scholarly journals Design of Soft Origami Mechanisms with Targeted Symmetries

Actuators ◽  
2018 ◽  
Vol 8 (1) ◽  
pp. 3 ◽  
Author(s):  
Andrew Gillman ◽  
Gregory Wilson ◽  
Kazuko Fuchi ◽  
Darren Hartl ◽  
Alexander Pankonien ◽  
...  
Keyword(s):  
Shape Change ◽  
Mechanical Energy ◽  
Rotational Symmetry ◽  
Deformation Mode ◽  
Energy Requirements ◽  
Optimization Framework ◽  
Geometric Difference ◽  
Novel Method ◽  
Low Stiffness ◽  
Local Vertex

The integration of soft actuating materials within origami-based mechanisms is a novel method to amplify the actuated motion and tune the compliance of systems for low stiffness applications. Origami structures provide natural flexibility given the extreme geometric difference between thickness and length, and the energetically preferred bending deformation mode can naturally be used as a form of actuation. However, origami fold patterns that are designed for specific actuation motions and mechanical loading scenarios are needed to expand the library of fold-based actuation strategies. In this study, a recently developed optimization framework for maximizing the performance of compliant origami mechanisms is utilized to discover optimal actuating fold patterns. Variant patterns are discovered through exploring different symmetries in the input and output conditions of the optimization problem. Patterns designed for twist (rotational symmetry) yield significantly better performance, in terms of both geometric advantage and energy requirements, than patterns exhibiting vertical reflection symmetries. The mechanical energy requirements for each design are analyzed and compared for both the small and large applied displacement regimes. Utilizing the patterns discovered through optimization, the multistability of the actuating arms is demonstrated empirically with a paper prototype, where the stable configurations are accessed through local vertex pop-through instabilities. Lastly, the coupled mechanics of fold networks in these actuators yield useful macroscopic motions and can achieve stable shape change through accessing the local vertex instabilities. This survey of origami mechanisms, energy comparison, and multistability characterization provides a new set of designs for future integration with soft actuating materials.

An Adjoint Based Approach for Optimal Design of Morphing SMP

2013 ◽  
Author(s):  
Shuang Wang ◽  
John C. Brigham
Keyword(s):  
Shape Change ◽  
Mechanical Energy ◽  
Optimization Methods ◽  
Design Parameters ◽  
Optimization Strategy ◽  
Thermally Activated ◽  
Gradient Based ◽  
Nonlinear Optimization Methods ◽  
Numerical Representations ◽  
Objective Functional

This work presents a strategy to identify the optimal localized activation and actuation for a morphing thermally activated SMP structure or structural component to obtain a targeted shape change or set of shape features, subject to design objectives such as minimal total required energy and time. This strategy combines numerical representations of the SMP structure’s thermo-mechanical behavior subject to activation and actuation with gradient-based nonlinear optimization methods to solve the morphing inverse problem that includes minimizing cost functions which address thermal and mechanical energy, morphing time, and damage. In particular, the optimization strategy utilizes the adjoint method to efficiently compute the gradient of the objective functional(s) with respect to the design parameters for this coupled thermo-mechanical problem.

An Efficient Computational Inverse Approach for Optimal Design of Localized Activation and Actuation for Morphing SMP Structures

2012 ◽  
Author(s):  
Shuang Wang ◽  
John C. Brigham
Keyword(s):  
Inverse Problem ◽  
Optimal Design ◽  
Shape Change ◽  
Mechanical Energy ◽  
Optimization Methods ◽  
Future Directions ◽  
Inverse Approach ◽  
Thermally Activated ◽  
Nonlinear Optimization Methods ◽  
Numerical Representations

A strategy is presented to identify the optimal localized activation and actuation for a morphing thermally-activated SMP structure or structural component to obtain a targeted shape change subject to design objectives such as minimal total required energy and time. This strategy combines numerical representations of the SMP structure’s thermo-mechanical behavior subject to activation and actuation with nonlinear optimization methods to efficiently solve the morphing inverse problem that includes minimizing cost functions which address thermal and mechanical energy, morphing time, and damage. The details of this strategy are presented along with simulated examples to display the capabilities and limitations, as well as potential future directions for improving these techniques.

