Дисертації з теми "Models of rupture (MOR)"
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Crabbé, Blandine. "Gradient damage models in large deformation." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX085/document.
Повний текст джерелаGradient damage models, also known as phase-field models, are now widely used to model brittle and ductile fracture, from the onset of damage to the propagation of a crack in various materials. Yet, they have been mainly studied in the framework of small deformation, and very few studies aims at proving their relevance in a finite deformation framework. This would be more helpful for the tyre industry that deals with very large deformation problems, and has to gain insight into the prediction of the initiation of damage in its structures.The first part of this work places emphasis on finding analytical solutions to unidimensional problems of damaging viscous materials in small and large deformation.In all the cases, the evolution of damage is studied, both in the homogeneous and localised cases. Having such solutions gives a suitable basis to implement these models and validate the numerical results.A numerical part naturally follows the first one, that details the specificities of the numerical implementation of these non local models in large deformation. In order to solve the displacement and damage problems, the strategy of alternate minimisation (or staggered algorithm) is used. When solved on the reference configuration, the damage problem is the same as in small deformation, and consists in a bound constraint minimisation. The displacement problem is non linear, and a mixed finite element method is used to solve a displacement-pressure problem. A quasi-incompressible Mooney-Rivlin law is used to model the behaviour of the hyperelastic material. Various tests in 2D and 3D are performed to show that gradient damage models are perfectly able to initiate damage in sound, quasi-incompressible structures, in large deformation.In the simulations depicted above, it should be noted that the damage laws combined to the hyperelastic potential results in an initiation of damage that takes place in zones of high deformation, or in other words, in zones of high deviatoric stress. However, in some polymer materials, that are known to be quasi-incompressible, it has been shown that the initiation of damage can take place in zones of high hydrostatic pressure. This is why an important aspect of the work consists in establishing a damage law such that the material be incompressible when there is no damage, and the pressure play a role in the damage criterion. Such a model is exposed in the third part.Finally, the last part focuses on the cavitation phenomenon, that can be understood as the sudden growth of a cavity. We first study it as a purely hyperelastic bifurcation, in order to get the analytical value of the critical elongation for which cavitation occurs, in the case of a compressible isotropic neo-hookean material submitted to a radial displacement. We show that there is a competition between the cavitation phenomenon and the damage, and that depending on the ratio of the critical elongation for damage and the critical elongation for cavitation, different rupture patterns can appear
Pulido, Nelson. "Constraints for Dynamic Models of the Rupture from Kinematic Source Inversion." 京都大学 (Kyoto University), 2000. http://hdl.handle.net/2433/181128.
Повний текст джерелаCirella, Antonella <1977>. "Joint inversion of GPS and strong motion data for earthquake rupture models." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/865/.
Повний текст джерелаHamesse, Charles. "Simultaneous Measurement Imputation and Rehabilitation Outcome Prediction for Achilles Tendon Rupture." Thesis, KTH, Robotik, perception och lärande, RPL, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231485.
Повний текст джерелаAchilles Tendon Rupture (ATR) is one of the typical soft tissue injuries. Rehabilitation after such musculoskeletal injuries remains a prolonged process with a very variable outcome. Being able to predict the rehabilitation outcome accurately is crucial for treatment decision support. In this work, we design a probabilistic model to predict the rehabilitation outcome for ATR using a clinical cohort with numerous missing entries. Our model is trained end-to-end in order to simultaneously predict the missing entries and the rehabilitation outcome. We evaluate our model and compare with multiple baselines, including multi-stage methods. Experimental results demonstrate the superiority of our model over these baseline multi-stage approaches with various data imputation methods for ATR rehabilitation outcome prediction.
Azizipesteh, Baglo Hamid Reza. "Effect of various mix parameters on the true tensile strength of concrete." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12560.
Повний текст джерелаMikami, Naoya. "Source Processes and Dynamic Rupture Models of Three Inland Earthquakes in the Northwestern Chubu District, Central Honshu Japan." 京都大学 (Kyoto University), 1992. http://hdl.handle.net/2433/168831.
Повний текст джерелаKyoto University (京都大学)
0048
新制・論文博士
博士(理学)
乙第7854号
論理博第1177号
新制||理||784(附属図書館)
UT51-92-K354
(主査)教授 尾池 和夫, 教授 安藤 雅孝, 教授 入倉 孝次郎
学位規則第4条第2項該当
Ragon, Théa. "Études des incertitudes dans l’imagerie de la rupture sismique." Thesis, Université Côte d'Azur (ComUE), 2019. http://www.theses.fr/2019AZUR4023.
Повний текст джерелаHow can we study earthquakes, these complex phenomenon occurring so deep under our feet that we cannot observe them directly? One unfortunate aspect of the problem is that we have to rely on measurements acquired at the surface of the Earth. These observations are incomplete, and the imagery of earthquakes is subject to biases induced by numerous approximations. Most of these approximations cannot be avoided, and stem from the poor resolution of the measurements, the inherent lack of knowledge of the physics of the Earth interior, and the bias induced by our modeling procedures. The imperfections of our models question our ability to robustly investigate earthquakes rupture, and thus to understand the physics driving them. The quest for robust images needs a thorough and exhaustive examination of the uncertainties that potentially corrupt the modeling procedure and its results, at least not to interpret improbable characteristics. Although measurement errors are usually accounted for, other kinds of approximations are overlooked. Here, we show that the impact of our simplified description of the Earth’s interior on earthquake models is significant, especially for the events with a large magnitude. We concentrate on two main sources of approximation: the architecture of seismogenic faults, and the temporal complexity of seismic and aseismic processes at play on these faults. We present two methodological developments allowing to estimate and account for uncertainties deriving from these approximations in modeling procedures. In particular, we show that introducing the uncertainties deriving from our approximation of the Earth’s physics is necessary to infer robust and realistic earthquake source models. Our analyses is supported by the use of probabilistic modeling approaches, allowing to explore the diversity and uncertainties of possible models
May, David. "The TLC Method for Modeling Creep Deformation and Rupture." Honors in the Major Thesis, University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1620.
