The increased quality and quantity of sensors provide an ever-increasing capability to collect large quantities of high-quality data in the field. Research devoted to translating that data is progressing rapidly; however, translating field data into usable information can require high performance computing capabilities. While high performance computing (HPC) resources are available in centralized facilities, bandwidth, latency, security and other limitations inherent to edge location in field sensor applications may prevent HPC resources from being used in a timely fashion necessary for potential United States Army Corps of Engineers (USACE) field applications. To address these limitations, the design requirements for RECON are established and derived from a review of edge computing, in order to develop and evaluate a novel high-power, field-deployable HPC platform capable of operating in austere environments at the edge.

With the help of sounding rockets, the Earth’sionosphere can be studied by ejecting cylindrical units thatmeasure various electromagnetic properties while falling. Theseunits are also known as Free Falling Units (FFUs). The goal of thisproject is to turn the FFUs into autonomous gliders by designingdeployable wings. A spring-loaded Scissor Structural Mechanism(SSM) was chosen as the main deploying mechanism. Furthermore,the conceptual wing design was simulated in Siemens NXand a structural analysis was performed in NASTRAN. Finally, aprototype was manufactured to confirm if the SSM would workas intended. Initial simulation results showed great promise withthe proper choice of materials. Due to resource limitations, theprototype could not be compared to the simulation. Based onthe prototype results, the design must be reinforced or alteredto become stronger and more rigid. / Med hjälp av sondraketer kan jordensjonosfär studeras genom att skicka ut cylindriska enhetersom mäter diverse elektromagnetiska egenskaper medan defaller. Dessa enheter är också kända som FFUs (Free FallingUnits). Målet med detta projekt var att förvandla dessa enhetertill autonoma glidare genom att designa utfällbara vingar.En fjäderbelastad saxmekanism valdes som den huvudsakligautfällningsmekanismen. Vidare simulerades den konceptuellavingdesignen i Siemens NX och strukturen analyserades i NASTRAN.Slutligen tillverkades en prototyp för att bekräfta omsaxmekanismen skulle fungera som avsedd. De första simuleringsresultatenvisade sig vara lovande med rätt materialval.På grund av begränsningar i resurser, kunde inte prototypenjämföras med simuleringen. Baserat på prototypresultaten måstedesignen förstärkas eller ändras för att bli starkare och mer styv. / Kandidatexjobb i elektroteknik 2021, KTH, Stockholm

In this dissertation, we explore the possibilities of systematically constructing large structural mechanisms using existing spatial overconstrained linkages with only revolute joints as basic elements. The first part of the dissertation is devoted to structural mechanisms (networks) based on the Bennett linkage, a well-known spatial 4R linkage. This special linkage has been used as the basic element. A particular layout of the structures has been identified allowing unlimited extension of the network by repeating elements. As a result, a family of structural mechanisms has been found which form single-layer structural mechanisms. In general, these structures deploy into profiles of cylindrical surface. Meanwhile, two special cases of the single-layer structures have been extended to form multi-layer structures. In addition, according to the mathematical derivation, the problem of connecting two similar Bennett linkages into a mobile structure, which other researchers were unable to solve, has also been solved. A study into the existence of alternative forms of the Bennett linkage has also been done. The condition for the alternative forms to achieve the compact folding and maximum expansion has been derived. This work has resulted in the creation of the most effective deployable element based on the Bennett linkage. A simple method to build the Bennett linkage in its alternative form has been introduced and verified. The corresponding networks have been obtained following the similar layout of the original Bennett linkage. The second effort has been made to construct large overconstrained structural mechanisms using hybrid Bricard linkages as basic elements. The hybrid Bricard linkage is a special case of the Bricard linkage, which is overconstrained and with a single degree of mobility. Starting with the derivation of the compatibility condition and the study of its deployment behaviour, it has been found that for some particular twists, the hybrid Bricard linkage can be folded completely into a bundle and deployed to a flat triangular profile. Based on this linkage, a network of hybrid Bricard linkages has been produced. Furthermore, in-depth research into the deployment characteristics, including kinematic bifurcation and the alternative forms of the hybrid Bricard linkage, has also been conducted. The final part of the dissertation is a study into tiling techniques in order to develop a systematic approach for determining the layout of mobile assemblies. A general approach to constructing large structural mechanisms has been proposed, which can be divided into three steps: selection of suitable tilings, construction of overconstrained units and validation of compatibility. This approach has been successfully applied to the construction of the structural mechanisms based on Bennett linkages and hybrid Bricard linkages. Several possible configurations are discussed including those described previously. All of the novel structural mechanisms presented in this dissertation contain only revolute joints, have a single degree of mobility and are geometrically overconstrained. Research work reported in this dissertation could lead to substantial advancement in building large spatial deployable structures.

