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Laboratoire des Propriétés Mécaniques et Thermodynamiques des Matériaux

Overview
Works: 61 works in 66 publications in 2 languages and 68 library holdings
Roles: Other, Organizer of meeting
Publication Timeline
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Most widely held works by Laboratoire des Propriétés Mécaniques et Thermodynamiques des Matériaux
Etude expérimentale et modélisation des mécanismes de recristallisation et de la croissance de grains dans des métaux de structure hexagonale by Mariusz Jedrychowski( )

2 editions published in 2014 in English and held by 3 WorldCat member libraries worldwide

The main aim of this thesis is to describe and analyse recrystallization and grain growth phenomena taking place in hexagonal metals, in particular cold-rolled titanium and channel-die compressed zirconium were considered. For that reason, several experiements were prepared and carried out using EBSD (Electron Backstartter Diffraction) technique. In addition, a special software based on Monte Carlo Potts model was developed in order to facilitate experiemental analysis using simulation approach. Based on the obtained experiemental data and simulation results, physical models and hypotheses concerning the investigate recrystallization and grain growth processes were proposed and positively verified
Les singularités en temps fini pour les équations semi-linéaires des ondes by Asma Azaiez( Book )

1 edition published in 2014 in English and held by 2 WorldCat member libraries worldwide

This thesis is devoted to the study of the finite time blow-up phenomena for the semilinear waves equations. We treat two models in this work. In the first part, we consider a complex-valued solution for the semilinear wave equation with power nonlinearity. We first characterize all the solutions of the associated stationary problem as a two-parameter family. Then, we use a dynamical system formulation to show that the solution in self-similar variables approaches some particular stationary one in the energy norm, in the non-characteristic case. This gives the blow-up profile for the original equation in the non-characteristic case.The second part is dedicated to the study of the semilinear wave equation with exponential nonlinearity in one space dimension. We generalize the results of Godin to a much larger class of initial data. We prove blow-up estimates near any point and give an optimal bound on the blow-up rate near the noncharacteristic points
Développement d'outils numériques pour la prise en compte du couplage hydrogène-plasticité dans un code éléments finis : application à l'essai de pliage en U by Tuan Hung Nguyen( Book )

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

In the framework of the coupling between plasticity and hydrogen interactions with the metallic material, the aim of this thesis is to implement in the finite element code Abaqus © the hydrogen diffusion law coupled with the mechanical fields, accounting particularly for the trapping caused by the plastic strain. The chosen implementation strategy allows to simultaneously solve the diffusion and mechanical problems. It is based on works from the literature and needs the development of procedures in fortran 77, in particular the user procedures UMAT and UMATHT allowing the definition of the mechanical behavior and the material flux respectively. These procedures were confronted with several cases in literature. The developed procedures were applied to the numerical study of the U-bend test, used for characterizing the delayed cracking caused by hydrogen embrittlement. A parametric study on test conditions, boundary conditions on hydrogen and relationship between plasticity, trapped hydrogen, diffusive hydrogen was carried out. Finally, a transposition to the scale of a 3D polycristal was performed using a modified UMAT procedure with crystalline elastoviscoplasticity. A numerical study on the relevant parameters for defining a Representative Volume Element was carried out. Then, the simulation of a virtual u-bend test at the polycristal scale was performed thanks to a boundary condition transfer between global calculation and the RVE, in order to simulate the effect of crystal anisotropy on hydrogen concentration field
Elaboration des biomatériaux apatitiques nanostructurés en milieux polyols : caractérisations physico-chimiques et études mécaniques après compaction par spark plasma sintering by Abderrahmen Mechay( Book )

