Mechanism of band gaps in self-similar triangular lattice with Koch fractal

2021 ◽  
pp. 1-17
Author(s):  
Pengcheng Zhao ◽  
Cheng Zhao ◽  
Kai Zhang ◽  
Zichen Deng
Keyword(s):  
Finite Element ◽  
Triangular Lattice ◽  
Vibration Suppression ◽  
Low Frequency ◽  
Band Gaps ◽  
Band Edge ◽  
Periodic Lattice ◽  
Finite Element Software ◽  
Iteration Number ◽  
Koch Fractal

Abstract Fractal lattice is a kind of lattices with multifunctional physical characteristics and superior mechanical properties. The wave propagation of the triangular lattice with Koch fractal is calculated by the finite element method and Bloch theorem. The effects of the iteration number on the band gaps and the band edge modes are studied. The finite element software was used to simulate the dynamic response of the triangular lattice with Koch fractal for verifying the vibration suppression performance. The results show that the triangular lattice with Koch fractal can produce multiple and low-frequency band gaps. As an increase of the iteration number, the band gap gradually shifts to a lower frequency. By comparing and analyzing the band edge modes and the eigenmodes of Koch fractal, the mechanisms of the band gaps within the low-frequency ranges are analyzed and discussed in detail. Additionally, the band edge modes exhibit similar vibration modes. Finally, the simulation results of the finite lattice verify the broadband vibration suppression performance of the triangular lattice with Koch fractal. This work provides insights into the lattice dynamic behavior adjusted by Koch fractal, which is beneficial to the periodic lattice for suppressing vibration in engineering applications.

scholarly journals Elastic Wave Propagation in Lattice Metamaterials with Koch Fractal

2020 ◽  
Vol 33 (5) ◽  
pp. 600-611 ◽  
Author(s):  
Pengcheng Zhao ◽  
Kai Zhang ◽  
Zichen Deng
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Vibration Isolation ◽  
Band Gaps ◽  
Dynamic Responses ◽  
Analytical Models ◽  
Band Structures ◽  
Finite Element Software ◽  
Directional Wave ◽  
Koch Fractal

Abstract In this study, the wave propagation properties of lattice metamaterials with Koch fractal structures are investigated in terms of band structures and directional wave propagation. The analytical models of lattice metamaterials are established using the finite element method, and the dispersion relation is solved using the Bloch’s theorem. The band structures of the lattice metamaterials with different numbers of iterations are studied, and the group velocities at a selected frequency are calculated to analyze the directional wave propagation characteristics. Furthermore, dynamic responses of the finite structures are calculated using commercial finite element software to verify the band gaps and directional wave propagation behaviors in the lattice metamaterials. The results show that multiple and low band gaps are present in the lattice materials with various geometric parameters of the Koch fractal, and the position of the lowest band gap decreases as the number of iterations increases. The results indicate the potential applications of lattice metamaterials with Koch fractals for vibration isolation and multi-functional design.

scholarly journals Metal Ceramic Segmented Ring Transducer under Deep Submergence Conditions

2017 ◽  
Vol 67 (6) ◽  
pp. 612
Author(s):  
Subash Chandrabose M R ◽  
Shan Victor Pereira ◽  
Jayakumar B ◽  
Ebenezer D. D.
Keyword(s):  
Finite Element ◽  
High Pressure ◽  
Low Cost ◽  
Low Frequency ◽  
Test Facility ◽  
Voltage Response ◽  
Performance Parameters ◽  
Finite Element Software ◽  
Pressure Test ◽  
Metal Ceramic

