Letteratura scientifica selezionata sul tema "Fibres flexibles"
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Articoli di riviste sul tema "Fibres flexibles"
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Grinholtz, D., M. Haddad, M. Talso, E. Émiliani, S. Doizi e O. Traxer. "Étude des contraintes induites par les fibres laser dans les urétéroscopes flexibles". Progrès en Urologie 26, n. 13 (novembre 2016): 699. http://dx.doi.org/10.1016/j.purol.2016.07.062.
Testo completo
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Parasakthibala, Ms G., e Mrs A. S. Monisha. "A Review on Natural Fibers; Its Properties and Application Over Synthetic Fibers". International Journal for Research in Applied Science and Engineering Technology 10, n. 8 (31 agosto 2022): 1894–97. http://dx.doi.org/10.22214/ijraset.2022.46530.
Testo completoAbstract (sommario):
Abstract: Fibre is a long, thin strand or thread of material made by weaving or knitting threads together. Fibre is a hair like strand of material. A fibre is the smallest visible unit of any textile product. Fibres are flexible and may be spun into yarn and made into fabric. Natural fibres are taken from animals, vegetables or mineral sources. A few examples of widely used natural fibres include animal fibre such as wool and silk vegetables fibres, especially cotton and flax and asbestos, a mineral. Natural fibers are more important part in our human environment. Natural fibers are ecofriendly and inexpensive which are readily available in nature. In this chapter we discuss about the overview of natural fiber and their characteristic. this paper also deals with the impact of natural fibers over the synthetic fibers and also the application of natural fiber in various fields.
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Guo, Y., C. Wassgren, B. Hancock, W. Ketterhagen e J. Curtis. "Computational study of granular shear flows of dry flexible fibres using the discrete element method". Journal of Fluid Mechanics 775 (16 giugno 2015): 24–52. http://dx.doi.org/10.1017/jfm.2015.289.
Testo completoAbstract (sommario):
In this study, shear flows of dry flexible fibres are numerically modelled using the discrete element method (DEM), and the effects of fibre properties on the flow behaviour and solid-phase stresses are explored. In the DEM simulations, a fibre is formed by connecting a number of spheres in a straight line using deformable and elastic bonds. The forces and moments induced by the bond deformation resist the relative normal, tangential, bending and torsional movements between two bonded spheres. The bond or deforming stiffness determines the flexibility of the fibres and the bond damping accounts for the energy dissipation in the fibre vibration. The simulation results show that elastically bonded fibres have smaller effective coefficients of restitution than rigidly connected fibres. Thus, smaller solid-phase stresses are obtained for flexible fibres, particularly with bond damping, compared with rigid fibres. Frictionless fibres tend to align with a small angle from the flow direction as the solid volume fraction increases, and fibre deformation is minimized due to the alignment. However, jamming, with a corresponding sharp stress increase, large fibre deformation and dense contact force network, occurs for fibres with friction at high solid volume fractions. It is also found that jamming is more prevalent in dense flows with larger fibre friction coefficient, rougher surface, larger stiffness and larger aspect ratio.
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Ullrich, Julia, Martin Eisenreich, Yvonne Zimmermann, Dominik Mayer, Nina Koehne, Jacqueline F. Tschannett, Amalid Mahmud-Ali e Thomas Bechtold. "Piezo-Sensitive Fabrics from Carbon Black Containing Conductive Cellulose Fibres for Flexible Pressure Sensors". Materials 13, n. 22 (16 novembre 2020): 5150. http://dx.doi.org/10.3390/ma13225150.
Testo completoAbstract (sommario):
The design of flexible sensors which can be incorporated in textile structures is of decisive importance for the future development of wearables. In addition to their technical functionality, the materials chosen to construct the sensor should be nontoxic, affordable, and compatible with future recycling. Conductive fibres were produced by incorporation of carbon black into regenerated cellulose fibres. By incorporation of 23 wt.% and 27 wt.% carbon black, the surface resistance of the fibres reduced from 1.3 × 1010 Ω·cm for standard viscose fibres to 2.7 × 103 and 475 Ω·cm, respectively. Fibre tenacity reduced to 30–50% of a standard viscose; however, it was sufficient to allow processing of the material in standard textile operations. A fibre blend of the conductive viscose fibres with polyester fibres was used to produce a needle-punched nonwoven material with piezo-electric properties, which was used as a pressure sensor in the very low pressure range of 400–1000 Pa. The durability of the sensor was demonstrated in repetitive load/relaxation cycles. As a regenerated cellulose fibre, the carbon-black-incorporated cellulose fibre is compatible with standard textile processing operations and, thus, will be of high interest as a functional element in future wearables.
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Wang, Zhixun, Zhe Wang, Dong Li, Chunlei Yang, Qichong Zhang, Ming Chen, Huajian Gao e Lei Wei. "High-quality semiconductor fibres via mechanical design". Nature 626, n. 7997 (31 gennaio 2024): 72–78. http://dx.doi.org/10.1038/s41586-023-06946-0.
Testo completoAbstract (sommario):
AbstractRecent breakthroughs in fibre technology have enabled the assembly of functional materials with intimate interfaces into a single fibre with specific geometries1–11, delivering diverse functionalities over a large area, for example, serving as sensors, actuators, energy harvesting and storage, display, and healthcare apparatus12–17. As semiconductors are the critical component that governs device performance, the selection, control and engineering of semiconductors inside fibres are the key pathways to enabling high-performance functional fibres. However, owing to stress development and capillary instability in the high-yield fibre thermal drawing, both cracks and deformations in the semiconductor cores considerably affect the performance of these fibres. Here we report a mechanical design to achieve ultralong, fracture-free and perturbation-free semiconductor fibres, guided by a study on stress development and capillary instability at three stages of the fibre formation: the viscous flow, the core crystallization and the subsequent cooling stage. Then, the exposed semiconductor wires can be integrated into a single flexible fibre with well-defined interfaces with metal electrodes, thereby achieving optoelectronic fibres and large-scale optoelectronic fabrics. This work provides fundamental insights into extreme mechanics and fluid dynamics with geometries that are inaccessible in traditional platforms, essentially addressing the increasing demand for flexible and wearable optoelectronics.
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Manikantan, Harishankar, Lei Li, Saverio E. Spagnolie e David Saintillan. "The instability of a sedimenting suspension of weakly flexible fibres". Journal of Fluid Mechanics 756 (9 settembre 2014): 935–64. http://dx.doi.org/10.1017/jfm.2014.482.
Testo completoAbstract (sommario):
AbstractSuspensions of sedimenting slender fibres in a viscous fluid are known to be unstable to fluctuations of concentration. In this paper we develop a theory for the role of fibre flexibility in sedimenting suspensions in the asymptotic regime of weakly flexible bodies (large elasto-gravitation number). Unlike the behaviour of straight fibres, individual flexible filaments rotate as they sediment, leading to an anisotropic base state of fibre orientations in an otherwise homogeneous suspension. A mean-field theory is derived to describe the evolution of fibre concentration and orientation fields, and we explore the stability of the base state to perturbations of fibre concentration. We show that fibre flexibility affects suspension stability in two distinct and competing ways: the anisotropy of the base state renders the suspension more unstable to perturbations, while individual particle self-rotation acts to prevent clustering and stabilizes the suspension. In the presence of thermal noise, the dominant effect depends critically upon the relative scales of flexible fibre self-rotation compared to rotational Brownian motion.
