Bibliographies: 'Architectured structures' – Grafiati (2024)

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The architectured metallic materials are a class of composite materials that combines two or more metals/alloys with a specific spatial ordering (architecture). The main goal behind the preparation of such materials is to obtain properties that are not achievable by a single material. The internal architecture thus creates an extra degree of freedom in materials design. Based on theoretical considerations three aluminum alloy structures containing square, triangle and sinusoidal iron beam patterns have been prepared by a cold spray deposition technique. Strength properties difference and good bonding of the reinforcing Fe structure to the Al matrix has been found to be important for effective improvement of final properties. Incorporating about 30 vol. % structured iron beams into the Al matrix resulted in a macroscopic performance of the architectured multimaterial similar to Ti alloys.

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Nitrogen-doped hybrid-dimensional nanocarbons are architectured into special structures and used for fabrication of solid-state flexible supercapacitors showing high-performance energy storage capacity.

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ABSTRACTShape-memory hydrogels (SMHs) are potential candidate materials for biomedical applications as they can mimic the elastic properties of soft tissue and exhibit shape transformations at body temperature. Here we explored, whether architectured SMHs can be designed by incorporating oligo(ε-caprolactone) (OCL, ${\overline M _n}$ = 4500 g·mol-1, Tm = 54 °C) side chains as switching segment into hydrophilic polymer networks based on N-vinylpyrrolidone as backbone forming component and oligo(ethylene glycol)divinylether (OEGDVE, ${\overline M _n}$ = 250 g·mol-1) as crosslinker. By utilizing NaCl and NaHCO3 as porogene during thermal crosslinking architectured hydrogels having pore diameters between 30 and 500 µm and wall thicknesses ranging from 10 to 190 µm in the swollen state were synthesized. According to the porous microstructure, a macroscopic form stability was obtained when the polymer networks were swollen until equilibrium in water. Material properties were investigated as function of the OCL content, which was varied between 20 and 40 wt%. In compression experiments the architectured hydrogels exhibited strain fixity and strain recovery ratios above 80%. These architectured SMHs might enable biomaterial applications as smart implants with the recovery of bulky structures from compact shapes.

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Abstract An effective technique for improving electrochemical efficiency is to rationally design hierarchical nanostructures that completely optimize the advantages of single components and establish an interfacial effect between structures. In this study, core–shell NiMoO4@Ni9S8/MoS2 hetero-structured nanorods are prepared via a facile hydrothermal process followed by a direct sulfurization. The resulting hierarchical architecture with outer Ni9S8/MoS2 nanoflakes shell on the inner NiMoO4 core offers plentiful active sites and ample charge transfer pathways in continuous heterointerfaces. Ascribing to the porous core–shell configuration and synergistic effect of bimetal sulfides, the obtained NiMoO4@Ni9S8/MoS2 as electrode material presents an unsurpassed specific capacity of 373.4 F g−1 at 10 A g−1 and remarkable cycling performance in the 6 M KOH electrolyte. This work delivers a rational method for designing highly efficient electrodes for supercapacitors, enlightening the road of exploring low-cost materials in the energy storage domain. Graphical Abstract

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Recent advances in lithography technology and the spread of 3D printers allow us a facile fabrication of special materials with complicated microstructures. The materials are called “designed materials” or “architectured materials” and provide new opportunities for material development. These materials, which owing to their rationally designed architectures exhibit unusual properties at the micro- and nano-scales, are being widely exploited in the development of modern materials with customized and improved performance. Meta-materials are found to possess superior and unusual properties as regards static modulus (axial stress divided by axial strain), density, energy absorption, smart functionality, and negative Poisson’s ratio (NPR). However, in spite of recent developments, it has only been feasible to fabricate a few such meta-materials and to implement them in practical applications. Against such a backdrop, a broad review of the wide range of cellular auxetic structures for mechanical metamaterials available at our disposal and their potential application areas is important. Classified according to their geometrical configuration, this paper provides a review of cellular auxetic structures. The structures are presented with a view to tap into their potential abilities and leverage multidimensional fabrication advances to facilitate their application in industry. In this review, there is a special emphasis on state-of-the-art applications of these structures in important domains such as sensors and actuators, the medical industry, and defense while touching upon ways to accelerate the material development process.

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Dans cette thèse à l'interface entre élasticité et géométrie, nous nous attachons à développer, étudier et programmer des structures gonflables élancées qui changent de forme. Une première stratégie consiste à fabriquer des plaques d'élastomère incluant des réseaux de canaux. L’expansion de ces canaux mis sous pression se produit presque exclusivement perpendiculairement à leur direction principale. Le choix de l'orientation et de la densité locales du réseau de canaux permet de contrôler la direction et l'intensité de la pseudo-croissance de cette plaque hom*ogénéisée. Sous pression, la métrique cible de ces objets devient en général incompatible avec l'état plan. La structure flambe alors spontanément pour adopter une forme qui minimise l’énergie élastique, ce qui revient à suivre la métrique imposée par gonflement dans le cas d’objets minces. Une deuxième technique consiste à thermocoller entre elles deux feuilles minces inextensibles selon un réseau de lignes qui définit des canaux gonflables. Le système élémentaire, constitué d'un seul tube formé de deux rubans sinueux joints le long de leurs bords, voit sa courbure amplifiée lors du gonflement. Nous mesurons, expliquons et exploitons cet effet surprenant qui résulte de la maximisation du volume contenu dans le tube sous la contrainte de l'inextensibilité de l'enveloppe. Nous étendons l'étude à des structures bidimensionnelles qui voient la distance entre deux lignes de couture parallèles se contracter lors du gonflement. Le contrôle de la déformation hom*ogénéisée dans le plan permet de programmer le déploiement dans l'espace de surfaces complexes à partir de ces structures initialement planes
In this thesis at the interface between geometry and mechanics, we aim at developing, studying and programming slender morphing inflatables structures. A first strategy consists in manufacturing elastomeric plates embedding a network of channels, which expand, when inflated, mainly perpendicular to their local orientation, similarly to simple elastic tubes. Playing with both the orientation and density of channels, we control the direction and intensity of the in-plane hom*ogenized ``growth", in general incompatible with a flat geometry. The structure spontaneously buckles and adopts a shape which minimizes its elastic energy. For very thin slender bodies, this reduces to follow the target metric induced by inflation. We then study the inflation of structures made of two superimposed inextensible thin sheets, sealed together along a specific line network. Starting with flat curved ribbons, we observe and rationalize the surprising overcurvature upon inflation by maximizing the inner volume given the inextensibility constraint. We finally extend our investigation to two-dimensional structures and control the in-plane contraction upon inflation, which occurs perpendicular to the seam?s direction. We program the morphing of such stiff inflatable structures and investigate their mechanics

