Thèses sur le sujet « Essais par ultrasons – Simulation par ordinateur »
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Verma, Ravi. « Interaction of ultrasonic waves with frictional defects in the context of nondestructive testing of materials ». Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN063.
Texte intégralThis thesis concerns theoretical concepts, models, and experiments for elastic wave propagation and vibrations in solids containing internal contacts (cracks, delaminations, etc.) having frictional nature. The study is oriented to nondestructive testing and therefore focuses on the case where the material contains few cracks of known configuration, in contrast to microcracked solids in which a statistical ensemble of a large number of internal contacts is present.An essential part of the work is related to a development of a method of numerical acoustics capable of imitating elastic waves in an environment containing frictional cracks/contacts. These planar defects represent a sort of inner boundaries at which appropriate boundary conditions should set. These boundary conditions are set using an original model for frictional interaction based on Cattaneo-Mindlin (or Hertz-Mindlin) mechanics in which two spheres are mechanically excited with an oblique force. The known solutions are extended to the case of rough surfaces and arbitrary in time oblique excitation.Another component of the numerical acoustics model we present here is a standard finite element description for elastic waves in solid materials (solid mechanics unit in a commercial FEM package). Some technical efforts have been made to integrate a user-defined contact model as a boundary condition into the solid mechanics unit. As a result, a complete model has been obtained that incorporates wave-induced contact frictional interactions described starting from first principles of contact mechanics.An essential progress in comparison to previous works is related to application of the elaborated model to a case that corresponds to a known technique of nonlinear acoustic nondestructive testing. The chosen technique is based on excitation of a sample with a harmonics wave that, after completion of a transient regime, results in a purely harmonic response of an intact sample, whereas the response of a damaged sample will present anharmonicity. The generated harmonics form its own standing wave pattern that can have a clear maximum around the defect. In practice, surface signal measurements are done via laser vibrometry; our modeling therefore represents an attempt to imitate laser vibromenry NDT experiment in geometrically simplified conditions, but fully adhering to its ideology.The simplified conditions are taken in a way that reduces the computation time. The most important assumption is a 2D geometry that immediately disables a quantitative comparison to experiment. Other simplifications are discussed below in greater detail. Keeping, however, the general methodology close to experimental principles we generate a large number of synthetic nonlinear images of an isolated crack immersed into a fragment of a solid plate. We analyze in detail influence of geometric and physical parameters of the system in the cases of one- and two-frequency excitations.Finally, we focus on the case close to real experimental conditions in terms of the sample geometry and boundary conditions selected. A preliminary theory and experiment comparison is presented.Generally, the results of this thesis could be of interest for researchers involved in nonlinear acoustic NDT experiments as well as for those who look for applications of modern semi-analytical contact models based on Cattaneo-Mindlin principles
Dridi, Samia. « Essais de caractérisation des structures tissées ». Lyon, INSA, 2010. http://theses.insa-lyon.fr/publication/2010ISAL0041/these.pdf.
Texte intégralIn this work, we interested to the study and the modelling of mechanical behaviour of weave structure. We begin by presenting the properties of tested materials thanks to tests of characterization. An experimental data base is established to analyze the mechanical behaviour of fabric under some solicitations, in particular the shear, using the technique of digital image correlation. Then, by adopting a hyperelastic approach, a simplified model is developed allowing to study numerically the influence of the report of tensile and shearing rigidities on the mechanical behaviour of woven fabric, further to an extension in 45. Finally, by basing on phenomenological approach, a hyperelastic behaviour law is proposed. This model is implanted in a routine Vumat. It is identified from the tensile and the shearing tests and validated by certain cases of composite reinforcement forming
Dautriat, Jérémie. « Comportement hydromécanique de roches réservoir sous contraintes : relations entre évolution de perméabilité et échelles des mécanismes d'endommagement ». Palaiseau, Ecole polytechnique, 2009. http://tel.archives-ouvertes.fr/docs/00/38/57/77/PDF/Manuscrit_These_Dautriat.pdf.
Texte intégralThe Understanding and the prevention of damage mechanisms, which have an impact on the kinetics of production and the rate of recovery, remain an outstanding issue in reservoir engineering. The aim of this study, based on the characterization of the hydromechanical behaviour of sandstone and carbonate rocks in 'reservoir conditions', is the identification of the local mechanisms responsible for changes in permeability measured macroscopically. The experimental work was performed with an original triaxial set-up, which allows measurements of the stress-induced permeability evolutions in the principal directions of the stress tensor. A first experimental campaign, consisting in hydrostatic and uniaxial compression tests, has been performed on Fontainebleau and Bentheim sandstones. In one hand, we showed that experimental end-effects might affect significantly the ‘classical' axial permeability measurements, and in the other hand, we have determined the impact of brittle failure on directional permeabilities. Compression experiments, following different stress-paths, were also carried out on a carbonate, the Estaillades limestone. In elastic deformation regime, the reduction of permeability was modelized by pore network simulations, based on 3D reconstructions of μ-tomography RX and a simplified representation of the pore space. While brittle fracture of carbonate samples induced slight permeability evolutions, at higher effective pressure, permeability drops can reach 90% to the initial values and are associated with mechanisms of pore collapse. The post-mortem analysis of deformed samples, coupled with digital image correlation methods, using both SEM and Optical acquisition devices, provide a better understanding of the role of the heterogeneities, identified at different scales, in the strain localization and their potential impacts on permeability changes at the sample scale
Rocher-Lacoste, Frédéric. « Etude expérimentale en vraie grandeur et étude numérique des pieux vibrofoncés : Vibrations dans l’Environnement et Capacité Portante ». Paris Est, 2008. http://pastel.paristech.org/5507/01/FRL-rapport_final.pdf.
