Dissertations / Theses on the topic 'Multiscale structural analysi'
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LUONI, PIETRO. "MULTISCALE STRUCTURAL ANALYSIS OF ULTRAMAFIC ROCKS IN THE DIFFERENT STRUCTURAL DOMAINS OF THE ALPS, INTEGRATED WITH PETROLOGY AND GEOCHEMISTRY: A KEY TO UNRAVEL THE GEODYNAMIC INTERPRETATION OF COLLISIONAL BELTS." Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/718368.
Full textThe tectono-metamorphic evolution of serpentinites and associated rocks has been investigated in the Alpine ophiolitic Piemontese Zone (PZ) – in the Zermatt-Saas Zone (ZSZ) and near the Sesia-Lanzo Zone (SLZ) rim – and in the Variscan migmatites of the Argentera External Crystalline Massif (ECM). Materials selected for laboratory work contain sequences of meso- and microstructural imprints containing parts of the tectonic evolution of both mono- and poly-orogenic environments (in our case the Piemontese Zone in the Penninic of the Western Alps and the Argentera EMC – Provençal domain of the Alpine collisional front at the Alpine belt termination within the Western Mediterranean). In the Zermatt-Saas Zone serpentinite of Valtournanche, meso- and microstructural analyses have been coupled with petrological investigation, geochemistry, and radiometric dating. In Valtournanche, Créton serpentinite has been interpreted as a slice of mid-ocean ridge lithosphere, affected by gabbroic percolation and hydrothermalism, deeply involved in the Alpine subduction complex, reaching UHP conditions (2.9-3.3 GPa and 600-630 °C) prior to be exhumed at HP conditions 60-70 Ma and incorporated in a mix of slices of oceanic material of heterogeneous origin and metamorphic evolution. Gias Vej serpentinite registered Eclogite facies conditions and was coupled with slices of continental material at the southern border of the Sesia Lanzo Zone before the record of Pmax conditions. At Lake Brocan in Valle Gesso, remnants of serpentinised spinel lherzolite and diopsidite are suggested to represent a most probable vestigial suture zone of the Rheic Ocean in the External Crystalline Massif of Argentera; this relict survived repeated transpositions and dismembering during migmatisation of the deep Variscan crust related to Variscan continental collision. The obtained results indicate that investigation of ultramafic rocks by a structure-driven multidisciplinary approach, can unravel the most complete memory of the divergent and convergent tectonic evolution of old oceans. Similar investigation strategies of laboratory procedures, based on solid structural fieldwork, may more diffusely support circumscription of tectonic units in ocean-derived sequences and contribute to redefine their translational tectonic trajectories during mountain-building processes.
Petracca, Massimo. "Computational multiscale analysis of masonry structures." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/393942.
Full textLa obra de fábrica es un material de construcción tradicional que ha sido utilizado a lo largo de la historia y que sigue siendo utilizado hoy en día. La obra de fábrica constituye la principal técnica de construcción adoptada en estructuras históricas, y una comprensión profunda de su comportamiento es de vital importancia para la conservación de nuestro patrimonio cultural. A pesar de su amplio uso, la obra de fábrica ha sido utilizada frecuentemente adoptando un enfoque empírico, debido a un escaso conocimiento del comportamiento mecánico complejo de este tipo de material compuesto. Los métodos numéricos avanzados son herramientas atractivas para entender y predecir el comportamiento de la obra de fábrica hasta su fallo, permitiendo estimar la resistencia residual y la seguridad de las estructuras. Durante los últimos años, han sido propuestos diferentes modelos computacionales, basados bien en una micro-modelización completa de los constituyentes del material (ladrillos y juntas de mortero), o bien en macro-modelos fenomenológicos. A partir de estos dos enfoques, los métodos de homogenización computacional han emergido recientemente como una herramienta prometedora que puede combinar las ventajas de la micro- y macro-modelización. El problema se divide en dos pasos: la escala estructural se trata como un medio homogéneo equivalente, mientras el comportamiento complejo de la microestructura heterogénea se tiene en cuenta mediante la resolución de un problema micro-mecánico reconducible a una muestra representativa de la microestructura. El objetivo de esta investigación es el desarrollo de una técnica de homogenización computacional multi-escala para el análisis de estructuras de obra de fábrica sometidas a cargas horizontales cuasi-estáticas que actúan en el plano y fuera del plano. Se adopta la teoría clásica del medio continuo de Cauchy en ambas las escalas, utilizando así la homogeneización computacional del primer orden. Debido a la naturaleza frágil de los componentes de la obra de fábrica, el estudio contempla también el problema de la localización de la deformación en el marco del enfoque numérico de fisura distribuida. En este contexto, la presente investigación propone una extensión de la regularización basada en la energía de fractura para el problema de homogenización en dos escalas, permitiendo el uso de la homogenización computacional del primer orden en problemas que implican la localización de la deformación. El método se plantea en primer lugar para el caso continuo general, y a continuación se aplica al análisis de muros de corte cargados en su plano y hechos de fábrica de ladrillos con aparejo periódico. Posteriormente, el método se extiende al caso de estructuras tipo placa para el análisis de muros de obra de fábrica cargados fuera de su plano. Para este propósito, se desarrolla una nueva técnica de homogenización basada en la teoría de placas gruesas. En ambos los casos de carga en el plano y fuera del plano, la precisión del método propuesto se valida mediante la comparación con ensayos experimentales y análisis de micro-modelización. También se validan las propiedades de regularización. Los resultados obtenidos muestran cómo la homogeneización computacional pueda resultar una herramienta válida para una evaluación precisa de la respuesta estructural de las estructuras de obra de fábrica, teniendo en cuenta el comportamiento complejo de la micro-estructura.
La muratura è un antico materiale da costruzione che è stato utilizzato in special modo nel corso della storia, ma che è ancora oggi piuttosto diffuso. La muratura è la tecnica principale di costruzione adottata in edifici storici, e una profonda comprensione del suo comportamento è di vitale importanza per la conservazione del nostro patrimonio culturale. Nonostante il suo ampio utilizzo, la muratura è sempre stata utilizzata seguendo un approccio empirico, a causa di una scarsa comprensione del complesso comportamento meccanico di tale materiale composito. I metodi numerici avanzati sono, quindi, strumenti attraenti per studiare e comprendere il comportamento della muratura fino al suo collasso, permettendo di stimare la resistenza residua e la sicurezza delle strutture. Diversi metodi numerici sono stati proposti negli ultimi anni, basati o sulla completa micro-modellazione dei componenti della muratura (mattoni e giunti di malta), o su macro-modelli fenomenologici. A metà strada tra questi due approcci, le tecniche di omogeneizzazione computazionale sono emerse recentemente come uno strumento promettente che unisce i vantaggi della micro- e macromodellazione. Il problema viene diviso in due scale: la scala strutturale viene trattata come un mezzo omogeneo equivalente, mentre il complesso comportamento della microstruttura eterogenea viene preso in considerazione risolvendo un problema di micro-scala su un volume rappresentativo della microstruttura. Lo scopo di questa ricerca è lo sviluppo di una tecnica di omogeneizzazione computazionale multiscala per l’analisi di strutture in muratura, sottoposte a carichi orizzontali quasi-statici agenti nel piano e fuori dal piano. La teoria classica del continuo di Cauchy è adottata in entrambe le scale, utilizzando quindi la cosiddetta omogeneizzazione computazionale del primo ordine. A causa della natura fragile dei costituenti della muratura, particolare attenzione viene dedicata al problema della local-izzazione delle deformazioni nel modello numerico a danneggiamento distribuito. In questo contesto, la presente ricerca propone un’estensione della regolarizzazione basata sull’energia di frattura al problema di omogeneizzazione a due scale, permettendo l’uso dell’omogeneizzazione computazionale di primo ordine in problemi che coinvolgono localizzazione delle deformazioni. Il metodo viene prima impostato per il caso continuo generale, e viene in seguito applicato all’analisi bidimensionale di pareti a taglio, caricate nel piano, fatte di muratura di mattoni a disposizione periodica. Poi, il suddetto metodo viene esteso al caso di strutture tipo piastra per l’analisi di pareti in muratura caricate fuori dal piano. A questo scopo, si sviluppa una nuova tecnica di omogeneizzazione basata sulla teoria delle piastre spesse. In entrambi i casi di carico nel piano e fuori dal piano, l’accuratezza del metodo proposto è validata mediante il confronto con evidenze sperimentali e con analisi di micro-modellazione. Allo stesso modo, le proprietà di regolarizzazione vengono validate. I risultati ottenuti evidenziano come l’omogeneizzazione computazionale sia uno strumento valido per una valutazione accurata della risposta strutturale delle strutture in muratura, tenendo conto del comportamento complesso della sua microstruttura.
