization of the model. First, I carry out a study on the long- term asymptotic behavior of the solution. I show that it decreases towards zero under certain physically reasonable assumptions. I conclude that it converges to a non-zero stationary state in a larger energy space. This stationary state is linked to the topology properties of the domain, and is expressed as a function of the initial data. Secondly, I study the energy decay rate by using the frequency domain method. I establish a polynomial decay for both boundary conditions. I also prove a conditional exponential decay result in the homogeneous Silver-Müller case. In the perfectly conducting case, we show that the Euler-Maxwell system is not exponentially stable. We conclude by a result of convergence towards the time-harmonic regime in the presence of a harmonic forcing. Among the main difficulties encountered, the resolvent of the evolution operator is not compact and the internal absorption acts only on the fluid variables. No homogeneity assumption is made, and the topological and geometrical assumptions on the domain are minimal. These results appear strongly linked to the spectral properties of various matrices describing the anisotropy and other plasma properties. Finally, we extend those results to the case of a vacuum-plasma interface problem
Herbaut, Rémy. « Dynamique des liquides sur substrat froid, avec solidification ». Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCC006.
We study the liquids spreading on cold substrate, with solidification. The intended application is the aeronautical sector, which faces icing problems when the aircraft is on the ground. The deicing is currently carried out by an ethylene glycol jet, which contributes to an additional cost for the companies and a significant pollution. Our objectives focus on fundamental issues of spreading a drop on a substrate at a temperature below the solidification temperature. On a given surface, is it possible to predict whether the drop solidifies or spreads as soon as it is impacted ? What are the forms taken by it, before, during and after solidification? What is the solidification mechanism and its influence on the spreading dynamics? What are the parameters that control the dynamics of the processes involved ? Several devices and models will be implemented to provide some answers to these questions. Our goals also include strategies to avoid freezing drops and allowing them to slide before freezing. Oscillation of a droplet or grafting of polymer to modify the surface condition will also be considered. This thesis attempts to bring some new elements of understanding by focusing on two very different types of flows. First, the advance of a line of contact in the presence of solidification. Second, the growth of a solid drop under continuous liquid feed
Autones, Lucas. « Élaboration d’aciers ODS (Oxide Dispersion Strengthened) par fabrication additive laser et cold spray : compréhension des relations procédés - microstructures ». Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR004.
ODS (Oxide Dispersion Strengthened) steels are materials that exhibit very good resistance to creep and swelling under irradiation. These properties make them good candidates for cladding materials in Generation IV reactors, or for structural materials in thermonuclear fusion reactors. The dispersion of the nano-oxides, which reinforce the material, is obtained by powder metallurgy. Mechanical-alloying of an atomized steel powder with an oxide powder (Y2O3) results in the oxide dissolution in the matrix. During hot consolidation (hot isostatic pression or hot extrusion), the precipitation of the nano-oxides takes place. Designs of component with these materials and their final geometry could be improved using additive manufacturing.Since the 2010s, recent developments in additive manufacturing technologies could enable to reduce lead times and costs, while increasing the geometric, hierarchical and functional complexity of parts. They pave the way to new freedom of design compared to conventional subtractive manufacturing processes.The objective of this thesis work was to assess the potentials of different additive manufacturing techniques (SLM, DMD, and Cold Spray) for ODS steels.Thus, three types of ODS powder (mechanically-alloyed, composite and STARS) were obtained to determine the most interesting powder-process combinations. The materials produced from these different combinations have been characterized at several scales. The amount of macroscopic defects (porosities, cracks) was analyzed in order to optimize the manufacturing parameters. Their granular microstructure was observed before and after annealing at 1100 °C by optical and electron microscopy (SEM, EBSD). The nano-precipitation was analyzed by SEM, TEM and by small angle X-rays scattering. An image analysis method combining high definition electron microscopy images and a machine learning software was implemented. Finally, the high temperature tensile properties of these different materials were evaluated and are in good agreement with their microstructural characteristics. The comparison of the whole characterization results enabled to select the relevant manufacturing paths.The results obtained indicate that laser additive manufacturing processes (SLM, DMD) lead to ODS steels with low performance, regardless the type of powder used. The yttrium content can greatly decrease after consolidation. It also forms fragile Y-rich coarse phases, and the density of the nano-precipitates population appears very low. These microstructural characteristics induce tensile properties equivalent to those of an unreinforced steel. Nevertheless, the composite powder elaboration method implemented in this work makes it very easy to adapt the nature and content of the reinforcements added to the base powder. Using TiC nano-particles, very fine microstructures composed of equiaxed grains were obtained. These unusual microstructures in laser additive manufacturing offer interesting prospects.ODS steels obtained by cold spray from a mechanically-alloyed powder have characteristics similar to conventional ODS steels. After annealing, these materials have a microstructure similar to the ODS steels obtained by HIP. However, the coarse grains take up a much larger fraction of the microstructure and attest to a more advanced recrystallization. The lower hardness and elastic limit of this material compared to its HIP equivalent confirm this result, which is very encouraging if further shaping should be aimed. The very high density of Y-Ti-O nano-oxides in the Cold Sprayed ODS steel enables to achieve a mechanical resistance at 700 °C which is 50 MPa higher than the HIPed ODS. However, this material exhibits a loss of ductility which will have to be resolved. The analyzes carried out enabled to suggest two mechanisms to explain this damage, which would be caused by the presence of microcracks and porosities in the part
Yu, Min. « Elaboration de composites à matrice métallique d'alliages d'aluminium par projection à froid ». Phd thesis, Université de Technologie de Belfort-Montbeliard, 2013. http://tel.archives-ouvertes.fr/tel-00982371.
