scholarly journals Measurement of Lamb waves dispersion curves under narrowband monomode excitation using TV holography

2006 ◽  
Author(s):  
J. Luis Deán ◽  
José L. Fernández ◽  
Ángel F. Doval ◽  
Cristina Trillo
Keyword(s):  
Lamb Waves ◽  
Dispersion Curves

Dielectric and Mechanical Loading Effects of a Fluid on Lamb Waves Propagating in an Immersed Piezoelectric Plate

2005 ◽  
Vol 21 (3) ◽  
pp. 179-186 ◽  
Author(s):  
C.-H. Yang ◽  
Y.-A. Lai
Keyword(s):  
Lamb Waves ◽  
Piezoelectric Plate ◽  
Dispersion Curves ◽  
Partial Wave Analysis ◽  
Theoretical Treatment ◽  
Fluid Loading ◽  
Wave Analysis ◽  
Sensor Applications ◽  
Dielectric Loading ◽  
Loading Effects

AbstractThis research is focused on exploring the fluid loading effects on the dispersion curves of Lamb modes propagating in a piezoelectric plate. A theoretical treatment based on a partial wave analysis is developed to model the dispersion curves of Lamb modes propagating in an X-LiNbO3 plate loaded by a fluid with combined mechanical/dielectric properties. In particular, the mode-shifting characteristics caused by the fluid loading as a function of the propagation orientation are illustrated with numerical examples. Finally, for the case of water as an immersing fluid, individual attributions of the mechanical and dielectric loading effects causing the mode-shifting are analyzed. It is found that the dielectric loading effect dominates the mode-shifting while the mechanical density loading can be neglected while Lamb waves propagate in an X-LiNbO3 plate immersing in water. The current results provides useful information for the applications of acoustic plate mode (APM) devices used in liquid sensor applications.

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.

Validation of Dispersion Curve Reconstruction Techniques for the A0 and S0 Modes of Lamb Waves

2014 ◽  
Vol 14 (07) ◽  
pp. 1450024 ◽  
Author(s):  
Lina Draudvilienė ◽  
Renaldas Raišutis ◽  
Egidijus Žukauskas ◽  
Audrius Jankauskas
Keyword(s):  
Phase Velocity ◽  
Structural Changes ◽  
Lamb Waves ◽  
High Sensitivity ◽  
Dispersion Curves ◽  
Curve Reconstruction ◽  
Informative Signal ◽  
Zero Crossing ◽  
Reconstruction Methods ◽  
Phase Velocity Dispersion

The properties of ultrasonic Lamb waves, such as relatively small attenuation and high sensitivity to structural changes of the object being investigated, allow performing of non-destructive testing of various elongated structures like pipes, cables, etc. Due to the dispersion effect of Lamb waves, a waveform of the received informative signal is usually distorted, elongated and overlapping in the time domain. Therefore, in order to investigate objects using the ultrasonic Lamb waves and to reconstruct the dispersion curves, it is necessary to know the relationship between frequency, phase and group velocities and thickness of the plate. The zero-crossing technique for measurement of phase velocity of Lamb waves (the A0 and S0 modes) has been investigated using modelled dispersed signals and experimental signals obtained for an aluminium plate having thickness of 2 mm. A comparison between two reconstruction methods of Lamb wave phase velocity dispersion curves, namely, the two-dimensional fast Fourier transform (2D-FFT) and zero-crossing technique, along with the theoretical (analytical) dispersion curves is presented. The results indicate that the proposed zero-crossing method is suitable for use in reconstruction of dispersion curves in the regions affected by strong dispersion, especially for the A0 mode.

Stopband edges in the dispersion curves of Lamb waves propagating in piezoelectric periodical structures

1988 ◽  
Vol 53 (19) ◽  
pp. 1806-1808 ◽  
Author(s):  
A. Alippi ◽  
F. Craciun ◽  
E. Molinari
Keyword(s):  
Lamb Waves ◽  
Dispersion Curves

Lamb Wave-Based Damage Location Detection Method of Composite Plate

2011 ◽  
Vol 301-303 ◽  
pp. 1260-1266
Author(s):  
Li Shao Zhang ◽  
Huan Guo Chen ◽  
Jian Min Li ◽  
Li Tian
Keyword(s):  
Group Velocity ◽  
Lamb Wave ◽  
Composite Laminates ◽  
Composite Plate ◽  
Velocity Dispersion ◽  
Lamb Waves ◽  
Group Velocity Dispersion ◽  
Dispersion Curves ◽  
Damage Location ◽  
The Difference

To understand more about Lamb waves on composite laminates damage detection features, the Lamb wave group velocity dispersion curves are calculated and plotted by using dichotomy method in MATLAB. The signal parameters are chosen according to Group velocity dispersion curves. The dynamic response signals of the composite plate are obtained by finite element method. Damage location is calculated by the actual group velocity of Lamb wave and time of flight of the difference signal before and after damage.

Lamb waves dispersion curves for diamond based piezoelectric layered structure

2016 ◽  
Vol 108 (11) ◽  
pp. 113501 ◽  
Author(s):  
B. P. Sorokin ◽  
G. M. Kvashnin ◽  
A. V. Telichko ◽  
A. S. Novoselov ◽  
S. I. Burkov
Keyword(s):  
Layered Structure ◽  
Lamb Waves ◽  
Dispersion Curves ◽  
Piezoelectric Layered Structure
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