Unnikrishnan, Vinu Unnithan. "Multiscale analysis of nanocomposite and nanofibrous structures." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1469.
Full textKayastha, Shilva. "New methods of multiscale chemical space analysis : visualization of structure-activity relationships and structural pattern extraction." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAF042/document.
Full textThis thesis presents studies devoted to aid in systematic analysis of chemical spaces, focusing on mining and visualization of structure-activity relationships (SARs). It reports some new analysis protocols, combining both existing and on-purpose developed novel methodology to address both large-scale and local SAR analysis. Large-scale analysis featured both generative topographic mapping (GTM)-based extraction of privileged structural motifs and scaffold analysis. GTM was combined with chemical space network (CSN) to develop a visualization tool providing global-local views of SAR in large data sets. We also introduce star coordinates (STC) to visualize multi-property space and prioritize drug-like subspaces. Local SAR monitoring includes new strategies to predict activity cliffs using support vector machine models and a study of structural modifications on ionization state of compounds. The SAR matrix methodology was applied to objectively evaluate SAR progression during lead optimization
Casadei, Filippo. "Multiscale analysis of wave propagation in heterogeneous structures." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44889.
Full textGigliotti, Luigi. "Multiscale analysis of damage-tolerant composite sandwich structures." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/32365.
Full textCRIPPA, CHIARA. "Regional and local scale analysis of very slow rock slope deformations integrating InSAR and morpho-structural data." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2021. http://hdl.handle.net/10281/306309.
Full textSlow rock slope deformations (DSGSDs and large landslides) are widespread, affect entire hillslopes and displace volumes up to billions of cubic meters. They evolve over long time by progressive failure processes, under variable climatic and hydro-mechanical coupling conditions mirrored by a complex creep behaviour. Although characterized by low displacement rates (up to few cm/yr), these slope instabilities damage sensitive structures and host nested sectors potentially undergoing rockslide differentiation and collapse. A robust characterization of the style of activity of slow rock slope deformations is required to predict their interaction with elements at risk and anticipate possible failure, yet a comprehensive methodology to this aim is still lacking. In this perspective, we developed a multi-scale methodology integrating geomorphological mapping, field data and different DInSAR techniques, using an inventory of 208 slow rock slope deformations in Lombardia (Italian Central Alps), for which we performed a geomorphological and morpho-structural mapping on aerial images and DEMs. On the regional scale, we developed an objective workflow for the inventory-scale screening of slow-moving landslides. The approach is based on a refined definition of activity that integrates the displacement rate, kinematics and degree of internal damage for each landslide. Using PS-InSAR and SqueeSAR datasets, we developed an original peak analysis of InSAR displacement rates to characterize the degree of segmentation and heterogeneity of mapped phenomena, highlight the occurrence of sectors with differential activity and derive their characteristic displacement rates. Using 2DInSAR velocity decomposition and machine learning classification, we set up an original automatic approach to characterize the kinematics of each landslides. Then, we sequentially combine PCA and K-medoid cluster analysis to identify groups of landslides characterized by consistent styles of activity, accounting for all the relevant aspects including velocity, kinematics, segmentation, and internal damage. Starting from the results of regional-scale classification, we focused on the Corna Rossa, Mt. Mater and Saline DSGSDs, that are emblematic case studies on which apply DInSAR analysis to investigate typical issues in large landslide studies (spatial segmentation, heterogenous activity, sensitivity to hydrological triggers). We applied a targeted DInSAR technique on multiple temporal baselines to unravel the spatial heterogeneities of complex DSGSDs and through a novel stacking approach on raw long temporal baseline interferograms, we outlined the permanent displacement signals and sectors with differential evolution as well as individual active structures. We then used DInSAR to investigate the possible sensitivity of slow rock slope deformations to hydrological triggers. Comparison between seasonal displacement rates, derived by interferograms with targeted temporal baselines, and time series of precipitation and snowmelt at the Mt. Mater and Saline ridge outlined complex temporally shifted seasonal displacement trends. These trends, more evident for shallower nested sectors, outline dominant controls by prolonged precipitation periods modulated by the effects of snowmelt. This suggests that DSGSDs, often considered insensitive to short-term (pluri-annual) climatic forcing, may respond to hydrological triggering, with key implication in the interpretation of their progressive failure. Our results demonstrated the effectiveness of the proposed multi-scale methodology that exploits DInSAR products and targeted processing to identify, classify and characterize the activity of slow rock slope deformation at different levels of details by including geological data in all the analysis stages. Our approach, readily applicable to different settings and datasets, provides the tools to solve key scientific issues in a geohazard-oriented study of slow rock slope deformations.
Honorio, de Faria Tulio. "Modelling Concrete Behaviour At Early-Age : Multiscale Analysis And Simulation Of A Massive Disposal Structure." Thesis, Cachan, Ecole normale supérieure, 2015. http://www.theses.fr/2015DENS0045/document.
Full textThe accurate prediction of the long and short-term behaviour of concrete structures in the nuclear domain is essential to ensure optimal performances (integrity, containment roperties) during their service life. In the particular case of massive concrete structures, at early age the heat produced by hydration reactions cannot be evacuated fast enough so that high temperatures may be reached and the resulting gradients of temperature might lead to cracking according to the external and internal restraints to which the structures are subjected. The goals of this study are (1) to perform numerical simulations in order to describe and predict the thermo-chemo-mechanical behaviour at early-age of a massive concrete structure devoted to nuclear waste disposal on surface, and (2) to develop and apply upscaling tools to estimate rigorously the key properties of concrete needed in an early-age analysis from the composition of the material. Firstly, a chemo-thermal analysis aims at determining the influence of convection, solar radiation, reradiation and hydration heat on the thermal response of the structure. Practical recommendations regarding concreting temperatures are provided in order to limit the maximum temperature reached within the structure. Then, by means of a mechanical analysis, simplified and more complex (i.e. accounting for coupled creep and damage) modelling strategies are used to assess scenarios involving different boundary conditions defined from the previous chemo-thermal analysis. Secondly, a study accounting for the multiscale character of concrete is performed. A simplified model of cement hydration kinetics is proposed. The evolution of the different phases at the cement paste level can be estimated. Then, analytical and numerical tools to upscale the ageing properties are presented and applied to estimate the mechanical and thermal properties of cementbased materials. Finally, the input data used in the structural analysis are compared with the estimations obtained in the multiscale analysis. To conclude, the entire strategy proposed in this thesis aims at predicting the behaviour of massive concrete structures from the composition of the concrete by means of a sequenced approach: concrete behaviour is estimated using the upscaling tools, providing then the input data to the phenomenological analysis at the structure level
Lutz, Benjamin [Verfasser], and W. [Akademischer Betreuer] Wenzel. "Multiscale Simulation and Analysis of Structured Ribonucleic Acids / Benjamin Lutz. Betreuer: W. Wenzel." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1054397236/34.
