226 research outputs found

    Homogenized yarn-level cloth

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    We present a method for animating yarn-level cloth effects using a thin-shell solver. We accomplish this through numerical homogenization: we first use a large number of yarn-level simulations to build a model of the potential energy density of the cloth, and then use this energy density function to compute forces in a thin shell simulator. We model several yarn-based materials, including both woven and knitted fabrics. Our model faithfully reproduces expected effects like the stiffness of woven fabrics, and the highly deformable nature and anisotropy of knitted fabrics. Our approach does not require any real-world experiments nor measurements; because the method is based entirely on simulations, it can generate entirely new material models quickly, without the need for testing apparatuses or human intervention. We provide data-driven models of several woven and knitted fabrics, which can be used for efficient simulation with an off-the-shelf cloth solver

    Mechanical characterization of rigid discrete interlocking materials

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    Les matériaux discrets entrecroisés (DIM) rigides sont une classe de matériaux qui se distinguent par la manière unique par laquelle ils se déforment: les DIMs sont composés d’éléments (connectés par entrecroisements) qui peuvent se déplacer librement à l’intérieur d’une amplitude définie par les contacts avec leurs éléments voisins. Ceci donne une réponse biphasique aux déformations unique à ces structures où soit aucune résistance n’est fournie à une déformation, soit un arrêt complet à la déformation se présente. Il n’est pas clair comment l’ensemble de paramètres discrets et continus décrivant un DIM influence ce comportement biphasique. De plus, nous ne possédons pas les outils pour le charactériser correctement. Dans le but d’élucider ce comportement, nous présentons une méthode qui s’inspire de techniques d’homogénisation qui peut détecter les contacts physiques entre éléments composés de tores. En définissant une énergie adéquate, nous pouvons minimiser les intersections entre éléments tout en déformant le DIM d’une façon arbitraire en utilisant des techniques d’optimisation standardes. Nous explorons les déformations auxquelles des arrangements planaires de DIMs peuvent être assujettis et investiguons comment le couplage de contraintes dans deux directions orthogonales influence ces déformations. Nos résultats permettent de mieux comprendre comment différents paramètres décrivant un DIM influence ces déformations.Rigid discrete interlocking materials (DIMs) are a class of materials that distinguish themselves by the unique way in which they deform: in DIMs, elements (connected through interlocking) can move freely within a range defined through contacts with neighbouring elements. This results in a biphasic deformation behaviour unique to these structures where no resistance is provided to deformation or a hard stop to deformation is met. It is yet unclear how the set of discrete and continuous parameters describing a DIM influences this biphasic behaviour. Likewise, we lack tools to properly characterize it. To that effect, we present a method which takes inspiration from homogenization and handles contacts by leveraging the definition of implicit surfaces, specifically tori, making up our elements. By defining an adequate energy function, we can minimize intersection between elements while deforming the DIM in an arbitrary way using standard optimization approaches. We explore the deformations that planar sheets of DIM can be subjected to and investigate how the coupling of constraints in two orthogonal directions affects these deformations. Our results give insights on how the tuning of various parameters describing the DIM affects these deformations

    Characterizing and predicting the self-folding behavior of weft-knit fabrics

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    This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this recordSelf-folding behavior is an exciting property of weft knit fabrics that can be created using just front and back stitches. This behavior is easy to create, but not easy to anticipate and currently cannot be predicted by existing computer aided design (CAD) software that controls the CNC knitting machines. This work identifies the edge deformation behaviors that lead to self-folding in weft knits, and methods to characterize the mechanical forces driving these behaviors with regard to chosen manufacturing parameters. With this data and analysis of the fabric deformations, the self-folding behavior was purposely controlled using calculated scaling factors. Furthermore, theoretical equations were developed to mathematically predict these scaling factors, minimizing the trial and error required to design with self-folding behavior and create textiles with novel engineered properties. By understanding the mechanisms responsible for creating these threedimensional self-folding textiles, they can then be designed in a programmable manner for use in technical applications.National Science FoundationUS Army Manufacturing Technology Program (US Army DEVCOM

