Dissertations / Theses on the topic 'Parois Élastiques'
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Bardot, Anne. "Modélisation acoustique basses fréquences de cavités en présence d'absorbants sur parois rigides ou élastiques." Compiègne, 1992. http://www.theses.fr/1992COMP0424.
Full textBardot, Anne. "Modélisation acoustique basses fréquences de cavités en présence d'absorbants sur parois rigides ou élastiques." Compiègne, 1992. http://www.theses.fr/1992COMPD424.
Full textAit, Moudid Lahcen. "Couplage Fluide Structure pour la simulation numérique des écoulements fluides dans une conduite à parois rigides ou élastiques, en présence d'obstacles ou non." Phd thesis, Université d'Artois, 2007. http://tel.archives-ouvertes.fr/tel-00341094.
Full textLa formulation Euler-Lagrange Arbitraire (ALE) a été utilisée, en considérant un maillage dynamique, où le solide est décrit par une formulation Lagrangienne et le fluide par une formulation Eulérienne. Le modèle fluide est validé en considérant des cas tests académiques et concernent les cas : de la marche, de la cavité, de l'écoulement autour d'un cylindre, etc... Le modèle solide est validé en considérant le cas d'une poutre encastrée-libre et encastrée-encastrée, le cas d'un cylindre soumis à son poids propre et le cas d'une arche elliptique.
Un algorithme de couplage est alors mis au point pour la mise en oeuvre de cette interaction fluide-structure. Cet algorithme, basé sur un schéma explicite, permet le transfert de champs de façon interactive. L'efficacité de la méthode ALE et du couplage fluide-structure a été évaluée en considérant plusieurs cas tests: solide immergé dans un canal, où s'écoule un fluide en écoulement transitoire ou stationnaire, écoulement d'un fluide dans une canalisation à parois élastiques, etc...
Les résultats montrent que ce couplage explicite-interactif permet d'utiliser un maillage et un schéma différent pour le fluide et la structure, et jouit de l'avantage de ne pas utiliser de grosses matrices de stockage des données.
Rais, Abdelillah. "Contribution à la modélisation des champs magnétiques dans R3 : résolution d'un problème par éléments finis hexaédriques et validation sur un cas-test ; établissement et mise en oeuvre numérique d'une formulation spécifique aux systèmes à parois minces." Tours, 1997. http://www.theses.fr/1997TOUR4009.
Full textRiveiro, Moreno Carmen. "Interaction of shock waves with compliant walls." Electronic Thesis or Diss., Institut polytechnique de Paris, 2024. http://www.theses.fr/2024IPPAX011.
Full textThis thesis aims to characterize the interaction between a compliant wall and a transonic normal shock. The flow topology and dynamics over a rigid wall is first determined. Using schlieren visualisation and unsteady pressure measurements the different temporal and length scales involved in the shock wave turbulent boundary layer interaction are characterized.A compliant wall is then designed so that its natural frequencies are within the same order of magnitude as the frequency range of the shock oscillations. In that manner, the compliant wall is expected to react to the shock wave forcing. The compliant wall's material and geometry are determined through numerical parametric studies based on modal analysis as well as the static deformation of the compliant wall caused by the flow. Two compliant walls are manufactured, one exhibiting elastic behavior, and the other viscoelastic behavior.The interaction between the normal shock wave and the compliant walls are experimentally characterized. In both cases the shock location is varied. In the elastic compliant wall configuration, the fluid-structure interaction is highly dependent on the shock position. The fluid-structure interaction varies from a large-amplitude synchronized regime to a non-synchronized regime, depending on the shock position. The large-amplitude synchronized regime was studied as a function of the structural natural frequencies. For that purpose, the compliant wall thickness and boundary conditions were modified. With increasing thickness, the amplitude of the oscillations considerably diminishes. Clamping the bottom surface of the elastic compliant wall yields no fluid-structure interaction. On the viscoelastic compliant wall configuration, large deformations of the compliant wall with no dynamic fluid-structure interaction are found. Such a result highlights the capability of viscoelastic materials to react differently depending on the external forcing frequency: the compliant wall's large static deformation corresponds to a soft structure, whereas its dynamic response is characteristic of a rigid one
Jaamei, Saïd. "Étude de différentes formulations lagrangiennes pour l'analyse non linéaire des plaques et coques minces élasto-plastiques en grands déplacements et grandes rotations." Compiègne, 1986. http://www.theses.fr/1986COMPD027.