<p class="p1">Segmented ring transducers are widely used for low frequency, broadband, deep submergence applications. These transducers can be made out of piezoceramic wedges or slabs and metallic wedges. Higher diameter, low frequency transducers are generally made out of piezoceramic slabs and metal wedges due to ease of manufacture and low cost. In this paper, metal ceramic segmented ring transducers are modelled using ATILA, a finite element software for the design of underwater transducers. Transducer variants were modelled with different wedge and piezoceramic materials. Transducers modelled were manufactured, assembled and tested. Various stages of manufacture like piezoceramic stacking, transducer assembly, pre-stressing with fibre winding, and encapsulation are explained. Acoustic performances of the transducers manufactured were measured in an open tank and inside a pressurised vessel from 10 bar to 70 bar. Performance parameters like resonance frequency, transmitting voltage response and directivity were measured. Results indicate that the transducer has usable bandwidth of about two octaves and stable response. One of the transducers was also tested in a high pressure test facility at 600 bar to check its pressure withstanding capability.</p>

Flexural Wave Propagation Characteristics of Lattice Sandwich Plates

2013 ◽  
Vol 753-755 ◽  
pp. 857-860 ◽  
Author(s):  
Shu Lang Tao ◽  
Gui Lan Yu ◽  
Zong Jian Yao
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Band Gaps ◽  
Comsol Multiphysics ◽  
Flexural Wave ◽  
Sandwich Plates ◽  
Propagation Characteristics ◽  
Finite Element Software ◽  
Flexural Wave Propagation ◽  
Lattice Pattern

This paper is aimed to study flexural wave propagation characteristics of lattice sandwich plates. Based on Blochs theorem, band structure of flexural wave propagation in the plate is obtained by commercial finite element software Comsol Multiphysics. Meanwhile, frequency response is obtained and its maximum attenuation is exactly corresponding to the band gaps. Finally, effects of lattice pattern on band gaps are introduced.

Metamaterial plate with an arrangement of different resonators

2021 ◽  
Vol 263 (2) ◽  
pp. 3987-3998
Author(s):  
Giovanna Pisicchio Zanoni ◽  
Alberto Luiz Serpa
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Frequency Response Function ◽  
Vibration Suppression ◽  
Band Gaps ◽  
The Finite Element Method ◽  
Periodic Cell ◽  
Vibration Attenuation ◽  
Element Method ◽  
Lower Frequencies

Local resonant metamaterials have been widely studied for vibration suppression in the last 20 years. They produce band gaps, which are frequency regions where the wave is not allowed to propagate. They are an alternative to reduce vibration levels at lower frequencies when compared to phononic crystals, which require larger periodic cells to create band gaps at lower frequencies. The most common configuration for a local resonant metamaterial is a periodic cell of a known structure with one attached resonator. In this study, a plate with a periodic cell using two different resonators is analyzed. Some configurations of mass and stiffness for the two resonators will be discussed to pursue the best compromise between a wider band gap and a more considerable vibration attenuation. The dispersion relation for the proposed metamaterial unit cell will be calculated using the Wave Finite Element Method to evaluate these configurations. The frequency response function for a finite structure with the proposed arrangement will also be calculated using the Finite Element Method to compare the results.

Modal Analysis of Water-Lubricated Rubber Stern Bearing Based on ANSYS

2011 ◽  
Vol 291-294 ◽  
pp. 2111-2114
Author(s):  
Yong Jin ◽  
Fang Lan
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Free Boundary ◽  
Modal Analysis ◽  
Low Frequency ◽  
Mode Shapes ◽  
Finite Element Software ◽  
3D Numerical Model ◽  
Rubber Bearings ◽  
Mode Order

With the popularity of the water lubricated rubber stern bearing, researches around rubber bearings are becoming more and more popular in recent years. This paper built a 3D numerical model of water-lubricated rubber stern bearing and did both free boundary and constraint modal analysis using finite element software ANSYS. The results show that free modes of water-lubricated rubber stern bearing are correlating with the constraint modes. The natural frequency distributes intensely in low frequency and the modal shapes mainly focus in the inner lining. Along with mode order increased, the mode shapes become more complicated. The mode shapes mainly embodies in the inner lining.

