Effective Dynamic Properties and Multi-Resonant Design of Acoustic Metamaterials

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
R. Zhu ◽  
G. L. Huang ◽  
G. K. Hu
Keyword(s):  
Dynamic Properties ◽  
Wave Dispersion ◽  
Wave Band ◽  
Energy Transfer Mechanism ◽  
Acoustic Metamaterials ◽  
Multiple Wave ◽  
Reflection And Transmission ◽  
Acoustic Metamaterial ◽  
Effective Dynamic ◽  
The Difference

In the study, a retrieval approach is extended to determine the effective dynamic properties of a finite multilayered acoustic metamaterial based on the theoretical reflection and transmission analysis. The accuracy of the method is verified through a comparison of wave dispersion curve predictions from the homogeneous effective medium and the exact solution. A multiresonant design is then suggested for the desirable multiple wave band gaps by using a finite acoustic metamaterial slab. Finally, the band gap behavior and kinetic energy transfer mechanism in a multilayered composite with a periodic microstructure are studied to demonstrate the difference between the Bragg scattering mechanism and the locally resonant mechanism.

scholarly journals A low/high frequency combined approach for the identification of mechanical properties of composite structural elements

2012 ◽  
Vol 39 (1) ◽  
pp. 1-25 ◽  
Author(s):  
Ivan Bartoli ◽  
Alessandro Marzaniy
Keyword(s):  
Mechanical Properties ◽  
High Frequency ◽  
Dynamic Properties ◽  
Wave Dispersion ◽  
Guided Wave ◽  
Analytical Models ◽  
Hybrid Technique ◽  
Dynamic Features ◽  
Dynamic Identification ◽  
The Difference

A combined low/high frequency dynamic identification approach is presented. The proposed hybrid technique compares experimentally extracted dynamic properties of plates such as modal frequencies and guided wave dispersion properties with the correspondent numerically predicted ones. Identification of mechanical properties of the plates is achieved by iteratively adjusting the mechanical properties assumed in finite element and semi-analytical models through minimization of the difference between experimental and predicted dynamic features.

scholarly journals Mode Shape-Based Damage Detection Method (MSDI): Experimental Validation

2021 ◽  
Vol 11 (10) ◽  
pp. 4589
Author(s):  
Ivan Duvnjak ◽  
Domagoj Damjanović ◽  
Marko Bartolac ◽  
Ana Skender
Keyword(s):  
Boundary Conditions ◽  
Damage Detection ◽  
Mode Shape ◽  
Experimental Validation ◽  
Detection Method ◽  
Dynamic Properties ◽  
Damage Index ◽  
Main Principle ◽  
The Difference ◽  
Different Levels

The main principle of vibration-based damage detection in structures is to interpret the changes in dynamic properties of the structure as indicators of damage. In this study, the mode shape damage index (MSDI) method was used to identify discrete damages in plate-like structures. This damage index is based on the difference between modified modal displacements in the undamaged and damaged state of the structure. In order to assess the advantages and limitations of the proposed algorithm, we performed experimental modal analysis on a reinforced concrete (RC) plate under 10 different damage cases. The MSDI values were calculated through considering single and/or multiple damage locations, different levels of damage, and boundary conditions. The experimental results confirmed that the MSDI method can be used to detect the existence of damage, identify single and/or multiple damage locations, and estimate damage severity in the case of single discrete damage.

scholarly journals Hybrid Bandgaps in Mass-coupled Bragg Atomic Chains: Generation and Switching

2021 ◽  
Vol 8 ◽  
Author(s):  
Shao-Feng Xu ◽  
Zhu-Long Xu ◽  
Kuo-Chih Chuang
Keyword(s):  
Structural Parameters ◽  
Dynamic Stiffness ◽  
Detailed Examination ◽  
Acoustic Metamaterials ◽  
Acoustic Metamaterial ◽  
Chain System ◽  
Different Types ◽  
Atomic Chains ◽  
Amplification System ◽  
Three Degree Of Freedom