Повний текст джерелаB.S.M.E.
Bachelors
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering
Di, Donfrancesco Fabrizio. "Reduced Order Models for the Navier-Stokes equations for aeroelasticity." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS603.
Повний текст джерелаThe numerical prediction of aeroelastic systems responses becomes unaffordable when parametric analyses with high-fidelity CFD are required. Reduced order modeling (ROM) methods have therefore been developed in view of reducing the costs of the numerical simulations while preserving a high level of accuracy. The present thesis focuses on the family of projection based methods for the compressible Navier-Stokes equations involving deforming meshes in the case of aeroelastic applications. A vector basis obtained by Proper Orthogonal Decomposition (POD) combined to a Galerkin projection of the system equations is used in order to build a ROM for fluid mechanics. Masked projection approaches are therefore implemented and assessed for different test cases with fixed boundaries in order to provide a fully nonlinear formulation for the projection-based ROMs. Then, the ROM is adapted in the case of deforming boundaries and aeroelastic applications in a parametric context. Finally, a Reduced Order Time Spectral Method (ROTSM) is formulated in order to address the stability issues which involve the projection-based ROMs for fluid mechanics applications
Hanada, Raíza Tamae Sarkis. "A noisy-channel based model to recognize words in eye typing systems." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-07112018-105429/.
Повний текст джерелаUm problema importante em sistemas de digitação com os olhos é a correta identificação tanto de quando uma letra é selecionada como de qual letra foi selecionada pelo usuário. As soluções tradicionais para este problema são baseadas na verificação de quanto tempo o olho permanece retido em um alvo. Se ele fica por um certo limite de tempo, a seleção é reconhecida. Métodos em que usam esta ideia são conhecidos como baseados em tempo de retenção (dwell time). É comum que tais métodos, com intuito de melhorar a precisão, adotem tempos de retenção alto. Isso, por outro lado, leva à fadiga e tempos de resposta altos. Estes problemas motivaram a proposta de métodos não baseados em tempos de retenção reduzidos, que dependem de técnicas mais robustas de reconhecimento para inferir as ações dos usuários. Tais estratégias são particularmente mais importantes quando o usuário tem desabilidades que afetam o movimento dos olhos ou usam dispositivos de rastreamento ocular (eye-trackers) muito baratos e, portanto, imprecisos. Uma forma de lidar com o problema de reconhecimento das ações dos usuários é tratá-lo como correção ortográfica. Métodos comuns para correção ortográfica consistem em modelá-lo como a transmissão de uma palavra através de um canal de ruído, tal que é necessário determinar que palavra de um dicionário corresponde à string recebida. Para que a aplicação deste método seja viável, o conjunto de palavras candidatas é reduzido somente àquelas que podem ser transformadas na string de entrada pela aplicação de até k operações de edição de carácter. Esta ideia funciona bem em digitação tradicional porque o número de erros por palavra é pequeno. Contudo, este não é o caso de digitação com os olhos, onde há muito mais ruído. Em tal cenário, técnicas de correção de erros ortográficos não escalam pois seu custo cresce exponencialmente com k e o tamanho do dicionário. Além disso, a distribuição de erros neste cenário é diferente, com muito mais inserções incorretas devido a fontes específicas de ruído como o dispositivo de rastreamento ocular, certos comportamentos dos usuários e características intrínsecas dos movimentos dos olhos. O uso de técnicas probabilísticas baseadas na análise de logs de digitação também não é uma alternativa uma vez que não há corpora de dados grande o suficiente para tanto. Para lidar com todos estes problemas, propomos um método efetivo de reconhecimento que combina estimativas de corpus de erros gerais com conhecimento específico sobre fontes de erro encontradas em sistemas de digitação com os olhos. Nossa técnica é capaz de calcular distâncias de edição eficazmente usando um índice de Mor-Fraenkel em que buscas são feitas com auxílio de um hashing perfeito mínimo. O método possibilita o processamento ordenado de candidatos promissores, de forma que as operações de busca podem ser podadas sem que apresentem perda significativa na qualidade do ranking. Nós também propomos uma heurística linear para estimar distância de edição que tira proveito das informações já mantidas no índice, estendemos nosso modelo de reconhecimento para incluir erros vinculados à variabilidade decorrente dos movimentos oculares e fornecemos um estudo detalhado sobre a importância relativa dos modelos de ruído e de linguagem. Por fim, determinamos os efeitos do modelo no comportamento do usuário enquanto ele digita. Como resultado, obtivemos um método de reconhecimento muito eficaz e rápido o suficiente para ser usado em um sistema real. Em uma tarefa de transcrição com 8 usuários, eles alcançaram velocidade de 17.46 palavras por minuto usando o nosso modelo, o que corresponde a um ganho de 11,3% sobre um método do estado da arte. Nosso método se mostrou mais particularmente útil em situação onde há mais ruído, tal como a primeira sessão de uso. Apesar dos ganhos claros de velocidade de digitação, não encontramos diferenças estatisticamente significativas na percepção dos usuários sobre sua experiência com os dois métodos. Isto indica que uma melhoria no ranking de sugestões pode não ser claramente perceptível pelos usuários mesmo quanto ela afeta positivamente os seus desempenhos.
Mohamed, Ahmed Tohami Abdelhay. "The rupture in state-society relationships and the prominence of youth activism in Egypt : opportunities, strategies and new models of mobilization." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/8502/.
