Tunable Wave Dynamics in Origami-Based Mechanical Metamaterials

2016 ◽  
Author(s):  
Hiromi Yasuda ◽  
Mia Lee ◽  
Jinkyu Yang
Keyword(s):  
Geometrical Parameters ◽  
Wave Dynamics ◽  
Mechanical Metamaterials ◽  
Mechanical Waves ◽  
1D Chain ◽  
Unit Cells ◽  
A Chain ◽  
Tunable Frequency ◽  
Relationship Of ◽  
The Given

We investigate unique wave dynamics in origami-based mechanical metamaterials composed of volumetric 3D origami unit cells. Specifically, we assemble a chain of lattice structures, in which the Tachi-Miura Polyhedron (TMP) is employed as a building block. We conduct two types of theoretical/computational analysis on this origami-based system. One is the dynamic analysis on the TMP unit cell under harmonic excitations. We find that the system transits from linear to nonlinear regimes or vice versa, depending on the amplitude of the excitation and the initial configurations of the given geometry. This implies that the origami-based system exhibits intrinsic tun-ability of its dynamic behavior by altering these excitation and geometrical parameters. The other analysis is on a dispersion relationship of mechanical waves propagating through the lattice. We analyze a 1D chain of (i) all identical TMP unit cells and (ii) two different unit cells in an alternating arrangement. From this analysis, we show that the origami-based system can create tunable frequency band structures by changing geometrical parameters. By leveraging these unique, tunable wave dynamics, the origami-based mechanical systems have great potential to be used as novel engineering devices that are capable of handling vibrations and impact efficiently.

Simultaneous energy harvesting and vibration attenuation in piezo-embedded negative stiffness metamaterial

2020 ◽  
Vol 31 (8) ◽  
pp. 1076-1090 ◽  
Author(s):  
Ankur Dwivedi ◽  
Arnab Banerjee ◽  
Bishakh Bhattacharya
Keyword(s):  
Energy Harvesting ◽  
Negative Stiffness ◽  
Engineering Properties ◽  
Mechanical Metamaterials ◽  
Analytical Simulation ◽  
Vibration Attenuation ◽  
Unit Cells ◽  
Parametric Studies ◽  
A Chain ◽  
Bloch’S Theorem

Mechanical metamaterials are uniquely engineered form of periodically arranged unit cells that exhibit interesting frequency-dependent physical properties like negative effective mass, Young’s modulus and Poisson’s ratio. These extreme engineering properties are beyond the natural properties of a material, which can modulate the propagation of wave. In this article, a mechanical realization of one of these uncommon properties called negative stiffness is emulated through analytical simulation. Wave propagation in metamaterials is contingent on frequency, which in turn results in transmission and attenuation bands. Simultaneous vibration control and energy harvesting can be executed by embedding energy harvesting smart material within the resonating units of the metamaterial. However, this needs careful design studies to outline the range of parameters. In this work, first, the band structure of a piezo-embedded negative stiffness metamaterial is studied using generalized Bloch’s theorem. Subsequently, harvested power along with the transmissibility is computed for a chain of finite number of metamaterial units by using backward substitution method. The results of the parametric studies elucidate that piezo-embedded negative stiffness metamaterial can enhance the performance in terms of vibration attenuation and harvested energy.

Wave Dynamics in Reconfigurable Tristable Mechanical Metamaterials

2019 ◽  
Author(s):  
Hiromi Yasuda ◽  
Lucia M. Korpas ◽  
Jordan R. Raney
Keyword(s):  
Band Gap ◽  
Stable State ◽  
Topological Properties ◽  
Wave Localization ◽  
Wave Dynamics ◽  
Mechanical Metamaterials ◽  
New Strategy ◽  
A Chain ◽  
Reconfigurable Structures ◽  
Interface Mode

Abstract We explore unique wave dynamics in a chain of tristable structures, inspired by multistable origami. We specifically focus on the frequency band structure of the chain, and conduct numerical and theoretical analysis. The band gap of the chain can be controlled by switching the stable state of each tristable structure. We also show that if two regions of the chain have different topological properties then wave localization can occur at the interface of the two regions. Interestingly, this interface mode is observed within the band gap. We demonstrate that the interface mode can be altered by leveraging the reconfigurable nature of the tristable structure. Our findings suggest a new strategy for controlling wave propagation in reconfigurable structures, which could be relevant for engineering applications such as energy harvesting.

