Topological design of square lattice structure for broad and multiple band gaps in low-frequency range

Owing to their locally resonant mechanism, internal resonators are usually used to provide band gaps in low-frequency region for many types of periodic structures. In this study, internal resonators are used to improve the vibration attenuation ability of finite periodic tetra-chiral coating, enabling high reduction of the radiated sound power by a vibrating stiffened plate. Based on the Bloch theorem and finite element method, the band gap characteristics of tetra-chiral unit cells filled with and without internal resonators are analysed and compared to reveal the relationship between band gaps and vibration modes of such tetra-chiral unit cells. The rotational vibration of internal resonators can effectively strengthen the vibration attenuation ability of tetra-chiral lattice and extend the effective frequency range of vibration attenuation. Two tetra-chiral lattices with and without internal resonators are respectively designed and their vibration transmissibilities are measured using the hammering method. The experimental results confirm the vibration isolation effect of the internal resonators on the finite periodic tetra-chiral lattice. The tetra-chiral lattice as an acoustic coating is applied to a stiffened plate, and analysis results indicate that the internal resonators can obviously enhance the vibration attenuation ability of tetra-chiral lattice coating in the frequency range of the band gap corresponding to the rotating vibration mode of internal resonators. When the soft rubber with the internal resonators in tetra-chiral layers has gradient elastic modulus, the vibration attenuation ability and noise reduction of the tetra-chiral lattice coating are basically enhanced in the frequency range of the corresponding band gaps of tetra-chiral unit cells.

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Research on the band gaps of the two-dimensional Sierpinski fractal phononic crystals

Modern Physics Letters B ◽

10.1142/s0217984915501341 ◽

2015 ◽

Vol 29 (23) ◽

pp. 1550134 ◽

Cited By ~ 5

Author(s):

Nansha Gao ◽

Jiu Hui Wu ◽

Li Jing

Keyword(s):

Rotation Angle ◽

Low Frequency ◽

Phononic Crystals ◽

Band Gaps ◽

Transmission Spectra ◽

Two Dimensional ◽

Bragg Scattering ◽

Frequency Range ◽

Displacement Fields ◽

First Time

In this paper, we study the band gaps (BGs) of the two-dimensional (2D) Sierpinski fractal phononic crystals (SFPGs) embedded in the homogenous matrix. The BGs structure, transmission spectra and displacement fields of eigenmodes of the proposed structures are calculated by using finite element method (FEM). Due to the simultaneous mechanisms of the Bragg scattering, the structure can exhibit low-frequency BGs, which can be effectively shifted by changing the inclusion rotation angle. The initial stress values can compress the BGs is proposed for the first time. Through the calculation, it is shown that, in the 2D solid–solid SFPG, the multi-frequency BGs exist. The whole BGs would incline to the low-frequency range with the increase of the fractal dimension. The SFPGs with different shape inclusions, can modulate the number, width and location of BGs. The study in this paper is relevant to the design of tuning BGs and isolators in the low-frequency range.

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Research on the Band Gap Characteristics of Two-Dimensional Phononic Crystals Microcavity with Local Resonant Structure

Shock and Vibration ◽

10.1155/2015/239832 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8 ◽

Cited By ~ 2

Author(s):

Mao Liu ◽

Pei Li ◽

Yongteng Zhong ◽

Jiawei Xiang

Keyword(s):

Band Gap ◽

Phononic Crystal ◽

Engineering Application ◽

Low Frequency ◽

Phononic Crystals ◽

Band Gaps ◽

Wave Band ◽

Two Dimensional ◽

Frequency Range ◽

Gap Characteristics

A new two-dimensional locally resonant phononic crystal with microcavity structure is proposed. The acoustic wave band gap characteristics of this new structure are studied using finite element method. At the same time, the corresponding displacement eigenmodes of the band edges of the lowest band gap and the transmission spectrum are calculated. The results proved that phononic crystals with microcavity structure exhibited complete band gaps in low-frequency range. The eigenfrequency of the lower edge of the first gap is lower than no microcavity structure. However, for no microcavity structure type of quadrilateral phononic crystal plate, the second band gap disappeared and the frequency range of the first band gap is relatively narrow. The main reason for appearing low-frequency band gaps is that the proposed phononic crystal introduced the local resonant microcavity structure. This study provides a good support for engineering application such as low-frequency vibration attenuation and noise control.

