Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session B44: Focus Session: Extreme Mechanics: Origami, Kirigami and Mechanisms II |
Hide Abstracts |
Sponsoring Units: GSNP GSOFT DPOLY Room: 214D |
Monday, March 2, 2015 11:15AM - 11:27AM |
B44.00001: Unravelling Origami Metamaterial Behavior Maryam Eidini, Glaucio Paulino Origami has shown to be a substantial source of inspiration for innovative design of mechanical metamaterials for which the material properties arise from their geometry and structural layout. Most research on origami-inspired materials relies on known patterns, especially on classic Miura-ori pattern. In the present research, we have created origami-inspired metamaterials and we have shown that the folded materials possess properties as remarkable as those of Miura-ori on which there is a lot of recent research. We have also introduced and placed emphasis on several important concepts that are confused or overlooked in the literature, e.g. concept of planar Poisson's ratio for folded materials from different conceptual viewpoints, and we have clarified the importance of such concepts by applying them to the folded sheet metamaterials introduced in our research. The new patterns are appropriate for a broad range of applications, from mechanical metamaterials to deployable and kinetic structures, at both small and large scales. [Preview Abstract] |
Monday, March 2, 2015 11:27AM - 11:39AM |
B44.00002: Origami Mechanics: Bistability and Isometries Mokhtar Adda-Bedia, Frederic Lechenault Origami structures are usually seen as assemblies of rigid faces articulated around creases with hinge-like behaviour. Their deployment and degrees of freedom are purely kinematic, resulting only from the geometry of the crease network. However, in real folded structures, the base material can deform outside the creases. In such situations, face bending competes with crease actuation in a morphogenetic way. In order to rationalise this interplay, we investigate the mechanical behaviour of an infinite sheet on which one or more straight creases meet at a single vertex. We find that these structures generically exhibit bistability, in the sense that they can snap through from one metastable configuration to another. Furthermore, we uncover a new class of isometry of the plane, which corresponds to metastable states of a creased sheet for which the hoop stress vanishes, an instability mechanism that is also responsible for the wrinkling of thin plates. [Preview Abstract] |
Monday, March 2, 2015 11:39AM - 11:51AM |
B44.00003: ABSTRACT WITHDRAWN |
Monday, March 2, 2015 11:51AM - 12:27PM |
B44.00004: Topological mechanics: from metamaterials to active matter Invited Speaker: Vincenzo Vitelli Mechanical metamaterials are artificial structures with unusual properties, such as negative Poisson ratio, bistability or tunable acoustic response, which originate in the geometry of their unit cell. At the heart of such unusual behavior is often a mechanism: a motion that does not significantly stretch or compress the links between constituent elements. When activated by motors or external fields, these soft motions become the building blocks of robots and smart materials. In this talk, we discuss topological mechanisms that possess two key properties: (i) their existence cannot be traced to a local imbalance between degrees of freedom and constraints (ii) they are robust against a wide range of structural deformations or changes in material parameters. The continuum elasticity of these mechanical structures is captured by non-linear field theories with a topological boundary term similar to topological insulators and quantum Hall systems. We present several applications of these concepts to the design and experimental realization of 2D and 3D topological structures based on linkages, origami, buckling meta-materials and lastly active media that break time-reversal symmetry. [Preview Abstract] |
Monday, March 2, 2015 12:27PM - 12:39PM |
B44.00005: Critical transition to bistability arising from hidden degrees of freedom in origami structures Itai Cohen, Jesse Silverberg, Jun-Hee Na, Arthur Evans, Bin Liu, Thomas Hull, Christian Santangelo, Robert Lang, Ryan Hayward Origami, the traditional art of paper folding, is now being used to design responsive, dynamic, and customizable mechanical metamaterials. The remarkable abilities of these origami-inspired devices emerge from a predefined crease pattern, which couples kinematic folding constraints to the geometric placement of creases. In spite of this progress, a generalized physical understanding of origami remains elusive due to the challenge in determining whether local kinematic constraints are globally compatible, and an incomplete understanding of how bending and crease plasticity found in real materials contribute to the overall mechanical response. Here, we show experimentally and theoretically that the traditional \textit{square twist}, whose crease pattern has zero degrees of freedom (DOF) and therefore should not be foldable, is nevertheless able to be folded by accessing higher energy scale deformations associated with bending. Due to the separation of bending and crease energy scales, these hidden DOF lead to a geometrically-driven critical bifurcation between mono- and bistability. The scale-free geometric underpinnings of this physical phenomenon suggest a generalized design principle that can be useful for fabricating micro- and nanoscale mechanical switches. [Preview Abstract] |