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LUSIS, Vitalijs, Andrejs KRASNIKOVS, Olga KONONOVA, Videvuds-Arijs LAPSA, Rimvydas STONYS, Arturs MACANOVSKIS e Arturs LUKASENOKS. "EFFECT OF SHORT FIBERS ORIENTATION ON MECHANICAL PROPERTIES OF COMPOSITE MATERIAL – FIBER REINFORCED CONCRETE". Journal of Civil Engineering and Management 23, n. 8 (20 novembre 2017): 1091–99. http://dx.doi.org/10.3846/13923730.2017.1381643.
Testo completoAbstract (sommario):
Traditional fiberconcrete structures have fibres in the mix oriented in all spatial directions, distributed in the structural element volume homogenously, what not easy to obtain in practice. In many situations, structurally more effective is the insertion of fibres into the concrete structural element body by forming layers, with a predetermined fibre concentration and orientation in every layer. In the present investigation, layered fibre concrete is under investigation. Short steel fibres were attached to flexible warps with the necessary fibres concentration and orientation. Warps were placed into the prismatic mould separating them by concrete layers without fibres. Prisms were matured and tested under four-point bending. The bending-affected mechanical behaviour of cracked fibre concrete was simulated numerically by using a developed structural model. Comparing the simulation results with experimental data, material micromechanical fracture mechanisms were analysed and evaluated.
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Prabu, Krishnaa, J. Srinivasan e C. Prakash. "Ceramic and Glass Fibre Reinforced Flexible Composites for Particulate Filter Walls – A Novel Approach". Fibres and Textiles in Eastern Europe 27, n. 3(135) (30 giugno 2019): 91–97. http://dx.doi.org/10.5604/01.3001.0012.7747.
Testo completoAbstract (sommario):
Flexible composites from high performance fibres were developed and targeted to replace the wall of existing rigid ceramic Particulate Filters. The composites are made from E Glass fibre webs of different density in the middle, with standard SiC Ceramic fibres webs in in the outer layers, forming a sandwich structure. Different needling densities were applied to form nonwoven composites, and they were stitched diagonally on the surface at specified intervals with continuous glass fibre filament yarn. In total, nine novel flexible composites were developed and evaluated for their structural, surface, mechanical and thermal properties. Based on the results and statistical analysis, the B2 sample is considered to be taken for further research to develop Particulate Matter (PM) filters.
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Hamedi, Naser, e Lars-Göran Westerberg. "Simulation of Flexible Fibre Particle Interaction with a Single Cylinder". Processes 9, n. 2 (20 gennaio 2021): 191. http://dx.doi.org/10.3390/pr9020191.
Testo completoAbstract (sommario):
In the present study, the flow of a fibre suspension in a channel containing a cylinder was numerically studied for a very low Reynolds number. Further, the model was validated against previous studies by observing the flexible fibres in the shear flow. The model was employed to simulate the rigid, semi-flexible, and fully flexible fibre particle in the flow past a single cylinder. Two different fibre lengths with various flexibilities were applied in the simulations, while the initial orientation angle to the flow direction was changed between 45° ≤ θ ≤ 75°. It was shown that the influence of the fibre orientation was more significant for the larger orientation angle. The results highlighted the influence of several factors affecting the fibre particle in the flow past the cylinder.
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Wan, Tao Yu, Mohammad Chowdhury e George K. Stylios. "The Formation and Morphology of PVA Ferrogel Nanofibre by the Electrospinning Process". Materials Science Forum 650 (maggio 2010): 361–66. http://dx.doi.org/10.4028/www.scientific.net/msf.650.361.
Testo completoAbstract (sommario):
Aqueous solutions of polyvinyl alcohol (PVA) with FeCl3 were homogenously mixed and subsequently electrospun; and its characteristics were studied as a function of voltage, tip-target distance and solution flow rate. Fiber mats of (PVA)/FeCl3 composite, in the diameter of 700–1100 nm were prepared by electrospinning. Lower concentrations of solution tended to facilitate the formation of fibres with beads. With increasing concentration, the morphology was improved with smooth and uniform fibres and the increased fibre diameters in the nano range. Spinning voltage also had an important influence on the diameters of the nano fibres, while the collection distance affected fibre diameters. Nano fibres of smaller diameter were formed when lower voltages are applied. The morphology of the electrospun from PVA/FeCl3 nano fibres and their magnetic power was observed and analyzed by scanning electron microscopy (SEM).The fibres produced in this way could potentially be applied to manufacture magnetic sensors, flexible magnets.
Tesi sul tema "Fibres flexibles"
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Allende, Sofia. "Dynamique et statistiques de particules allongées et flexibles dans des écoulements turbulents". Thesis, Université Côte d'Azur, 2021. https://tel.archives-ouvertes.fr/tel-03284996.
Testo completoAbstract (sommario):
Cette thèse analyse la dynamique de petits objets complexes immergés dans des environnements turbulents. Les champs turbulents peuvent être vus comme des champs aléatoires très fluctuants, dont les statistiques sont en général fortement non-Gaussiennes et se caractérisent par la présence de fluctuations très violentes. En pratique, la turbulence est le mécanisme dominant régissant le transport et le mélange de matière. Dans leurs détails, les propriétés statistiques du transport turbulent dépendent de la nature des particules considérées. Ici, nous nous concentrons sur le transport de petites particules complexes, qui sont caractérisées par une interaction non triviale entre leur masse, leur forme et leur rhéologie. Notre objectif est d’acquérir une compréhension physique de la façon dont les fluctuations turbulentes prescrivent la dynamique de ces particules complexes, et se manifestent au travers à la fois des phénomènes collectifs comme la concentration préférentielle, ou des phénomènes individuels allants de la déformation de particules jusqu’à leur fragmentation. Ces manifestations physiques de la turbulence ont des conséquences tant au niveau industriel que du développement durable. Par exemple, le transport atmosphérique de cendres volcaniques a des conséquences dans le secteur aéronautique commercial, ainsi que la floraison de méduses ou de phytoplancton dans les océans a des conséquences à la fois sur la maintenance des circuits de refroidissement des centrales thermiques, et sur la thermodynamique de la Terre.Nos recherches s'appuient sur des simulations numériques massives et systématiques basées sur l'intégration directe des équations de Navier-Stokes incompressibles, ce pour générer une turbulence isotrope homogène à très haut nombre de Reynolds. À partir de ces simulations, nous analysons les statistiques de différents types de particules tels que des sphéroïdes inertiels ou des fibres flexibles. Pour les sphéroïdes, nos travaux montrent que les dynamiques translationnelles et rotationnelles sont essentiellement découplées. Alors que le mouvement de translation se rattache à celui d’une sphère avec une masse effective, la dynamique de l'orientation présente des caractéristiques plus complexes. Cette complexité se reflète dans les statistiques du taux de rotation et dans les propriétés de concentration. Ainsi, la dynamique de rotation n'est pas universelle et dépend de la forme spécifique des particules.Pour les fibres nous constatons que leur dynamique est, la plupart du temps, qualitativement très semblable à celle d’une tige rigide. En des occasions très rares et intermittentes les fibres flambent violemment, et ces événements se corrèlent aux fortes compressions locales exercées par le fluide turbulent. En outre, les statistiques de l'orientation des fibres diffèrent sensiblement des statistiques de tiges parfaitement rigides, même en dehors de ces événements de flambages. Ces déviations peuvent être comprises comme des « anomalies d'alignement » causées par la flexibilité. Notre observation principale est le fait que le couplage entre les fibres et la turbulence peut se modéliser