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Les Structures atomiques Quasi-périodiques (QP) possèdent des propriétés particulières, notamment dans le domaine vibrationnel. Il pourrait être intéressant de pouvoir transférer ces propriétés à des méta-matériaux macroscopiques. Des réseaux de poutres quasi-périodiques 2D sont étudiés dans cette thèse dans le cadre du modèle élément finis (EF) poutre Euler Bernoulli. Ces réseaux de poutres peuvent facilement être produits par fabrication additive ou par découpe laser. Il est possible de faire varier l'élancement des poutres (le ratio hauteur sur longueur) qui est un paramètre intéressant pour modifier la réponse mécanique du réseau. En utilisant la méthode EF, l'influence de l'élancement des poutres sur la réponse vibratoire des réseaux de poutres QP est étudiée. La méthode numérique Kernel Polynomial (KPM) est adaptée avec succès de la dynamique moléculaire aux réseaux de poutres pour étudier leurs modes de vibration sans avoir à diagonaliser complètement la matrice dynamique. Les réseaux de poutres QP présentent des propriétés similaires à leur compère atomique: en particulier la localisation de modes sur des sous-structures et une relation de dispersion hiérarchisée. Le comportement à la fracture est aussi étudié étant donné que les symétries présentes dans les QP pourraient permettre des réseaux de poutres ne présentant pas de plans faibles pour la propagation de fissures. Cela a été démontré d'après des calculs EF statiques avec un critère de fracture fragile sur l'énergie de déformation. Les simulations statiques ne suffisent pas car elles ne peuvent pas capturer les phénomènes dynamiques complexes qui apparaissent lors de la fissuration fragile. Les propriétés de vibration du QP pourraient aussi avoir un impact sur la propagation dynamique de fissure. Un modèle dynamique de fissuration est développé afin d'étudier l'impact de l'élancement sur la capacité des réseaux de poutres QP à dissiper de l'énergie par fissuration. Finalement une méthode Coarse Graining est développée pour identifier un milieu Cosserat continu équivalant au réseau de poutres QP pour différentes échelles. Cette méthode permet d'identifier la densité, les déformations, les contraintes et donc les modules d'élasticité du milieu Cosserat équivalent, permettant ainsi une meilleure compréhension du rôle des sous structures précédemment identifiées
Quasi periodic (QP) structures have shown peculiar properties in the atomistic domain, especially the vibrational one. It could be interesting to be able to transpose these properties in macroscopic meta-materials. Quasi periodic 2D beam lattices are studied in this thesis due to the simplicity of the Euler Bernoulli finite element (FE) model. These beam lattices can easily be produced by additive manufacturing or by laser cutting. It is possible to vary the beam slenderness (i.e the ratio of height over length) that is a interesting parameter to modify the mechanical response of the lattice. Using finite element method, the influence of the beam slenderness over the vibration behavior of the QP beam lattices will be studied. The Kernel Polynomial numerical Method (KPM) is successfully adapted from molecular dynamics simulations in order to study vibrational modes of FE beam lattices without having to fully diagonalize the dynamical matrix. The QP lattices show similar properties as their atomic counterpart e.g mode localization over sub-stuctures and hierarchical dispersion relation. The fracture behavior is also studied, as the special symmetries allowed by the quasi periodicity could result in beam lattices without weak planes for crack propagation. It was proved to be true from static FE simulations with a brittle strain energy breaking criterion. Static simulations were not enough and do not grasp the complex dynamical phenomena taking place in brittle fracture. A dynamic crack propagation model was thus developed. The vibrational properties of quasi periodic structures could also have an impact on the dynamic crack propagation. Several simulations are run in order to study the impact of the slenderness on the energy dissipated by fracture of QP lattices. Finally, a coarse graining method (CG) was developed to identify a continuous Cosserat medium at different scales from the FE beam model. This CG method allows to identify, density, strain, stress and elastic moduli of an equivalent continuous Cosserat. This allows a better understanding of the role of previously identified characteristic sub structures