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

L'hydroxyapatite est un biomatériau bioactif largement utilisé pour la réparation et la reconstruction des défauts osseux, cependant, son efficacité est souvent limitée par sa faible densité. Le présent travail constitue une nouvelle contribution à l'étude des biocéramiques compacts nanostructurés qui sont considérés comme étant des matériaux facilement implantables au niveau osseux et dentaire. Des nanoparticules anisotropes d'hydroxyapatites ont été synthétisées par hydrolyse forcée en milieu polyol, en vue d'améliorer les caractéristiques mécaniques des biocéramiques apatitiques. Les nanopoudres obtenues ont été consolidées par le processus non-conventionnel tel que le frittage flash (spark plasma sintering, SPS) aboutissant à des massifs d'hydroxyapatites nanostructurés 3D. Ces derniers ont montré des performances morphologiques similaires à celles utilisés dans l'industrie, d'autre part, elles ont montré des performances mécaniques améliorées avec une dureté allant jusqu'à 9 GPa
Optimisation du procédé polyol pour la synthèse de nanoparticules d'oxyde de zinc : mise à l'échelle du procédé et applications photovoltaïques by Mongia Zehani( Book )

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

Thanks to developments in synthesis methods and characterization techniques, nanomaterials research field is increasingly active and attractive. This thesis aims to investigate the polyol process for zinc oxide nanoparticles synthesis. Indeed, this method has the advantage of providing a wide variety of particle morphology with a good crystalline quality. In this thesis, we show that by varying the synthesis conditions we can adjust the size, the size distribution and the morphology of nanoparticles to obtain either shaped nanospheres as small as 6 nm or nanowires as long as 600 nm. Our systemic study focused on a set of parameters that control the forced hydrolysis reaction including stoichiometry, temperature, nature of the polyol but also mixing, injection of reagents and ultrasound activation. We show that the shape of the nanoparticles is determined by the competition between growth rates of different zinc oxide crystal facets. Our study also compared different mixing devices such as laboratory reactor, T- mixer and impinging jets. More over, to mass produce zinc oxide nanoparticles, we developed an original strategy to understand the effect of mixing on nanoparticle size. In our approach, we correlate the turbulent energy dissipated as obtained from Computation Fluid Dynamics with theme asured nanoparticle size. The application to the specific case of zinc oxide has allowed us to produce sample aliquots of ~50 g per Batch. These nanoparticles were subsequently incorporated into dye-sensitized solar cells as semi conducting material at the École Nationale Supérieure de Chimie de Paris. Indeed, the morphological richness of the zinc oxide produced via polyol process suggests good adsorption of the dye on their surfaces. Our results show that the photoconversion efficiencies depend both on the morphology and the size. Our best photoconversion efficiency approaches 5.3%
Elaboration des nanoparticules d'oxyde de zirconium par voie sol-gel : mise en forme et application pour la synthèse de biodiesel by Sana Labidi( )

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

In this work, we have realized novel nanoparticulate catalysts ZrO₂-SO₄²⁻ for biofuel production. We have studied nucleation-growth kinetics of zirconium-oxo-alkoxy (ZOA) nanoparticles in the sol-gel process. The monodispersed nanoparticles of 3.6 nm diameter were realised in a sol-gel reactor with rapid (turbulent) micro-mixing of liquid solutions containing ZNP and H₂O in 1-propanol at 20°C. The nanocoatings were realised of stable colloids of ZOA nanoparticles on silica beads along with common powders obtained after precipitation of unstable colloids. The acid ZrO₂-SO₄²⁻" catalysts were prepared after drying at 80°C, wet impregnation in 0.25 mol.L⁻¹ aqueous solution of sulfuric acid and subsequent thermal treatment between 500 and 700°C and studied with BET, DTA-DSC, TEM, DRIFT, elemental analysis, DRX and other methods. The catalyst nanocoatings calcinated at 580°C showed strong activity in esterification reaction of palmitic acid in methanol at 65°C, which is about 50 times higher than that of nanopowders, and also possesses the highest stability towards recycling. Tha catalytic performance of catalytic nanocoatings was also confirmed on unedible and waste oils
Thermal Barrier Effect, Non-Fourier Effect and Inertia Effect on a Cracked Plate under Thermal Shock Loading by Wei Li( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