Повний текст джерелаHuang, Xueying. "In Vivo MRI-based three-dimensional fluid-structure interaction models and mechanical image analysis for human carotid atherosclerotic plaques." Worcester, Mass. : Worcester Polytechnic Institute, 2009. http://www.wpi.edu/Pubs/ETD/Available/etd-050409-100213/.
Повний текст джерелаKeywords: atherosclerotic plaque; fluid-structure Interaction models; MRI-based; rupture; plaque vulnerability assessment. Includes bibliographical references (leaves 116-127).
Tanne, Erwan. "Variational phase-field models from brittle to ductile fracture : nucleation and propagation." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX088/document.
Повний текст джерелаPhase-field models, sometimes referred to as gradient damage, are widely used methods for the numerical simulation of crack propagation in brittle materials. Theoretical results and numerical evidences show that they can predict the propagation of a pre-existing crack according to Griffith’s criterion. For a one- dimensional problem, it has been shown that they can predict nucleation upon a critical stress, provided that the regularization parameter is identified with the material’s internal characteristic length.In this work, we draw on numerical simulations to study crack nucleation in commonly encountered geometries for which closed-form solutions are not available. We use U- and V-notches to show that the nucleation load varies smoothly from the one predicted by a strength criterion to the one of a toughness criterion when the strength of the stress concentration or singularity varies. We present validation and verification of numerical simulations for both types of geometries. We consider the problem of an elliptic cavity in an infinite or elongated domain to show that variational phase field models properly account for structural and material size effects.In a second movement, this model is extended to hydraulic fracturing. We present a validation of the model by simulating a single fracture in a large domain subject to a control amount of fluid. Then we study an infinite network of pressurized parallel cracks. Results show that the stimulation of a single fracture is the best energy minimizer compared to multi-fracking case. The last example focuses on fracturing stability regimes using linear elastic fracture mechanics for pressure driven fractures in an experimental geometry used in petroleum industry which replicates a situation encountered downhole with a borehole called burst experiment.The last part of this work focuses on ductile fracture by coupling phase-field models with perfect plasticity. Based on the variational structure of the problem we give a numerical implementation of the coupled model for parallel computing. Simulation results of a mild notch specimens are in agreement with the phenomenology of ductile fracture such that nucleation and propagation commonly reported in the literature
Poloni, Alexandre. "Étude de la sensibilité à la fragilisation par l’hydrogène de deux alliages de titane, le T40 et le TA6V ELI, sous polarisation cathodique en eau de mer par une approche locale de la rupture." Thesis, La Rochelle, 2020. http://www.theses.fr/2020LAROS003.
Повний текст джерелаThis study aims at understanding the hydrogen absorption mechanisms in titanium under cathodic polarization in seawater and then to provide risk assessments for engineers. The single-phase T40 and the two-phase TA6V ELI alloys were employed to study the influence of α and β phases as well as their distribution on the hydrogen embrittlement mechanisms. Hydrogen absorption kinetics were studied for several cathodic potentials in artificial seawater, while other electrolytes were used to validate some hypothesis. These kinetics are observed to be similar between the two alloys despite the differences in the absorption mechanisms and the hydrogen concentration at saturation. Then, this work investigates the role of the metallographic structure on the localisation of hydrides. The evolutions of the mechanical properties were studied by tensile tests on various orientations of solicitation, hydrogen concentrations and notches. As a result, these properties are observed to depend on the hydrogen concentration and the hydrides location. Models by finite elements were also used to determine local mechanical criterions of internal damage and fracture in term of hydrostatic stress and equivalent plastic strain. It allowed us to establish an abacus linking the evolutions of the mechanical properties to the hydrogen concentration. Moreover, this work also results in the determination of a maximum threshold of the cathodic potential at -1,1 V/SCE by comparing the laboratory results with those of on-site galvanic coupling by sacrificial anodes in natural seawater
Antoinat, Léonard. "Contribution à la caractérisation de la déformation et de la rupture dynamique de structures sous impact : Modélisations et approche expérimentale." Thesis, Paris, ENSAM, 2014. http://www.theses.fr/2014ENAM0037/document.
Повний текст джерелаThe objective of this work is to propose approaches to model and to assess experimentally the structural impact on different media. A variety of analytic models and numerical simulations are developed comparing to experimental results. The first part of this work presents a discussion on the similitude between a water impact and an impact on a deformable solid structure. Water impact simulations of a deformable cylinder (without rupture) are performed by finite elements (FE, Coupled Eulerian Lagrangian) and SPH analysis. An analytical model of water impact is proposed for the prediction of peak force evolution. The analysis of results permits to design an impact programmer reproducing this peak force. FE longitudinal impact simulations on cylindrical tubes, with an adapted geometry, are performed and compared with some experiments. The “dynamic buckling” of tubes under impact (due to the material inelastic behavior and to strain waves) is observed. The second part deals with the low velocity perforation (< 10 m/s, strain rate < 1000 s-1) of thin plates. Some experiments on an instrumented drop test (force, displacement, plate shape, crack propagation) are analyzed. Shell FE simulations, with a damage rupture criteria implemented are performed. Parameters are identified by inverse method with the help of Charpy tests made on 2024 T3 aluminum alloy. An analysis of the peak force, during impact, leads to a good understanding of the perforation mechanism. In parallel, a new analytical model, based on an energetic approach of the perforation, is proposed and compared with FE simulations. The numerical perforation study is extended to high velocities and high strain rates (100 - 1000m/s, strain rate < 100 000 s-1) in order to identify different well-known transitions of perforation (Petalisation, petals' fragmentation, total plate's fragmentation)
Renou, Julien. "Observations and modeling of the seismic rupture development based on the analysis of source time functions." Thesis, Université de Paris (2019-....), 2020. https://theses.md.univ-paris-diderot.fr/RENOU_Julien_va2.pdf.