Les mètres rubans sont utilisés comme dispositif de déploiement car ils sont légers, compacts, se déploient de manière autonome et ont une capacité d'auto-blocage en position déployée. Ces structures élancées de forme cylindrique présentent un comportement complexe avec formation de plis localisés. Leur modélisation est donc difficile : bien que des modèles de poutre à section flexible (RFleXS) aient été développés. Les travaux réalisés consistent à développer des outils numériques d'aide au dimensionnement de structures déployées par des rubans. Un modèle RFleXS adimensionné dédié aux rubans peu profonds est introduit et analysé, mettant en évidence des liens avec le modèle de barre d'Ericksen régularisé. Ces liens expliquent la formation de plis et caractérisent les trois zones constitutives d'un pli. On détermine de façon analytique le nombre et la position des points de bifurcation des branches de solution obtenues pour un essai de flexion pure d'un ruban. Un enrichissement de la cinématique de section est intégré dans les modèles RFleXS. Les simulations de flexion de ruban montrent alors une bonne corrélation avec les modèles de coque. Une nouvelle formulation des modèles RFleXS est implémentée et conduisant au développement de deux outils numériques : un code de calcul par éléments finis complet et un élément à deux noeuds intégré dans un code commercial. Des essais de flexion réalisés sur des rubans composites viennent compléter ces travaux afin de confronter les simulations numériques à des essais réels. Bien que des écarts soient observés, le comportement global du ruban est bien retranscrit par les modèles de poutre à section flexible. / Due to their lightness, compactness, their autonomous deployment and their ability to self-locking while deployed, tape-springs are considered to deploy structures. These slender and cylindrical structures highlight a complex behaviour because of the formation of localised folds. Tape-springs are then difficult to model but a rod model with flexible cross-section (RFleXS) has been developed in order to characterise the tape-spring behaviour.The purpose of this PhD was to develop numerical tools dedicated to design structures deployed by tape-spings. A dimensionless form of the RFleXS model dedicated to shallow tape spring has been developed and links with a regularised Ericksen's bar have been made. These links help to explain folds creation and to determine characteristics of the three constitutive areas of a fold. Analysis of the dimensionless model leads to determine the finite number and the position of bifurcation points for the pure bending of a tape-spring. The cross-section kinematic is enriched; simulations of bending tests then show a good correlation with shell models. A new implementation of RFleXS models is introduced, leading to the creation of two numerical tools: a full finite element software and a one-dimensional element with two nodes incorporated in Abaqus. Some bending experiments have been performed in order to compare simulations with measured data. Even if discrepancies are observed, these comparisons show that the tape-spring overall behaviour is well predicted by rod models with flexible cross-section.