Thermal shock problems occur in many engineering materials and elements, which are used in high temperature applications such as thermal barrier coatings (TBCs), solid propellant of rocket-engine, pulsed-laser processing of materials, and so on. The thermal shock resistance performances and the thermal shock damages of materials, especially the interface debonding and spallation of coatings, have received considerable attention in both analysis and design. Some conventional theories, such as the Fourier's law of thermal conduction and the quasi-static assumption of the thermoelastic body, may no longer be appropriate because of the extreme loads provoked by the thermal shock. Therefore, these conventional theories need to be enriched or revised.The objective of this thesis is to develop the solutions of the transient temperature field and thermal stresses around a partially insulated crack in a thermoelastic strip under thermal shock loading. The crack lies parallel to the heated traction free surface. The thermal conductivity of the crack gap is taken into account. Hyperbolic heat conduction theory is used in solving the temperature field instead of the traditional Fourier thermal conduction theory. Equations of motion are applied to obtain the stress fields and the dynamic stress intensity factors of the crack. The Laplace and Fourier transforms are applied to solve the thermal-elastic governing equations such that the mixed boundary value problems are reduced to solving a singular integral equations system in Laplace-Fourier space. The numerical integration method is applied to get the temperature field and stress fields, respectively. The problems are then solved numerically by converting the singular integral equations to a linear algebraic equations system. Finally, numerical inversions of the Laplace transform are performed to obtain the temperature field and dynamic stress intensity factors in the time domain.Numerical results show that the thermal conductivity of the crack gap strongly affects the uniformity of the temperature field and consequently, the magnitude of the dynamic stress intensity factors of the crack. The stress intensity factors would have higher amplitude and oscillating feature comparing to those obtained under the conventional Fourier thermal conduction and quasi-static hypotheses. It is also observed that the interactions of the thermal conductivity of the crack gap, the non-Fourier effect and the inertia effects would make the dynamic thermal shock problem more complex. The magnitude of the thermal barrier, non-Fourier and inertia effects is estimated for some practical cases
Crystal Plasticity Theory Accounting for GL(2,Z) Symmetry by Roberta Baggio( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

We develop a new mesoscopic approach to crystal plasticity and apply it for the modeling of the homogeneous and heterogeneous nucleation of dislocations in 2D. Plasticity is modeled in the context of geometrically and physically nonlinear elasticity theory, by using Landau-type energy density generating a globally periodic energy landscape. The equivalent energy wells describe atomic configurations which can be mapped on each other by lattice invariant shears. This type of invariance is dictated by the global symmetry group of integer valued invertible matrices GL(2,Z).The resulting model accounts for this tensorial symmetry in the context of nonlinear elasticity with finite stretches and rotations. The activation of the 'plastic mechanisms', described in this model by the extended ravines in the energy landscape, is directed by the energy minimization which accounts automatically for the coupling between different slip planes. Such coupling is largely controlled by the saddle points corresponding to the unstable high symmetry phases. Then, we used to simulate the collective nucleation of dislocations with the main goal of quantifing the effects of crystal symmetry and sample orientation in the loading device. Our numerical simulations show that homogeneous nucleation results in the formation of the dislocation patterns which are are characterized by high spatial complexity. We perform a systematic comparison with atomistic simulations, which suggest that our mesoscopic model is capable of capturing the main atomistic effects. The main advantage of the new model is that short range dislocations interaction is accounted automatically, whitout ad hoc phenomenological realtions. Being designed for the study of the evolution of a large number of interacting dislocations, the proposed mesoscopic model opens new possibilities for studying the complexity of plastic flows in crystals associated with the emergence of scale free spatial and temporal correlations
MECAMAT 93( Book )

1 edition published in 1993 in English and held by 1 WorldCat member library worldwide

Prediction of Phase Equilibria Associated with Hydrotreating Process of Biomass by GC-PPC-SAFT Equation of State by Thi Kim Hoang Trinh( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