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La question du stockage de chaleur est non négligeable dans le contexte actuel. L’une des solutions est l’utilisation de matériaux à changement de phase (MCP). Cependant leurs propriétés thermiques restent inadaptées et il est absolument nécessaire d'utiliser un substrat conducteur afin de maximiser le rendement de ces systèmes.L’objectif de cette thèse est la compréhension et la caractérisation des phénomènes physiques mis en œuvre, et l’optimisation de structures architecturés dans de tels systèmes de stockage de chaleur. Une double démarche a été adoptée à la fois expérimentale et numérique sur des structures d’accueil du MCP relativement simples (ailettes) puis plus complexes (mousses ouvertes). Nous avons pu étudier des paramètres géométriques (longueur, porosité, espacement et épaisseur des ailettes, taille de cellules des mousses) de la structure d'accueil, de son matériau constitutif et de son orientation. Les résultats expérimentaux corroborent les simulations numériques menées ce qui a permis de réaliser une étude plus systématique sur les paramètres analysés et notamment d’identifier dans quel cas il fallait prendre en compte la convection naturelle. Enfin à partir de ces résultats nous avons développé un outil permettant d’optimiser des structures pour un cahier des charges défini
The problematic of heat storage is important in the present context. One of the solutions is to use phase change materials (PCM). Nevertheless their thermal properties are poors and a conductive substracte must absolutely be used in order to maximise the yield of theses systems.The purposes of this PhD are the physics phenomena implementation understanding and characterization, and the optimization of architectured structures for heat storage systems. A dual approach was adopted both experimental and numerical on simple PCM reception structures (fins) and on more complex ones (open foams). We analyzed influences of geometrical parameters (system lenght and porosity, thickness and space betweens fins, cellfoam size) from reception structure, its constituent material and its orientation. Experimental results support well with numerical simulations. This permits to pursue a more systematical study about analyzed parameters, and notably to identify in which cases natural convection has to be taken into account. Finally, from these results, we developped a tool which permits to optimize architectured structures for a defined bill of specifications

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La conception sur-mesure de matériaux architecturés à l'échelle du milli/centimètre est une stratégie pour développer des matériaux de structure plus performants vis-à-vis de cahiers des charges multifonctionels. Ce travail de thèse s'intéresse en particulier à la conception optimale de panneaux architecturés périodiques, dans le but de combiner des exigences mécaniques de flexion et de cisaillement, ainsi que de conductivité thermique. Le comportement élastique peut être prédit grâce à l'identification sur la cellule périodique des coefficients de la matrice des souplesses équivalente. Ces calculs d'hom*ogénéisation ont été mis en oeuvre par éléments finis pour estimer en particulier les souplesses en flexion et en cisaillement transverse. Après validation expérimentale, cette méthode de calcul constitue un outil d'évaluation des performances mécaniques pour chaque géométrie de cellule périodique (2D ou 3D). À titre d'exemple, et dans un contexte de développement de solutions matériaux architecturés pour l'automobile, la conception de tôles "texturées" est proposée en menant une étude paramétrique à l'aide de cet outil. L'implémentation d'un algorithme d'optimisation topologique couplé à la procédure d'hom*ogénéisation permet d'enrichir les méthodes de conception sur-mesure en élargissant l'espace de recherche des "architectures". Après l'étude modèle du compromis entre flexion et cisaillement, le cas industriel d'un panneau sandwich isolant est traité. Dans ce cas, l'optimisation fournit plusieurs compromis prometteurs entre rigidité en cisaillement et isolation thermique. Ces géométries ont été réalisées et testées, et une nouvelle version améliorée du panneau sandwich a été sélectionnée.

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Les cartographes ont réalisé depuis longtemps qu'il est impossible de dessiner une carte plane du globe terrestre sans déformer les continents. Carl Gauss a généralisé cette contrainte géométrique fondamentale dans son "remarquable'' Theorema Egregium. Pouvons-nous inverser le problème et obtenir une forme 3D en changeant localement les distances entre les points (c'est-à-dire la métrique) sur une feuille initialement plane? Cette stratégie est largement employée dans la Nature: feuilles ou pétales peuvent adopter des formes très complexes sous l'effet d'une croissance différentielle. Cependant, imposer la métrique ne suffit pas à définir la géométrie d'une surface et il est nécessaire de contrôler également la courbure locale pour trancher entre différentes isométries. Au cours de cette thèse, nous nous attaquons au problème général de mise en forme à travers trois différentes stratégies. Du point de vue de l'ingénieur, les changements de métrique peuvent être imposés par la mise sous pression de canaux insérés dans une plaque d'élastomère ou entre deux pièces de tissus en induisant une extension ou contraction le long de lignes directrices. Dans un premier temps nous décrivons comment un motif en zigzag à une échelle méso apporte un degré de liberté supplémentaire dans l'espace de design de structures 3D complexes. Un second chapitre est consacré au contrôle de la courbure locale (en plus de la métrique) grâce à des canaux de section asymétrique. Au-delà de rubans de courbure contrôlée ou de structures origami auto-déployables, différentes formes isométriques peuvent être produites grâce à cette technique polyvalente. Nous montrons dan un troisième chapitre comment la flexion des facettes de structures origami au plis courbés peut être exploitée pour déployer efficacement des structures tridimensionnelles
Cartographers have early realized that it is impossible to draw a flat map of the Earth without distorting continents. Carl Gauss later generalized this geometrical constrain in his seminal Theorema Egregium. Can we invert the configuration and obtain 3D shapes by changing local distances (ie, metrics) in an initially flat plate? This strategy is widely used in Nature: leaves or petals may develop into very complex shapes through differential growth. Nevertheless, imposing metrics is not enough to define the geometry of a surface and controlling local bending is necessary to select between different isometric shapes. In this thesis, we address shape morphing through three different strategies. From an engineering point of view, metric changes can be imposed by inflating channels embedded in a polymeric plate or in between to pieces of fabric as it induces extension or contraction along director lines. We first show how a zigzag meso-structure brings an extra degree of freedom in the design space to program complex 3D structures. A second chapter is dedicated to the control of local bending (in addition to metrics) by designing channels of non-symmetric cross-section. In addition to bending ribbons or self-folding origami structures, different isometric shapes can be designed with this versatile technique. In a third chapter we finally show how bending the facets in curved fold origami can be harvested to deploy efficiently 3D structures

