Letteratura scientifica selezionata sul tema "Topology Tailoring"

In the paper, a lightweight design method for tailor-welded blanks (TWBs), termed as Topology Tailoring Method (TTM), is proposed, which is based on topology optimization philosophy and in which the variable density method is employed so as to reach the goal of the smallest structure strain energy. By using this method, a TWB autodoor subjected to a specific working condition is topologically optimized in HyperWorks, thus obtaining the more lightweight autodoor. At last, a side impact simulation of the autodoor is demonstrated, thus showing the effectiveness of the method.

Cellular Materials and Topology Optimization use a structured distribution of material to achieve specific mechanical properties. The controlled distribution of material often leads to several advantages including the customization of the resulting mechanical properties; this can be achieved following these two approaches. In this work, a review of these two as approaches used with compliance purposes applied at flexure level is presented. The related literature is assessed with the aim of clarifying how they can be used in tailoring stiffness of flexure elements. Basic concepts needed to understand the fundamental process of each approach are presented. Further, tailoring stiffness is described as an evolutionary process used in compliance applications. Additionally, works that used these approaches to tailor stiffness of flexure elements are described and categorized. Finally, concluding remarks and recommendations to further extend the study of these two approaches in tailoring the stiffness of flexure elements are discussed.

Parent nanoparticle networks containing trithiocarbonate photoactive groups form nanonetworks with incorporated homopolymers, random copolymers and block copolymers through a developed photogrowth expansion process.

La transition vers une économie neutre en carbone est confrontée à deux défis majeurs : le stockage de l'excès d'énergie provenant des énergies renouvelables et la décarbonation des processus de combustion dans les secteurs difficiles à électrifier. La stratégie Power to Gas (P2G) propose de résoudre ces problèmes en substituant partiellement l'hydrogène dans le réseau actuel de gaz naturel. Cependant, cela nécessite le développement de brûleurs flexibles capables de s'adapter à des niveaux variables d'hydrogène dans le réseau. Cela est compliqué à cause des différences entre les propriétés de la flamme d’hydrogène et celles des combustibles hydrocarbonés. Les brûleurs poreux (PMBs) sont considérés comme une technologie prometteuse en raison de leurs propriétés uniques. Les PMBs utilisent la recirculation de chaleur pour stabiliser les flammes à l'intérieur de matrices poreuses inertes, incrémentant le taux de consommation de la flamme et atteignant des températures locales superadiabatiques. Cela permet des densités de puissance plus élevées et l’extension des limites d'inflammabilité, ce qui se traduit par des dispositifs compacts et une faible émission de NOx avec des efficacités radiatives élevées.Le mécanisme fondamental de fonctionnement des brûleurs poreux à l'échelle macroscopique, la recirculation de la chaleur, est bien compris. Cependant, il existe encore une connaissance limitée sur certains phénomènes à l'échelle des pores et de leur influence sur le comportement du système global. En raison de la non-linéarité de la combustion et du transfert de chaleur, la stabilisation de la flamme et les performances du brûleur dépendent fortement des détails à l'échelle des pores. Les modèles de bas ordre actuels n'incluent pas la modélisation des interactions flamme-paroi et des effets de diffusion préférentielle, ce qui entraîne une faible précision. Les diagnostics non intrusifs avancés pourraient être utilisés pour étudier la structure locale de la flamme et guider l'amélioration des modèles de bas ordre. Cependant, les mesures expérimentales dans les PMBs sont entravées par le manque d'accès optique à l'intérieur de la matrice poreuse. Malgré les efforts récents, l'application de diagnostics optiques et non intrusifs dans les PMBs est encore très rare. Cette thèse présente une étude expérimentale sur la combustion en milieu poreux et est consacrée au développement de diagnostics optiques. Des PMBs optiquement accessibles sont produits en combinant des topologies définies par ordinateur avec des techniques de fabrication additive. La méthodologie actuelle offre un accès optique étendu dans une configuration de brûleur 3D sans perturber la structure de la matrice. L'accès optique est utilisé pour appliquer une série de diagnostics optiques, y compris la chimiluminescence CH*, l'imagerie de diffusion de Mie et la micro-PIV. Nos résultats montrent les limites des VAMs actuels et de leurs méthodes de validation. La mise en œuvre de diagnostics novateurs a également révélé différentes tendances de stabilisation dans les flammes enrichies en H2, soulignant l'effet des mécanismes d'ancrage local sur les limites de fonctionnement du brûleur. Enfin, l'accès optique est exploité pour effectuer des diagnostics laser et étudier la structure de la flamme à l'échelle des pores. Nos résultats révèlent différents modes de stabilisation et mettent en évidence l'impact de l’écoulement interstitiel sur les performances du brûleur. Cette thèse ouvre de nouvelles voies pour l'application de diagnostics non intrusifs et plaide pour un développement supplémentaire des techniques expérimentales avancées dans les brûleurs poreux
Porous Media Burners (PMBs) are a combustion technology based on heat recirculation where a flame is stabilized within the cavities of an inert porous matrix. In PMBs, heat is transferred upstream from the burned to the unburned gas through the solid matrix yielding a preheating of the reactants.This increases their burning rate allowing for more compact combustion devices and the operation beyond conventional flammability limits. As a result, the stabilization of flames at ultra-lean equivalence ratios is possible, with the subsequent reduction of the flame temperature and NOx emissions. In these burners, a substantial fraction of the power is radiated by the hot solid phase, with radiated power fractions ranging between 20-30 %. This, together with their elevated efficiency and low pollutant emissions, has motivated their commercial use in various infrared heating applications.In the past years, PMBs have received renewed interest owing to their potential as fuel flexible burners. Their ability to stabilize flames over a wide range of burning rates makes them promising candidates to handle the uneven flame properties of hydrogen and hydrocarbon fuels.The mechanism of heat recirculation in PMBs is well understood. However, there is still limited knowledge about many pore-scale phenomena that have a critical impact on the macroscopic behavior of the system and its performance.Advanced nonintrusive diagnostics could be used to study local flame stabilization mechanisms and improve current models. However, experimental measurements in PMBs are hindered by the lack of optical access to the interior of the porous matrix.This dissertation presents an experimental study on porous media combustion and is devoted to the application of optical diagnostics. Optically accessible PMBs are produced by combining computer-defined topologies with additive manufacturing techniques. This methodology provides an extensive optical access in a 3D burner configuration without altering the matrix structure. Optical access is leveraged to apply CH* chemiluminescence, Mie-scattering imaging and micro PIV. Topology tailoring is exploited to analyze the influence of the geometrical parameters of the porous matrix. Direct flame visualization enables the tracking of the reaction region as a function of the operating conditions, which can be used for model validation. The present results bring to light several limitations of current low order models and highlight the influence of the pore size on flame stabilization. Flame-front tracking is also used to investigate the effect of H2-enrichment on the behavior of the flame. This technique reveals different stabilization trends in H2-enriched flames that are not well retrieved by current models. Mie-scattering permits the quantification of the re-equilibration distance and the analysis of the flame shape. Micro PIV measurements show the influence of the topology on the interstitial flow and on the contribution of hydrodynamic effects to flame stabilization.This PhD seeks to open new paths for the application of non-intrusive diagnostics in PMBs and to improve the current understanding of flame stabilization mechanisms