The main objective of this thesis is to develop a predictive tool to compute the vapor-liquid equilibria (VLE) associated with hydrotreating operation from biomass for process simulation. The construction of a reliable database of hydrogen and the other hydrotreating gases solubilities have been done. The model used based on the Group Contribution - Polar Perturbed Chain - Statistical Associating Fluid Theory (GC-PPC-SAFT), which is PC-SAFT combined with the group contribution proposed by Tamouza and a polar term developed by Nguyen Huynh. The systematic tests have been perform for mixtures of alcohols, aldehydes, esters, ethers, ketones,... A new non-additive contribution has also been proposed based on the reflections on the repulsive interactions and the free volume effect. The model development are validated by Monte Carlo simulations. This non-additive term has been integrated in GC-PPC-SAFT Equation of state and tested for systems containing hydrogen. Group contribution method has been extended to its parameter. Average deviations on Henry's constant are within the experimental uncertainty (~10%). We also have performed the prediction of the other gases i.e. CO, H₂S, NH₃ solubility using GC-PPC-SAFT. A cross associative parameter has been used for systems containing H₂S and NH₃. The results are quite acceptable and within the experimental uncertainty (~20%)
Étude expérimentale et numérique de l'hydrodynamique de l'écoulement dans un réacteur continu by Khaled Oualha( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

Au cours de ce travail de thèse, sur l'hydrodynamique de l'écoulement dans le un réacteur continu, où les propriétés des nanomatériaux élaborés dépendent des caractéristiques morphologiques et structurales de la solution colloïdale issue du réacteur, nous avons d'abord optimisé les conditions d'utilisation (Re ≈ 6000), ainsi que la géométrie du T-mélange dans le but d'améliorer la qualité du micro-mélange. Ensuite, des mesures expérimentales ont permis de vérifier que la condition de Damköhler est respectée (Da ≤ 1). Enfin, ce résultat a été validé numériquement. Au delà de cette valeur de Re critique (Re* ≈ 8000), nous avons mis en évidence le phénomène de cavitation dans le T-mélange. Ce phénomène à été étudié expérimentalement, par des mesures SLS, et numériquement par des simulations CFD. Les résultats obtenus par ces deux approches concordent. Enfin, des mesures DLS ont été effectuées pour étudier et caractériser les bulles de cavitation. Ces dernières ont permis d'évaluer la taille des bulles ainsi que leur trajectoire le long de l'axe Z à la sortie du T-mélange. Cette étude a été suivie par des simulations numériques de la cavitation et du modèle multiphasique dans notre écoulement. Les deux études, expérimentale et numérique, ont confirmé que la diminution de l'intensité de la lumière diffusée mesurée par SLS le long de l'axe Z est due à l'évolution du nombre et de la taille des bulles
Etude expérimentale de la multifissuration et de la décohésion de films minces et nanostructures magnétiques sur substrats flexibles : effet sur l'anisotropie magnétique by Skander Merabtine( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

Flexible and stretchable magnetic systems are of increasing interest for the development of electromagnetic devices conformable to non-planar surfaces. In this context, the objective of this thesis is to identify the relationships between irreversible mechanical phenomena (cracking and delamination) at large strains and magnetic properties of thin films of nanometric thicknesses (CoFeB and NiFe alloys) deposited on polymer substrate (Kapton®) by magnetron sputtering. In a first time, tensile tests coupled in situ with atomic force microscopy or electrical resistance measurements were used to study thin film multifissuration and subsequent localized debonding (buckles). These measurements made it possible to highlight areas of macroscopic strains for which each mechanism was predominant. In addition, the adhesion energy could be discussed and estimated from the monitoring of the buckles under applied strain. In a second step, ferromagnetic resonance measurements carried out ex situ made it possible to link the previously identified areas of strains to the evolutions of the magnetic anisotropy of thin films. In addition, a correlation between strain heterogeneities and Gilbert damping coefficient was found. Finally, the magnetomechanical properties of NiFe nanowires arrays have made it possible to highlight the advantage of nanopatterning for these deformable magnetic systems
Application de techniques d'opto-acoustique et de calculs de premiers principes à la caractérisation des propriétés élastiques de films minces by Chenhui Li( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