Full textRamalho, Geraldo Luis Bezerra. "AnÃlise de imagens por meio da matriz de interdependÃncia e da transformaÃÃo estrutural multiescala." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11079.
Full textA anÃlise de imagens à uma tarefa fundamental em visÃo computacional. Ela influencia o desenvolvimento de algoritmos de processamento digital de imagens e as abordagens de avaliaÃÃo dos resultados produzidos por estes algoritmos. Esta tese introduz uma metodologia para a anÃlise estrutural de imagens baseada no uso combinado de uma transformaÃÃo estrutural multiescala e da extraÃÃo de caracterÃsticas estruturais por meio da matriz de interdependÃncia espacial. A transformaÃÃo estrutural multiescala à um algoritmo baseado no arcabouÃo da morfologia matemÃtica que mapeia os nÃveis de cinza da imagem de entrada para um espaÃo no qual esses nÃveis de cinza estÃo reagrupados em diferentes escalas de estruturas que formam os objetos. A transformaÃÃo pode ser aplicada no realce de imagens em nÃveis de cinza e na decomposiÃÃo de imagens binÃrias em estruturas elementares. A matriz de interdependÃncia espacial à um algoritmo baseado na estatÃstica de coocorrÃncia que produz uma representaÃÃo global das coincidÃncias das estruturas de duas imagens de entrada. Essa matriz provà quatro atributos, a saber, correlaÃÃo, momento de diferenÃa inverso, coeficiente chi-quadrado e entropia, os quais podem ser utilizados como descritores globais das estruturas da imagem. A metodologia proposta à validada com os resultados obtidos para diferentes aplicaÃÃes: a deteÃÃo de corrosÃo atmosfÃrica em fotografias de superfÃcies metÃlicas, a deteÃÃo de doenÃas pulmonares em imagens de tomografia computadorizada, a avaliaÃÃo referenciada da qualidade da imagens, a segmentaÃÃo dos vasos da retina em retinografias e a avaliaÃÃo da qualidade de algoritmos de segmentaÃÃo de vasos de retina.
Image analysis is a fundamental task in computer vision. It influences the development of algorithms for digital image processing and approaches for evaluating the results produced by these algorithms. This thesis introduces a methodology for the structural analysis of images based on the combined use of a multiscale structural transformation and extraction of structural features through spatial interdependence matrix. The multiscale structural transformation is an algorithm based on mathematical morphology framework that maps the gray levels of the input image into a space in which these gray levels are grouped into different scales of structures that form objects. The transformation can be applied in enhancement of gray level images and decomposition of binary images into elementary structures. The spatial interdependence matrix is an algorithm based on cooccurrence statistics that produces a global representation of the structural coincidences of two images. This matrix provides four attributes, namely, correlation, inverse difference moment, chi-square coefficient and entropy, which can be used as global descriptors of the image structures. The proposed methodology is validated with the results obtained for different applications: the detection of atmospheric corrosion of metal surfaces in photographs, the detection of lung disease in computerized tomography images, the referenced evaluation of image quality, the segmentation of retinal vessels in retinography and the quality assessment of retinal vessels segmentation algorithms.
El, Helou Rafic Gerges. "Multiscale Computational Framework for Analysis and Design of Ultra-High Performance Concrete Structural Components and Systems." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73381.
Full textPh. D.
Badillo, Almaraz Hiram. "Numerical modelling based on the multiscale homogenization theory. Application in composite materials and structures." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/83924.
Full textEn esta tesis se propone y desarrolla un método de homogeneización multi-dominio basado en una técnica en dos escalas. El método es capaz de analizar estructuras de materiales compuestos con varias distribuciones periódicas dentro de un mismo continuo mediante la partición de todo el dominio del material compuesto en subestructuras utilizando la teoría clásica de homogeneización a través de una formulación estándar de mecánica de medios continuos de primer orden. La necesidad de desarrollar este método multi-dominio surgió porque los métodos actuales de homogeneización se basan en el supuesto de que todo el dominio del material está representado por solo una distribución periódica o cuasi-periódica. Sin embargo, en algunos casos, la estructura puede estar formada por más de un tipo de distribución de dominio periódico. Los principios teóricos desarrollados en el método de homogeneización multi-dominio se aplicaron para ensamblar una herramienta computacional basada en dos problemas de valores de contorno anidados, los cuales son representados por un código de elementos finitos (FE) en dos escalas: a) una escala global, que trata el material compuesto como un material homogéneo. Esta escala se ocupa de las condiciones de contorno, las cargas aplicadas y los diferentes subdominios periódicos (o cuasi-periódicos) que puedan existir en el material compuesto; y b) una escala local, que obtiene la respuesta homogenizada de un volumen representativo o celda unitaria. Esta escala se ocupa de la geometría, y de la distribución espacial de los constituyentes del compuesto así como de sus propiedades constitutivas. El método se basa en la hipótesis de periodicidad local derivada de la periodicidad de la estructura interna del material. La implementación numérica de las restricciones de los desplazamientos y las fuerzas derivadas de la periodicidad se realizaron por medio del método de multiplicadores de Lagrange. La formulación incluye un método para calcular el tensor constitutivo tangente no-lineal homogeneizado una vez que el umbral de la no-linealidad de cualquiera de las celdas unitarias ha sido superado. El procedimiento se basa en llevar a cabo una derivación numérica aplicando una técnica de perturbación. El tensor constitutivo tangente se calcula para cada incremento de carga y para cada iteración del análisis una vez que la estructura ha entrado en el rango no-lineal. El método de perturbación se aplicó tanto en la escala global como en la local con el fin de analizar la efectividad del método en ambas escalas. Se lleva a cabo un proceso de paralelización en el método con el fin de acelerar el proceso de cómputo debido al enorme coste computacional que requiere la solución iterativa incremental anidada. Se investiga el efecto de ablandamiento por deformación en el material usando el método de homogeneización en dos escalas a través de un enfoque de fractura discreta. Se estudió la objetividad en el mallado dentro de la formulación clásica de FE en una escala y luego los conceptos expuestos se extrapolaron en el marco de la homogeneización de dos escalas. Se enfatiza la importancia de la longitud característica del elemento en un análisis multi-escala en el cálculo de la energía específica disipada cuando se produce el efecto de ablandamiento. Se presentan varios ejemplos para evaluar la propuesta computacional desarrollada en esta investigación. Se estudiaron diferentes configuraciones de compuestos que incluyen diferentes tipos de materiales, así como compuestos que presentan ablandamiento después de que el punto de fluencia del material se alcanza (usando daño y plasticidad) y compuestos con zonas que presentan altos gradientes de deformación. Los ejemplos se llevaron a cabo en materiales compuestos con uno y con varios dominios periódicos utilizando diferentes configuraciones de células unitarias. Los ejemplos se comparan con soluciones de referencia obtenidas con el método clásico de elementos finitos en una escala.