The use of small satellites is rapidly growing, especially satellites with masses between 1 and 10 kg and few litres of volume. The main reasons are due to the low development time and cost. Electronics miniaturization and high density integration is enabling the small satellites class to perform more and better tasks and at a lower cost. When deployable structures are required for the missions, the actual paradigm is that there are very few that have been successfully developed and flown. It is usually not possible to scale down existing deployable structures from larger satellites. Power and attitude control is also very limited in small satellites thus, completely new deployable structures, low mass and with high packaging ratio (yet large and with adequate mechanical properties when deployed) must be developed. Furthermore, such new structures are usually made of very thin and light materials which complicates the on-ground tests prior the launch. Therefore, advances in modelling and simulation deployable structures such as booms are also of great interest for the scientific community. This thesis and the papers included herein focus on the finite element modelling of a meter-class passively deployable boom – based on the SIMPLE boom by Thomas W. Murphey – and deployment simulations. Experimental tests were also carried on a boom prototype suspended from a gravity off-loading system. An analytical model produced certain parameters which are used for validation of the finite element model. The strain energy stored in the boom prior to deployment and spacecraft displacements during deployment agreed well. The deployment time, however, have discrepancies: the models predicted a deployment time six times faster than the experimental tests. For that reason the deployment simulations cannot be compared with the tests. The reason of the discrepancies are believed to be due to the actual material model and the contacts formulation used in the finite element model. The finite element simulations, however, shows a reasonable behaviour given the nature of the deployment thus, despite the necessary improvements, we believe that future improvements in the material and friction models will provide us more realistic results. / Användningen av små satelliter ökar snabbt, särskilt satelliter med en vikt på mellan 1 och 10 kg och bara några liters volym. De främsta orsakerna till detta är den korta utvecklingstiden och den låga kostnaden. Elektronikminiatyrisering och hög integreringsdensitet möjliggör för små satelliter att utföra fler och bättre uppgifter till en lägre kostnad. När utfällbara strukturer krävs för uppdragen är nuvarande läge att det är få som utvecklats och flugits framgångsrikt. Det är inte heller alltid möjligt att skala ner utfällbara strukturer som utformats för användning i större satelliter. I små satelliter är den tillgängliga elektriska energin och volymen starkt begränsade faktorer och därmed måste helt nya passivt utfällbara strukturer med låg vikt och liten packningsvolym, men ändå rätt storlek och mekaniska egenskaper när de är utfällda, utvecklas. Dessa strukturer är vanligen tillverkade av mycket tunna och lätta material, som komplicerar tester innan uppskjutningen p.g.a. tyngdkraften. Därför är det av stort intresse att noggrant kunna modellera och simulera ett tyngdlöst utfällningsförlopp. Denna licentiatuppsats och bilagda artiklar i fokuserar på finit elementmodellering och utfällningssimuleringar av en 1 meter lång passivt utfällbar bom baserad på SIMPLE-bommen som utformats av Thomas W. Murphey. Utfällningsexperiment har utförts på en prototyp av bommen upphängd i ett tyngdkraftskompenserande system. Analytiska modeller har använts för att validera simuleringarna och töjningsenergin som lagrats i bommen innan utfällning och rymdfarkostens förflyttning efter utfällning överensstämmer väl. Utfällningstiden avviker dock och båda modellerna predikterar en utfällningstid som är sex gånger snabbare än den tiden som observeras i experimenten. Anledningen till skillnaderna antas delvis bero på begränsningar i den använda materialmodellen och i algoritmer för hantering av kontakt i den finita elementmodellen. De finite elementsimuleringarna visar dock ett rimligt dynamisk beteende hos bommen baserat på vad som observerats i experimenten och även om modellen är i behov av förbättring så finns det stora förhoppningar att åstadkomma en mer realistisk modell genom införande av förbättrade kontakalgoritmer och nogrannare modellering av dämpning och friktion. / <p>QC 20130506</p>

<p>Composite materials have been invented and used to make all kinds of industrial products, such as automobiles, aircraft, sports equipment etc., for many years. Excellent properties such as high specific stiffness and strength have been recognized and studied for decades, motivating the use of composite materials. However, the design of composite structures still remains a challenge. Existing design tools are not adequate to exploit the full benefits of composites. Many tools are still based on the traditional material selection paradigm created for isotropic homogeneous materials, separated from the shape design. This will lose the coupling effects between composite materials and the geometry and lead to less optimum design of the structure. Hence, due to heterogeneity and anisotropy inherent in composites, it is necessary to model composite parts with appropriate microstructures  instead of simplistically replacing composites as black aluminum and consider materials and geometry at the same time.</p> <p><br></p> <p>This work mainly focuses on the design problems of complex material-structural systems through computational analyses. Complex material-structural systems are structures made of materials that have microstructures smaller than the overall structural dimension but still obeying the continuum assumption, such as fiber reinforced laminates, sandwich structures, and meta-materials, to name a few. This work aims to propose a new design-by-analysis framework based on the mechanics of structure genome (MSG), because of its capability in accurate and efficient predictions of effective properties  for different solid/structural models and three-dimensional local fields (stresses, strains, failure status, etc). The main task is to implement the proposed framework by developing new tools and integrating these tools into a complete design toolkit. The main contribution of this work is a new efficient high-fidelity design-by-analysis framework for complex material-structural systems.</p> <p><br></p> <p>The proposed design framework contains the following components. 1) MSG and its companion code SwiftComp is the theoretical foundation for structural analysis in this design framework. This is used to model the complex details of the composite structures. This approach provides engineers the flexibility to use different multiscale modeling strategies. 2) Structure Gene (SG) builder creates finite element-based model inputs for SwiftComp using design parameters defining the structure. This helps designers deal with realistic and meaningful engineering parameters directly without expert knowledge of finite element analysis. 3) Interface is developed using Python for easy access to needed data such as structural properties and failure status. This is used as the integrator linking all components and/or other tools outside this framework. 4) Design optimization methods and iteration controller are used for conducting the actual design studies such as parametric study, optimization, surrogate modeling, and uncertainty quantification. This is achieved by integrating Dakota into this framework. 5) Structural analysis tool is used for  computing global structural responses. This is used if an integrated MSG-based global analysis process is needed.</p> <p><br></p> <p>Several realistic design problems of composite structures are used to demonstrate the capabilities of the proposed framework. Parameter study of a simple fiber reinforce laminated structure is carried out for investigating the following: comparing with traditional design-by-analysis approaches, whether the new approach can bring new understandings on parameter-response relations and because of new parameterization methods and more accurate analysis results. A realistic helicopter rotor blade is used to demonstrate the optimization capability of this framework. The geometry and material of composite rotor blades are optimized to reach desired structural performance. The rotor blade is also used to show the capability of strength-based design using surrogate models of sectional failure criteria. A thin-walled composite shell structure is used to demonstrate the capability of designing variable stiffness structures by steering in-plane orientations of fibers of the laminate. Finally, the tool is used to study and design auxetic laminated composite materials which have negative Poisson's ratios.</p>

