Academic literature on the topic 'Modélisation numérique discrète (DEM)'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Modélisation numérique discrète (DEM).'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Dissertations / Theses on the topic "Modélisation numérique discrète (DEM)":
Nguyen, Minh-Duc. "Modélisation numérique discrète des matériaux bitumeux." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSET003/document.
Bituminous mixtures have traditionally been used in road constructions and recently under railway ballast. Its high rigidity at relatively low ambient temperatures and high frequency explains its widespread application in northern Europe. This material has been studied at the global level by both empirical, experimental and analytical approaches. However, the asphalt has a heterogeneous internal structure and complex which may cause complex behavior. The analysis at the local level then make it possible to supplement the knowledge of its behaviors.Nowadays, the method of discrete elements is known as a numerical tool spread in the granular field. It can model its behavior through local models and provide information about its internal structure. On the one hand, this method considers that the particles are quasi-solid. Its displacement is governed by the laws of motion. On the other hand, the overlap at the particle contact level is allowed. The interpenetration of the particles is calculated by the associated local contact laws. This thesis constitutes a numerical model of bituminous mixes whose isolated particles interact through laws of interaction at a distance. This model takes into account the granulometry of the aggregates (> 1 mm) and its volume ratio with respect to the mastic constituted by grains (<1 mm), the binder and voids. The aggregates (> 1 mm) alone are modeled by numerical particles, while mastic is taken into account by laws of interaction.First, an elastic simulation is performed in order to reproduce the elastic asymptotic behaviors of a reference bituminous mix of GB3 type that appear during extreme conditions (frequency or temperature). Elastic interaction laws have applied to the created numerical model. In both normal and tangential directions, the stiffness of the spring and its ratio are constant.Then, the viscoelastic simulations are performed to reproduce the viscoelastic behavior of the same reference material. At first, a Kelvin-Voigt interaction law is used to qualitatively highlight the application of a viscoelastic law. Then, the global viscoelastic behavior is modeled at the level of the particles by some laws of interaction of type 1KV1R (a Kelvin-Voigt and a spring in series) leaving again to the network of interaction of the numerical model. The stiffness of the springs taking into account the geometry of the particle interface is constant for all models of 1KV1R. However, the viscosities of the dashpots are different. Some hypotheses are examined to distribute its viscosities in the interaction network. At the end of the studies, the analysis of the internal efforts are carried out
Fakih, Mahmoud. "Modélisation numérique discrète de la croissance racinaire dans un sol : relation force-forme." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT323/document.
Plant roots play an important role in the growth and development of plants, and it is well known that the mechanical interactions between a growing root and the surrounding soil can have a major impact on root growth and consequently on plant biomass production. These mechanical interactions are one of numerous factors that explain the variability of root architecture, including genetics, environment and developmental instability. But this factor has often been under-estimated. I hypothesize that the heterogeneous structure of soil at the particle scale, demonstrated by the broad distribution of forces, can significantly influence root growth trajectories. This thesis aims at determining how grains in granular soils are reorganized under the action of growing roots, and in return how the resulting forces acting on root tips modify their development, including the kinematics of their trajectories, in order to develop a general biophysical law of root-soil mechanical interactions. I developed a 2D numerical model of root growth in a granular medium using a Discrete Element Model (DEM). The model is able to compute grain-grain and root-grain contact forces within a granular medium. The root system is modelled using chains of connected spheroline elements. The orientation of root growth at every growth step is determined by the dynamics of the whole root under the action of its internal elastic forces and reaction forces exerted by the grains, which are the mechanical interactions that control numerical growth in the model.Parametric studies were carried out in order to (i) estimate the influence of granular structure (grain diameter distribution, cohesion, volume fraction) and root mechanical properties (root bending stiffness) on the axial force signal acting on the root tip, and on the root trajectories and (ii) define general physical laws that can be used further to analyze experimental data. The distribution curves of computed root tip-grain forces normalized by the mean force during a given period of growth were characterized by a decreasing power law for forces below the mean force, and an exponential fall-off for forces above the mean force, thus reflecting the broad distribution of forces inside the granular material. An analysis of the standard deviation of the local deformations of root trajectories resulted in two different regimes with regard root stiffness. In the first regime, soil controlled the root deformation and in the second, the root trajectory was straighter and displaced more significantly the surrounding grains during growth
Al, 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.
Geotechnical 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
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.
The 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
Than, Vinh-Du. "Comportement en compression des matériaux granulaires humides lâches : expérience et simulation numérique discrète." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1204/document.
An approach combining the Discrete Element Method (DEM) and experimental techniques (oedometric compression test and X-ray Computed Tomography (XRCT)) is proposed to observe the mechanical behavior of wet granular material, modeled as frictional spherical glass beads, in very loose state under growing of applied external force. An experimental observation combining one-dimensional compression test and XRCT is first presented. The plastic responses of real material (spherical glass beads) are depicted with different values of very low initial densities. The grain-scale behavior of this material is then characterized by using the XRCT and in-situ compaction test. We propose a method to detect the spherical structures from the 3D tomography images. Microstructure properties of the loose system are then analyzed and computed from the detected spherical structures. This simplified material gives further a better understanding of the macroscale behavior of wet granular soils based on their microstructure characterization. The DEM simulation then allowed us to predict accurately in 3D the plastic response of very loose assemblies of modeled wet beads to an isotropic/ oedometric compression in the presence of a small amount of an interstitial liquid, which gives rise to capillary menisci and attractive forces. The plastic responses along the compression curves are then shown in particular without and with the appearance of rolling/ pivoting resistances in contacts and also the effect of size polydispersity. The evaluation of microstructure and force transmission along the compression curve is also characterized. Finally, we compare the predictions of the experimental results with the DEM simulations results. Our comparisons show that the predictions of experiments are underestimated for the DEM simulations. Nevertheless, the combined approach in this work also provides an comprehensive characterization of the plastic and grain-scale compression behavior of wet granular soil at very loose state
Dugelas, Loic. "Stratégies probabilistes appliquées à la modélisation numérique discrète : le cas des filets pare-pierres." Thesis, Université Grenoble Alpes, 2020. https://tel.archives-ouvertes.fr/tel-02498238.