Texte intégralThe objective of this work is to better understand the phenomena related to vibratory driving and to capitalize on it. This report is organized into three chapters. The first describes two techniques of driven piles: impact driving and vibratory driving. The second chapter is based on two axes : 1) A full scale experimental study of acoustic impact of sound and especially an analysis of noise caused by the driving piles with a vibrator, a hydraulic hammer or a pneumatic hammer, 2) A full scale experimental study of particulate velocity during pile driving, coupled with a numerical analysis (both in 2D and in 3D), with the finite element software package CESAR-LCPC. From full-scale experiments, the third chapter compares the bearing capacity of piles implemented by impact and vibratory driving and proposes to take into account the vibratory driving piles into the French rules
Gaudillière, Camille. « Cisaillage à grande vitesse : des essais à la simulation ». Paris, ENSAM, 2011. http://www.theses.fr/2011ENAM0052.
Texte intégralTo increase their productivity, blanking professionals are interested by an emerging process: the high speed blanking. For this process, the punch speed reaches10m/s whereas this speed does not exceed 0,1m/s for conventional blanking process. However, even if the quality of the obtained surfaces is close to those obtained with fine blanking, the occurence of hard dynamic phenomena makes difficult the deployment of the high speed blanking process. This work proposes to better control this process using experimentations and numerical simulations. An instrumented device has been designed to observe in detail the existing phenomenon during cutting. This device is similar to the industrial one. It includes a punch with non-constant sections and a matrix linked to an Hopkinson's tube in order to measure the blanking cutting forces. This measure requires a specific treatment to correct dynamic effects present in the matrix during the cutting. This treatment, which uses a calibration of the device, was validated thanks to a one-dimensional numerical model. Many observations made on the blanked surfaces have shown that adiabatic shear bands (ASB) can take place. A thermo-mechanical constitutive model (Johnson-Cook's law) of the C40 steel has been identified and used into simulations to reproduce real experimentations. The used simulation is based on a C-NEM approach (Constrained Natural Element Method). A comparative study between simulation and experimental results has been done. Results show a good correlation with experimental tests
Albach, Daniel. « Amplified Spontaneous Emission and Thermal Management on a High Average-Power Diode-Pumped Solid-State Laser – The Lucia Laser System ». Palaiseau, Ecole polytechnique, 2010. http://tel.archives-ouvertes.fr/docs/00/50/49/15/PDF/these_final.pdf.
Texte intégralOn trouve sur la plateforme de thèses en ligne Pastel le résumé suivant : The development of the laser triggered the birth of numerous fields in both scientific and industrial domains. High intensity laser pulses are a unique tool for light/matter interaction studies and applications. However, current flash-pumped glass-based systems are inherently limited in repetition-rate and efficiency. Development within recent years in the field of semiconductor lasers and gain media drew special attention to a new class of lasers, the so-called Diode Pumped Solid State Laser (DPSSL). DPSSLs are highly efficient lasers and are candidates of choice for compact, high average-power systems required for industrial applications but also as high-power pump sources for ultra-high intense lasers. The work described in this thesis takes place in the context of the 1 kilowatt average-power DPSSL program Lucia, currently under construction at the ‘Laboratoire d'Utilisation des Laser Intenses' (LULI) at the Ecole Polytechnique, France. Generation of sub-10 nanosecond long pulses with energies of up to 100 joules at repetition rates of 10 hertz are mainly limited by Amplified Spontaneous Emission (ASE) and thermal effects. These limitations are the central themes of this work. Their impact is discussed within the context of a first Lucia milestone, set around 10 joules. The developed laser system is shown in detail from the oscillator level to the end of the amplification line. A comprehensive discussion of the impact of ASE and thermal effects is completed by related experimental benchmarks. The validated models are used to predict the performances of the laser system, finally resulting in a first activation of the laser system at an energy level of 7 joules in a single-shot regime and 6. 6 joules at repetition rates up to 2 hertz. Limitations and further scaling approaches are discussed, followed by an outlook for the further development
Ledoux, Yann. « Optimisation des procédés d'emboutissage par caractérisation géométrique et essais numériques ». Phd thesis, Chambéry, 2005. http://tel.archives-ouvertes.fr/tel-00419320.
Texte intégralCollin, Jean-Marc. « Identifiabilité des paramètres de lois de comportement de matériaux par essais d’indentation continue ». Rennes 1, 2008. http://www.theses.fr/2008REN1S079.
Texte intégralThe aim of this thesis is to study the potential of indentation test in the determination of the materials behaviour laws parameters. From a study of the spherical indentation, some models describing indentation data changes were proposed. They allow a good evaluation of the stress-strain curve of several metallic samples by inversion. However, it has been observed that isotropic hardening is not sufficient to describe the unloading and reloading during an indentation test. Thus, models combining both isotropic and kinematic hardening were used in order to describe the whole indentation test. They depend on many parameters; an approach by inversion of models becomes then difficult. We then propose the use of inverse analysis approach on indentation tests in order to determine the parameters of these behaviour models
Bittencourt, Machado Christiano. « Suivi de la consolidation des fractures par transmission axiale ultrasonore : effet de la composition et de la minéralisation du cal osseux ». Paris 6, 2011. http://www.theses.fr/2011PA066450.