No description available.

[pt] Estruturas reticuladas espaciais com grandes vãos são encontradas em uma variedade de aplicações em engenharia. Muitas dessas estruturas apresentam um comportamento eminentemente não linear, envolvendo tanto não linearidades físicas quanto geométricas, o que leva em muitos casos a múltiplas configurações de equilíbrio. Em particular, estruturas biestáveis estão usualmente sujeitas a instabilidades por ponto limite (snap-through), bifurcações simétrica instável ao longo do caminho não linear de equilíbrio, instabilidade elástica de elementos individuais, devido à plastificação destes elementos ou a interação destes fenômenos. O presente trabalho tem como objetivo a análise detalhada de duas classes de estruturas biestáveis: treliças piramidais (instabilidade indesejada) e estruturas ajustáveis com elementos de tesoura (instabilidade desejada). Ferramentas teóricas e computacionais são desenvolvidas para a investigação da influência das medidas de deformação quadrática e logarítmica, deformações elasto-plásticas e instabilidades na resposta estática e dinâmica não linear de um módulo de treliça piramidal. Uma formulação corrotacional em elementos finitos é proposta para descrever a ligação espacial flexível encontrada nas estruturas ajustáveis biestáveis aqui estudadas. A análise de estruturas com grandes vãos formadas pela junção de módulos de treliças piramidais ou módulos ajustáveis é apresentada. Os resultados obtidos mostram que a presença e interação das diversas fontes de instabilidade têm uma grande influência no comportamento destas estruturas e pode determinar ou não a sua viabilidade em aplicações práticas. / [en] Large span reticulated structures are applied in a variety of engineering applications. Many of these structures present a nonlinear behavior involving both geometric and material nonlinearities with multistable configurations. Particularly, bistable structures are often subjected to instability phenomena, such as snap-through and bifurcations of the whole structure, individual units or single bars. The present work, focuses on two classes of bistable structural systems: pyramidal trusses (undesired instability) and deployable scissor structures (desired design instability). Theoretical and computational tools are developed to investigate the influence of the strain measure, elasto-plastic deformations and instability phenomena on the nonlinear static and dynamic response of bistable pyramidal trusses. A compliant corrotational spatial joint finite element formulation with finite size is developed and applied to study bistable deployable scissor modules. The analysis of bistable large span structures formed by the assembly of modules is also carried out. It s shown that the presence and interaction of the studied buckling sources have deep influence on the systems behavior and can ultimately determine their viability in practical applications.

Rapidly assembled tent structures are temporary enclosures used to house people or goods. Their uses vary to include recreation, refugee housing, and military shelters. The structural concepts applied in these shelters are as variable as their uses. Some make use of a tensioned fabric and pole system to provide structural strength. Others have a load-bearing frame with attached fabric skin. Further variants make use of inflatable arches or consist of modular containers. Analysis of a number of different types of rapidly assembled tent structures reveals an area where innovation can occur. Conflicts in the last ten years suggest that rapidly assembled shelters for both military purposes and humanitarian relief have the greatest need for innovative solutions. Existing shelters used by the military lack the versatility and speed of deployment necessary in modern conflict. The lack of scalability in the designs makes it difficult to use an existing tent in different situations. They are slow to construct, heavy, and difficult to transport in large numbers. These problems suggest that there is a need for new shelters that better meet the needs of the military. The application of deployable structures technology meets military's needs for structures with the advantages of a small compacted volume, rapid assembly, and ease of deployment. This makes them ideal for application to shelter structures. The aim of this dissertation was to develop a new type of deployable, long-span shelter frame based upon tiled Bennett mechanisms. An overlapping combination of equilateral Bennett mechanisms yields a structure that opens into a half-cylinder shape, providing an enclosed space useful and applicable to the problem of deployable shelters. The specific application considered in the design portion of this process will be a long-span deployable shelter capable of housing military helicopters. This report details the development of the Bennett Shelter concept. Its deployed and compacted geometries are explored, and a procedure for determining structural properties and dimensions is presented. The full concept for the structure, from outer covering to foundation support is then detailed. Loads affecting the structure are determined, and the process of modelling and analysing the structure is then considered. Optimisation of the structure with respect to weight and serviceability requirements is conducted using a number of different materials, and full analysis of the optimal geometries is completed. As no method exists for evaluating the effect of imperfections on the deployment of overconstrained mechanisms, a procedure is derived. The effects of manufacturing imperfections on deployment of the Bennett mechanism are then explored using the method. A full examination of the variation of energy within the Bennett Shelter during deployment provides valuable insight into the performance of the structure. With the above analysis complete, it is shown that the Bennett Shelter is viable as a long-span deployable shelter.

