Shielding performance of T-shaped periodic barrier for surface waves in transversely isotropic soil

2021 ◽  
pp. 146442072110130
Author(s):  
De-Xin Ji ◽  
Gui-Lan Yu
Keyword(s):  
Finite Element Method ◽  
Surface Waves ◽  
Floquet Theory ◽  
Vibration Isolation ◽  
Mass Density ◽  
Density Ratio ◽  
Transversely Isotropic ◽  
Band Gaps ◽  
Modulus Ratio ◽  
Material Parameters

Aiming at the vibration isolation in transversely isotropic soil, a T-shaped partially embedded periodic barrier for surface waves is proposed, and its shielding performance is explored by using finite element method combined with Bloch-Floquet theory. Seven independent dimensionless material parameters are derived and their influences on band gaps are discussed numerically. The results show that the band gaps exhibit strong sensitivity to the three parameters out of seven, and the band gaps are far wider in transversely isotropic soils than that in the isotropic. The mass density ratio and the shear modulus ratio of the barrier to the soil, as well as the length ratio of the barrier above the ground to that below, can be used to adjust band gaps effectively to meet the shielding requirements for different frequency ranges under different anisotropic soils. As a case of study, the El Centro seismic wave is considered and found that it can be considerably attenuated by the designed periodic barrier.

Three-Dimensional Sonic Band Gaps Tunned by Material Parameters

2010 ◽  
Vol 29-32 ◽  
pp. 1797-1802 ◽  
Author(s):  
Xiao Zhou Zhou ◽  
Yue Sheng Wang ◽  
Chuan Zeng Zhang
Keyword(s):  
Bulk Modulus ◽  
Mass Density ◽  
Density Ratio ◽  
Three Dimensional ◽  
Expansion Method ◽  
Small Mass ◽  
Band Gaps ◽  
Face Centered Cubic ◽  
Modulus Ratio ◽  
Material Parameters

In this paper, band gaps tunned by material parameters in three-dimensional fluid-fluid sonic crystals are studied. From the basic wave equation, it is found that the material parameters directly determining the three-dimensional sonic band gaps are the mass density ratio and bulk modulus ratio. The calculation of the sonic band gaps is completed by the plane-wave expansion method. The effects of these parameters on sonic band gaps are discussed in details for the simple-cubic (sc), face-centered cubic (fcc) and body-centered cubic (bcc) lattices. The results show that the first potential sonic band gap easily appears at both small mass density ratio and bulk modulus ratio, and becomes wider with both of these two parameters decreasing. The bulk modulus ratio plays a more important role than the mass density ratio in tuning the sonic band gaps. The present analysis can be applied to artificially design band gaps.

Effects of Material Parameters on Longitudinal Vibration Band Gaps in Thin Phononic Crystal Plates

2014 ◽  
Vol 654 ◽  
pp. 16-19
Author(s):  
Hao Jiang Zhao ◽  
Rong Qiang Liu ◽  
Hong Wei Guo
Keyword(s):  
Longitudinal Vibration ◽  
Mass Density ◽  
Phononic Crystal ◽  
Density Ratio ◽  
Young Modulus ◽  
Expansion Method ◽  
Band Gaps ◽  
Square Lattice ◽  
Vibration Band ◽  
Material Parameters

The improved plane wave expansion method is used to investigate the effects of material parameters on the longitudinal vibration band gaps in thin phononic crystal plates. Both square lattice and graphite lattice are considered. Results show that the parameters playing the essential roles are the mass density ratio and the Young modulus ratio of the scatterers and the host materials.

scholarly journals Phononic Band Gaps of Elastic Periodic Structures: A Homogenization Theory Study

2007 ◽  
Author(s):  
Ying-Hong Liu ◽  
Chien C. Chang ◽  
Ruey-Lin Chern ◽  
C. Chung Chang
Keyword(s):  
Elastic Constants ◽  
Periodic Structures ◽  
Mass Density ◽  
Density Ratio ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Band Gaps ◽  
Homogenization Theory ◽  
Dominant Factor ◽  
Phononic Band Gaps

In this study, we investigate band structures of phononic crystals with particular emphasis on the effects of the mass density ratio and of the contrast of elastic constants. The phononic crystals consist of arrays of different media embedded in a rubber or epoxy. It is shown that the density ratio rather than the contrast of elastic constants is the dominant factor that opens up phononic band gaps. The physical background of this observation is explained by applying the theory of homogenization to investigate the group velocities of the low-frequency bands at the center of symmetry Γ.

scholarly journals Band Gaps and Vibration Isolation of a Three-dimensional Metamaterial with a Star Structure