Les propriétés élastiques sont d'une importance fondamentale pour un matériau. Avec la combinaison des techniques acoustique picoseconde et de la diffusion Brillouin, nous avons mesuré les vitesses du son et constantes élastiques dans divers films minces déposés par pulvérisation magnétron, y compris des nitrures de métaux de transition, binaires et ternaires épitaxiés (TaN, TiN, ZrN, Ti1-xZrxN), des alliages polycristallins à haute entropie ((CoCrCuFeNi)1-x(Al, Nb)x), et leurs alliages de nitrure interstitiels (CoCr(Cu,Mn)FeNiNx). D'autre part, des calculs ab-initio basés sur la théorie de la fonctionnelle de la densité (DFT) ont été effectués pour fournir des constantes élastiques monocristallines avec considération de lacunes.Il a été constaté que pour les nitrures binaires et ternaires, les lacunes jouent un rôle énorme sur les propriétés élastiques, en particulier dans le cas de TaN. Alors que dans le cas de TiN, ZrN et Ti1-xZrxN, l'influence des lacunes est moindre mais reste perceptible. Dans le cas des alliages polycristallins à plusieurs composants et des alliages interstitiels, les vitesses du son et les constantes élastiques effectives sont associées à des effets de composition chimique (Al, Nb et N), à des transitions de phase (FCC, BCC et amorphe), et des changements de textures et de porosité. Le module élastique correspond au module de nanoindentation EIT. La concordance globale entre nos mesures de propriétés élastiques et les calculs DFT a été atteinte. En outre, DFT ont également fourni des informations précieuses sur les propriétés structurelles et la stabilité des phases observées
Discontinuous Galerkin Modeling of Wave Propagation in Damaged Materials by Quriaky Gomez carrero( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

Dans cette thèse on utilise une méthode de Galerkin discontinue (GD) pour modéliser la propagation des ondes dans un matériau endommagé. Deux modèles différents pour la description de l'endommagement ont été considérés. Dans la première partie de la thèse on utilise un modèle d'endommagent assez général, basé sur une modélisation micromécanique. Pour ce modèle on établit un critère de stabilité basé sur une densité critique de fissuration. On développe aussi une méthode numérique GD capable de capturer les instabilités au niveau microscopique. On construit une solution exacte pour analyser la précision de la méthode proposée.Plusieurs résultats numériques vont permettre d'analyser la propagation des ondes dans les configurations planes et anti-planes. Dans la deuxième parte de la thèse on étudie la propagation des ondes dans un milieux fissuré (microfissures en contact avec frottement). La méthode numérique développée utilise une technique GD et la méthode du Lagrangien augmenté. En utilisant cette méthode on a pu calculer numériquement la vitesse de propagation moyenne dans un matériau endommagé. On a pu comparer les résultats obtenus avec les formules analytiques obtenues avec des approches micromécaniques. Finalement, on a utilisé les calculs numériques pour étudier la propagation des ondes après un impact sur une plaque céramique pour les deux modèles mécaniques considérés
Matériaux nanométriques à base de métaux 3d (Fe, Co, Ni) : Nouvelles voies de synthèse et caractérisations by Noémie Ballot( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

Analyse expérimentale et numérique de l'essai de disque de rupture : Cas de l'acier AISI 4135 testé sous hydrogène gazeux by Kevin Ardon( )

1 edition published in 2015 in French and held by 1 WorldCat member library worldwide

This work focused on the experimental and numerical analysis of the normalized disk pressure test used to select metallic materials hydrogen sensitive and particularly aimed to evaluate the potential extension of the test to higher pressures. The study focused on an AISI 4135 steel, which composed hydrogen gas storage vessels. Disk pressure tests had been leading under helium and hydrogen gas in order to study the influence of some parameters on failure pressures and to obtain experimental deflection-pressure curves. The response of the test for pressures higher than in the usual domain of specifications was studied for different disk thickness. SEM-EBSD characterization of failed or cracked disks allowed examining cracks at different scales in the bainitic microstructure. Finite element simulations of disk pressure test permitted to analyze the influence of different parameters on mechanical field distributions in the disk and led to a satisfying comparison with experimental results. Helium failure pressures were obtained by a ductile damage computation ; and hydrogen failure pressures were described thanks to a cohesive elements model. Distributions of diffusive and trapped hydrogen in the material during a disk pressure test were obtained considering hydrogen diffusion is assisted by the hydrostatic pressure and the evolution of trapping with strain. Extension of the simulation at polycrystalline scale open the way to embrittlement index ; taking into account microstructural heterogeneities
Élaboration de nano-fils 1D ferromagnétiques de cobalt à travers le procédé polyol et étude théorique du pouvoir réducteur de BEG (1,2-butanediol) by Khouloud Mrad( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

