scholarly journals Experimental and Numerical Assessment of Local Resonance Phenomena in 3D-Printed Acoustic Metamaterials

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
D. Roca ◽  
T. Pàmies ◽  
J. Cante ◽  
O. Lloberas-Valls ◽  
J. Oliver
Keyword(s):  
Acoustic Waves ◽  
Unit Cell ◽  
Material Structure ◽  
Cell Design ◽  
Acoustic Metamaterials ◽  
Local Resonance ◽  
Resonance Phenomena ◽  
Resonance Frequencies ◽  
Characteristic Wavelength ◽  
3D Printed

Abstract The so-called locally resonant acoustic metamaterials (LRAMs) are a new kind of artificially engineered materials capable of attenuating acoustic waves. As the name suggests, this phenomenon occurs in the vicinity of internal frequencies of the material structure and can give rise to acoustic bandgaps. One possible way to achieve this is by considering periodic arrangements of a certain topology (unit cell), smaller in size than the characteristic wavelength. In this context, a computational model based on a homogenization framework has been developed from which one can obtain the aforementioned resonance frequencies for a given LRAM unit cell design in the sub-wavelength regime, which is suitable for low-frequency applications. Aiming at validating both the proposed numerical model and the local resonance phenomena responsible for the attenuation capabilities of such materials, a 3D-printed prototype consisting of a plate with a well selected LRAM unit cell design has been built and its acoustic response to normal incident waves in the range between 500 and 2000 Hz has been tested in an impedance tube. The results demonstrate the attenuating capabilities of the proposed design in the targeted frequency range for normal incident sound pressure waves and also establish the proposed formulation as the fundamental base for the computational design of 3D-printed LRAM-based structures.

Enhanced Sound Energy Harvesting by Leveraging Gradient-Index Phononic Crystals

2020 ◽  
Author(s):  
Ahmed Allam ◽  
Karim Sabra ◽  
Alper Erturk
Keyword(s):  
Finite Element ◽  
Numerical Simulations ◽  
Acoustic Waves ◽  
Design Procedure ◽  
Unit Cell ◽  
Design Parameters ◽  
Lens Design ◽  
Gradient Index ◽  
Cell Design ◽  
Electrical Load

Abstract We explore the harvesting of acoustic waves by leveraging a 3D-printed gradient-index phononic crystal (GRIN-PC) lens design. The concept is demonstrated numerically and experimentally for audio frequency range acoustic waves in air. Unit cell design procedure to achieve the required refractive index profile and numerical simulations of the band structure are executed using a high-fidelity finite-element model, followed by 3D simulations of the acoustic wave field for validation of the lens performance. Performance enhancement by focusing acoustic waves is quantified along with the level of anisotropy in the resulting 3D lens design. Additionally, a fully coupled multiphysics framework is developed to cover acoustic-structure interaction, piezoelectric coupling, as well as electrical load impedance. Finite-element simulations include the GRIN-PC lens and the harvester components along with basic electrical load to quantify the electrical power. In the full numerical simulations, design parameters such as the unit cell design, aperture of the lens, directional effects and anisotropy are explored in detail. Specifically, efforts are summarized on the unit cell design to minimize the directional sensitivity, toward making the lens close to omnidirectional.

scholarly journals Beam Scanning Capabilities of a 3D-Printed Perforated Dielectric Transmitarray

Electronics ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 379 ◽  
Author(s):  
Andrea Massaccesi ◽  
Gianluca Dassano ◽  
Paola Pirinoli
Keyword(s):  
3D Printing ◽  
Unit Cell ◽  
Multibeam Antenna ◽  
Beam Scanning ◽  
Additional Advantage ◽  
Ka Band ◽  
Measured Radiation ◽  
3D Printed ◽  
Printing Techniques

In this paper, the design of a beam scanning, 3D-printed dielectric Transmitarray (TA) working in Ka-band is discussed. Thanks to the use of an innovative three-layer dielectric unit-cell that exploits tapered sections to enhance the bandwidth, a 50 × 50 elements transmitarray with improved scanning capabilities and wideband behavior has been designed and experimentally validated. The measured radiation performances over a scanning coverage of ±27 ∘ shown a variation of the gain lower than 2.9 dB and a 1-dB bandwidth in any case higher than 23%. The promising results suggest that the proposed TA technology is a valid alternative to realize a passive multibeam antenna, with the additional advantage that it can be easily manufactured using 3D-printing techniques.

scholarly journals Gradient index phononic crystals and metamaterials

Nanophotonics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 685-701 ◽  
Author(s):  
Yabin Jin ◽  
Bahram Djafari-Rouhani ◽  
Daniel Torrent
Keyword(s):  
Refractive Index ◽  
Wave Propagation ◽  
Acoustic Waves ◽  
Effective Properties ◽  
Periodic Structures ◽  
Phononic Crystals ◽  
Ray Theory ◽  
Acoustic Metamaterials ◽  
Propagation Of Waves ◽  
At Will

AbstractPhononic crystals and acoustic metamaterials are periodic structures whose effective properties can be tailored at will to achieve extreme control on wave propagation. Their refractive index is obtained from the homogenization of the infinite periodic system, but it is possible to locally change the properties of a finite crystal in such a way that it results in an effective gradient of the refractive index. In such case the propagation of waves can be accurately described by means of ray theory, and different refractive devices can be designed in the framework of wave propagation in inhomogeneous media. In this paper we review the different devices that have been studied for the control of both bulk and guided acoustic waves based on graded phononic crystals.

