EFFICIENT PERTURBATION ANALYSIS OF LAMB WAVE DISPERSION CURVES

This study presents a noncontact sensing technique with ultrasonic wave propagation imaging algorithm, for damage visualization of liquid-immersed structures. An aluminum plate specimen (400 mm × 400 mm × 3 mm) with a 12 mm slit was immersed in water and in glycerin. A 532 nm Q-switched continuous wave laser is used at an energy level of 1.2 mJ to scan an area of 100 mm × 100 mm. A laser Doppler vibrometer is used as a noncontact ultrasonic sensor, which measures guided wave displacement at a fixed point. The tests are performed with two different cases of specimen: without water and filled with water and with glycerin. Lamb wave dispersion curves for the respective cases are calculated, to investigate the velocity-frequency relationship of each wave mode. Experimental propagation velocities of Lamb waves for different cases are compared with the theoretical dispersion curves. This study shows that the dispersion and attenuation of the Lamb wave is affected by the surrounding liquid, and the comparative experimental results are presented to verify it. In addition, it is demonstrated that the developed fully noncontact ultrasonic propagation imaging system is capable of damage sizing in submerged structures.

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Reconstruction of Lamb wave dispersion curves by sparse representation with continuity constraints

The Journal of the Acoustical Society of America ◽

10.1121/1.4974063 ◽

2017 ◽

Vol 141 (2) ◽

pp. 749-763 ◽

Cited By ~ 10

Author(s):

Wenbo Zhao ◽

Ming Li ◽

Joel B. Harley ◽

Yuanwei Jin ◽

José M. F. Moura ◽

...

Keyword(s):

Sparse Representation ◽

Lamb Wave ◽

Wave Dispersion ◽

Dispersion Curves

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A Point-Focus PVDF Transducer for Lamb Wave Measurements

Journal of Mechanics ◽

10.1017/s1727719100001994 ◽

2002 ◽

Vol 18 (1) ◽

pp. 29-33

Author(s):

Yung-Chun Lee ◽

Yi Fan Tein ◽

Yu Yi Chao

Keyword(s):

Lamb Wave ◽

Acoustic Waves ◽

Lamb Waves ◽

Experimental Testing ◽

Spherical Shape ◽

Wave Dispersion ◽

Dispersion Curves ◽

Pvdf Film ◽

Wave Measurements ◽

Metal Plates

ABSTRACTThis paper reports the development of a point-focused PVDF transducer with a large aperture surface and its application on measuring Lamb wave dispersion curves. The point-focused transducer is constructed by forcing a piezoelectric PVDF film into a concave spherical shape. The acoustic waves radiated from the PVDF film are then focused into a point without using any acoustic lens. Similar to its line-focused counterpart, the point-focused transducer is capable of measuring dispersion curves of lamb waves provided its aperture angle is large enough. To verify this, experimental testing is carried out on several thin metal plates and good measurement results are observed. Future improvements and applications on the transducer will be addressed.

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