Fantassi, Said. « Contribution à l'étude de l'impact de particules projetées par plasma sur un substrat froid ». Limoges, 1993. http://www.theses.fr/1993LIMO0228.
Suo, Xinkun. « Réalisation et caractérisation des revêtements à base magnésium élaborés par projection à froid ». Phd thesis, Université de Technologie de Belfort-Montbeliard, 2012. http://tel.archives-ouvertes.fr/tel-00864186.
Xie, Yingchun. « Etude de la déformation particule/substrat au mécanisme de liaison en projection à froid ». Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0301/document.
Cold spraying, also called cold gas dynamic spraying, is a new coating technology which has been developed duringthe past three decade. In this study, a comprehensive investigation on particle deformation behavior and bondingbehavior between particle and substrate was conducted by experiment and numerical method.This thesis aims at presenting an innovative method to directly observe the fractured contact surface between thecold sprayed particle and substrate. By this means, the particle/substrate fractured contact surfaces were analyzedfor different conditions.Based on the experimental results, a new theory was proposed to explain the interfacial bonding mechanism of hardNi coating onto soft Al substrate. It is assumed that the particle peening effect is essential for the formation ofdiscontinuous metallurgical bonding. The dominant coating/substrate bonding mechanism is responsible of thetransformation during the coating build-up process of the initial mechanical interlocking to a combination ofmechanical interlocking and metallurgical bonding therefore of the formation of interfacial instabilities. The highcontact pressure is the relevant factor determining the particle/substrate metallurgical bonding. More metallurgicalbonding areas were generated due to strengthen peening effect of the subsequently deposited particles with higherpropelling gas pressure. Finally, stronger adhesion is able to occur despite the presence of a thick oxide film on thesubstrate surface by the preheating of the substrate. Higher temperatures help the materials to undergoes astronger plastic deformation that disrupts the oxide films. That leads to initiate an intimate contact between particleand substrate
Douchy, Guillaume. « Procédé de projection à froid interne et caractérisation des revêtements résultants : application au moteur d'automobile ». Besançon, 2008. http://www.theses.fr/2008BESA2009.
Within a framework of research to decrease the consumption of vehicles and thus to reduce gas emissions, one of the most accessible solutions technically and economically consists in decreasing the losses by friction in a general way within the engines, and in particular at the Piston/Rings/Liner part, which represents alone about half of these losses, and this as well for gas engine types as well as diesel types. In order to find new coatings in the cylinders of the engine, the new process known as cold spraying was adapted to internal spraying. The purpose of the present study consisted in developing an intern cold spray gun and studying the deposits obtained by the developed nozzle. The first part of this thesis was to design a cold spray gun. Based on a study of the geometries of cold spray nozzles named De Laval, a new injection of the powder was proposed. This geometry makes it possible to reduce considerably the encumbrance of the nozzle. Thus a nozzle, which is able to enter into cylinders, was designed, manufactured and validated by the deposits obtained. In addition, the numerical simulations of the flows in the nozzles allowed determining how to optimize each geometrical parameter of divergent to obtain an optimal velocity of particles. The second part of the thesis examines the coatings which are possible to obtain with the intern nozzle. Bronze and iron deposits were obtained. To launch the bases of the next elaborated deposits, the spray parameters and composite deposits were studied. The tests that were carried out underlined the difficulties to obtain composite coatings, but also showed their valuable properties
Kolli, Zehir. « Dynamique de renouvellement du parc automobile : Projection et impact environnemental ». Phd thesis, Paris 1, 2012. http://tel.archives-ouvertes.fr/tel-00860364.
Hamdi-Bellini, Radia. « Comportement quasi-statique et dynamique des aciers pour frappe et forge à froid ». Compiègne, 1997. http://www.theses.fr/1997COMP1018.
Bielousova, Oleksandra. « Etude de la structure et des propriétés de revêtements composites obtenus par la projection gazodynamique à froid ». Ecole nationale d'ingénieurs (Saint-Etienne), 2013. http://www.theses.fr/2013ENISE019.
