Dissertations / Theses on the topic 'Approches expérimentales et numériques'
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Crambuer, Romain. "Contribution à l'identification de l'amortissement : approches expérimentales et numériques." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00957320.
Full textRupin, Matthieu. "Cavité réverbérante et résonateurs sub-longueur d'onde : approches numériques et expérimentales." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY082/document.
Full textThis thesis is divided into two parts. First, we present a new technique for focusing waves with one emitter in reverberant cavity (OCIF) inspired by inverse filter algorithm. Through the experimental study of reverberant cavities in the field of ultrasound, we demonstrate the ability of the OCIF to optimize the focusing no matter what type of cavity (ergodic type or not). In a second part, we investigate the propagation of elastic waves in a system formed by a set of aluminum rods glued to a thin plate of the same material. These rods form a set of quasi-punctual resonators in the propagation plane of waves. It is possible to arrange them periodically or randomly on a subwavelength scale. The metamaterial thus formed shows a complex wave field within it, including the presence of wide prohibited frequency ranges (bandgaps). The experimental and numerical approaches described in this manuscript show the existence of both flexural and compressional resonances in the resonators. Added to the presence of a conversion of a portion of the energy from the $A0$ Lamb mode to the $S0$ one in the plate, such a complexity makes this type of metamaterials, quite unusual objects at the mesoscopic scale
Guinot, Florent. "Interactions houle-courant en bathymétrie variable : approches numériques et expérimentales." Brest, 2010. http://www.theses.fr/2010BRES2069.
Full textMarais, Louise. "Caractérisation mécanique de la paroi artérielle pathologique : approches expérimentales et numériques." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC0084.
Full textVascular pathologies are generally accompanied by a remodeling of the arterial wall that may lead to modifications of its stiffness and mechanical behavior. The goal of this thesis is to propose methods of mechanical characterization allowing to detect the changes in arterial mechanical properties in the case of two pathologies: abdominal aortic aneurysm (AAA) and arterial hypertension (HTA). The first study consisted in evaluating in vitro the arterial functional modifications in the case of an AAA obtained by the rat xenograft model which reproduces several biological features of the human pathology and is used to develop cell therapies. First, the assessment of regional variations in mechanical properties of aneurysmal tissue was conducted by carrying out traction tests on rings from AAAs. Then, extension-inflation tests were conducted on the vascular structure for loading conditions replicating those observed in vivo. In each case, an inverse method associated with a numerical finite element model was developed to identify the material parameters of vascular tissue. In the second study, arterial stiffness was measured in vivo for a population of hypertensive patients and healthy subjects using two non-invasive methods which were developed and optimized: ultrafast imaging of the pulse wave and shear wave elastography of the arterial wall. These two methods are based on an ultrafast ultrasound scanner. Thus the local pulse wave velocity on a segment of the carotid artery was assessed, as well as the propagation speed of shear waves created in the arterial wall at several moments during the cardiac cycle. Both in vitro and in vivo approaches enabled to evaluate some changes in mechanical properties of the arterial wall in pathological cases. Although all the biological mechanisms of AAA and HTA are complex, this work provides a contribution to a better understanding of vascular pathologies and can thereby assist in the choice or development of adapted treatments, from both a pharmacological point of view, and within the context of new cell therapies
Nguyen, Tuan Anh. "Approches expérimentales et numériques pour l'étude des transferts hygroscopiques dans le bois." Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0034/document.
Full textIn civil engineering constructions, the development of timber structures requires today to managers works some diagnostic tools and monitoring systems to monitor pathologies (excessive deflections, cracks, biological attack, etc.) but also to control moisture content in the element sections. In the last context, the proposed work in this PhD thesis is the development of a tool for characterization of the moisture content map in the cross sections of structural elements. Studied method is based on the resistivity measuring, comprising a measuring head (resistivity meter) associated with many connected probes in a multiplexed system, and an inverse method implemented in a finite element software. In the first part, it is studied the techniques of characterization of diffusion properties in wood samples characterized by orthotropic and nonlinear behaviors according to average moisture content measurements (gravimetric method) and spatial profiles gamma densitometer measures. It is shown that the coupling of the two measurements provides the intrinsic properties with more reliability and more robustness. The second part deals with the development of an experimental protocol in order to achieve 1D and 2D mapping of the moisture content field in a cross section. The technique is based on the generalization of multiplexed resistivity geophysical methods used in the study of stratified soils with 2-dimensional geometries. The algorithm is based on the coupling between the resistivity measurements and an inverse multiplexed analysis implemented in a finite element code. The 1D solution provides spatial profiles which can replace gamma densitometer measures. For a selected section, 2D profiles allow estimating the moisture content field at any point and thus provide a time tracking of moisture profiles
Amaied, Emna. "Effet du vieillissement cutané sur la perception tactile : approches expérimentales et numériques." Lyon, Université de Lyon, 2016. http://www.theses.fr/2016LYSEE003.
Full textThe aim of this thesis is to study the effect of aging on the viscoelastic properties of the finger and the tactile perception. The understanding of tactile perception related to age requires further development of experimental and Numerical approaches. The skin tissue as sensory organ is presented. To asses the effect of age and gender effect, an xperimental device designed and producted in the laboratory is used. This device allows soliciting the skin of the finger in vivo, with a controlled air pressure and identifying the viscoelastic parameters. This expérimental study allowed calculating of the mechanical properties of the finger pad. The experimental study is accompanied with a multilayer axisymmetric two-dimensional FEM model of the human finger developed to reproduce the test creep. This model was used to calculate the instantaneous modulus of elasticity of each layer of the finger by a reverse approach. An experimental study of tactile acuity was conducted of the human finger. This shows a deficit of tactile acuity of aged subjects. This study identified the threshold of tactile acuity in each age group and allowed the understanding of the interactions of the sensory receptors with the stimulus. The study of the effect of aging on the active touch with an experimental approach was conducted. An innovative device developped in the laboratory, was used to quantify vibrations induced when a human finger explores a textured surface. These vibrations are the source of excitation of sensory receptors and have a big role in the sensation of active touch. The effect of age shows a significant decrease in vibration level. The numerical study in the last chapter was used to study for the first time the deficit due to aging in terms of vertical and special resolutions of textured surfaces
Sinou, Jean-Jacques. "Dynamique non-linéaire des structures complexes, fixes et tournantes. Approches théoriques, numériques et expérimentales." Habilitation à diriger des recherches, Ecole Centrale de Lyon, 2007. http://tel.archives-ouvertes.fr/tel-00260913.
Full textDans une première partie, le rôle joué par les phénomènes non-linéaires en dynamique des structures et le développement de méthodes non-linéaires sont illustrés à travers trois axes de recherche.
Le premier axe porte sur la stabilité et la dynamique non-linéaire des systèmes frottants. On se propose de déterminer les zones stables et instables, ainsi que les niveaux vibratoires lorsque le système dynamique non-linéaire est sujet à une instabilité de type flottement. Pour ce faire, des approches se basant sur des réductions et/ou approximations des solutions sont développées et validées sur des exemples industriels (freins automobile et aéronautique).
Le deuxième axe se focalise sur la détection des fissures dans les systèmes tournants et cherche à définir des critères de détection des fissures se basant sur les réponses dynamiques non-linéaires (résonances sous-harmoniques, ordres, orbites, interaction fissure-balourds,...). Des approches théoriques, numériques et expérimentales sont menées en parallèle afin de statuer sur la pertinence et la robustesse des critères proposés.