Full textSoualmi, Lahbib. "Caractérisation des propriétés élastiques de la paroi artérielle par ultrasonographie endovasculaire." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0025/NQ38729.pdf.
Full textDanila, Emilian. "Théorie de la diffusion résonnante multicanaux : application à la diffusion acoustique par un tube élastique aux parois excentrées." Le Havre, 1995. http://www.theses.fr/1995LEHA0006.
Full textFranquet, Alexandre. "Identification de modules élastiques in vivo en utilisant l'imagerie par résonance : Application à la paroi des artères carotides." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2012. http://tel.archives-ouvertes.fr/tel-00784102.
Full textMarque, Valérie. "Détermination des propriétés élastiques de la paroi aortique dans différents modèles physiopathologiques murins : méthodologie, étiologie et implications thérapeutiques." Nancy 1, 2000. http://www.theses.fr/2000NAN12003.
Full textNobre, Dantas Grassi Estephanie. "Comportement anisotrope de tubes médicaux à parois mince en alliage à mémoire de forme super-élastique de nickel-titanium." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI067/document.
Full textThin walled tubes of Nickel-Titanium shape memory alloys (NiTi SMA) are widely used in the fabrication of self-expandable stents. The operation of stents relies on the superelastic effect (SE), as many other applications of NiTi SMA in the biomedical field. The SE is a reversible crystallographic phenomenon that gives SMA the ability to recover large strains through simple unload. Due to the crystallographic nature of the SE, the mechanical properties related to this effect are expected to be affected by the inherent anisotropy of the tube, which emerges from its fabrication process. However, NiTi is still often treated as isotropic in the design and optimization of such devices. One of the difficulties preventing the use of anisotropic models is a lack of mechanical characterizations about the NiTi tube's anisotropy. The present work aims to perform such characterization for a thin walled NiTi superelastic tube. In an experimental campaign, the tensile behaviour of the tube is analysed at different orientations and temperatures. Digital Image Correlation (DIC) technique is used to monitor the strain distribution during tensile tests. Results show that all the analysed properties related with SE are anisotropic. All the orientation dependencies are nearly symmetrical to 45° from the tube's axis. Some properties are also dependent on temperature, a dependence that is also anisotropic. A thermodynamic approach based on the Gibbs free energy is used to analyse these orientation and temperature dependencies. With this analysis it was possible to relate the SE stress hysteresis and thermodynamic irreversible energy contributions. Finally, the influence of anisotropy on the strain distribution of tensile samples is verified. Focus is given to the analysis of the strain localization phenomenon throughout loading and unloading. The inclination of the localization front band is characterized and evaluated with a plasticity approach. The front angle observed with DIC is predicted using global strain rate data
El, Khouzai El Mostapha. "Ecoulements transitoires en conduite élastique et viscoélastique : Influence relative de la déformation longitudinale de la paroi." Lyon, INSA, 1993. http://www.theses.fr/1993ISAL0051.
Full textThe study concerns the analysis of the influence on transient flows of a real pipe deformation of thin walled tubes, with longitudinal displacement in perfect and viscous fluids, A general treatment already has been developed which allows to account on one side, for the flexure and shear deformation, and on other side for the inertia of the pipe and the longitudinal deformation which will be neglected in the previous studies. The asymptotic development has been established in order to facilitate the direct analysis of flows singularities (primary wave front, diffusion front) in relation to different cases considered (Newtonian or perfect fluid, elastic or viscoelastic pipe), The general case has been treated numerically, by direct numerical inversion of the system of equations Expressed in the space transform LAPLACE-CARSON. A t ypical case has been treated concerning semi-infinite pipe fixed at the origin
Djemili, Abdelouaheb. "Influence de l'ancrage de la conduite - paroi élastique ou viscoélastique sur les écoulements en regime transitoire." Lyon, INSA, 1988. http://www.theses.fr/1988ISAL0077.
Full textRohan, Christian Pierre-Yves. "Etude biomécanique de l’action des Bas Médicaux de Compression sur les parois veineuses du membre inférieur." Thesis, Saint-Etienne, EMSE, 2013. http://www.theses.fr/2013EMSE0721/document.
