Defect detection and localization in plates using a lamb wave time reversal technique

Time reversal (TR) concept is widely used for Lamb wave-based damage detection. However, the time reversal process (TRP) faces the challenge that it requires two actuating-sensing steps and requires the extraction of re-emitted and reconstructed waveforms. In this study, the effects of the two extracted components on the performance of TRP are studied experimentally. The results show that the two time intervals, in which the waveforms are extracted, have great influence on the accuracy of damage detection of the time reversal method (TRM). What is more, it requires a large number of experiments to determine these two time intervals. Therefore, this paper proposed an efficient time reversal method (ETRM). Firstly, a broadband excitation is applied to obtain response at a wide range of frequencies, and ridge reconstruction based on inverse short-time Fourier transform is applied to extract desired mode components from the broadband response. Subsequently, deconvolution is used to extract narrow-band reconstructed signal. In this method, the reconstructed signal can be easily obtained without determining the two time intervals. Besides, the reconstructed signals related to a series of different excitations could be obtained through only one actuating-sensing step. Finally, the effectiveness of the ETRM for damage detection in composite laminates is verified through experiments.

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Structural health monitoring of plate by using ultrasonic Lamb wave and time reversal, multiple signal classification beam forming.

The Journal of the Acoustical Society of America ◽

10.1121/1.3508733 ◽

2010 ◽

Vol 128 (4) ◽

pp. 2443-2443 ◽

Cited By ~ 1

Author(s):

Je‐Heon Han ◽

Yong‐Joe Kim

Keyword(s):

Structural Health Monitoring ◽

Health Monitoring ◽

Time Reversal ◽

Lamb Wave ◽

Signal Classification ◽

Beam Forming ◽

Multiple Signal Classification ◽

Structural Health ◽

Multiple Signal

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Defects Detection and Localization in Underwater Plates Using Laser Laterally Generated Pure Non-Dispersive S0 Mode

Applied Sciences ◽

10.3390/app9030459 ◽

2019 ◽

Vol 9 (3) ◽

pp. 459 ◽

Cited By ~ 2

Author(s):

Qingnan Xie ◽

Chenyin Ni ◽

Zhonghua Shen

Keyword(s):

Defect Detection ◽

Lamb Waves ◽

Mode Conversion ◽

High Sensitivity ◽

Laser Source ◽

Dispersion Characteristics ◽

High Attenuation ◽

Corrosion Defects ◽

Detection And Localization ◽

Lateral Excitation

When working in humid environments, corrosion defects are easily produced in metallic plates. For defect detection in underwater plates, symmetric modes of Lamb waves are widely used because of their characteristics including long propagating distance and high sensitivity to defects. In this study, we extend our previous work by applying the laser laterally generated S0 mode to detection and localization of defects represented by artificial notches in an aluminum plate immersed in water. Pure non-dispersive S0 mode is generated in an underwater plate by lateral laser source irradiation and its fd (frequency·thickness) range is selected by theoretical calculation. Using this lateral excitation, the S0 mode is enhanced; meanwhile, the A0 mode is effectively suppressed. The mode-converted A0 mode from the incident S0 mode is used to detect and localize the defect. The results reveal a significantly improved capability to detect defects in an underwater plate using the laser laterally generated S0 mode, while that using A0 is limited due to its high attenuation. Furthermore, owing to the long propagating distance and the non-dispersion characteristics of the S0 generated by the lateral laser source, multiple defects can also be detected and localized according to the mode conversion at the defects.

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A Time Reversal Imaging Method without Relying on Transfer Function for Impact and Damage Monitoring of Composite Structures

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.330.542 ◽

2013 ◽

Vol 330 ◽

pp. 542-548

Author(s):

Lei Qiu ◽

Shen Fang Yuan ◽

Tian Xiang Huang

Keyword(s):

Transfer Function ◽

Time Reversal ◽

Lamb Wave ◽

Composite Structures ◽

Structural Damage ◽

Composite Panel ◽

Synthesis Process ◽

Propagation Mechanism ◽

Imaging Method ◽

Phase Synthesis

Composite structures adopted in aerospace structures have attracted much interest to structural health monitoring (SHM) for localization of impact and damage positions due to their poor impact resistance properties. Propagation mechanism and frequency dispersion characteristics of Lamb wave signals on composite structures are more complicated than that on simple aluminum plates. Recently, much attention has been paid to the research of time reversal focusing method because this method shows a promising advantage to give a focusing image of the structural damage, improve the signal-to-noise ratio and compensate the dispersion of Lamb wave signals. In this paper, aiming at developing a practical method for on-line localization of impact and damage on aircraft composite structures which can take advantage of time reversal focusing and does not rely on the transfer function, a new phase synthesis based time reversal focusing method is proposed. Impact and damage images are given out directly through time reversal focusing based on phase synthesis process of the signals. A SHM demonstration system is built on a composite panel of an aircraft wing box with many bolt holes and stiffeners using the phase synthesis based time reversal focusing method. The demonstration results show that this method can estimate the positions of impact and damage efficiently with a low sensitivity of velocity errors.

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