Le troisième axe s'intéresse à la problématique de la dynamique non-linéaire des systèmes mono et bi rotor à travers des approches numériques et expérimentales. Ces recherches proposent de statuer sur la prise en compte des phénomènes non-linéaires et de la modélisation des organes associés lors du dimensionnement des systèmes tournants à partir de l'étude du comportement vibratoire (diagramme de Campbell, réponses non-linéaires et orbites, évolution des ordres,...).
Dans un second temps, l'accent est porté sur les perspectives de recherches et sur les ouvertures scientifiques envisageables sur des thématiques transversales.
Compère, Fabrice. "Transport et rétention de particules argileuses en milieu poreux saturé : approches expérimentales et numériques." Poitiers, 1999. http://www.theses.fr/1999POIT2301.
Full textDiouf, Abdou khadre. "Approches numériques et expérimentales pour l’étude des écoulements dans les laboratoires géologiques sur puce (GLoCs)." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0951/document.
Full textThis thesis work is included within the ANR CGS µLab projet, which aims to understand thefundamental mechanisms involved in the deep storage processes of CO2 from on-chip geological laboratories(GLoCs - geological labs on chip) to reproduce the pressure and temperature conditionsof deep geological environments. Besides experimental understanding, the contribution of numericalmodeling approaches appears essential in order to define models allowing to predict in particularthe maximum storage capacities based on the characteristics of the reservoirs (porosity, permeability,temperature, pressure, geochemistry), and the injection process (flow rate, composition). In thiscontext, this work has two main goals : (i) to associate experimental imaging and numerical modelingto simulate non-reactive flows in model porous media on chip ; and (ii) to follow experimentally thestructural evolution of a 3D porous medium undergoing a reactive flow. In order to address to thesegoals, the approach we have proposed is divided into two parts. In the first part, we carried out the3D modeling of the permeabilities of GLoCs by taking volume averaging. To do this, we first verifiedthe behavior of a GLoC according to its number of plots rows by studying a diffusion problem ona nested mesh that we have implemented from a GLoC binary image to reduce computation time.Then, we updated our permeability code, which solves the closure problem of flow, by analyticallycalculating in 3D the stability criterion that takes into account the anisotropy of GLoC geometry. Wethen processed the 2D digital images of the GLoCs before proceeding with the generation of their3D representative elementary volumes. Finally, we have simulated the permeabilities of GLoCs beforecomparing them with the experimental results and those obtained with the PHOENICS software. In asecond part, we have developed an experimental set-up to recreate 3D reactive porous media within amicrofluidic channel (fixed packed bed of calcium carbonate - CaCO3 microparticles). Using the X-raylaminography of the ESRF line ID19, we have observed on reconstructed 2D images the dissolutionphenomena occurring during the successive injection of constant volumes of non-equilibrium solution.This proof of concept has opened new possibilities for using this methodology to acquire kinetic dataon reactive front phenomena in porous media
Jaisle, Nicolas. "Contraindre la fusion partielle dans les intérieurs planétaires en combinant les approches numériques et expérimentales." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALU013.
Full textThe study of partial melting processes in planetary interiors is of prime importance to understand planetary evolution mechanisms. This is even more true when considering the increasing number of exoplanetary discoveries which likely acknowledged a high variety of histories. A main experimental tool for to study deep planetary interior conditions is the diamond anvil cell (DAC), allowing to raise pressures on micron-sized samples up to hundreds of GPa and at temperatures up to thousands of Kelvins. The study of sample’s physical properties such as their phase change pressures and temperatures (P,T) can be analyzed in X-ray generating synchrotron facilities, using the X-ray diffraction (XRD) properties of minerals. Those experiments may yet suffer from the continuous laser heating technique which generates strong temperature gradients within the samples and may lead to chemical migration in the heated zone. The sample in-situ analysis is then achieved on a composition diverging from the initial one which does not necessarily correspond to what was intended to be measured. This thesis suggests a new experimental approach consisting in using a short and intense (250 ns) laser heating pulse in order to limit that chemical migration. This experimental setup was tested on iron alloys of the Fe-Si-O ternary system, results on such compositions being for instance applicable on in the context of Earth’s liquid outer core crystallization. Our experiments are run at the European X-ray Free Electron Laser (EuXFEL) facility which generates a high brilliance pulsed X-ray source (series of 30 fs pulses at frequencies up to 4.5 MHz (one pulse each 221.5 ns). Combined to the µs fraction laser heating, the EuXFEL experiments allow to obtain a temporal resolution of the sample evolution during its cooling, allowing to observe crystallization sequences. A streak optical pyrometry (SOP) surface temperature measurement is achieved simultaneously to the XRD with time resolution below the µs-scale. However, measurements achieved at the EuXFEL do not allow to fully resolve the extent of the phenomena occurring during experiments. To compensate this lack of information, we developed a numerical model based on the finite element method (FEM) to reproduce the achieved experiments. This model uses the material properties (such as ρ, K, G, κ, Cp and latent heat) at the experimental pressure and temperature conditions including their P,T dependencies when available. Equations of state (EoS) related variations where included in the model for the related parameters. To reproduce the experiments, the model values are adjusted by minimizing the mean error compared to the SOP data. Combining experimental XRD with best-fitting model temperatures, it is possible to get back to the P, T conditions during the samples phase change. In addition, the FEM furnishes temperature and pressure maps highlighting e.g. sample internal gradients and allowing to evaluate the degree of homogeneity of P and T, both assumed to be critical parameter in chemical migration. Models allow as well to calculate the constraint distribution in the DAC assemblage which can be an important factor in certain conditions. Finally, experiments directly using X-rays to heat the sample were achieved, analyzed and reproduced by modelling. Using the models, the possibility of deducing material properties such as thermal conductivity from best fits to experimental data are explored
Letty, Camille. "Etude d'une flamme en V diphasique : Approches expérimentale et numérique." Rouen, 2008. http://www.theses.fr/2008ROUES036.
Full textThis work deals with V-shaped two-phase flames stabilised in a pseudo-laminar or moderated turbulent flow. Some gaseous fuel is also injected to help turbulent flames stabilisation. An experimental approach and a numerical approach (Direct Numerical Simulation) are conducted simultaneously. The same tools are used for post-processing of experimental and numerical data. The flow is experimentally charaterised in term of droplet size distribution (Malvern), turbulent properties (PIV), qualitative fuel repartition (PLIF on acetone) and droplet temperature distribution (rainbow refractometry). The gaseous flow is numerically defined by Navier-Stokes equations in an eulerian framework. Two-way coupling is use to determine interaction of gaseous and liquid phases. A lagrangian solver is used for the dispersed phase. Chemical kinetics is derived from complex chemistry results computed with Chemkin (San Diego mechanism for n-heptane with acetone oxydation reactions). Flame front is artificially thickened (Flame thickness factor and efficiency function). This enables reduction of the mesh size which is time saving. Mean geometrical and local properties of the flame front are determined: morphology, flame angle, progress variable, flame brush evolution, curvature and strain rate. The mean flame angle is used to ajust DNS parameters. The evolution of the droplets mean temperature is presented for different turbulent conditions and from experimental and numerical approaches. DNS fields are used to develop a calculation method of strain rate from experimental data following tensorial method
Du, Rou. "Mise en forme à chaud de tôles fines en alliage AA 5383 : Approches expérimentales et numériques." Thesis, Paris, ENSAM, 2019. http://www.theses.fr/2019ENAM0030/document.