    FRAME MODEL OF UNIAXIAL STRETCHING OF 1x1 RIB KNITS

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    One of the nowadays challenges is the development of scientific sound models of knitwear deformations. The paper is devoted to developing an algorithm for constructing a frame model of rib 1x1 knits stretched in the course or wale direction. In the process of uniaxial stretching, the shape of the sample depends on the tensile forces orientation. A frame model of a deformed knitted structure, and an algorithm of construction of a mesh frame, are developed during the study. The frame model makes it possible to find coordinates of intermeshing points of every stitch. Then yarn characteristic points can be determined that, in turn, serve as input data for the construction of 3D model of rib 1x1 structure under uniaxial tensile deformations at the yarn level of detail. The study provides a graphical tool for formalization of geometric transformation that happen during 2D deformations of knitted structures, characterized by gradual change of the specimens width crosswise to the loading direction. This model is intended to become a part of a general deformation model of knitted fabrics

    Exploring expressive and functional capacities of knitted textiles exposed to wind influence

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    This study explores the design possibilities with knitted architectural textiles subjected to wind. The purpose is to investigate how such textiles could be applied to alter the usual static expression of exterior architectural and urban elements, such as\ua0facades\ua0and windbreaks. The design investigations were made on a manual knitting machine and on a CNC (computer numerically controlled)\ua0flat knitting machine. Four knitting techniques -\ua0tuck stitch, hanging stitches, false lace, and drop stitch - were explored based on their ability to create a three-dimensional effect on the surface level as well as on an architectural scale. Physical textile samples produced using those four techniques were subjected to controlled action of airflow. Digital experiments were also conducted, to probe the possibilities of digitally simulating textile behaviours in wind. The results indicate that especially the drop stitch technique exhibits interesting potentials. The variations in the drop stitch pattern generate both an aesthetic effect of volumetric expression of the textile architectural surface and seem beneficial in terms of wind speed reduction. Thus, these types of knitted textiles could be applied to design architecture that are efficient in terms of improving the aesthetic user experience and comfort in windy urban areas

    STUDY OF RIB KNITS COURSEWISE TENSILE PROCESS

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    Stretchability of knitwear is one of the most important factors of wearing comfort. Elasticity of knitted structures in course wise direction is usually higher than along wales and often characterized by crosswise shrinkage. Existing methods of knitting program development do not consider the real rate of wale wise shrinkage of rib knitted structure under the course wise extension. During the study experimental research has been carried out to fulfill empirical data on the relationship between samples’ length and width under uniaxial course wise elongation. A range of samples of rib 1×1, 2×2, 3×3, 4×4 and 5×5 knits, made of cotton, bamboo, polyacrylonitrile (PAN), wool/acrylic blend and wool yarn, were stretched with a tensile machine WDW-05M. In the process of stretching the width of each specimen was defined in the moments of extension by 50, 100, 150, 200, 250 and 300 per cent. It has been found that linear approximation can be applied to describe the dependence of specimen’s width on its relative course wise elongation. It was found that the stitch height/width ratio changes unevenly. In the beginning of the process of course wise stretching of a rib knitted structure, it does exist, such an interval, where an increase of the knit’s linear size along the courses occurs without a significant shrinkage in the wale wise direction. It is suggested to name the upper limit of this interval as “unidimensional extension limit” and define it as an extension of a standard (100×50mm) specimen, at which its width decreases by 10%. It was found as well that the value of this index significantly depends on the ribbing variation and much less on the type of raw materials

    Textile architecture informed by wind

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    Textiles in architecture is a field of great potential, which are worth to explore further. This thesis aims to show that the flexibility of the textile material could be better included in the architectural design, allowing it to adapt to forces, such as the wind, and viewing motion as a positive design feature. The main methods for this were a literature study and design investigations, using physical as well as digital prototypes, with extra focus on the material flexibility and knitted textiles. The field textile architecture informed by wind is defined through three main components: the textile material, the lightweight structure, and the wind. Textiles are, here, seen as a material with structural and aesthetical flexibility and diversity that can adapt to as well as carry applied loads. Lightweight structures are concepts for material efficiency and structural elegance. And, wind informed architecture is the concept of including the phenomena of wind in the architectural design, as a free source of energy or force that could be used, absorbed, or directed to create beauty and to form a more comfortable environment. The core of the thesis lies in the overlap of these three components. Results from this thesis indicate, firstly, that the field of textile architecture informed by wind is relatively uncharted territory. Knowledge and inspiration can, however, be found outside the field of architecture, such as performing arts, art installations, sailing, and fashion. Secondly, opportunities for supporting the, often complicated, design process of textile architecture are demonstrated through the use of a combination of digital models and physical prototypes, in the presented examples
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