Дисертації з теми "Méthode DIM"
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Tenanguena, Nongni Fresnelle. "Modélisation de la formation des ions moléculaires dans les plasmas froids de gaz rares." Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSES080.
Повний текст джерелаMolecular ions, in particular, dimeric rare-gas ions have a very important influence on the behavior of rare gas plasmas used in multiple fields. Therefore, the analysis and understanding of their formation are of great importance for the macroscopic modeling of these plasmas. The main objective of this work is to perform calculations of the rate constants of dimers ion formation in cold plasmas using rare gases as carriers over a wide range of reduced electric fields. To do so we have used mesoscopic data (cross sections) obtained from microscopic data (interaction potentials) for argon to provide reaction rate constants of the formation of Ar_2^+. Further, to perform our calculations we have considered all six lowest-lying electronic states of the Ar_2^+ ions. These six electronic states are classified in two fine structure states of the atomic ion, the ground state (_ ^2)P_(3/2) and the excited state(_ ^2)P_(1/2). A quasi-classical trajectory approach based on the nonadiabatic mean-field dynamics approach and Diatomics In Molecules (DIM) model of the interactions in collision complexes used in preceding studies to calculate the collision cross sections that we will use in the present work. These collision cross sections will feed a Monte Carlo code adapted and optimized for the calculation of auxiliary data such as collision energy distributions which are important to provide averaged, thermal ternary recombination rate constants of ground and excite states of the dimer ion. The ternary recombination rate constants calculated in this way are compared with the experimental measurements and theoretical available in the literature. The results we have obtained, are close to these experimental and theoretical values for selected values of reduced electric fields, E/N = 1, 50, and 100 Td, with standard conditions of temperature T = 300 K and pressure P = 10^5 Pa. Thus, these results are expected to be helpful in tuning cold plasma generators for specific applications
Tsopela, Alexandra. "Modélisation hydromécanique de la réactivation de faille par la méthode des éléments discrets." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI046/document.
Повний текст джерелаFaults in the Earth crust are localized zones of deformation which can drive fluids over long distances. Estimating the permeability of fault zones and their hydro-mechanical properties is crucial in a wide range of fields of research and industrial applications. In the petroleum industry, and more specifically in exploration and production applications, the seal integrity of faults in low permeability formations (e.g. shale) needs to be evaluated for the detection of hydrocarbon traps. There already exist approaches able to sufficiently estimate the "side-sealing" capacity of a fault based on the clay or shale content of the layers (e.g. Shale Gouge Ratio). Nevertheless, the conditions under which the fault acts as a drain along its structure are still not properly constrained. In this context, the response of the fault is directly controlled by a number of factors that can be better approached from a geomechanics point of view. These factors include the stress field, the fluid pressure, the orientation of the fault-related structures and the material properties. Meso-scale field injection experiments were carried out inside a fault zone located in the Tournemire massif at the South of France during which the fluid pressure, the deformation, the seismicity and the flow rate were monitored. Based on the Tournemire experiments and field observations, a numerical study was performed exploring the evolution of the permeability and how it is related to the fault hydro-mechanical reactivation and potentially to the induced seismicity. Fault-related structures such as subsidiary faults or fractures that were targeted during the experiments together with the surrounding intact rock, were modeled using the Discrete Element method. Modeling of the experimental tests and the analysis of generic models used to perform parametric studies highlighted the primary role of the in-situ stress conditions. The combined effect of stress and orientation of the fault structures determine in the first place the nature of the reactivation according to the critically stressed fault concept reported in the literature. For given stress conditions and structural features, it was shown that depending on the fluid pressure level, the fault offers three different ranges of permeability: i) permeability that is equivalent to the formation's permeability, ii) 2 to 4 orders of magnitude higher and iii) more than 4 orders of magnitude higher. While for the two extreme cases the fault is characterized as hydro-mechanically inactive or active, the second case is mostly controlled by fluid channeling mechanisms promoted by heterogeneities at the scale of a single fracture or at the scale of the fracture network. Changes in the hydraulic properties are in some cases detected by the seismicity triggered during the injection under the assumption that the seismicity is the direct effect of fluid propagation, fluid pressure increase and effective stress drop.However, the mechanisms behind the injection induced seismicity are still poorly understood. Using experimental results from the Tournemire site, the role of the hydraulic diffusivity of the fault-related structures was explored on the recorded seismicity in the framework of a hydro-mechanical analysis. The results suggest that the induced microseismicity was possibly related to stress perturbations caused by a significant aseismic deformation rather than fluid propagation through hydraulically connected structures
Gibaud, Robin. "Application de la méthode des éléments discrets aux déformations finies inélastiques dans les multi-matériaux." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI086/document.
Повний текст джерелаForming of multiphase materials involves complex mechanisms linked with therheology,morphology and topology of the phases.From a numerical point of view,modeling such phenomena by solving the partial differential equation (PDE) system accounting for thecontinuous behavior of the phases can be challenging.The description of the motion and the interaction of numerous discontinuities,associated with the phases,can be conceptually delicate and computationally costly.In this PhD,the discrete element method (DEM) is used to phenomenologically model finite inelastic strain inmulti-materials.This framework,natively suited for discrete phenomena,allows a flexible handling of morphological and topological changes.Ad hoc attractive-repulsive interaction laws are designed betweenfictitious particles,collectively rearranging to model irreversible strain in continuous media.The numerical behavior of a packing of particles can be tuned to mimic keyfeatures of isochoric perfect viscoplasticity:flow stress, strain rate sensitivity, volume conservation.The results for compression tests of simple bi-material configurations,simulated with the DEM,are compared to the finite element method (FEM) and show good agreement.The model is extended to cope with tensile loads.A method for the detection of contact and self-contact events of physicalobjects is proposed,based on a local approximation of the free surfaces.The potential of the general methodology is tested on complex mesostructuresobtained by X-ray tomography.The high temperature compression of a dense metallic composite is modeled.The co-deformation can be observed at the length scale of the phases.Two cases of ``porous'' material are considered.Firstly,the simulation of the compression and the tension of aluminum alloys with poresis investigated.These pores stem from the casting of the material,their closure and re-opening is modeled,including the potential coalescence occurring at large strain.Secondly,the compression of a metallic foam,with low relative density,is modeled.Typically used in energy absorption applications,the compression up to densification involves numerous interactions between thearms
Radi, Kaoutar. "Matériaux bioinspirés : Optimisation du comportement mécanique en utilisant la méthode des éléments discrets." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI066/document.
Повний текст джерелаNatural materials such as bone and the nacre of some seashells are made of relatively weak building blocks and yet often exhibit remarkable combinations of stiffness, strength, and toughness. Such performances are due in large part to their brick and mortar architectures. Many efforts are devoted to translate these design principles into synthetic materials. However, much of the progress is based on trial-and-error approaches, which are time consuming and do not guarantee that an optimum is achieved.Modeling is an appealing alternative to guide the design and processing routes of such materials. In this work, we develop a numerical model based on Discrete Element Method (DEM) to understand the reinforcement mechanisms and optimize the mechanical properties of nacre-like materials based on their microstructural parameters. The model follows the crack propagation, accounts for different reinforcement mechanisms, and quantitatively assess stiffness, strength, and toughness. An interesting approach, based on EBSD imaging, is presented to model the real material and its different microstructural variations. Results are then combined to provide design guidelines for synthetic brick-and-mortar composites comprising with only brittle constituents
Jeune, Francois. "Dia : le déplacement dans la peinture comme méthode." Paris 1, 2004. http://www.theses.fr/2004PA010569.
Повний текст джерелаRemy, Laurent. "Mise en place d'une nouvelle méthode de conception orientée DFM." Phd thesis, Université de Provence - Aix-Marseille I, 2010. http://tel.archives-ouvertes.fr/tel-00524319.
Повний текст джерелаRemy, Laurent. "Mise en place d'une nouvelle méthode de conception orientée DFM." Phd thesis, Aix-Marseille 1, 2010. https://theses.hal.science/tel-00524319.
Повний текст джерелаThe first part of this thesis presents a state of the art of different DFM approaches in the industrial production flow. A new DFM design methodology is defined. It is called DFM², and it is mainly based on the intensification of interactions between design and process. The cell design is the center of these interactions in order to apply DFM optimizations before the circuit conception. The following of the study presents results about the decrease of the design dependence versus process variations in many domains, such as planarity or lithography for both FEOL and BEOL. A statistical study about the metallization step is then proposed, in order to model the impact of metal filling patterns on electrical performances of circuits. The results obtained allow defining new simulations corners in order to take into account this effect at the cell design step. Finally, an aided-cell design tool (DUTY) is proposed. Its goal is to help designers to adopt DFM² methodology by proposing DFM optimizations, mainly based on previous obtained results. Furthermore, the goal of DUTY is to correlate DFM modifications with yield optimization
Antoni, Rodolphe. "Optimisation des mesures d'interrogation neutronique active par couplage d'une méthode de correction des effets de matrice." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY014.