Full textAluminum alloys have been extensively used in the automotive and marine industry due to the advantages of low density, high strength to weight ratio and good corrosion resistance. Major challenge of their application lies in the ability to form deep-drawing shapes. Superplastic Forming is widely used to produce this type of parts. However, high forming cycle time due to the low forming strain rate limits their wide application. The present dissertation focuses on hot forming strategies to produce deep drawing parts from AA5383 aluminum thin sheets. The main objective is to reduce the forming time without sacrificing the part integrity. Firstly, the hot deformation behavior of the AA5383 alloy is experimentally characterized. An experimental campaign, including uniaxial tension, notched tension, shear and free bulging tests, is performed to cover an important range of temperatures (623~723 K) and strain rates (10-4~10-1 s-1). Then, the material models, such as a composite flow rule with the BBC2003 anisotropic yield criterion and the modified Mohr-Coulomb damage criterion, are developed and implemented in ABAQUS by using user subroutine. Finally, the numerical simulations of the gas forming processes are performed and compared with the corresponding experimental results
Elmeguenni, Mohamed. "Effet de la triaxialité sur le comportement et la rupture du polyéthylène haute densité : approches expérimentales et numériques." Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10035.
Full textIn a first part of this thesis, an experimental approach based on macroscopic measurements and microscopic observations (SEM and OM) led to a better understanding of damage mechanisms in high density polyethylene (HDPE) and its stress triaxiality sensitivity. In order to examine higher stress triaxiality values, cracked samples were experimentally examined in a second part. Based on the obtained results, the relevance of the fracture mechanics concepts to characterize the fracture toughness of HDPE was critically discussed. The investigation was performed using two well-known approaches of the fracture mechanics – J-integral and EWF – using different specimen configurations (SENB, CT and DENT). To gain insight into the strain field around the crack tip, digital image correlation method was used. The third part was focused on the demonstration of the relevance of ductile damage models (based on the void volume evolution as indicator of damage) to predict the mechanical and damage behaviour of HDPE and that, until complete failure. A special attention was paid on the stress triaxiality effects. Two failure criteria using complementary approaches were examined. These approaches were found relevant in the case of HDPE. Indeed, a good agreement was found between the numerical simulations and the experimental results in terms of overall response of axisymmetric samples (true stress-strain-volumetric response) and of cracked samples (load-displacement response) and in terms of local response corresponding to kinematics fields
Huchette, Cédric. "Sur la complémentarité des approches expérimentales et numériques pour la modélisation des mécanismes d'endommagement des composites stratifiés." Paris 6, 2005. http://www.theses.fr/2005PA066513.
Full textBriki, Amani. "Production de succinate par Corynebacterium glutamicum en microaérobiose : approches expérimentales et numériques, de l’échelle métabolique au bioréacteur." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0082.
Full textSuccinate is a diacid used nowadays as a building block in the synthesis of various molecules of interest. It is mostly produced by chemical synthesis. A part of succinate is industrially produced using a microbiological process. Corynebacterium glutamicum, a well-known industrial producer of amino acids, is able to produce organic acids, in particular succinate, under micro-aerobic and anaerobic conditions. The aim of this work was thus to understand the physiological response of C. glutamicum 2262 to change in oxygen supply conditions. Both experimental and numerical tools have been implemented. The first step was to identify, experimentally, the parameters influencing the physiological response of C. glutamicum 2262 during batch and continuous cultures. This approach allowed to identify oxygenation level and residual glucose concentration as key parameters for organic acids production. The ratio OUR/GUR was also defined as a relevant indicator of the physiological state of C. glutamicum 2262. It was observed that organic acids were simultaneously produced during micro-aerobic phase corresponding to ratio below 1, whereas, above this value, a maximal growth was obtained. The maximal succinate production was obtained at the lower oxygenation level. Moreover, a re-consumption of the produced succinate was also observed when a threshold residual concentration of glucose was reached. Considering the influence of these two key parameters, a highly performant fed-batch process for the succinate production using a wild-type strain of C. glutamicum was defined. Then, a kinetic model was developed. This primary model was then generalized by integrating a correlation between kinetic parameters of model and oxygenation level. The results of both primary and generalized model simulation, showed an excellent agreement with the experimental data. The generalized model was then successfully transposed to a C. glutamicum mutant strain. In addition, a simplified metabolic model for C. glutamicum 2262 was constructed to understand the metabolic response of this bacterium in micro-aerobiosis. Both predicted production fluxes of lactate in microaerobiosis and of biomass synthesis during aerobiosis phase, under stationary conditions, agreed with the experimental data. This metabolic model was also able to predict, under dynamic conditions, the concentration profiles of the succinate during highly limited oxygen supply conditions
Traisnel, Caroline. "Étude de la diffusion et de la solubilité de l’hydrogène en surface et subsurface du nickel monocristallin : approches numériques et expérimentales." Electronic Thesis or Diss., La Rochelle, 2022. http://www.theses.fr/2022LAROS033.
Full textMetallic surfaces are at the central place of stress corrosion cracking and corrosion fatigue mechanisms. These latter turn out to be the initiation site of materials damage, while exhibiting great reactivity to their environment. As they act as front doors for solutes, like hydrogen or oxygen, towards the bulk, surfaces play a key role in hydrogen embrittlement (HE) processes. In order to identify HE-tolerant metallurgical states, an understanding of H-surface interactions under stress is necessary. By investigating elementary physical mechanisms implied at the first stage of corrosion fatigue, this thesis work aims to propose a beginning in assessing the impact of the emergence of surface defects due fatigue stress (surface dislocations, slip bands, vacancies) on the apparent local diffusivity and solubility of hydrogen near the surface of nickel. The first step of this study requires however to identify the surfaces crystallographic orientation effect on these local properties, which is the raw material of this thesis. For this, we work on monocrystalline {100}, {110} and {111} surfaces of undeformed nickel at first sight, using both numerical and experimental approaches. Experimentally, a hydrogen diffusion gradient is observed for each orientation by charging nickel single crystals with a pulsed electrochemical technique. Conversely to usual permeation techniques, this double-step potentiostatic one enables the characterization of hydrogen mobility at the entrance side of the sample which was proven to be the main location for H-trapping and embrittlement. A correlation between emerging surface and subsurface defects (characterized by MO/AFM/TEM) according to the degree of cyclic deformation and the local hydrogen diffusivity is then discussed in case of Ni{110}. In parallel, calculations at the atomic scale are carried out (DFT + Phonons) in order to determine the evolution free energies of hydrogen migration from near the {100}, {110} and {111} surfaces towards the bulk. The local solubility of hydrogen is calculated and discussed in terms of lattice elastic distortion energy related to the differentiated relaxation of the surface atoms for the three orientations. A confrontation with elastic theory approach highlights the evolution of local elastic properties. Finally, bigger scales calculations through EAM are initiated to study more complex systems by adding defects, such as surface steps, giving a start for a reliable basis to interpret the interactions between hydrogen and part of the surface defects involved with a fatigue solicitation
Jaber, Jana. "Application de la fabrication additive à la modélisation physique des joints et des massifs rocheux, par approches expérimentales et numériques." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0071.