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Les méthodes d'optimisation de forme s’industrialisent progressivement, elles permettent la conception automatisée de structures aux propriétés optimales. Elles constituent aussi un outil d'exploration majeur pour la conception de nouveaux matériaux.Dans une première partie nous utilisons ces méthodes afin de générer des matériaux architecturés aux propriétés thermoélastiques effectives cibles et extrêmes. En plus de proposer différentes solutions, nous répertorions les différents mécanismes œuvrant au contrôle des ces propriétés. Dans ce contexte nous proposons aussi de prendre en compte l'influence des interfaces comportant un gradient de propriétés sur les architectures obtenues.Nous étudions ensuite les procédés de fabrication pouvant être utilisés afin de réaliser ces matériaux. Les méthodes de fabrication additive, considérées comme le vecteur d'une prochaine révolution industrielle, constituent une piste que nous considérerons tout particulièrement. Nous proposons plusieurs solutions pour prendre en compte les limitations et les effets collatéraux de ces procédés de fabrication au sein de processus d'optimisation de forme. Nous traitons le problème de la prise en compte des propriétés induites par la méthode de fabrication Fiber Deposition Molding (FDM), à savoir des propriétés anisotropes orientées. Nous proposons ensuite une approche pour traiter le problème des dépôts en porte-à-faux à l'aide d'un critère mécanique.Enfin, nous abordons la prise en compte des non-linéarités géométriques au sein de calculs d'optimisation de forme et discutons de leurs apports ainsi que de leurs limitations. Nous présentons plusieurs applications pour la conception automatisée d'actuateurs non linéaires
Shape optimization methods are promising methods and are gradually becoming industrialized. They provide the ability to automatically design structures with optimal behavior. They are outstanding tools for exploration and design of new materials.We use these methods to generate architectured multi-phased materials with prescribed thermoelastic properties. We first propose several solutions and we classify them by the mechanisms they rely on in order to control the effective properties. We also propose to evaluate the influence of an interface with a gradient of properties on the obtained architectures.Eventually we focus on the plausible manufacturing solution to produce our architectured materials. In this context, additive manufacturing methods (often considered as the support of an incoming industrial revolution) is our main option. We introduce several strategies to circumvent some limitations and side effects of these manufacturing methods during optimization process. We particularly focus on Fiber Deposition Molding, which induce an important mechanical anisotropy in processed parts. Then we consider the problem of overhangings features in design and propose a way to handle them prior to additive manufacturing using a mechanical criteria.Finally we take into account geometrical non linearities in optimization process. We highlight the pros and cons of this new modeling by presenting several applications of non linear actuators design

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L’émergence des techniques de fabrication additive permet de réaliser des structures lattices de géométries complexes. Leur potentiel, en termes de légèreté, d’absorption des chocs, de personnalisation et de design attise l'intérêt de l'équipementier sportif DECATHLON, qui envisage ces méso-structures pour des applications casques et chaussures. Ce travail étudie le comportement de différentes géométries de lattices soumises à des chargements de compression.Dans une première partie, la faisabilité technique de produits sportifs en lattices a été évaluée par des compressions statiques et des impacts dynamiques adaptés aux normes casques et chaussures. Cette étude préliminaire a permis de mettre en évidence l’intérêt des lattices dans les applications sportives.La deuxième phase de ce travail a consisté à développer des modèles et méthodes de dimensionnement de lattices. Le comportement mécanique de lattices octets réalisées en deux matériaux (PA12 et TPU) a été caractérisé. La géométrie et le respect dimensionnel de ces structures ainsi que la quantification des champs cinématiques sous sollicitations ont été analysés par micro-tomographie.Un modèle numérique réalisé sous un code éléments finis a ensuite été proposé. Une confrontation aux observations expérimentales a permis d'évaluer la pertinence du modèle. Pour une meilleure représentativité des zones de jonction des poutres (les vertices), et donc une meilleure exploitation des modélisations, une rigidification locale aux vertices est étudiée par un plan d'expérience numérique
Additive manufacturing enables the production of complex parts such as lattice structures. Their potential, in terms of lightness, improved impact performances, customization and design, draws the attention of the sports equipment manufacturer DECATHLON, who is considering these meso-structures for helmets and shoes applications. This study focuses on the behaviour of several lattices subjected to compressive loading.A preliminary experimental phase identified the behaviour of two materials (PA12 and TPU) produced by a laser sintering process (SLS). The technical feasibility of lattices structures in sports products was then evaluated using static compressions and dynamic impacts adapted to helmet and footwear standards.The second stage of the study consists in developing numerical tools for the design of lattices structures. Several lattices were produced. There mechanical behaviour was characterized in several aspects: the static response under compressive loadings was compared to foams conventionally used for energy absorption; the dimensional stability of the structures and the quantification of the kinematic fields under stress were assessed by micro-tomography.Thanks to these observations, the relevance of a numerical lattice model realized under a finite element code was evaluated. Its lack of representativeness of the junction zones of the beams (the vertices) limits its use. Nevertheless, a local stiffening at the vertices, studied by a numerical design of experiment, greatly improved the modeling