en termes de différents processus d’activation, qui rendent compte à la fois des statistiques du flambage et des anomalies de l'alignement. Nous étudions enfin la fragmentation des fibres dues à la turbulence. À cette fin, nous implémentons dans nos codes numériques deux mécanismes de rupture : flexion et tension. Nous esquissons un cadre stochastique de tels événements catastrophiques, qui justifie l'usage d'équations cinétiques du type Smoluchowski pour la description statistique de la fragmentation en temps long, et ce malgré la présence des corrélations temporelles non triviales dans les fluctuations turbulentes Lagrangiennes. Cette description ouvre des perspectives pour mieux quantifier la fragmentation des matériaux fragiles dans les codes utilisés pour la prévention des risques dans des cadres industrielsThis thesis analyses the dynamics of small complex objects immersed in a turbulent environment. Turbulent flows are akin to apparent random fields, that usually display very non-Gaussian and fluctuating statistics, and which are known to enhance the mixing and the transport of the objects that they carry. Here, we focus on the transport of small complex particles, which are characterized by a non-trivial interplay between their mass, their shape and their rheology. Our aim is to gain a physical understanding on how turbulent fluctuations prescribe the dynamics of such complex particles, and lead to various physical phenomena, including preferential concentration, their deformation or catastrophic events such as their fragmentation. Studying such phenomena is relevant for both industrial and sustainability issues. For instance, while volcanic ash has direct impacts for the commercial flight industry, the blooming of diverse types of species such as jellyfishes or phytoplankton has consequences both for the maintenance of power plants and for the thermodynamics of our planet.Our approach relies on a systematic use of massive numerical simulations of the Navier-Stokes equations to generate homogeneous isotropic turbulence at high Reynolds number, and analyze in details the statistics of various types of particles such as inertial spheroids and flexible fibers. For small inertial spheroids, our numerical work shows that the translational and the rotational motion are essentially decoupled. While the translational motion can be described by the motion of a sphere with a suitably defined effective mass, the rotational dynamics displays more intricate features. This reflects in the statistics of the rotation rate and in the concentration properties. Conversely to translational motion, the rotational dynamics is therefore non-universal and depends on the specific shape of the spheroids.For small inertialess fibers, which constitute a paradigmatic example of flexible elongated particles, we find that the dynamics is most of the time closely resembling that of a stiff rod. Yet, in very rare and intermittent episodes, the fibers experience violent buckling events, which correlate to strong local compressions exerted by the local turbulent flow. Besides, detailed statistical investigations reveal that flexibility also produces misalignments of the fibers, e.g. deviations in the statistics of the orientation compared to the dynamics of a completely stiff rod. Our most salient observation is that the coupling between such flexible fibers and the turbulence can be phenomenologically modeled in terms of various activation processes, both for the buckling rate and for the misalignments statistics.We finally investigate scenarios for turbulent fragmentation of brittle fibers. To that end, we implement in our numerics two mechanisms leading to the fibers breaking in smaller pieces, either because of tensile failure or because of flexural failure. We sketch a stochastic description of such violent events that paves the way to better parametrization of turbulent-induced fragmentation of brittle material in industrial codes
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Schulmann, Nava. "Du polymère à la fibre : Conformations et élasticité de chaines à deux dimensions". Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAE014/document.
Testo completoAbstract (sommario):
Cette thèse de doctorat est consacrée à l’étude analytique et numérique de systèmes de polymères et de fibres à deux dimensions. Des systèmes de polymères confinés en films ultra-minces présentent un très grand intérêt technologique et expérimentale et posent de nombreux défis théoriques en raison de leur fort comportement non-champ moyen qui se manifeste par divers exposants critiques non triviaux. Nous nous concentrons sur la limite strictement 2D où le croisement des chaînes est interdit et nous étudions, en fonction de la densité et de la rigidité des chaînes, les propriétés élastiques et conformationnelles de trois classes de systèmes: polymères flexibles et semi flexibles à température finie et polymères macroscopiques athermiques (fibres) à courbure spontanée imposée. Pour les polymères flexibles, il est démontré que bien que les polymères auto-évitant denses adoptent des configurations compactes avec un exposant de Flory ν = 1/2, ils ne se comportent pas comme des chaines gaussiennes. En particulier un exposant de contact non-nul θ2 = 3/4 implique une dimension fractale de périmètre dp = 5/4. Par conséquence, en accord avec la loi généralisée de Porod, le facteur de structure intramoléculaire F(q) révèle un comportement non-gaussien et la température de démixion des mélanges de polymères 2D devrait être réduite. Nous étudions également les effets de la rigidité des chaînes sur les systèmes de polymères à 2D et constatons que le comportement universel n’est pas modifié lorsque la longueur de persistance est beaucoup plus petite que la longueur de confinement. La nature de la transition de phase nématique à haute rigidité, qui est dans le cas 2D l’objet d’un débat de longue date, est également explorée. Des résultats préliminaires semblent indiquer une transition du premier ordre. Enfin, motivés par un travail théorique récent sur les modules élastiques de faisceaux de fibres, nous étudions les effets de la courbure spontanée sur l’élasticité d’ensembles de fibres. Nous montrons que en jouant sur le désordre des amplitudes des modes de Fourier de l’état fondamental il est possible de régler le module de compression, en accord qualitatif avec la théorieThis PhD thesis is devoted to a theoretical study of polymer and ’polymer like’ systems in strictly two dimensions. Polymer systems in reduced dimensions are of high experimental and technological interest and present theoretical challenges due to their strong non-mean-field-like behavior manifested by various non-trivial universal power law exponents. We focus on the strictly 2D limit where chain crossing is forbidden and study as function of density and of chain rigidity conformational and elastic properties of three system classes: flexible and semiflexible polymers at finite temperature and macroscopic athermal polymers (fibers) with imposed quenched curvature. For flexible polymers it is shown that although dense self-avoiding polymers are segregated with Flory exponent ν = 1/2 , they do not behave as Gaussian chains. In particular a non-zero contact exponent θ2 = 3/4 implies a fractal perimeter dimension of dp = 5/4. As a consequence and in agreement with the generalized Porod law, the intramolecular structure factor F(q) reveals a non-Gaussian behavior and the demixing temperature of 2D polymer blends is expected to be reduced. We also investigate the effects of chain rigidity on 2D polymer systems and found that universal behavior is not changed when the persistence length is not too large compared to the semidilute blob size. The nature of the nematic phase transition at higher rigidities, which is in the 2D case the subject of a long standing debate, is also briefly explored. Preliminary results seem to indicate a first order transition. Finally, motivated by recent theoretical work on elastic moduli of fiber bundles, we study the effects of spontaneous curvature at zero temperature. We show that by playing on the disorder of the Fourier mode amplitudes of the ground state, it is possible to tune the compression modulus, in qualitative agreement with theory
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Makanga, Ursy. "Transport and deformation of flexible fibers in structured environments". Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAX080.