Повний текст джерелаOur knowledge of earthquake source physics, giving rise to events of very different magnitudes, requires observations of a large population of earthquakes. The development of systematic analysis tools for the global seismicity meets these expectations, and allows us to extract the generic properties of earthquakes, which can then be integrated into models of the rupture process. Following this approach, the SCARDEC method is able to retrieve source time func tions of events on a large range of magnitude (Mw > 5.7). The source time function (which describes the temporal evolution of the moment rate) is suitable for the analysis of transient rupture properties which provide insights into the generation of earthquakes of various sizes. The purpose of our study is to observe the rupture development of such earthquakes in order to add better constraints on kinematic and dynamic source models. The first part of our work focuses on the development of earthquakes through the analysis of the SCARDEC catalog. The phase leading to the peak of the source time function (“development phase”) is extracted to characterize its evolution. From the computation of moment accelerations at prescribed mo ment rates, we observe that the evolution of the moment rate during the developement phase is independent of the final magnitude. A quantitative analysis of the moment rate increase as a function of time further indicates that this phase does not respect the steady t 2 self-similar growth, suggesting a transient variation of rupture velocity and/or stress drop. In a second part, these observations are compared with kinematic source models. A crack model with ra dial variations of the rupture velocity combined with low stress drop highlights that correlation between rupture velocity and slip velocity is a key feature for the transient behavior of the development phase previously observed. We then generate, using the composite fractal RIK model, synthetic catalogs of source time functions. This also supports that the correlation bet ween rupture velocity and slip velocity, as well as the duration of the rise-time, have a strong effect on moment acceleration values. We finally develop heterogeneous dynamic models which take into consideration rupture physics. Heterogeneous distributions of the friction parameter Dc and the initial stress τ0 contribute to generate highly realistic rupture scenarios. Rupture propagation is strongly influenced by these two dynamic parameters which induce a clear pre ferential direction of propagation together with a local variability of the rupture velocity. The correlation between rupture velocity and slip velocity highlighted by the previous kinematic models is retrieved and allows to reproduce the SCARDEC observations. These findings are expected to put further constraints on future realistic dynamic rupture scenarios
Mefti, Nacim. "Mise en oeuvre d'un modèle mécanique de l'adhésion cellulaire : approche stochastique." Thesis, Vandoeuvre-les-Nancy, INPL, 2006. http://www.theses.fr/2006INPL099N/document.
Повний текст джерелаCell adhesion is an important phenomenon in biology, especially in the immune defence and tissue growth.We focus in this work on the development of a mechanical model for the description of the cell adhesion in a multiscal context. The first one is microscopic scale, which describes the molecular rupture and adhesion kinetics.At the mesoscopic scale, we model the active deformation of the cell during the motility phenomenon. At the macroscopic scale, we model the time evolution of the adhesion of cell population, under the action of the fluid. Numerical simulations emphasize the rolling phenomenon and the active deformation of a cell
Savio, Daniele. "Nanoscale phenomena in lubrication : From atomistic simulations to their integration into continuous models." Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00961197.
Повний текст джерелаGoda, Ibrahim. "Micromechanical models of network materials presenting internal length scales : applications to trabecular bone under stable and evolutive conditions." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0055/document.
Повний текст джерелаA methodology based on micromechanics has been developed to determine the effective behavior of network materials endowed with a discrete architecture at the microscopic level. It relies on the discrete homogenization method, which has been applied to textile monolayers and trabecular bones. The initially discrete topology of the considered network materials results after homogenization at the mesoscopic level in anisotropic micropolar effective continuum, which proves able to capture the observed internal scale effects. Such micromechanical methods are useful to remedy the difficulty to measure the effective mechanical properties at the intermediate mesoscopic level scale. The bending and torsion responses of vertebral trabecular bone beam specimens are formulated in both static and dynamic situations, based on the Cosserat theory. 3D models have been developed for describing the multiaxial yield and brittle fracture behavior of trabecular bone, including the analysis of size-dependent non-classical plastic yield. We have constructed by FE analyses a homogeneous, orthotropic couple-stress continuum model as a substitute of the 3D periodic heterogeneous cellular solid model of vertebral trabecular bone, based on the equivalent strain energy approach. Bone tissues are able to adapt their local density and load bearing capacities as well as their size and shape to mechanical stimuli. We have developed models for combined internal and external bone remodeling in the framework of the thermodynamics of irreversible processes, at both the cellular and macroscopic levels. We lastly combined anisotropic internal remodeling with fatigue continuum damage
Nguyen, Quoc Lan. "Instabilités liées au frottement des solides élastiques : modélisation de l'initiation des séismes." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10016.
Повний текст джерелаSchwaller, Loïc. "Exact Bayesian Inference in Graphical Models : Tree-structured Network Inference and Segmentation." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS210/document.
Повний текст джерелаIn this dissertation we investigate the problem of network inference. The statistical frame- work tailored to this task is that of graphical models, in which the (in)dependence relation- ships satis ed by a multivariate distribution are represented through a graph. We consider the problem from a Bayesian perspective and focus on a subset of graphs making structure inference possible in an exact and e cient manner, namely spanning trees. Indeed, the integration of a function de ned on spanning trees can be performed with cubic complexity with respect to number of variables under some factorisation assumption on the edges, in spite of the super-exponential cardinality of this set. A careful choice of prior distributions on both graphs and distribution parameters allows to use this result for network inference in tree-structured graphical models, for which we provide a complete and formal framework.We also consider the situation in which observations are organised in a multivariate time- series. We assume that the underlying graph describing the dependence structure of the distribution is a ected by an unknown number of abrupt changes throughout time. Our goal is then to retrieve the number and locations of these change-points, therefore dealing with a segmentation problem. Using spanning trees and assuming that segments are inde- pendent from one another, we show that this can be achieved with polynomial complexity with respect to both the number of variables and the length of the series
Li, Tianyi. "Gradient-damage modeling of dynamic brittle fracture : variational principles and numerical simulations." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX042/document.