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Cette thèse suit une démarche " materials-by-design " avec pour objectif le développement d'une méthode de conception dédiée aux panneaux sandwichs architecturés pour l'obtention de propriétés multifonctionnelles. Cette méthode s'appuie sur l'utilisation d'un algorithme génétique permettant simultanément une sélection de matériaux (variables discrètes) et un pré-dimensionnement du panneau (variables continues). Trois architectures de cœur ont été étudiées : les mousses, les nids-d'abeilles hexagonaux et les treillis tétraédriques. Dans cette thèse, on définit deux approches différentes de sélection des matériaux. Dans un premier temps, les matériaux architecturés sont considérés comme des matériaux existants, dont les propriétés sont référencées dans une base de données fermée. Cette approche est appelée optimisation par " voie réelle ". Afin d'ouvrir les possibilités en termes de sélection de matériaux, la deuxième approche considère une description semi-continue des matériaux architecturés et est appelée optimisation par " voie virtuelle ". Le matériau cœur est décrit par un matériau constitutif (variable discrète) et par une ou plusieurs variables géométriques continues représentant l'architecture. Utilisant ces deux approches, différentes propriétés d'emploi des panneaux sandwichs sont évaluées : rigidité et résistance en flexion, atténuation acoustique, résistance et isolation thermique, et enfin résistance aux chocs impulsionnels. Chaque fonction est optimisée à masse minimale par optimisation bi-objectifs. Différents cas d'optimisation tri-objectifs sont également présentés afin d'évaluer la compatibilité entre propriétés. En effet, la forme de la surface de compromis obtenue donne une indication sur la compatibilité entre les différents critères. Cette étape d'optimisation permet également l'identification des paramètres de conception optimaux. Dans le cas d'une optimisation par " voie virtuelle ", une comparaison directe entre architectures est aussi possible. Cependant, la démarche d'optimisation mise en place est complexe car globale et travaillant avec des variables mixtes. Deux méthodes mixtes, couplant l'algorithme génétique avec d'autres approches, sont proposées pour permettre un accroissem*nt de la complexité de l'analyse tout en garantissant une complexité raisonnable de l'optimisation.

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L’émergence des techniques de fabrication additive permet de réaliser des structures lattices de géométries complexes. Leur potentiel, en termes de légèreté, d’absorption des chocs, de personnalisation et de design attise l'intérêt de l'équipementier sportif DECATHLON, qui envisage ces méso-structures pour des applications casques et chaussures. Ce travail étudie le comportement de différentes géométries de lattices soumises à des chargements de compression.Dans une première partie, la faisabilité technique de produits sportifs en lattices a été évaluée par des compressions statiques et des impacts dynamiques adaptés aux normes casques et chaussures. Cette étude préliminaire a permis de mettre en évidence l’intérêt des lattices dans les applications sportives.La deuxième phase de ce travail a consisté à développer des modèles et méthodes de dimensionnement de lattices. Le comportement mécanique de lattices octets réalisées en deux matériaux (PA12 et TPU) a été caractérisé. La géométrie et le respect dimensionnel de ces structures ainsi que la quantification des champs cinématiques sous sollicitations ont été analysés par micro-tomographie.Un modèle numérique réalisé sous un code éléments finis a ensuite été proposé. Une confrontation aux observations expérimentales a permis d'évaluer la pertinence du modèle. Pour une meilleure représentativité des zones de jonction des poutres (les vertices), et donc une meilleure exploitation des modélisations, une rigidification locale aux vertices est étudiée par un plan d'expérience numérique
Additive manufacturing enables the production of complex parts such as lattice structures. Their potential, in terms of lightness, improved impact performances, customization and design, draws the attention of the sports equipment manufacturer DECATHLON, who is considering these meso-structures for helmets and shoes applications. This study focuses on the behaviour of several lattices subjected to compressive loading.A preliminary experimental phase identified the behaviour of two materials (PA12 and TPU) produced by a laser sintering process (SLS). The technical feasibility of lattices structures in sports products was then evaluated using static compressions and dynamic impacts adapted to helmet and footwear standards.The second stage of the study consists in developing numerical tools for the design of lattices structures. Several lattices were produced. There mechanical behaviour was characterized in several aspects: the static response under compressive loadings was compared to foams conventionally used for energy absorption; the dimensional stability of the structures and the quantification of the kinematic fields under stress were assessed by micro-tomography.Thanks to these observations, the relevance of a numerical lattice model realized under a finite element code was evaluated. Its lack of representativeness of the junction zones of the beams (the vertices) limits its use. Nevertheless, a local stiffening at the vertices, studied by a numerical design of experiment, greatly improved the modeling

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This research began with an exploration of the phenomenon of cultural conflict and fusion in the process of architectural modernization in Taiwan. It will examine the impact of modern and contemporary theories on the practice of architecture of the island. It will then seek out the essence of Chinese classical architecture in order to develop an approach for the development of the future Chinese/Taiwanese architecture. In addition, the findings of the study could serve as a reference for scholars who would pursue historical and theoretical studies of in the subject, or for architects who are seeking design concepts to enhance their projects.The study utilizes an interpretive-historical methodology. It emphasizes that researchers should investigate social phenomena within broader and more complex contexts of what to uncover the underlying cultural factors. To highlight their significance, the author will pursue a hypothetic project to examine and demonstrate the meaningfulness and applicability of the concepts learned from the research.Efforts were made to discover ways in which Taiwanese and Chinese architectural culture can deal with foreign influences, such that it will be able to enjoy the benefits of modernization while maintaining its unique character and identity. Moreover, it will attempt to uncover ways in which Chinese architecture can in fact influence the global contemporary architectural culture. Finally, it is hoped that this work will produce a useful reference for students, scholars and architects who wish to develop design projects that reflect and celebrate regional cultures.
Ph. D.