Structure, Process, and Material Influences for 3D Printed Lattices Designed With Mixed Unit Cells

2020 ◽  
Author(s):  
Gabriel Briguiet ◽  
Paul F. Egan
Keyword(s):  
Elastic Modulus ◽  
Mechanical Testing ◽  
Mechanical Response ◽  
Cell Types ◽  
Unit Cell ◽  
Ultraviolet Curing ◽  
Mechanical Responses ◽  
Lattice Design ◽  
Unit Cells ◽  
3D Printed

Abstract Emerging 3D printing technologies are enabling the design and fabrication of novel architected structures with advantageous mechanical responses. Designing complex structures, such as lattices, with a targeted response is challenging because build materials, fabrication process, and topological design have unique influences on the structure’s mechanical response. Changing any factor may have unanticipated consequences, even for simpler lattice structures. Here, we conduct mechanical compression experiments to investigate varied lattice design, fabrication, and material combinations using stereolithography printing with a biocompatible polymer. Mechanical testing demonstrates that a higher ultraviolet curing time increases elastic modulus. Material testing demonstrated that anisotropy does not strongly influence lattice mechanics. Designs were altered by comparing homogenous lattices of single unit cell types and heterogeneous lattices that combine two types of unit cells. Unit cells for heterogeneous structures include a Cube design for a high elastic modulus and Cross design for improved shear response. Mechanical testing of three heterogeneous layouts demonstrated how unit cell organization influences mechanical outcomes, therefore enabling the tuning of an elastic modulus that surpasses the law of averages designed for application-dependent mechanical needs. These findings provide a foundation for linking design, process, and material for engineering 3D printed structures with preferred properties, while also facilitating new directions in design automation and optimization.

Design for Additive Manufacturing: Effectiveness of Unit Cell Design Guidelines As Ideation Tools

2019 ◽  
Author(s):  
I’Shea Boyd ◽  
Mohammad Fazelpour
Keyword(s):  
Additive Manufacturing ◽  
Effective Properties ◽  
Cellular Materials ◽  
Design Guidelines ◽  
Unit Cell ◽  
Cell Design ◽  
Recent Approach ◽  
Wide Range ◽  
Unit Cells ◽  
High Flexibility

Abstract The periodic cellular materials are comprised of repeatable unit cells. Due to outstanding effective properties of the periodic cellular materials such as high flexibility or high stiffness at low relative density, they have a wide range of applications in lightweight structures, crushing energy absorption, compliant structures, among others. Advancement in additive manufacturing has led to opportunities for making complex unit cells. A recent approach introduced four unit cell design guidelines and verified them through numerical simulation and user studies. The unit cell design guidelines aim to guide designers to re-design the shape or topology of a unit cell for a desired structural behavior. While the guidelines were identified as ideation tools, the effectiveness of the guidelines as ideation tools has not been fully investigated. To evaluate the effectiveness of the guidelines as ideation tools, four objective metrics have been considered: novelty, variety, quality, and quantity. The results of this study reveal that the unit cell design guidelines can be considered as ideation tools. The guidelines are effective in aiding engineers in creating novel unit cells with improved shear flexibility while maintaining the effective shear modulus.

scholarly journals Fabrication and Characterization of 3D Printed Thin Plates for Acoustic Metamaterials Applications

2019 ◽  
Vol 19 (22) ◽  
pp. 10365-10372
Author(s):  
Cecilia Casarini ◽  
Vicent Romero-Garcia ◽  
Jean-Philippe Groby ◽  
Benjamin Tiller ◽  
James F. C. Windmill ◽  
...  
Keyword(s):  
Thin Plates ◽  
Acoustic Metamaterials ◽  
3D Printed ◽  
Fabrication And Characterization

scholarly journals Computational design, engineering and manufacturing of a material-efficient 3D printed lattice structure

2020 ◽  
Vol 18 (4) ◽  
pp. 404-423
Author(s):  
Roberto Naboni ◽  
Anja Kunic ◽  
Luca Breseghello
Keyword(s):  
Lattice Structure ◽  
Computational Design ◽  
Material Structure ◽  
Fused Deposition Modelling ◽  
Design Engineering ◽  
Design Development ◽  
Fused Deposition ◽  
Construction Methods ◽  
3D Printed ◽  
Scarcity Of Resources

Building with additive manufacturing is an increasingly relevant research topic in the field of Construction 4.0, where designers are seeking higher levels of automation, complexity and precision compared to conventional construction methods. As an answer to the increasing problem of scarcity of resources, the presented research exploits the potential of Fused Deposition Modelling in the production of a lightweight load-responsive cellular lattice structure at the architectural scale. The article offers an extensive insight into the computational processes involved in the design, engineering, analysis, optimization and fabrication of a material-efficient, fully 3D printed, lattice structure. Material, structure and manufacturing features are integrated within the design development in a comprehensive computational workflow. The article presents methods and results while discussing the project as a material-efficient approach to complex structures.

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