Monday, March 2, 2015 12:39PM - 12:51PM |
B44.00006: A probabilistic approach to randomness in geometric configuration of scalable origami structures Ke Liu, Glaucio Paulino, Paolo Gardoni Origami, an ancient paper folding art, has inspired many solutions to modern engineering challenges. The demand for actual engineering applications motivates further investigation in this field. Although rooted from the historic art form, many applications of origami are based on newly designed origami patterns to match the specific requirenments of an engineering problem. The application of origami to structural design problems ranges from micro-structure of materials to large scale deployable shells. For instance, some origami-inspired designs have unique properties such as negative Poisson ratio and flat foldability. However, origami structures are typically constrained by strict mathematical geometric relationships, which in reality, can be easily violated, due to, for example, random imperfections introduced during manufacturing, or non-uniform deformations under working conditions (e.g. due to non-uniform thermal effects). Therefore, the effects of uncertainties in origami-like structures need to be studied in further detail in order to provide a practical guide for scalable origami-inspired engineering designs. Through reliability and probabilistic analysis, we investigate the effect of randomness in origami structures on their mechanical properties. Dislocations of vertices of an origami structure have different impacts on different mechanical properties, and different origami designs could have different sensitivities to imperfections. Thus we aim to provide a preliminary understanding of the structural behavior of some common scalable origami structures subject to randomness in their geometric configurations in order to help transition the technology toward practical applications of origami engineering. [Preview Abstract] |
Monday, March 2, 2015 12:51PM - 1:03PM |
B44.00007: Exponential Number of Shapes in Origami Metasheets Peter Dieleman, Scott Waitukaitis, Martin van Hecke The simplest possible fold pattern that allows for motion, the 4-vertex, has two distinct branches of motion. By deriving a local combinatorial rule, we show that the number of branches in a tessellated sheet of such 4-vertices grows exponentially with the number of vertices. We introduce energy in the system by approximating the folds as torsional springs and show that we can create an arbitrary number of well separated minima, i.e. shapes. With 3D printing, we bring these shape-shifting structures to life. [Preview Abstract] |
Monday, March 2, 2015 1:03PM - 1:15PM |
B44.00008: Topological modes bound to lattice dislocations in mechanical metamaterials Jayson Paulose, Bryan Chen, Vincenzo Vitelli The mechanical rigidity of frameworks -- nodes connected by springs or rigid bars -- underlies the structural integrity of bridges, the response of granular materials, and the design of metamaterials with unusual mechanical properties. A fundamental question governing rigidity is the existence of mechanisms: motions that do not significantly stretch or compress the constituent elements of the structure. We demonstrate a novel way to introduce approximate mechanisms at desired locations in a metamaterial, by exploiting the properties of a recently introduced class of topological metamaterials. These are special periodic frameworks which exhibit localized edge modes, analogous to the electronic edge states of topological insulators. We show that dislocations in such metamaterials are associated with soft modes of topological origin. The existence of the modes is determined by the interplay between two Berry phases -- the Burgers vector of the dislocation and a topological ``polarization'' characterizing the underlying lattice. Simple prototypes built out of triangular plates joined by hinges provide a visual demonstration of these modes. [Preview Abstract] |
Monday, March 2, 2015 1:15PM - 1:27PM |