In this work, without introducing mass-in-mass units or inertial amplification mechanisms, we show that two Bragg atomic chains can form an acoustic metamaterial that possesses different types of bandgaps other than Bragg ones, including local resonance and inertial amplification-like bandgaps. Specifically, by coupling masses of one monatomic chain to the same masses of a diatomic or triatomic chain, hybrid bandgaps can be generated and further be switched through the adjustment of the structural parameters. To provide a tuning guidance for the hybrid bandgaps, we derived an analytical transition parameter (p-value) for the mass-coupled monatomic/diatomic chain and analytical discriminants for the mass-coupled monatomic/triatomic chain. In our proposed mass-coupled monatomic/triatomic chain system, each set of analytical discriminants determines a hybrid bandgap state and a detailed examination reveals 14 different bandgap states. In addition to bandgap switching, the analytical p-value and discriminants can also be used as a guide for designing the coupled-chain acoustic metamaterials. The relations between the mass-coupled monatomic/triatomic chain system and a three-degree-of-freedom (DOF) inertial amplification system further indicate that the band structure of the former is equivalent to that of the latter through coupling masses by negative dynamic stiffness springs.

scholarly journals Simulation method for determining traction power of ATN–PRT vehicle

Transport ◽  
2016 ◽  
Vol 33 (2) ◽  
pp. 335-343 ◽  
Author(s):  
Maciej Kozłowski
Keyword(s):  
Aerodynamic Force ◽  
Dynamic Properties ◽  
Simulation Method ◽  
Drive System ◽  
Constant Speed ◽  
Technical Parameters ◽  
Personal Rapid Transit ◽  
Motion Resistance ◽  
The Difference ◽  
Traction Power

The construction of Personal Rapid Transit (PRT) vehicle made within the framework of Eco-Mobility project has been described in the present paper. Key features of the vehicles were identified – e.g. drive with three-phase linear motor with winding on the vehicle and fixed rotor in the road surface, contactless dynamic vehicle powering. Attention was paid to the difference in dynamic properties compared to rail vehicles, related to the lack of the so-called ‘centering mechanism’. A development of a nominal model for the analysis of vehicle drive properties was presented. Results of simulation studies were presented for a vehicle with running-drive system construction, planned for implementation in the city of Rzeszów (Poland). While discussing the problems of building a PRT system, there was a focus on the issue of determining power and traction of the vehicle. A methodology for determining the power and traction energy consumption of the vehicle was presented for assumed conditions of travel on road segments. Input values for the calculation of power are variables describing the curvature (or bends radii) of paths of movement between stops and the course of the current speed. Output values are total traction power or traction energy (where ‘traction’ refers to the power or mechanical work of drive forces). Three basic elements of traction power were isolated: the power of kinetic energy (for acceleration/delay of vehicle movement) basic (to offset the aerodynamic force of motion resistance at constant speed) and additional losses (to offset additional motion resistance forces operating in turns at constant speed). Due to the lack of vehicle prototypes with assumed structure, it was proposed that these components are determined via simulation. The presented results relate to the calculation of demand for power and energy for the planned test section. The scope of further work was indicated: determining the required traction characteristics of electric drive, selecting the best values for supercapacitor’s capacity in the drive system, determining the technical parameters of substation.

