Propagation of pulsed ultrasonic fields in a band gap of a two dimensional phononic crystal

2015 ◽  
Vol 138 (3) ◽  
pp. 1751-1751
Author(s):  
Ukesh Koju ◽  
Joel Mobley
Keyword(s):  
Band Gap ◽  
Phononic Crystal ◽  
Two Dimensional ◽  
Ultrasonic Fields ◽  
Pulsed Ultrasonic

Frequency characteristics of defect states in a two-dimensional phononic crystal with slit structure

2016 ◽  
Vol 30 (06) ◽  
pp. 1650025 ◽  
Author(s):  
X. P. Wang ◽  
P. Jiang ◽  
T. N. Chen ◽  
K. P. Yu
Keyword(s):  
Band Gap ◽  
Power Transmission ◽  
Phononic Crystal ◽  
Slit Width ◽  
Band Gaps ◽  
Theoretical Research ◽  
Two Dimensional ◽  
Defect States ◽  
Band Frequency ◽  
Practical Applications

In this paper, the defect state and band gap characteristics in a two-dimensional slit structure phononic crystal, consisting of slotted steel tubes embedded in an air matrix, are investigated theoretically and experimentally. Using the finite element method and supercell technique, the dispersion relationships and power transmission spectra of the slit structures are calculated. The vibration modes of the band gap edges are analyzed to clarify the mechanism of the generation of the band gaps. Additionally, the influence of the slit width on the band gaps in slit structure is investigated. The slit width was found to influence the band gaps; this is critical to understand for practical applications. Based on this finding, a method to form defect scatterers by changing the slit width of a single central scatterer, or one row of scatterers, in the perfect PC was developed. Defect bands can be induced by creating defects inside the original complete band gaps. The frequency can then be tuned by changing the slit width of defect scatterers. Meanwhile, the relationship between point defect and line defect is investigated. Finally, we verify the results of theoretical research by experiments. These results will help in fabricating devices such as acoustic filters and waveguides whose band frequency can be modulated.

scholarly journals Experimental study of guiding and filtering of acoustic waves in a two dimensional ultrasonic crystal

2005 ◽  
Vol 220 (9-10) ◽  
Author(s):  
Abdelkrim Khelif ◽  
Abdelkrim Choujaa ◽  
Sarah Benchabane ◽  
Bahram Djafari-Rouhani ◽  
Vincent Laude
Keyword(s):  
Band Gap ◽  
Acoustic Waves ◽  
Theoretical Study ◽  
Phononic Crystal ◽  
Wide Frequency Range ◽  
Two Dimensional ◽  
Full Band ◽  
Side Walls ◽  
Difference Time ◽  
Good Agreement

AbstractWe present a combined experimental and theoretical study of the guiding, bending and filtering of acoustic waves in an ultrasonic crystal. The crystal consists of a two-dimensional periodical array of steel rods immersed in water, for wich a complete acoustic band gap extending from 240 to 325 kHz is found experimentally. Waveguides for acoustic waves are further created by removing a line defect, on which stubs can be added by removing rods from the side-walls of the waveguide. Full transmission is observed for a one-period-wide straight waveguide within the full-band-gap of the perfect phononic crystal, i.e. for a waveguide aperture smaller than one acoustic wavelength. Waveguiding over a wide frequency range is also obtained for a one-period-wide waveguide with two sharp 90° bends. Finite-difference time-domain computations are found to be in good agreement with the measurements in all experimental configurations.

Influence of Point Defects on Band Gaps of Fe-Epoxy in Two-Dimensional Phononic Crystal

2013 ◽  
Vol 652-654 ◽  
pp. 1377-1382
Author(s):  
Jiao He ◽  
Guang Hui Fan ◽  
De Xun Zhao ◽  
Ying Kai Liu
Keyword(s):  
Point Defect ◽  
Band Gap ◽  
Nearest Neighbor ◽  
Phononic Crystal ◽  
Expansion Method ◽  
Band Gaps ◽  
Two Dimensional ◽  
Defect States ◽  
Filling Fraction ◽  
Nearest Neighbor Coupling

The band gap of a new two-dimensional phononic crystal was studied by the plane-wave expansion method. The two-dimensional phononic crystal is formed by square-shape array geometry of iron cylinders with square cross section inserted in an epoxy resin. The band gaps of different structures were calculated such as defect-free, single cavity crystal point defect states, crystal point defect states with (10) direction coupling, crystal point defect states with (10) direction next-nearest-neighbor coupling, and crystal point defect states with (11) direction next-nearest-neighbor coupling. Compared with that of defect-free, it is conclude that point defect is beneficial to the production of band gaps. The bandwidth of point defect is about 5 times larger than that of the defect-free crystal with the filling fraction F=0.4. In addition, the maximum number of band gap is in the crystal point defect states with (10) direction next-nearest-neighbor coupling. It will provide a theoretical reference for the manufacture of phononic crystal.

Band Gaps of a Two-Dimensional Periodic Graphenelike Structure

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Zi-Gui Huang ◽  
Chun-Fu Su
Keyword(s):  
Acoustic Wave ◽  
Band Gap ◽  
Phononic Crystal ◽  
Chain Structure ◽  
Gap Effect ◽  
Two Dimensional ◽  
Acoustic Wave Propagation ◽  
Bloch’S Theorem ◽  
Acoustic Wave Device ◽  
Wave Device

This study constructs a new phononic crystal acoustic wave device that adopts a graphenelike structure and is composed of piezoelectric zinc oxide (ZnO) material. We employed the finite-element method to determine periodic boundary conditions. Following Bloch's theorem, we analyzed the acoustic wave propagation of the proposed graphenelike structure in the frequency domain to understand the band gap effect and oscillation behavior. We also investigated the band gap variation and modal distortion tendencies of the piezoelectric ZnO material in the two-dimensional graphenelike structure under the condition of changing chain structure diameters and bonding rod widths between the atoms columns to develop an optimal acoustic wave device.

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