Dans un contexte où l'utilisation de structures déployables s'est généralisée, le département Recherche de la société Thales Alenia Space étudie un nouveau concept de télescope spatial dont le miroir secondaire est déployé grâce au déroulement de six mètres rubans. Des études antérieures ont permis la mise au point d'un prototype constitué de rubans métalliques dont le déploiement s'est avéré trop violent. Dans ce travail de thèse nous proposons d'une part un nouveau type de ruban à la vitesse de déroulement maîtrisable et d'autre part un modèle original décrivant le comportement dynamique de tels rubans, permettant de mieux appréhender les phénomènes complexes pouvant intervenir lors de scénarios de pliage, de déploiement ou de déroulement. La solution envisagée pour contrôler la vitesse de déroulement repose sur l'exploitation des propriétés mécaniques d'une couche de matériau viscoélastique collée à la surface du ruban. Ces propriétés variant avec la température permettent de garantir un maintien de la position enroulée à froid et assurent un déroulement régulé grâce à un réchauffage localisé. Ces phénomènes ont été mis en évidence expérimentalement et numériquement. La lourdeur des méthodes classiques de modélisation et le manque de richesse des méthodes simplifiées nous ont conduit à développer un modèle de poutre à section fortement déformable permettant de décrire le comportement dynamique des rubans en grands déplacements. Partant d'un modèle de coque, l'originalité de la méthode repose essentiellement sur l'introduction d'une cinématique de type elastica pour décrire les grandes variations de forme de la section. Un modèle énergétique 1D est obtenu en intégrant dans la section et le problème est résolu à l'aide du logiciel de modélisation par éléments finis COMSOL. On propose finalement un modèle continu 1D à 4 paramètres cinématiques qui permet de rendre compte d'une large gamme de phénomènes intervenant dans des scénarios complexes de pliage, de déroulement et de déploiement dynamique. / The research department of Thales Alenia Space is studying new concepts of space telescopes whose secondary mirror is deployed thanks to the unreeling of six tape-springs. A breadboard using metallic tape-springs has been built during preliminary studies and has exhibited a deployment that is too energetic and induce too important shocks.In this thesis a new kind of tape-spring with a controlled uncoiling speed is introduced. Secondly a rod model with highly deformable thin-walled cross-sections describing the dynamic behaviour of tape-springs is derived.In order to over come the deployment speed of a tape spring, a viscoelastic layer is stuck on its sides. Thanks to its properties varying with the temperature, the viscoelastic layer is used to maintain the tape-spring in a coiled configuration at low temperature whereas a local heating leads to a controlled uncoiling. These phenomenons have been underlined experimentally and numerically.Because of the high complexity of classical shell models and the lack of details of simplified models, smart modelling methods need to be developed to describe the highly non linear behaviour of a tape-spring. A planar rod model with highly deformable thin-walled cross-sections that accounts for large displacements and large rotations in dynamics is proposed. Starting from a classical shellmodel, the main additional assumption consists in introducing an elastica kinematics to describe thelarge changes of the cross-section shape with very few parameters. The expressions of the strain andkinetic energies are derived by performing an analytical integration over the section. The Hamilton principle is directly introduced in a suitable finite element software to solve the problem. Several examples (folding, coiling and deployment of a tape spring) are studied through the FEM software COMSOL to demonstrate the ability of the 4-parameter model to account for several phenomena: creation of a single fold and associated snap-through behaviour, splitting of a fold into two, motion of a fold along the tape during a dynamic deployment, scenarios of coiling and uncoiling of a bistable tape-spring.