Optimization of Viscoelastic Metamaterials for Vibration Attenuation Properties

2020 ◽  
pp. 2050116
Author(s):  
Ratiba F. Ghachi ◽  
Wael I. Alnahhal ◽  
Osama Abdeljaber ◽  
Jamil Renno ◽  
A. B. M. Tahidul Haque ◽  
...  
Keyword(s):  
Multiobjective Optimization ◽  
Experimental Testing ◽  
Low Frequency ◽  
Optimization Procedure ◽  
Bragg Scattering ◽  
Frequency Range ◽  
Element Analysis ◽  
Scattering Effect ◽  
Vibration Attenuation ◽  
Electrodynamic Shaker

Metamaterials (MMs) are composites that are artificially engineered to have unconventional mechanical properties that stem from their microstructural geometry rather than from their chemical composition. Several studies have shown the effectiveness of viscoelastic MMs in vibration attenuation due to their inherent vibration dissipation properties and the Bragg scattering effect. This study presents a multiobjective optimization based on genetic algorithms (GA) that aims to find a viscoelastic MM crystal with the highest vibration attenuation in a chosen low-frequency range. A multiobjective optimization allows considering the attenuation due to the MM inertia versus the Bragg scattering effect resulting from the periodicity of the MM. The investigated parameters that influence wave transmission in a one-dimensional (1D) MM crystal included the lattice constant, the number of cells and the layers’ thickness. Experimental testing and finite element analysis were used to support the optimization procedure. An electrodynamic shaker was used to measure the vibration transmission of the three control specimens and the optimal specimen in the frequency range 1–1200[Formula: see text]Hz. The test results demonstrated that the optimized specimen provides better vibration attenuation than the control specimens by both having a band-gap starting at a lower frequency and having less transmission at its passband.

On the Accuracy of Dynamic and Acoustic Analysis of Lightweight Panel Structures: A Comparison of ABAQUS and ANSYS

2012 ◽  
Author(s):  
Poul Henning Kirkegaard ◽  
Lars Vabbersgaard Andersen ◽  
Kristoffer Ahrens Dickow
Keyword(s):  
Acoustic Analysis ◽  
Low Frequency ◽  
Coupled Model ◽  
Acoustic Medium ◽  
Building Structures ◽  
Sound Waves ◽  
Frequency Range ◽  
Element Analysis ◽  
Structural Part ◽  
Fully Coupled

During the last couple of years, there has been an increasing focus on the vibro-acoustic performance of built environments due to increasing requirements in building codes regarding impact and airborne sound transmission. Hence, development of efficient and accurate methods for prediction of sound in such buildings is important. In the low-frequency range, prediction of sound and vibration in building structures may be achieved by finite-element analysis (FEA). The aim of this paper is to compare the two commercial codes ABAQUS and ANSYS for FEA of an acoustic-structural coupling in a timber, lightweight panel structure. For this purpose, modal analyses are carried out employing a fully coupled model of sound waves within an acoustic medium and vibrations in the structural part. The study concerns the frequency range 50–250 Hz.

Bandgap analysis of cylindrical shells of generalized phononic crystals by transfer matrix method

2015 ◽  
Vol 29 (24) ◽  
pp. 1550176 ◽  
Author(s):  
Hai-Sheng Shu ◽  
Xing-Guo Wang ◽  
Ru Liu ◽  
Xiao-Gang Li ◽  
Xiao-Na Shi ◽  
...  
Keyword(s):  
Cylindrical Shell ◽  
Transfer Matrix ◽  
State Vector ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Bragg Scattering ◽  
Mechanical State ◽  
Material Parameters ◽  
Scattering Effect ◽  
Torsional Shear