Full textThis thesis presents a study of the application of additive manufacturing (known as 3D printing) to rock mechanics. It is part of a larger project aimed at building a 2m3 physical model of an explicit discontinuous rock mass, whose behaviour is mainly controlled by discontinuities. The 3DP technology adopted in this work is selective laser sintering, and the material is Polyamide 12. First, we present the experimental results of the mechanical characterization of artificial rock joints constructed by 3DP. Two joint families are tested. The first is characterized by a fixed aperture (0,4mm), a simplified geometry (planar or sawtooth), and containing rock bridges. The mechanical characterization shows that these joints exhibit a mechanical behavior similar to that of natural rock joints under shear tests, with a cohesion driven by the rock bridges, and a friction angle which depends on the angle of the asperities. The second family consists of joints with more realistic roughnesses, to which a JRC value, commonly used to describe natural joints, can be assigned. Again, experimental results show the potential of artificial joints to reproduce the mechanical behavior of natural joints, and to respect the Barton-Bandis criterion. Experimental studies are coupled with numerical modeling, using the UDEC software, to define the appropriate model that reproduces the experimental results, and to calibrate the mechanical parameters of both joints type. After defining different artificial joints with controlled parameters, cylindrical samples (16 x 32 cm) containing two and eight planar discontinuities with rock bridges are printed and tested under uni-axial compression. This is a first attempt at an explicitly discontinuous physical model containing joints with controlled mechanical behaviour. The mechanical behavior of these samples highlights the influence of discontinuities in controlling the global behavior and resistance of rock masses. The results are then compared to a numerical modeling under 3EDC. Finally, scaling laws are applied to the previous results. The application of scale factors to the experimental results shows the possibility of representing natural rock mass and rock joints with artificial 3DP joints (SLS technique) up to a scale factor on metric dimensions of 1/25
Ciblac, Thierry. "Stabilité de la zone non soutenue dans le creusement de tunnels en terrains meubles sans pressurisation : Approches expérimentales et numériques." Lyon, INSA, 1996. http://www.theses.fr/1996ISAL0051.
Full textUnderground excavation without pressurization implies that both heading and lateral sides remain unsupported for a certain time. Besides a key issue lies in the control of the stability of the unsupported area and settlements due to excavation, particularly in soft grounds. In order to study the stability of this area characterized by its length (free length) and its height (free height), a numerical approach and an experimental approach on a small-scale model have been developed. The numerical model is based on a failure calculation method considering 3D rupture mechanisms. It allows the determination of the safety factor for the heading and the lateral areas as a function of free length and free height, and taking into account the arching effect for soils above the tunnel. A comparison between this model and other numerical methods shows its wider field of application and leads to results in better agreement with real tunnels. The experimental approaches have been carried out on two small-scale models of different sizes with the same equivalent ground material modeled by a mixture of sand and kaolin and that satisfies the similarity conditions. Excavation tests are in good agreement with our numerical prediction of rupture mechanisms. Also our first quantitative results regarding the larger small-scale model agree well with numerical simulation results, suggesting that it provides a reasonably accurate picture of a full-scale tunnel
Ayed, Yessine. "Approches expérimentales et numériques de l’usinage assisté jet d'eau haute pression : étude des mécanismes d'usure et contribution à la modélisation multi-physiques de la coupe." Thesis, Paris, ENSAM, 2013. http://www.theses.fr/2013ENAM0056/document.
Full textThis study focuses on the machining of the Ti17 titanium alloy using high-pressure water jet assistance. Special emphasis is placed on the analysis of degradation mechanisms and tool wear during machining, with and without assistance. Wear monitoring was achieved by regular observations using both scanning electron microscope (SEM) and chemical analysis (EDS technique) to determine the areas of material deposition on the tool. These observations made it possible to explain the wear mechanisms for roughing and finishing conditions. Wear mechanisms for conventional machining and for assisted machining were found to be significantly different. Indeed, with high-pressure water jet assistance, some tool wear mechanisms are no longer activated, whereas others are accelerated. Hence, there exists an optimum water jet pressure which minimizes tool wear.To highlight the effect of water jet assistance on the thermomechanical phenomena in the chip formation zone, finite-element modeling has been performed. Fluid/structure coupling was developed to take into account the mechanical and thermal effects of the water jet. For this to be possible, the Johnson-Cook constitutive law and damage model have been identified for the Ti17 titanium alloy, under extreme conditions, over a wide range of temperatures and strain rates. This modeling has highlighted the fact that, for high-pressure assisted machining, the tool/chip contact zone is reduced. In addition, the simulation of chip fragmentation as well as the cooling effect on the tool and workpiece is possible.However, this model does not shed light on the effect of the microstructural heterogeneity of the material in the cutting zone. This is an important observation because the material studied has a very large grain size (of the order of a millimeter). For this reason, a new (multi-scale) modeling approach has been developed to take into consideration the microstructure of the material. The material is subsequently modeled as a polycrystal which obeys crystal plasticity constitutive laws. This new approach is then used to simulate chip formation, taking into account the grain orientations and phase changes that occur during the machining process
Ayed, Yessine. "Approches expérimentales et numériques de l'usinage assisté jet d'eau haute pression : étude des mécanismes d'usure et contribution à la modélisation multi-physiques de la coupe." Phd thesis, Ecole nationale supérieure d'arts et métiers - ENSAM, 2013. http://pastel.archives-ouvertes.fr/pastel-00973532.
Full textClouet, Boris. "Comportement hydromécanique d'assemblages bois collés à l'état vert : approches expérimentale et numérique." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0036/document.
Full textThe development of new adhesives during the last decades has implied radically changes in the sawmill industry. The gluing of unseasonned wood, called green gluing, allows a new order in the process of engineered wood products, thanks to the final position of the drying step. Nevertheless, the jointing prevents the free shrinkage of wood during the mass transfer, involving a stress development. Nowadays, numerous drying models have been developed to predict the deformations and stresses of wood, but few have been confirmed by experimental tests. For an organic material such as wood, the measurement of hygromechanical properties will be more efficient if there is no interaction between the material and the measurement system. One of the most promising experimental techniques for this kind of issue is noncontact optical measurement based on Digital Image Correlation principles. The objective of this study is to evaluate by experimental and numerical solutions the stress development in green-glued wood laminated timber subjected to drying conditions. An experimental method has been set up and the results allow to validate a numerical finite elements model. The model which has been chosen is an orthotropic elastic model, able to describe the morphology of the wood material. This study allows to identify the parameters governing the damage of the interface. This approach leads to suggest some preconizationsin order to optimize the behavior of product during the drying procedure
Mayeur, Didier. "Communication numérique en contexte organisationnel : approches qualitatives et expérimentales des représentations sociales et des processus de réception dans le e-commerce." Electronic Thesis or Diss., Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0273.
Full textDigital communication in the e-commerce sector remains poorly studied in the human, social, and communication sciences. By articulating two types of qualitative and experimental/quantitative methodologies, this multidisciplinary thesis, carried out in collaboration with Oxatis, sets out to find the solution to two main problems from an information-communication perspective. First, by mobilizing theoretical resources mainly from social psychology, a qualitative survey was conducted on a group of e-merchants. The results show that societal transformations linked to the growth of digital technology in general, and of the Internet in particular, help create a context in which e-merchants consider e-commerce as a new opportunity. The research uncovers the different types of difficulties related to the use of digital devices, including e-commerce sites.Secondly, in this context and with the aid of a multidisciplinary theoretical framework (theories of persuasive communication, social psychology of communication, theoretical models relating to user experience and engaging communication), the second objective aims to better understand the cognitive processes of reception. A series of seven experiments in an regular environment was conducted on a total of 20829 subjects. Our results show, according to our hypotheses, that a particular procedure we tested (Repeated Acquiring) generates significant effects
Maldonado, Marc. "VIBRATIONS DUES AU PASSAGE D'UN TRAMWAY : MESURES EXPÉRIMENTALES ET SIMULATIONS NUMERIQUES." Phd thesis, Ecole centrale de nantes - ECN, 2008. http://tel.archives-ouvertes.fr/tel-00356222.