Повний текст джерелаThe fissile mass in radioactive waste drums filled with compacted metallic residues (spent fuel hulls and nozzles) produced at AREVA La Hague reprocessing plant is measured by neutron interrogation with the Differential Die-away measurement Technique, on the waste compaction facility (ACC). In the future, old hulls and nozzles mixed with ion-exchange resins will be measured. The ion-exchange resins increase neutron moderation in the matrix, compared to the waste measured in the current process. In this context, a matrix effect correction method based on a drum monitor (3He proportional counter) has been studied. The feasibility of the method was first performed with the R&D measurement cell PROMETHEE 6, showing a good correlation between the monitor signal and the matrix effect correction, and the capability of MCNP simulations to reproduce experiments and to estimate the performances of the proposed correction. Therefore, the industrial implementation of the method and the assessment of its final performances have been studied by numerical simulation. Calculations demonstrate that the method allows keeping the highest error on the measured fissile mass below roughly a factor of 2, while the matrix effect without correction ranges on 2 orders of magnitude. In addition, the analysis of experimental data from the current process shows a good correlation between known physical properties of the matrix (moderation and absorption) and the monitor signal, demonstrating the reliability of the proposed approach. According to these satisfactory results, this correction method will be implemented on the industrial station. More generally, this method could be applied to similar waste measurement systems
Durand, Capucine. "Stabilité des digues sous chargement sismique : vers une nouvelle génération de méthodes simplifiées." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAU021/document.
Повний текст джерелаEmbankments are strategic facilities that, among other things, protect population from flooding and canalize rivers for energy production or for irrigation concerns. Since their rupture can lead to terrible consequences, they must remain stable, especially in case of earthquake. However, given the very large length of embankments, it is rarely possible to conduct complete investigations and complex numerical models in regions of moderate seismicity. Therefore, simplified tools to estimate the dynamic response of embankments using accessible embankments’ features are necessary to estimate their capacity to resist seismic loadings. Existing simplified methods, generally developed to assess the dynamic response of embankment-dams, turn out to be inappropriate to study the particular case of embankments along rivers – or other types of embankment, with small height and large length. The majority of these simplified methods do not take into account site effects: they assume the presence of rock directly at the base of the embankment, whereas most of large length embankments are located in alluvial valleys. Two methods only - Sarma(1979) and Papadimitriou(2014) - take into account the interaction between the embankment and its soil foundation. However, the first one relies on strong assumptions (among others, that the bedrock is considered rigid and that the viscous damping is supposed to be both spatially uniform and very large) and the second one is limited to tall embankments (higher than 20 si{m}).The method developed in this thesis relies on assumptions that are more realistic: it considers geometries adapted to large length embankments, it accounts for the presence of a soil foundation and includes an energy dissipation process consistent with expected levels of strain. A numerical parametric study is performed based on the computation with the spectral element method of the viscoelastic response of a large set of embankments spanning a wide range of geometrical and mechanical properties. In order to take into account nonlinearity, damping and shear modulus reduction are adapted in each point of the numerical models according to the results of a set of 1D linear equivalent computations. A new simplified method is derived from the obtained numerical results using artificial neural networks. Abacuses are produced from the neural networks so that engineers can have at their disposal a visual tool. This thesis leads to a simplified method that uses some accessible features of embankments as input parameters. The ability of classical geophysical methods to provide those input parameters is further estimated on four sites corresponding to different realistic configurations
Tran, Duc Kien. "Modélisation numérique discrète de l'érosion interne par renard hydraulique dans les barrages ou digues en terre." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC055/document.
Повний текст джерелаThe work reported in this thesis consists in a discrete modelling of the backward front propagation of an erosion pipe, as can take place in embankment dams or dikes. Some numerical tools have been developed to this end, based on the coupling between the Discrete Element Method (DEM) and the Lattice Boltzmann Method (LBM) for the representation of the solid and uid phases, respectively. The implementation of DEM follows a standard molecular dynamics approach and the interaction among grains are regulated by unilteral frictional visco-elastic and breakable visco-elastic bonds, in order to take into account a slightly cohesive soil behaviour. The LBM was implemented according to the Multiple Relaxation Time (MRT) scheme along with an interpolated non-slip conditions for moving boundaries, in order to improve the numerical stability of the calculations. The coupling scheme is described along with the criteria for the numerical parameters of the two methods. A representative specimen of a granular soil located at the front of an erosion pipe is first assembled by a \dry" preparation precedure and then tested under fully-saturated conditions and increasing hydraulic load over time. Backward erosion is takes place in the form of clusters of grain being eroded at the erosion front after a degradation of the material due to the breakage of tensile bonds. The other interesting feature that was observed is the creation of arches of compressive force chains. These arches enabled the specimen to maintain a stable or metastable configuration under the increasing hydraulic load
Bednarek, Xavier. "Simulation de l'homogénéisation de poudres dans un mélangeur conique à vis par la méthode des éléments discrets." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEM016.
Повний текст джерелаThe homogenization of powders in a conical screw mixer is studied with numerical simulations using the discrete element method (DEM). Following a literature review, two major aspects are presented: a robust calibration method of the numerical model and the study of the mixing process itself.The aim of the calibration of the DEM model is the replication of laboratory measurement by a simulation. We show that the simulation of the measurement of the yield locus with the Freeman Technology’s FT4 shear cell experiment is the best option. We developed an automated and robust simulation procedure. The difficulty of depicting a grain of real powder by a numerical one required some considerations on the parameters to be calibrated. We conduct a sensitivity analysis on a wide range of parameters values, whether they are parameters of the force models or those called "collective" - i.e. related to the number of grains used and to the particle size distribution. The Efficient Global Optimization (EGO) algorithm is used to optimize the degree of fitness between the numerical measurements and the experimental ones.The numerical study of the mixing process was conducted with one million particles, for several configurations. We discuss the issue of the scale-up, from the test mixer to the production mixer. We perform different analysis methods based on various mixing indices and study velocity fields, granular temperature and dispersion. A time extrapolation method based on Kuhn’s Hungarian algorithm solving the assignment problem was also implemented and tested with good results
Tran, Quoc Anh. "Modélisation numérique du comportement des milieux granulaires à partir de signaux pénétrométriques : approche micromécanique par la méthode des éléments discrets." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22561/document.
Повний текст джерелаIn the field of in situ mechanical characterization of soils, penetration tests are commonly used. Penetration tests measure the properties of soils in the domain of large deformations. The tip resistances, deduced from pile driving theory, can be measured either in dynamic conditions (q d ) either in static conditions (q c ). Recently, the measurement technique in dynamic conditions has been improved and it is now possible to record the whole response of the soil during one impact in terms of tip force and penetration distance. The exploitation of this new curve provides information not only on dynamic tip resistance but also on additional mechanical parameters involved during the driving of the tip. The objective of this work is to develop a numerical model in 2D able to reproduce the penetrometric record obtained experimentally by static or dynamic penetration tests. This model is based on the discrete element method with a simple linear contact model. After the validation of the model, a parametric study was performed essentially on the loading type (static or dynamic), the penetration rate, the particle size of the granular material and the arrangement (density variation). Besides the influence of these parameters on the penetrometer signals and the tip resistance, a particular attention was focused on micromechanical analysis: energy dissipation in the medium, force chain evolution, contact orientation. This analysis requires the development of specific numerical tools to better understand the penetration mechanism and try to explain the macroscopic mechanical response obtained. The penetration rate influences significantly only in the dense flow regime on the static and dynamic penetration tests. There is no significant microscopic difference between static and dynamic penetration tests with similar penetration rates. Regarding the influence of the characteristics of the material, the numerical results obtained conform to the real results when the particle friction or the compactness of the medium varies. Concerning the particle size, the dynamic signal variation and the dynamic tip force increases when the average particle diameter increases
Shahzad, Muhammad Kashif. "Exploitation dynamique des données de production pour améliorer les méthodes DFM dans l'industrie Microélectronique." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00771672.