Testo completoAbstract (sommario):
Les fibres flexibles se rencontrent dans diverses situations dans la nature et les applications industrielles. Parmi lesquelles on trouve des fibres de microplastiques, des fibres de cellulose et des structures filamenteuses résultant de colonies bactériennes dites “biofilms". Dans la plupart des cas, les fibres flexibles sont généralement immergées dans des environnements fluidiques qui sont munis d'obstacles. A titre d'exemple, les lave-linge rejettent un grand nombre de fibres de microplastiques (environ 1900 fibres par lavage) dans des eaux usées contenant plusieurs débris. Dans de tels environnements complexes, les fibres peuvent adopter différentes formes non triviales et se déplacer suivant différents modes à travers les obstacles environnants. Ces différents comportements résultent du couplage complexe entre la réponse élastique des fibres, les collisions et les interactions hydrodynamiques. Leur compréhension est par conséquent essentielle pour l'étude des systèmes biologiques, environnementaux et industriels, où des phénomènes similaires sont observés, de même que pour éviter des problèmes majeurs comme la pollution ou le colmatage. Au cours des dernières décennies, la modélisation des particules élancées immergées dans un fluide visqueux a été un domaine majeur de recherche en mécanique des fluides. Cependant, le développement des modèles numériques permettant de prendre en compte des environnements munis d'obstacles a été peu abordé. Le problème raide à résoudre sous contraintes qui en résulte en est une des raisons. Modéliser des fibres dans de tels environnements est un défi majeur pour les approches numériques actuelles.Ainsi, dans cette thèse, nous proposerons une méthodologie pour simuler des fibres flexibles dans des environnements fluidiques munis d'obstacles. Notre implémentation permet de simuler des systèmes contenant un nombre considérable de fibres et d'obstacles en des temps raisonnables sur une seule carte graphique (GPU). Forts de cet outil, et d'expériences simples, nous étudierons ensuite le problème de sédimentation des fibres flexibles dans des environnements complexes. Nos résultats jettent les bases pour de futures expériences et fournissent des ingrédients physiques essentiels pour la conception des dispositifs de tri de particules sous l'action de la gravitéFlexible fibers are encountered in various situations in nature and industrial applications. Examples include microplastics fibers, cellulose fibers, and biofilm streamers. In a wide range of such situations, flexible fibers are often immersed in a fluidic environment with obstacles embedded. For instance, laundry washing machines discharge a large number of microplastics fibers (around 1900 fibers per wash) into wastewaters which contain a significant amount of debris. In such complex media, flexible fibers can exhibit nontrivial conformations and different modes of transport through the surrounding obstacles. These dynamics result from the complex interplay between their elastic response, collisions and hydrodynamic interactions. Understanding of these phenomena is therefore essential to study the physics of biological, environmental and industrial systems, but also to prevent issues such as pollution or clogging. While modeling slender particles in viscous fluids has been a major area of research over the past few decades, methodologies involving surrounding environments are scarce. The resulting complex coupling leads to a constrained formulation of the problem in addition of being stiff. Therefore, modeling fibers in complex media is challenging and can be computationally costly.In this thesis, we will propose a methodology to model flexible fibers in different environments that are made of rigid stationary obstacles. Our implementation enables dynamic simulations of large systems in a reasonable wall times on a single modern Graphics Processing Unit (GPU). Using the capabilities afforded by our method, together with simple experiments, we will investigate the sedimentation of flexible fibers in structured environments. The resulting findings provide physical insight into future experiments and the design of gravity-based sorting devices
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Daieff, Marine. "Deformation and shape of flexible, microscale helices in viscous flows". Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC189/document.
Testo completoAbstract (sommario):
Les interactions fluide-structure sont d'un grand intérêt en ingénierie et pour des applications industrielles et médicales. Comprendre les interactions entre des particules aux formes complexes et des écoulements peut mener à de nouveaux projets pour l'administration ciblée de médicaments, pour des micro capteurs de débit et à une meilleure compréhension du comportement des micro-organismes. Dans cette thèse, nous étudions l'interaction fluide-structure de particules chirales de taille microscopique à bas nombres de Reynolds. Les particules sont rigides et confinées dans une géométrie 2D ou flexibles avec une forme hélicoïdale. Combiner des techniques de microfabrication, comme des méthodes d'assemblage multi-échelles et la microfluidique, permet d'avoir un excellent contrôle à la fois sur les propriétés géométriques et mécaniques des fibres et aussi sur les caractéristiques de l'écoulement comme ses propriétés Newtoniennes et non Newtoniennes, sa vitesse et sa géométrie. Dans un premier temps, nous avons étudié des fibres rigides, 2D et asymétriques, i.e. des fibres en L. Les confinements latéral et transversal ont été étudiés tout comme la forme de la fibre. Lorsque la particule est transportée dans un écoulement visqueux, elle tourne jusqu'à atteindre une orientation d'équilibre. Dans cette orientation particulière, la fibre se décale vers les murs latéraux du canal. Une étude complète des trajectoires de la fibre a été réalisée et des comparaisons avec des particules symétriques ont été faites. Ce sujet de recherche pourrait aider à concevoir des dispositifs pour trier des particules à des fins médicales. Dans un second temps, nous avons étudié des fibres hélicoïdales flexibles de taille micrométrique. La dynamique de formation de l'hélice a été analysée. Les hélices se forment à partir de rubans droits 2D qui, de façon spontanée, s'enroulent quand ils sont libérés dans l'eau. La forme hélicoïdale est obtenue seulement quelques minutes après la libération des rubans mais l'hélice continue à rétrécir pendant plusieurs heures jusqu'à ce qu'elle atteigne une courbure préférentielle. Deux temps caractéristiques sont identifiés dans cette dynamique de formation. Un modèle a été développé pour comprendre le complexe équilibre entre les forces élastiques, de tension de surface et visqueuses aux temps courts. Après avoir analysé plusieurs hypothèses, comme l'impact d'une couche sacrificielle, une possible modification du module du matériau et la présence de fluage, l'évolution du rayon de l'hélice aux temps longs s'explique probablement par du fluage. La dynamique d'extension et de relaxation de la fibre flexible a aussi été étudiée dans des fluides Newtonien et non Newtonien. L'étude dans des solutions de polymères est pertinente et intéressante car la taille des micro hélices est comparable à celle des flagelles des micro-organismes et à celle de chaînes de polymères de grande masse moléculaire. Il s'agit donc d'un problème mutli-échelles complexe car la viscosité locale au niveau du ruban pourrait être différente de la viscosité globale de l'écoulementFluid-structure interactions are of wide interest in engineering, industrial and medical applications. Understanding the interactions between complex shaped particles and flows might lead to new designs for targeted delivery, microflow sensors and to a better understanding of the behavior of microorganisms. In this thesis, we study the fluid-structure interaction of microscale chiral particles at low Reynolds numbers. The particles are rigid and confined in a 2D geometry or flexible with a helical shape. The combination of microfabrication techniques, such as multiscale assembly methods and microfluidics, enables to have a perfect control on both the geometrical and mechanical properties of the fibers and the flow features such as Newtonian or non Newtonian properties, the flow velocity and the flow geometry. First we studied asymmetric 2D rigid fibers, i.e. L-shaped fibers. Both lateral and transversal confinements have been investigated, as well as the shape of the fiber. When the particle is transported in viscous flows, it rotates until reaching an equilibrium orientation. In this specific orientation, the fiber drifts towards the lateral walls of the channel. A full investigation on the trajectories of the fiber has been performed and comparisons with symmetric particles have been done. Such research may help design devices to sort particles for medical purposes. Secondly we studied flexible microscale helical fibers. The dynamics of the helix formation has been investigated. The helices are formed from straight 2D ribbons, which spontaneously coil when released in water. The helical shape is reached only several minutes after the release but the helix keeps shrinking during several hours until reaching a preferred curvature. Two different timescales are identified in this formation dynamics. A model has been developed to understand the complex balance between elastic, surface tension and viscous forces at short times. After investigating several assumptions such as the impact of a sacrificial layer, a possible change in the modulus of the material and a creep behavior, the evolution of the radius at long times is most likely explained by creep. The extension and relaxation dynamics of the flexible fiber has also been studied in Newtonian and non Newtonian fluids. The study in polymer solutions is relevant and interesting because the size of the microhelix is comparable to the flagella of microorganisms and to the chains of high molecular weight polymers. Complex multiscale problems are then involved as the local viscosity at the scale of the ribbon might differ from the global viscosity at the scale of the flow
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Joung, Clint Gwarngsoo. "Direct simulation studies of suspended particles and fibre-filled suspensions". Thesis, The University of Sydney, 2003. http://hdl.handle.net/2123/554.
