An Analytical Model for the Interaction of Mass Inclusions in Heterogeneous (HG) Blankets

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
A. Wagner ◽  
M. E. Johnson ◽  
K. Idrisi ◽  
D. P. Bartylla
Keyword(s):  
Elastic Layer ◽  
Analytical Approach ◽  
Low Frequency ◽  
Control Device ◽  
Effective Stiffness ◽  
Special Focus ◽  
Dynamic Vibration Absorber ◽  
Low Frequencies ◽  
Dynamic Vibration ◽  
The Masses

The heterogeneous (HG) blanket is a passive treatment used to reduce the low frequency transmission of sound through partitions. HG blankets, glued onto a structure, consist of an elastic medium with embedded mass inhomogeneities that mechanically replicate a mass-spring-damper system to reduce efficient radiating structural modes at low frequencies. The elastic layer typically used has sound absorption properties to create a noise control device with a wide bandwidth of performance. The natural frequency of an embedded dynamic vibration absorber is determined by the mass of the inhomogeneity as well as by its effective stiffness due to the interaction of the mass inclusion with the elastic layer. A novel analytical approach has been developed to describe in detail the interaction of the mass inclusions with the elastic layer and the interaction between the masses by evaluating special elastomechanical concepts. The effective stiffness is predicted by the analytical approach based on the shape of the mass inclusions as well as on the thickness and material properties of the layer. The experimental validation is included and a simplified direct equation to calculate the effective stiffness of a HG blanket is proposed. Furthermore, the stress field inside the elastic material will be evaluated with focus on the stresses at the base to assess the modeling of one or more masses placed on top of the elastic layer as dynamic vibration absorbers. Finally, the interaction between two (or more) masses placed onto the same layer is studied with special focus on the coupling of the masses at low distances between them.

Dynamic analysis and vibration reduction of articulated silicone gel column with varying geometry

2021 ◽  
pp. 1-13
Author(s):  
Ji-Hou Yang ◽  
Xiao-Dong Yang ◽  
Qing-Kai Han ◽  
Jinguo Liu
Keyword(s):  
Frequency Band ◽  
Vibration Reduction ◽  
Low Frequency ◽  
Vibration Absorber ◽  
Frequency Range ◽  
Dynamic Vibration Absorber ◽  
Dynamic Vibration ◽  
Silicone Gel ◽  
Resonance Frequencies ◽  
Reduction Effect

Abstract To improve vibration reduction effect in low-frequency band of dynamic vibration absorber (DVA), a novel type of articulated silicone gel column (SGC) is introduced in the design of the tuned dynamic vibration absorber. The nonlinear variation of frequency of SGC with varying geometry is obtained by both finite element simulation and experiments. The most sensitive mode is located, which has wider frequency range by varying the geometry. The polynomial fitting is used to describe nonlinear relation between frequency and geometry. By tuning the geometry, the equivalent stiffness and then resonance frequencies can be manipulated to behave as an active vibration absorber. The vibration reduction experiment of SGC vibration absorbers is investigated. It is found that SGC has better vibration reduction effect in low-frequency band. The experimental results in the current design demonstrate that the vibration reduction effect can reach 94.03% when tuning SCG to the first order main resonance. The dimensions and material parameters of SGC should be altered for specific frequency range and vibration strength.

Design and Experimental Verification of Torsion-Bending Low-Frequency Piezoelectric Energy Harvesters

2016 ◽  
Author(s):  
Hichem Abdelmoula ◽  
Nathan Sharpes ◽  
Hyeon Lee ◽  
Abdessattar Abdelkefi ◽  
Shashank Priya
Keyword(s):  
System Analysis ◽  
Energy Harvester ◽  
Excitation Frequency ◽  
Low Frequency ◽  
Load Resistance ◽  
Mode Shapes ◽  
Low Frequencies ◽  
Piezoelectric Energy ◽  
The Masses ◽  
Tip Mass

We design and experimentally validate a zigzag piezoelectric energy harvester that can generate energy at low frequencies and which can be used to operate low-power consumption electronic devices. The harvester is composed of metal and piezoelectric layers and is used to harvest energy through direct excitations. A computational model is developed using Abaqus to determine the exact mode shapes and coupled frequencies of the considered energy harvester in order to design a broadband torsion-bending mechanical system. Analysis is then performed to determine the optimal load resistance. The computational results are compared and validated with the experimental measurements. More detailed analysis is then carried out to investigate the effects of the masses on the bending and torsion natural frequencies of the harvester and generated power levels. The results show that due to the coupling between the bending and torsion modes of the zigzag structure, highest levels of the harvested power are obtained when the excitation frequency matches the coupled frequency of torsion type for three different values of the tip mass.