Повний текст джерелаLiu, Hua. "Nouveau procédé d'enrobage de particules en voie sèche et modélisation numérique : préparation de catalyseur solide propre pour la méthanisation." Electronic Thesis or Diss., Centrale Lille Institut, 2021. http://www.theses.fr/2021CLIL0016.
Повний текст джерелаThe objective of this thesis is to propose a new methodology – dry particle coating technique to prepare catalyst supports for the methanation reaction. Dry particlecoating is considered as an environmentally friendly and low-cost technique. However, it is crucial to understand the mechanism of the dry coating process, the factorsaffect the coating performance, the evaluation of the coating quality, the large-scale production as well as the exploration of new application fields.In this work, the method of preparing new catalyst supports is to coat γ-Al2O3 and 316L steel (S.S316L) particles with TiO2, SiO2, and Zeolite nanoparticles. However,these powders (TiO2, SiO2, and Zeolite) are highly cohesive and form agglomerates of uncontrollable sizes, the nanoscale of the powders poses a major problem inthe accuracy of size measurements. The coating process requires analysis of the nanoparticles. Four analytical techniques were applied and compared. The basicprinciple of the dry particle coating process is the mixing of particles under mechanical force (impact/compression/shear force). Host particle: γ-Al2O3 and S.S316Lhave an average diameter of about 67 μm and 98.3 μm will be used as host particles to prepare new carriers. The guest particles: TiO2, SiO2 and Zeolite with nanosizewill be used to coat the surface of γ-Al2O3 and S.S316L to prepare the new substrates (such as TiO2/S.S316L, SiO2/S.S316L, Zeolite/S.S316L and TiO2/γ-Al2O3,SiO2/γ-Al2O3, Zeolite/γ-Al2O3,). The coating of particles in dry process is due to mechanical/shear forces and it depends on collisions, particle movements, interactionsbetween particles and the impact of operating conditions (the rotation speed and coating time) in the mixer. A numerical modeling DEM (Discrete Element Method)has been implemented to answer and explain the phenomena and the coating process.The results of the analysis of the nanoparticles showed that the technique of diffraction/laser scattering (LD) highlights a larger size of particle of the nanopowder(overestimation) on the other hand the dynamic diffusion of the light (DLS) shows a smaller size. Transmission electron microscopy (TEM) indicates the smallerdiameter of the nanopowder. The coating results highlight a good coating by SiO2, TiO2, and Zeolite nanoparticles on the surface of γ-Al2O3 and S.S316L under 3500rpm and 5 min. However, for the same guest particles with different host particles, the S.S316L coating shows excellent coating. Numerical modeling reveals that themain factors affecting the simulation are: rotational speed and particle size. Simulation of the coating indicates that the interfacial energy between the host and theguest is the main parameter affecting the coating
Abdulhay, Enas. "Une nouvelle méthode non-invasive d'estimation cycle à cycle du volume d'éjection cardiaque dans le signal de plethysmographie respiratoire par inductance : algorithme de "double décomposition empirique"." Université Joseph Fourier (Grenoble ; 1971-2015), 2009. http://www.theses.fr/2009GRE10220.
Повний текст джерелаThe main objective that guides the signal processing approaches ofthis thesis is the development of a tool that oould be part of an integrative physiology approach where, at each scale, the model of signais may be different We seek here the restriction of asstnnptions a priori to a set: of rules goveming the physiological interactions between physiological functions in the absence of fannal and mathematical assumptions. We applied this approach to the problem of cardiac waves detection and estimation of cycle-to-cycle stroke volume in the RIP signal (Respiratory Inductive Plethysmography). The empirical decomposition approach seems to be particularly adapted to our logic. We propose here the first version of an algorithm based on RIP double decomposition. The method and its COITeSpül1ding tools have been tested on two types of data, simulated signais and real signais recorded at healthy volunteers. Our aim is also therefore to develop a cardio-respiratory model that can serve as a tool for ventilatory, cardiac and RIP signals simulation along with the simulation of the effect of each system on the other. The results show that the proposed method is suitable for RIP signal analysis and for stroke volume estimation
Mazor, Alon. "Modelling of roll compaction process by finiite element method." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2017. http://www.theses.fr/2017EMAC0009/document.
Повний текст джерелаIn the pharmaceutical industry, dry granulation by roll compaction is a process of size enlargement of powder into granules with good flowability for subsequent die compaction process. Understanding the roll compaction process and optimizing manufacturing efficiency is limited using the experimental approach due to the high cost of powder, time-consuming and the complexity of the process. In this work, a 3D Finite Element Method (FEM) model was developed to identify the critical material properties, roll press designs and process parameters controlling the quality of the product. The Drucker-Prager Cap (DPC) model was used to describe the powder compaction behavior and was determined based on standard calibration method. To overcome the complexity involving two different mechanisms of powder feeding by the screw and powder compaction between rolls, a novel combined approach of Discrete Element Method (DEM), used to predict the granular material flow in the feed zone and the Finite Elements Method (FEM) employed for roll compaction, was developed. Lastly, for a more realistic roll compaction modelling, allowing the fluctuation of the gap between rolls, a Coupled-Eulerian Lagrangian (CEL) approach was developed. FEM simulation results clearly show the effect of different process parameters on roll pressure and density distribution in the compaction zone of powder between the rolls. Moreover, results show that using a cheek-plates sealing system causes a nonuniform roll pressure and density distribution with the highest values in the middle and the lowest at the edges. On the other hand, the resultant pressure and density distributions with the rimmed-roll obtained higher values in the edges than in the middle and overall a more uniform distribution. The combined DEM-FEM methodology clearly shows a direct correlation between the particle velocity driven by the screw conveyor to the feed zone and the roll pressure, both oscillating in the same period. This translates into an anisotropic ribbon with a density profile varying sinusoidally along its length. To validate the results, the simulations are compared with literature and experimentally measured values in order to assess the ability of the model to predict the properties of the produced ribbons
Taforel, Paul. "Apport de la Méthode des Éléments Discrets à la Modélisation des Maçonneries en Contexte Sismique : Vers une Nouvelle Approche de la Vulnérabilité Sismique." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2012. http://tel.archives-ouvertes.fr/tel-00801814.
Повний текст джерелаBéreaux, Yves. "Simulation numérique d’écoulements de fluides viscoélastiques à formulation intégrale, par la méthode des tubes de courant." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0005.
Повний текст джерелаHusseini, Hassan Al. "Adaptation de la méthode de corrélation d'images numériques pour la gestion des discontinuités du milieu et de la transformation." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2270/document.
Повний текст джерелаThe development of the digital image correlation method (DIC) for the management of discontinuities of the material and the transformation is discussed in this thesis. As we know, the framework for the use of the optical measurement methods i.e. of continuum mechanics requires a continuity of: i) domain and ii) transformation. To treat those discontinuities, we can consider a piecewise continuity (material and transformation). In the case of DIC method, this can be done by adapting locally the shape and size of the correlation subsets to the zone of interest and its kinematics. A novel way to do it, is by using masks: an object mask to process material discontinuities and a discontinuity mask to process transformation discontinuities. However before the implementation of masks in the correlation process, several experimental displacement tests on models reproducing the two types of discontinuity at small scale were performed. Those tests proved the influence of discontinuities on the degradation of the measurement accuracy by DIC. Then, tensile tests were conducted on a polycarbonate made specimen knowing a mode I opening or closing crack. After implementing masks in the correlation software Correla, the calculation of displacement and deformation fields was successfully performed on the surface of this specimen for all its edges, demonstrating the effectiveness of the adapted DIC
Louati, Haithem. "Experimental and numerical study of humid granular material : influence of liquid content in quasi-static regime." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2016. http://www.theses.fr/2016EMAC0008/document.
Повний текст джерелаWe study experimentally and numerically the shear behaviour of wet granular material. We investigate the effect of the liquid content and the applied normal stresses to this behaviour. An annular shear cell was used to carry out the experiments, for a large range of applied normal stress from about 0.3 kPa to 12 kPa. The results give the variation of the shear stress at steady-state as a function of the normal stress for a wide range of liquid fraction. The incorporated liquid goes from forming bridges at the contact point to completely filling the space between grains. The shear resistance and the voidage fraction variations with the liquid fraction were analysed. Depending on the applied normal stress and the liquid fraction, different regimes of the shear resistance were identified. The discrete element method (DEM) was used to gain a microscopic understanding of the shear behaviour of dry and partially wet granular material in the shear cell. Large size glass beads were used to speed up the computational time and to facilitate characterisation at the particle scale. First, the influence of the microscopic properties of the particle (The Young’s modulus and the sliding friction) on the macroscopic properties of dry and wet granular materials (the coordination number, the voidage fraction, the shear ratio and the velocity of particles) was investigated. Secondly, the shear behaviour of the partially wet granular material for different liquid fractions and normal stresses was studied. The capillary forces and the number of liquid bridges were quantitatively analysed
Pimentel, Torres Gaspar Ana Patricia. "Contribution to control uncertainties in numerical modelling of dam performances : an application to an RCC dam." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2014. http://www.theses.fr/2014ECAP0053/document.