Testo completoAbstract (sommario):
A new Direct Simulation fibre model was developed which allowed flexibility in the fibre during the simulation of fibre suspension flow.This new model was called the 'Chain-of-Spheres' model.It was hypothesised that particle shape and deformation could significantly affect particle dynamics,and also suspension bulk properties such as viscosity.Data collected from the simulation showed that flexible fibres in shear flow resulted in an order of 7 −10% bulk relative viscosity increase over the 'rigid' fibre result.Results also established the existence of a relationship between bulk viscosity and particle stiffness. In comparison with experimental results,other more conventional rigid fibre based methods appeared to underpredict relative viscosity.The flexible fibre method thus markedly improved the ability to estimate relative viscosity.The curved rigid fibre suspension also exhibited increased viscosity of the order twice that of the equivalent straight rigid fibre suspension.With such sensitivity to fibre shape,this result has some important implications for the quality of fibre inclusions used.For consistent viscosity,the shape quality of the fibres was shown to be important. The 'Chain of Spheres' simulation was substantially extended to create a new simulation method with the ability to model the dynamics of arbitrarily shaped particles in the Newtonian flow field.This new '3D Particle' simulation method accounted for the inertial force on the particles,and also allowed particles to be embedded in complex flow fields.This method was used to reproduce known dynamics for common particle shapes,and then to predict the unknown dynamics of various other particle shapes in shear flow. In later sections, the simulation demonstrated inertia-induced particle migration in the non-linear shear gradient Couette cylinder flow,and was used to predict the fibre orientation within a diverging channel flow.The performance of the method was verified against known experimental measurements,observations and theoretical and numerical results where available.The comparisons revealed that the current method reproduced single particle dynamics with great fidelity. The broad aim of this research was to better understand the microstructural dynamics within the fibre-filled suspension and from it,derive useful engineering information on the bulk flow of these fluids.This thesis represents a move forward to meet this broad aim.It is hoped that future researchers may benefit from the new approaches and algorithms developed here.
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Joung, Clint Gwarngsoo. "Direct simulation studies of suspended particles and fibre-filled suspensions". University of Sydney. Chemical Engineering, 2003. http://hdl.handle.net/2123/554.
Testo completoAbstract (sommario):
A new Direct Simulation fibre model was developed which allowed flexibility in the fibre during the simulation of fibre suspension flow.This new model was called the �Chain-of-Spheres �model.It was hypothesised that particle shape and deformation could signi ficantly a ffect partic e dynamics,and also suspension bulk properties such as viscosity.Data collected from the simulation showed that flexible fibres in shear flow resulted in an order of 7 −10% bulk relative viscosity increase over the �rigid �fibre result.Results also es- tablished the existence of a relationship between bulk viscosity and particle sti ffness.In comparison with experimental results,other more conventional rigid fibre based methods appeared to underpredict relative viscosity.The flexible fibre method thus markedly improved the ability to estimate relative viscosity.The curved rigid fibre suspension also exhibited increased viscosity of the order twice that of the equivalent straight rigid fibre suspension.With such sensitivity to fibre shape,this result has some important implications for the quality of fibre inclusions used.For consistent viscosity,the shape quality of the fibres was shown to be important. The �Chain of Spheres �simulation was substantially extended to create a new simulation method with the ability to model the dynamics of arbitrarily shaped particles in the Newtonian flow field.This new �3D Particle �simulation method accounted for the inertial force on the particles,and also allowed particles to be embedded in complex flow fields.This method was used to reproduce known dynamics for common particle shapes,and then to predict the unknown dynamics of various other particle shapes in shear flow. In later sections, the simulation demonstrated inertia-induced particle migration inthe non-linear shear gradient Couette cylinder flow,and was used to predict the fibre orientation within a diverging channel flow.The performance of the method was verified against known experimental measurements,observations and theoretical and numerical results where available.The comparisons revealed that the current method reproduced single particle dynamics with great fidelity. The broad aim of this research was to better understand the microstruc- tural dynamics within the fibre-filled suspension and from it,derive useful engineering information on the bulk flow of these fluids.This thesis represents a move forward to meet this broad aim.It is hoped that future researchers may bene fit from the new approaches and algorithms developed here.
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Harris, Samantha Mary. "Dynamics of semi-flexible fibres in viscous flow". Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/53/.
Testo completoAbstract (sommario):
The dynamics of semi-flexible fibres in shear flow and the effect of flexibility on the swimming speed of helical flagella are investigated. High aspect ratio particles such as carbon and glass fibres are often added as fillers to processed polymers. Although these materials have high rigidity, the large aspect ratiomakes the fibres liable to bending during flow. Other high aspect ratio fibres that behave as semi-flexible fibres include carbon nano-tubes, paper fibres and semi-flexible polymers such as the muscle protein f-actin. Most theoretical studies assume that fibres are either rigid or completely flexible, but in this thesis fibres with a finite bending modulus are considered. A semi-flexible fibre is modelled as a chain of shorter rods linked together. A bending torque is included at the joints between the rods to account for the rigidity. In shear flow the simulation reproduces the C and S turns observed in experiments on semi-flexible fibres. The results for finite aspect ratio fibres predict changes to the period of rotation and drift between Jeffery orbits. The direction of drift for a flexible fibre depends on both the intial orientation and the fibre’s flexiblity. We also present a linear analysis of how small distortions to a straight semi-flexible fibre grow when the flow places the fibre under compression. These results are in agreement with our full simulations and the growth rates of the distortions to a straight fibre allow us to predict the most unstable mode at a particular flow rate. To allow for intrinsically bent or helical equilibrium shapes a second simulation method is developed that includes a twisting torque at the joints between the rods as well as a bending torque. Using this simulation we measure the period of rotation and orbit drift of permanently deformed fibres in shear flow and show that due to the asymmetry of a helix, shear induced rotation results in translation and orbit drift for both rigid and semi-flexible fibres. Bacteria such as Vibrio alginolyticus and Escherichia coli swim by rotating one or more helical flagella. Vibrio alginolyticus has only one flagella and changes direction by altering its sense of rotation. Experimental observations of Vibrio alginolyticus have found that backwards swimming is 50% faster than forwards swimming speed however, previous numerical simulation results have shown only a 4% difference for flagella of the same dimensions. We use our simulation to consider how flexiblity affects the swimming speed of helical flagella and show that for a constant angular velocity, difference between forwards and backwards swimming speed ranges between 0-23%depending on the exact stiffness chosen. We explain the differences in swimming speeds of semi-flexible fibres by investigating the shape changes which occur and comparing them to the results for swimming speeds of rigid flagella of varying dimensions.