Adjustable sound insulation frequency band through the combination of membrane-type acoustic metamaterial array

2021 ◽  
Vol 263 (1) ◽  
pp. 5869-5877
Author(s):  
Xiang Wu ◽  
TengLong Jiang ◽  
JianWang Shao ◽  
GuoMing Deng ◽  
Chang Jin
Keyword(s):  
Thin Films ◽  
Frequency Band ◽  
Transmission Loss ◽  
Structural Parameters ◽  
Sound Insulation ◽  
Acoustic Metamaterials ◽  
Additional Mass ◽  
Acoustic Metamaterial ◽  
Material Parameters ◽  
Membrane Type

Membrane-type acoustic metamaterials are thin films or plates composed of periodic units with small additional mass. A large number of studies have shown that these metamaterials exhibit tunable anti-resonance, and their transmission loss values are much higher than the corresponding quality laws. At present, most researches on membrane-type acoustic metamaterials focus on the unit cell, and the sound insulation frequency band can only be adjusted by adjusting the structural parameters and material parameters. In this paper, two kinds of acoustic metamaterials with different structures are designed, which are the center placement of the mass and the eccentric placement of the mass.The two structures have different sound insulation characteristics. By designing different array combinations of acoustic metamaterials, the sound insulation peaks of different frequency bands are obtained. This paper studies the corresponding combination law, and effectively realizes the adjustable sound insulation frequency band.

scholarly journals Dynamic Analysis and Security Characteristics of Carrier-Based Aircraft Arresting in Yaw Condition

2020 ◽  
Vol 10 (4) ◽  
pp. 1253
Author(s):  
Yiming Peng ◽  
Pengpeng Xie ◽  
Xiaohui Wei ◽  
Hong Nie
Keyword(s):  
Negative Impact ◽  
Early Stage ◽  
Dynamic Properties ◽  
Wave Model ◽  
The United States ◽  
Us Military ◽  
Load Fluctuation ◽  
Kink Wave ◽  
The Difference ◽  
Yaw Angle

In order to research the safety characteristics of carrier-based aircraft in yaw arrest, a complete dynamic model of the arresting system of a certain type of aircraft was developed to understand more about its dynamic properties. Based on the discrete kink-wave model, a simulation of centering arrest was conducted. The simulation results were compared with experimental data from the United States (US) military standards, demonstrating that the basic changing laws are almost the same. On the basis of centering arrest, a simulation of yaw arrest was carried out. The results show that in yaw state, the difference in the lengths of the arresting cables on either side of the hook is smaller in the early stage after the hook hangs on the rope, which leads to little influence on load fluctuation produced by the kink-wave. With the increase in arresting distance, the difference in the lengths of the arresting cables on either side becomes larger, resulting in a situation in which the cable tension on the departure side will gradually become greater than that on the opposite side. In this situation, yaw landing has a negative impact on the characteristics of arresting safety, and the excessive yaw angle causes the aircraft to rush out of the safe landing area.

scholarly journals Hybrid acoustic metamaterial as super absorber for broadband low-frequency sound

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Yufan Tang ◽  
Shuwei Ren ◽  
Han Meng ◽  
Fengxian Xin ◽  
Lixi Huang ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Functional Materials ◽  
Theoretical Method ◽  
Acoustic Metamaterials ◽  
Mechanical Stiffness ◽  
Acoustic Metamaterial ◽  
Frequency Sound

Abstract A hybrid acoustic metamaterial is proposed as a new class of sound absorber, which exhibits superior broadband low-frequency sound absorption as well as excellent mechanical stiffness/strength. Based on the honeycomb-corrugation hybrid core (H-C hybrid core), we introduce perforations on both top facesheet and corrugation, forming perforated honeycomb-corrugation hybrid (PHCH) to gain super broadband low-frequency sound absorption. Applying the theory of micro-perforated panel (MPP), we establish a theoretical method to calculate the sound absorption coefficient of this new kind of metamaterial. Perfect sound absorption is found at just a few hundreds hertz with two-octave 0.5 absorption bandwidth. To verify this model, a finite element model is developed to calculate the absorption coefficient and analyze the viscous-thermal energy dissipation. It is found that viscous energy dissipation at perforation regions dominates the total energy consumed. This new kind of acoustic metamaterials show promising engineering applications, which can serve as multiple functional materials with extraordinary low-frequency sound absorption, excellent stiffness/strength and impact energy absorption.

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