Full textCompression therapy is a highly effective modality for treating venous disorders of the lower leg and is considered as the “gold standard” for non-operative therapy. However the mechanisms by which Medical Compression Stockings (MCS) benefit the control and treatment of venous insufficiency are neither clearly understood nor have they been conclusively demonstrated. In the present study, the biomechanical response of the lower leg veins to elastic compression is modelled in order to address some of the issues relating to the mechanisms by which it achieves its medical function. First, a new methodology has been developed in order to predict the pressure transmitted to the superficial vein wall during external compression and to quantify the resulting variations of transmural pressure and of the vein cross sectional area. A parametric study was performed to study the influence of the model parameters on the response of the vein. The developed model was also used to simulate different scenarii related to the use of elastic compression after sclerotherapy. In a second step, a numerical approach was developed to model the biomechanical response of deep veins to elastic compression. A parametric study was performed to evaluate the relative influence of the muscular aponeurosis, muscular contraction and external compression applied by MCS. The obtained results bring a new insight on MCS mechanical action and its possible benefits. They also open up new perspectives, especially, regarding the development of new tools to assist MCS manufacturers in adapting the level of compression to the location of the deep vein, the morphology of the patient and the severity of the disease
Maknun, Imam Jauhari. "Évaluation numérique des éléments finis DKMQ pour les plaques et les coques." Thesis, La Rochelle, 2015. http://www.theses.fr/2015LAROS040/document.
Full textIn the linear case, the Mindlin-Reissner model for thick plates and the Naghdi model for thick shells are commonly used. The finite element discretization of these models leads to numerical locking phenomenon when the thickness approaches zero : shear locking for plates and both shear and membrane locking for shells. There are some finite elements that could reduce or even eliminate this phenomenon. DKMQ element for plates or DKMQ24 element for shells, are low-order elements, based on a mixed formulation, introduced a few years ago to prevent the numerical locking phenomenon. In this thesis, we concentrated on numerical evaluation of the performance of these elements. Besides the classical benchmark tests, we also focused on the analysis of discrete inf-sup condition for DKMQ element. We studied the s-norm test proposed by Bathe for DKMQ24 element. Finally, we performed a posteriori error estimation for DKMQ and DKMQ24 elements, using the error estimator Z2 (proposed by Zienkiewicz and Zhu), associated with the averaging, projection or SPR recovery methods. The results obtained have enabled us to quantify the performance of these two finite elements for locking problems, and to identify their limits. Two important applications of these elements DKMQ and DKMQ24 were then presented ; the first one concerns thin-walled beams with open cross-section and the second one composite plates
Martin, Hugo André Roger. "Convex contact dynamics methods with friction : granular flow and generated elastic waves." Thesis, Université de Paris (2019-....), 2019. https://theses.md.univ-paris-diderot.fr/MARTIN_Hugo_Andre_Roger_va1.pdf.
Full textThis work concerns the modeling of dense granular media and their interactions with acoustic phenomena at the laboratory scale.The models that are developed in order to describe the movement of grains can be range into the category of non-smooth discrete methods, often referred to as "contact dynamics". When we consider the friction forces between particles in these models, we obtain constrained optimization problems which are not convex in general. Two convex approaches to the modeling of friction forces in contact dynamics are proposed here.The links between granular flows and the elastic wave propagation are an important topic nowadays. In particular, the acoustic signal emitted by these flows as well as the wave propagation within the medium itself are current research topics. Two studies are proposed here that concerns the relations between granular assembly and generated elastic waves propagation. In particular, a wave propagation model is proposed, whith its variables defined as the infinitesimal perturbations of the grain positions around equilibrium configurations
Debord, Régis. "Développement d'une cellule haute pression haute température dans la presse Paris-Edimbourg pour la mesure de propriétés élastiques et de densité : Application sur les oxydes de fer." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2001. http://tel.archives-ouvertes.fr/tel-00189118.
Full textDebord, Régis. "Développement d'une cellule haute pression haute température dans la presse Paris-Edimbourg pour la mesure de propriétés élastiques et de densité : application sur les oxydes de fer." Paris 6, 2004. http://www.theses.fr/2004PA066448.
Full textDoué, Manon. "Rôle de la carbamylation des protéines matricielles dans l’altération des propriétés de la paroi vasculaire : application à l'anévrysme aortique." Thesis, Reims, 2019. http://www.theses.fr/2019REIMS042.