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APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Recent experimental work on harmonic modelocking shows constraints on temporal spacing and frequency spectra can produce highly uniform trains of solitons. In addition, recent numerical simulation and analytical work predict: (1) solitons on the separate cores of dual core fiber can exhibit both repulsive and attractive interactions, and (2) individual solitons, satisfying certain threshold conditions, can propagate primarily on one core of dual core fiber despite significant coupling between guides. We use numerical simulation and analytical techniques to study the consequences of these findings for simple soliton arrays propagating in dual guide structures. In particular, we examine the case where strong constraints are imposed on the temporal spacing, amplitude, and frequency spectra of solitons in a given core, but weaker, or no constraints are imposed on solitons in the adjacent core. We find conditions, e.g., where a uniform train of solitons propagates primarily in the core where the strong constraints are imposed. We also find interesting dynamics for a “free” soliton in the second core that result from the interaction of the “free” soliton with the periodic potential produced by presence of the uniform soliton train on the first core. We examine routes to stability of this coupled system.

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Abstract:

The paper presents results of finite element analysis of architectured iron-based shape memory alloy (SMA) samples consisting of bulk SMA and void combined to different proportions and according to different geometric patterns. The finite element simulation uses a constitutive model for iron-based SMAs that was recently developed by the authors in order to account for the behavior of the bulk material. The simulation of the architectured SMA is then carried out using a unit cell method to simplify calculations and reduce computation time. For each unit cell, periodic boundary conditions are assumed and enforced. The validity of this assumption is demonstrated by comparing the average behavior of one unit cell to that of a considerably larger sample comprising multiple such cells. The averaging procedure used is implemented numerically, by calculating volume averages of mechanical fields such as stress and strain over each finite element model considered as a combination of mesh elements.

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APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This paper presents an optimization method for optimally distributing short fibers of variable length for the reinforcement of structural components for stiffness. Unlike standard density-based and level set topology optimization methods that generally render material distributions with variable member size, the proposed method projects an explicit geometry model onto a continuous density field. The proposed method inherits the benefits of density-based topology optimization methods, namely simplified and efficient primal and sensitivity analyses on a fixed grid, fast convergence, robustness, and amenability to standard finite element methods for the analysis and to nonlinear programming algorithms for the optimization. The explicit geometry representation of the fibers provides a suitable description of the short fibers, and therefore the designs produced by the proposed method have potential for manufacturing using, for example, processing methods for the fabrication of micro-architectured materials. Examples of reinforcement distribution design for two-dimensional structures in plane stress demonstrate the method.

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Abstract:

Architectural smells are decisions made at the software architecture level, whether intentional or not, that may negatively impact the quality of a software system. In the literature, architectural smells are identified mainly by relying on the source code or other implementation artifacts. However, architectural smells could be detected at design time, even before employing implementation efforts and preventing them from being reflected at the system implementation. This research investigates how software architecture descriptions realized through architecture description languages (ADLs) can be used to identify architectural smells at design time. This work focuses on how architectural smells manifest and can be detected in SysADL, an ADL that allows describing both structure and behavior of software architectures using standardized diagrams from the OMG’s SysML language.

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Abstract:

Vernacular architecture is identified as a structure based on specific local needs, on the presence of building materials present in the place and on the extemporaneousness of the architecture, built according to structural dogmas based on the local construction tradition. This is confirmed by the etymology of the word ‘vernacular’, from the Latin “vernaculus”, meaning "indigenous, domestic", or from “verna”, that is "native slave". In the present, vernacular architecture takes on new meanings, often used as an identifier for popular architecture - as also stated by Allen Noble in "Traditional Buildings: A global Survey of Structural Forms and Cultural Functions" of 2007 - or rather structures belonging to common people but «That can be built by skilled professionals, using local and traditional designs and materials», which is also supported by the Oxford English Dictionary. It is in this context that the vernacular Aeolian architecture fits, which significantly and identically characterize the entire territory of the Aeolian Islands, awarded the title of World Heritage Site by UNESCO. Aeolian architecture is inextricably linked to the history of the invasions of different peoples that have taken place in this area, such as the Greek-Roman, Islamic and finally Campania influences, due to their modifications both from an urbanistic and compositional point of view. But today how is it possible to encourage the dissemination and knowledge of these architectures which are so identifying for the Sicilian territory? Cataloging and semantics are configured as fundamental actions for the analysis and use of the architectural heritage, broken down into its deepest formal and compositional characteristics, identifiable in Aeolian architecture through the identification of semantics with a peculiar nomenclature. This article therefore investigates the aspects of semantics applied to traditional language and the compositional characteristics of Aeolian architecture, treated as an indissoluble link of knowledge and analysis of the building, through possible uses of digital applications.