The synthesis of nanomaterials based on transition metals such as cobalt increasingly attracts, in recent years, the interest of the applied researches. From one hand this is due to the intrinsic magnetic properties of cobalt (strong residual magnetization, magneto-crystalline anisotropy constant as well as a high curie temperature) and on the other hands to the new properties presented by the reduced size and controlled morphology of the nano-objects. Soft chemistry process, like the polyol synthesis method, allows driving the morphology and microstructure of the nanoparticles thanks to the control of various synthesis parameters (the nature of the metal precursors, the basicity of the solution, the nature of the polyol, the temperature ramp ...), which also influence the magnetic properties. The first part of this work is devoted to the synthesis of cobalt nanowires (NWs) by the polyol process using laurates as metal precursors and varying the stirring speeds during synthesis. Our results show that the magnetic properties are strongly correlated with the morphological and micro-structural ones of NWs. The stirring speed inside the reaction solution appears as a driving force for finely driving the structural / morphological and magnetic properties of the elaborated NWs. The magnetic performances of the synthesized NWs have been evaluated by measuring the stored magnetic energy BHmax and its behavior as a function of the structural defects. The second part of this work focuses on the theoretical study, by 'DFT' calculation, of the electronic structure influence of the different polyols used for elaborations. The results show that the reducing power of 1,2butanediol (BEG) used for our syntheses, is higher compared to those of PEG (1,2propanediol) and EG (Ethylene glycol) usually used in litterature
Tungstène et alliages nanostructurès dans le système W-V-Cr pour la fusion : synthèse, densification et propriétés mécaniques by Sarah Dine( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

The aim of this thesis concerns the synthesis of nanostructured tungsten and tungsten alloys, related to the thermonuclear fusion issue, with a double perspective, one concerning the powders themselves,in order to simulate the dust that will be produced during the tokamak operation, the other concerning bulk materials, where the nanostructure could bring a significant improvement on mechanical properties (elastic limit, ductility), and also on specific properties related to this operating environment (resistance to sputtering, blistering, corrosion, ...).To do so, we synthesized tungsten and binary and ternary alloys in the W-V-Cr system using Selfpropagating High-temperature Synthesis. These powders were then sintered using Spark Plasma Sintering, in order to retrieve bulk dense samples. At each step of the process, the materials were characterized using X-Ray Diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, microhardness and compression tests. Our results show that we were able to obtain bulk nanostructured samples, with a relative density ranging from 97 to 100% depending on the alloy, with an elastic limit of up to 1000 MPa and a ductility of about 30%, which is a very promising results for a tungsten alloy with no rhenium
Spectroscopie Brillouin dans les couches minces, multicouches et nanostructures magnétiques : étude de l'interaction Dzyaloshinskii-Moriya by Hedi Bouloussa-Huynh( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