Повний текст джерелаIn civil engineering, mechanical integrity of the reinforced concrete structures under severe transient dynamic loading conditions is of paramount importance for safety and calls for an accurate assessment of structural behaviors in presence of dynamic crack propagation. In this work, we focus on the constitutive modeling of concrete regarded as an elastic-damage brittle material. The strain localization evolution is governed by a gradient-damage approach where a scalar field achieves a smeared description of dynamic fracture phenomena. The contribution of the present work is both theoretical and numerical. We propose a variationally consistent formulation of dynamic gradient damage models. A formal definition of several energy release rate concepts in the gradient damage model is given and we show that the dynamic crack tip equation of motion is governed by a generalized Griffith criterion. We then give an efficient numerical implementation of the model based on a standard finite-element spatial discretization and the Newmark time-stepping methods in a parallel computing framework. Simulation results of several problems are discussed both from a computational and physical point of view. Different damage constitutive laws and tension-compression asymmetry formulations are compared with respect to their aptitude to approximate brittle fracture. Specific properties of the dynamic gradient damage model are investigated for different phases of the crack evolution: nucleation, initiation, propagation, arrest, kinking and branching. Comparisons with experimental results are also performed in order to validate the model and indicate its further improvement
Coradi, Audrey. "Modélisation du comportement mécanique des composites a matrice céramique : développement du réseau de fissures." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0267/document.
Повний текст джерелаCeramic matrix composite materials (CMC) are elaborated from fragile constituents. Their mechanical behaviour and crack growing depend on the properties of the CMC elementary constituent. Knowing the influence of these properties on crack development and mechanical behaviour provides support to the composite material designer.This work aims at modelling the crack networks development within the CMC under axial tension, at the yarn scale as well as at the woven composite scale. The proposed approach is an alternative to the main CMC behaviour models.At the yarn scale, matrix cracking with interfacial debonding between fiber and matrix first happen. Both mechanisms are analysed and their development are expressed. The mechanical behaviour resulting from damage and the crack opening displacement are also described using semi-analytical equations. Comparisons with numerical cohesive zone model and also with experimental testing shows good correlation between results.These semi-analytical expressions are then used for modelling damage within each yarns at the woven composite scale. In addition, a numerical tool is developed for matrix cracking and interfacial debonding between yarns of the woven composite
Jung, Sophie. "Agents infectieux et rupture de tolérance lymphocytaire B : étude des processus de maturation d'affinité et de différenciation plasmocytaire au cours d'une infection bactérienne dans un nouveau modèle knock-in autoréactif." Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAJ067.
Повний текст джерелаAutoimmune diseases, affecting more than 5% of the population, reflect a loss of tolerance to selfantigens. These multifactorial diseases result from the combined effect of several susceptibility alleles and different environmental factors. Infectious agents have been particularly incriminated but there is no clear understanding of the underlying mechanisms. B lymphocytes, that appear central to the pathogenesis of several autoimmune diseases, may be activated by several mechanisms during infectious processes and this activation can encompass autoreactive cells. Whether or not the lattercan induce the production of high-affinity pathogenic IgG isotype auto-antibodies from the naturally present low-affinity self-reactive B cells is still unknown. To gain further insight into this question, we created a new intermediate affinity autoreactive mouse model called SWHEL X HEL2X. In these mice, knock-in B cells express a B cell receptor highly specific for Hen-Egg Lysozyme (HEL) that recognizes HEL2X mutated auto-antigen with intermediate affinity. This model, generated on a non-autoimmune-prone genetic background, allows the following of anti-HEL B cells affinity maturation process in presence of their auto-antigen during Borrelia burgdorferi chronic bacterial infection. The infection leads to lymph nodes lymphoproliferation and B cell activation including anergic cells. Some autoreactive clones are able to form germinal centers, toswitch their immunoglobulin heavy chain and to introduce somatic mutations in the heavy chain variable regions on amino-acids forming direct contacts with HEL2X, suggesting an auto-antigen-driven selection process. Despite increased levels of IgM autoantibodies, infected mice are unable to generate IgG autoantibody secreting plasma-cells. These observations suggest the existence of intrinsic peripheral tolerance mechanisms operating mainly at the level of germinal centers. The first checkpoint eliminates switched autoreactive B cells with increasing affinity mutations while a secondcheckpoint avoids IgG+ plasma-cell differentiation. Thus, in genetically non predisposed individuals, tolerance mechanisms may be set-up to prevent the development of pathogenic autoimmunity during the course of an infection
Do, Van Long. "Sequential detection and isolation of cyber-physical attacks on SCADA systems." Thesis, Troyes, 2015. http://www.theses.fr/2015TROY0032/document.
Повний текст джерелаThis PhD thesis is registered in the framework of the project “SCALA” which received financial support through the program ANR-11-SECU-0005. Its ultimate objective involves the on-line monitoring of Supervisory Control And Data Acquisition (SCADA) systems against cyber-physical attacks. The problem is formulated as the sequential detection and isolation of transient signals in stochastic-dynamical systems in the presence of unknown system states and random noises. It is solved by using the analytical redundancy approach consisting of two steps: residual generation and residual evaluation. The residuals are firstly generated by both Kalman filter and parity space approaches. They are then evaluated by using sequential analysis techniques taking into account certain criteria of optimality. However, these classical criteria are not adequate for the surveillance of safety-critical infrastructures. For such applications, it is suggested to minimize the worst-case probability of missed detection subject to acceptable levels on the worst-case probability of false alarm and false isolation. For the detection task, the optimization problem is formulated and solved in both scenarios: exactly and partially known parameters. The sub-optimal tests are obtained and their statistical properties are investigated. Preliminary results for the isolation task are also obtained. The proposed algorithms are applied to the detection and isolation of malicious attacks on a simple SCADA water network
Shen, Yang. "Comportement et endommagement des alliages d’aluminium 6061-T6 : approche micromécanique." Thesis, Paris, ENMP, 2012. http://www.theses.fr/2012ENMP0089/document.