Texte intégralChen, Yu. « Contribution à l'optimisation de l'aisance d'un vêtement par les techniques de calcul avancé ». Lille 1, 2006. http://www.theses.fr/2006LIL10020.
Texte intégralSahraoui, Sohbi. « Effets dynamiques dans les essais de rupture aux grandes vitesses de chargements : Etude de quelques polymères ». Bordeaux 1, 1986. http://www.theses.fr/1986BOR10612.
Texte intégralRenard, Béatrice. « Etude expérimentale et modélisation du comportement thermique d'une machine électrique multi-fonctions : application à un alterno-démarreur intégré ». Poitiers, 2003. http://www.theses.fr/2003POIT2282.
Texte intégralThe work consisted in studying the thermal behaviour of an electrical induction motor operating as an alternator, a starter and a booster in a motor vehicle. A numerical thermal model (nodal method) was elaborated of an ISA (Integrated Starter Alternator) and its environment. The winding of copper was studied. In addition, the modelling of this closed machine required a simulation of convective transfers with the help of a CFD tool and the use of a superposing method in order to translate the obtained results into a network. In parallel, specific experimental trials brought us to validate the thermal model, analyse certain aspects of the thermal behaviour of this multi-function system and be more precise in assessing the amount of iron losses generated in the alternator mode. In conclusion, the nodal model, obtained after adjusting, led us to classify the important parameters in view of the behaviour of the ISA when in use during precise driving cycles
Deydier, Sébastien. « Modélisation par une méthode d'homogénéisation de la propagation ultrasonore dans les composites multicouches : application à la simulation du contrôle non destructif ». Paris 7, 2006. http://www.theses.fr/2006PA077215.
Texte intégralSimulation of ultrasonic testing is of great interest for the aircraft industry to improve measurement analysis and optimize configurations. This thesis describes a study dedicated to the modeling of the ultrasonic propagation in parts made of carbon-fiber-reinforced epoxy composites (CFRP), whose thickness and shape complexity tend to increase in current industrial use. We propose here to compute the field radiated into such parts by means of a ray theory based homogenization method, coupled to the pencil model used for the radiated field computation. This homogenization is based on the follow-up of the energy ray path inside each ply of a repeated pattern, which gives access to an average energy direction. A set of calculated energy directions allows us to construct the overall slowness surfaces, and an appropriate inverse method is then applied to obtain the associated effective stiffness tensor. Therefore, an effective anisotropic homogeneous medium is described, characterizing the whole composite. An improvement is also proposed, which consists in fully taking into account the inner refraction phenomenon. The benefits of this complete procedure are shown through comparisons of measured and simulated fields transmitted through parts of continuously varying thickness. Experimental and simulated echoes with typical composite defects are finally compared and show the efficiency of our method
Jezzine, Karim. « Approche modale pour la simulation globale de contrôles non-destructifs par ondes élastiques guidées ». Bordeaux 1, 2006. http://www.theses.fr/2006BOR13241.
Texte intégralYunus, Yuhanis. « Modélisation discrète du comportement cyclique des matériaux granulaires ». Ecully, Ecole centrale de Lyon, 2008. http://www.theses.fr/2008ECDL0033.
Texte intégralAl, Galib Dhafar. « Comportement statique et dynamique de structures fusibles susceptibles d'absorber les énergies d'impact en cas de crash ». Lyon, INSA, 2003. http://www.theses.fr/2003ISAL0033.
Texte intégralThe objective of this study is to contribute to the improvement of the behavior to the crushing tubular extrusion, which should permit to find a structure optimizing the absorption of impact energy. An attempt to identify the characteristic behaviors of the studied structures was made by an experimental, analytical and numerical approach, Three main objectives constitute the frame of our study: * How will be able to reduce, during the crash, the first peak load, which reflect the decelerations transmitted to the occupants of the vehicle? * How will be able to dissipate by a controlled manner the kinetic energy during crash event? The proposed process, which reduced the first load peak, can be used for other geometries and other materials? * How can one evaluate the influence of the rupture of aluminum alloy on the global behavior of tubes, and what criteria can one propose to detect the rupture? On the experimental and numerical plan, the behaviors of static and dynamic crushing of circular and square aluminum tubes have been studied. A process that permits to decrease the deceleration transmitted to the passengers during impact or frontal collision has been proposed and validate. We could also have evaluated the behavior of these tubes while varying the mass and the speed of impactor and finally to study geometric imperfection, boundary conditions and loading affects on the static and dynamic behavior. Propositions are made for the choice of the geometric parameter used in order to facilitate the similarity (material, geometry). Finally, we linger especially on the influence of the rupture, that it is necessary to consider in an objective of design and quantification of the energy absorbed
Ngo-Ngoc, Cyril. « Modélisation non linéaire et simulation des matériaux souples textiles : application aux essais Kawabata ». Lille 1, 2003. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2003/50376-2003-13.pdf.
Texte intégralTran, Gia Phuong. « Crack Inspection and simulations with Eddy Current Thermography for the Aerospace Industry ». Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/30044/30044.pdf.