Intensive development of the industry in the direction of design and optimisation of novel materials and coatings leads to invention and elaboration of new powder coating technologies. One of these technologies is Cold Spray of various materials and composites. The properties of composites materials depend on their phase composition and structure of various phases. For this reason, it seems to be reasonable to manage the cold sprayed material structure by following heat treatment. Such a combined technology opens the new opportunities to control the phase comporition, dislocation and gain structure of materials. In this case, the new opportunities to obtain various phase composition and properties of materials are opened. The main goal of the work is to examine the specific features of cold spraying process of composite coatings obtained by deposition of powder mixtures or separate layers of soft and hard materials, and to define their influence on composite structure and properties in order to obtain and to develop the new composite coating applications. Three main groups of coating are studied : Al-SS coating for possible application as a thermal barrier coating, Ti-Al intermetallic coating and naw anti-frictional SS-SiC coating. Thermal tratment of the coatings is performed to favour the formation of intermetallic components and stainless steel matrix graphitisation in case of SS-SiC coatings. Mechanical properties of the coatings such as microhardness and elastic modulus are evaluated on the base of straingradient plasticity theory and the parameters of the depth dependence of the materials are calculated. Possible applications of the deposited coatings are developed and discussed
Guo, Xueping. « Etude des procédés d'élaboration et caractérisation des revêtements de bronze et de ses composites préparés par projection à froid ». Phd thesis, Université de Technologie de Belfort-Montbeliard, 2009. http://tel.archives-ouvertes.fr/tel-00603634.
Malachowska, Aleksandra. « Analysis of the cold gas spraying process and determination of selected properties of metallic coatings on polymers ». Thesis, Limoges, 2016. http://www.theses.fr/2016LIMO0012/document.
The aim of this Phd thesis was to analyze the possibility of metallization of polymers surface using a Low-Pressure Cold Gas spraying method. Two polymers substrate: polyamide 6 (Pa 6) and polycarbonate (PC) were investigated. The coatings were deposited using: tin, aluminium and copper powders. Within the framework of this work powders particles velocity and temperature was calculated during spraying process. The obtained particle velocity was compared to the critical velocity to select initial spraying conditions. Direct spraying on polymers substrate brought acceptable properties only for tin powder. Aluminium coatings delaminated spontaneously after spraying process. In case of copper powder deposition of continuous layer was impossible. Next, the influence of powder morphology, heat treatment of the feedstock material and the use of interlayers on the deposition process was investigated. Consequently, aluminium and copper coatings were obtained on both polymers. For a set of received coatings (Sn, Al, Cu) microstructure was observed and the results of adhesion, resistivity, micro-hardness, Young's modulus, and oxygen content in powders and coatings measurements were given. The bonding mechanism of the powder particles with substrate material was investigated using simulation of impact of copper and tin particle on polyamide substrate in Abaqus program. The simulation results were compared to experimental results. The dissertation was summed up with conclusion and possibilities of further research
Celem niniejszej rozprawy doktorskiej była analiza możliwości metalizacji powierzchni tworzyw sztucznych za pomocą metody niskociśnieniowego natryskiwania zimnym gazem (z ang. Low-Pressure Cold Spraying – LPCS). Jako podłoże zastosowano dwa polimery: poliamid 6 (PA 6) i poliwęglan (PC). Powłoki zostały wykonane z użyciem proszków: cyny, aluminium i miedzi. W ramach pracy obliczono prędkość oraz temperatura cząstek proszku podczas procesu natryskiwania. Na podstawie porównania otrzymanych wyników prędkości cząstek proszku do prędkości krytycznej dobrano wstępne parametry procesu. W przypadku bezpośredniego natryskiwania na tworzywo jedynie powłoki cynowe charakteryzowały się akceptowalnym właściwościami. Powłoki aluminiowe miały tendencje do samoistnego odspajania. W przypadku prób nanoszenia proszku miedzi nie udało się uzyskać ciągłej warstwy. W dalszej kolejności zbadano wpływ morfologii i obróbki cieplnej proszku oraz zastosowania międzywarstw na proces formowania powłoki, co pozwoliło na uzyskanie powłok aluminiowych i miedzianych na powierzchni obydwu tworzyw sztucznych.Dla kompletu uzyskanych powłok (Sn, Al, Cu) przedstawiono zdjęcia mikrostruktury oraz wyniki pomiarów wyniki pomiarów przyczepności, rezystywności, mikrotwardości,modułu Younga, zawartości tlenu w proszku i powłoce. Mechanizm wiązania cząstek proszku z materiałem podłoża przeanalizowano za pomocą symulacji uderzenia cząstek miedzi i cyny w podłoże poliamidowe w programie Abaqus. Wyniki z symulacji zostały porównane do rezultatów eksperymentalnych. Całość pracy podsumowano wnioskami oraz przedstawiono możliwości dalszych badań
Mailler, Sylvain. « Influence dynamique de l'Himalaya sur le climat en Extrême-Orient ». Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00598530.
Casetta, Damien. « Modèle d'aide à la conduite de réseaux de froid ». Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM012.
Cooling demand management of commercial buildings can contribute to limit global warming below 2°C. District cooling is an energy-efficient option. However, improving operational performance is of great importance to ensure and increase its competitive advantages. The aim of this thesis is to contribute to the development of a decision-support tool for daily operation of district cooling networks. Challenges lie at two levels: diversity of decisions to be taken and complexity of physical phenomena involved. The original aspect of our work is to propose a methodology to improve chillers and cooling towers control, differential pressure management and dispatching between production plants with variable efficiency. Our developments are applied to the district cooling of Paris-Bercy, operated by Climespace. First; a model featuring a physical description of chilled-water production plants, distribution network and buildings substations, is developed. In particular, a semi-empirical model with identified parameters is modified to compute non-nominal characteristics of centrifugal chillers. The system model is validated against an independent dataset. Then, the model is used to find optimized controls from cooling loads forecast. The proposed methodology is sequential: pre-computation of optimal set-points at plant level and then generation of quadratic plant models to solve the dispatching optimization problem at each time step. Differential pressure is minimized with a simulation-based tracking of the critical substation. To conclude, electricity consumption reduction with optimized controls is evaluated during a summer week
Allali, Oussama. « Structure et dynamique des graphes de terrain bipartis : liens internes et prédiction de liens ». Paris 6, 2011. http://www.theses.fr/2011PA066201.
