scholarly journals Mapping of ultrasonic Lamb-wave field in elastic layered structures using laser probes

2017 ◽  
Author(s):  
Christoph Klieber ◽  
Thilo M. Brill
Keyword(s):  
Wave Field ◽  
Lamb Wave ◽  
Layered Structures ◽  
Laser Probes

Theoretical calculation of circular-crested Lamb wave field in single- and multi-layer isotropic plates using the normal mode expansion method

2019 ◽  
Vol 19 (2) ◽  
pp. 357-372 ◽  
Author(s):  
Lingfang Li ◽  
Mohammad Faisal Haider ◽  
Hanfei Mei ◽  
Victor Giurgiutiu ◽  
Yong Xia
Keyword(s):  
Wave Field ◽  
Normal Mode ◽  
Lamb Wave ◽  
Response Spectrum ◽  
Excitation Frequency ◽  
Expansion Method ◽  
Guided Wave ◽  
Element Analysis ◽  
Mode Expansion ◽  
Isotropic Plates

The guided wave technique is commonly used in the health monitoring of thin-walled structures because the guided waves can propagate far in the structures without much energy loss. However, understanding of the wave propagation in bounded layered structures is still lacking. In this study, the Lamb wave field of single- and multi-layer plates excited by surface-mounted piezoelectric wafer active sensors is theoretically analyzed using the normal mode expansion method, which is based on the elastodynamic reciprocity relation and utilizes the orthogonality relations of the Lamb wave modes. The mode participation factors of Lamb wave in single- and multi-layer isotropic plates are derived. The time domain responses are obtained through the inverse Fourier transform of the structural response spectrum, which is obtained by multiplying the transfer function with the excitation frequency spectrum. The developed normal mode expansion method is first applied to an aluminum single-layer plate. The obtained analytical tuning curves and out-of-plane velocity of the plate are in good agreement with the numerical and experimental results. Finally, the analytical wave responses of an aluminum–adhesive–steel triple-layer plate are verified through comparison with the finite element analysis and experiment. The proposed normal mode expansion method provides a reliable and accurate calculation of the wave field in single- and multi-layer plates.

scholarly journals A0-Mode Lamb Wave Based Detection of Corrosion under Coating Film in Plate-Like Metallic Structures: Analytical, Finite Element and Experimental Studies

2018 ◽  
Vol 5 (1) ◽  
pp. 37-44
Author(s):  
MS Rabbi ◽  
K Teramoto
Keyword(s):  
Wave Field ◽  
Lamb Wave ◽  
Experimental Studies ◽  
Scattered Wave ◽  
Normal Displacement ◽  
Analytical Prediction ◽  
Coating Film ◽  
The Matrix ◽  
Shear Strains ◽  
Overlapping Region

The fundamental order antisymmetric mode (A0-mode) Lamb wave based a quantitative acoustical imaging technique is proposed in this paper to classify the corroded region under coating film within the metallic structure. This method estimates versatility qualities of the zone of intrigue to some degree inhomogeneity differentiated to the encompassed materials. However, a converging region consisting of incident wave field and scattered wave field difficult to demonstrate from the observed signals. The proposed method focuses on reconstructing the image of the defect by calculating the shear strains. The shear strains deduced from the observed normal displacement of the specimen. A covariance matrix has been constructed using the shear strains and meaningful determinant values of the matrix reveal the overlapping region. As the beginning overlapping region developed at the edge of the defect, thus image of the defect can be reconstructed by this technique. This paper discussed the analytical approach of computing the incoming, outgoing, as well as the transmitting wave fields. Physical interpretation of the analytical prediction is explored via numerical simulations and acoustical observations. GUB JOURNAL OF SCIENCE AND ENGINEERING, Vol 5(1), Dec 2018 P 37-44

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