The advent of mobile computing offloading paradigms, such mobile-edge computing (MEC), has allowed several internet of things (IoT) applications to use end devices' processing capabilities to do local tasks independently of a centralized server. A practical method for extending the amount of duration needed to finish computing tasks is computation off-load. This in-depth study investigates the complicated world of IoT systems, MEC paradigms, and the supplementary advantages gained by properly coordinating processing phases and compute modes. End-device execution is better for some application tasks due to reduced processing and greater connection expenses. In contrast, the MEC topology extends cloud capabilities to the network edge to speed up data processing near mobile devices. Symmetric propagation is the strategy the authors use in the cloud computing layer to shorten the time it takes for data to go from edge devices to cloud servers. In conclusion, they address computation latency in the cloud computing layer by tailoring our approach to its unique properties.

The freedom of design that is afforded by Additive Manufacturing (AM) processes opens exciting possibilities for the production of lightweight, high performance components and structures. Consequently, in recent years the development of software tools to enable engineering design methods that exploit the unique features of AM has become a subject of increased research interest. In this paper we explore the use of Topology Optimization (TO) algorithms to tailor component shape in order to achieve the intended functionality of additively manufactured components at the macro length scale. We present two case studies: the first concerns the hierarchical nesting of functions in a hand tool, while the second covers the development of a metamaterial component substructure for an Uninhabited Underwater Vehicle (UUV) hull. We offer conclusions regarding the usefulness of TO techniques for the design of AM components, and a summary of future work, which we feel is necessary to improve such methodologies.