scholarly journals Hierarchical mechanical metamaterials built with scalable tristable elements for ternary logic operation and amplitude modulation

2021 ◽  
Vol 7 (9) ◽  
pp. eabf1966
Author(s):  
Hang Zhang ◽  
Jun Wu ◽  
Daining Fang ◽  
Yihui Zhang
Keyword(s):  
Structural Diversity ◽  
Cell Number ◽  
Structural Elements ◽  
Ternary Logic ◽  
Stable States ◽  
One Dimensional ◽  
Logic Operation ◽  
Artificial Materials ◽  
Mechanical Metamaterials ◽  
Unit Cells

Multistable mechanical metamaterials are artificial materials whose microarchitectures offer more than two different stable configurations. Existing multistable mechanical metamaterials mainly rely on origami/kirigami-inspired designs, snap-through instability, and microstructured soft mechanisms, with mostly bistable fundamental unit cells. Scalable, tristable structural elements that can be built up to form mechanical metamaterials with an extremely large number of programmable stable configurations remains illusive. Here, we harness the elastic tensile/compressive asymmetry of kirigami microstructures to design a class of scalable X-shaped tristable structures. Using these structure as building block elements, hierarchical mechanical metamaterials with one-dimensional (1D) cylindrical geometries, 2D square lattices, and 3D cubic/octahedral lattices are designed and demonstrated, with capabilities of torsional multistability or independent controlled multidirectional multistability. The number of stable states increases exponentially with the cell number of mechanical metamaterials. The versatile multistability and structural diversity allow demonstrative applications in mechanical ternary logic operators and amplitude modulators with unusual functionalities.

Prediction of internal geometry and tensile behavior of 3D woven solid structures by mathematical coding

2021 ◽  
pp. 152808372110013
Author(s):  
Vivek R Jayan ◽  
Lekhani Tripathi ◽  
Promoda Kumar Behera ◽  
Michal Petru ◽  
BK Behera
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Areal Density ◽  
Woven Fabrics ◽  
Tensile Behavior ◽  
Geometrical Parameters ◽  
Fiber Volume ◽  
Acceptable Error ◽  
Internal Geometry ◽  
Unit Cells

The internal geometry of composite material is one of the most important factors that influence its performance and service life. A new approach is proposed for the prediction of internal geometry and tensile behavior of the 3 D (three dimensional) woven fabrics by creating the unit cell using mathematical coding. In many technical applications, textile materials are subjected to rates of loading or straining that may be much greater in magnitude than the regular household applications of these materials. The main aim of this study is to provide a generalized method for all the structures. By mathematical coding, unit cells of 3 D woven orthogonal, warp interlock and angle interlock structures have been created. The study then focuses on developing code to analyze the geometrical parameters of the fabric like fabric thickness, areal density, and fiber volume fraction. Then, the tensile behavior of the coded 3 D structures is studied in Ansys platform and the results are compared with experimental values for authentication of geometrical parameters as well as for tensile behavior. The results show that the mathematical coding approach is a more efficient modeling technique with an acceptable error percentage.

Failure Mechanisms of Particulate Two-Phase Composites

1998 ◽  
Vol 529 ◽  
Author(s):  
T. Antretter ◽  
E D. Fischer
Keyword(s):  
Residual Stresses ◽  
Crack Growth ◽  
Opening Angle ◽  
Geometrical Parameters ◽  
Two Phase ◽  
Absolute Size ◽  
The Matrix ◽  
Unit Cells ◽  
Angle Criterion ◽  
Probability Of Fracture