Badillo, Almaraz Hiram. "Numerial modelling based on the multiscale homogenization theory. Application in composite materials and structures." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/83924.
Full textEn esta tesis se propone y desarrolla un método de homogeneización multi-dominio basado en una técnica en dos escalas. El método es capaz de analizar estructuras de materiales compuestos con varias distribuciones periódicas dentro de un mismo continuo mediante la partición de todo el dominio del material compuesto en subestructuras utilizando la teoría clásica de homogeneización a través de una formulación estándar de mecánica de medios continuos de primer orden. La necesidad de desarrollar este método multi-dominio surgió porque los métodos actuales de homogeneización se basan en el supuesto de que todo el dominio del material está representado por solo una distribución periódica o cuasi-periódica. Sin embargo, en algunos casos, la estructura puede estar formada por más de un tipo de distribución de dominio periódico. Los principios teóricos desarrollados en el método de homogeneización multi-dominio se aplicaron para ensamblar una herramienta computacional basada en dos problemas de valores de contorno anidados, los cuales son representados por un código de elementos finitos (FE) en dos escalas: a) una escala global, que trata el material compuesto como un material homogéneo. Esta escala se ocupa de las condiciones de contorno, las cargas aplicadas y los diferentes subdominios periódicos (o cuasi-periódicos) que puedan existir en el material compuesto; y b) una escala local, que obtiene la respuesta homogenizada de un volumen representativo o celda unitaria. Esta escala se ocupa de la geometría, y de la distribución espacial de los constituyentes del compuesto así como de sus propiedades constitutivas. El método se basa en la hipótesis de periodicidad local derivada de la periodicidad de la estructura interna del material. La implementación numérica de las restricciones de los desplazamientos y las fuerzas derivadas de la periodicidad se realizaron por medio del método de multiplicadores de Lagrange. La formulación incluye un método para calcular el tensor constitutivo tangente no-lineal homogeneizado una vez que el umbral de la no-linealidad de cualquiera de las celdas unitarias ha sido superado. El procedimiento se basa en llevar a cabo una derivación numérica aplicando una técnica de perturbación. El tensor constitutivo tangente se calcula para cada incremento de carga y para cada iteración del análisis una vez que la estructura ha entrado en el rango no-lineal. El método de perturbación se aplicó tanto en la escala global como en la local con el fin de analizar la efectividad del método en ambas escalas. Se lleva a cabo un proceso de paralelización en el método con el fin de acelerar el proceso de cómputo debido al enorme coste computacional que requiere la solución iterativa incremental anidada. Se investiga el efecto de ablandamiento por deformación en el material usando el método de homogeneización en dos escalas a través de un enfoque de fractura discreta. Se estudió la objetividad en el mallado dentro de la formulación clásica de FE en una escala y luego los conceptos expuestos se extrapolaron en el marco de la homogeneización de dos escalas. Se enfatiza la importancia de la longitud característica del elemento en un análisis multi-escala en el cálculo de la energía específica disipada cuando se produce el efecto de ablandamiento. Se presentan varios ejemplos para evaluar la propuesta computacional desarrollada en esta investigación. Se estudiaron diferentes configuraciones de compuestos que incluyen diferentes tipos de materiales, así como compuestos que presentan ablandamiento después de que el punto de fluencia del material se alcanza (usando daño y plasticidad) y compuestos con zonas que presentan altos gradientes de deformación. Los ejemplos se llevaron a cabo en materiales compuestos con uno y con varios dominios periódicos utilizando diferentes configuraciones de células unitarias. Los ejemplos se comparan con soluciones de referencia obtenidas con el método clásico de elementos finitos en una escala.
Chabani, Arezki. "Analyse méthodologique et caractérisation multi-échelle des systèmes de fractures à l’interface socle/couverture sédimentaire – application à la géothermie (bassin de Valence, SE France)." Electronic Thesis or Diss., Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM046.
Full textThe Valence basin is a graben located in the Rhodanian corridor which belongs to the ECRIS system, and is the subject of many studies due to its geothermal potential. In response to its a multiphase history, fracture networks of the basement and sedimentary cover which are targeted for geothermal exploitation show a complex organization. This study aims to characterize facture networks organization in the Valence basin. It is based on seismic and borehole data in the basin, as well as geological maps, digital elevation model (DEM) and outcrops on the Ardèche margin. Two methodological studies were developed to characterize the orientation and length distributions. These methods allowed to determine fracture network modelling parameters, and highlighted a structural heritage but also a detachment between the basement and the cover
Xia, Liang. "Towards optimal design of multiscale nonlinear structures : reduced-order modeling approaches." Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2230/document.
Full textHigh-performance heterogeneous materials have been increasingly used nowadays for their advantageous overall characteristics resulting in superior structural mechanical performance. The pronounced heterogeneities of materials have significant impact on the structural behavior that one needs to account for both material microscopic heterogeneities and constituent behaviors to achieve reliable structural designs. Meanwhile, the fast progress of material science and the latest development of 3D printing techniques make it possible to generate more innovative, lightweight, and structurally efficient designs through controlling the composition and the microstructure of material at the microscopic scale. In this thesis, we have made first attempts towards topology optimization design of multiscale nonlinear structures, including design of highly heterogeneous structures, material microstructural design, and simultaneous design of structure and materials. We have primarily developed a multiscale design framework, constituted of two key ingredients : multiscale modeling for structural performance simulation and topology optimization forstructural design. With regard to the first ingredient, we employ the first-order computational homogenization method FE2 to bridge structural and material scales. With regard to the second ingredient, we apply the method Bi-directional Evolutionary Structural Optimization (BESO) to perform topology optimization. In contrast to the conventional nonlinear design of homogeneous structures, this design framework provides an automatic design tool for nonlinear highly heterogeneous structures of which the underlying material model is governed directly by the realistic microstructural geometry and the microscopic constitutive laws. Note that the FE2 method is extremely expensive in terms of computing time and storage requirement. The dilemma of heavy computational burden is even more pronounced when it comes to topology optimization : not only is it required to solve the time-consuming multiscale problem once, but for many different realizations of the structural topology. Meanwhile we note that the optimization process requires multiple design loops involving similar or even repeated computations at the microscopic scale. For these reasons, we introduce to the design framework a third ingredient : reduced-order modeling (ROM). We develop an adaptive surrogate model using snapshot Proper Orthogonal Decomposition (POD) and Diffuse Approximation to substitute the microscopic solutions. The surrogate model is initially built by the first design iteration and updated adaptively in the subsequent design iterations. This surrogate model has shown promising performance in terms of reducing computing cost and modeling accuracy when applied to the design framework for nonlinear elastic cases. As for more severe material nonlinearity, we employ directly an established method potential based Reduced Basis Model Order Reduction (pRBMOR). The key idea of pRBMOR is to approximate the internal variables of the dissipative material by a precomputed reduced basis computed from snapshot POD. To drastically accelerate the computing procedure, pRBMOR has been implemented by parallelization on modern Graphics Processing Units (GPUs). The implementation of pRBMOR with GPU acceleration enables us to realize the design of multiscale elastoviscoplastic structures using the previously developed design framework inrealistic computing time and with affordable memory requirement. We have so far assumed a fixed material microstructure at the microscopic scale. The remaining part of the thesis is dedicated to simultaneous design of both macroscopic structure and microscopic materials. By the previously established multiscale design framework, we have topology variables and volume constraints defined at both scales
Zhu, Shaoming. "Multiscale analysis of protein functions and stochastic modelling of gene transcriptional regulatory networks." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/41693/1/Shaoming_Zhu_Thesis.pdf.