Prismatic cellular or honeycomb materials exhibit favorable properties for multifunctional applications such as ultra-light load bearing combined with active cooling. Since these properties are strongly dependent on the underlying cellular structure, design methods are needed for tailoring cellular topologies with customized multifunctional properties that may be unattainable with standard cell designs. Topology optimization methods are available for synthesizing the form of a cellular structure—including the size, shape, and connectivity of cell walls and the number, shape, and arrangement of cell openings—rather than specifying these features a priori. To date, the application of these methods for cellular materials design has been limited primarily to elastic and thermo-elastic properties, however, and limitations of standard topology optimization methods prevent direct application to many other phenomena such as conjugate heat transfer with internal convection. In this paper, we introduce a practical, two-stage, flexibility-based, multifunctional topology design approach for applications that require customized multifunctional properties. As part of the approach, robust topology design methods are used to design flexible cellular topology with customized structural properties. Dimensional and topological flexibility is embodied in the form of robust ranges of cell wall dimensions and robust permutations of a nominal cellular topology. The flexibility is used to improve the heat transfer characteristics of the design via addition/removal of cell walls and adjustment of cellular dimensions, respectively, without degrading structural performance. We apply the method to design stiff, actively cooled prismatic cellular materials for the combustor liners of next-generation gas turbine engines.

The spatial distribution of material phases within a periodic composite can be engineered to produce band gaps in its frequency spectrum. Applications for such composite materials include vibration and sound isolation. Previous research focused on utilizing topology optimization techniques to design two-dimensional periodic materials with a maximized band gap around a particular frequency or between two particular dispersion branches. While sizable band gaps can be realized, the possibility remains that the frequency bandwidth of the load that is to be isolated might significantly exceed the size of the band gap. In this paper, genetic algorithms are used to design squared bi-material unit cells with a maximized sum of relative band-gap widths over a prescribed frequency range of interest. The optimized unit cells therefore exhibit broadband frequency isolation characteristics. The effects of the ratios of contrasting material properties are also studied. The designed cells are subsequently used, with varying levels of material damping, to form a finite vibration isolation structure, which is subjected to broadband loading conditions. Excellent isolation properties of the synthesized material are demonstrated for this structure.

We describe and demonstrate a computational approach to analyze and design piezoelectric energy harvesting systems composed of layered plate and shell-like structures with an external harvesting circuit. We model the coupled dynamic electromechanics of a piezoelectric harvester as well as the dynamics of an electrical circuit that is connected to the harvester with the finite element method. We assume the harvester is subjected to a prescribed harmonic excitation that may have broadband frequency content. Our design approach uses topology optimization to optimally design a piezoelectric harvester by tailoring the layout of a multilayer structure consisting of structural layers, piezoelectric layers, electrodes, as well as the electrical circuit parameters. We admit the spatially tailoring of these items both in the plane and through the thickness of the multilayer plate and shell. After a description of our analysis and design approaches, we present a number of examples that demonstrate some of the capabilities of our approach and show how it can be used to explore general behavior and develop overarching principles through the study of a suite of particular problems.

High-modulus (HM) carbon fiber-reinforced polymers (CFRPs) have attracted strong demand by the rotorcraft industry as such materials can potentially enable lightweight airframes and rotor components with significant weight savings. However, low fiber-direction compressive strength, compared to intermediate-modulus (IM) CFRPs currently used in primary structures, has been a well-recognized weakness of HM CFRPs, prohibiting their implementation in rotorcraft platforms. Microstructural tailoring provides an innovative means for breaking through the fiber-direction compressive strength barrier of the HM CFRPs. Microbuckling, the fiber-direction compressive failure mechanism of the subject HM and IM CFRPs, is driven by fiber-matrix interface shear strength. Assessment of the interface properties using in-situ SEM-based experiments reveal substantial difference in surface topology between IM and HM fibers, which is related to higher interface strength in HM fibers. This instigates a microstructural tailoring approach of reinforcing material surrounding HM fibers with IM fibers to improve microstructural stability. A manufacturing system has been developed, and promising results enabling HM CFRPs with adequate fiber-direction compressive strength have been achieved through hybridization of IM and HM fibers at the filament level in HM CFRP toughened with nano-silica. A new material achieving compressive strength of IM CFRPs but with >30% higher modulus has been developed.