Повний текст джерелаThe AA6061-T6 aluminum alloy was chosen as the material for the core vessel of the future Jules Horowitz testing reactor (JHR). The objective of this thesis is to understand and model the tensile and fracture behavior of the material, as well as the origin of damage anisotropy. A micromechanical approach was used to link the microstructure and mechanical behavior. The microstructure of the alloy was characterized on the surface via Scanning Electron Microscopy and in the 3D volume via synchrotron X-ray tomography and laminography. The damage mechanism was identified by in-situ SEM tensile testing, ex-situ X-ray tomography and in-situ laminography on different levels of triaxiality. The observations have shown that damage nucleated at lower strains on Mg2Si coarse precipitates than on iron rich intermetallics. The identified scenario and the in-situ measurements were then used to develop a coupled GTN damage model incorporating nucleation, growth and coalescence of cavities formed by coarse precipitates. The relationship between the damage and the microstructure anisotropies was explained and simulated
Monfret, Tony. "Utilisation de la composante verticale du mode fondamental des ondes de rayleigh du manteau : etude de la source sismique et modelisation tri-dimensionnelle de la terre." Paris 7, 1988. http://www.theses.fr/1988PA077123.
Повний текст джерелаKaravelić, Emir. "Stochastic Galerkin finite element method in application to identification problems for failure models parameters in heterogeneous materials." Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2501.
Повний текст джерелаThis thesis deals with the localized failure for structures built of heterogeneous composite material, such as concrete, at two different scale. These two scale are latter connected through the stochastic upscaling, where any information obtained at meso-scale are used as prior knowledge at macro-scale. At meso scale, lattice model is used to represent the multi-phase structure of concrete, namely cement and aggregates. The beam element represented by 3D Timoshenko beam embedded with strong discontinuities ensures complete mesh independency of crack propagation. Geometry of aggregate size is taken in agreement with EMPA and Fuller curve while Poisson distribution is used for spatial distribution. Material properties of each phase is obtained with Gaussian distribution which takes into account the Interface Transition Zone (ITZ) through the weakening of concrete. At macro scale multisurface plasticity model is chosen that takes into account both the contribution of a strain hardening with non-associative flow rule as well as a strain softening model components for full set of different 3D failure modes. The plasticity model is represented with Drucker-Prager yield criterion, with similar plastic potential function governing hardening behavior while strain softening behavior is represented with St. Venant criterion. The identification procedure for macro-scale model is perfomed in sequential way. Due to the fact that all ingredients of macro-scale model have physical interpretation we made calibration of material parameters relevant to particular stage. This approach is latter used for model reduction from meso-scale model to macro-scale model where all scales are considered as uncertain and probability computation is performed. When we are modeling homogeneous material each unknown parameter of reduced model is modeled as a random variable while for heterogeneous material, these material parameters are described as random fields. In order to make appropriate discretizations we choose p-method mesh refinement over probability domain and h-method over spatial domain. The forward model outputs are constructed by using Stochastic Galerkin method providing outputs more quickly the the full forward model. The probabilistic procedure of identification is performed with two different methods based on Bayes’s theorem that allows incorporating new observation generated in a particular loading program. The first method Markov Chain Monte Carlo (MCMC) is identified as updating the measure, whereas the second method Polynomial Chaos Kalman Filter (PceKF) is updating the measurable function. The implementation aspects of presented models are given in full detail as well as their validation throughthe numerical examples against the experimental results or against the benchmarks available from literature
Tanays, Eric. "Approche algorithmique des conceptions geometriques et geotechniques de mines a ciel ouvert : application a la mine de carmaux (u.e. tarn, h.b.c.m., cdf)." Paris, ENMP, 1989. http://www.theses.fr/1989ENMP0142.
Повний текст джерелаEl-Hassan, Assoum Nada. "Modélisation théorique et numérique de la localisation de la déformation dans les géomatériaux." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10112.
Повний текст джерелаBarbato, Kelly Biancardini Gomes. "Efeitos do uso de antiinflamatório e do exercício aeróbico sobre a regeneração tecidual e perfil biomecânico do tendão calcâneo de ratos após ruptura completa." Universidade do Estado do Rio de Janeiro, 2011. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=3845.