Pibernat, Jérôme. « Conception d'une électronique de traitement de signaux de forte dynamique issus d'une chambre à projection temporelle ». Bordeaux 1, 2007. http://www.theses.fr/2007BOR13600.
The emphasis on many-particles radioactive decays requires a tracking detector like a Time Projection Chamber (TPC), which operating point can be set in accordance with the nucleides analyzed. The electrical model of such a detector reveals that, depending on its operating conditions and the nature of elements under study, the signals dynamic range can be up to more than five orders of magnitude. Consequently, an application specific processing system has to be designed. To meet the requirements of the experimental equipment, this system muste be integrated and its functional architecture muste be similar to the one of the prototype presented. The topology of the input stage of the protoype narrows the dynamics of the processing. The solution suffested to solve this problem consists in substituting this stage by a second generation current conveyor (CCII) with multiple outputs. The study of its linearity leads to predict the highest signal amplitude that it's able to process. A dynamic range greater than 1. 10(5) obtained in simulation with adapted filters. Optimization of this conveyor and filters coukd lead to extend even more this dynamic range
Andreux, Régis. « Étude expérimentale et numérique d'un séparateur gaz-solide en sortie du riser d'un pilote froid de FCC ». Toulouse, INPT, 2001. http://ethesis.inp-toulouse.fr/archive/00000624/.
Andreux, Régis Simonin Olivier Hemati Mehrdji. « Étude expérimentale et numérique d'un séparateur gaz-solide en sortie du riser d'un pilote froid de FCC ». Toulouse : INP Toulouse, 2008. http://ethesis.inp-toulouse.fr/archive/00000624.
Cournède, Paul-Henry. « Un schéma bilagrange plus projection pour la simulation bifluide des instabilités de mélange ». Châtenay-Malabry, Ecole centrale de Paris, 2001. http://www.theses.fr/2001ECAP0732.
Alrachid, Houssam. « Analyse mathématique de méthodes numériques stochastiques en dynamique moléculaire ». Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1115/document.
In computational statistical physics, good sampling techniques are required to obtain macroscopic properties through averages over microscopic states. The main difficulty is that these microscopic states are typically clustered around typical configurations, and a complete sampling of the configurational space is thus in general very complex to achieve. Techniques have been proposed to efficiently sample the microscopic states in the canonical ensemble. An important example of quantities of interest in such a case is the free energy. Free energy computation techniques are very important in molecular dynamics computations, in order to obtain a coarse-grained description of a high-dimensional complex physical system. The first part of this thesis is dedicated to explore an extension of the classical adaptive biasing force (ABF) technique, which is used to compute the free energy associated to the Boltzmann-Gibbs measure and a reaction coordinate function. The problem of this method is that the approximated gradient of the free energy, called biasing force, is not a gradient. The contribution to this field, presented in Chapter 2, is to project the estimated biasing force on a gradient using the Helmholtz decomposition. In practice, the new gradient force is obtained by solving Poisson problem. Using entropy techniques, we study the longtime behavior of the nonlinear Fokker-Planck equation associated with the ABF process. We prove exponential convergence to equilibrium of the estimated free energy, with a precise rate of convergence in terms of the Logarithmic Sobolev inequality constants of the canonical measure conditioned to fixed values of the reaction coordinate. The interest of this projected ABF method compared to the original ABF approach is that the variance of the new biasing force is smaller, which yields quicker convergence to equilibrium. The second part, presented in Chapter 3, is dedicated to study local and global existence, uniqueness and regularity of the mild, Lp and classical solution of a nonlinear Fokker-Planck equation, arising in an adaptive biasing force method for molecular dynamics calculations. The partial differential equation is a semilinear parabolic initial boundary value problem with a nonlocal nonlinearity and periodic boundary conditions on the torus of dimension n, as presented in Chapter 3. The Fokker-Planck equation rules the evolution of the density of a given stochastic process that is a solution to Adaptive biasing force method. The nonlinear term is non local and is used during the simulation in order to remove the metastable features of the dynamics
Aboussioud, Rachid. « Dynamique de la persistance identitaire : complémentarité graphique et numérique dans l'autoportrait du XXIe siècle ». Thesis, Paris 1, 2014. http://www.theses.fr/2014PA010561.
