Literatura científica selecionada sobre o tema "Matériaux à gradient fonctionnel – Vibrations"
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Teses / dissertações sobre o assunto "Matériaux à gradient fonctionnel – Vibrations"
Koutoati, Kouami. "Modélisation numérique du comportement statique et vibratoire des poutres sandwich viscoélastiques à gradient de propriétés". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0290.
Texto completo da fonteThis thesis proposes a numerical tool for the static and dynamic study of viscoelastic structures made of Functionally Graded Materials (FGM) for vibration control by passive damping. The objective is to make available to engineers a generic code based on the finite element approach for sizing calculations on FGM sandwich beam with viscoelastic core for applications requiring lightness and good thermal and mechanical resistance such as aerospace, automotive and nuclear. To reach this objective we first proposed a numerical model for the static and free vibration study of FGM sandwich beams with elastic behavior. This finite element model is implemented in the Matlab code environment. Using this code, we compare different beam theories for different geometric properties and boundary conditions. Thus, the limit of the classical beam theory in the study of short structures is highlighted. Also with this numerical model, the study of axial-bending and axial-rotation coupling is possible. From this, it is shown that FGM structures are very sensitive to spatial coupling and warping effects because of the non-symmetrical distribution of the material in their cross sections. In the proposed code, the resolution of the vibration problem is possible using classical eigenvalue and eigenvector problem solving methods. Then to introduce passive damping in the FGM sandwich structure, we proposed a sandwich beam model with FGM materials faces and viscoelastic materials core. This model is also implemented in the Matlab language and proposed as a generic tool. The interest of this numerical tool lies in its ability to compute the modal properties as well as the behavior of the viscoelastic FGM sandwich beam while taking into account the frequency dependence of the viscoelastic behavior, the boundary conditions and the axial-bending and axial-rotation coupling specific to FGM materials. The free vibration problem is non-linear in this case due to the material non-linearity induced by the soft layer. In the proposed code, the resolution of this problem is possible thanks to the coupling of the homotopy technical, the asymptotic numerical method and the automatic differentiation. Through this work, the contribution of FGM materials in the improvement of the damping power of structures is highlighted. In the continuation of the work, we propose a finite element formulation to compute the amplitude of forced vibrations of viscoelastic FGM sandwich structures. The resolution of the forced vibration problem is possible by using the bandwidths method. A study on the contribution of FGM materials in the reduction of vibration amplitudes is carried out for different viscoelastic laws. It is proved in this study that by a direct control of the composition gradient of FGM materials it is possible to optimize the damping power of structures even for low frequency modes for which classical composite materials have a damping power requiring improvement
Dammak, Yosra. "Caractérisation numérique et expérimentale par ultrasons de matériaux à gradient fonctionnel". Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1039/document.
Texto completo da fonteThis thesis focuses on the study of multilayered and FGM systems (FGM : Functionnally Graded Materials). The main purpose of this type of materials is to obtain deposits with new and innovative features and to increase the fracture toughness. From now on, FGM have been used in various high technology applications.A multilayer system with a composition gradient of copper and nickel was studied experimentally by the application of the laser ultrasonics (LU) technique which was coupled to a theoretical study based on the ordinary differential equations (ODE) and the Stiffness Matrix Method (SMM). This PhD thesis is organized around four chapters. The first chapter is dedicated to a theoretical study of the propagation behavior of surface acoustic wave (SAW) in a multilayer system with à gradient of properties. Thus, the numerical methods developped for the piezoelectric materials (FGPM) are presented. The second chapter is devoted to describe the setup for making the samples used in this study which were obtained by sputtering technique. The third chapter presents the experimental study dedicated to the measurement of surface wave velocities in many crystal orientations. The last chapter of the manuscript presents experimental results, compared to the theoretical results, describing the dispersive behavior of submicrometer multilayers
Froehly, Luc. "Nouveaux matériaux à gradient d'indice pour l'optique : étude des procédés de fabrication existants et développement de méthodes de caractèrisation". Saint-Etienne, 2000. http://www.theses.fr/2000STET4005.
Texto completo da fonteAudouard, Lisa. "Conception et caractérisation de matériaux ultra haute température à gradient de propriétés". Electronic Thesis or Diss., Bourgogne Franche-Comté, 2023. http://www.theses.fr/2023UBFCA019.