Full textSamyn, Kévin. "Imagerie de subsurface à partir d'une approche géophysique multi-méthode basée sur l'inversion coopérative 2 D : Nouvelle formulation théorique et applications numériques et expérimentales sur des données électriques et sismiques." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066612/document.
Full textUnderstanding geology from geophysical investigation is better when information is obtained from different kinds of data. A single method may not have sufficient resolution to provide the expected information. Joint inversion is a step forward to quantitatively combine data of different nature. Joint inversion may be considered in two different ways, petrophysical or structural. We may subdivide a joint inversion into two categories, joint inversion of data function of the same physical parameter, and cooperative inversion of data of different nature such as electrical and seismic data. In this work, we propose to combine a zonal cooperative inversion scheme with a Gauss-Newton method for minimizing the cost function. The basic idea of zonal cooperative inversion is to use cooperatively fuzzy c-means (FCM) classe analysis and separate inversion algorithm. For each iteration classe analysis of separate inversion results is used to construct models composed by several classes that contain the parameter characteristics of dominant subsurface structures. These constructed models are then used in the expression of the model space a priori covariance term in a new stage of separate inversion. The resulting models are then possibly biased to a priori models which depend on the number of classes. To overcome this problem, we formulate the inverse problem using a regularization parameter selected by an adapted L-curve method to weigh the impact of the a priori model on the solution when geology cannot be described by segmented models. The advantage of such a formulation is to avoid undesirable bias towards the starting model and leads to significantly improved spatial resolution for consistent prior information. Hence, the choice of the number of classe to create the a priori model is although less important. The developed methodology is tested and validated on two synthetic models. An experimental application is performed on real data acquired as part of a research survey of the National Agency for Radioactive Waste Management (Andra) for the characterization of a site of interest. Given the results of this application, the use of a cooperative approach for the inversion of electrical and seismic data allows the reconstruction of a more robust geological model, consistent with all the data. The variations of the parameters with depth are more precisely described using this approach
Samyn, Kévin. "Imagerie de subsurface à partir d'une approche géophysique multi-méthode basée sur l'inversion coopérative 2 D : Nouvelle formulation théorique et applications numériques et expérimentales sur des données électriques et sismiques." Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066612.pdf.
Full textUnderstanding geology from geophysical investigation is better when information is obtained from different kinds of data. A single method may not have sufficient resolution to provide the expected information. Joint inversion is a step forward to quantitatively combine data of different nature. Joint inversion may be considered in two different ways, petrophysical or structural. We may subdivide a joint inversion into two categories, joint inversion of data function of the same physical parameter, and cooperative inversion of data of different nature such as electrical and seismic data. In this work, we propose to combine a zonal cooperative inversion scheme with a Gauss-Newton method for minimizing the cost function. The basic idea of zonal cooperative inversion is to use cooperatively fuzzy c-means (FCM) classe analysis and separate inversion algorithm. For each iteration classe analysis of separate inversion results is used to construct models composed by several classes that contain the parameter characteristics of dominant subsurface structures. These constructed models are then used in the expression of the model space a priori covariance term in a new stage of separate inversion. The resulting models are then possibly biased to a priori models which depend on the number of classes. To overcome this problem, we formulate the inverse problem using a regularization parameter selected by an adapted L-curve method to weigh the impact of the a priori model on the solution when geology cannot be described by segmented models. The advantage of such a formulation is to avoid undesirable bias towards the starting model and leads to significantly improved spatial resolution for consistent prior information. Hence, the choice of the number of classe to create the a priori model is although less important. The developed methodology is tested and validated on two synthetic models. An experimental application is performed on real data acquired as part of a research survey of the National Agency for Radioactive Waste Management (Andra) for the characterization of a site of interest. Given the results of this application, the use of a cooperative approach for the inversion of electrical and seismic data allows the reconstruction of a more robust geological model, consistent with all the data. The variations of the parameters with depth are more precisely described using this approach
D'Aloia-Schwartzentruber, Laetitia. "Détermination de l'énergie d'activation apparente du béton dans le cadre de l'application de la méthode du temps équivalent à la prévision de la résistance en compression au jeune âge : approches expérimentales mécanique et calorimétrique, simulations numériques." Lyon, INSA, 1998. http://www.theses.fr/1998ISAL0018.
Full textThe concept of maturity or equivalent age enables the combined effects of time and temperature, on the concrete strength development at early ages, to be accounted for. It is based on the Arrhenius' law which has revealed itself to be the most accurate in order to describe the temperature influence on cement hydration (exothermic reaction). A proper estimation of the concrete strength at early ages by the method of equivalent age is directly related to a correct determination of the Apparent Activation Energy: Ea. This is the unique parameter which characterizes the whole concrete mixture and which can be found in the Arrhenius' law. The major aim of this study is to show how calorimetric tests under semi-adiabatic conditions can be an alternative to unwieldy compressive tests procedures in order to determine Ea. The validity of the obtained Ea values has been verified by means of several mechanical tests. Moreover, the possibility of using either mortar or concrete is partially dealt with. The water to cement ratio appears to naturally be considered as a constant in proportioning an equivalent mortar. Finally, the evolution of the Apparent Activation Energy in relation to the degree of hydration is given. Hence, the widespread opinion that Ea depends on the degree of hydration is confirmed and a field of definition can be brought to the fore. Besides, a numerical tool: CHAL is developed. This enables rates of heat flow under adiabatic conditions to be simulated, by taking into account, the cement composition and the coupling which operates by the temperature. Hence, the influence of the polymineral characteristic of cement, on the determination of Ea can be underlined. Finally, the redefinition of the hydration degree which enables the detriment al effect of high temperature at earl y ages on the long term strength of concrete to be accounted for, and the definition of the setting time, make it possible to improve the method of equivalent age
NOGER, Christophe. "Contribution à l'étude des phénomènes aéroacoustiques se développant dans la baignoire et autour des pantographes du TGV. Approches expérimentale et numérique des écoulements affleurant une cavité et interactions non-linéaires de sillage entre deux cylindres." Phd thesis, Université de Poitiers, 1999. http://tel.archives-ouvertes.fr/tel-00006437.
Full textFelis-Carrasco, Francisco. "Atomisation et dispersion d'un jet liquide : approches numérique et expérimentale." Thesis, Ecole centrale de Marseille, 2017. http://www.theses.fr/2017ECDM0001/document.
Full textA typical water round-nozzle jet for agricultural applications is presented in this study. The dispersion of a liquid for irrigation or pesticides spraying is a key subject to both reduce water consumption and air pollution. A simplified study case is constructed to tackle both scenarios, where a round dn=1.2 mm nozzle of a length Ln=50dn is considered. The injection velocity is chosen to be UJ=35 m/s, aligned with gravity, placing the liquid jet in a turbulent atomization regime. The flow is considered statistically axisymmetric. Experimental and numerical approaches are considered.An Eulerian mixture multiphase model describes the original two-phase flow. Several U-RANS turbulence models are used: k-ε and RSM; where special attention is taken to the modelling of variable density effects from the mixture formulation. A custom numerical solver is implemented using the OpenFOAM CFD code. A series of study cases are constructed to test the influence of the turbulence modeling and first/second-order closures of the turbulent mass fluxes. LDV and DTV optical techniques are used to gather statistical information from both the liquid and the gas phases of the spray. The experimental campaign is carried out from x/dn=0 to x/dn=800. Concerning the LDV, small (~1 µm) olive-oil tracers are used to capture the gas phase, where a distinction between the liquid droplets and tracers is achieved by a specific set-up of the laser power source and the burst Doppler setting (BP-Filter and SNR). On the dispersed zone, DTV measurements are carried out to measure velocities and sizes of droplets. Special attention to the depth-of-field (DOF) estimation is taken in order to obtain a less biased droplet’s size-velocity correlation.Numerical and experimental results show good agreement on the mean velocity field. A strong dependence on the turbulence model is found. However, the RSM does not capture the same behaviour on the calculated Reynolds stresses. Indeed, neither the experimental anisotropy (R22/R11≈0.05), nor the liquid-gas slip-velocity can be reproduced, even with a second-order closure for the turbulent mass fluxes. The strong density ratio (water/air), flow’s directionality and production of turbulent kinetic energy may be the cause of a weak dispersion and mixing between the two fluids. This mechanism is not yet clarified from a RSM modeling point-of-view
Remy, Benoit. "Caractéristiques d'une butée de turbocompresseur : Approches numérique et expérimentale." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0125.