This research aims at developing numerical tools to help the design of flexible fences against rockfall.Models based on the Discrete Element Method (DEM) are developed for two flexible fences, using modeling approaches taken from the literature. The main difference between the two flexible fences investigated is their interception structure: ring net or ELITE net. For the ring net flexible fence, the DEM model proved to be a sufficient compromise between relevance, accuracy, and efficiency. On the other side, for the flexible fence with a ELITE net, new numerical developments are necessary to reach such compromise.In order to get an efficient DEM model for the ELITE flexible fence, the sliding between the cables of the net has to be taken into account. Two approaches are proposed to integrate this sliding. In the first approach, the sliding is considered without friction between the cables, while in the second approach the friction is considered. However, the calculation duration obtained with the second approach was too important to integrate it into a complete fence model.The developed models have been integrated into a design assistance tool for flexible fences, based on surrogate modeling. Parametric and sensitivity analysis are carried out with this tool, and the optimal configurations of the fence are identified
Boltcheva, Dobrina. "Modélisation géométrique et topologique des images discrètes." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. https://publication-theses.unistra.fr/public/theses_doctorat/2007/BOLTCHEVA_Dobrina_2007.pdf.
The subject of this thesis is the reconstruction of geometrical meshes from three-dimensional images for visualisation and scientific computation purposes. We introduce a new approach to handle surface reconstruction from 3D discrete data which combines techniques from both, algorithmic geometry and digital topology. The key idea is to join together two concepts: the Delaunay triangulation and the digital surfaces. Our approach allows to reconstruct triangular meshe(s) from discrete data either as a single object for a binary image, or as several objects simultaneously for a multi-labelled segmented image. We introduce two reconstruction methods which use different digital surface definitions: the first method uses a set of voxels as object boundary whereas the second is based on a combinatorial intervoxel boundary
Sakami, Siham. "Modélisation numérique des structures composites multicouches à l’aide d’une approche discrète au sens de Mindlin. Le modèle DDM (Displacement Discrete Mindlin)." Reims, 2008. http://theses.univ-reims.fr/exl-doc/GED00000982.pdf.
The present work of the thesis deals with the theoretical formulation and the evaluation of a new first order finite element for multilayered/sandwich plates and shells. It’s based on a displacement variational model that we consider as discrete, insofar as we introduce kinematic and mechanical hypothesises in a discrete manner. This model, labelled DDM (Discrete Displacement Mindlin), leads to a finite element which is geometrically simple (4 node) and efficient, owing to the linearity of bending curvatures obtained from a quadratic approximation of the normal rotations to the plate mid-surface. The new element takes into account the transverse shear effects along thickness direction and gives thin plate results when the ratio L/h (Length/ thickness) becomes big. It has been successfully validated across some known testing problems, from thin to thick laminated and sandwich
Coulibaly, Jibril. "Modélisation numérique discrète du comportement mécanique sous impact des structures d'écrans de filets pare-pierres." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI040/document.
This thesis introduces a generic model of rockfall barriers under impact loading. The structures are described as an abstract assembly of their main components. The developed model thereby enables the consideration of most of the existing technologies. A C++ code based on the Discrete Element Method is developed in order to perform the numerical simulations of impacts. The generic description of the barriers is implemented at the code level using a corresponding data structure and object-oriented programming. The generic model is completed by the mechanical models of two components. First, a mechanical model of 4-contact interlaced ring nets is developed. An experimental campaign is carried out to calibrate and validate the model against steel wire rings used in rockfall restraining nets. Second, a general sliding cable model is developed to account for the curtain effect. This model demonstrates great capabilities in describing sliding phenomena and a low computational cost. Finally, full-scale impact tests performed on two barriers of different technologies are used to validate the generic model. Numerical simulations of the full-scale tests highlight the relevance of the developed model. Numerical results agree finely with experiments and the model exhibits compelling predictive capacities for engineering applications. Deformations, loading time and forces magnitude are all predicted within 10 % relative error. Complex and unprecedented simulations of repeated impacts are carried out and the model is able to reproduce the barrier behavior both during the impact phase and after springback
Lachihab, Adel. "Un modèle numérique pour les composites biphasés matrice - inclusions rigides : Application à la détermination des propriétés élastiques et en fatigue des enrobés bitumeux." Marne-la-vallée, ENPC, 2004. http://www.theses.fr/2004ENPC0025.
Book chapters on the topic "Modélisation numérique discrète (DEM)":
HUCKERT, Audrey, and Francis TANO. "Les modèles numériques spécifiques au renforcement." In Les géosynthétiques d’hier à aujourd’hui, 85–115. ISTE Group, 2024. http://dx.doi.org/10.51926/iste.8175.ch3.
FELD-PAYET, Sylvia. "Transition endommagement-fissure." In Modélisation numérique en mécanique fortement non linéaire, 309–82. ISTE Group, 2023. http://dx.doi.org/10.51926/iste.9081.ch7.