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Abstract:

In 1963, Robin Boyd wrote about a post-war “rapprôchement” between the disciplines of structural engineering and architecture. Etymologically, the term suggests the movement of two entities that draw closer to each other, either in an unprecedented fashion or resuming a suspended interaction. World War II and the “anxieties and stimulations” of the post-war period, to use Boyd’s expression, accelerated the process of overcoming longstanding educational and professional disciplinary barriers. They were the driving forces behind what he denominated the “great structural-functional idea” of the 1950s. Architecture schools embraced modernist/functionalist ideals, producing graduates with considerable technical knowledge - true “romantic engineers.” The global post-war fascination with unconventional structures played its part. Occasionally, Antoine Picon argues, architecture’s “symbolic and aesthetic discourses” walk a “strictly technical path.” Under the banner of Le Corbusier’s Esthétique de l’Ingénieur, architecture and engineering converged. New technologies made collaborations with engineers habitual. According to Andrew Saint, however, partnerships were rarely affairs of equals since “architectural jobs came to architects first.” The diversification and growing number of engineers also transformed them into a labour force, Picon suggests, affecting their prestige and, possibly, their historiographical fortune. Scholarship on post-war Melbourne architecture has generally privileged the architect as the protagonist in the creation of innovative structures, only occasionally acknowledging consultants. This does not reflect the concerted nature of design commissions and frequent evanescence of disciplinary boundaries. This paper aims to highlight the major playing grounds for this alignment within design professions. It also hints at the complex relationship between the contributions of Victorian engineers and their recognition by post-war newspapers and architectural journals, opening the analysis of Melbourne’s post-war architecture to the discourse of professional representation and arguing the importance of “unbiased” histories of the built environment.

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Abstract:

The complexity of today’s highly engineered products is rooted in the interwoven architecture defined by its components and their interactions. Such structures can be viewed as the adjacency matrix of the associated dependency network representing the product architecture. To evaluate a complex system or to compare it to other systems, numerical assessment of its structural complexity is essential. In this paper, we develop a quantitative measure for structural complexity and apply the same to real-world engineered systems like gas turbine engines. It is observed that low topological complexity implies centralized architectures and that higher levels of complexity generally indicate highly distributed architectures. We posit that the development cost varies non-linearly with structural complexity. Empirical evidence of such behavior is presented from the literature and preliminary results from simple experiments involving assembly of simple structures further strengthens our hypothesis. We demonstrate that structural complexity and modularity are not necessarily negatively correlated using a simple example. We further discuss distribution of complexity across the system architecture and its strategic implications for system development efforts.

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Abstract:

Periodic cellular (lattice) materials, by virtue of their periodic structures and associated geometric impedance mismatch, exhibit wave dispersion, frequency dependent transmissibility, and directional characteristics that are inherently dependent on their constituent material and mesoscale microstructural features. These characteristics render lattice materials as potential candidates to perform as low frequency phononic crystals and metamaterials for radar, sonar, wave guiding, wave modulation and isolation applications. Accelerating the wide-spread implementation of lattice materials as phononic crystals hinges on establishing the ability to engineer them to exhibit application-tailored properties and tunable behavior (e.g. to activate/deactivate band gaps). Achieving tunability and application-oriented tailorablity requires, first, establishing an understating of phononic, acoustic, wave dispersion and directional properties of the lattices and how they are affected by lattices’ inherent features. Accordingly, using Bloch’s theorem in conjunction with finite element analysis, this work investigates the relationships between inherent microstructural features (such as lattice symmetry, relative density (i.e. volume fraction) and constituent material) and the acoustic properties (such as wave dispersion, band gaps, and acoustic anisotropy) of architectured lattice materials. The coupling between microstructural features and band gaps is investigated in a hexagonal lattice geometry which is inspired by the two dimensional Bravais family of lattices. Results illustrate that band structure and phononic properties are highly sensitive to relative density and can scale non-uniformly with it as eigenmodes are associated with relative density dependent deformation mechanisms. Moreover, results show that band gaps can potentially be activated and deactivated using macroscopic strain fields. The latter opens horizons for realizing cellular based phononic crystals with tunable properties.

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APA, Harvard, Vancouver, ISO, and other styles

Abstract:

As an emerging field, Automated Machine Learning (AutoML) aims to reduce or eliminate manual operations that require expertise in machine learning. In this paper, a graph-based architecture is employed to represent flexible combinations of ML models, which provides a large searching space compared to tree-based and stacking-based architectures. Based on this, an evolutionary algorithm is proposed to search for the best architecture, where the mutation and heredity operators are the key for architecture evolution. With Bayesian hyper-parameter optimization, the proposed approach can automate the workflow of machine learning. On the PMLB dataset, the proposed approach shows the state-of-the-art performance compared with TPOT, Autostacker, and auto-sklearn. Some of the optimized models are with complex structures which are difficult to obtain in manual design.

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Abstract:

West-central Yukon and eastern Alaska are characterized by widespread metamorphic rocks that form part of the allochthonous, composite Yukon-Tanana terrane and parautochthonous North American margin. Structural windows through the Yukon-Tanana terrane expose parautochthonous North American margin in that broad region, particularly as mid-Cretaceous extensional core complexes. Both the Yukon-Tanana terrane and parautochthonous North American margin share the same Late Devonian history, making their discrimination difficult; however, distinct post-Late Devonian magmatic and metamorphic histories assist in discriminating Yukon-Tanana terrane from parautochthonous North American margin rocks. The suture between Yukon-Tanana terrane and parautochthonous North American margin is obscured by many episodes of high-strain deformation. Their main bounding structure is probably a Jurassic to Cretaceous thrust, which has been locally reactivated as a mid-Cretaceous extensional shear zone. Crustal-scale structures within composite Yukon-Tanana terrane (e.g. the Yukon River shear zone) are commonly marked by discontinuous mafic-ultramafic complexes. Some of these complexes represent orogenic peridotites that were structurally exhumed into the Yukon-Tanana terrane in the Middle Permian.