Texte intégralEddy Current Thermography (ECT) is a non-contact, non-destructive testing (NDT) method, and nowadays it is used in a wide range of applications. This method combines eddy current and thermographic NDT techniques in order to provide an efficient method for crack detection. In this method, the eddy current is generated into metallic specimens. If the specimen contains cracks, the current flow and temperature propagation inside the metallic specimens would be affected by these cracks. The changes of temperature distribution are captured by an infrared camera. One of the main challenges in this method is that it requires many parameters in the experiments, such as coil excitations: the frequency value, number of turns, material of wire, radius of the coil...In order to optimize the experiments, numerical simulation is necessary, and COMSOL Multiphysics® FEM software is a very suitable solution. During the simulation process, a crack detection limit for a crack in a given metallic specimen has been proposed. The simulation results and crack detection limit are also verified using experiments in the laboratory. The final goal of this thesis is to provide the overall picture of the Eddy Current Thermography, crack detection limit and the manner in which to simulate as well as perform the experiments in order to detect cracks on the metallic plate specimens which were provided by L3-MAS and Pratt & Whitney Canada (P.W.C), the industrial partners involved in this project which was sponsored by the Natural Sciences and Engineering Research Council of Canada (NSERC) and The Consortium for Research and Innovation in Aerospace in Québec (CRIAQ).
Broca, Olivier. « Influence des caractéristiques aérodynamiques d'un écoulement en conduite sur la réponse d'un débitmètre à ultrasons ». Toulouse, ENSAE, 2004. http://www.theses.fr/2004ESAE0003.
Texte intégralHoumed-Gaba, Abdourahman. « Hydrogéologie des milieux volcaniques sous climat aride : caractérisation sur site expérimental et modélisation numérique de l'aquifère basaltique de Djibouti (Corne de l'Afrique) ». Poitiers, 2009. http://www.theses.fr/2009POIT2266.
Texte intégralThe Djibouti aquifer is constituted by fractured basalts and scoria of 1 to 9My old, intercalated by sediments layers. It is localised in a coastal area under semi-arid conditions. This aquifer is exploited over 15 millions m3/year for Djibouti town water supply. A hydrogeological research site which includes by now 11 wells was set up on the aquifer, over 1 hectare area. Lithological logs of the wells show scoria underlying fractured basalt. Electrical conductivity profiles performed on the research site wells show fresh groundwater overlying at places brackish water. Slug tests were conducted on the fractured basalts, using Hvorslev (1951) and Bouwer & Rice (1976) solutions. Long term pumping tests were conducted to characterise the scoria. An estimation of the average hydraulic conductivity is thus obtained for the fractured basalts (K=10-8m/s) and for the scoria (K=10-2m/s). The long term tests have been interpreted using the semi-confined Hantush-Jacob model (1955) which showed that the scorias are under leaky conditions. The chemical analyses results, using multivariate statistical tools (factorial analysis) show three types of water, chloride water, sulphate group and bicarbonate type. A numerical modelling is elaborated using the pilot points methodology in conjunction with the PEST non-linear parameter estimation and regularisation functionality. The water balance showed that the exploitation of this aquifer has reached a crucial limit and cannot be increased without serious risks of degrading its resources
Girard, Patrick. « Diagnostic de pannes temporelles dans les circuits digitaux ». Montpellier 2, 1992. http://www.theses.fr/1992MON20053.
Texte intégralBoussetta, Abid Hajer. « Caractérisation expérimentale par émission acoustique et modélisation numérique du comportement des structures composites obtenues par enroulement filamentaire ». Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2519.
Texte intégralNowadays, filament wound composite pipes GRP, are widely used in in the transport of fluids. However, for the designer, these new materials represent a significant change, which profoundly affects the design and realization of industrial products. In order to take the measure of this change, it is essential to understand the mechanical characteristics of this material through experimental tests; which is the purpose of this thesis works. Thus, several techniques and tools have been used, in particular the acoustic emission technique. This experimental characterization study allowed the numerical modeling of the material behavior. During the development of the model, a set of parameters is involved; whose identification has required the use of special experimental devices, in addition to the numerical tool. The model has been validated by comparison with tensile and compressive tests on representative specimens. This paved the way for the use of this model in an industrial application by modeling a test of pipe pressurizing
Kadjo, Amangoua. « Caracterisation et contribution à l'optimisation des performances électriques des PEMFC ». Poitiers, 2006. http://www.theses.fr/2006POIT2279.
Texte intégralPam, Abdoulaye. « Méthodologie d’émulation pour le test de chaîne de puissance de véhicules électrifiés ». Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1I027.
Texte intégralThe electrification of transportation has become, for several years, an essential solution to deal with the various ecological problems in transport. Thus, electrified vehicles (hybrid and electric) are more and more put on the road. Test procedures for their various components are organized to optimize the design, production, and quality of these vehicles. Power Hardware-in-the-Loop simulation (using power emulators) has become an important step in the vehicle development cycle for these various tests. To reduce time and cost constraints, the rapid development of reliable and flexible power emulators is necessary. The objective of this PhD thesis is to propose a method for the design of power emulators for electrified vehicles for the testing of their various functional subsystems. EMR (Energetic Macroscopic Representation) formalism is used as an organization tool for the design of the various power emulators. The methodology developed is used to test the battery and electric drives of a series hybrid electric vehicle. First, a unified representation of the energetic simulation model of the series hybrid electric vehicle is proposed. Next, the methodology is applied for the battery testing of the reference vehicle. Finally, the methodology is applied for electric drives testing. Experimental results are provided throughout this PhD thesis to validate these various power emulators
Amory, Vincent. « Études du comportement complexe de source et du rayonnement ultrasonore des traducteurs multi-éléments flexibles au contact ». Compiègne, 2007. http://www.theses.fr/2007COMP1727.