Повний текст джерелаAchilles tendon rupture is one of the most frequent tendon injuries. Although most studies have shown the benefits of exercise on tendon regeneration, controversy still exists concerning non-steroidal antinflammatory drug (NSAID) effects in this context. Several experimental models have been used for the study of Achilles tendon injury. In this study, we describe the surgical technique of right Achilles tenotomy in rats and subsequently evaluate the effects of NSAID and aerobic exercise, in an isolated fashion and combined, on cell proliferation and biomechanical aspects of the Achilles tendon after tenotomy. Experimental study with 156 male Wistar rats with an average age of 3 months and with average weight of 300g. Surgical procedures were performed under light microscopy, after anesthesia with thiopental. A five millimeters posterior longitudinal incision was created, proximally directed, starting five millimeters proximal to the posterior calcaneal tuberosity. A complete tenotomy of the Achilles tendon was performed, seven millimeters away from the calcaneal tuberosity. The plantaris tendon was preserved. We used Hematoxilin and Eosin, Picrosirius-red and Weigerts Resorcin-fucsin to observe general tendon healing, especially regarding collagen and elastic fibers. After tenotomy, half of the rats received an intramuscular injection of tenoxican for 7 days and exercise was initiated on the 8th day for half the animals of each group. Rats were randomly divided into four treatment groups: A) no NSAID and no exercise; B) NSAID plus exercise; C) no NSAID, with exercise; D) NSAID and no exercise. Animals were sacrificed at 1, 2, 4 and 8 weeks after the tenotomy and cell proliferation was evaluated by immunohistochemistry for PCNA, biomechanical evaluation was performed with ultimate load and gait cycle analysis was also carried out. We used the test of analysis of variance, the Kruskal-Wallis test and also, Bonferroni method, in the R Project program 2.11.1. The mean operative time was one minute and 24 seconds, without complications observed until the 8th postoperative week. Histological studies showed cellular proliferation and fibrilogenesis at two weeks, with decreased amounts of cellularity and elastic fibers at the 8th week, besides changes in structural organization of collagen fibers. The highest intensity of PCNA immunostaining was found at 2 weeks in all groups except for group A (control) that had the highest intensity at 1 week. Animals submitted to exercise had significantly higher (P = 0.02) ultimate loads at 8 weeks after injury. The animals that received NSAID presented with a more stable gait cycle. The surgical technique described for complete Achilles tenotomy, under light microscopy and sparing the plantaris tendon, is simple and quick, shows signs of normal healing process, and it is easily reproducible in rats. Aerobic exercise, initiated early after a complete Achilles tendon tenotomy, was beneficial to the biomechanical aspects of the tendon during regeneration and the combined use of NSAID improved the gaits characteristics, which could be protective against reruptures
Sánchez, Tizapa Sulpicio. "Experimental and numerical study of confined masonry walls under in-plane loads : case : guerrero State (Mexico)." Phd thesis, Université Paris-Est, 2009. http://tel.archives-ouvertes.fr/tel-00537380.
Повний текст джерелаDiaz, Pulgar Luis Gerardo. "Lightning induced voltages in cables of power production centers." Thesis, Limoges, 2016. http://www.theses.fr/2016LIMO0093/document.
Повний текст джерелаWhen lightning strikes a building in a Power Generation Center, dangerous currents propagates through all the components connected to the building structure: The walls, the grounding grid, and the cables leaving the building. It is the interest of this work to study the transient voltages at the terminations of these cables external to the building.Particularly, the Instrumentation and Measure (IM) cables, since they are connected to electronic equipment susceptible of damage or malfunctioning due to lightning ElectroMagnetic perturbations. A full wave approach based on the numerical solution of Maxwell’s equations through the FDTD algorithm is adopted. Notably, the formalism of Holland and Simpson is used to model all the structures composed of thin wires: the building steel structure, the grounding copper grid, the concrete cable ducts and the coaxial IM cables. A validation of the model developed for each component is presented. A sensitivity analysis is performed in order to the determine the main parameters that configure the problem. Also, the Design of Experiments (DoE) technique is used to generate a meta-model that predicts the peak induced voltages in the cable terminations, as a function of the main parameters that configure the industrial site. This represents an accurate, and computationally efficient tool to assess lightning performance of IM cables
Uribe, Suarez Diego Alejandro. "Combinaison d’éléments cohésifs et remaillage pour gérer la propagation arbitraire du chemin de fissure : des matériaux fragiles à l’analyse de fatigue thermique des petits corps du système solaire." Thesis, Université Côte d'Azur, 2021. http://www.theses.fr/2021COAZ4047.
Повний текст джерелаThe present PhD thesis aims at providing a better modeling of fracture phenomenon in brittle materials, with special attention focused on fracture processes taking place in astronomical bodies. One of the most challenging issues in computational fracture mechanics is the propagation of a crack through a finite element mesh for arbitrary crack paths. In this work, this problem is approached by means of an advanced remeshing technique that propagates a crack using cohesive elements through arbitrary directions (mesh-independent). The crack direction is computed using the maximal energy release rate criterion which is implemented using finite elements and the Gθ method. The effects of different numerical and physical parameters regarding the crack path and fracture energy have been investigated. Even though it has been shown that temperature cycles on airless bodies of our Solar System can cause damaging of surface materials (Thermal cracking), propagation mechanisms in the case of space objects are still poorly understood. Thermal cracking of surface rocks, in addition to the impact of micrometeorties, can eventually lead to rocks’ breakup and produce fresh regolith, the latter being the layer of unconsolidated material that covers planetary surfaces. For this reason, the present work combines a thermoelasticity model together with linear elastic fracture mechanics theory to predict fracture propagation in the presence of thermal gradients generated by diurnal temperature cycling and under conditions similar to those existing on asteroid (101955) Bennu. Using the implemented methodologies, it is found that in asteroid Bennu, cracks preferentially propagate in the North to South (N-S), in the North-East to South-West (NE-SW) and in the North-West to South-East (NW-SE) directions. Finally, thermal fatigue analysis was performed in order to estimate the crack growth rate.Aforementioned methodologies have been implemented in Cimlib, a C++ in-house finite element library developed at CEMEF. Inside Cimlib, a methodology allowing two-dimensional crack propagation through arbitrary directions with the option of handling multiple cracks in the domain and inside a parallel environment was developed. Regarding three-dimensional scenario, a first approach where a crack front was propagated through an arbitrary direction was achieved. Concerning numerical modeling of crack propagation, the developed framework opens new possibilities for various applications such as composites cracking at the meso-scale
Rukavina, Ivan. "Cyber-physics intrinsic modelling for smart systems." Thesis, Compiègne, 2021. http://bibliotheque.utc.fr/EXPLOITATION/doc/IFD/2021COMP2581.