Full textWith increasing focus on downsizing, high performances, low fuel consumption and emission reduction of modern vehicles, turbochargers of combustion engines have become more and more innovative and technological. Leader in this field, Honeywell Turbo Technologies is interested in two major lines of research regarding lubricated contacts. A delay in response time is frequently observed between the gas pedal push and the pressure rise of ambient air at the compressor wheel. It is called turbo lag. This phenomenon is mainly induced by a parasitic frictional torque existing in the thrust bearing contact. Penalizing turbochargers performances and drivability, the reduction of turbo lag constitutes a major concern for the automotive turbocharger industry. As an event constantly occurring on working engines, exhaust gas pulsations represent an essential line of research. Due to successive openings and closings of engine valves, these pulsations result in significant axial load variations applied to the turbocharger thrust bearing. Current sizing of thrust bearing design resting on steady state studies of critical on-engine cases, the influence of exhaust gas pulsations on the thrust bearing behavior needs to be determined. This thesis presents a thermohydrodynamic model of the thrust bearing contact applied to turbochargers. A Modified Reynolds equation is established and uses the Modified Phan-Thien and Tanner model. It connects rheological characteristics of current engine oils to the behavior of long polymeric chain additives they contain. The necessity for fluid inertia and oil recirculation to be considered is demonstrated. The influence of oil elasticity on energy dissipation within the contact is numerically analyzed. A compromise on the extent of oil elasticity can lead to a turbo lag reduction. In addition, a thrust bearing rig is developed to highlight the influence of exhaust gas pulsations on thrust bearing performances. Experimental results support dynamic effects predicted by simulations
Abidelah, Anis. "Analyse numérique du comportement d'assemblages métalliques. Approche numérique et validation expérimentale." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2009. http://tel.archives-ouvertes.fr/tel-00725229.
Full textBernaud, Denise. "Tunnels profonds dans les milieux viscoplastiques : approches expérimentale et numérique." Phd thesis, Ecole Nationale des Ponts et Chaussées, 1991. http://tel.archives-ouvertes.fr/tel-00529719.
Full textBaïotto, Sébastien. "Modèle viscoélastique de remodelage osseux : approches théorique, numérique et expérimentale." Paris 12, 2004. https://athena.u-pec.fr/primo-explore/search?query=any,exact,990002140450204611&vid=upec.
Full textIn this work. We propose a bone remodeling model, which takes into account the trabecular hone viscoelastic properties and the osteocyte cells distribution, The mechanical behavior of the material is described with a Zener's law. The model stability is studied and the non linear equations governing the apparent bone density evolution are solved by a finite difference method in the case of a n-unit elements model. The presented numerical resuits show the influence of the viscous damping on the bone adaptation under controlled mechanical load. Furthermore, finite element simulations froin experirnental data, obtained from rat tibias and a human femoral head, indicate that the model can mimic hone evolution observed in vivo
Duthil, Patxi. "Etude du pompage de chaleur thermoacoustique : approches numérique et expérimentale." Paris 6, 2003. http://www.theses.fr/2003PA066103.
Full textGuérin, Nicolas. "Analyse thermomécanique du contact aube-stator : approches numérique et expérimentale." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC043.
Full textThe constant need for efficiency and lightweightness of aeroengines demands OEM continued efforts to open design domain. In particular, operations clearances between static and rotating parts of modern engines become narrower, leading to better efficiencies. However, lighter components generally have lower stiffnesses, causing a growth in dynamic phenomena participation in the engines life-cycle. Mutli-physics coupling effects are aggravated in the same manner, whether they are of thermomechanical or aeroelastic nature. In this context, it is therefore crucial to improve design tools so as to predict more accurately the operational conditions of the engine components, with a general objective to cut down development and operational costs, while ensuring engine reliability and passenger safety. This thesis closely follows previous work on blade–casing contacts, all aimed at modelling more accurately the underlying more and more complex phenomena and structures. The main objective of this work has been to introduce a model for the thermal phenomena occurring during contacts at the interface between rotating and static parts, based on industrial geometries of components, which are set in a test rig. Due to the sophistication of the parts, the addition of these phenomena in the model had to be performed while paying attention to high simulation constraints. In other words, a trade-off had to be found between speed and precision of the computations. Finally a correlation phase was to be performed between simulations and experimental trials was to be performed to assess the relevance of the proposed numerical tools. During this thesis, a modification and a new instrumentation of the CASTOR test rig were performed. Multiple contact trials were carried out, during which vibratory and thermal behavior of the components were measured. In parallel to these experimental operations, multiple numerical developments were tackled. Among them, a model reduction methodology of thermoelastic models of turbo-engine centrifugal compressors was developed. Also, multiple time-stepping procedures, originally dedicated to solve contact problems in a purely mechanical context, we extended to perform thermomechanical computations. Several complications were removed taking advantage of advanced methods stemming from the non-smooth dynamics community. Eventually, simulations were performed with diverse setups to both show the capabilities of the numerical tool as well as confront numerical results and experimental observations
Absi, Joseph. "Les paliers à rainures : approche expérimentale et simulation numérique." Poitiers, 1994. http://www.theses.fr/1994POIT2273.
Full textGillet, 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.
Full textLow 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
Caussanel-Laurent, Odile. "Agitation industrielle de fluides visqueux newtoniens et pseudoplastiques : approches expérimentale et numérique." Toulouse, INPT, 1990. http://www.theses.fr/1990INPT008G.
Full textAwad, Carmen. "Études numériques et expérimentales des feux marginaux." Thesis, Corte, 2021. http://www.theses.fr/2021CORT0001.