Dynamics of identity Persistence wants, through the plastic self-portrait, an analysis of the concepts of ego and superego. Self Portrait raises for the majority of artists, from the oldest to the most innovative, the question of identity through the appearance, character, but also social and cultural origins and exacerbation leads to a narcissism that was the engine the activity of man y of Art masters. Remember certain periods of life, happy or unhappy memories of life situations, leads to introspection, where time is a necessary artistic and psychological structuring an individual major concept. Many artists have focused on their image using many traditional engineering plastics and, more recently, experimental (three-dimensional experiments). These representations using new tools accessible to all are now modified at will, bringing unlimited choice reversible alterations only virtual mode. In initial work (Identity Evolution) this design questions the portrait of the author with one colored drawings illuminated highlights of each face appears white or line by line to form the individual. Dynamics of identity Persistence puts into these thirty questions and faces presented as objectively as possible to deviate from the actual image to the perfect picture, the technique Makeover, widely used on the Internet and giving an opportunity to reconquer identity, the search for an aesthetic optimized, adapted to the choice of the artist: two hundred and seventeen drawings, ail outputs combined, are well designed. This package is distributed through an exhibition and a video that is adaptable to many spaces in three complementary ways:-A double timeline of self-portraits in parallel on A4 paper with a lightly tinted face objective and subjective representations of forms depending on the requirements of Gestalt's laws. -A video projection where faces are gradually revealed, giving rise to " evolutionary drawing " , close to the animation technique, and giving life to the individual with the morphing ultimate step reveals a new face smoothly corrected according to the wishes of the author. -A long white frieze chronological format A2 where the image is coupled lived and confronted with the idealized image, on the same representation by two different colors to signify the completed corrections. This research should be completed in the future, always with engine research achievements of three-dimensional self-portraits, with pointed and such anamorphic 30 printer technologies
Wu, Hongjian. « Process Modeling and Planning for Robotic Cold Spray Based Additive Manufacturing ». Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCA026.
Cold spray (CS) is a solid-state coating deposition technology that has recently been applied as an additive manufacturing (AM) process to fabricate individual components. This potential AM process is attracting more and more attention because of its advantages: high-forming efficiency, low temperature, and no phase changing of materials. These advantages make CS able to form large-volume objects to become an efficient and effective AM process. Nowadays, new advances in cold spray additive manufacturing (CSAM) call for new process implementation to improve the manufacturing accuracy and flexibility. Therefore, the purpose of this study is to enhance CS-based AM through the modeling and planning of the robotic CS process. The work of this thesis consists of three parts.Firstly, efforts have been dedicated to design and implement a new framework for CSAM. In this part, a concept of modular system is presented. Here, the current CSAM system is decomposed into different modules in order to understand the physical and functional relationships between the key elements of the entire system. This physical and functional modularity is an indispensable necessity to promote hybrid AM processes. New modules, such as in-situ measurement module, inter-process module can be integrated into the framework to bring more possibilities to the conventional CS process. It is revealed that system modularity is suitable to revolutionize the CSAM method and conduction. It can be seen that to fully exert the potential of CSAM, efforts are still required to integrate and coordinate more technologies with the help of the proposed modular framework.Secondly, a novel approach is presented to simulate the CS deposition. Here, a three-dimensional geometric model of the coating profile based on Gaussian distribution is developed. The model is combined with robot trajectory and processing parameters to simulate the evolving CS deposits. In addition, it can offer accurate profile prediction in the robot off-line programming platform, especially in case of shadow effects, which enables the integration of robot programming with simulation to better control the coating process. The results of both numerical and experimental verifications show that this proposed method has a good prediction accuracy for practice.At last, compared with the current bulk-based volume-forming strategy (e.g. a tessellation-based method), this study proposes a new spray strategy that considers the characteristics and kinematic parameters of cold spray to enhance stable layer building for 3D shape forming. Both simulation and experiments are conducted for method verification. Layer built benchmarking test objects have better shape accuracy than that of existing methods. This implies that the proposed method makes CS a real and layer-by-layer ready AM process for 3D shape forming
Gouriet, Karine. « Etude numérique de la formation de nano-agrégats créés lors de l'ablation laser à courtes impulsions ». Aix-Marseille 2, 2008. http://theses.univ-amu.fr.lama.univ-amu.fr/2008AIX22053.pdf.
The aim of this work is to understand the formation and the evolution of nanoclusters produced by short pulse laser ablation. Material ablation, plume formation and its evolution are simulated from a computational model, which combines molecular dynamics (MD) method and direct simulation Monte Carlo (DSMC) technique. The influence of both cluster and gas around the cluster parameters on its evaporation and condensation processes is analysed by using MD simulations. The obtained evaporation and condensation are directly transferred to the DSMC part of our combined model. Finally, several simulations MD-DSMC of longer-time over the plume expansion demonstrate both plume dynamic and cluster evolution. Two cluster evolution mechanisms are demonstrated : by material ejection and by collision processes during plume expansion. Comparisons with experimental findings show a good agreement with the prediction for the cluster size distribution
Pubill, Aleix. « Procédé thermochimique de production de froid de forte puissance pour application mobile. Etude et caractérisation de la dynamique du système ». Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0060.