Full textNonenzymatic post-translational modifications of proteins, such as glycation or carbamylation, alter their structural and functional properties, and result in their molecular aging. The carbamylation reaction corresponds to the binding of cyanate, mainly derived from urea, to the amino groups of proteins. Several studies have demonstrated a link between protein carbamylation and cardiovascular complications. The aim of this work was to determine how carbamylation of matrix proteins could participate in the modification of the mechanical properties of the vascular wall and in the development of aortic aneurysm. Our experiments show that vascular matrix proteins, including elastin, are carbamylated. Although fiber morphology is unchanged, carbamylated elastin is more sensitive to pancreatic elastase degradation. The increased carbamylation rate of aortic matrix proteins in a murine model fed with water supplemented with cyanate leads to an increased stiffness of elastic fibers, as evaluated by atomic force microscopy, which is associated with an increase of pulse wave velocity. Cyanate-diet mice have less frequently aortic aneurysms and a smaller proportion of aneurysm ruptures. Finally, in vitro carbamylated proteins are able to stimulate the migration of vascular smooth muscle cells and to induce an oxidative stress. These results suggest that the carbamylation of matrix proteins participates in the remodeling of the vascular wall and leads to the alteration of its mechanical properties
Cheng, Bolin. "Etude des transitions de phase et des mouvements de parois de domaines dans les céramiques ferroélectriques à base de titanate de baryum par mesures du module élastique et des pertes mécaniques." Lyon, INSA, 1996. http://www.theses.fr/1996ISAL0068.
Full textIn this work we have studied the anelastic behaviors of barium titanate ceramics. We have measured the mechanical losses and the longitudinal and the shear elastic modulus as function of temperature from - l80°C to 150°C. The mechanical vibration frequencies used are between 0. 01 Hz and several kHz. We have also complete the frequency range to 100 kHz par the dielectric measurements. The phase transitions are perfectly identified by the anomalies of elastic modulus. The measurements of elastic modulus is more sensible than the permittivity to the phase transitions. The relaxation peaks as function of temperature are observed in the ceramics no-doped with large grains sizes. All of those peaks can be analyzed by the Arrhenius relationship. The activation energy of the peaks are 0. 29, 0. 47, 0. 68, and 0. 92 eV, respectively, and the relaxation time is about 10E-14 s. For all the peaks. Those peaks could be explained by the interaction of point defects with the movement of domain walls. The temperature of the relaxation peaks can pass from one phase to another one for different vibration frequencies. Which suppose that certain configurations of domain structures have a memory effect. In the doped samples, the measurements of elastic modulus allow us to study the influences of dopants on the temperatures of phase transitions with high precision. For the ceramics doped with Nb (donor) and Co (acceptor) the mechanical and dielectric losses are reduced in the tetragonal and orthorhombic phases so the variations of the permittivity conform to the X7R specification. For the relaxation peak observed in the ceramic doped with Co, the activation energy is about 0. 3 eV and can be associated with the diffusion of oxygen vacancy. The relaxation peak in the ceramic doped with Nb (2-4 at %) could be associated to the diffusion of simple ionised barium vancany
Sahed, Hocine. "Détection et étude de la perturbation dûe à un défaut dans la paroi d'un réservoir cylindrique sous pression." Valenciennes, 1995. https://ged.uphf.fr/nuxeo/site/esupversions/f640c3d5-db1c-4f28-b1d6-8a393ac30dd2.