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Thompson, Ian. "Use of steel fibres to reinforce cement bound roadbase". Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366364.
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Rezak, Sheila. "Analysis of flexible fiber suspensions using the Lattice Boltzmann method". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24798.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Co-Chair: Aidun, K. Cyrus; Committee Co-Chair: Ghiaasiaan, Mostafa; Committee Member: Deng, Yulin; Committee Member: Empie, Jeff; Committee Member: Patterson, Tim.
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Ybañez, y. Valeros Numer. "The crack bridging behavior of flexible fibers". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11817.
Testo completoAbstract (sommario):
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995.Includes bibliographical references (leaves 162-165).
by Numer Ybañez y Valeros.
M.S.
Libri sul tema "Fibres flexibles"
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Pen, Wang Ko, Mehta Atul C e Turner J. Francis, a cura di. Flexible bronchoscopy. 2a ed. Malden, Mass: Blackwell Pub., 2004.
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Brydon, A. G. Flexible card clothing and its application. Manchester: Textile Institute, 1988.
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Keller, Thomas. Use of fibre reinforced polymers in bridge construction. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2003. http://dx.doi.org/10.2749/sed007.
Testo completoAbstract (sommario):
<p>The aim of the present Structural Engineering Document, a state-of-the-art report, is to review the progress made worldwide in the use of fibre reinforced polymers as structural components in bridges until the end of the year 2000.<p> Due to their advantageous material properties such as high specific strength, a large tolerance for frost and de-icing salts and, furthermore, short installation times with minimum traffic interference, fibre reinforced polymers have matured to become valuable alternative building materials for bridge structures. Today, fibre reinforced polymers are manufactured industrially to semi-finished products and ccimplete structural components, which can be easily and quickly installed or erected on site.<p> Examples of semi-finished products and structural components available are flexible tension elements, profiles stiff in bending and sandwich panels. As tension elements, especially for the purpose of strengthening, strips and sheets are available, as weil as reinforcing bars for concrete reinforcement and prestressing members for internal prestressing or external use. Profiles are available for beams and columns, and sandwich constructions especially for bridge decks. During the manufacture of the structural components fibre-optic sensors for continuous monitoring can be integrated in the materials. Adhesives are being used more and more for joining components.<p> Fibre reinforced polymers have been used in bridge construction since the mid-1980s, mostly for the strengthening of existing structures, and increasingly since the mid-1990s as pilot projects for new structures. In the case of new structures, three basic types of applications can be distinguished: concrete reinforcement, new hybrid structures in combination with traditional construction materials, and all-composite applications, in which the new materials are used exclusively.<p> This Structural Engineering Document also includes application and research recommendations with particular reference to Switzerland.<p> This book is aimed at both students and practising engineers, working in the field of fibre reinforced polymers, bridge design, construction, repair and strengthening.
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Galperin, Inna. A numerical model of the motion of a curved flexible fibre in a shear flow. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1999.
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Dahl, Milo D. Effects of fiber motion on the acoustic behavior of an anisotropic, flexible fibrous material. [Washington, DC: National Aeronautics and Space Administration, 1987.
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1943-, Murry Thomas, a cura di. FEESST: Flexible endoscopic evaluation of swallowing with sensory testing. San Diego: Plural Pub., 2005.
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Turner, Roderick David. Dual wavelength fiber-optic polarimeter for path-integrated strain sensing: application to the measurement of local slope on a flexible beam. [Downsview, Ontario]: University of Toronto, Institute for Aerospace Studies, 1991.
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Turner, Roderick David. Dual wavelength fiber-optic polarimeter for path-integrated strain sensing: application to the measurement of local slope on a flexible beam. [Downsview, Ont.]: University of Toronto, Institute for Aerospace Studies, 1990.
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Melashvili, Yuri. Controlled structures with electromechanical and fiber-optical sensors. Hauppauge, NY, USA: Nova Science Publishers, 2008.
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Hearle, J. W. Mechanics of Flexible Fibre Assemblies. Ingramcontent, 2013.
Cerca il testo completoCapitoli di libri sul tema "Fibres flexibles"
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Ouagne, Pierre, e Mahadev Bar. "Natural Fibres-Based Hybrid Towpregs". In Flexible Towpregs and Their Thermoplastic Composites, 59–84. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003049715-3.
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Huang, YongAn, YeWang Su e Shan Jiang. "Self-Assembly of Self-Similar Fibers for Stretchable Electronics". In Flexible Electronics, 257–87. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-6623-1_10.
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Kuncová, G., J. Vlček, M. Kubečková e J. Götz. "Flexible self-centering die for coating fibres". In Progress and Trends in Rheology II, 391–94. Heidelberg: Steinkopff, 1988. http://dx.doi.org/10.1007/978-3-642-49337-9_135.
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Rath, Jan-Erik, Robert Graupner e Thorsten Schüppstuhl. "Die-Less Forming of Fiber-Reinforced Plastic Composites". In Lecture Notes in Mechanical Engineering, 3–14. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-18326-3_1.
Testo completoAbstract (sommario):
AbstractFiber-reinforced plastics (FRP) are increasingly popular in light weight applications such as aircraft manufacturing. However, most production processes of thin-walled FRP parts to date involve the use of expensive forming tools. This especially hinders cost-effective production of small series as well as individual parts and prototypes. In this paper, we develop new possible alternatives of highly automated and die-less production processes based on a short review of current approaches on flexible thin-walled FRP production. All proposed processes involve robot guided standard tools, similar to incremental sheet metal forming, for local forming of the base materials. These include woven glass fiber fabrics which are locally impregnated with thermoset resin and cured using UV-light, woven commingled yarns made out of glass fibers and thermoplastic fibers which are locally heated and pressed, as well as pre-consolidated thermoplastic organo sheets which require selective heating for forming. General applicability of the processes is investigated and validated in practical experiments.
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Salem, David R. "Draw-Induced Structure Development in Flexible-Chain Polymers". In Structure Formation in Polymeric Fibers, 118–84. München: Carl Hanser Verlag GmbH & Co. KG, 2001. http://dx.doi.org/10.3139/9783446456808.004.
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Knudsen, Bodo E. "Flexible Ureteroscopy: Holmium:YAG Laser and Optical Fibers". In Ureteroscopy, 161–67. Totowa, NJ: Humana Press, 2012. http://dx.doi.org/10.1007/978-1-62703-206-3_14.
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Fukushima, Yasunori, Hiroki Murase e Yasuo Ohta. "Dyneema®: Super Fiber Produced by the Gel Spinning of a Flexible Polymer". In High-Performance and Specialty Fibers, 109–32. Tokyo: Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-55203-1_7.
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Koumbourlis, Anastassios C. "Flexible Fibre-Optic Bronchoscopy in the Intensive-Care Unit". In Paediatric Bronchoscopy, 54–63. Basel: KARGER, 2010. http://dx.doi.org/10.1159/000314384.
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Dufek, W., C. Sebesta, K. Schütze, E. Hentschel, H. Rosen e B. Bauer. "Submucous and Intravascular Application of Fibrin Sealant Using a Double-Luminal Flexible Needle". In Progress in Fibrin Sealing, 135–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-48362-2_16.
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Xiang, Dong. "Flexible Strain Sensors Based on Elastic Fibers of Conductive Polymer Composites". In Carbon-Based Conductive Polymer Composites, 113–25. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003218661-6.