Full textAvois-Jacquet, Carol. "Variabilité spatiale multiéchelle du zooplancton dans un lagoon récifal côtier (Multiscale spatial variability of zooplankton in a coastal reef lagoon)." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2002. http://tel.archives-ouvertes.fr/tel-00001767.
Full textRoirand, Quentin. "Modélisation multiéchelle du comportement et de l'endommagement de composites tissés 3D. Développement d'outils numériques d'aide à la conception des structures tissées." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM036/document.
Full textWith their large flexibility of design , 3D woven composites can provide mechanical properties tailored specificially to structural needs. However, the architectural complexity of woven reinforcements presents serious challenges when predicting properties, behaviours and damage processes. The present work deals with these challenges and seeks to develop numerical tools which are able to foresee the mechanical characteristics of this kind of materials. For this purpose, a multiscale approach, which combines experimental tests and numerical simulations, has been adopted. This approach allows, simultaneously, to take into account the loads and composite behavior, at the macroscopic scale, also the reinforcement geometry and the material heterogeneities which are only visible at the mesoscopic scale. The experimental investigation has been carried out to characterize the behaviour of an 2.5D interlock composite and its constituents. Examinations of the damage mechanisms have also been performed, using tomography and the interzone concept, for this woven composite under loadings in tension and combined tension and bending. With regards to the numerical modeling part, the ultimate degradation of the composite was simulated by cutting the reinforcement yarns with a failure criterion, previously reported, on a 3D representative cell of the experimental composite. For the two kinds of macroscopic loadings, the locations, orientations and kinetics of the damage were found to be fully in agreement with the experimental results. The influence of the architectural parameters on the failure criterion was then evaluated by finite element calculation. Consequently, it has been possible to proposed optimized architectures and make a camparison, for the two macroscopic loadings, with the 2.5D interlock woven composite. Still motivated to improve the prediction of the behaviour of woven composites, this work has also been on developing a finer modeling approach to the understanding of damage mechanisms. A stochastic approach was therefore introduced to the failure criterion using a Weibull statistical distribution. In addition, matrix cavitation has also been taken into account in the modelling. This damage mechanism was simulated using the GTN (Gurson-Tvergaard-Needleman) model. Finally, model reduction techniques have been applied to lower the cost of computing multiscale modeling in order to identify, for example, material properties by an inverse method or to simulate fatigue tests
Aghaei, Amin. "Symmetry-Adapted Molecular Modeling of Nanostructures and Biomembranes." Research Showcase @ CMU, 2013. http://repository.cmu.edu/dissertations/295.
Full textThiede, Tobias [Verfasser], Giovanni [Akademischer Betreuer] Bruno, Giovanni [Gutachter] Bruno, Christoph [Gutachter] Genzel, and Simone [Gutachter] Carmignato. "A multiscale analysis of additively manufactured lattice structures / Tobias Thiede ; Gutachter: Giovanni Bruno, Christoph Genzel, Simone Carmignato ; Betreuer: Giovanni Bruno." Potsdam : Universität Potsdam, 2019. http://d-nb.info/1219515442/34.
Full textSalles, Loïc. "Etude de l'usure par fretting sous chargements dynamiques dans les interfaces frottantes : application aux pieds d'aubes de turbomachines." Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00600613.
Full textTruan, Melanie Allen. "Spatiotemporal, multiscale gradient analysis of longitudinal community structure and habitat relationships for plants, birds, and small mammals in two shredded riparian ecosystems, Central Valley, California /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
Full textMarty, Jérémy. "Analyse expérimentale des cinématiques de changement d'échelles en mécanique non linéaire." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0013/document.
Full textIndustry employ more and more composite materials in structures todecrease the weight. At the microstructure scale behavior is strongly heterogeneous but at the structure scale behaviour may be considered homogeneous. Multiscale methods have been developed to solve the structural problems with a reasonable calculation time. These methods are validated by comparison with a numerical calculation where heterogeneities are fully meshed. In this thesis work, an ideal architectural material was created in the center of a (homogeneous) stainless steel (304L) thin plate. The unit cell architecture material consists of a square with a hole in the center. The use of a high resolution camera (270 million pixels) allows to follow simultaneously the evolution of deformation at microscopic and macroscopic scales. The orientation of the heterogeneous structure modifies the sollicitations applied to the unit cells. The experiments are designed to analyze the kinematics of deformation of the unit cells in a multi-axial loading. Unit cells with periodic kinematics are searched. It is thus shown that the cells with a non-periodic kinematic correspond to the transition zone between the homogeneous material and the architectured material. Knowledge of the kinematic cells allows to investigate the scale changings in the linear and nonlinear range. The downscaling from the macroscopic to the microscopic scale is particularly studied with the choice of boundary conditions. An equivalent homogeneous medium (MHE) is determined as a remplacement for the cells having a periodic kinematic. The geometry of the unit cell introduced symmetries in the behavior of MHE, it becomes cubic (orthotropic with material parameters). The elastic characteristics of the MHE are obtained by homogenization from the experimental results. A criterion of Tsai-Hill is identified in the non-linear domain. The last chapter is interested in cracking of the architected zone and the initiation of strain localization in cells. The support of location is calculated from the strain field measured by correlation. The kinematics of the cell is enriched with a discontinuity and the displacement jump normal to the localization is identified. A comparison with the displacement jump calculated by extended digital image correlation at the macroscopic scale is conducted to validate the identification strategy at the microscopic level
Suzuki, Yoshiharu. "Integrated approach on the multiscale structure of precipitation-topography relationship over mountainous complex terrain based on weather radar observations and numerical model analysis of the atmosphere." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136352.
Full textSecco, Michele. "Characterization studies on cement conglomerates from historic reinforced concrete structures." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422111.