Full textThis dissertation deals firstly with a theorical analysis of flaw detection and secondly with the singularity problem in a cylindrical, pressurized vessel (tank). Flaw detection by acoustic emission and elastic waves scattering is discussed within the context of non-destructive inspection. Firstly, the position of the physical and mathematical problem is given. From the solution (Existence and Uniqueness), we express the radiated field (displacement/stress), in a zone far away from the propagation medium. Secondly, under some assumptions about the tank, we consider an infinite, isotopic , elastic medium. Hence, using Fourier transforms, an integral equation is obtained for an elastic wave scattering. We discuss some type of problems. In the framework of Sobolev space, an alternative formulation is well posed. Thirdly, our last interest is in the perturbation problem due to a defect in the cylindrical tank. Within the shell theory, we reduce the problem to a mixed boundary value problem. Using an inverse integral transform, a Fredhom system of integral equations is established. Thus, the asymptotic analysis and the resolution allow us to characterize the perturbed state of the vessel and to determine the parameters of singular fields. A stability criterion, with an energetic approach, is built in order to flaw propagation in the tank. Finally, some subjects for further research in this domain of investigation are suggested : The behavior of a vessel under propagation crack conditions; The oscillations during the process of crack propagation; State of the vibration mode in the vessel perturbed by a flaw; Theoretical study on the conditions of the arrest, initiation, bifurcation of the crack
Aillaud, Krakowiak Cécile. "Elaboration et validation d'une méthode de calcul élastique et inélastique des tuyauteries, basée sur une modélisation en poutre et prenant en compte le chargement thermique dans la paroi." Poitiers, 1989. http://www.theses.fr/1989POIT2338.
Full textAired-Selmani, Leila. "Caractérisations théoriques et expérimentales d'agents de contraste ultrasonore ciblés." Thesis, Tours, 2013. http://www.theses.fr/2013TOUR3301/document.
Full textSince they were introducted, contrast agents have revolutionized the ultrasound imaging. They are composed of tiny gaseous microbubbles and when injected intravenously into the blood, they improve the ultrasound image. Targeted imaging is another application based on the physical characteristics of contrast agents. This approach is based on the ligands incorporation into the microbubbles shell. The microbubble attach to the molecular factors overexpressed by endothelial cells, covering the inner wall of blood vessels. To distinguish these microbubbles from those freely circulating, attached microbubble have to produce an acoustic signal that is sufficiently strong. However, the low microbubbles adhesion induces a decrease of the acoustic signal. To make it possible, it is important to determine the effect of the elastic wall on their acoustic response. This thesis aimed to study the effect of elastic walls on the ultrasonic behavior of targeted microbubbles. First, a theoretical model describing a wall with finite thickness was developed. It has been shown that the scattered echo amplitude by a microbubble near a wall with finite thickness is small in comparison to the echo from a microbubble located in an infinite fluid. Furthermore, and in order to account for the effect of blood vessel wall, the mechanical properties of the wall have been incorporated into the model. The results showed that the resonane frequency of a microbubble near the wall is higher than the resonanace of the same microbubble in an infinite medium. Subsequently, we studied the effect of three types of walls on the microbubble behavior including the wall of OptiCell chamber which is commonly used in ultrasonic experiments. We have shown that microbubbles near the OptiCell wall diffuses a higher echo than those far from the wall when the excitation frequency is above the microbubble resonance frequency. On the other side, we observed that small microbubbles to the presence of the wall. Afterward, we developed a model describing a microbubble attached to the wall. We have shown that the microbubble in direct contact with the wall induces a decrease of the echo amplitude compared to the same bubble in infinite liquid. Moreover, the direct contact of the bubble with the wall generates an increase of the resonance frequency relative to a bubble without direct contact. Finally, an experimental study has shown the advantage of the subharmonic imaging to differentiate attached microbubbles from the free ones
Clair, Bruno. "Etude des propriétés mécaniques et du retrait au séchage du bois à l'échelle de la paroi cellulaire : essai de compréhension du comportement macroscopique paradoxal du bois de tension à couche gélatineuse." Phd thesis, ENGREF (AgroParisTech), 2001. http://tel.archives-ouvertes.fr/tel-00008857.
Full textLes fibres à couche G semblant être le moteur du fort retrait axial du bois de tension, une observation du comportement au séchage à l'échelle de la paroi cellulaire est mise au point. Des observations en microscopie électronique à balayage et en microscopie à force atomique montrent que, en plus de son fort retrait transverse, la couche G a aussi un très fort retrait longitudinal. Une approche simple de modélisation par éléments finis est proposée pour rendre compte des phénomènes observés.
Afin de récolter des données pour la modélisation, deux outils complémentaires sont mis au point pour une estimation des propriétés élastiques et viscoélastiques des couches de la paroi cellulaire. La réalisation d'un microscope acoustique en transmission et l'utilisation de la microscopie atomique en mode contact vibrant permettent d'envisager la caractérisation quantitative des propriétés mécaniques à l'échelle de la paroi dans différentes conditions d'humidité.