This work aims to investigate, experimentally and theoretically, the behavior of spin waves (SW) in ultrathin layers, multilayers and magnetic nanostructures in the presence of interface Dzyaloshinskii-Moriya interaction (DMI). For this purpose, we used the Brillouin light scattering spectroscopy (BLS) as an experimental probe. This technique has proven to be an efficient tool for measuring the DMI; an effect that results in an asymmetry of the Stokes and anti-Stokes lines of a BLS spectrum for a thin ferromagnetic film in contact with a heavy metal producing a strong spin-orbit coupling (SOC). Thus, in the presence of DMI, the frequencies of two SW propagating in opposite directions will be different due to inversion symmetry breaking.Different systems were discussed and different situations and parameters were considered.On simple ultrathin layer systems, the behavior as a function of the thickness of themagnetic film or the effect of annealing have been identified, highlighting the interfacial nature of the DMI and the role of the structural and chemical quality of the ferromagnetic/heavy metal interface.Moreover, we have shown that the addition of non-magnetic impurities with high SOC in light metals interfaced with a ferromagnetic layer can be an effective approach to simultaneously improveand control magnetic damping, perpendicular anisotropy and DMI. A correlation between these SOC parameters has been also demonstrated. In thin film stacks, particular attention has been dedicated to the role of dipolar coupling,exchange coupling and magnetic anisotropy on the behavior of SW in the presence of DMI. It appears that the quantitative measurement of the DMI can deviate significantly from that obtained from the analytical expression known for simple thin layers where the value of the DMI is directly proportional to the wave vector of the SW. A complete calculation is thus necessary for all non-symmetrical cases (non-equivalent interfaces, different interface anisotropies, etc. . . ).The theoretical results presented for this purpose represent an extremely useful tool.The study of different nanostripes arrays in presence of DMI was the opportunity to highlight the effects of size and periodicity in different situations. Completely decoupled nanostripes or inpartial physical contact with periodic layer thickness were discussed. We have thus demonstrated the absence of DMI for stationary spin waves according to the width of the decoupled stripes and correlated the behavior of the SW with their attenuation length and the periodicity of the arrays, whereas a modulated magnetic behavior by the presence of the DMI was observed for the coupled stripes via a ferromagnetic film.The results obtained in this thesis work contribute to the understanding of the dynamic magnetic behavior of systems in the presence of DMI that can contribute to the efficient engineering of future systems for spintronics or spin-orbitronics, particularly based on configurations of chiral spin texture such as skyrmions
Contribution à la compréhension des liens entre microstructure et propriétés tribologiques d'aciers inoxydables haute dureté après traitements de surface by Edson thiago Silva santos( )

1 edition published in 2015 in French and held by 1 WorldCat member library worldwide

Des industriels du domaine aéronautique se sont regroupés autour du projet MEKINOX (Mécanique Inoxydable) visant à développer l'utilisation de différentes nuances d'aciers inoxydables en raison de leur haute résistance mécanique et de leur résistance à la corrosion. Cependant ces aciers sont réputés sensibles au frottement. Dans ce contexte, ce travail de thèse est dédié dans un premier temps à l'étude de l'effet des différents traitements thermiques et de surface sur la microstructure des aciers inoxydables visant à améliorer leur aptitude au frottement. Nous avons mis en évidence différents mécanismes de durcissement : par précipitation, par changement de phase et par solution solide. Dans un deuxième temps, nous avons mis en place une démarche expérimentale permettant de comparer la réponse des différents couples de matériaux sous contact roulant et glissant extrêmes. Ces essais nous ont permis de caractériser l'évolution du coefficient de traction et de classer les différents états métallurgiques selon leur résistance à l'usure. Dans un troisième temps, nous avons caractérisé les différents types d'endommagements se produisant en surface et en sous-couche. Enfin, l'utilisation de l'EBSD nous a permis caractériser la déformation plastique en sous couche et de tenter de corréler la valeur de la densité de HAGB (Angles à forte désorientation) avec la résistance à l'usure des différents états métallurgiques des aciers étudiés
 
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WorldCat IdentitiesRelated Identities
Alternative Names
Centre national de la recherche scientifique

CNRS. Laboratoire des Sciences des Procédés et des Matériaux.

Laboratoire des propriétés mécaniques et thermodynamiques des matériaux

Laboratoire des Sciences des Procédés et des Matériaux

Laboratoire des Sciences des Procédés et des Matériaux facility in Villetaneuse, France

Laboratory of Science of Processes and Materials

LIMHP

LPMTM

LSPM.

Mechanical Properties and Thermodynamics of Materials Laboratory

Université Paris 13. CNRS. Laboratoire des Sciences des Procédés et des Matériaux.

Université Paris 13. Laboratoire des Sciences des Procédés et des Matériaux.

Université Paris 13 Mechanical Properties and Thermodynamics of Materials Laboratory

UPR 1153

UPR 3407

UPR 9001

Languages
French (17)

English (8)