Full textBrevettato da Joseph Monier nel 1867, il conglomerato cementizio armato (comunemente definito calcestruzzo armato, o cemento armato) è diventato un materiale da costruzione di grandissimo successo nel corso del XX secolo, capace di soddisfare le richieste più impegnative di progettisti e ingegneri. Tuttavia, nonostante la sua introduzione e diffusione abbia spianato la strada a un secolo di continue innovazioni tecnologiche nell'ambito dell'industria delle costruzioni, il comportamento meccanico degli edifici costruiti con tale materiale non è stato compreso a pieno per lungo tempo, con conseguente incidenza di una serie di problemi strutturali interessanti gli edifici costruiti nei primi decenni del XX secolo. Alle radici del problema non vi era soltanto la concezione empirica dei calcoli strutturali, ma anche la mancanza di una tecnologia standardizzata di produzione del calcestruzzo e la scarsa attenzione posta nella scelta delle materie prime e delle strategie di miscelazione. Inoltre, le problematiche relative alla resistenza del conglomerato cementizio armato all'azione degradante di agenti chimico-fisici esterni non sono state considerate per gran parte del XX secolo, a causa dell'errata assunzione di "durabilità infinita" del materiale. Un secolo e mezzo dopo la sua invenzione, il cemento armato è al giorno d'oggi considerato un materiale di interesse culturale, costituendo il nucleo strutturale dell'architettura contemporanea. La caratterizzazione di questo materiale eterogeneo è stata per decenni di competenza esclusiva degli ingegneri strutturali, ma, nel corso degli ultimi quindici anni, è diventata una delle principali tematiche di studio degli scienziati dei materiali, a causa della complessità mineralogica, tessiturale e chimica del calcestruzzo e della sua suscettibilità all'azione di agenti alterativi esterni di natura chimico-fisica. Considerata la complessità del materiale, un approccio analitico combinato e multidisciplinare, comprendente campi sia ingegneristici sia della scienza dei materiali, risulta necessario al fine di ottenere una completa caratterizzazione meccanica e microstrutturale delle strutture in cemento armato e, conseguentemente, di progettare ed eseguire interventi di restauro con materiali adeguati per la riabilitazione e il miglioramento strutturale di questi moderni beni culturali. Tale progetto di ricerca è stato volto alla caratterizzazione multi-analitica di conglomerati cementizi appartenenti a cinque edifici storici in cemento armato, tutti localizzati nell’Italia nordorientale e costruiti tra la fine del XIX secolo e la metà del XX secolo, prestando particolare attenzione alla determinazione dei mix design originari, allo studio del loro stato di conservazione e allo sviluppo di tecniche analitiche innovative di natura mediamente distruttiva. I materiali sono stati anzitutto caratterizzati tramite un approccio multi-analitico; in questa parte dello studio, la classica caratterizzazione petrografica dei conglomerati secondo le linee guida dello standard americano ASTM C856 è stata integrata con i risultati ottenuti tramite analisi mineralogiche in diffrazione ai raggi X delle polveri (XRPD) e analisi microstrutturali e microchimiche in microscopia elettronica a scansione e microfluorescenza ai raggi X a dispersione di energia (SEM-EDS). La metodologia analitica integrata ha permesso un notevole allargamento dello spettro dei risultati ottenuti, consentendo una caratterizzazione completa dei materiali e dei loro costituenti in un ampio intervallo dimensionale, composizionale e tessiturale. I risultati ottenuti, sebbene altamente accurati, sono strettamente qualitativi, in particolare per quanto concerne la determinazione di una serie di parametri fondamentali per la ricostruzione dei mix design originari (quali i rapporti acqua/cemento e cemento/aggregato e la curva di distribuzione granulometrica degli inerti). A tal riguardo, diversi studi hanno recentemente testato procedure di analisi di immagine 2D per lo studio di componenti del calcestruzzo indurito, ottenendo risultati affidabili e oggettivi. Ciononostante, tali procedure analitiche non sono mai state applicate al sistema calcestruzzo nel suo insieme, a causa di limitazioni intrinseche delle tecniche di studio legate sia all'alto grado di polidispersione delle componenti del conglomerato cementizio, sia all'assenza di chiari traccianti colorimetrici in grado di consentire una rapida e chiara discriminazione digitale delle stesse. Al di là di tali problematiche, allo stato dell'arte l'analisi di immagine 2D risulta essere l'unica tecnica analitica in grado, almeno in via teorica, di fornire risultati rapidi, attendibili e oggettivi su un materiale caratterizzato da un grado di polidispersione così elevato. Conseguentemente, uno degli obbiettivi principali di questo progetto di ricerca è consistito nello sviluppo di un valido protocollo multiscala di preparazione dei campioni e acquisizione e analisi delle immagini per ricostruire completamente e quantitativamente i mix design dei calcestruzzi storici studiati. Tale approccio analitico innovativo si è dimostrato estremamente affidabile per l'ottenimento di una caratterizzazione completa di questi materiali eterogenei e poco standardizzati, e i risultati ottenuti sono stati confrontati con successo con quelli ottenuti tramite lo studio multi-analitico. Infine, è stato effettuato uno studio dettagliato dello stato di conservazione e dei fenomeni di degrado agenti sui materiali. I calcestruzzi sono stati studiati con un approccio multi-analitico articolato in uno studio petrografico preliminare, integrato da analisi XRPD di profilo della frazione fine dei materiali e da analisi SEM-EDS sia su campioni massivi che in sezione sottile. I risultati hanno evidenziato l'incidenza nei materiali di molteplici fenomeni di alterazione, strettamente correlati alle loro caratteristiche composizionali e tessiturali e alle condizioni ambientali di esposizione. Oltre all'individuazione di forme comuni di alterazione del calcestruzzo, quali la carbonatazione, l'attacco solfatico, l'attacco da cloruri, le reazioni alcali-aggregato e di ricristallizzazione di sali solubili, una nuova tipologia di degrado è stata per la prima volta osservata e studiata nei campioni di calcestruzzo dell'Area Ex-Agrimont, l'attacco sinergico solfatico-fosfatico. Questa forma di alterazione è stata investigata approfonditamente attraverso un approccio multi-analitico di profilo, consistente in una combinazione di microscopia ottica, micro-XRPD in luce di sincrotrone, microanalisi SEM-EDS, XRPD termica in situ, analisi termogravimetriche e termiche differenziali simultanee (TGA-DTA), spettroscopia di emissione atomica a plasma accoppiato induttivamente (ICP-OES) e modeling termodinamico. Tale forma di alterazione è risultata essere strettamente legata all'interazione tra inquinanti atmosferici ricchi in solfati e soluzioni ricche in fosfati e ioni ammonio rilasciati dall'impianto di produzione di fertilizzanti, e ha causato una grave decalcificazione delle matrici cementizie e la formazione di fosfati e solfati secondari secondo una marcata zonazione mineralogica e tessiturale, con associata stabilizzazione di fasi metastabili a causa dei particolari gradienti di pH e concentrazione degli inquinanti venutisi a stabilire all'interno dei materiali. Inoltre, si sono formate rare fasi in soluzione solida, le quali hanno successivamente subito fenomeni di parziale disidratazione correlati alle condizioni di esposizione.
Ma, Zepeng. "Fatigue models for life prediction of structures under multiaxial loading with variation in time and space." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX117/document.
Full textThe aim of this work is to propose a multi-scale approach to energy-based fatigue, which can estimate lifetimes associated with variable multidimensional loading. The foundation of the approach is to assume that the energy dissipated on a small scale governs the fatigue behavior. Each material point is associated to a stochastic distribution of weak points that are likely to plasticize and contribute to the dissipation of energy without affecting global macroscopic stresses. This amounts to adopting Dang Van's paradigm of high cycle fatigue. The structure is supposed to be elastic (or adapted) on a macroscopic scale. In addition, we adopt on the mesoscopic scale an elastoplastic behavior with a dependence of the plastic load function not only of the deviatoric part of the stresses, but also of the hydrostatic part. Linear kinematic hardening is also considered under the assumption of an associated plasticity. Instead of using the number of cycles as an incremental variable, the concept of temporal evolution of the load is adopted for a precise follow-up of the history of the actual loading. The effect of mean stress is taken into account in the mesoscopic yield function; a law of nonlinear accumulation of damage is also considered in the model. Fatigue life is then determined using a phenomenological law based on mesoscopic energy dissipation from the plastic accommodative cycle. The first part of the work focused on a proposal for a fatigue model with a simpler implementation gradient than the previous models
Tamoud, Abderrahman. "Mécanique multi-échelle et multiaxiale des composites souples multicouches : application à l'annulus fibrosus humain." Electronic Thesis or Diss., Université de Lille (2018-2021), 2021. http://www.theses.fr/2021LILUN034.