A better cold chain logistics understanding and control is a major safety issue in deep freezing processes within -20°C/-30°C. Self-cooling solutions based on thermochemical systems appear very suitable for rapid cooling of isothermal containers and its temperature regulation for several hours. Different process concepts and configurations are presented to tackle this problem. Through their dynamic nodal modeling, involving thermodynamic management of one or various reactors, an analysis of their behaviors is performed to evaluate their relevance. A selection of the best performing configurations leads us to an industrial pre-design.To undertake quality measures, a diagnosis approach for possible reactors malfunctions is developed. The methodology is based on a comparison of experimental responses between tested reactor and reference one under the same operating conditions. A database of simulated faulty behaviors will allow the detection and identification of possible malfunctions of reactors coming from the production line
Goulas, Estelle. « Dynamique de repousse chez Trifolium repens (trèfle blanc) en relation avec la morphogenèse et l'azote protéique de réserve : Caractérisation physiologique et moléculaire des VSP ». Caen, 2001. http://www.theses.fr/2001CAEN2004.
Gillet, Vincent. « Revêtement de cuivre par projection à froid basse pression sur substrats d'aluminium texturés et composites PEEK/Carbone. Approche expérimentale et numérique. : approche expérimentale et numérique ». Thesis, Nantes, 2018. http://www.theses.fr/2018NANT4002/document.
Low Pressure Cold Spray is an emerging thermal spraying process increasingly appreciated in the industry for its simplicity, low cost and versatility. In order to enhance coatings characteristics, aluminum substrates were laser-textured with holes of varying dimensions distributed in a regular pattern before being coated with copper. An optimization of the holes dimensions led to an increase of the adhesion for Cu/Al2O3 coatings by +81% compared to a raw substrate. These results were analyzed using a mathematical model developed during the thesis allowing to calculate the surface increase induced by the laser texturing. Moreover a characterization of the residual stresses by XRD through the thickness revealed the uniformity of compressive stresses in the deposit. In a second time copper deposits were made on PEEK/Carbon composites. The need to have an organic matrix layer on the composite surface has been highlighted in order to avoid substrate erosion and allow the coating construction. A spraying strategy based on a variation of the powders granulometry being sprayed has therefore been developed in order to reduce the porosity and obtain electrically conductive coatings. In addition to this experimental aspect, a 3D dynamic model has been developed on Abaqus/Explicit. This model allowed to study the influence of the projection parameters and the substrate surface state on the particles deformation during the impact and the induced residual stresses
Blais, Laurent-Bernard. « Analyse objective de deux techniques de projection en judo : seoi͏̈ nage et uchi mata de la réalité mécanique aux applications pédagogiques ». Poitiers, 2004. http://www.theses.fr/2004POIT2316.
Through this work, we want to support the exchanges between sporting people and university research people, and we want to give to our work direct applications in term of formation and training. Beyond an intuitive approach based on empirical knowledge of the judo activity, we want to objectively understand the reality of the judo throw, from an analysis of the external and internal mechanical parameters. In the first part, we explain our method of research which tends to go beyond a reducing approach of considering the athlete in his complexity and to measure its segmentary parameters, by associating dynamographic and cinematographic measuring tools. In a second part, we present the results of the study carried out in collaboration with French champions, who allowed us to identify clearly common elements, constituting as many rules of action, whose acquisition by the athletes prove to be essential to realize a good movement. In the last part, we present the results of the calculation of the articular efforts of an athlete, carrying out a judo throw on an instrumented ergometer, like its total energy expenditure, for each phase of the movement or for each segmentary contribution
Baudry, Cyril. « Contribution à la modélisation instationnaire et tridimensionnelle du comportement dynamique de l'arc dans une torche de projection plasma ». Limoges, 2003. http://aurore.unilim.fr/theses/nxfile/default/3a9e5f66-c72c-4a0a-b773-7a84ebd75d44/blobholder:0/2003LIMO0063.pdf.
Contribution to the 3D time-dependent modeling of the arc dynamic behavior in a DC plasma spray torch This work is devoted to the tri-dimensional time-dependent modeling of the arc behavior in a plasma spray torch. It has been carried out in the fame of a collaboration with the Thermal Spray Laboratory of CEA-DAM, Le Ripault and the laboratory of Fluid Mechanics and Heat Transfers of EDF. After a summary of the operation modes of a DC plasma torch and the effect of anode erosion on the torch working, the structure of an electric arc is depicted as well as the main models of non-transferred electric arcs proposed in the literature. This review allows the determination of the main assumption and boundary conditions for a "realistic" model of the electric arc. Then, the equations, assumptions and boundary conditions of the model we have developped are presented and, the CFD code ESTET 3. 4 used to solve the model equations. The model is based on a specific value of the local electric field to predict the breakdown of the arc while its restriking is favored by a hot gas column at the spot where the highest value of the electric field is calculated. This model gives a realistic prediction of the time-dependent arc behavior according to the plasma-forming gas nature and of the temperature and velocity of the gas flow at the nozzle exit. However, it overestimates the torch voltage and dimensions of the anode arc root attachment spot
Savin, de Larclause Isabelle. « Dépôt organosilicie par plasma froid basse pression et pression atmosphérique sur substrats microstructurés ». Toulouse 3, 2008. http://thesesups.ups-tlse.fr/870/.