Full textWildfire suppression begins before the start of a fire incidence with the application of many proactive prevention policies. One of the most common method is the reduction of the fuel load accumulation by using controlled fires techniques also called prescribed fires. These fires are often conducted in forests and their intensity must be low to prevent any major damage on trees and on the soil. Thus, they must propagate under marginal conditions. So, a slight modification of the propagation conditions can cause their extinction. Indeed, the probability of sustainability of this type of fire depends on several natural factors (ambient temperature, relative humidity, wind speed, etc.) and also on the fuel properties (water content, shape, size, density, specific heat of combustion…). The aim of this study is to identify the fuel properties allowing fire propagation under these particular conditions. Also, the influence of some fuel properties, and of meteorological conditions (wind speed, ambient temperature, etc.) on the behavior of marginal fires and especially on the fuel moisture content of extinction are investigated.During a first work about the determination of the threshold value of the fuel moisture content involving fire extinction under no wind and no slope conditions, three models were used: a complete physical model, based on a multiphase formulation (“FireStar2D”), an analytical model published in 2014 by Balbi et al., and two experimental models. The first one is based on experimental tests carried out in the UMR SPE 6134 laboratory at the University of Corsica and the second one is an empirical model proposed by Wilson in 1985. Thus, field scale simulations were carried out using FireStar2D, with grassland and shrubs as fuel under conditions of light wind and no slope. Moreover, laboratory scale experimental burnings were conducted with excelsior fuel beds. The different results of the simulations and the burning tests are in agreement with those obtained with the semi-physical model. In addition, the effect of fuel load and the LAI, « Leaf Area Index », on the fuel moisture extinction threshold are studied.In a second study, several field scale numerical simulations are conducted with grassland under non-zero wind conditions in order to relate the fuel moisture content threshold to wind speed and to fuel load. This study also allows us to evaluate the influence of wind speed and fuel moisture content on marginal fire behavior and especially on flame characteristics.The results are encouraging and interesting to operational people working in fire management and firefighting fields, given the importance of marginal fire applications in these two domains
Dang-Hoang, Thong. "Rupture et endommagement d’un assemblage boulonné : approche expérimentale et simulation numérique." Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10066/document.
Full textThis study focuses on the study of fracture and damage of a bolted assembly made up of thin sheets of aluminum alloy 6082 T6, thickness e= 2 millimeters, in single recovery. Several configurations of assemblies (number and arrangement of fasteners) are studied in monotonous solicitations, analyzing the effects of board. The influence of torque and clearance will be considered for the study of the behavior of the link. An experimental approach was implemented to analyze the sequence of damage mechanisms simultaneously using the technique of acoustic emission (AE) and measurement of fields by digital image correlation (DIC). EA Technology has tracked the evolution of acoustic activities by planar localization to better identify the initiation and propagation of cracks. The DIC technique confirms the damage scenarios evaluating, the deformation field at any point near the fastener. The finite element technique was used to predict the overall behavior of these assemblies. The calculations are performed in a 3D computer code using solid elements, shell elements and and are undertaken both in élastoplasticité without and with damage. The prediction of damage has been done using two models : modeling decoupled depending on the model of Latham and Cockroft and coupled modeling based on the model of Gurson modified
Dang-Hoang, Thong. "Rupture et endommagement d’un assemblage boulonné : approche expérimentale et simulation numérique." Electronic Thesis or Diss., Lille 1, 2009. http://www.theses.fr/2009LIL10066.
Full textThis study focuses on the study of fracture and damage of a bolted assembly made up of thin sheets of aluminum alloy 6082 T6, thickness e= 2 millimeters, in single recovery. Several configurations of assemblies (number and arrangement of fasteners) are studied in monotonous solicitations, analyzing the effects of board. The influence of torque and clearance will be considered for the study of the behavior of the link. An experimental approach was implemented to analyze the sequence of damage mechanisms simultaneously using the technique of acoustic emission (AE) and measurement of fields by digital image correlation (DIC). EA Technology has tracked the evolution of acoustic activities by planar localization to better identify the initiation and propagation of cracks. The DIC technique confirms the damage scenarios evaluating, the deformation field at any point near the fastener. The finite element technique was used to predict the overall behavior of these assemblies. The calculations are performed in a 3D computer code using solid elements, shell elements and and are undertaken both in élastoplasticité without and with damage. The prediction of damage has been done using two models : modeling decoupled depending on the model of Latham and Cockroft and coupled modeling based on the model of Gurson modified
Sicard, Pierre. "Stress oxydatif et hypertension artérielle : approches expérimentales et cliniques." Dijon, 2007. http://www.theses.fr/2007DIJOMU11.
Full textAmong the many processes which appear to play a major part in the cardiovascular diseases development, oxidative stress (OS) and inflammation take a particular place. One of the questions which remains posed is their primary or secondary participation in the initiation of pathology such as arterial hypertension (HT). The originality of our work was to apprehend the HT and the cardiovascular protection by two complementary approaches: one experimental and one clinical study. The first experimental aimed at, in Spontaneously hypertensive rats, to appreciate the presence of circulating and tissue OS markers and to evaluate potential cardiovascular protection by reinforcing endogenous antioxidant defences by strong amounts of vitamin C. The second aspect of our experimental work consisted of a pharmacological approach by using a HMG-CoA reductase inhibitor (rosuvastatine). Our objectives were then 1) to specify if statin modified the OS status and inflammatory levels, and 2) to appreciate the cardiovascular incidences of this treatment. The third part of our work was interested in a clinical study on the basis of a myocardial infarction observatory based in Côte d’Or (RICO) datas. Our work aimed to evaluate the effects of statins treatment on cardiovascular mortality among hypertensive patients hospitalized for a myocardial infarction. These data support the hypothesis that statin treatment had an impact on physiopathological processes among patients at the very high cardiovascular risk. These results can have implications in the optimisation of treatment among hypertensive patients in secondary prevention
Jrad, Mohamad. "Modélisation du perçage à grande vitesse : approches analytique, numérique et expérimentale." Thesis, Metz, 2007. http://www.theses.fr/2007METZ037S/document.
Full textThe determination of the cutting forces generated during the drilling operation is an essential step in the drilling optimisation. This information is crucial for the cutting conditions determination and the tool definition. The aim of this work is to propose a predictive thermo mechanical model for the drilling process. This model is based ont the thermo mechanical oblique cutting model developed and validated in the LPMM laboratory. The parameters used in this model are the cutting angles, the cutting conditions, the behaviour of the workpiece materials and the friction conditions on tool-chip interface. After the determination of the cutting angles from the CAD definition of the drill using a mathematical geometrical model developed in this work, the cutting edges are decomposed into a series of linear oblique cutting edges. A modified version of the thermo mechanical model is then apllied on each elemental cutting edge in order to calculate the elemental cutting forces, and then the global thrust and torque are determined. Experimental dry drilling tests were performed in order to validate the presented model. The calculated and measured global torque and thrust were compared, a good agreement was obtained. In the last section a numerical model using the finite element method with two commercial codes are presented. 2D orthogonal cutting and 3D drilling simulations were carried out. Numerical simulation provides interesting information on the chip formation and on the temperature and stress distributions but the calculations are time consuming. The two proposed methods may be used as complementary approaches to optimize cutting conditions and drill geometry
Haddad, Oriana. "Convection naturelle nanofluidique en cavité hémisphérique inclinée : approches numérique et expérimentale." Thesis, Paris 10, 2018. http://www.theses.fr/2018PA100091.
Full textThis numerical and experimental thesis deals with natural convective heat transfer that occurs in a hemispherical cavity in steady state. The enclosure is filled with water or ZnO / water nanofluid. The volume fraction varies between 0% (pure water) and 10%. The coupola of the cavity is kept at a cold temperature. This work corresponds to the field of electronics and the cooling of different actives composants. Three active heating sources are studied: the first one is plane and circular (the disc) and the followings, centered on the disc with the same surface, are cubical and hemispherical. The tilted angle varies between 0 (dome facing upwards) and 180° (dome facing downwards) with respect to the horizontal plane. Heat sources generate important heat fluxes leading to high Rayleigh numbers values. Numerical approach is done by means of the volume control method based on the SIMPLE algorithm and using monophasic model. For each active source, the convective heat transfer is analyzed and quantified by means of a correlation of the Nusselt-Rayleig-Prandtl-tilt angle type. Experimentally, the heat sources are built step by step and the average convective heat transfer coefficient is calculated. The comparison measures-correlations questions on the cooling nanofluid’s efficiency
Camborde, Françoise. "Modèles de douleur chronique : approches bibliographiques et expérimentales." Bordeaux 2, 1992. http://www.theses.fr/1992BOR2P084.