Повний текст джерелаThe use of fully probabilistic approaches to account for uncertainties within dam engineering is a recently emerging field on which studies have been mostly done concerning the safety evaluation of dams under service. This thesis arises within this framework as a contribution on moving the process of risk analysis of dams beyond empirical knowledge, applying probabilistic tools on the numerical modelling of a roller compacted concrete (RCC) dam during its construction phase.The work developed here aims to propose a methodology so as to account for risks related to cracking during construction which may compromise the dam’s functional and structural behaviour.In order to do so, emphasis is given to uncertainties related to the material itself (i.e.strength, water-to-cement ratio, among others) as well as to ambient conditions during the construction phase of RCC dams. A thermo-chemo-mechanical model is used to describe theRCC behaviour. Concerning the probabilistic model, two aspects are studied : how the uncertainties related to the input variables are propagated through the model, and what is the influence of their dispersion on the dispersion of the output, assessed by performing a global sensitivity analysis by means of the RBD-FAST method. Also, spatial variability of some input parameters is accounted for through bi-dimensional random fields. Furthermore, a coupling between reliability methods and finite element methods is performed in order to evaluate the cracking potential of each casted RCC layer during construction by means of a cracking density concept. As an important outcome of this applied research,probability curves for cracking density within each casted layer as functions of both age and boundary conditions are predicted, which is believed to be an original contribution of this thesis. The proposed methodology may therefore be seen as a contribution to help engineers understand how uncertainties will affect the dam behaviour during construction and rely on it inthe future to improve and support the design phase of the dam project
Taha, Habib. "Mechanical behavior of eroded soils : numerical study based on the DEM." Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4029.
Повний текст джерелаSuffusion can induce a loss of fine particles to granular soils and consequently a modification of their mechanical behavior. In this PhD thesis, we aim to study the effect of the loss of fine particles caused by suffusion on mechanical properties of soils at the macroscopic and microscopic scales by using the Discrete Element Method (DEM). Granular samples composed of spherical particles with a gap-graded particle size distribution (PSD) are simulated by the DEM. Due to a very high computational cost, the fluid flow through the void space between solid particles is not simulated. Instead, we propose a representation of the internal state of soils after suffusion at three different levels with increasing complexity. For the level 1, a sample considered as eroded is generated at a target density and with a fine content lower than that of the original sample. The level 2 consists in removing a fraction of fine particles from the original sample at a given stress state. We proposed thus a method to identify the loose fraction composed of particles which do not carry significantly stresses. The level 3 aims to take into account the transport of fine particles in the pore network of the solid skeleton and the blockage of fine particles by constrictions. The key point in this model is how to describe the pore network. This study showed that fine particles can have a negligible effect, positive or negative effect on the shear strength depending on fine content. A removal of fine particles causes a significant reduction in shear strength to gap-graded soils. It was also showed that a random removal of fine particles leads to a greater reduction in shear strength than a removal of only fine particles in the loose fraction. For the description of the pore network of the solid skeleton, we propose a new method for merging neighboring tetrahedra issued from the Delaunay triangulation. This pore network will be incorporated into a model to take into account the transport and blockage of fine particles within the pore network of the solid skeleton
Mesnier, Aline. "Étude expérimentale et simulation de la ségrégation mécanique et thermique de billes millimétriques dans un séchoir de type tambour tournant." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1046/document.
Повний текст джерелаProduct homogeneity issue during mechanical and thermal processing of a bi-dispersed bed with two particles’ sizes or two particles’ densities in a horizontal rotary drum was considered. In the first part, the mixing of milli-metric size spherical beads in a two-dimensional drum was simulated by means of a commercial discrete element software and optically observed in a specially designed laboratory scale device. The spatial distribution of the particles in the front bed section, the radial mechanical segregation index and the dynamic slope angle were analyzed. After adjusting the friction coefficient, the simulation results were close to the experimental ones. Important phenomena of radial and axial segregation have been highlighted. The radial segregation index was found to be significantly decreased by applying an important number of long baffles, while using few short baffles had practically no influence on segregation intensity. In the second part, the heating of the bed of spherical beads in a 2D drum with hot peripheral wall was simulated by means of the discrete element software. Mono-dispersed, gaussian-dispersed and bi-dispersed beds (same as in part 1) were considered. The mechanical segregation and the thermal segregation indexes were calculated for the different types of bed and for different baffles configurations. The thermal segregation was found to be generally enhanced by the mechanical segregation and reached its highest values for the bi-density bed. Increasing the number and the length of the baffles considerably improved the overall heating rate and the thermal homogeneity of the considered beds
Tatin, Maxime. "Comportement thermique des barrages en béton : amélioration des modèles d'analyses physico-statistiques des mesures de déplacements." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI059/document.
Повний текст джерелаConcrete dam displacements are influenced by various factors such as hydrostatic load, thermaleffects, and irreversible effects. In order to interpret measurements, to split apart all the differentinfluences and to identify a potential pathological behaviour, physico-statistical modelssuch as multi-linear regression are commonly employed in dam engineering. Nevertheless, thethermal component estimation is an important source of uncertainty for these models. Thus, theobjectives of this thesis are to highlight the mechanism that generate thermal displacement, toclarify model hypothesis, to determine the main sources of uncertainty from environnemental influencesso as to propose improvements of statistical modelling. Two original physico-statisticalmodels have been develloped to account for water temperature which has been identified as amain source of uncertainty. Firstly, only the mean value has been introduced. Then, in parallelto in-situ measurements, realistic temperature profils are accounted for over the dam’s height.These models have been tested both on a virtual environnement (finite element model) and ona real study case. The results show a significant reduction of the residual dispersion and anincrease of the predictive capacity of the models
Maione, Riccardo. "Modélisation d’un système de pyrogazéification de la biomasse." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0088/document.
Повний текст джерелаThis work is part of the LORVER project, funded by Grand Est Région and FEDER. It aims to create a non-food biomass production chain by using and upgrading brownfields and industrial by-products in Lorraine. One possible valorization process of the produced biomass is a thermochemical pyro-gasification process that would generate heat and electricity. This process, developed by SEA Marconi, involves three different reactors: a rotating drum, for the pyrolysis of wood particles, the heat required being brought by hot steel balls; an Auger for partial oxidation of the char that allows heating the steel balls; a reactor for tar cracking. The aim of this thesis is to develop models that can predict the behavior of the system. 3D models based on DEM or CFD - DEM were designed for the modeling of phenomena involved in the system. The DEM model parameters were first calibrated in a rotating drum. The DEM simulation was able to predict in a satisfactory manner segregation between steel balls and non-spherical wood particles; it also helped to design a 1D thermal and chemical model, on which a sensitivity study has been done. A CFD - DEM model has been coded and validated on a granular rheometer allowing the simulation of the char oxidation reactor, even if this simulation was not possible during the PhD
Vo, Quoc Thang. "Imagerie d'essais mécaniques sur des composites à matrice métallique : contribution expérimentale à la validation de méthodes d'homogénéisation et identification de propriétés mécaniques par phases." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20151/document.
Повний текст джерелаThis work is focused on a matrix/inclusion metal composite. A simple method is proposed to evaluate the elastic properties of one phase while the properties of the other phase are assumed to be known. The method is based on both an inverse homogenization scheme and mechanical field's measurements by 2D digital image correlation. The originality of the approach rests on the scale studied, i.e. the microstructure scale of material: the characteristic size of the inclusions is about few tens of microns. The evaluation is performed on standard uniaxial tensile tests associated with a long-distance microscope. It allows observation of the surface of a specimen on the microstructure scale during the mechanical stress. First, the accuracy of the method is estimated on ‘perfect' mechanical fields coming from numerical simulations for four microstructures: elastic or porous single inclusions having either spherical or cylindrical shape. Second, this accuracy is estimated on real mechanical field for two simple microstructures: an elasto-plastic metallic matrix containing a single cylindrical micro void or four cylindrical micro voids arranged in a square pattern. Third, the method is used to evaluate elastic properties of inclusions with arbitrary shape in an oxidized Zircaloy-4 sample of the fuel cladding of a pressurized water reactor after an accident loss of coolant accident (LOCA). In all this study, the phases are assumed to have isotropic properties
Ben, Turkia Salma. "Etude expérimentale et numérique du comportement mécanique des matériaux granulaires : De la simulation discrète d'essais de laboratoire à la mise en place d'une procédure de calibration des paramètres d'entrée." Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2020. http://www.theses.fr/2020MTLD0004.