AbstractIn many composites consisting of hard and brittle inclusions embedded in a ductile matrix failure can be attributed to particle cleavage followed by ductile crack growth in the matrix. Both mechanisms are significantly sensitive towards the presence of residual stresses.On the one hand particle failure depends on the stress distribution inside the inclusion, which, in turn, is a function of various geometrical parameters such as the aspect ratio and the position relative to adjacent particles as well as the external load. On the other hand it has been observed that the absolute size of each particle plays a role as well and will, therefore, be taken into account in this work by means of the Weibull theory. Unit cells containing a number of quasi-randomly oriented elliptical inclusions serve as the basis for the finite element calculations. The numerical results are then correlated to the geometrical parameters defining the inclusions. The probability of fracture has been evaluated for a large number of inclusions and plotted versus the particle size. The parameters of the fitting curves to the resulting data points depend on the choice of the Weibull parameters.A crack tip opening angle criterion (CTOA) is used to describe crack growth in the matrix emanating from a broken particle. It turns out that the crack resistance of the matrix largely depends on the distance from an adjacent particle. Residual stresses due to quenching of the material tend to reduce the risk of particle cleavage but promote crack propagation in the matrix.

scholarly journals MULTIPARAMETRIC OPTIMIZATION OF THE SHAPE AND THICKNESS OF INSULATED ENERGY EFFICIENT CONSTRUCTED BUILDING WITH A SPECIFIC NUMBER OF FACES

2021 ◽  
pp. 196-204
Author(s):  
Viacheslav Martynov
Keyword(s):  
Energy Efficiency ◽  
Energy Efficient ◽  
Heat Losses ◽  
Geometrical Parameters ◽  
Energy Efficient Buildings ◽  
Multiparametric Optimization ◽  
Heat Influx ◽  
Number Of Faces ◽  
The Given ◽  
First Time

To calculate the optimal parameters of outbuildings, a mathematical model and method for optimizing the shape and resistance of heat transfer for opaque and transparent structures with a certain constant number of faces, building volume and amount of insulation to minimize the thermal balance of enclosing structures with the environment during the heating period In the course of calculations the geometrical parameters of translucent, opaque structures in the heat-insulating shell of buildings are determined taking into account heat losses, heat influx from solar radiation by the criterion of ensuring minimum heat losses through enclosing structures, rational parameters (buildings) The given technique and mathematical models should be used in the future in the design of energy efficient buildings in the reconstruction and thermal modernization of buildings. This will increase their energy efficiency and, accordingly, the energy efficiency class of buildings. For the research faceted attached building in the form of a triangular pyramid, the reduction in heat loss was 14.82 percent only due to the optimization of the shape and redistribution of the insulation. Similar results were obtained for other initial forms. For the first time, a computerized method was proposed, an algorithm and application package Optimparam for multiparameter shape optimization and insulation of translucent and opaque structures for outbuildings with a given number of arbitrarily arranged faces were developed.

scholarly journals Chemo-mechanical Diffusion Waves Orchestrate Collective Dynamics of Immune Cell Podosomes

2021 ◽  
Author(s):  
Ze Gong ◽  
Koen van den Dries ◽  
Alessandra Cambi ◽  
Vivek Shenoy
Keyword(s):  
Actin Polymerization ◽  
Immune Cell ◽  
Wave Dynamics ◽  
Diffusion Waves ◽  
Mechanical Diffusion ◽  
Mechanical Waves ◽  
The Individual ◽  
The Impact ◽  
Cell Mechanosensing

Immune cells, such as macrophages and dendritic cells, can utilize podosomes, actin-rich protrusions, to generate forces, migrate, and patrol for foreign antigens. In these cells, individual podosomes exhibit periodic protrusion and retraction cycles (vertical oscillations) to probe their microenvironment, while multiple podosomes arranged in clusters demonstrate coordinated wave-like spatiotemporal dynamics. However, the mechanisms governing both the individual vertical oscillations and the coordinated oscillation waves in clusters remain unclear. By integrating actin polymerization, myosin contractility, actin diffusion, and mechanosensitive signaling, we develop a chemo-mechanical model for both the oscillatory growth of individual podosomes and wave-like dynamics in clusters. Our model reveals that podosomes show oscillatory growth when the actin polymerization-associated protrusion and the signaling-associated myosin contraction occur at similar rates, while the diffusion of actin monomers within the cluster drives mesoscale coordination of individual podosome oscillations in an apparent wave-like fashion. Our model predicts the influence of different pharmacological treatments targeting myosin activity, actin polymerization, and mechanosensitive pathways, as well as the impact of the microenvironment stiffness on the wavelengths, frequencies, and speeds of the chemo-mechanical waves. Overall, our integrated theoretical and experimental approach reveals how collective wave dynamics arise due to the coupling between chemo-mechanical signaling and actin diffusion, shedding light on the role of podosomes in immune cell mechanosensing within the context of wound healing and cancer immunotherapy.