The determination of the equivalent strain in finite, homogeneous deformation processes

1983 ◽  
Vol 18 (2) ◽  
pp. 119-123 ◽  
Author(s):  
R Sowerby ◽  
P C Chakravarti
Keyword(s):  
Shape Change ◽  
Plane Deformation ◽  
Deformation Mode ◽  
Equivalent Strain ◽  
Homogeneous Deformation ◽  
Line Pair ◽  
Principal Axes ◽  
Loading System ◽  
Deformation Processes

This article considers the in-plane deformation of a thin, incompressible membrane undergoing an arbitrary, but finite, homogeneous deformation mode. No discontinuities in the loading system are permitted, and the nature of the straining process is assumed unchanged from beginning to end. For these restricted deformation modes a technique is described whereby the equivalent strain can be evaluated by measuring the initial and final shape only of a finitely deformed grid marked on the surface of the membrane. The analysis is performed with reference to an initially square or rectangular grid of lines, since the nodes of the grid facilitate the experimental measurements. A distinction is drawn between homogeneous deformation and the special case of pure homogeneous deformation which results in the same shape change. In the latter mode a pair of principal axes can be identified which remain orthogonal during the entire deformation history; while for the former mode there is no such line pair which preserves orthogonality throughout the deformation. The article concludes with a brief discussion on the determination of strain in industrial stampings.

scholarly journals Embedding Effect on the Mechanical Stability of Pressurised Carbon Nanotubes

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Motohiro Sato ◽  
Hisao Taira ◽  
Tetsuro Ikeda ◽  
Hiroyuki Shima
Keyword(s):  
Carbon Nanotubes ◽  
Critical Pressure ◽  
Mechanical Stability ◽  
Mechanical Energy ◽  
Finite Thickness ◽  
Deformation Mode ◽  
Radial Pressure ◽  
Cross Sectional ◽  
Embedding Effect ◽  
The Continuum

We elaborate on the cross-sectional deformation of carbon nanotubes embedded into a self-contracting host medium. The continuum elastic approach is used to formulate the mechanical energy of both the embedded nanotubes and the self-contracting outer medium with finite thickness. Our formula allows us to evaluate the critical radial pressure applied on the interface between the embedded nanotube and the outer contracting medium as well as the deformation mode that arises immediately above the critical pressure. An interesting mechanical implication of the embedding effect, that is, the power-law dependence of the critical pressure on the elastic modulus of the medium, is deduced by the theoretical approach established.

Material influence in newly proposed ferroelectric energy harvesters

2018 ◽  
Vol 29 (16) ◽  
pp. 3305-3316 ◽  
Author(s):  
Dan Wang ◽  
Roderick Melnik ◽  
Linxiang Wang
Keyword(s):  
Energy Harvesting ◽  
Mechanical Energy ◽  
Phase Field Model ◽  
Ferroelectric Materials ◽  
Equivalent Material ◽  
Energy Harvesters ◽  
Piezoelectric Energy ◽  
New Strategy ◽  
Novel Method ◽  
Harvesting Process

Recently, a novel method for mechanical energy harvesting has been proposed, which is based on stress-induced polarization switching in ferroelectric materials. Compared with the traditional piezoelectric energy harvesters, a huge improvement in the output energy has already been theoretically demonstrated. In this article, the influence of different materials on the energy-harvesting performance associated with this new strategy is further studied. The state-of-the-art phase-field model is adopted to investigate the nonlinear hysteretic energy-harvesting process in two nanoscale ferroelectric energy harvesters, which are respectively based on two typical ferroelectric materials—single-crystal BaTiO3 and PbTiO3. In both cases, the effects of the bias voltage and bias resistance are carefully investigated and the optimum values are obtained. Later, the energy-harvesting process and energy flow details in both harvesters working at the optimum conditions are presented and carefully compared in the context of real applications. Furthermore, the energy-harvesting performance of a BaTiO3-based nanoscale piezoelectric energy harvester with equivalent material size is additionally simulated with the finite element method and compared with the corresponding results of the ferroelectric energy harvesters, where obvious advantages associated with the new strategy are demonstrated.

scholarly journals A Novel Method for Electricity Generation from Footsteps Using Piezoelectric Transducers

2021 ◽  
Vol 12 (2) ◽  
pp. 810-817
Author(s):  
D. Sathisha, Et. al.
Keyword(s):  
Mechanical Energy ◽  
Electrical Energy ◽  
Piezoelectric Transducers ◽  
Energy Scavenging ◽  
Maximum Output ◽  
Hydro Power ◽  
Exothermic Reactions ◽  
Novel Method ◽  
Density Population ◽  
Multiple Units