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Abstract:

The US Congress codified the National Historic Preservation Act of 1966 (NHPA), through establishing the National Register of Historic Places (NRHP). The NHPA requires federal agencies to address their cultural resources, which are defined as any prehistoric or historic district, site, building, structure, or object. Section 110 of the NHPA requires federal agencies to inventory and evaluate their cultural resources, and Section 106 requires them to determine the effect of federal undertakings on those potentially eligible for the NRHP. Fort Gordon is located in northeast Georgia, directly west of Augusta-Richmond. It was first established as Camp Gordon during WWII for infantry and armor training. It has been known as Fort Gordon since 1956. This report provides historic context and recommends eligibility determinations for 24 buildings, structures, and landscapes associated with the Gordon Lakes Golf Club constructed between 1975 and 2009. The report recommends two Real Property landscapes (the Golf Driving Range and 18-Hole Golf Course including Gordon Lake) and one structure (Gordon Lake Dam) are eligible for the NRHP. The other 21 buildings and structures are recommended Not Eligible. Consulting with the Georgia State Historic Preservation Officer, this work fulfills Section 110 requirements for these buildings, structures, and landscapes.

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APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The Western Canada Sedimentary Basin (WCSB) is a mature oil and gas basin with an extraordinary endowment of publicly accessible data. It contains structural elements of varying age, expressed as folding, faulting, and fracturing, which provide a record of tectonic activity during basin evolution. Knowledge of the structural architecture of the basin is crucial to understand its tectonic evolution; it also provides essential input for a range of geoscientific studies, including hydrogeology, geomechanics, and seismic risk analysis. This study focuses on an area defined by the subsurface extent of the Triassic Montney Formation, a region of the WCSB straddling the border between Alberta and British Columbia, and covering an area of approximately 130,000 km2. In terms of regional structural elements, this area is roughly bisected by the east-west trending Dawson Creek Graben Complex (DCGC), which initially formed in the Late Carboniferous, and is bordered to the southwest by the Late Cretaceous - Paleocene Rocky Mountain thrust and fold belt (TFB). The structural geology of this region has been extensively studied, but structural elements compiled from previous studies exhibit inconsistencies arising from distinct subregions of investigation in previous studies, differences in the interpreted locations of faults, and inconsistent terminology. Moreover, in cases where faults are mapped based on unpublished proprietary data, many existing interpretations suffer from a lack of reproducibility. In this study, publicly accessible data - formation tops derived from well logs, LITHOPROBE seismic profiles and regional potential-field grids, are used to delineate regional structural elements. Where seismic profiles cross key structural features, these features are generally expressed as multi-stranded or en echelon faults and structurally-linked folds, rather than discrete faults. Furthermore, even in areas of relatively tight well control, individual fault structures cannot be discerned in a robust manner, because the spatial sampling is insufficient to resolve fault strands. We have therefore adopted a structural-corridor approach, where structural corridors are defined as laterally continuous trends, identified using geological trend surface analysis supported by geophysical data, that contain co-genetic faults and folds. Such structural trends have been documented in laboratory models of basem*nt-involved faults and some types of structural corridors have been described as flower structures. The distinction between discrete faults and structural corridors is particularly important for induced seismicity risk analysis, as the hazard posed by a single large structure differs from the hazard presented by a corridor of smaller pre-existing faults. We have implemented a workflow that uses trend surface analysis based on formation tops, with extensive quality control, combined with validation using available geophysical data. Seven formations are considered, from the Late Cretaceous Basal Fish Scale Zone (BFSZ) to the Wabamun Group. This approach helped to resolve the problem of limited spatial extent of available seismic data and provided a broader spatial coverage, enabling the investigation of structural trends throughout the entirety of the Montney play. In total, we identified 34 major structural corridors and number of smaller-scale structures, for which a GIS shapefile is included as a digital supplement to facilitate use of these features in other studies. Our study also outlines two buried regional foreland lobes of the Rocky Mountain TFB, both north and south of the DCGC.

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APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The need to conduct complex operations over time results in U.S. forces remaining in deployed locations for long periods. In such cases, more sustainable facilities are required to better accommodate and protect forward deployed forces. Current efforts to develop safer, more sustainable operating facilities for contingency bases involve construction activities that redesign the types and characteris-tics of the structures constructed, reduce the resources required to build, and reduce resources needed to operate and maintain the com-pleted facilities. The Automated Construction of Expeditionary Structures (ACES) project was undertaken to develop the capability to “print” custom-designed expeditionary structures on demand, in the field, using locally available materials with the minimum number of personnel. This work investigated large-scale automated “additive construction” (i.e., 3D printing with concrete) for construction applications. This document, which documents ACES energy and modeling, is one of four technical reports, each of which details a major area of the ACES research project, its research processes, and associated results, including: System Requirements, Construction, and Performance; Energy and Modeling; Materials and Testing; Architectural and Structural Analysis.

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Abstract:

The need to conduct complex operations over time results in U.S. forces remaining in deployed locations for long periods. In such cases, more sustainable facilities are required to better accommodate and protect forward deployed forces. Current efforts to develop safer, more sustainable operating facilities for contingency bases involve construction activities that redesign the types and characteris-tics of the structures constructed, reduce the resources required to build, and reduce resources needed to operate and maintain the com-pleted facilities. The Automated Construction of Expeditionary Structures (ACES) project was undertaken to develop the capability to “print” custom-designed expeditionary structures on demand, in the field, using locally available materials with the minimum number of personnel. This work investigated large-scale automated “additive construction” (i.e., 3D printing with concrete) for construction applications. This document, which documents ACES energy and modeling, is one of four technical reports, each of which details a major area of the ACES research project, its research processes, and associated results, including: System Requirements, Construction, and Performance; Energy and Modeling; Materials and Testing; Architectural and Structural Analysis.