Full textThe damage in annulus fibrosus soft tissues is a complex multiscale phenomenon due to a complex structural arrangement of collagen network at different scales of hierarchical organization. A fully three-dimensional constitutive representation that considers the regional variation of the structural complexity to estimate annulus multiaxial mechanics till failure has not yet been developed. In the present PhD dissertation, a model, formulated within the framework of nonlinear continuum mechanics, is developed to predict deformation-induced damage and failure of annulus under multiaxial loading histories considering as time-dependent physical process both chemical-induced volumetric effects and damage accumulation.In a first part, a microstructure-based model is proposed to connect structural features, intrinsic mechanics and electro-chemical properties of annulus soft tissues. The multi-layered lamellar/inter-lamellar annulus model is constructed by considering the effective interactions between adjacent layers and the chemical-induced volumetric strain. The model/experiments comparison demonstrates that the evaluation of the overall time-dependent response involves considering stress, volumetric change and auxetic feature simultaneously in relation to structural features.In a second part, the model is enriched by considering the hierarchical structure of the soft tissue from the nano-sized collagen fibrils to the micro-sized oriented collagen fibers. The stochastic process of progressive damage events operating at different scales of the solid phase is introduced for the extracellular matrix and the network of nano-sized fibrils/micro-sized fibers. The directional effects on annulus mechanics and failure are highlighted in relation to external loading mode, structure features, damage events and hydration.In a third part, the model is further developed by considering the regional variation of the complex structural organization of collagen network at different scales to predict the regional anisotropic multiaxial damage of the intervertebral disc. After model identification using single lamellae extracted from different disc regions, the model predictability is verified for various multiaxial elementary loading modes representative of the spine movement. The stretching along the circumferential and radial directions till failure serves to check the predictive capacities of the annulus model for the different regions. Model results under simple shear, biaxial stretching and plane-strain compression are further presented and discussed.In a fourth part, a full human disc model is constructed using the regional annulus model to examine the heterogeneous mechanics in the disc core. Damage fields in the disc are analyzed under axial compression, axial twist and combined loadings to assess the areas where the risk of failure is the highest
Lougou, Komla Gaboutou. "Méthodes multi-échelles pour la modélisation des vibrations de structures à matériaux composites viscoélastiques." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0044/document.
Full textIn this thesis, multiscale homogenization techniques are proposed for vibration analysis of structures with viscoelastic composite materials. In the first part, the Double Scale Asymptotic Method is proposed for vibration modeling of large repetitive viscoelastic sandwich structures. For this kind of structures, la eigenfrequencies are closely located in well separated packets. The DSAM splits the initial problem of large size into two problems of relatively small sizes. The first problem is posed on few basic cells, and the second one is an amplitude equation with complex coefficients. The resolution of these equations permits to compute the damping properties that correspond to the beginning and the end of every packets of eigenmodes. In case of structure with frequency dependent Young modulus in the core, the diamant approach is used to solve the nonlinear problem posed on basic cells. The ADF and fractional derivative models are considered in numerical tests. By using the DSAM, one avoid the discretization of the whole structure, and the computation time and needed CPU memory are thus reduced. The proposed method is validated by comparing its results with those of the direct finite element method using the diamant approach. In the second part of this thesis, the multiscale finite element method (FE2) is proposed for computation of modal properties (resonant frequency and modal loss factors) of structures with composite materials. In the principle of the (FE2) method, the vibration problem is formulated at two scales: the scale of the whole structure (macroscopic scale) and the scale of a Representative Volume Element (RVE) considered as the microscopic scale. The microscopic problem is a nonlinear one and the macroscopic problem is linear. The nonlinearity at the microscopic scale is introduced by the frequency dependence of the Young modulus of the viscoelastic phases. This nonlinear problem is solved by the Asymptotic Numerical Method and its automatic differentiation tools realizable in Matlab, Fortran or C++. From this approach, numerical tool that is generic, flexible, robust and inexpensive in term of CPU time and memory is proposed for vibration analysis of viscoelastic structures. The constant Young modulus and frequency dependent Young modulus are considered in validation tests. The results of numerical simulation with ABAQUS are used are reference. The model is then used to compute the modal properties of sandwich structure with viscoelastic composite core. To test the capacities of the proposed approach to design sandwich viscoelastic structure with high damping properties, the influence of parameters of the inclusions are studied
Perdikis, Dionysios. "Functionnal organization of complex behavioral processes." Thesis, Aix-Marseille 2, 2011. http://www.theses.fr/2011AIX22050/document.
Full textBehavioural studies suggest that complex behaviours are multiscale processes, which may be composed of elementary ones (units or primitives). Traditional approaches to cognitive mod-elling generally employ reductionistic (mostly static) representations and computations of simplistic dynamics. The thesis proposes functional architectures to capture the dynamical structure of both functional units and the composite multiscale behaviours. First, a mathe-matical formalism of functional units as low dimensional, structured flows in phase space is introduced (functional modes). Second, additional dynamics (operational signals), which act upon functional modes for complex behaviours to emerge, are classified according to the separation between their characteristic time scale and the one of modes. Then, complexity measures are applied to distinct architectures for a simple composite movement and reveal a trade off between the complexities of functional modes and operational signals, depending on their time scale separation (in support of the control effectiveness of architectures employing non trivial modes). Subsequently, an architecture for serial behaviour (along the example of handwriting) is demonstrated, comprising of functional modes implementing characters, and operational signals much slower (establishing a mode competition and ‘binding’ modes into sequences) or much faster (as meaningful perturbations). All components being coupled, the importance of time scale interactions for behavioural organization is illustrated. Finally, the contributions of modes and signals to the output are recovered, appearing to be possible only through analysis of the output phase flow (i.e., not from trajectories in phase space or time)
Bondon, Arnaud. "Stabilité des écoulements stratifiés en coextrusion : Etude multi-échelle du rôle de l’architecture du copolymère aux interfaces." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0100.
Full textSeveral polymers can be combined in one multilayer structure by reactive coextrusion. Tie-layers are often used to compatibilize the adjacent layers and may reduce or suppress the interfacial instabilities and the defects in the multilayer coextrusion flow. However, an additional defect defined as the “grainy” defect can be observed. In the best of our knowledge, no study in literature has been devoted to understand its origin. The phenomena are quite complex due to the coupling of the effects of flow and the physico-chemical mechanisms at the interface. The aim of this work is to understand the relations between the instabilities and the defects encountered in multilayer coextruded films and the role of the copolymer formed in-situ between tie and barrier layers. Polyamide 6 (PA6) and ethylene-vinyl alcohol copolymer (EVOH) were used as the barrier layers sandwiched in a polypropylene (PP) with or without a polypropylene grafted maleic anhydride (PP-g-MA) as a tie-layer. The effect of the process parameters and the structure of the polymers on the generation of the “grainy” defect was assessed in correlation with the rheological and the physicochemical properties of the layers. These experiments have shown that this defect appeared mainly in the compatibilized EVOH system and could be distinguished from the usual coextrusion instabilities. The interfacial properties between tie and barrier layers were investigated. The characterization of the interfacial morphology by TEM and AFM highlighted an irregular and rough interface between PP-g-MA and EVOH while a flat interface was observed with PA6 and PP-g-MA. Step shear and startup elongation rheology was shown to be sensitive to the copolymer at the polymer/polymer interface. The study of the interfacial properties highlighted that the copolymer architecture significantly impacts the interfacial roughness and the rheology of the multilayer stuctures. Hence, relations between the relaxation process, the interfacial morphology and the copolymer architecture were established in correlation with the generation of the macroscopic grainy defect in coextrusion
Barbarroux, Loïc. "Contributions à la modélisation multi-échelles de la réponse immunitaire T-CD8 : construction, analyse, simulation et calibration de modèles." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC026/document.