Testo completoAtti di convegni sul tema "Fibres flexibles"
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Lammi, Tuulikki, e Annikki Heikkurinen. "Changes in Fibre Wall Structure during Defibration". In The Fundamentals of Papermaking Materials, a cura di C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1997. http://dx.doi.org/10.15376/frc.1997.1.641.
Testo completoAbstract (sommario):
Development of earlywood and latewood fibres was investigated to find out how morphologically different fibres undergo delamination. Fibre fractions rich in earlywood and latewood, were separated from mechanical pulps using a hydrocyclone and refined further in awing defibrator. Changes in fibre structure due to defibration were studied using microscopy techniques that included measurement of fibre stiffness, fibre wall thickness and external fibre surface. Before refining, the latewood fibres were stiff and their external fibre wallswere poorly developed. Refining reduced the stiffness of both fibre types. The stiffness of latewood fibres decreased to around that of unrefined earlywood fibres, andthe external walls of latewood fibres became fibrillated. The wall thickness of both earlywood and latewood fibres was reduced only slightly. Although the tensile and tear indices of sheets made of late wood fibres were improved by refining, the tensile index of flexible latewood fibres was only half of that measured for unrefined earlywood fibres. This indicates that there are fibre properties other than stiffness which must be changed in order to get latewood fibres to bond and conform properly.
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Ostoja-Starzewski, M., e D. C. Stahl. "Mechanics of Random Fiber Networks". In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1992.
Testo completoAbstract (sommario):
Abstract Paper has a multiscale structure, including a spectrum of features: macro-fluctuations (scale of tens, hundreds, thousands … of meters), streaks (scale of meters), flocs (scale of centimeters), single cellulose fibers (scale of millimeters), cellulose fiber being a composite helically wound from fibrils (scale of tens of microns), fibrils (submicron scale), and molecular chains (tens through thousands of Angstroms). This complexity is the root cause of various size-scale effects in mechanics (elasticity and strength) of paper. We outline a micromechanics model of paper which provides a bridge from the scale of interacting fibers to a statistical continuum approximation. The model accounts for a 3-D random geometry of fiber networks with any degree of fiber flocculation, and employs a Timoshenko beam with torsion for each fiber segment (between two contiguous fiber-fiber bonds). The fiber-fiber bonds are treated as either rigid or flexible. The model involves a computational mechanics of thousands of fibers, in which global failure occurs on microscale through fracture of a fiber segment and/or fracture of a fiber-fiber bond. We also report on the scale effects and statistics of effective mechanical (elastic and strength) responses due to a nonuniform paper formation.
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Berg, Arne, e Niels Jo̸rgen Risho̸j-Nielsen. "Integrity Monitoring of Flexible Risers by Optical Fibres". In ASME 2002 21st International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/omae2002-28088.
Testo completoAbstract (sommario):
The use of fibre optic sensing technology for integrity monitoring of flexible risers has been demonstrated. A technique for integration of the sensors along the tensile armouring has been developed and used in testing of a full-scale riser where the strain in the tensile armour was measured. The integration technique is also applicable to fibre optic sensors for other measurands. The test riser was exposed to a fatigue test of 612 000 bending cycles. The strain measurements provided new and important data about the conditions in the annulus of a riser during operation. The small diameter of optical fibres (OD = 0.125mm) and the multiplexing features of sensors based on fibre Bragg gratings (FBG) make it possible to realise various sensing systems in the riser annulus. A possible combination of different fibre optic sensors is outlined.
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Chen, Hongyu, Peter Wapperom e Donald G. Baird. "Simulation of Long Semi-Flexible Fiber Orientation During Injection Molding". In ASME 2016 11th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/msec2016-8577.
Testo completoAbstract (sommario):
Fiber orientation simulation is conducted for the Center-Gated-Disk (CGD) geometry and compared with experimental data. Long-fiber thermoplastic composites (LFTs) possess competitive advantages over short glass fiber composites in terms of their mechanical properties while retain the ability to be injection molded. Mechanical properties of LFTs are highly dependent on the microstructural variables imparted by the injection molding process including fiber orientation and fiber length distribution. As the fiber length increased, the mechanical properties of the composites containing discontinuous fibers can approach those of continuous fiber materials. Several researchers have reported that flexural, creep and charpy impact properties increase as fiber length increases, while tensile modulus will plateau for glass fibers above 1 mm in length. Fibers less than the 1 mm threshold have been considered to be short while fibers with lengths greater than 1 mm are considered long. For long fibers, they will have the ability to deform, bend and even break during any stage of polymer processing. There is a lack of knowledge about the effects of fiber length and fiber length variation on fiber orientation kinetics. This lack of information provides an opportunity to understand the length effect inherent to long fibers systems. The Bead-Rod fiber orientation model takes into account the flexibility of semi-flexible fibers that show small bending angles. In this model, a flexibility parameter representing the resistive bending potential is fiber length dependent (detailed explanation can be found in the reference)1. This work is concerned with the effect of fiber length on the performance of the Bead-Rod fiber orientation model which takes into account the flexibility of semi-flexible fibers. Different averaging techniques are used to represent the average fiber length for the population of fibers, which give different fiber length parameters for the Bead-Rod model. The sensitivity of the Bead-Rod model is evaluated with regard to the fiber flexibility parameter, k, and length parameter, lb. The other phenomenal parameters within the orientation model are obtained via basic rheological measurements using simple shear flow. As the value of average fiber length Lav increases and the corresponding flexibility parameter value decreases, the core regions become wider and the flow direction orientation gradually decreases especially near the walls for the Bead-Rod model predictions. In addition, as the parameters favor longer fiber lengths, the predicted extent of fiber bending increases. The simulation results are also compared with the experimental obtained fiber orientation at different flow length along the thickness direction. The Bead-Rod model shows improvement over the rigid rod model.
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Pillai, Sivaji, Thomas O. H. Charrett, Thomas Kissinger, James H. Barrington, Stephen W. James e Ralph P. Tatam. "Optical Fibre Based Angle Measurement for Robotic Joints". In Optical Fiber Sensors. Washington, D.C.: Optica Publishing Group, 2023. http://dx.doi.org/10.1364/ofs.2023.th6.82.
Testo completoAbstract (sommario):
Abstract: A multiplexed array of optical fibre based angle sensors for deployment on multiple joints of a robotic arm is demonstrated. Two optical fibres, each containing an array of fibre segment interferometers, are bonded either side of the neutral axis of a thin, flexible metal tape. Differential measurement of the phases of corresponding interferometers in the two fibres yields an angle measurement with resolution better than 0.001° over a bandwidth of 21 kHz when demodulated using the principles of range resolved interferometry.
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Da Costa Santos, Ana Caroline, e Paul Archbold. "Mechanical Properties and Fracture Energy of Concrete Beams Reinforced with Basalt Fibres". In 4th International Conference on Bio-Based Building Materials. Switzerland: Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/www.scientific.net/cta.1.316.