Повний текст джерелаThe processing, transport, handling and storage of granular materials underlies the operations of numerous industries. Thus, reliably predicting the dynamics of granular materials is critical for successful process operation and sensible process optimization. Granular materials are complex systems that can display solid, liquid and gas phases that are often characterized by nonfrivolous transitions between static, quasi-static and dynamic states. Needless to say, the manifestation of segregation, arching and jamming can have dire consequences for manufacturers. Predicting the bulk behavior of granular media requires a good understanding of the dominant mechanisms involved at grain or particle level. It is therefore essential to numerically simulate at the grain or particle scale to accurately predict granular dynamics over all regimes. In the discrete element method (DEM) there are constitutive models that describe the material responses for different mechanical loading conditions. However, significant computational resources are required to simulate large number of particles often making bulk and industrial scale simulations intractable.In this study, we use the BlazeDEM3D-GPU simulation framework that uses GPU (Graphic Processing Unit) compute, allowing DEM simulations to be conducted tens to hundreds times faster. This tremendous increases in compute efficiency creates new opportunities in DEM to solve problems that previously were thought to be too computationally demanding. The usefulness and generality of the discrete element model strongly depends on the quality of the calibration process of the model. The process we proposed first conducts a virtual calibration of a bulk experiment that uses design of experiments, optimization and variation maps over the parameter domain to identify known optima in the virtual problem. This not only ensures a better match between the experimental and numerical model responses but also the uniqueness of the model parameters themselves. In particular, two distinct experimental and virtual calibration approaches are investigated to verify the generality of the calibrated DEM models for laboratory scale applications and future industrial applications
Desbordes, Paul. "Méthode de sélection de caractéristiques pronostiques et prédictives basée sur les forêts aléatoires pour le suivi thérapeutique des lésions tumorales par imagerie fonctionnelle TEP." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR030/document.
Повний текст джерелаRadiomics proposes to combine image features with those extracted from other modalities (clinical, genomic, proteomic) to set up a personalized medicine in the management of cancer. From an initial exam, the objective is to anticipate the survival rate of the patient or the treatment response probability. In medicine, classical statistical methods are generally used, such as theMann-Whitney analysis for predictive studies and analysis of Kaplan-Meier survival curves for prognostic studies. Thus, the increasing number of studied features limits the use of these statistics. We have focused our works on machine learning algorithms and features selection methods. These methods are resistant to large dimensions as well as non-linear relations between features. We proposed two features selection strategy based on random forests. Our methods allowed the selection of subsets of predictive and prognostic features on 2 databases (oesophagus and lung cancers). Our algorithms showed the best classification performances compared to classical statistical methods and other features selection strategies studied
Skander, Achraf. "Méthode et modèle DFM pour le choix des procédés et l'intégration des contraintes de fabrication vers l'émergence de la solution produit." Troyes, 2006. http://www.theses.fr/2006TROY0001.
Повний текст джерелаIn a general context of concurrent engineering, Design for Manufacturing tackles the problem of acceptable manufacturing processes selection (product analysis) and integration, as soon as possible, of constraints related to these processes in product definition (constraints synthesis). The research results are related to the specification of product definition method that aims to manufacturing processes selection and integration of their constraints during product design. On the one hand, this DFM method analyzes the product data issued of processes (form, roughness, tolerance interval, etc. ). On the other hand, it treats manufacturing information (manufacturing processes constraints). It manages simultaneously these data using a skin-skeleton model (product-processes interface model). The use of the skin and skeleton features is justified by their capacity to make a simplify product representation that gives possibility to integrate both design and manufacture data and therefore defines the product data at least commitments
Vergez, Guillaume. "Méthodes numériques avec des éléments finis adaptatifs pour la simulation de condensats de Bose-Einstein." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR014/document.
Повний текст джерелаThe phenomenon of condensation of a boson gas when cooled to zero degrees Kelvin was described by Einstein in 1925 based on work by Bose. Since then, many physicists, mathematicians and digitizers have been interested in the Bose-Einstein condensate and its superfluidity. We propose in this study numerical methods as well as a computer code for the simulation of a rotating Bose-Einstein condensate.The main mathematical model describing this phenomenon is a Schrödinger equation with a cubic nonlinearity, discovered in 1961: the Gross-Pitaevskii (GP) equation. By using the software FreeFem++ and a finite elements spatial discretization we solve this equation numerically. The mesh adaptation to the solution and the use of finite elements of order two allow us to solve the problem finely and to explore complex configurations in two or three dimensions of space. For its stationary version, we have developed a Sobolev gradient method or an internal point method implemented in the Ipopt library. .For its unsteady version, we use a Time-Splitting method combined with a Crank-Nicolson scheme ora relaxation method. In order to study the dynamic and thermodynamic stability of a stationary state,the Bogoliubov-de Gennes model proposes a linearization of the Gross-Pitaevskii equation around this state. We have developed a method to solve this eigenvalues and eigenvector system, based on a Newton algorithm as well as the Arnoldi method implemented in the Arpack library
Pizette, Patrick. "Simulation de la compaction de poudres céramiques par la méthode des éléments discrets : application à la mise en forme des combustibles nucléaires mixtes." Grenoble INPG, 2009. http://www.theses.fr/2009INPG0190.
Повний текст джерелаNuclear mixed oxide fuel (MOX) is formed as pellets by cold compaction of a powder blend of oxides of uranium and plutonium followed by sintering. Because of the variability of incoming powders in the process and taking into account the need to maintain constant industrial settings for processing significant quantities of pellets, the compaction process may generate some rejection during controls. In particular, compact strength and dimensional precision are key features of the industrial process. The Discrete Element Method (DEM), which has been used here, offers a powerful tool for understanding and simulating the compaction stage. It relies on an explicit modeling of the particulate nature of the uranium oxide powders. Two models, at the length scale of the aggregate of crystallites and at the length scale of the crystallites are used to simulate the powder compaction. A methodology, based on numerical experiments, is proposed to generate constitutive laws to feed a finite element code. Finally, the modeling at the crystallite length scale is used to identify the main microstructural parameters that control the compact strength
Nguyen, Trung Kien. "Modelisation multi-echelle des materiaux granulaires frottant-cohesifs." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-01062483.
Повний текст джерелаAl, Tfaily Bilal. "Capacité prévisionnelle de la modélisation discrète pour application aux ouvrages géotechniques complexes." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALI077.
Повний текст джерелаGeotechnical engineering is a crucial field in the design and construction of foundations, embankments, tunnels, and other structures interacting with soil and rock. However, the description of the elastoplastic response of soil, with preponderant non-linear and non-reversible deformations together with a non-associative flow rule, is complex. The difficulty is even higher in the case of non-monotonous loading paths where phenomenological constitutive relations require ad-hoc history parameters and advanced experimental tests for their calibration.Discrete element method has been proved to be an effective method in predicting quantitatively the constitutive response of soils, even in the case of complex loadings (with rotation of principal stress directions, or loading/unloading cycles) where conventional elastoplastic constitutive relations may fail to simulate realistic responses. For granular soils with a narrow grading, a direct representation of soil grains by polyhedral particles or with the level set method is possible, whereas for finer soils, or soils with a wider grading, alternative solutions should be considered. Spherical particles with enriched contact laws (e.g. by introducing rolling resistance at the contact) or rather simplified clumps of spheres can be used to keep the model relatively light to tackle further boundary value problems with limited computational cost. However, even if the models provide satisfying results for direct shear tests or drained triaxial compression loading paths compared to experimental measurements, their validation with respect to more complex loading paths as the isochoric compression or the path at constant stress deviator still present difficulties, in particular for initially loose granular assemblies.First, this study aims to compare such different approaches in terms of the prediction abilities at the macroscopic scale of the constitutive responses of soils, particularly for complex loading paths. Two kinds of discrete models are considered: (i) spherical particles with rolling resistance, (ii) simple clumps made of 2 to 6 spheres. The models are calibrated from two drained triaxial compressions on dense and loose Hostun sand. They are then assessed, according to the macroscopic response, on loading paths significantly different from the calibration loading paths (isochoric compressions, circular stress paths in the deviatoric plane, constant deviatoric stress path, etc.).Then, we investigate the importance of the description of the anisotropy of the initial fabric and of the inter-particle friction law in the simulated responses of loose granular assembly to different kinds of loading paths. It shows how the combination of both can modify importantly the simulated responses to some kinds of loading paths. This investigation is carried out for a numerical discrete model made of spheres by comparison with experimental results on sand.Finally, the model is used to simulate the nonlinear interaction between a shallow foundation of building structure and the supporting soil during strong seismic loadings, as tested experimentally for the TRISEE project with a full scale physical model. An adaptative discretization technique is implemented to limit the number of particles in such a boundary value problem and make the computation possible with a conventional desktop computer. Numerical results are benchmarked against experimental measurements from the TRISEE project, and FEM numerical simulations or macro-element models
Lorenat, Jemma. ""Die Freude an der Gestalt" : méthodes, figures et pratiques de la géométrie au début du dix-neuvième siècle." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066079/document.