Full textUpon infection by an intracellular pathogen, the organism triggers a specific immune response,mainly driven by the CD8 T cells. These cells are responsible for the eradication of this type of infections and the constitution of the immune repertoire of the individual. The immune response is constituted by many processes which act over several interconnected physical scales (intracellular scale, single cell scale, cell population scale). This biological phenomenon is therefore a complex process, for which it is difficult to observe or measure the links between the different processes involved. We propose three multiscale mathematical models of the CD8 immune response, built with different formalisms but related by the same idea : to make the behavior of the CD8 T cells depend on their intracellular content. For each model, we present, if possible, its construction process based on selected biological hypothesis, its mathematical study and its ability to reproduce the immune response using numerical simulations. The models we propose succesfully reproduce qualitatively and quantitatively the CD8 immune response and thus constitute useful tools to further investigate this biological phenomenon
Fedorov, Vadim. "Affine invariant image comparison and its applications." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/398002.
Full textImage comparison is a main ingredient in many image processing and computer vision problems and applications, and not surprisingly it is a very diverse topic. The subject of this thesis is the comparison of local patches of images by means of similarity measures (or distance functions). In particular, we are interested in affine invariant patch-wise image comparison which opens the door to a more thorough analysis of similarities and self-similarities present in natural images. Our work is based on a recently proposed axiomatic framework for similarity measures between images defined on Riemannian manifolds. At the beginning we derive and study some affine invariant similarity measures and then present two novel methods built around them. The first method for exemplar-based image inpainting is aimed at the recovery of occluded, missing or corrupted parts of an image, in such a way that the reconstructed image looks natural. It is capable of reconstructing textures under perspective or even more complex distortions. The second method extends the well-known Non-Local Means approach for image denoising by taking advantage of affine invariant self-similarities of real images. Our extension improves the original method in both quantitative and qualitative assessments, and the results are promising when compared with state-of-the-art methods.
Kinvi-Dossou, Gbèssiho Raphaël. "Étude de la résistance à l’impact et de l’endommagement des composites stratifiés à matrice Elium acrylique : caractérisation expérimentale et modélisation numérique multi-échelle." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0249/document.
Full textIn the race for light materials able of meeting modern environmental challenges, an acrylic resin (Elium) has been developed. Elium is a thermoplastic resin able to replace thermosetting matrices, which are widespread nowadays in the industrial world. The present study aims to evaluate the impact resistance and to understand the failure mechanisms of composite laminates based on acrylic matrix under impact loading. We provide a contribution to the multiscale analysis of the impact resistance of laminated composite.First, the impact resistance and the damage tolerance of the acrylic resin based composites were compared with those of conventional composites. Then, the impact performance of the laminated composites has been enhanced by adding copolymer blocks to the liquid acrylic resin. These copolymers are able to form micelles of nanometer sizes, which lead to the improvement of both the acrylic matrix fracture toughness and the impact resistance. The effects of the impact energy, temperature, and composition in nano-copolymers have also been investigated.In order to provide a numerical tool for the prediction of the impact response of the glass fiber/Acrylic laminates, two strategies have been analyzed. The first one, performed at the macroscopic scale, considers the woven ply of the laminate as homogeneous material, and the second one (at the mesoscopic scale), deals with a realistic geometrical description of the yarns undulation. Both models use cohesive zones at the interface between the adjacent plies, to simulate the delamination. For this purpose, experimental and numerical delamination tests were performed to feed the inter-ply damage model. Mechanical tests for material characterization were also performed on specimens in order to identify the ply-damage model parameters. The Mechanics of Structure Genome (MSG) and a finite element based micromechanics approaches were then conducted to evaluate the effective thermomechanical properties of the yarns and the plain woven composite laminate. The realistic topological and morphological textures of the composite were accounted through Texgen software. These numerical impact simulations were performed using the finite element software ABAQUS/Explicit. Both models were implemented through a user material subroutine VUMAT. The obtained results appear in a good agreement with the experimental data and confirm the relevance of the proposed approach
Visseq, Vincent. "Calcul haute performance en dynamique des contacts via deux familles de décomposition de domaine." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2013. http://tel.archives-ouvertes.fr/tel-00848363.
Full textMaynadier, Anne. "Couplages thermomécaniques dans les alliages à mémoire de forme : mesure de champs cinématique et thermique et modélisation multiéchelle." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2012. http://tel.archives-ouvertes.fr/tel-01044998.
Full textMoyeda, Morales Arturo. "Multiscale Analysis of Reinforced Concrete Structures." Thesis, 2018. https://doi.org/10.7916/D8VH75Q3.
Full textWatson, Alexander Bruce. "Wave dynamics in locally periodic structures by multiscale analysis." Thesis, 2017. https://doi.org/10.7916/D89W0SSM.
Full text"Multiscale Analysis of Nanocomposites and Their Use in Structural Level Applications." Doctoral diss., 2014. http://hdl.handle.net/2286/R.I.25901.
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Doctoral Dissertation Aerospace Engineering 2014
(5930414), Tong Wu. "TOPOLOGY OPTIMIZATION OF MULTISCALE STRUCTURES COUPLING FLUID, THERMAL AND MECHANICAL ANALYSIS." Thesis, 2019.
Find full textOztop, Muin S. "Multiscale Experimental Analysis in Plasticity: Linking Dislocation Structures to Continuum Fields." Thesis, 2011. https://doi.org/10.7916/D8NP2BS1.
Full textVarghese, Julian. "A Finite Element Framework for Multiscale/Multiphysics Analysis of Structures with Complex Microstructures." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-7054.
Full textBrown, Donald. "Multiscale Methods for Fluid-Structure Interaction with Applications to Deformable Porous Media." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11569.
Full textBurrell, Michael. "Multicohort Management and LiDAR: New Forest Management Tools for Northeastern Ontario Boreal Mixedwood Bird Communities." Thesis, 2009. http://hdl.handle.net/1807/18228.
Full textLiu, Kai. "Concurrent topology optimization of structures and materials." Thesis, 2013. http://hdl.handle.net/1805/3755.
Full textTopology optimization allows designers to obtain lightweight structures considering the binary distribution of a solid material. The introduction of cellular material models in topology optimization allows designers to achieve significant weight reductions in structural applications. However, the traditional topology optimization method is challenged by the use of cellular materials. Furthermore, increased material savings and performance can be achieved if the material and the structure topologies are concurrently designed. Hence, multi-scale topology optimization methodologies are introduced to fulfill this goal. The objective of this investigation is to discuss and compare the design methodologies to obtaining optimal macro-scale structures and the corresponding optimal meso-scale material designs in continuum design domains. These approaches make use of homogenization theory to establish communication bridges between both material and structural scales. The periodicity constraint makes such cellular materials manufacturable while relaxing the periodicity constraint to achieve major improvements of structural performance. Penalization methods are used to obtain binary solutions in both scales. The proposed methodologies are demonstrated in the design of stiff structure and compliant mechanism synthesis. The multiscale results are compared with the traditional structural-level designs in the context of Pareto solutions, demonstrating benefits of ultra-lightweight configurations. Errors involved in the mult-scale topology optimization procedure are also discussed. Errors are mainly classified as mesh refinement errors and homogenization errors. Comparisons between the multi-level designs and uni-level designs of solid structures, structures using periodic cellular materials and non-periodic cellular materials are provided. Error quantifications also indicate the superiority of using non-periodic cellular materials rather than periodic cellular materials.
Thomas, Dilip Mathew. "Symmetry in Scalar Fields." Thesis, 2014. http://etd.iisc.ernet.in/handle/2005/2989.
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