Based on the concept of generalized phononic crystals (GPCs), a type of 1D cylindrical shell of generalized phononic crystals (CS-GPCs) where two kinds of homogeneous materials are arranged periodically along radial direction was proposed in this paper. On the basis of radial, torsional shear and axial shear vibrational equations of cylindrical shell, the total transfer matrix of mechanical state vector were set up respectively, and the bandgap phenomena of these three type waves were disclosed by using the method of transfer matrix eigenvalue of mechanical state vector instead of the previous localized factor analyses and Bloch theorem. The characteristics and forming mechanism of these bandgaps of CS-GPCs, together with the influences of several important structure and material parameters on them were investigated and discussed in detail. Our results showed that, similar to the plane wave bandgaps, 1D CS-GPCs can also possess radial, torsional shear and axial shear wave bandgaps within high frequency region that conforms to the Bragg scattering effect; moreover, the radial vibration of CS-GPCs can generate low frequency bandgap (the start frequency near 0 Hz), as a result of the double effects of wavefront expansion and Bragg scattering effect, wherein the wavefront effect can be the main factor and directly determine the existence of the low frequency bandgaps, while the Bragg scattering effect has obvious enhancement effect to the attenuation. Additionally, the geometrical and material parameters of units have significant influences on the wave bandgaps of CS-GPCs.

scholarly journals AC Equivalent Circuit Model of an Electrochemical Accelerometer for 3D Numerical Simulation in the Low-Frequency Range

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4686
Author(s):  
Qiuzhan Zhou ◽  
Yuzhu Chen ◽  
Jikang Hu ◽  
Boshi Lyu
Keyword(s):  
Numerical Simulation ◽  
Equivalent Circuit ◽  
Characteristic Curve ◽  
Equivalent Circuit Model ◽  
Low Frequency ◽  
Circuit Model ◽  
Frequency Range ◽  
Element Analysis ◽  
Amplitude Frequency Characteristic ◽  
Vibration Sensors

The electrochemical principles presented in this paper can be applied to the manufacture of vibration sensors for oil and gas exploration, as well as long-period vibration sensors for the observation of natural earthquakes. To facilitate the manufacture of high-volume electrochemical accelerometer (EAM), this paper presents an AC equivalent circuit model of an EAM in a low-frequency range. A 3D time-dependent numerical simulation based on finite element analysis was designed to combine a complex chemical reaction with electric circuit theory. A sensitive chip channel model was constructed by using partial differential equations and the problem caused by a designed mathematical model was solved by using multi-physics finite element analysis. When the electrochemical properties of an electrochemical vibration sensor and its design parameters as well as the parameters of the AC equivalent circuit model are considered, the abstract processing of the sensor on the equivalent circuit is better accomplished. The effectiveness of the proposed simulation model and the equivalent circuit model were verified by comparing the amplitude-frequency characteristic curve of the equivalent circuit with the amplitude-frequency characteristic curve of the single-channel simulation model of the sensitive chip. These model not only have great significance for the design guidance of an external conditioning circuit but also provide an effective method to decouple the output signal and noise of the sensor reaction cavity.

Modal Analysis of Bandgap Formation for Vibration Attenuation in Locally Resonant Finite Beams

2016 ◽  
Author(s):  
Christopher Sugino ◽  
Stephen Leadenham ◽  
Massimo Ruzzene ◽  
Alper Erturk
Keyword(s):  
Boundary Conditions ◽  
Modal Analysis ◽  
Low Frequency ◽  
Optimal Number ◽  
Frequency Range ◽  
Design Guideline ◽  
Arbitrary Boundary ◽  
Low Frequency Vibration ◽  
Vibration Attenuation ◽  
Unit Cells

Metamaterials made from locally resonating arrays can exhibit attenuation bandgaps at wavelengths much longer than the lattice size, enabling low-frequency vibration attenuation. For an effective use of such locally resonant metamaterial concepts, it is required to bridge the gap between the dispersion characteristics and modal behavior of the host structure with its resonators. To this end, we develop a novel argument for bandgap formation in finite-length beams, relying on modal analysis and the assumption of infinitely many resonators. This assumption is analogous to the wave assumption of an infinitely long beam composed of unit cells, but gives additional analytical insight into the bandgap, and yields a simple formula for the frequency range of the bandgap. We present a design guideline to place the bandgap for a finite beam with arbitrary boundary conditions in a desired frequency range that depends only on the total mass ratio and natural frequency of the resonators. For a beam with a finite number of resonators and specified boundary conditions, we suggest a method for choosing the optimal number of resonators. We validate the model with both finite-element simulations and a simple experiment, and draw conclusions.