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A novel metal-matrix phononic crystal with a low-frequency, broad and complete, locally-resonant band gap

Modern Physics Letters B ◽

10.1142/s0217984918502214 ◽

2018 ◽

Vol 32 (19) ◽

pp. 1850221 ◽

Cited By ~ 3

Author(s):

Suobin Li ◽

Yihua Dou ◽

Tianning Chen ◽

Zhiguo Wan ◽

Zhengrong Guan

Keyword(s):

Band Gap ◽

Metal Matrix ◽

Steel Plate ◽

Phononic Crystal ◽

Low Frequency ◽

Crystal Plate ◽

Band Gaps ◽

Frequency Range ◽

Low Frequency Vibration ◽

Out Of Plane

In this paper, a novel metal-matrix phononic crystal with a low-frequency, broad and complete, locally-resonant band gap, which includes the in-plane and out-of-plane band gaps, is investigated numerically. The proposed structure consists of double-sided single “hard” cylinder stubs, which are deposited on a two-dimensional locally-resonant phononic-crystal plate that consists of an array of rubber fillers embedded in a steel plate. Our results indicate that both the out-of-plane band gap and the in-plane band gap increase after introducing single “hard” cylinder stubs. More specifically, the out-of-plane band gap is increased by the out-of-plane analogous-rigid mode, while the in-plane band gap is increased by the in-plane analogous-rigid mode. The out-of-plane and the in-plane analogous-rigid mode are formed after introduction of the single “hard” cylinder stub. As a result, a broad, complete locally-resonant band gap in the low frequency is obtained due to the broad in-plane and out-of-plane band gaps overlapping. Compared to the classical double-sided stubbed metal-matrix phononic-crystal plate, the absolute bandwidth of the complete band gap is increased by a factor of 4.76 in the proposed structure. Furthermore, the effect of simple “hard” stubs on complete band gaps is investigated. The results show that the location of the complete band gaps can be modulated using a low frequency, and the bandwidth can be extended to a larger frequency range using different “hard” stubs. The new structure provides an effective way for metal-matrix phononic crystals to obtain broad and complete locally-resonant band gaps in the low-frequency range, which has many applications for low-frequency vibration reduction.

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Multi-large low-frequency band gaps in a periodic hybrid structure

Modern Physics Letters B ◽

10.1142/s0217984916501116 ◽

2016 ◽

Vol 30 (08) ◽

pp. 1650116 ◽

Cited By ~ 3

Author(s):

T. Wang ◽

M. P. Sheng ◽

H. B. Guo

Keyword(s):

Frequency Band ◽

Phononic Crystal ◽

Low Frequency ◽

Hybrid Structure ◽

Band Gaps ◽

Response Analysis ◽

Acoustic Metamaterials ◽

Frequency Range ◽

Local Resonance ◽

Small Series

A hybrid structure composed of a local resonance mass and an external oscillator is proposed in this paper for restraining the elastic longitudinal wave propagation. Theoretical model has been established to investigate the dispersion relation and band gaps of the structure. The results show that the hybrid structure can produce multi-band gaps wider than the multi-resonator acoustic metamaterials. It is much easier for the hybrid structure to yield wide and low band gaps by adjusting the mass and stiffness of the external oscillator. Small series spring constant ratio results in low-frequency band gaps, in which the external oscillator acts as a resonator and replaces the original local resonator to hold the band gaps in low frequency range. Compared with the one-dimensional phononic crystal (PC) lattice, a new band gap emerges in lower frequency range in the hybrid structure because of the added local resonance, which will be a significant assistance in low-frequency vibration and noise reduction. Further, harmonic response analysis using finite element method (FEM) has been performed, and results show that elastic longitudinal waves are efficiently forbidden within the band gaps.