Повний текст джерелаThe standard history of nineteenth century geometry began with Jean Victor Poncelet's contributions which then spread to Germany alongside an opposition between Julius Plücker, an analytic geometer, and Jakob Steiner, a synthetic geometer. Our questions centre on how geometers distinguished methods, when opposition arose, in what ways geometry disseminated from Poncelet to Plücker and Steiner, and whether this geometry was "modern'' as claimed.We first examine Poncelet's argument that within pure geometry the figure was never lost from view, while it could be obscured by the calculations of algebra. Our case study reveals visual attention within constructive problem solving, regardless of method. Further, geometers manipulated and represented figures through textual descriptions and coordinate equations. We also consider the debates involved as a medium for communicating geometry in which Poncelet and Gergonne in particular developed strategies for introducing new geometry to a conservative audience. We then turn to Plücker and Steiner. Through comparing their common research, we find that Plücker practiced a "pure analytic geometry'' that avoided calculation, while Steiner admired "synthetic geometry'' because of its organic unity. These qualities contradict usual descriptions of analytic geometry as computational or synthetic geometry as ad-hoc.Finally, we study contemporary French books on geometry and show that their methodological divide was grounded in student prerequisites, where "modern'' implied the use of algebra. By contrast, research publications exhibited evolving forms of geometry that evaded dichotomous categorization.The standard history of nineteenth century geometry began with Jean Victor Poncelet's contributions which then spread to Germany alongside an opposition between Julius Plücker, an analytic geometer, and Jakob Steiner, a synthetic geometer. Our questions centre on how geometers distinguished methods, when opposition arose, in what ways geometry disseminated from Poncelet to Plücker and Steiner, and whether this geometry was "modern'' as claimed.We first examine Poncelet's argument that within pure geometry the figure was never lost from view, while it could be obscured by the calculations of algebra. Our case study reveals visual attention within constructive problem solving, regardless of method. Further, geometers manipulated and represented figures through textual descriptions and coordinate equations. We also consider the debates involved as a medium for communicating geometry in which Poncelet and Gergonne in particular developed strategies for introducing new geometry to a conservative audience. We then turn to Plücker and Steiner. Through comparing their common research, we find that Plücker practiced a "pure analytic geometry'' that avoided calculation, while Steiner admired "synthetic geometry'' because of its organic unity. These qualities contradict usual descriptions of analytic geometry as computational or synthetic geometry as ad-hoc.Finally, we study contemporary French books on geometry and show that their methodological divide was grounded in student prerequisites, where "modern'' implied the use of algebra. By contrast, research publications exhibited evolving forms of geometry that evaded dichotomous categorization
Olmedilla, González de Mendoza Antonio. "Grain motion and packing : application to metallic alloy solidification." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0265/document.
Повний текст джерелаSolidification multiphase multiscale modeling of metal alloys is based on the combination of the phenomena at the macroscopic scale of the product and at the microscopic scale of the solidification structures. In this thesis, the random packing of the typical equiaxed grain morphologies in metal alloy solidification is investigated. Firstly, we highlight the hydrodynamic dimensionless parameters governing the grain packing in the melt: the Stokes number, St, the Archimedes number, Ar, and the growth-to-motion ratio, Γ. Subsequently, an experimental setup is designed by hydrodynamic similarity with the actual solidification packing phenomenon in order to investigate the influence of the equiaxed grain geometry and the hydrodynamic conditions on the average solid packing fraction. Additionally, a numerical Discrete Element Method tool is developed to complement the experimental work by accessing to those granular variables which result difficult to be experimentally obtained such as the local packing fraction, the contacting neighbors and the particle orientation. Packing fractions between approximately 0.53 and 0.67 are measured and computed for the spherical noncohesive grains, for different hydrodynamic, frictional and polydispersity conditions, whereas values down to approximately 0.30 are found for noncohesive dendrite envelopes. Finally, we investigate the packing dynamics, which is the transition from a sedimentation regime to the mechanical equilibrium (packing). The evolution of the local solid fraction, contacting neighbors, mechanical contacts and grain orientation are given
Yaseri, Alireza. "Analysis of earth dam-flexible canyon interaction by 3D hybrid FEM-SBFEM." Doctoral thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/70281.
Повний текст джерелаThe canyon surrounding a dam can be assumed as an unbounded domain, and the geometry and flexibility of a canyon are parameters that greatly affect the values of natural periods in earth dams. In this thesis, in order to take into account these two effects, canyons are modeled by SBFEM, and earth dams, which have limited geometries, are modeled by FEM. The hybrid FEM-SBFEM technique used for the dynamic three-dimensional analysis of soil-earth dam interactions is validated with results available in the literature. Because the dynamic-stiffness matrix of the unbounded domain is complex and frequency-dependent, the classical mode-superposition method is not straightforward for a soil-structure interaction system, and thus, to obtain their fundamental natural frequencies, the modeled dams were excited in the upstream-downstream direction. The natural periods of earth dams in canyons with different geometries shapes and impedance ratios are obtained, and are found to have significant effects on the dams’ natural periods. The results are compared with actual recorded data, and it is found that the graphs put forward in this study may be used by practical engineers for the estimation of natural periods of earth dams in canyons with different shapes and material properties. Several amplification functions corresponding to different canyon conditions are obtained by applying a uniform displacement at the canyons’ boundaries. A comprehensive study is performed to examine the effects of canyon geometry and flexibility on the steady-state responses of the dams, and it is found that these two effects significantly influence the amplification functions. While the flexibility of the canyon does affect the maximum amplification function value, this value does not change for earth dams in canyons that have different shapes but the same length. In addition, the lateral responses of earth dams in the time domain are computed in order to analyze the aforementioned effects under an actual earthquake. The proposed amplification functions are used to compare the recorded response spectra of the El Infiernillo dam under the two 1966 earthquakes with the calculated amplification function, and a reasonable agreement is observed between them. The equivalent linear method (EQL) is implemented into the FEM, and the FEM-SBFEM technique is extended in order to take into consideration the effect of earth dams’ nonlinear behavior. It is observed that such nonlinear behavior greatly affects the natural frequency, the amplification function, and peak crest acceleration of earth dams located in canyons. The effects of canyon geometry and flexibility on the nonlinear behavior are examined, and it is found that by increasing canyon flexibility, the effect of nonlinearity is decreased. The El Infiernillo dam is modeled by the 3D nonlinear FEM-SBFEM, and comparison of the crest amplification function obtained by the proposed method with the recorded data shows the accuracy of the nonlinear FEM-SBFEM.
Al-Arkawazi, Sherko Ahmad Flamarz. "Modélisation des interactions fluide-milieu granulaire par couplage CFD-DEM, incluant les transferts thermiques." Amiens, 2014. http://www.theses.fr/2014AMIE0116.
Повний текст джерелаIn this work, we are interested in the study of hydrodynamic and thermal behavior of fluidized beds by numerical simulations. By means of a coupling between the discrete element method (DEM) and computational fluid mechanics (CFD), we are modeling the interaction between a fluid and a granular medium. The interaction is translated through a drag force, and the effect of local concentration of the particles on the drag force is taken into account by a porosity function. Simulation results on a fluidized bed are discussed and compared with experimental ones, especially in terms of height of expansion of the fluidized bed. The influence of friction and restitution coefficients on the macroscopic behavior of the bed is also studied. For example, different geometries of fluidizing columns are modeled. For each of them, simulation results are analyzed, through a fluidization index. These examples illustrate the ability of the coupling CFD–DEM method presented in this work to optimize complex granular flow. We proposed a thermal approach (conduction-convection) based on the finite volume method to calculate the heat transfer between fluid-particle and particle-particle. The effects of dissipation by shock and friction were also taken into account and analyzed. The validation results depicted that the thermal model has proven its effectiveness whether on a fixed or fluidized bed
Farah, Nicolas. "Flow Modelling in Low Permeability Unconventional Reservoirs." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066503/document.