Texto completo da fonteThe development of a new green ergol prototype for satellite repositioning engines requires more severe thermal and environmental conditions for combustion chamber materials than is currently the case. As a result, alternative materials known as functionally graded materials (FGM) have been developed for several years as part of an ONERA-CNES-ICB study. The aim of this thesis is to pursue the development of this type of ceramic/metal gradient material, in order to optimize its design and ensure that it can be used up to 2400 °C in the presence of water vapor. Firstly, different configurations of FGM developed by air plasma thermal spraying (APS) were tested under vacuum laser heat flux up to 2350 °C. By modelling the cracking of these materials when subjected to thermal shock, the link between the observed degradations and the FGM configurations was better established. In particular, it has been shown that increasing the thickness of the ceramic on the FGM surface is responsible for the appearance and propagation of deeper, deviated cracks.Secondly, the possibility to use such FGM under an oxidising atmosphere at ultra-high temperature was studied through two experimental set ups. The first one is a laser test bench which allowed to assure the resistance of the materials submitted to repeated thermal schocks up to 1800 °C in presence of water vapour. The tested materials presented an appropriate behaviour under the tested conditions. The degradation mechanisms related to FGM oxidation have been identified and compared from one FGM configuration to another and linked to the tested conditions. The second one permits to qualify the behaviour of FGM in the H2/O2 flame of a combustion chamber. Thus, the tested conditions were relatively close to the ones of the intended application. No major degradation was observed after the combustion chamber tests, which demonstrates the potential of this type of FGM for the application.In parallel, a study was carried out about the improvement of the ceramic part of the FGM. Indeed, the thermal expansion coefficient of the chosen metal is twice lower than the one of the chosen ceramic. Thus, and despite the presence of graded layers in-between the metal and the ceramic, high thermomechanical stresses occur at the interfaces between the different layers of the FGM. Thus, a key point of this study consisted in the understanding of the influence of the ceramic composition, and in particular of the amount and nature of the rare earth oxide, on the thermal expansion coefficient. In addition, ionic conductivity and thermal conductivity measurements most accurately reflect the role of thermal and environmental barrier coating of the pure ceramic layer upon the FGM. It has been shown that high content Lu2O3 based compositions are the most promising to be used for the ceramic composition of the FGM. The last part of this thesis was dedicated to study the possibility to heal the cracks observed in the ceramic, which came either from the thermal treatment, either from the thermal tests. Thus, an yttrium disilicate was introduced in the pure ceramic layer of the FGM directly during the elaboration process with APS. Its influence on the resistance of FGM under harsh thermal and environmental conditions was finally reported. In particular, the presence of this disilicate is responsible of chemical transformations in the FGM during high temperature tests
Madec, Clémentine. "Elaboration de matériaux à gradient de fonction céramique / métal par SPS pour la protection balistique". Thesis, Dijon, 2016. http://www.theses.fr/2016DIJOS057/document.
Texto completo da fonteThe objective is to improve ballistic performance of armors. A perfect armor combines ductility to resistto the impact and high hardness to stop projectile’s fragments. However, such an association of properties is inconsistent witha single material. The solution is to perform a functionally graded material (FGM) with a ductile metal at the back side of thesample and a hard ceramic on the top side. Non-conventional technologies like Spark Plasma Sintering allow joining orsintering all types of materials with different and additional properties. Furthermore, with this technique, high heating ratescan be achieved, limiting grain growth and resulting in a fine microstructure. The goal is to study joining conditions or cosinteringof such materials (in this case, Al2O3 and Ti), as well as the resulting microstructure on the ballistic efficiency.The first part of the study focused on the characterization of alumina and titanium. Five powders of alumina werestudied from a sintering point of view. Three of which were selected because of their interesting microstructures, close indensities and grain sizes. These ceramics have been characterized mechanically (hardness, toughness and strength) andballistically. One of them is adopted to realize FGM. Titanium, sintered with the same conditions, unfortunately, doesn’t haveexpected properties (absence of ductility).The second part of the work showed that the preparation of FGM without cracks from Al2O3 and Ti only ischallenging, with an interlayer with one or more layers. The strong affinity of Ti with oxygen (formation of oxides orinsertion) with C (forming carbides) and its reactivity with alumina (forming intermetallics) make the FGM brittle and enablethe release of residual stresses during the process. By adding a low amount of nickel (more ductile and less reactive withoxygen and titanium) in composites, FGMs almost without cracks were obtained. The latter were evaluated ballistically
Boulvert, Jean. "Traitements acoustiques à porosité contrôlée pour atténuation optimale". Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1033.