Texte intégralUltrasonic methods of non-destructive testing (NDT) are frequently used in industries where safety requirements are important (nuclear, aerospace). To improve contact inspection of parts of irregular geometry, specific phased arrays are developed at the French Atomic Energy Commission (CEA), made up of an arrangement of piezoelectric elements assembled to make the probe flexible. Their active surface can fit the irregular shape of the component, thus inimizing aberrations in radiated ultrasonic field observable when rigid traditional transducers are used ; they make feasible and reliable examinations that are impossible otherwise. To optimize their design, to develop NDT methods using them, it is necessary to have a simulation tool able to predict the field they radiate. A field computation tool is implemented in the CIVA platform of CEA; it is widely used for the simulation of longitudinal (L) and transversal (T) waves testing using various kinds of ultrasonic transducers. For flexible phased arrays, a specific model has been developed; in certain directions of T wave propagation, predictions based on this latter model partially disagree with measurements. A tool to simulate T-wave inspections using these flexible transducers is developed in this thesis. Models of source and of radiation are based on observations made thanks to computation results by finite elements and to experiments. The model of source accounts for the complex stresses created by one of the elements of the flexible transducer to the transducer-part interface. The study of the radiation from these sources highlights the quantitative importance of head wave contribution, generally neglected, on the field radiated by small sources. Head waves are coupled with T-waves in certain directions of radiation; it is necessary to take them into account when using flexible transducers in T-wave testing. The proposed radiation model deals with L, T and head wave contributions; it combines exact Greens functions for T and head waves, and the asymptotic model already validated used at CEA for L-waves. Simulation results for the field radiated by a whole phased arrays transducer demonstrate the show the effectiveness of the developed model relatively to results computed under asymptotic approximations, to accurately simulate T-wave contact testing of parts of complex surface
Le, Louarn Catherine. « Étude et réalisation d’un outil de simulation et de test pour le logiciel temps réel ». Compiègne, 1986. http://www.theses.fr/1986COMPI224.
Texte intégralRoy, Sébastien. « Mesure de l’adhérence et des propriétés mécaniques de couches minces par des essais dérivés de la nanoindentation. Application à la microélectronique et au biomédical ». Paris, ENMP, 2008. http://tel.archives-ouvertes.fr/tel-00289845.
Texte intégralThree different tests, developed on a nanoindentation apparatus, are used for the mechanical characterization of various thin films: Cu, SiN and SiCN films for microelectronics (interconnection) and polymer films for biomedicals (drug eluting stent). Basic nanoindentation test is used for the measurement of mechanical properties of 500 nm Cu thin films deposited on Ta/TaN/SiO2/Si substrate. The experimental results and the 2D finite element calculations show the inadequacy of the Oliver and Pharr analysis for this kind of materials, because of the growth of a pile-up around the contact area. A work-hardening effect also induces a huge increase of the hardness values during penetration. This work-hardening effect is influenced by annealing temperature of the Cu films. Mechanical adhesion of Cu films was then measured by Cross Sectional Nanoindentation (CSN). The experimental procedure and the mechanical interpretation of this test were strongly improved. Results show the influence of annealing temperature and substrate patterning on Cu adhesion. A 3D numerical simulation is developed to calculate deformation energy spent during film delamination. A micro-scratch test was employed for adhesion measurement of SiN and SiCN thin films (40 to 120 nm) deposited on Cu/Ta/TaN/SiO2/Si substrate. The influence of the film thickness and the wear of the indenter tip on the critical force are studied. Finite element calculations show that the delamination at critical force is due to high stress in the SiCN film and at SiCN/Cu interface. Micro-scratch test was then applied to polymer films (500 to 1000 nm) deposited on stainless steel. The results show the enhancement of the adhesion when an electro-grafted sub-layer is used to promote steel/polymer interface
Olivier, Loïc. « Prévision du vieillissement thermo-oxydant de composites à matrice organique dédiés à l'aéronautique : prise en compte des couplages multiphysiques ». Poitiers, 2008. http://theses.edel.univ-poitiers.fr/theses/2008/Olivier-Loic/2008-Olivier-Loic-These.pdf.
Texte intégralThe aim of the study is to understand and forecast damage onset conditions in aeronautic C/Epoxy composite materials, under thermo-oxidizing environment. An original testing device is presented, built for loading mechanically composite samples under temperature and gas pressure simultaneously, and studying couplings between deformation and thermooxidation mechanisms. On another hand, a multi physic modeling is performed, minimizing the resort to phenomenological parameters: this theoretical approach is taking into account all phenomena, and provides an expression of the coupling expressions. The model is then implemented in a finite element code, to simulate in a realistic way the composites evolution during a thermo-oxidizing cycle. A quantitative comparison is done between experimentally measured and numerically pre dicted matrix shrinkage values. A good agreement is observed in all onfigurations, as far as damage onset has not occurred. In the latter case, this onset can be detected and the scenario of damage initiation can be foreseen. In the end, the perspective of a multi scale approach is investigated, in order to extend the models application capability to the service life of large structural laminate components
Verone, Benjamin. « Étude du comportement statique et dynamique d'un matériau composite textile interlock 3D - caractérisation expérimentale et modélisation numérique ». Master's thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/35273.