Повний текст джерелаUnconventional low permeability reservoirs present a multi-scale fractured media, including stimulated fractures and natural fractures of various sizes, increasing the heterogeneity and the complexity of the reservoir simulation. This work proposes a methodology to address this challenge, taking into account reservoir key parameters such as fractures locations, orientation, anisotropy and low permeability matrix in a unique model as simple as possible. Using standard Discrete Fracture Models (DFMs), the matrix-fracture interaction is not properly handled due to the large grid cells and very low matrix permeability. In this work, we extended the MINC (Multiple INteracting Continua) method to the DFM in order to improve the matrix-fracture flow exchange. Our DFM based on a MINC proximity function is computed by taking into account all discrete fractures, within a triple-porosity model where the propped fractures are explicitly discretized and other fractures are homogenized. In order to improve the flow exchange between the matrix and fracture media, the matrix grid cell is subdivided according to the MINC proximity function based on the distance to all discrete fractures, by using randomly sampled points. Our approach is particularly useful for multi-phase flow simulations in matrix-fracture interaction with phase change, which cannot be handled by a standard approach. Finally, we applied our technique to synthetic DFM case in a retrograde gas and a tight-oil reservoirs. A good agreement is observed by comparing our results to a reference solution where very fine grid cells were used
Bautista, Rozo Lola Xiomara. "Reconstruction de phase pour la microscopie à Contraste Interférentiel Différentiel." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4045/document.
Повний текст джерелаIn this dissertation we address the problem of estimating the phase from colorimages acquired with differential–interference–contrast (DIC) microscopy. This technique has been widely recognized for producing high contrast images at high lateral resolution. One of its disadvant ages is that the observed images cannot be easily used for topographical and morphological interpretation, because the changes in phase of the light, produced by variations in the refractive index of the object, are hidden in the intensity image. We present an image formation model for polychromatic light, along with a detailed description of the point spread function (PSF). As for the phase recovery problem, we followed the inverse problem approach by means of minimizing a non-linear least–squares (LS)–like discrepancy term with an edge–preserving regularizing term, given by either the hypersurface (HS) potential or the total variation (TV) one. We investigate the analytical properties of the resulting objective non-convex functions, prove the existence of minimizers and propose a compact formulation of the gradient allowing fast computations. Then we use recent effective optimization tools able to obtain in both the smooth and the non-smooth cases accurate reconstructions with a reduced computational demand. We performed different numerical tests on synthetic realistic images and we compared the proposed methods with both the original conjugate gradient method proposed in the literature, exploiting a gradient–free linesearch for the computation of the steplength parameter, and other standard conjugate gradient approaches
Vareilles, Julie. "Etude de l'influence de la distribution de la taille des grains sur le seuil d'érosion des lits de sédiments non cohésifs par la méthode DEM." Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00627859.
Повний текст джерелаFederico, Carlos. "Effets couplés de la température et de la vitesse de déformation sur le comportement mécanique non-linéaire des polymères amorphes : Caractérisation expérimentale et modélisation de la superposition vitesse de déformation-température." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM009/document.
Повний текст джерелаThe present PhD thesis proposes a simplified and accurate strategy for characterising and modelling the mechanical behaviour of amorphous polymers from the quasi-fluid state up to the solid state.The study was carried out on PMMAs with different molar masses and crosslinking degree.First, we addressed the mechanical behaviour in the linear viscoelastic domain using DMTA and rheological tests. Results showed that increasing the molar mas and crosslinking degree increased the elastic and loss moduli as the α-transition. In parallel, using the time-temperature superposition principle allowed determining “equivalent strain rates at reference temperature”.Then, we performed uniaxial tensile and shear uploading-unloading tests at high temperature and coupled with DIC, to characterise the mechanical behaviour at large strain. Additionally, strain rate and temperature effects were coupled by means of the “equivalent strain rate at reference temperature” extracted from observations in the linear domain. Results showed that targeting the same equivalent strain rate lead to the same stress-strain curves, i.e. same mechanical response. This allows reducing the number of experimental tests needed to characterise the mechanical behaviour of amorphous polymers.Finally, a constitutive modelling based in a thermodynamics framework, was used to reproduce the mechanical response of the PMMAs at large deformation. The model presented a good agreement with the experimental data, being able to reproduce viscoelastoplastic, viscoelastic, hyperelastic and viscohyperelastic behaviours for cyclic loading tensile
Zouaghi, Ahmed. "Modélisation multi-échelle du comportement non linéaire et hétérogène en surface de l'acier AISI H11." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2015. http://www.theses.fr/2015EMAC0008/document.
Повний текст джерелаAISI H11 martensitic tool steels are critical mechanical components that behaviour during service is drastically linked to their internal structures and their possible evolution. Their manufacture processes are often at the origin of microstructural changes at the surface, namely the morphology of martensitic laths, the crystallographic orientations, the internal hardening state and the surface profile These aspects can potentially alter the mechanical performance of AISI H11 martensitic steel. In order to get better insight into and optimize its mechanical behaviour, a multi-scale approach involving an experimental investigation and a numerical treatment is taken in this work.The experimental investigation focuses to reproduce, at the laboratory scale, equivalent surfaces to those resulting from tool steels manufacture processes. Specific characterization techniques, namely SEM, EBSD, nanoindentation and altimetry enable to highlight a stereology gradient of the material in surface and sub-surface. The induced local heterogeneities consist in morphology of martensitic laths and crystallographic orientations, internal hardening state and surface profile. In-situ mechanical tests with digital image correlation technique (DIC) are carried out for monotonous quasi-static and tension-tension cyclic loads. An investigation of the local mechanical fields at the surface is thus performed and allows to analyze the localizations schemes of nonlinear strains which are related to stereological artifacts.The numerical treatment is focused on a multi-scale modelling, and more particularly on finite element calculations on virtual microstructures which are generated by Voronoi tesselations. The latters are carried out such that to reproduce martensitic structures and consider a specific orientation relationship between martensitic laths and parent austenitic grains (i.e. Kurdjumov-Sachs) after the heat treatment. The constitutive equations of the (elasto-viscoplastic) crystal plasticity of Méric-Cailletaud are implemented in the finite element code Abaqus in the context of the small strain assumption and the finite strain theory. The formulation of the model in the context of finite strain theory is is given a spatial description where the notion of objective derivative, namely the so called one of Oldroyd or Truesdell, is used in such a way that such formulation is equivalent to a Lagrangian description.The numerical treatment has allowed to qualitatively reproduce the localization patterns at the surface which have been highlighted in the experimental investigation. The influence of the different stereological parameters mentioned above on the local mechanical fields was analyzed. By this approach, it was possible to highlight some elementary mechanisms including interaction and surface effects. Finally, it was found that the inclusion of lattice rotations via the theory of finite strain allows to release certain areas of mechanical fields localization that are related to stereological artifacts
Ernould, Clément. "Développement et application d’une méthode à haute résolution angulaire pour la mesure des gradients d’orientation et des déformations élastiques par microscopie électronique à balayage." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0225.
Повний текст джерелаUnderstanding the deformation mechanisms in crystalline materials requires a fine characterization of microstructures. The precise measurement of lattice rotations and elastic strains in the scanning electron microscope is the aim of the so-called high-angular resolution methods. For this purpose, digital image correlation techniques are used in order to register electron diffraction patterns. In this thesis, an original registration approach is proposed. The displacement field across the whole scintillator is modelled by a linear homography. Such a shape function is often met is the field of computer vision to describe projective transformations. The homography between two patterns is measured from a single and large region of interest using a numerically efficient inverse-compositional Gauss-Newton algorithm. It integrates a correction of optical distortions caused by camera lenses and its convergence is ensured by a pre-alignment step of the patterns. The latter relies on global cross-correlation algorithms based on Fourier-Mellin and Fourier transforms. It fairly accounts for rotations up to approximately ten degrees with an accuracy typically between 0.1 and 0.5°. The homography is measured independently from the projection geometry, which is only considered afterwards to analytically deduce the rotations and elastic strains. The proposed method is validated numerically from simulated and optically distorted patterns showing disorientations up to 14° in the presence of elastic strains up to 5×10⁻². The accurate measurement of elastic strains between 1×10⁻⁴ and 2×10⁻³ requires a correction of radial distortion effects, even when the disorientation angle is small. Finally, the method is applied to patterns acquired by means of electron backscatter diffraction (EBSD) and in transmission using the new on-axis transmission Kikuchi diffraction (TKD) configuration. Plastically deformed polycrystalline metals as well as semiconductors are characterized. The method highlights fine details of the microstructure of a quenched and tempered martensitic steel and of an interstitial free steel deformed by 15% in tension, although plastic deformation deteriorates the diffraction contrast. The deformation structures in a nanostructured aluminium obtained by severe plastic deformation are also analysed by coupling the image registration method to the on-axis TKD configuration. This coupling allows a high spatial resolution (3 to 10 nm) and a high angular resolution (0.01 to 0.05°) to be reached simultaneously. Elastic strain maps are obtained at the nanoscale in a SiGe thin foil. The geometrically necessary dislocation densities in a GaN single crystal are mapped with a resolution of about 2.5×10⁻³ µm⁻¹ (i.e. 8×10¹² m⁻²)
Drui, Florence. "Modélisation et simulation Eulériennes des écoulements diphasiques à phases séparées et dispersées : développement d’une modélisation unifiée et de méthodes numériques adaptées au calcul massivement parallèle." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC033/document.