Повний текст джерелаIn this thesis, a multi-scale and multi-physics coupling computation procedure for a 2D and 3D setting is presented. When modeling the behavior of a structure by a multi-scale method, the macro-scale is used to describe the homogenized response of the structure, and the micro-scale to describe the details of the behavior on the smaller scale of the material where some inelastic mechanisms, like damage or plasticity, can be taken into account. The micro-scale mesh is defined for each macro-scale element in a way to fit entirely inside it. The two scales are coupled by imposing a constraint on the displacement field over their interface. The computation is performed using the operator split solution procedure on both scales, using the standard finite element method. In a 2D setting, an embedded discontinuity is implemented in the Q4 macroscale element to capture the softening behavior happening on the micro-scale. For the micro-scale element, a constant strain triangle (CST) is used. In a 3D setting, a macro-scale tetrahedral and hexahedral elements are developed, while on the micro-scale Timoshenko beam finite elements are used. This multi-scale methodology is extended with a multi-physics functionality, to simulate the behavior of a piezoelectric material. An additional degree of freedom (voltage) is added on the nodes of the 3D macro-scale tetrahedral and hexahedral elements. For the micro-scale element, a Timoshenko beam element with added polarization switching model is used. Also, a multi-scale Hellinger- Reissner formulation for electrostatics has been developed and implemented for a simple electrostatic patch test. For implementing the proposed procedure, Finite Element Analysis Program (FEAP) is used. To simulate the behavior on both macro and micro-scale, FEAP is modified and two different version of FEAP code are implemented – macroFEAP and microFEAP. For coupling, the two codes are exchanging information between them, and Component Template Library (CTL) is used. The capabilities of the proposed multi-scale approach in a 2D and 3D pure mechanics settings, but also multi-physics environment have been shown. The theoretical formulation and algorithmic implementation are described, and the advantages of the multi-scale approach for modeling heterogeneous materials are shown on several numerical examples
(12804799), Bruce Arthur Jordan. "Duration of load behaviour of an aligned strand wood composite (ASC)." Thesis, 1994. https://figshare.com/articles/thesis/Duration_of_load_behaviour_of_an_aligned_strand_wood_composite_ASC_/20010698.
Повний текст джерелаAn aligned strand, wood composite (ASC) material was subjected to a two year duration of load (DOL) study. The experimental work was conducted in Mt. Gambier South Australia from a purpose built shed housing 42 back to back (double) vertically oriented specimen test rigs in an atmosphere not controlled for temperature and relative humidity. A total of 244 specimens were tested in two population groups, each group divided into two subgroups. One subgroup each for short term static Modulus of Rupture (MOR) and Modulus of Elasticity (MOE), and the other for long term bending strength and stiffness under stresses varying from 0.4MOR to 0.9MOR.
Creep and creep - rupture observations were taken over a two year period providing an extensive database for the evaluation of DOL properties. Monte Carlo simulations were used to give confidence in the process of assigning MOR values to the long term specimens using a statistical matched distribution technique for long term strength evaluation.
Creep and creep - rupture responses for the ASC were similar in effect but fifty percent greater in magnitude than that predicted for solid seasoned timber by AS1720.1-1988, the Australian Timber Structures Code. Creep design multipliers, and long term strength design multipliers in both working stress and limit state design formats were derived for the ASC.
A limiting strain criterion was established for the ASC and was observed to be independent of time under load and applied stress intensity. A failure strain model was presented for the ASC in a form enabling the determination of a limiting deflection for flexural (beam) members at failure.
Sypus, Matthew. "Models of tsunamigenic earthquake rupture along the west coast of North America." Thesis, 2019. http://hdl.handle.net/1828/11436.
Повний текст джерелаGraduate
Wang, Pei-Ling. "Rupture models of the great 1700 Cascadia earthquake based on microfossil paleoseismic observations." Thesis, 2012. http://hdl.handle.net/1828/4167.
Повний текст джерелаGraduate
(13754247), Jenelle Tarlington. "Softwood timber poles: Proving of strength and stiffness." Thesis, 1998. https://figshare.com/articles/thesis/Softwood_timber_poles_Proving_of_strength_and_stiffness/21048196.
Повний текст джерелаThe method of classification of softwood timber poles within Australia is adopted directly from the United States of America, whereby a pole is classified by its groundline circumference which was determined from a given pole tip load and a fibre stress value (as determined from previous testing). Consequently, the derivation of the basis for classification is based on strength and stiffness values determined from the testing of American timber. This study was conducted to determine the strength and stiffness of Queensland plantation grown softwood.
The strength and stiffness of timber is expressed by the Modulus of Rupture (MOR) and Modulus of Elasticity (MOE), respectively.
The samples selected for testing were two lots of 40 specimens of the species Slash Pine (Pinus Elliotti). One sample consisted of poles 9.1m in length, the other 7.6m in length. The species and length of the specimens represent the product of timber poles most commonly utilised by industry. The size of the sample was determined so to be both economic and also to produce results which were a valid indication of the entire population.
Specimens were tested by cantilever loading. Full size poles were placed horizontally into a rigid clamp. A load was then applied to the tip of the pole until failure occurred. The load at failure and corresponding deflection were measured, from which the MOR and MOE of each pole was determined.
Carty, Dillon Matthew. "An Analysis of Boosted Regression Trees to Predict the Strength Properties of Wood Composites." 2011. http://trace.tennessee.edu/utk_gradthes/954.
Повний текст джерелаNaguit, Muriel. "Towards Earthquake-resilient Buildings: Rupture Process & Exposure/Damage Analysis of the 2013 M7.1 Bohol Philippines Earthquake." Phd thesis, 2017. http://hdl.handle.net/1885/117284.
Повний текст джерелаWentzel, Maximilian. "Process optimization of thermal modification of Chilean Eucalyptus nitens plantation wood." Doctoral thesis, 2019. http://hdl.handle.net/11858/00-1735-0000-002E-E5A0-2.
Повний текст джерелаCaston, Megan. "Tsunamigenic potential of crustal faults in the southern Strait of Georgia and Boundary Bay." Thesis, 2021. http://hdl.handle.net/1828/13351.
Повний текст джерелаGraduate