Texte intégralThis study presents the development of a tool for numerical simulation of the behavior of a special textile composite material called interlock 3D. This composite woven fabric exhibits interesting performance in terms of impact resistance and damage tolerance. These properties come from the presence of strands woven through the thickness. As a result, this material can be a very interesting alternative to conventional laminated composite, which have only planar oriented fibers, for aeronautical applications where elements are subjected to impacts and subjected to delamination. This work presents an experimental campaign aimed at characterizing the behavior of the material in the in-plane directions and through the thickness. Subsequently behavior laws are developed to reproduce the mechanical behavior in each direction. Seting up the mechanics of damage, as well as the inelastic behavior were the most complex parts. This model is subsequently implemented in the ABAQUS / Explicit finite element software using a VUMAT subroutine. Simulations of the material mechanical behavior are first performed to validate the predictions of the model in all the directions. Then, quasi-static indentation tests are performed and the results compared to the model predictions. Finally, dynamic impact simulations are carried out on the woven composite using rigid and soft projectiles as well as different configurations. Comparisons with experimental results show the model's good ability to reproduce the behavior of the material during impact with a rigid low-velocity projectile. High impact energies reflect shortcomings in the mechanics of damage close to rupture. Impact results with a soft low-velocity projectile are encouraging and show the ability of the model to provide a correct estimate of the impact force, although overestimated in some configurations
Olivier, Loïc Lafarie-Frenot Marie-Christine Grandidier Jean-Claude. « Prévision du vieillissement thermo-oxydant de composites à matrice organique dédiés à l'aéronautique prise en compte des couplages multiphysiques / ». Poitiers : I-Médias, 2008. http://theses.edel.univ-poitiers.fr/index.php?id=532.
Texte intégralAlwash, Maitham Fadhil Abbas. « Assessment of concrete strength in existing structures using nondestructive tests and cores : analysis of current methodology and recommendations for more reliable assessment ». Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0587/document.
Texte intégralTo assess concrete strength in an existing structure, the current methodology combines nondestructive measurements (NDT) like rebound hammer or/and pulse velocity with destructive technique (cores) in order to implement a relationship ‘‘conversion model” between the compressive strength and NDT measurements. The conversion model is used to estimate the local strength value at each test location using the corresponding NDT value.Then the estimated mean strength and/or estimated strength standard deviation (concrete strength variability) values are calculated. However, the reliability of these estimated values isalways a questionable issue because of the uncertainties associated with the strength assessment based upon NDT measurements. To improve the reliability, the uncertainties must be reduced by specifying and controlling their influencing factors. Therefore, the objective of this thesis is to analyze the current assessment methodology in order to provide practical recommendations that can improve the reliability of assessing the in-situ strength in existing concrete structures by nondestructive tests and cores.To this end, a simulator was built in order to analyze the effects of the most influencing factors using a large campaign of datasets from different sources (in-situ or laboratory studies,and generated synthetic data).The first contribution of this work is the development of a new model identification approach“bi-objective” that can efficiently capture the strength variability in addition to the mean strength. After studying the effect of the way of selection the core locations, a method was proposed to select these locations depending on the NDT measurements “conditional selection” that improves the quality of assessment without additional cost. A third innovation was the development of a procedure to identify the relation between the number of cores and the accuracy of the estimation. Finally recommendations were derived in order to providemore reliable estimated values
Chen, Zhou. « Simulation virtuelle des essais de validation pour l'ameublement - meubles à base de plaques ». Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2071.
Texte intégralIn furniture industry, the numerical simulation allows the design and optimization of wood-based structures, thus avoiding expensive experimental campaigns. Most of wood-based furniture present some particular features in terms of material properties and geometries. On the one hand, the properties of timber materials (such as particule boards) are strongly heterogeneous and anisotropic. On the other hand, the furniture are often made of simply-shaped elements and then can be represented by an assembly of plates and/or beams. The present work deals with those specific features and presents the identification of the elastic properties of particle boards from digital image correlation (DIC) [Chevalier et al. 2001] as well as the simulation of the mechanical behavior of furniture. First, three-point bending tests based on Timoshenko’s beam theory are performed on different samples cut from a prototype desk for the identification of the material properties using DIC techniques. Secondly, a probabilistic model for the uncertain material parameters is constructed by using the Maximum Entropy (MaxEnt)principle [Soize 2017] combined with a Markov Chain Monte-Carlo (MCMC) method based on Metropolis-Hastings algorithm for generating realizations of the underlying random variables. Thirdly, numerical virtual tests are performed to propagate the uncertainties in the material properties through the model and assess the impact of such variabilities on the response of the structure. Lastly, several real tests were previously conducted on the desk in order to validate the proposed numerical approach. Quite good agreement is observed between the numerical computations and the experimental measurements
Mahboubi-Ardakani, Ahmad-Reza. « Contribution à l'étude micromécanique du comportement des matériaux granulaires par homogénéisation et approche numérique ». Ecully, Ecole centrale de Lyon, 1995. http://www.theses.fr/1995ECDL0018.