Texto completo da fonteThis thesis exploits some of the new possibilities offered by additive manufacturing to design and optimize treatments for sound attenuation consisting in porous materials. Additive manufacturing allows to control individually each pore of a material. The porous treatment design process is turned upside down: instead of searching through a catalogue of existing materials to solve a problem, it is possible to directly design the right material by adjusting its microstructure. This research is part of a plan to reduce aircraft engine noise but extends beyond the aeronautical field, both theoretically and in terms of possible applications. A predicting method of the acoustic behaviour of porous materials produced by additive manufacturing and taking into account the impact of manufacturing defects is first introduced. Porous materials with controlled graded properties are then studied. A method for optimizing microstructural or manufacturing parameters is developed. The ability of graded porous materials to attenuate frequencies too low to be attenuated by non-graded materials is then proven and the optimal gradient for broadband attenuation is defined. The impact of the wall thickness of the pores along with the impact of transverse propagation inside porous materials is studied. Finally, a metaporous treatment allowing broadband and sub-wavelength absorption is developed. The results of this research can be applied to create porous treatments with a high noise attenuation. The analytical and numerical models used in this research are based on the hypothesis of porous materials acoustically behaving as equivalent fluids. The results are physically analyzed and experimentally validated through impedance tube testing of specimens produced by additive manufacturing
Le, Duc Trung. "Modèle d'endommagement à gradient : approche par homogénéisation". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066662/document.
Texto completo da fonteThe aim of this work is to propose a general framework to obtain a gradient damage model from the micro-structural level. It is based, firstly, on the homogenization method to derive an effective medium from the microstructure, and secondly, on the variational formulation of a damage evolution law from the homogenized medium. We propose, as a first step, an approach based on asymptotic expansion and the variational method for homogenizing a periodic elastic medium. To model the localization of damage, this approach has been extended to a quasi-periodic heterogeneous medium. From an example of quasi periodically micro-cracked solid, we obtain an elastic energy that not only depends on the gradient of the damage but also the strain gradients. Based on the principle of energy minimization, we propose the construction of a gradient damage model from the elastic energy homogenized in the second part. By adding some hypothesis to simplify the model, we can construct localized damage and strain solutions in closed form. Finally, a numerical resolution scheme, which is based on an alternate minimization algorithm, is proposed for the one-dimensional traction bar test. From the numerical results, the advantages and disadvantages of the model are discussed
Maruani, Jonas. "Contrôle actif des vibrations de structures élancées FGPM". Thesis, Paris 10, 2019. http://www.theses.fr/2019PA100062.
Texto completo da fonteThe aim of this thesis is to show the feasibility and the efficiency of active vibration control by structures made of functionally graded piezoelectric materials (FGPM). One bloc structure, made of FGPM, with piezoelectric properties embedded, is used to replace classical intelligent structures (a host structure equipped with piezoelectric patches) and to remove their disadvantages (stresses concentrations near interface, delamination of patches, …).This study focuses on the FGPM’s modelization, in particular on the graded behavior laws and on the development of finite elements of FGPM beams and plates. Two finite element are implemented, a beam element based on Timoshenko’s kinematics and a plate element based on an adaptive kinematics. Both elements have a numerical layers approximation for the electrical potential. These two elements are used for active vibration control simulations. In the beam case, the system is governed by a linear quadratic regulator. Otherwise, for the plate a fuzzy decentralized regulator is developed and used. Both systems beam and plate are observed thanks to a Luerberger’s observer. Static studies show the behavior of FGPM depending on the material gradation. In addition, active vibration simulations show the feasibility of control with both systems and the ability of fuzzy regulator to accommodate to sudden changes on external perturbations
Gozdecki, Nicolas. "Nouveaux alliages de titane à gradient de propriétés pour l'implantologie dentaire : approches expérimentale et numérique". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066710.