The process of generation of mechanical energy of human footsteps and converting into electrical energy using piezoelectric transducer is discussed in this paper. This method of generation comes under the Energy scavenging section of renewable resources where wasted energy during regular processes such as heat during exothermic reactions is captured and converted. With the increase in energy consumption from handy electronic devices, the concept of harvesting alternative non-conventional energy in highly density population regions is a new interest of late. The model is a focused spring action between two tiles on to the piezoelectric transducers. This model contracts during a footstep and therefore allowing the mechanical input onto the transducers and converting this input into electrical output. This process is focused on footsteps upon multiple units across a pathway to generate maximum output with minimal monitoring. This type of generator is simply a secondary backup to coal or hydro power generation. The main feature of such generator is that this requires no conscious thought on the user’s part.

scholarly journals Oligomodal metamaterials with multifunctional mechanics

2021 ◽  
Vol 118 (21) ◽  
pp. e2018610118
Author(s):  
Aleksi Bossart ◽  
David M. J. Dykstra ◽  
Jop van der Laan ◽  
Corentin Coulais
Keyword(s):  
Poisson’S Ratio ◽  
Shape Change ◽  
Density Ratio ◽  
Deformation Mode ◽  
System Size ◽  
Combinatorial Design ◽  
Poisson's Ratio ◽  
Zero Energy ◽  
Wide Range ◽  
Deformation Modes

Mechanical metamaterials are artificial composites that exhibit a wide range of advanced functionalities such as negative Poisson’s ratio, shape shifting, topological protection, multistability, extreme strength-to-density ratio, and enhanced energy dissipation. In particular, flexible metamaterials often harness zero-energy deformation modes. To date, such flexible metamaterials have a single property, for example, a single shape change, or are pluripotent, that is, they can have many different responses, but typically require complex actuation protocols. Here, we introduce a class of oligomodal metamaterials that encode a few distinct properties that can be selectively controlled under uniaxial compression. To demonstrate this concept, we introduce a combinatorial design space containing various families of metamaterials. These families include monomodal (i.e., with a single zero-energy deformation mode); oligomodal (i.e., with a constant number of zero-energy deformation modes); and plurimodal (i.e., with many zero-energy deformation modes), whose number increases with system size. We then confirm the multifunctional nature of oligomodal metamaterials using both boundary textures and viscoelasticity. In particular, we realize a metamaterial that has a negative (positive) Poisson’s ratio for low (high) compression rate over a finite range of strains. The ability of our oligomodal metamaterials to host multiple mechanical responses within a single structure paves the way toward multifunctional materials and devices.

scholarly journals Biodiesel production from catfish (Pangasius) fat via ultrasound- assisted method

2019 ◽  
Vol 1 (1) ◽  
pp. 15-20
Author(s):  
Intan Shafinaz Abd Manaf ◽  
Mohd Hasbi Ab. Rahim ◽  
Gaanty Pragas Maniam
Keyword(s):  
Reaction Time ◽  
Mechanical Energy ◽  
Biodiesel Production ◽  
Molar Ratio ◽  
Reaction Conditions ◽  
Surface Areas ◽  
Novel Method ◽  
Working Frequency ◽  
Ultrasound Assisted ◽  
Improve Mass Transfer

This paper reports studies in ultrasound-assisted heterogeneous solid catalyzed (CaO) synthesis of biodiesel from catfish (Pangasius) fat. Ultrasonication provides a faster chemical reaction, and the rate enhancements, refereed by cavitation that causes the building- up of pressures and temperatures, as well as increased catalytic surface areas and improve mass transfer. This novel method offers significant advantages such as shorter reaction time and less energy consumption than the conventional method, efficient molar ratio of methanol to triglycerides and provides the mechanical energy for mixing. The required activation energy for initiating the transesterification reaction and so, it gives a higher yield by transesterification of oils into biodiesel. The optimized reaction conditions were as follows: methanol to oil molar ratio of 15:1; catalyst (B-CaO), 9 wt. %; reaction temperature, 65 ± 2 °C; reaction time, 1 h at a working frequency of 42 kHz and the power supply of 100W. Highest conversion of 96.4 wt. % was achieved.

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