Full textHoang, Thanh Tung. "Récupération et valorisation d'énergie thermique sur gaz chauds- Approche expérimentale et numérique." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2018. http://www.theses.fr/2018ESMA0016/document.
Full textThe aim of the thesis is to analyze the heat recovery on hot gases at intermediate temperature range (250°C - 450°C). For this purpose, the thermosyphon heat exchanger recuperation technology has been chosen. The choice of a working fluid adapted to these temperature levels is one of the crucial points. A literature review identified naphthalene as a potentialfluid for this temperature range. However, because of the lack of information about naphthalene heat pipes, the development of a fundamental test-rig was necessary to fully characterize the thermal behavior and transport capacities of this fluid.A thermosyphon heat-pipe charged with naphthalene in the shape of a smooth stainless steel tube with a diameter of 23.9mm, a length of 1 m (evaporator zone: 20 cm, condenser zone: 20 cm) has been manufactured and tested. The experimental results obtained demonstrate the feasibility of such system in this temperature range and for the thermal powers required.They reveal an unusual behavior of the thermosyphon during the start-up process. In steady state, the analysis deals with the influence of the saturation temperatures, the transferred heat power and the thermosyphon inclination. In terms of performances, the thermal conductance (evaporator, condenser, system) increases with the vapor temperature and decreases with the heat power supplied to the evaporator. The heat flow rate can be applied from 0.2 to 1.5 kW, or 1 to 8W/cm² at the evaporator. During the tests, the system is found to be less sensitive to inclination (0° to 78°), but more important for 84°. In the horizontal position, the thermosyphon operates, but its heat transfer remains high even far away from the thermosyphon mode. A theoretical model has been developed in which the local heat transfer coefficients(evaporator and condenser) are evaluated by different correlations from literature. The comparison with the experimental results allowed to validate the models retained with good agreement, and to make it possible to predict the heat pipe operation for other solicitations.Thus, and finally, a first thermosyphon charged naphthalene recuperator prototype was designed, manufactured and coupled to the "hot gas" line designed and performed in the laboratory. The first results obtained from the complete system allowed us to develop a strategy for heat recovery system on the exhaust line of an automotive application
Barre, Cyril. "Jet en écoulement transversal : observations expérimentales et numériques." Nancy 1, 1998. http://www.theses.fr/1998NAN10277.
Full textParant, Paul. "Compaction de microsphères poreuses d'oxyde de lanthanides : approche expérimentale et simulations numériques." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI086/document.
Full textOne option envisioned for the future management of high level nuclear waste is the transmutation of minor actinides into short-lived fission products in sodium fast reactor. This route requires the development of pellet fabrication processes to prepare Minor Actinide Bearing Blanket (MABB) for the transmutation of americium.Currently, those ceramic pellets are produced by powder metallurgy processes involving numerous grinding and milling steps that generate very fine and highly contaminating and irradiating particles. A viable option for reducing the amount of those fine particles would be to develop a dustless process by working on much coarser particles. In this context, this study is concerned with the pelletization of porous and spherical lanthanides oxide precursors (surrogates of actinides). The present work uses both experimental data and numerical simulations to optimize the pelletization step. The final aim is to obtain, after sintering, homogeneous, dense and undistorted ceramic pellets.Firstly, this study concerns the synthesis and characterisation of these oxide microspheres precursors by the Weak Acid Resin process, which consists in loading beads of ion exchange resin with lanthanides cations and mineralizing the metal loaded resin leads into sub-millimetric-sized oxide microspheres. Comprehensive characterisations of the microstructure and mechanical properties of oxide microspheres have been carried out to better understand their behaviour into the matrix when producing pellets.Secondly, the mechanical properties of a single microsphere were investigated in order to better understand its behaviour during compaction steps. They were also analysed using multi-scale simulations based on the Discrete Element Method (DEM), which is well suited for such particulate materials. In a second approach, compaction studies were carried out in a three parts die to characterize the mechanical behaviour under pressure of a large number of oxide precursors. The behaviour of several microspheres in the matrix was finally simulated using DEM in order to describe interactions between microspheres and to have a better understanding of their evolution during pressing
Rouyer, Olivier. "Dysfonctions endothéliales après transplantation et diabète : Approches expérimentales et cliniques." Strasbourg 1, 2008. http://www.theses.fr/2008STR13075.
Full textAmong its many functions, vascular endothelium modulates vascular tone by secreting vasodilators and vasoconstrictors factors. Some diseases alter this balance, causing endothelial dysfunction which reduces organ perfusion and may jeopardizing the life. The work presented shows the interest of exploring endothelial dysfunction through endothelium-dependent relaxation studies, both in vitro through the analysis of aortic vascular ring reactivity in chamber organ and in vivo through flow-dependent dilatation of the humeral artery measurement, in response to a post-ischemic hyperaemia. In a model of aged rats with type 1 diabetes induced by streptozotocin, the late introduction of an IEC is deleterious on the exercise capacity. The normalization of blood pressure induced by the IEC could affect muscle perfusion. Endothelial function was not impaired and was not affected when the term of diabetes was lower. In a genetic model of Goto-Kakizaki rat type 2 diabetes, there was endothelial dysfunction related to the production of vasoconstrictors prostanoids. It was not improved by training even if training improved glycemic profile. In stable heart transplant patients with “normal” cardiac function, the persistent rise of plasma BNP values appeared to be related to endothelial dysfunction. While among hepatic transplant patients, normality of the endothelial function could be linked to the low prevalence of cardiovascular risk factors and a possible direct protective effect of Tacrolimus
Soveja, Adriana. "Modélisation du processus de texturation par faisceau laser : approches expérimentale et numérique." Phd thesis, Université de Bourgogne, 2007. http://tel.archives-ouvertes.fr/tel-00345826.
Full textSoveja, Adriana-Florina. "Modélisation du processus de texturation par faisceau laser : approches expérimentale et numérique." Dijon, 2007. http://www.theses.fr/2007DIJOS057.
Full textThe aim of this work is to have a better control on the laser beam surfaces texturing on three materials: 304L, TA6V and AA6056 alloys. For this purpose, it has been used two types of modelling, experimental and numerical, that are complementary. Using an experimental design approach it was observed that the laser surface texturing process of 304L and TA6V alloys are strongly influenced by energy and frequency of pulses. In order to obtain a surface roughness Sa 5 µm for the biggest possible productivity it is necessary to work with an energy of 5 mJ and a frequency ranging between 10 and 12 kHz. Unfortunately, for aluminium alloy AA6056 it is necessary to make a choice between having a good surface quality and having a high productivity. The numerical simulations of the coupled phenomena (thermals-hydrodynamics-mechanics) complete the experimental information and they have been showed that the existence of a strong recoil pressure generates a strong movement of liquid towards the edges of the crater (v some m. S-1) which continues after the end of impulse (inertia effect). The fact that the displacement of the liquid is more important for AA6056 than for 304L and TA6V, determs a more important pads formation arround the impact. This has a negative influence on surface roughness. In this case, in order to minimize the surface roughness, it is necessary to assure the best compromise which is making possible to favour the vaporization, to decrease the thickness of the melt liquid and to optimize the covering rate of the impacts. In conclusion, the laser beam can successfully be used in metal’s surfaces texturing process