Vibration isolation characteristics of finite periodic tetra-chiral lattice coating filled with internal resonators

2016 ◽  
Vol 230 (16) ◽  
pp. 2840-2850 ◽  
Author(s):  
Dawei Zhu ◽  
Xiuchang Huang ◽  
Hongxing Hua ◽  
Hui Zheng
Keyword(s):  
Band Gap ◽  
Vibration Isolation ◽  
Periodic Structures ◽  
Low Frequency ◽  
Band Gaps ◽  
Stiffened Plate ◽  
Frequency Range ◽  
Vibration Attenuation ◽  
Unit Cells ◽  
Internal Resonators

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.

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

2015 ◽  
Vol 29 (23) ◽  
pp. 1550134 ◽  
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.

scholarly journals Phononic metastructures with ultrawide low frequency three-dimensional bandgaps as broadband low frequency filter

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad ◽  
C. W. Lim
Keyword(s):  
Passive Control ◽  
Noise Control ◽  
Three Dimensional ◽  
Low Frequency ◽  
Resonant Mode ◽  
Frequency Range ◽  
Research Activities ◽  
Vibration Attenuation ◽  
Mass Spring ◽  
Broadband Frequency

AbstractVibration and noise control are among the classical engineering problems that still draw extensive research interest today. Multiple active and passive control techniques to resolve these problems have been reported, however, the challenges remain substantial. The recent surge of research activities on acoustic metamaterials for vibration and noise control are testimony to the fact that acoustic metamaterial is no longer limited to pure theoretical concepts. For vibration and noise control over an ultrawide frequency region, 3-D metastructures emerge as a novel solution tool to resolve this problem. In that context, the present study reports a novel proposal for 3-D monolithic phononic metastructures with the capability to induce low frequency ultrawide three-dimensional bandgaps with relative bandwidth enhancements of 157.6% and 160.1%. The proposed monolithic metastructure designs consist of elastic frame assembly that is connected with the rigid cylindrical masses. Such structural configuration mimics monoatomic mass-spring chain where an elastic spring is connected with a rigid mass. We develop an analytical model based on monoatomic mass-spring chain to determine the acoustic mode frequency responsible for opening the bandgap. The wave dispersion study reveals the presence of ultrawide bandgaps for both types of metastructures. The modal analysis shows distribution of vibration energy in the bandgap opening (global resonant mode) and closing (local resonant mode) bounding edges. We further analyze the band structures and discuss the physical concepts that govern such ultrawide bandgap. Vibration attenuation inside the bandgap frequency range is demonstrated by frequency response studies conducted by two different finite element models. Thanks to additive manufacturing technology, 3-D prototypes are prepared and low amplitude vibration test is performed to validate the numerical findings. Experimental results show the presence of an ultrawide vibration attenuation zone that spreads over a broadband frequency spectrum. The bandgaps reported by the proposed metastructures are scale and material independent. The research methodology, modelling and design strategy presented here may pave the way for the development of novel meta-devices to control vibration and noises over a broadband frequency range.

Acoustic Modal Test and Finite Element Analysis on Vehicle Cavity

2012 ◽  
Vol 239-240 ◽  
pp. 32-36 ◽  
Author(s):  
Wei Ling Hou ◽  
Hong Zhou ◽  
Si Le Wang
Keyword(s):  
Finite Element ◽  
Commercial Vehicle ◽  
Low Frequency ◽  
Element Model ◽  
Acoustic Properties ◽  
Frequency Range ◽  
Element Analysis ◽  
Modal Test ◽  
Analysis System ◽  
The Finite Element Model

A cavity acoustic modal of a medium-sized commercial vehicle was tested and analyzed based on LMS Test.Lab modal analysis system. Acoustic modal characteristics, including modal frequencies and modal shapes of the cavity, were obtained. By comparing the results of acoustic modal frequencies to the structure modal ones, the acoustic-structure coupling at critical frequencies could be avoided and the noise in low frequency range could be reduced. Meanwhile, the simulation of the acoustic modal is analyzed by establishing the finite element model of the cavity, which may be a reference to improve the interior acoustic properties of the cavity.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
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.

Dynamic Damping and Stiffness Characteristics of the Rolling Tire

2001 ◽  
Vol 29 (4) ◽  
pp. 258-268 ◽  
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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