Texte intégralThe behavior of granular materials is usually modeled by phenomenological models based on continum mechanics. Considering the non continuity of the structure of granular materials, the alternative approach for modelling this behavior is to try to describe the global behavior of the medium from the local behavior of the structural element (particles). One of the important step of this approach is the definition of the static local variable (contact forces) from the static global variable (stress tensor). In this work a model is presented that permits this passage from the global to local variable. Using the obtained results for the contact forces and the local conditions for the contact instability a plasticity criterion is defined. For validating the obtained results concerning contact forces local informations are necessary. For this purpose the numerical simulation of granular assemblies (District Element Method) is used. The simulations on polydisperse packages of 1000 particules (2D and 3D) show a good ability of the simulations for describing the global behavior of granular materials. The comparison between the distribution of contact forces given by numerical simulations and the results of the proposed analytical formulation shows a good agreement
Marcon, Didier. « Étude de faisabilité d'un processeur matériel spécialisé pour la simulation concurrente de fautes ». Montpellier 2, 1986. http://www.theses.fr/1986MON20174.
Texte intégralGrisey, Anthony. « Modélisation et optimisation de la déposition de chaleur pour les ablations thermiques par ultrasons focalisés ». Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLC008.
Texte intégralThis manuscript aims at discussing the complex issue of modeling high-intensity focused ultrasound thermal ablations. An acoustical simulation method, based on the use of the k-Wave library, is described and applied to the description of the interaction between the acoustic beam and the superficial tissue layers. It is validated in the linear domain based on hydrophone measurements realized in different configurations with biological samples. Nonlinear simulations are subsequently used to evaluate the influence of the tissue geometry on the beam focusing.The thermal modeling of the treatment is then discussed with intent to design a truly quantitative model. An equivalent model of the modified heat deposition pattern in presence of boiling is presented and validated based on the use of original, diverse and unexpensive data.Finally, an algorithm is proposed to optimize the focal spot trajectory in order to maximize the heat deposition efficiency, thus reducing treatment time. The advantages and the limits of the approach are discussed based on different examples
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.
Texte intégralThis 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
Truc, Olivier. « Prediction of chloride penetration into saturates concrete - multi-species approach ». Toulouse, INSA, 2000. http://www.theses.fr/2000ISAT0019.
Texte intégralZine, Adil. « Fatigue multiaxiale des élastomères : vers un critère de dimensionnement unifié ». Lille 1, 2006. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2006/50376_2006_128.pdf.
Texte intégralServeaux, Jérémy. « Rupture ductile d’un conteneur de déchets radioactifs HA soudé et soumis à une corrosion généralisée ». Thesis, Troyes, 2019. https://tel.archives-ouvertes.fr/tel-03180078.
Texte intégralAndra, the French national radioactive waste management agency, is in charge of studying the possibility of disposal of High Level activity Wastes (HLW) in deep geological repository. Andra has planned to encapsulate HLW in non-alloy P285NH steel overpacks before inserting them into horizontal steel cased micro-tunnels called HLW disposal cells. The objective of this PhD is to study the long-term behavior of a welded steel overpack subjected to mechanical loading and generalized corrosion. Several tensile tests have been performed on smooth and notched specimens taken from both base material and welded material. For these materials, an elastoplastic behavior model with mixed nonlinear hardening strongly coupled with ductile isotropic damage and weakly coupled with generalized corrosion is developed. It is formulated based on the classical thermodynamics of irreversible processes framework with state variables at the macroscopic scale assuming the large plastic strains and small elastic strains. The comparisons between numerical and experimental results allow us to be confident in the capability of numerical simulations performed on P285NH to simulate the initiation and propagation of cracks. Finally, the addition of corrosion allows performing multiple simulations on overpacks, subjected to different mechanical loading conditions and corrosion conditions
Mora, Pierric. « Réponse élastodynamique d'une plaque stratifiée anisotrope : approches comparées. : Vers le développement de méthodes hybrides ». Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0382/document.
Texte intégralThis work adresses the direct problem of the propagation of an elastodynamic field radiated by a source in an anisotropic layered medium. Applications concern non destructive evaluation of composite plates by ultrasonic guided waves. In the lower frequencies, these materials can be modeled as homogeneous, anisotropic and dissipative media. Two causal approaches are studied and developped to solve the wave equation, and their interest is discussed regarding to the widely used harmonic modal method. One of these methods is modal, and is formulated directly in the time domain. It allows to deal easily with anisotropy, even in 3D ; however it also suffers classical shortcomings such as the high cost of the unestablished regime or the difficulty to deal with open waveguides. The other method is a formulation of the so-called partial-waves method in the Laplace domain. Its attractiveness relies in its versatility and in the fact that computational costs can be very acceptable. In a second time, we consider using both methods to solve problems of diffraction by defects. A boundary element method based on the partial-waves approach is developped and leads to solve very efficiently the case of a planar defect. The possibility of treating more general defects is briefly discussed
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.
Texte intégralThis 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
Motamedi, Nikzad. « Vers la prédiction et la compréhension des effets tribologiques sur les performances systèmes par l'intelligence artificielle ». Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN011.