Повний текст джерелаIn an industrial context, reduced-order two-phase models are used in predictive simulations of the liquid fuel injection in combustion chambers and help designing more efficient and less polluting devices. The combustion quality strongly depends on the atomization process, starting from the separated phase flow at the exit of the nozzle down to the cloud of fuel droplets characterized by a disperse-phase flow. Today, simulating all the physical scales involved in this process requires a major breakthrough in terms of modeling, numerical methods and high performance computing (HPC). These three aspects are addressed in this thesis. First, we are interested in mixture models, derived through Hamilton’s variational principle and the second principle of thermodynamics. We enrich these models, so that they can describe sub-scale pulsations mechanisms. Comparisons with experimental data in a context of bubbly flows enables to assess the models and the methodology. Based on a geometrical study of the interface evolution, new tracks are then proposed for further enriching the mixture models using the same methodology. Second, we propose a numerical strategy based on finite volume methods composed of an operator splitting strategy, approximate Riemann solvers for the resolution of the convective part and specific ODE solvers for the source terms. These methods have been adapted so as to handle several difficulties related to two-phase flows, like the large acoustic impedance ratio, the stiffness of the source terms and low-Mach issues. Moreover, a cell-based Adaptive Mesh Refinement (AMR) strategy is considered. This involves to develop refinement criteria, the setting of the solution values on the new grids and to adapt the standard methods for regular structured grids to non-conforming grids. Finally, the scalability of this AMR tool relies on the p4est AMR library, that shows excellent scalability on several thousands cores. A code named CanoP has been developed and enables to solve fluid dynamics equations on AMR grids. We show that CanoP can be used for future simulations of the liquid atomization
Croissant, Baptiste. "Intensification du procédé de vaporeformage du gaz naturel : fonctionnalisation catalytique d'échangeurs-réacteurs." Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0115.
Повний текст джерелаThe Steam Methane Reforming (SMR) process is still today the most profitable industrial synthesis process of hydrogen. The efficiency of this technique is however facing intrinsically technical limitations due to the design of production units. In order to intensify the global process, exchangers-reactors are under investigation at AIR LIQUIDE. Thanks to recent progresses in metallic additive manufacturing, new compact equipment can be designed. Structures made of millimetric channels allow optimizing heat and mass transfers. New catalyst architecture design needs to be developed to reach high conversion rates despite extreme low contact times in such devices. Stable and highly active rhodium-based catalysts supported on spinel MgAl2O4 have been prepared in this aim. The impact of rhodium loading, properties of supports, as well as thermal treatments have allowed us understanding active phase and support interactions. Catalyst properties under SMR conditions have been linked to active phase morphologies. Functionalization of exchangers-reactors channels through a dip-coating technique has been detailed in this thesis. The formulations of suspensions of washcoat have been optimized thanks to rheological behavior characterizations to achieve very low viscosities. A procedure to deposit homogeneous coatings with controlled thicknesses on the internal channels has been validated on a pilot structure. These new intensified exchangers-reactors have been successfully tested for methane conversion during several hundred of hours
Saied, Mazen. "Etude de la stabilité et de la précision des modèles utilisés dans la correction des effets de proximité optique en photolithographie." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00682907.
Повний текст джерелаMoussa, Hassan. "Contribution to the Decentralized Energy Management of Autonomous AC-Microgrid." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0161/document.
Повний текст джерелаThis thesis deals with islanded AC microgrid that allows any integration of Distributed Energy Resources (DERs) that may provide their existing supply energy in a controlled manner to insure overall system functioning. The interconnection of a DER to a microgrid is done usually by using a Distributed Interface Converter (DIC), a general power electronics interface block, which consists of a source input converter module, a Voltage Source Inverter module (VSI), an output interface module, and the controller module. The thesis realizes several control laws based on decentralized methods. The major focus is on the Droop functions that are responsible for providing a power distribution balance between different Energy Resources connected to a microgrid. The aim is to insure system stability and better dynamic performance when sharing the power between different DGs as function to their nominal power. Developing a closed loop stability analysis is useful for studying system dynamics in order to obtain a desired transient response that allows identifying the proper loop control parameters. Power Quality enhancement in microgrids is also a purpose of this research. The reduction of harmonic distortions of the output voltage when supplying linear and non-linear loads are taken in consideration in this thesis. Further aspects will be studied about how to deal with constant power loads connected to the grid and the large perturbations exerted. This results to further research studies that deal with large-signal stability of microgrids
Zinsmeister, Louis. "Étude de l'évolution hydromécanique d'un carbonate après altération chimique. Application des méthodes de corrélation d'images 2D et 3D à la mesure des champs locaux de déformation lors d'essais mécaniques à différentes échelles." Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00955351.
Повний текст джерелаCortez, Diego. "Amélioration des méthodes pour la détection des éléments intégrés dans les génomes de bactéries et d’archaeaÉtude du système Xer-dif chez les Archaea." Paris 11, 2009. http://www.theses.fr/2009PA112111.
Повний текст джерелаArchaea, the third domain of life, have circular chromosomes and active homologous recombination. Therefore, archaea should harbour a mechanism to solve dimeric chromosomes and overcome this obstacle on their cell cycle. Here we have identified putative dif-like sites in different archaeal chromosomes. The XerA protein is highly active and specific recombining two dif sites. Our results show that the Xer/dif were already present at the base of Bacteria and Archaea, although, we failed to determine whether this is due to an ancient horizontal gene transfer between domains or because the system was already present in LUCA. Archaeal and bacterial genomes contain a number of genes of foreign origin that arose from recent horizontal gene transfer, but the role of integrative elements, such as viruses, plasmids, and transposable elements, in this process has not been extensively quantified. We have performed a large-scale survey of potential recently acquired integrative elements in 119 archaeal and bacterial genomes. Our results strongly indicate that archaeal and bacterial genomes contain an impressive proportion of recently acquired foreign genes (including ORFans) coming from a still largely unexplored reservoir of integrative elements
Hennicker, Julian. "Discrétisation gradient de modèles d’écoulements à dimensions hybrides dans les milieux poreux fracturés." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4057/document.
Повний текст джерелаThis thesis investigates the modelling of Darcy flow through fractured porous media and its discretization on general polyhedral meshes. We follow the approach of hybrid dimensional models, invoking a complex network of planar fractures. The models account for matrix-fracture interactions and fractures acting either as drains or as barriers, i.e. we have to deal with pressure discontinuities at matrix-fracture interfaces. In the case of two phase flow, we present two models, which permit to treat gravity dominated flow as well as discontinuous capillary pressure at the material interfaces. The numerical analysis is performed in the general framework of the Gradient Discretisation Method, which is extended to the models under consideration. Two families of schemes namely the Vertex Approximate Gradient scheme (VAG) and the Hybrid Finite Volume scheme (HFV) are detailed and shown to fit in the gradient scheme framework, which yields, in particular, convergence. For single phase flow, we obtain convergence of order 1 via density results. For two phase flow, the existence of a solution is obtained as a byproduct of the convergence analysis. Several test cases are presented. For single phase flow, we study the convergence on different types of meshes for a family of solutions. For two phase flow, we compare the hybrid-dimensional models to the reference equidimensional model, in which fractures have the same dimension as the matrix. This does not only provide quantitative evidence about computational gain, but also leads to deep insight about the quality of the proposed reduced models