Texto completo da fonteIn the field of biomaterials, titanium alloys are among the most attractive materials for osseointegrated implants due to their high biocorrosion resistance, increased general biocompatibility and specific mechanical properties. Among these properties, low elastic modulus of titanium alloys has attracted much attention regarding the transmission of functional loads from the implant to the surrounding bone. The aim of this work consists in developing functionally graded materials, with careful attention to the thermomechanical treatments. In one hand, this allows us to obtain a gradient of elasticity in bulk materials and in the other hand, a gradient of grain sizes. This is possible thanks to the reversible martensitic transformation β ↔ α’’ and also to the α phase dissolution during flash treatments. The microstructural scale is also controlled in order to develop homogeneous materials at the nanoscale, thermally stables, and exhibiting superplasticity at low temperatures. These results are thought to be good strategy to avoid the use of SPD processes. A complete characterization of these new materials is performed with the combination of SEM, TEM and XRD analyses to appreciate the modifications of the microstructures and grain sizes. Values of elastic modulus are obtained by tensile tests, and locally determined with the use of instrumented microindentation measurements
Leblond, Timothée. "Calcul de gradient sur des paramètres CAO pour l’optimisation de forme". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC017/document.
Texto completo da fonteIn this manuscript, we present a shape optimization method based on CAD parameters such as lengths, angles, etc. We rely on gradient-based optimization techniques. The sensitivity of the objective function, with respect to the mesh nodes position, is provided by an adjoint solver considered here as a black box. To optimize with respect to CAD parameters, we focus on computing the sensitivity of the nodes positions with respect to these parameters. Thus, we propose two approaches based on finite differences. The first method uses a harmonic projection to compare in the same space the initial mesh and the one obtained after a change of the set of CAD parameters. The developments presented in this manuscript open up new doors like the application to shapes with multiple borders such as exhaust manifolds. We also developed an interpolation method suitable for this comparison. The entire process is automated, and we demonstrate the entire effectiveness on internal aerodynamics industrial applications. The second method is directly based on the CAD geometries to assess this sensitivity. To perform this comparison, we use the intrinsic definition of the patches in the parametric space (u;v). Through the use of the exact coordinates at any point on the surface provided by the CAD, we avoid using an interpolation to get the best calculation accuracy possible. However, unlike the first method, it requires to identify the correspondence between patches from one shape to another. An application on an external aerodynamics academic case was made. The relevance of the first method is demonstrated on a representative multi-objective case, which facilitate its deployment use in an industrial environment. Regarding the second method, we showed its great potential. However, further developments are needed to handle more advanced cases. Because they are independent of the mechanical solver and the number of parameters, these methods significantly reduce product development time, particularly by allowing large and multiphysics optimization
Livros sobre o assunto "Matériaux à gradient fonctionnel – Vibrations"
Sobczak, Jerzy, e Ludmil Drenchev. Metal based functionally graded materials: Engineering and modeling. [Saif Zone, Sharjah, U.A.E.]: Bentham eBooks, 2009.
Encontre o texto completo da fonteFunctionally Graded Materials (fgms). Taylor & Francis Group, 2021.
Encontre o texto completo da fonteKumar, Vineet, Nandita Dasgupta, Shivendu Ranjan e Praveen Guleria. Functionalized Nanomaterials II. Taylor & Francis Group, 2021.
Encontre o texto completo da fonteFunctionalized Nanomaterials II: Applications. Taylor & Francis Group, 2021.
Encontre o texto completo da fonteKumar, Vineet, Nandita Dasgupta, Shivendu Ranjan e Praveen Guleria. Functionalized Nanomaterials II: Applications. Taylor & Francis Group, 2021.
Encontre o texto completo da fonteKumar, Vineet, Nandita Dasgupta, Shivendu Ranjan e Praveen Guleria. Functionalized Nanomaterials II: Applications. Taylor & Francis Group, 2021.
Encontre o texto completo da fonteShen, Hui-Shen. Functionally Graded Materials. Taylor & Francis Group, 2019.
Encontre o texto completo da fonteDey, Arjun, e Anoop Kumar Mukhopadhyay. Nanoindentation of Natural Materials: Hierarchical and Functionally Graded Microstructures. Taylor & Francis Group, 2018.
Encontre o texto completo da fonteNanoindentation of Natural Materials. Taylor & Francis Group, 2018.
Encontre o texto completo da fonteDey, Arjun, e Anoop Kumar Mukhopadhyay. Nanoindentation of Natural Materials: Hierarchical and Functionally Graded Microstructures. Taylor & Francis Group, 2018.
Encontre o texto completo da fonte