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3812 ◽  
Author(s):  
Heng Jiang ◽  
Mangong Zhang ◽  
Yu Liu ◽  
Dongliang Pei ◽  
Meng Chen ◽  
...  
Keyword(s):  
Band Gap ◽  
Vibration Isolation ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Mass Density ◽  
Three Dimensional ◽  
Low Frequency ◽  
Band Gaps ◽  
Acoustic Metamaterials ◽  
Star Structure

Elastic metamaterials have promising applications in wave control and vibration isolation, due to their extraordinary characteristics, e.g., negative Poisson ratio, band gaps, effective negative mass density and effective negative modulus. How to develop new functional metamaterials using a special structure has always been a hot topic in this field. In this study, a three-dimensional (3D) star structure is designed to construct metamaterials with both negative static and dynamic properties. The results show that the 3D star structure formed a wide band gap at lower frequency and had a negative Poisson’s ratio. Different from conventional acoustic metamaterials, the main physical mechanism behind the low-frequency band gap of the 3D star structure is the resonance mode formed by the bending deformation of each rib plate, which made it easier to achieve effective isolation of low-frequency elastic waves with a low mass density. In addition, many structural parameters of the 3D star structure can be modulated to effectively adjust the band gap frequency by changing the angle between the concave nodes and aspect ratio. This study provides a new way to design the 3D acoustic metamaterials and develop the lightweight vibration isolation devices.

Vibration Isolation Design for Periodical Stiffened Shells by the Wave Finite Element Method

2017 ◽  
Author(s):  
Jie Hong ◽  
Xueqing He ◽  
Dayi Zhang ◽  
Yanhong Ma
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Band Gap ◽  
Vibration Isolation ◽  
Band Gaps ◽  
Vibration Band ◽  
Frequency Range ◽  
Gap Characteristics ◽  
Plates And Shells ◽  
Element Method

Thin plates and shells are widely used to reduce the weight in modern mechanical systems, in particularly for the aeronautic and astronautical machineries. These thin structures can result in intensive modes, and lead to the difficulty on the suppression of vibration. The excessive vibration of casing can not only lead to the failure itself but also has a significant influence on the related external pipelines and other attachments which could cause the fatigue failure for the aero-engine casings. A proper method is needed to investigate the dynamic characteristics for these casings, and to be potentially further used for the vibration isolation design. Periodic structure has received a great deal of attentions for its band gap characteristics. Sound and other vibration can be forbidden to propagate in its band gap. With regard to the applications in aero-engines, the article provides one probable vibration isolation method for the stiffened plates and shells with high strength-to-weight ratio and with periodic configuration characteristics. The vibration characteristics of the stiffened shell are usually difficult to be acquired, and there is neither an analytical solution for the complicated stiffeners configuration. Therefore, a Wave finite element method (FEM) based on the wave theory and finite element method, which can solve the dynamic response and band gap characteristics of casings with wide frequency band is presented. Taking the characteristics of the curvature into account, it is proposed for how to confirm the periodic boundaries of the shells. Moreover, the finite element model built by ANSYS is combined with MATLAB program, and the validity of Wave FEM is proved in shell with different boundaries including free-clamped boundary and free-free boundary. The results reveal that with the increase of stiffeners’ width, wider frequency range and larger attenuating ability appear in the vibration band gap. While with the increase of stiffeners’ thickness, neither the variety of the attenuating capability nor of the frequency range of band gaps is monotone. And the local resonance of stiffeners is obvious, the corresponding band gaps’ contribution to the whole system is little. Moreover, three typical configurations-hexagonal, square and triangular are considered. The configurations of stiffeners have distinct characteristics on the dispersion relation, if the weight problems are not taken into account, the square honeycomb is better than the others.

scholarly journals On the Jump Conditions for Shock Waves in Condensed Materials

2021 ◽  
Author(s):  
R K Anand
Keyword(s):  
Stainless Steel ◽  
Mach Number ◽  
Shock Front ◽  
Particle Velocity ◽  
Mass Density ◽  
Jump Conditions ◽  
Condensed Material ◽  
Material Parameters ◽  
Stainless Steel 304 ◽  
Condensed Materials

Abstract In this article, we have proposed Rankine–Hugoniot (RH) boundary conditions at the normal shock-front which is passing through the condensed material. These RH conditions are quite general, and their convenient forms for the particle velocity, mass density, pressure and temperature have been presented in terms of the upstream Mach number, and the material parameters for the weak and the strong shocks, respectively. Finally, the effects on the mechanical quantities of the shock compressed materials e.g. titanium Ti6Al4V, stainless steel 304, aluminum 6061-T6, etc. have been discussed.

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