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Band Gap Properties of Two-Dimensional Photonic Crystal Structures with Rectangular Lattice

Journal of Optical Communications ◽

10.1515/joc-2014-0049 ◽

2015 ◽

Vol 36 (2) ◽

Cited By ~ 10

Author(s):

Hamed Alipour-Banaei ◽

Somaye Serajmohammadi ◽

Farhad Mehdizadeh ◽

Alireza Andalib

Keyword(s):

Band Gap ◽

Lattice Structure ◽

Band Gaps ◽

The Other ◽

Square Lattice ◽

Rectangular Lattice ◽

Lattice Structures ◽

Two Dimensional ◽

Two Dimensional Photonic Crystal ◽

Polarization Independent

AbstractIn this paper we proposed a new structure of two-dimensional photonic crystals with rectangular lattice. After deducing the primitive lattice vectors and first Brillouin zone of the structures, we studied the band gap properties of horizontal and vertical rectangular lattice structures and compared them with conventional square lattice structure. The most excellent characteristic of these structures is their joint band gap regions, which make them suitable for designing polarization-independent devices. The other advantage of these structures is having band gaps at higher normalized frequencies.

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Experimental study on the high-damping properties of metallic lattice structures obtained from SLM

10.31224/osf.io/xnvej ◽

2020 ◽

Cited By ~ 1

Author(s):

Federico Scalzo ◽

Giovanni Totis ◽

Emanuele Vaglio ◽

Marco Sortino

Keyword(s):

Dynamic Behaviour ◽

Acoustic Noise ◽

Lattice Structure ◽

Low Frequency ◽

Weight Ratio ◽

Damping Capacity ◽

Lattice Structures ◽

Frequency Range ◽

Global Dynamic ◽

Manufacturing Technologies

Modern additive manufacturing technologies allow the creation of parts characterized by complex geometries that cannot be created using conventional production techniques. Among them the Selective Laser Melting (SLM) technique is very promising. By using SLM it is possible to create lightweight lattice structures that may fill void regions or partially replace bulk regions of a given mechanical component. As a consequence, the overall mechanical properties of the final component can be greatly enhanced, such as the resistance to weight ratio and its damping capacity against undesired vibrations or acoustic noise. Nevertheless, only a few research works focused on the characterization of the dynamic behaviour of lattice structures, that were mainly investigated in the low frequency range or directly tested on some specific applications. In this work the dynamic behaviour of lattice structures in the medium-high frequency range was experimentally investigated and then modelled. For this purpose, different types of lattice structures made of AlSi10Mg and AISI 316L were measured. Experimental modal analysis was performed on the obtained specimens in order to assess the influence of lattice material and unit cell geometry on their global dynamic behaviour. Experimental results revealed that lattice structures have superior damping characteristics compared to solid materials having an equivalent static stiffness. Eventually, the classic Rayleigh model was found to be adequate - with some approximation - to explain the damping behaviour of a generic lattice structure.

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Evaluation of Special Hearing Aids for Deaf Children

Journal of Speech and Hearing Disorders ◽

10.1044/jshd.3604.527 ◽

1971 ◽

Vol 36 (4) ◽

pp. 527-537 ◽

Cited By ~ 1

Author(s):

Norman P. Erber

Keyword(s):

Hearing Aids ◽

High Frequency ◽

Hearing Aid ◽

Low Frequency ◽

Acoustic Stimulation ◽

Deaf Children ◽

Frequency Range ◽

Frequency Limit ◽

Unpublished Studies ◽

Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

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Dynamic Damping and Stiffness Characteristics of the Rolling Tire

Tire Science and Technology ◽

10.2346/1.2135243 ◽

2001 ◽

Vol 29 (4) ◽

pp. 258-268 ◽

Cited By ~ 12

Author(s):

G. Jianmin ◽

R. Gall ◽

W. Zuomin

Keyword(s):

Dynamic Behavior ◽

Variable Parameter ◽

Low Frequency ◽

Vertical Load ◽

Frequency Range ◽

Inflation Pressure ◽

Vehicle Simulation ◽

Dynamic Damping ◽

Speed Range ◽

Stiffness Characteristics

Abstract A variable parameter model to study dynamic tire responses is presented. A modified device to measure terrain roughness is used to measure dynamic damping and stiffness characteristics of rolling tires. The device was used to examine the dynamic behavior of a tire in the speed range from 0 to 10 km/h. The inflation pressure during the tests was adjusted to 160, 240, and 320 kPa. The vertical load was 5.2 kN. The results indicate that the damping and stiffness decrease with velocity. Regression formulas for the non-linear experimental damping and stiffness are obtained. These results can be used as input parameters for vehicle simulation to evaluate the vehicle's driving and comfort performance in the medium-low frequency range (0–100 Hz). This way it can be important for tire design and the forecasting of the dynamic behavior of tires.

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