Suppressing Technique of the Antisymmetric Mode by the Superposition of Lamb Waves Generated by Two Laser Beams in a Thin Plate

2006 ◽  
Vol 321-323 ◽  
pp. 103-107
Author(s):  
Seung Seok Lee ◽  
Sang Whoe Dho
Keyword(s):  
Thin Plate ◽  
Opposite Direction ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Mode ◽  
Laser Beams ◽  
Symmetric Mode ◽  
Antisymmetric Mode

We present a suppressing technique of the antisymmetric mode by superposition of Lamb waves generated by two laser beams in a thin plate. Two Lamb waves of the same frequency propagating from the opposite direction simultaneously arrive at the point of measurement and are superposed to compose one Lamb wave. The amplitude of the superposed Lamb wave depends on the distance between two laser beams. The suppressing of antisymmetric Lamb wave mode is accomplished by selecting the distance between two beams which simultaneously satisfies the condition of the anti-node(maximum) for the symmetric mode and the minimum for the antisymmetric mode. By this method, the antisymmetric Lamb wave mode is suppressed to the degree of 1.4% of the amplitude measured at zero distance between two beams.

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.

Notice of Removal: Zero TCF resonator based on S0 Lamb wave mode in AlN thin plate films

2017 ◽  
Author(s):  
Mohammed Moutaouekkil ◽  
Abdelkrim Talbi ◽  
Omar Elmazria ◽  
El Houssaine El Boudouti ◽  
Philippe Pernod ◽  
...  
Keyword(s):  
Thin Plate ◽  
Lamb Wave ◽  
Wave Mode

scholarly journals Leaky Lamb Wave Radiation from a Waveguide Plate with Finite Width

2020 ◽  
Vol 10 (22) ◽  
pp. 8104
Author(s):  
Sang-Jin Park ◽  
Hoe-Woong Kim ◽  
Young-Sang Joo
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Mode ◽  
Wave Radiation ◽  
Finite Width ◽  
Propagation Characteristics ◽  
Radiation Characteristics ◽  
Radiation Beam ◽  
Leaky Lamb Wave ◽  
Waveguide Sensor

In this paper, leaky Lamb wave radiation from a waveguide plate with finite width is investigated to gain a basic understanding of the radiation characteristics of the plate-type waveguide sensor. Although the leaky Lamb wave behavior has already been theoretically revealed, most studies have only dealt with two dimensional radiations of a single leaky Lamb wave mode in an infinitely wide plate, and the effect of the width modes (that are additionally formed by the lateral sides of the plate) on leaky Lamb wave radiation has not been fully addressed. This work aimed to explain the propagation behavior and characteristics of the Lamb waves induced by the existence of the width modes and to reveal their effects on leaky Lamb wave radiation for the performance improvement of the waveguide sensor. To investigate the effect of the width modes in a waveguide plate with finite width, propagation characteristics of the Lamb waves were analyzed by the semi-analytical finite element (SAFE) method. Then, the Lamb wave radiation was computationally modeled on the basis of the analyzed propagation characteristics and was also experimentally measured for comparison. From the modeled and measured results of the leaky radiation beam, it was found that the width modes could affect leaky Lamb wave radiation with the mode superposition and radiation characteristics were significantly changed depending on the wave phase of the superposed modes on the radiation surface.

Temperature compensation of lamb wave sensor by combined antisymmetric mode and symmetric mode

2008 ◽  
Vol 92 (7) ◽  
pp. 074101 ◽  
Author(s):  
Feng Li ◽  
Yihui Wu ◽  
Jean-François Manceau ◽  
François Bastien
Keyword(s):  
Lamb Wave ◽  
Temperature Compensation ◽  
Symmetric Mode ◽  
Antisymmetric Mode

scholarly journals Investigation of the relationship between the Lamb waves phase velocity and the technical condition of housing and utilities pipelines

2020 ◽  
Vol 216 ◽  
pp. 01080
Author(s):  
A.A. Ibadov ◽  
A.E. Kondrat'ev ◽  
D.A. Makueva ◽  
D.V. Sergeeva
Keyword(s):  
Phase Velocity ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Mode ◽  
Technical Condition ◽  
Propagation Parameters ◽  
The Relationship

The article describes a method for determining the dependence of the Lamb waves phase velocity on the technical condition of housing and utilities pipelines, using the example of thin two-layer segments. Variations in the thickness of the considered pipeline affect the propagation parameters of the Lamb wave mode.

scholarly journals Nonpenetrating Damage Identification Using Hybrid Lamb Wave Modes from Hilbert-Huang Spectrum in Thin-Walled Structures

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Zijian Wang ◽  
Pizhong Qiao ◽  
Binkai Shi
Keyword(s):  
Lamb Wave ◽  
Damage Identification ◽  
Lamb Waves ◽  
Wave Mode ◽  
Thin Walled Structures ◽  
Damage Indices ◽  
Thin Walled ◽  
Experimental Validations ◽  
The One ◽  
Wave Modes

Lamb waves have shown promising advantages for damage identification in thin-walled structures. Multiple modes of Lamb wave provide diverse sensitivities to different types of damage. To sufficiently utilize damage-related wave features, damage indices were developed by using hybrid Lamb wave modes from Hilbert-Huang spectra. Damage indices were defined as surface integrals of Hilbert-Huang spectra on featured regions determined by time and frequency windowing. The time windowing was performed according to individual propagation velocity of different Lamb wave mode, while the frequency windowing was performed according to the frequency of excitation. By summing damage indices for all transmitter-receiver pairs, pixels were calculated to reconstruct a damage map to characterize the degree of damage at each location on structure. Both numerical and experimental validations were conducted to identify a nonpenetrating damage. The results demonstrated that the proposed damage indices using hybrid Lamb wave modes are more sensitive and robust than the one using single Lamb wave mode.

Damage Detection in Thick Steel Beam Using Lamb Waves

2008 ◽  
Author(s):  
Kai Sun ◽  
Guang Meng ◽  
Fucai Li ◽  
Lin Ye ◽  
Ye Lu
Keyword(s):  
Damage Detection ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Fem Simulation ◽  
Wave Mode ◽  
Thin Plates ◽  
Steel Beams ◽  
Thick Steel ◽  
Number Of Cycles ◽  
Detection And Localization

Different from the mostly concerned Lamb wave-based damage detection for thin plates, this paper presents a diagnosis procedure on thick steel beams with thickness of 34 mm. The diagnosis strategy and specimens were first described, and some parameters, such as the frequency and the number of cycles of the diagnostic waveform, were discussed. Based on finite element method (FEM) simulation, the experiment configuration was addressed, results from which show good similarity between the outcomes from the simulations and those from the experiments. Wavelet transform was further used to process the acquired Lamb wave signals for the purpose of damage detection and localization. Meanwhile, the velocity of the Lamb waves was calculated, illustrating that the fundamental anti-symmetric (A0) Lamb wave mode was excited in this case. The results demonstrate that Lamb waves can also be applied to some thick structures for the purpose of structural health monitoring.

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