A paradigm shift is underway in which the classical materials selection approach in engineering design is being replaced by the design of material structure and processing paths on a hierarchy of length scales for multifunctional performance requirements. In this paper, the focus is on designing mesoscopic material topology—the spatial arrangement of solid phases and voids on length scales larger than microstructures but smaller than the characteristic dimensions of an overall product. A robust topology design method is presented for designing materials on mesoscopic scales by topologically and parametrically tailoring them to achieve properties that are superior to those of standard or heuristic designs, customized for large-scale applications, and less sensitive to imperfections in the material. Imperfections are observed regularly in cellular material mesostructure and other classes of materials because of the stochastic nature of process-structure-property relationships. The robust topology design method allows us to consider imperfections explicitly in a materials design process. As part of the method, guidelines are established for modeling dimensional and topological imperfections, such as tolerances and cracked cell walls, as deviations from intended material structure. Also, as part of the method, robust topology design problems are formulated as compromise Decision Support Problems, and local Taylor-series approximations and strategic experimentation techniques are established for evaluating the impact of dimensional and topological imperfections, respectively, on material properties. Key aspects of the approach are demonstrated by designing ordered, prismatic cellular materials with customized elastic properties that are robust to dimensional tolerances and topological imperfections.

Abstract This paper will investigate the effects of pennate angle on fluidic artificial muscle (FAM) bundles for a robot arm motion. Rising interest in soft fluidic actuators exists due to their prospective inherent compliance and safe human-robot interaction. The high force-to-weight ratio, innate flexibility, inexpensive construction, and muscle-like force-contraction behavior of McKibben FAMs make them an attractive type of soft fluidic actuator. Multi-unit architectures found in biological muscles tissues and geometric fiber arrangements have inspired the development of hierarchical actuators to enhance the total actuator performance and increase actuator functionality. Parallel, asymmetric unipennate, and symmetric bipennate are three muscle fiber arrangement types found in human skeletal muscle tissues. Unique characteristics of the pennate muscle tissue, with muscle fibers arranged obliquely from the line of muscle motion, enable passive regulation of effective transmission between the fibers and muscle. Prior studies developed an analytical model based on idealized assumptions to leverage this pennate topology in optimal fiber parameter design for FAM bundles under spatial bounds. The findings showed FAMs in the bipennate topology can be designed to amplify the muscle output force, contraction, and stiffness as compared to that of a parallel topology under equivalent spatial and operating constraints. This work seeks to extend upon previous studies by investigating the effects of pennate angle on actuation and system hydraulic efficiency for a robot arm with a more realistic FAM model. The results will progress toward tailoring actuator topology designs for custom compliant actuation applications.

Abstract Ferromagnetic soft materials can generate flexible mobility and changeable configurations under an external magnetic field. They are used in a wide variety of applications, such as soft robots, compliant actuators, flexible electronics, and bionic medical devices. The magnetic field enables fast and biologically safe remote control of the ferromagnetic soft material. The shape changes of ferromagnetic soft elastomers are driven by the ferromagnetic particles embedded in the matrix of a soft elastomer. The external magnetic field induces a magnetic torque on the magnetized soft material, causing it to deform. To achieve the desired motion, the soft active structure can be designed by tailoring the layouts of the ferromagnetic soft elastomers. This paper aims to optimize multi-material ferromagnetic actuators. Multi-material ferromagnetic flexible actuators are optimized for the desired kinematic performance using the reconciled level set method. This type of magnetically driven actuator can carry out more complex shape transformations by introducing ferromagnetic soft materials with more than one magnetization direction. Whereas many soft active actuators exist in the form of thin shells, the newly proposed extended level set method (X-LSM) is employed to perform conformal topology optimization of ferromagnetic soft actuators on the manifolds. The objective function comprises two sub-objective functions, one for the kinematic requirement and the other for minimal compliance. Shape sensitivity analysis is derived using the material time derivative and the adjoint variable method. Three examples are provided to demonstrate the effectiveness of the proposed framework.

Wave propagation inside a host media with periodically distributed inclusions can exhibit bandgaps. While controlling acoustic wave propagation has large impact on many engineering applications, studies on broadband acoustic bandgap (ABG) adaptation is still outstanding. One of the important properties of periodic structure in ABG design is the lattice-type. It is possible that by reconfiguring the periodic architectures between different lattice-types with fundamentally distinct dispersion relations, we may achieve broadband wave propagation tuning. In this spirit, this research pioneers a new class of reconfigurable periodic structures called origami metastructures (OM) that can achieve ABG adaption via topology reconfiguration by rigid-folding. It is found that origami folding, which can enable significant and precise topology reconfigurations between distinct Bravais lattice-types in underlying periodic architecture, can bring about drastic changes in wave propagation behavior. Such versatile wave transmission control is demonstrated via numerical studies that couple wave propagation theory with origami folding kinematics. Further, we also exploit the novel ABG adaptation feature of OM to design structures that can exhibit unique tunable non-reciprocal behavior. Overall the broadband adaptable wave characteristics of the OM coupled with scale independent rigid-folding mechanism can bring on-demand wave tailoring to a new level.