An Inertant Elastic Metamaterial Plate With Extra Wide Low-Frequency Flexural Band Gaps

2020 ◽  
Vol 88 (2) ◽  
Author(s):  
Xiang Fang ◽  
Kuo-Chih Chuang ◽  
Xiao-Ling Jin ◽  
Dan-Feng Wang ◽  
Zhi-Long Huang
Keyword(s):  
Vibration Suppression ◽  
Low Frequency ◽  
Wide Band ◽  
Band Gaps ◽  
Flexural Wave ◽  
Additional Degree ◽  
Periodic Arrays ◽  
Low Frequency Vibration ◽  
Elastic Metamaterial Plate ◽  
Engineering Vibration

Abstract Arranging inerter arrays in designing metamaterials can achieve low-frequency vibration suppression even with a small configuration mass. In this work, we investigate flexural wave bandgap properties of an elastic metamaterial plate with periodic arrays of inerter-based dynamic vibration absorbers (IDVAs). By extending the plane wave expansion (PWE) method, the inertant elastic metamaterial plate is explicitly formulated in which the interactions of the attached IDVAs and the host plate are considered. Due to the additional degree-of-freedom induced by each IDVA, multiple band gaps are obtained. Along the ΓX direction, the inertant elastic metamaterial plate exhibits two locally resonant (LR) band gaps and one Bragg (BG) band gap. In contrast, along the ΓM direction, two adjacent LR band gaps are obtained. Detailed parametric analyses are conducted to investigate the relationships between the flexural wave bandgap properties and the structural inertant parameters. With a dissipative mechanism added to the IDVAs, extremely wide band gaps in different directions can be further generated. Finally, by adopting an effective added mass technique in the finite element method, displacement transmission and vibration modes of a finite inertant elastic metamaterial plate are obtained. Our investigation indicates that the proposed inertant elastic metamaterial plate has extra-wide low-frequency flexural band gaps and therefore has potential applications in engineering vibration prohibition.

Finite Element Analysis of Flextensional Transducer with Slotted Shell

2012 ◽  
Vol 187 ◽  
pp. 151-154
Author(s):  
Si Chen ◽  
Yu Lan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Resonant Frequency ◽  
Low Frequency ◽  
Maximum Size ◽  
Voltage Response ◽  
Element Analysis ◽  
Finite Element Software ◽  
Acoustic Transducer ◽  
Flextensional Transducer

The study of low frequency, small size transducer was an important aspect for the development of the underwater acoustic transducer. The Class Ⅳ flextensional transducer was a typical low frequency, high-power and small size transducer. For decreasing its resonant frequency in the case of small size, a flextensional transducer with slotted shell was analyzed using finite element software ANSYS. A comparison between the flextensioanl transducer with slotted shell and the Class Ⅳ flextensional transducer was made. The maximum size of the shell is 200mm. The transmitting voltage response of the transducer reaches to 131dB with resonant frequency 600Hz in water. The transducer could radiate at low frequency with small size of the shell.

Finite Element Analysis for Unstiffened Overlapped CHS KK-Joints Welded in Different Ways

2010 ◽  
Vol 163-167 ◽  
pp. 299-306 ◽  
Author(s):  
Xiu Li Wang ◽  
Wen Wei Yang ◽  
Lei Zou
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Low Frequency ◽  
Steel Structure ◽  
Structure Design ◽  
Hysteretic Behavior ◽  
Ultimate Capacity ◽  
Element Analysis ◽  
Finite Element Software ◽  
Better Than

The question whether hidden weld of unstiffened overlapped CHS (circular hollow sections) KK-joints is welded or un-welded is not clearly mentioned in China's steel structure design codes (GB50017-2003) .This paper mainly analyzes the influence of chord-to-brace diameter ratio β, diameter-to- ply ratio γ and brace-to-chord ply ratio τ to the ultimate bearing capacity of the joints with the hidden weld welded and un-welded. The influence of welded and un-welded hidden welds of the joints on hysteretic behavior under low frequency loading is analyzed , and hysteretic curve of the joints are obtained by the finite element software ANSYS. Side brace or opposite brace of the hidden weld of the joints has little influence on the failure modes and ultimate capacity of the joints. Hysteretic behavior of the joints with the hidden weld un-welded is much better than that of the welded.

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