Silicon Pillars as Resonators in an Acoustical Metamaterial

2014 ◽  
Author(s):  
Bernard Bonello ◽  
Rémi Marchal ◽  
Rayisa Moiseyenko ◽  
Yan Pennec ◽  
Bahram Djafari-Rouhani ◽  
...  
Keyword(s):  
Thin Plate ◽  
Lamb Waves ◽  
Mass Density ◽  
Resonant Mode ◽  
Ultrasonic Technique ◽  
Frequency Range ◽  
Negative Mass ◽  
Laser Ultrasonic ◽  
Compressional Mode ◽  
Bending Modes

We have investigated the propagation of Lamb waves in structures made of either an isolated resonant pillar or a set of pillars arranged in a line on a thin plate. The resonators as well as the plate are made of silicon. FEM computations show that two bending modes and one compressional mode are unambiguously identified in the frequency range of interest (0–10 MHz). We used a laser ultrasonic technique to map both the amplitude and the phase of the normal displacements on top of the pillars and at the surface of the sample. When the frequency is tuned to a resonant mode, either compressional or bending, the pillars vibrate 180° out-of-phase with respect to the Lamb waves, resulting in a negative modulus or negative mass density respectively.

Metamaterials With Tunable Stop Bands

2008 ◽  
Author(s):  
H. H. Huang ◽  
C. T. Sun
Keyword(s):  
Energy Flow ◽  
Degrees Of Freedom ◽  
Numerical Solutions ◽  
Mass Density ◽  
Stop Band ◽  
Internal Mass ◽  
Frequency Range ◽  
Negative Mass ◽  
One Dimensional ◽  
Internal Degrees Of Freedom

Metamaterials are materials with manmade microstructures. Recently, researchers have looked at a class of metamaterials whose microstructures contain internal degrees of freedom that are different from those of the macro-medium. These metamaterials exhibit unusual dynamic behavior and if modeled as homogeneous solids then their effective mass densities would become negative in certain frequency range. Specifically, a new stop band in the vicinity of the local resonance frequency of the internal mass in the microstructure would result. In this paper, a one dimensional metamaterial is employed to investigate the meaning of the negative mass density in the material and the energy flow in and out of the microstructure. In addition, numerical solutions are used to illustrate the phenomenon.

Absolute Single-Mode Lamb Wave Generation by Laser in a Thin Plate

2006 ◽  
Vol 321-323 ◽  
pp. 108-111
Author(s):  
Seung Seok Lee ◽  
Sang Whoe Dho
Keyword(s):  
Thin Plate ◽  
Lamb Wave ◽  
Single Mode ◽  
Wave Mode ◽  
Wave Generation ◽  
Laser Beams ◽  
Special Technique ◽  
Ultrasonic Technique ◽  
Laser Ultrasonic ◽  
Mode Operation

We present a laser-ultrasonic technique to generate the lowest symmetric ( ) Lamb wave in a thin plate. Using this special technique, in which two symmetric laser beams quasi-simultaneously hit at the same point on both sides of the plate, we absolutely suppress anti-symmetric Lamb wave modes. This technique is applicable to any situation that requires symmetric Lamb wave mode operation and does not need additional contacts or special equipments.

An elastic metamaterial with simultaneously negative mass density and bulk modulus

2011 ◽  
Vol 98 (25) ◽  
pp. 251907 ◽  
Author(s):  
X. N. Liu ◽  
G. K. Hu ◽  
G. L. Huang ◽  
C. T. Sun
Keyword(s):  
Bulk Modulus ◽  
Mass Density ◽  
Negative Mass

Design of a Variable Thickness Plate to Focus Bending Waves

2012 ◽  
Author(s):  
Noah H. Schiller ◽  
Sz-Chin Steven Lin ◽  
Randolph H. Cabell ◽  
Tony Jun Huang
Keyword(s):  
Numerical Simulations ◽  
Thin Plate ◽  
Traveling Waves ◽  
Variable Thickness ◽  
Focal Point ◽  
Frequency Range ◽  
Additional Energy ◽  
Broad Frequency Range ◽  
Bending Waves ◽  
Energy Dissipated

This paper describes the design of a thin plate whose thickness is tailored in order to focus bending waves to a desired location on the plate. Focusing is achieved by smoothly varying the thickness of the plate to create a type of lens, which focuses structure-borne energy. Damping treatment can then be positioned at the focal point to efficiently dissipate energy with a minimum amount of treatment. Numerical simulations of both bounded and unbounded plates show that the design is effective over a broad frequency range, focusing traveling waves to the same region of the plate regardless of frequency. This paper also quantifies the additional energy dissipated by local damping treatment installed on a variable thickness plate relative to a uniform plate.

Novel negative mass density resonant metamaterial unit cell

2015 ◽  
Vol 379 (1-2) ◽  
pp. 33-36 ◽  
Author(s):  
Norbert Cselyuszka ◽  
Milan Sečujski ◽  
Vesna Crnojević-Bengin
Keyword(s):  
Mass Density ◽  
Unit Cell ◽  
Negative Mass

A design of active elastic metamaterials with negative mass density and tunable bulk modulus

2018 ◽  
Vol 230 (3) ◽  
pp. 1003-1008 ◽  
Author(s):  
Sheng Sang ◽  
Anwer Mhannawee ◽  
Ziping Wang
Keyword(s):  
Bulk Modulus ◽  
Mass Density ◽  
Negative Mass ◽  
Elastic Metamaterials

The study of ultrasonic longitudinal velocities for nanostructured NiAl alloys by laser ultrasonic technique

1998 ◽  
Vol 105 (9) ◽  
pp. 601-604 ◽  
Author(s):  
Yinglei Du ◽  
Baimei Wu ◽  
Xiaorong Zhang ◽  
Xiaoyin Qin
Keyword(s):  
Ultrasonic Technique ◽  
Laser Ultrasonic

Noncontact Evaluation of Defects in Thin Plate With Multimodes Lamb’s Waves and Wavelet Transform

2002 ◽  
Author(s):  
Morimasa Murase ◽  
Koichiro Kawashima
Keyword(s):  
Group Velocity ◽  
Thin Plate ◽  
Wavelet Transformation ◽  
Velocity Dispersion ◽  
Lamb Waves ◽  
Group Velocity Dispersion ◽  
Dispersion Curves ◽  
Contact Method ◽  
Intact Specimen ◽  
Time Frequency

Multimode’s Lamb waves in aluminum plates with various defects were excited by a Q-switched Nd:YAG laser. The Lamb waves past through the defects were received a laser interferometer. The received signals of the Lamb waves are processed by the wavelet transformation. The wavelet transformation is generally shown on the time-frequency domain. By dividing a propagation distance by the time, the group velocities are identified. In this way, group velocity dispersion maps of multimode’s Lamb waves are constructed with the received temporal signals. By changing the shape of the mother wavelet, Gabor function, we can identify the dispersion curves of the higher mode Lamb waves. The group velocity dispersion maps of a intact specimen agree well on theoretical dispersion curves of S0, A0, S1, A1, S2, A2, and A3 modes. The difference between the dispersion maps of the intact specimen and that with defects clearly visualizes the existence of defects. This non-contact method is effective for inspecting various defects in thin plate structures.

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