A Design Method for Sound Absorbing Structure at Low Frequency

2020 ◽  
Vol 982 ◽  
pp. 39-50
Author(s):  
Ying Jie Fu ◽  
Xiao Ming Wang ◽  
Yu Lin Mei
Keyword(s):  
Design Method ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Channel Structure ◽  
Response Analysis ◽  
Acoustic Metamaterials ◽  
Element Analysis ◽  
Low Frequencies ◽  
Mass Unit ◽  
The Masses

Traditional acoustic absorbing materials are not effective for low-frequency engineering applications, but on the basis of the locally resonant principle, acoustic metamaterials can utilize the resonance of vibrators to dissipate acoustic energy and realize the subwavelength design of acoustic absorbers, therefore the acoustic metamaterials have great potential applications for noise reduction at low frequencies. This paper firstly employs the Bloch theory to investigate the effects of the parameters of the unit cell of the embedded membrane-and-mass metamaterials on the dispersion characteristics of the metamaterials, and the band gap is verified by the full wave finite element analysis. And then, a model of acoustic metamaterials is constructed by embeding an array of membrane-and-masses into a channel structure filled with acoustic materials. Next the transient frequency response analysis is performed to simulate the wave propagation in the model, the results show that the acoustic metamaterials can absorb the sound through the local resonance of the membrane-and-mass vibrators. Finally, an acoustic metamaterial maze structure is designed and analyzed, in the structure the membrane-and-mass array is embedded and the masses varies periodically. The research illustrates that the acoustic metamaterials with membrane-and-mass unit cells have excellent performances on the sound absorption at low frequency.

scholarly journals Study on the Vibration Suppression Method of Urban Railway Vehicles Based on a Composite Dynamic Vibration Absorber

2019 ◽  
Vol 296 ◽  
pp. 01010
Author(s):  
Qian Sun ◽  
Yongpeng Wen ◽  
Yu Zou
Keyword(s):  
Vibration Suppression ◽  
Vibration Reduction ◽  
Low Frequency ◽  
Peak Frequency ◽  
Degree Of Freedom ◽  
Vibration Absorber ◽  
Dynamic Vibration Absorber ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Dynamic Vibration

To reduce the bounce and the pitch vibration of carbody, a vertical dynamic model for urban rail vehicles is established to analyze the vibration response of the carbody in the low frequency range. In this paper, different methods of single-degree-of-freedom dynamic vibration absorber to suppress the vibration for carbody are investigated. The limits of single-degree-of-freedom dynamic vibration absorber to the vibration reduction effect of carbody are pointed out. After that, the design of a composite dynamic vibration absorber including a double oscillator structure is introduced. A vibration discreteness index is used to evaluate dynamic vibration absorbers with various designs for the vibration damping performance. Finally, the vibration reduction performance of the composite dynamic vibration absorber is verified by Sperling’s riding index. The results demonstrate that the performance of the single degree of freedom dynamic vibration absorber attached to a carbody may increase the vibration within a partial scope, when the peak frequency of vibration is far away from the design frequency. The installation of the composite dynamic vibration absorber vibration provides gentler running experience for passengers.

H 2 Optimization of the Three-Element Type Dynamic Vibration Absorbers

2002 ◽  
Vol 124 (4) ◽  
pp. 583-592 ◽  
Author(s):  
Toshihiko Asami ◽  
Osamu Nishihara
Keyword(s):  
Optimization Design ◽  
Random Excitation ◽  
Control Device ◽  
Algebraic Solution ◽  
Primary System ◽  
Dynamic Vibration Absorber ◽  
Dynamic Vibration ◽  
Optimum Parameters ◽  
Element Type ◽  
H2 Optimization

The dynamic vibration absorber (DVA) is a passive vibration control device which is attached to a vibrating body (called a primary system) subjected to exciting force or motion. In this paper, we will discuss an optimization problem of the three-element type DVA on the basis of the H2 optimization criterion. The objective of the H2 optimization is to reduce the total vibration energy of the system for overall frequencies; the total area under the power spectrum response curve is minimized in this criterion. If the system is subjected to random excitation instead of sinusoidal excitation, then the H2 optimization is probably more desirable than the popular H∞ optimization. In the past decade there has been increasing interest in the three-element type DVA. However, most previous studies on this type of DVA were based on the H∞ optimization design, and no one has been able to find the algebraic solution as of yet. We found a closed-form exact solution for a special case where the primary system has no damping. Furthermore, the general case solution including the damped primary system is presented in the form of a numerical solution. The optimum parameters obtained here are compared to those of the conventional Voigt type DVA. They are also compared to other optimum parameters based on the H∞ criterion.

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