This PhD works is part of an industrial project on ophthalmic optic, developed by the company Essilor. The aim is to prepare a technological step in the apprehension of the optical function of the glass and in their production. The innovative idea is based on the introduction of some actives functions in the glass, thanks to its discretisation. To do so, Essilor turns toward the microlectronic technologies, and especially the plasma technologies. The thematic treated here is the deposition of a thin film by plasma on a microstructurated substrate. In order to obtain a quality of the film homogeneous on the whole microstructure, the coating must be conformal, i. E. It must have a thickness, composition and structure constant on all the microstructure parts. Thus, the issue of this PhD is the understanding of the mechanisms which control this property, through the use of two different processes, a microwave ECR low pressure plasma and an Atmospheric Pressure Townsend discharge. The effect of process parameters (power, substrate polarisation, temperature, gas mixture) on the conformity was studied. This allowed checking the significance of the shadow effect at low pressure and to bring out the main role of the ions. At atmospheric pressure, although mean free pass is lower compared to the microstructure size, the coating is mainly concentrated on the superior regions of the microstructure. In order to understand this phenomena, reactive mass transfer simulation and electrical field simulation was done. The diffusion seems to be responsible, and these effects are accentuated by the repartition of the electrical field at the surface. The predominance of one of these phenomena (diffusion or field effect) changes in function of the process conditions
Yao, Yijun. « Exploration d’un équipement d'observation non intrusif pour la compréhension des processus de projection thermique ». Electronic Thesis or Diss., Bourgogne Franche-Comté, 2023. http://www.theses.fr/2023UBFCA025.
The fourth industrial revolution ushered in a new technological era characterized by digitalization and intelligence. In this context, there is a growing tendency to combine traditional technologies with more modern information technologies. This approach is opening up a new avenue of interpretation for scientific research.In the context of this study, which is specific to thermal spraying, the work involved using a non-invasive display device to collect on-line images of a jet seeded with powder particles. Processing these images using a specially developed algorithm resulted in the extraction of relevant and reliable data on the construction processes of a spray coating.Indeed, thermal spraying, as a traditional technology in the field of surface treatments, is also a very promising technique in the field of additive manufacturing. The coatings produced by this method have excellent properties and are widely applied in a variety of sectors. It therefore seems important to change the paradigm by incorporating computer technologies.The experiments carried out enabled us to observe the phenomena/processes involved in the plasma spraying of alumina particles, and an algorithm was developed to extract the interesting data contained in the images observed (size distribution of the flying particles, growth pattern of the coating on the substrate, deposition efficiency, etc.). In this way, it was possible to study the particle velocity and flight angle distributions throughout the plasma spraying process.Subsequently, validation of the observation technique and the algorithm applied to plasma spraying made it possible to study the existing cold spraying process. In situ observation of copper particles was therefore carried out to identify the stacking process of cold-sprayed layers and to quantify the size and dispersion of the particles forming the deposit. The study also combined different characterization methods to understand the process of layer stacking during cold spraying
Jolly, Emilien. « Effet de l’Amplification Arctique sur la circulation atmosphérique des moyennes latitudes et les vagues de froid en hiver à partir de modélisation numérique idéalisée ». Electronic Thesis or Diss., Université Paris sciences et lettres, 2020. https://theses.hal.science/tel-03592535.
The Arctic Amplification (AA) is a stronger atmospheric warming in the Arctic than in mid-latitudes, and its effects on atmospheric circulation are discussed. Its impact on Rossby waves and winter cold spells in mid-latitudes is analyzed using a 3-level dry quasi-geostrophic model on the sphere, with orography. First the study is conducted by comparing long simulations: one corresponds to the winter climatology of the last 30 years, and for the other one a AA pattern is added. It is build from a composite of the warmest winters in the Arctic. A spectral analysis shows a decrease in Rossby wave phase speed for the most energetic waves. This appears to be related to a jet narrowing and is accompanied by a moderate increase in low frequency variance at mid-latitudes, which may increase cold spells. This increase can compensate locally the warming in terms of the number of cold spells. Then, in a simplified framework, without zonal asymmetries, the impact of the jet width on the waves is more particularly studied. It appears that this narrowing can be a consequence of AA. It slows down the flow, with two consequences: a slowing down of the phase speed, through changes in the vorticity gradient; and a frequency shift of the variance from high frequency to low frequency. Finally, the variability of the AA pattern, and its consequences on this mecanism, are presented. The different ways of counting AA are permeable to the influences of the rest of climate change, which may have opposite influences
Girardin, Mathieu. « Méthodes numériques tout-régime et préservant l'asymptotique de type Lagrange-Projection : application aux écoulements diphasiques en régime bas mach ». Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066377/document.