Texte intégralThe contact between two parts, especially when it is induced as in braking systems, needs to be improved and therefore to be better understood. The phenomena involved are complex because they involve multi-scale, multi-physics concepts in a context of constant evolution. An additional difficulty is that the contact is closed, and therefore it is difficult to explicitly observe the interface phenomena that play a major role in the targeted performances (noise pollution, emission of fine particles, wear etc.). In view of the European environmental standards which will be increasingly severe, it is essential to establish new strategies to better understand the problem in its entirety. The team wishes to move towards the coupling of numerical and experimental methods. The "experiment" part is based on dedicated test benches with a rich and fine instrumentation. The "numerical" part is based on multi-scale and multi-physics modeling trying to consider tribological mechanisms within a complete system. One difficulty is to compare (realign) these two parts.Thus, the objective of this PhD thesis is to propose predictive models linking the contact interface with the complete system through artificial intelligence. In the first step, we will try to determine the natural frequencies of a pin-on-disk system by considering any surface for the interface. More precisely, this interface will present a roughness field that will be generated numerically. In the second step, an AI model is developed to predict the contact distribution during a test. This part is based on measurements of a thermocouple array embedded in the near surface friction material during the tests. In the third step, based on experimental acquisitions of the surface profile at different times, a model is proposed to determine the evolution of wear. The AI models specifically developed for these three parts use algorithms such as CNN, GAN, RNN etc. These concepts are not common in the mechanical community, they are illustrated on a simple example of behavior identification in the preamble of this manuscript. In terms of results, the obtained results are very satisfactory when compared to simulation and/or experimental data. This confirms the interest of using AI in order to pass a milestone in the prediction of models. Moreover, AI also allows the understanding and the importance of the input parameters which could be used in the medium term to optimize the system or to drive the tests
Van, Roey Jan. « Etude du comportement dynamique des matériaux granulaires et tissés : approche expérimentale et simulation numérique ». Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10179/document.
Texte intégralThis thesis deals with the absorption of shock wave energy by a granular material, and with the study of ballistic impact in fabrics and granular materials. For the assessment of shock wave absorption by a granular material, a test set-up was developed. This set-up allows the evaluation of incident and reflected pressure, and deflection and acceleration of a reference plate as a function of time. An analytical mass-spring-dashpot model with one degree of freedom can predict the deflection correctly. The ballistic performance of a granular material, impacted by a spherical projectile, is evaluated in terms of velocity decay through the material. The experimental results indicate that the impact can be considered as a hydrodynamic impact.In the numerical study, two approaches are used to apply the pressure on the granular material: direct application of the pressure on the sample, and propagation of the shock wave through an Eulerian domain. For the granular material, considered as homogeneous and isotropic, different models have been analysed. A new test set-up was developed for the continuous measurement of the projectile velocity during the penetration in ballistic fabric. The experimental results are compared to an analytical model, based on the conservation of momentum. It appears that the very simple analytical model describes the velocity evolution very well during the first phase after impact
Wu, Kai. « Étude du cisaillement des matériaux granulaires homogènes et hétérogènes par expérimentation et simulation de l'essai triaxial ». Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10028/document.
Texte intégralThis research work aims at studying the shear behavior of homogeneous and heterogeneous granular materials by triaxial test. The work is performed on glass beads both in laboratory tests and by numerical simulations in DEM (Discrete Element Method). From an experimental point of view, tests are first performed on homogeneous samples (monodisperse beads), then expands to heterogeneous cases like monodisperse systems comprising a large inclusion and bidisperse mixtures. From a numerical point of view, a cylindrical rigid wall boundary condition, based on the Lamé formula is integrated into an existing discrete elements code. A series of procedures is proposed to model the triaxial test in conditions similar to experimental tests. The numerical and experimental results are compared both for monodisperse and heterogeneous systems. The numerical model can reproduce deviatoric curves very satisfactorily in all experimental conditions. It also allows describing correctly the volumetric strains of the sample despite the simplicity of the boundary condition used. The developed numerical tool is an interesting complement to experiment triaxial tests. It makes it possible to study the influence of micromechanical parameters on the overall behavior of materials
Mosbah, Henia. « Sur quelques méthodes de résolution de problèmes de vibrations aléatoires non linéaires ». Clermont-Ferrand 2, 1998. http://www.theses.fr/1998CLF22087.
Texte intégralBéliveau-Viel, David. « Étude des paramètres influençant le comportement d'un amortisseur hydrolique ajustable : approche par modélisation ». Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27768/27768.pdf.
Texte intégralMarot, Guillaume. « Modélisation de l'essai d'indentation interfaciale et confrontation aux essais normalisés pour la détermination de l'adhérence de revêtements obtenus par projection thermique ». Lille 1, 2007. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2007/50376-2007-Marot.pdf.
Texte intégralEstocq, Philippe. « Une approche méthodologique numérique et expérimentale d'aide à la détection et au suivi vibratoire de défauts d'écaillage de roulements à billes ». Reims, 2004. http://theses.univ-reims.fr/exl-doc/GED00000129.pdf.
Texte intégralThis study deals with conditional maintenance by vibratory analysis. This activity constitutes an increasingly important part of the tools used to keep industrial plants in continuous service. This work proposes a numerical and experimental methodology of assistance to the detection and the vibratory follow-up of spalling defects in ball bearings. The objective of this work is to use a measurement point located on the casing of a revolving machine to carry out an effective vibratory monitoring. Two steps can be distinguished in this work. The first one consists in the conception of an optimized structural component, called resonator, to channel the vibrations if placed on the casing of the machine. The second step is a numerical determination of the optimum measurement point for defects detection, which can also be used for the follow-up of the evolution of severity of the spalling
Pinède, Pascale. « Conception, réalisation et validation du simulateur concurrent de fautes LOFSCATE ». Montpellier 2, 1988. http://www.theses.fr/1988MON20132.
Texte intégralAllali, Lahcen. « Conception et réalisation du préprocesseur du simulateur concurrent de fautes LOFSCATE ». Montpellier 2, 1987. http://www.theses.fr/1987MON20111.
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