Testo completoAbstract (sommario):
Fibre-reinforced concrete (FRC) is widely employed in the construction industry, with assorted fibre types being used for different applications. Typically, steel fibres give additional tensile strength to the mixture, while flexible fibres may be used in large sections, such as floor slabs, to control crack width and to improve the handling ability of precast sections. For many reasons, including durability concerns, environmental impact, thermal performance, etc, alternatives to the currently available fibres are being sought. This study examines the potential of using basalt fibres, a mineral and natural material, as reinforcement of concrete sections in comparison to steel fibres and plain concrete mix. Mixes were tested containing 0.5% and 1.0% of basalt fibres measuring 25mm length, 0.5% of the same material with 48mm length and steel fibres measuring 50mm by 0.05%, 0.1%, 0.15% and 0.2% of the concrete volume. For the mechanical performance analysis, the 3-point bending test was led and the fracture energy, Young’s modulus and tensile strength in different moments of the tests were calculated. When compared to the control mixtures and the steel-fibre-reinforced concrete, the mixes containing basalt had a reduction in their elastic modulus, representing a decrease in the concrete brittleness. At the same time, the fracture energy of the mixtures was significantly increased with the basalt fibres in both lengths. Finally, the flexural strength was also higher for the natural fibre reinforced concrete than for the plain concrete and comparable to the results obtained with the addition of steel fibres by 0.15%.
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Görres, J., R. Amiri, M. Grondin e J. R. Wood. "Fibre Collapse and Sheet Structure". In Products of Papermaking, a cura di C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1993. http://dx.doi.org/10.15376/frc.1993.1.285.
Testo completoAbstract (sommario):
A stylus profilometer has been used to evaluate the effect of wet pressing on the collapse of individual fibres from mechanical, chemimechanical and chemical pulps. The chemimechanical and chemical pulp fibres begin to collapse at low pressures and approach complete collapse at high pressures, while the mechanical pulp fibres do not exceed 80% collapse to 5000 kPa. The degree of collapse of southern pine TMP at a given pressure is about the same as that of northeastern spruce/balsam TMP. Since the thick-walled Southern pine fibres are less flexible, it is concluded that transverse collapsibility and flexibility are two independent fibre properties. On the basis of modelling results and the difference between fibre thickness-measurement from networks pressed in contact with smooth and with rough surfaces, it is suggested that wet pressure transferred locally at fibre contacts within a sheet leads to local collapse forces higher- than expected from nominal wet pressure values. Fibre contacts are initially present in the unpressed sheet.On pressing, free fibre segments will be deflected into contact with other segments above or below them, producing additional fibre crossings as pressing progresses . The effective pressing pressure will be highest at the initial fibre contacts, decreasing to zero at contacts just formed at the end of pressing. Because of the demonstrated effect of wet pressure on fibre collapse, it is the thickness at the initial fibre contacts or those formed early in the pressing process that is important in determining sheet density. Use of the more appropriate fibre thicknesses, substantially improves the prediction of sheet density by the Interactive Multiplanar Model of sheet structure for a range of pulp types.
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Ellis, A. D., e D. M. Spirit. "The use of GaInAsP amplifiers for 40 Gbit/s signal processing." In Nonlinear Guided-Wave Phenomena. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/nlgwp.1993.pd.2.
Testo completoAbstract (sommario):
Optical time domain multiplexed (OTDM) systems are expected to play an important role in increasing the aggregate fibre capacity in telecommunications networks beyond the levels attainable with electronic systems. Within these systems, one of the key elements is a flexible optical demultiplexer, and recently attention has been focused on the use of the Kerr effect in silica based fibres to produce optically controlled switching elements1,2. However, whilst offering attractive functionality, the relatively low nonlinear coefficientin silica fibres leads to excessively long devices and consequent latency, timing and stability issues. It is also necessary to carefully select the fibre properties and signal wavelengths for these switches to achieve a desired function. Thus a compact sub millimetre device, offering similar overall levels of nonlinearity offers clear advantages.
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Wang, Ranran, Yin Cheng e Jing Sun. "Smart Fibers Based on Low Dimensional Conductive Materials". In 2018 International Flexible Electronics Technology Conference (IFETC). IEEE, 2018. http://dx.doi.org/10.1109/ifetc.2018.8583915.
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Qu, Yunpeng, Tung Nguyen-Dang, Alexis Gerald Page, Wei Yan, Tapajyoti Das Gupta, Gelu Marius Rotaru, Rene M. Rossi, Valentine Dominique Favrod, Nicola Bartolomei e Fabien Sorin. "Stretchable Optical and Electronic Fibers via Thermal Drawing". In 2018 International Flexible Electronics Technology Conference (IFETC). IEEE, 2018. http://dx.doi.org/10.1109/ifetc.2018.8583875.
Testo completoRapporti di organizzazioni sul tema "Fibres flexibles"
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McKeehan, K. Composite molding of SPECTRA{reg_sign} extended chain polyethylene fibers in a flexible rubber matrix. Office of Scientific and Technical Information (OSTI), agosto 1997. http://dx.doi.org/10.2172/653949.
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Siebenaler, Shane. PR-015-163766-R01 Field Testing of Distributed Acoustic Sensing Systems. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), luglio 2018. http://dx.doi.org/10.55274/r0011503.
Testo completoAbstract (sommario):
Distributed acoustic sensing (DAS) technology utilizes a fiber-optic cable as a distributed vibration sensor that can be installed in a right-of-way to monitor for pipeline leaks and to identify third-party interference (TPI), such as mechanized excavation, hand digging, etc. Various laboratory tests have been performed to demonstrate that DAS has the potential to be a flexible solution for pipeline operators. A key gap that needs to be assessed is the ability of the technology to serve its intended leak detection and TPI functions while not generating alarms at any other times. The most comprehensive means of performing such an evaluation is through an actual field demonstration of DAS technology on an operational pipeline. This report documents a ten-week-long test of four commercially available DAS technologies on an operational pipeline. The pipeline segment is 25-kilometers in length, and the systems were configured to autonomously alarm to leaks and mechanical digging. This research demonstrates the real-world performance of such systems and provides qualitative information in regards to the operational requirements for sustained deployment of DAS technology. This document has a related webinar. (member login required)
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AN ANALYTICAL METHOD FOR EVALUATING THE DEFLECTION AND LOAD-BEARING AND ENERGY ABSORPTION CAPACITY OF ROCKFALL RING NETS CONSIDERING MULTIFACTOR INFLUENCE. The Hong Kong Institute of Steel Construction, settembre 2022. http://dx.doi.org/10.18057/ijasc.2022.18.3.1.
Testo completoAbstract (sommario):
In this study, an analytical method for evaluating the structural performance, including maximum deflection, load-bearing, and energy absorption capacity of a steel wire-ring net, was proposed to effectively design the ring net of the flexible barrier systems. Puncture tests of the ring nets and two-point traction tests of the three-ring chains with various wire-ring specifications were conducted. Correlation analysis was used to test the results between ring nets and chains, revealing that three structural performance indicators of the test specimens were strongly related. The ring net’s structural performance was affected specifically by ring chains on the shortest load transfer path. Accordingly, a three-ring chain with a flexible boundary corresponded to a fibre–spring element. A three-dimensional analytical model of the ring net was established. Explicit formulas for computing the three indicators of the ring net were derived. Comprehensive quasi-static and impact tests, using different shapes and sizes of punching devices, were conducted, providing valuable data to calibrate and validate this analytical method. The ability of the model in yielding consistent results when implemented at the structure scale was then assessed, based on the data of full-scale impact tests on a 1500kJ-energy rockfall barrier. Lastly, the effects of various factors, such as single ring geometry, the length–width ratio of the net, loading area size, boundary stiffness, and load rate, influencing the structural performance indicators of the ring net were investigated, respectively.