B44.00009: Wave Propagation in Origami-inspired Foldable Metamaterials Pai Wang, Sijie Sun, Katia Bertoldi We study the propagation of elastic waves in foldable thin-plate structures. Both 1D systems of periodic folds and 2D Miura-Ori patterns are investigated. The dispersion relations are calculated by finite element simulations on the unit cell of spatial periodicity. Experimental efforts and considerations are also discussed. The characteristic propagating bands and bandgaps are found to be very sensitive to the folding angles. The existence of highly tunable bandgap makes the system suitable for potential applications including adaptive filters in vibration-reduction devices, wave guides and acoustic imaging equipment. [Preview Abstract] |
Monday, March 2, 2015 1:27PM - 1:39PM |
B44.00010: Quantification of a Helical Origami Fold Eric Dai, Xiaomin Han, Zi Chen Origami, the Japanese art of paper folding, is traditionally viewed as an amusing pastime and medium of artistic expression. However, in recent years, origami has served as a source of inspiration for innovations in science and engineering. Here, we present the geometric and mechanical properties of a twisting origami fold. The origami structure created by the fold exhibits several interesting properties, including rigid foldibility, local bistability and finely tunable helical coiling, with control over pitch, radius and handedness of the helix. In addition, the pattern generated by the fold closely mimics the twist buckling patterns shown by thin materials, for example, a mobius strip. We use six parameters of the twisting origami pattern to generate a fully tunable graphical model of the fold. Finally, we present a mathematical model of the local bistability of the twisting origami fold. Our study elucidates the mechanisms behind the helical coiling and local bistability of the twisting origami fold, with potential applications in robotics and deployable structures. [Preview Abstract] |
Monday, March 2, 2015 1:39PM - 1:51PM |
B44.00011: Associative memory through rigid origami Arvind Murugan, Michael Brenner Mechanisms such as Miura Ori have proven useful in diverse contexts since they have only one degree of freedom that is easily controlled. We combine the theory of rigid origami and associative memory in frustrated neural networks to create structures that can ``learn'' multiple generic folding mechanisms and yet can be robustly controlled. We show that such rigid origami structures can ``recall'' a specific learned mechanism when induced by a physical impulse that only need resemble the desired mechanism (i.e. robust recall through association). Such associative memory in matter, seen before in self-assembly, arises due to a balance between local promiscuity (i.e., many local degrees of freedom) and global frustration which minimizes interference between different learned behaviors. Origami with associative memory can lead to a new class of deployable structures and kinetic architectures with multiple context-dependent behaviors. [Preview Abstract] |
Monday, March 2, 2015 1:51PM - 2:03PM |
B44.00012: Hiding the weakness: structural robustness using origami design Bin Liu, Christian Santangelo, Itai Cohen A non-deformable structure is typically associated with infinitely stiff materials that resist distortion. In this work, we designed a structure with a region that will not deform even though it is made of arbitrarily compliant materials. More specifically, we show that a foldable sheet with a circular hole in the middle can be deformed externally with the internal geometry of the hole unaffected. Instead of strengthening the local stiffness, we fine tune the crease patterns so that all the soft modes that can potentially deform the internal geometry are not accessible through strain on the external boundary. The inner structure is thus protected by the topological mechanics, based on the detailed geometry of how the vertices in the foldable sheet are connected. In this way, we isolate the structural robustness from the mechanical properties of the materials, which introduces an extra degree of freedom for structural design. [Preview Abstract] |
Monday, March 2, 2015 2:03PM - 2:15PM |
B44.00013: Untangling the mechanics versus topology of overhand knots Pedro Reis, Mohammad Jawed, Peter Dieleman, Basile Audoly We study the interplay between mechanics and topology of overhand knots in slender elastic rods. We perform precision desktop experiments of overhand knots with increasing values for the crossing number (our measure of topology) and characterize their mechanical response through tension-displacement tests. The tensile force required to tighten the knot is governed by an intricate balance between topology, bending, friction, and contact forces. Digital imaging is employed to characterize the configuration of the contact braid as a function of crossing number. A robust scaling law is found for the pulling force in terms of the geometric and topological parameters of the knot. A reduced theory is developed, which predictively rationalizes the process. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700