scholarly journals Divergent Design of Mechanical Metamaterials Clan Deducted from Arc-serpentine Curve

2021 ◽  
Author(s):  
Shengli Mi ◽  
Hongyi Yao ◽  
Xiaoyu Zhao ◽  
Wei Sun
Keyword(s):  
Thick Plate ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Design Strategies ◽  
Shape Morphing ◽  
Mechanical Metamaterials ◽  
Unit Cells ◽  
Combinatorial Principles ◽  
Composite Curve ◽  
Typical Design

Abstract The exotic properties of mechanical metamaterials are determined by their unit-cells' structure and spatial arrangement, in analogy with the atoms of conventional materials. Companioned with the mechanism of structural or cellular materials1–5, the ancient wisdom of origami6–11 and kirigami12–16 and the involvement of multiphysics interaction2,17,18 enrich the programable mechanical behaviors of metamaterials, including shape-morphing8,12,14,16,19, compliance4,5,8,17,20, texture2,18,21, and topology11,18,22−25. However, typical design strategies are mainly convergent, which transfers various structures into one family of metamaterials that are relatively incompatible with the others and do not fully bring combinatorial principles3,10,26 into play. Here, we report a divergent strategy that designs a clan of mechanical metamaterials with diverse properties derived from a symmetric curve consisting of serpentines and arcs. We derived this composite curve into planar and cubic unit-cells and modularized them by attaching magnetics. Moreover, stacking each of them yields two- and three-dimensional auxetic metamaterials, respectively. Assembling with both modules, we achieved three thick plate-like metamaterials separately with flexibility, in-plane buckling, and foldability. Furthermore, we demonstrated that the hybrid of paradox properties is possible by combining two of the above assembles. We anticipate that this divergent strategy paves the path of building a hierarchical library of diverse combinable mechanical metamaterials and making conventional convergent strategies more efficient to various requests. Main

Slavery, Redemption, and Manumission as Structural Metaphors in Augustine’s Theology

2021 ◽  
Vol 40 (2) ◽  
pp. 195-220
Author(s):  
Joshua Benjamins
Keyword(s):  
Roman Empire ◽  
Human Beings ◽  
Legal Norms ◽  
The Social ◽  
Christian Service ◽  
Contemporary Reality ◽  
A Chain ◽  
Relationship Of ◽  
Key Terms ◽  
The Devil

Across his corpus, Augustine strikingly and recurrently deploys the three cognate metaphors of slavery to sin, redemption from sin, and slavery to God. I argue that Augustine’s use of these theological metaphors is thoroughly contoured by the legal and social strictures governing slavery and freedom in the later Roman empire. To develop this argument, I pay close attention to the economic and legal connotations of some key terms in Augustine’s lexicon of salvation—like manumissio, redemptio, and libertas—and seek to tease out the social, legal, and economic logic they encapsulate. As I show, the concept of dominium underwrites Augustine’s description of the prelapsarian ordo naturalis as a chain of hierarchical relationships: between God and man, soul and body, male and female. The notion that human beings are enslaved to sin, subject to the condicio servitutis from birth, evokes the situation of laboring tenants (coloni) bound to the land through their origo. Moreover, the bishop of Hippo’s descriptions of captivity to the devil and liberation through the interpellation (interpellatio) of God the Redeemer are informed by the contemporary reality of barbarian captivity and liberales causae, so richly described in Augustine’s Letter 10*. Finally, Augustine’s characterization of Christian service in terms of a state of simultaneous freedom and servitude implicitly draws upon the legal norms governing the relationship of freed captives to their redeemers, as well as the obligations of obsequium and gratia which freedmen owed to their former masters.

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