Two-phase flows in Pressurized Water Reactors belong to a wide range of Mach number flows. Computing accurate approximate solutions of those flows may be challenging from a numerical point of view as classical finite volume methods are too diffusive in the low Mach regime. In this thesis, we are interested in designing and studying some robust numerical schemes that are stable for large time steps and accurate even on coarse meshes for a wide range of flow regimes. An important feature is the strategy to construct those schemes. We use a mixed implicit-explicit strategy based on an operator splitting to solve fast and slow phenomena separately. Then, we introduce a modification of a Suliciu type relaxation scheme to improve the accuracy of the numerical scheme in some regime of interest. Two approaches have been used to assess the ability of our numerical schemes to deal with a wide range of flow regimes. The first approach, based on the asymptotic preserving property, has been used for the gas dynamics equations with stiff source terms. The second approach, based on the all-regime property, has been used for the gas dynamics equations and the homogeneous two-phase flows models HRM and HEM in the low Mach regime. We obtained some robustness and stability properties for our numerical schemes. In particular, some discrete entropy inequalities are shown. Numerical evidences, in 1D and in 2D on unstructured meshes, assess the gain in term of accuracy and CPU time of those asymptotic preserving and all-regime numerical schemes in comparison with classical finite volume methods
Nova, Rincón Arley Fernando. « Dynamic optimization of a district cooling distribution network ». Thesis, Pau, 2019. http://www.theses.fr/2019PAUU3020.
Due to the increasing demand for cooling worldwide and the need for reliable and energy-efficient alternatives to provide it, the analysis of district cooling (DC) networks has become a focus of interest in recent years. Currently, most of the developments in the field of numerical simulation and optimization of these systems have been done by implementing steady-state models. Considering this, in the present work we proposed a methodology based on mathematical programming for the dynamic simulation and optimization of the distribution system in district cooling networks.The dynamic model includes a partial differential equation to describe the variation of the temperature in the pipes, and heat and mass balances in the users and in the interconnecting nodes of the network. This arrangement is known as a partial differential algebraic equation (PDAE) problem. We detail the implementation of 2D- Orthogonal Collocation on Finite Elements (OCFE) for the discretization of the dynamic problem. Then the previously discretized model is added to the optimization constraint set, according to the simultaneous (equation-oriented) solution strategy. The optimization variables (decision variables) include the spatial and temporal profiles of the temperatures and temporal profiles of the mass flows of the system. Additional optimization variables (pipe diameters…) are progressively introduced. We apply this methodology for the analysis of an operational and a cost objective function in a medium size cooling system, serving 20 consumers grouped in five different categories with fluctuating cooling demands subject to variable external conditions. The first objective function considers that in DC networks, the temperature of the cooling utility returning to the production site must be close to the design temperature of the installed technology to ensure proper efficiency and avoid the technical issue known as low ΔT syndrome. Then, still ensuring this condition, the second objective function aims to minimize a cost function (production and pumping costs) including the diameter of the pipes as decision variables. The methodology allowed the computation of the optimal mass flow profiles to operate the system under the desired conditions and the estimation of the pipe diameters of the distribution network for two different costs of production. For the two objective functions, the dynamic simulation and optimization were performed using insulated and non-insulated piping. The proposed methodology exhibits low CPU cost that demonstrates its potential use for the development of applications for the operation and forecasting of distributed systems
HUGUES, SANDRINE. « Developpement d'un algorithme de projection pour methodes pseudospectrales : application a la simulation d'instabilites tridimensionnelles dans les cavites tournantes. modelisations d'ecoulements turbulents dans les systemes rotor-stator ». Aix-Marseille 2, 1998. http://www.theses.fr/1998AIX22104.
Zahzam, Nassim. « COLLISIONS ET INTERACTIONS FROIDES :- Collisions froides dans des pièges d'atomes et de molécules- Dynamique de l'interaction dipôle-dipôle dans un gaz de Rydberg froid ». Phd thesis, Université Paris-Diderot - Paris VII, 2005. http://tel.archives-ouvertes.fr/tel-00011696.
Trois expériences sont décrites dans cette thèse. Dans la première, la caractérisation du régime de collisions élastiques dans un piège hybride optique et magnétique a été menée. Cette étude est d'une grande importance pour évaluer, dans un tel piège, les possibilités d'atteindre la phase quantique de condensation de Bose-Einstein pour l'atome de césium. Dans la deuxième expérience, un dispositif de piégeage dipolaire de molécules de césium, réalisé à l'aide d'un laser CO2, a permis d'obtenir un échantillon dense et froid de molécules, créées par photoassociation d'atomes froids. Le confinement d'atomes et de molécules a été mis en évidence et des études quantitatives de collisions froides inélastiques molécule-atome ont pu être réalisées. Une mesure de ce taux de collisions est donnée dans le manuscrit. Nous abordons, dans la troisième expérience, l'étude détaillée des phénomènes d'interactions à longue distance dipôle-dipôle qui règnent au sein d'un gaz d'atomes de Rydberg froids. Ces interactions ont été mises en évidence et caractérisées à l'aide d'une méthode originale de spectroscopie optique de haute résolution.
Cousin, Laurent. « Simulation de sillages par méthode de projection spectrale multidomaine et technique de pénalisation : application au sillage d'une sphère en fluide stratifié thermiquement ». Nice, 2004. http://www.theses.fr/2004NICE4086.
Le, Pierrès Nolwenn. « Procédé solaire de production de froid basse température (-28°C) par sorption solide-gaz ». Phd thesis, Université de Perpignan, 2005. http://tel.archives-ouvertes.fr/tel-00011253.