Mode separation of Lamb waves based on dispersion compensation method

2012 ◽  
Vol 131 (4) ◽  
pp. 2714-2722 ◽  
Author(s):  
Kailiang Xu ◽  
Dean Ta ◽  
Petro Moilanen ◽  
Weiqi Wang
Keyword(s):  
Lamb Waves ◽  
Dispersion Compensation ◽  
Compensation Method ◽  
Mode Separation

scholarly journals Dispersion Compensation Method for Lamb Waves Based on Measured Wavenumber

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
J. Li ◽  
Y. Han
Keyword(s):  
Steel Plate ◽  
Lamb Waves ◽  
Dispersion Compensation ◽  
Distance Estimation ◽  
Phase Spectrum ◽  
Compensation Method ◽  
Phase Compensation ◽  
Material Parameters ◽  
Spectrum Measurement

In this study, a delta wavenumber dispersion compensation (∆K-DC) method was developed and applied, not only with the theoretical wavenumber but also with the measured wavenumber. Dispersion compensation can be achieved by the following steps: relative wavenumber measurement, traveling distance estimation, phase compensation, and wave correction. The feasibility of ∆K-DC with the theoretical wavenumber and measured wavenumber was validated with a high-dispersive A0 mode in a 2 mm steel plate experiment. The results showed that phase spectrum measurement was an effective method to construct the wavenumber curve, the propagation distances estimated by SAP2 were very accurate, and the dispersive signals can be compensated perfectly by applying the phase compensation and wave correction methods for each wavepacket. The present results highlight the application of ∆K-DC on dispersion compensation without any material parameters of a waveguide.

scholarly journals Mode Separation for Multimodal Ultrasonic Lamb Waves Using Dispersion Compensation and Independent Component Analysis of Forth-Order Cumulant

2019 ◽  
Vol 9 (3) ◽  
pp. 555 ◽  
Author(s):  
Xiao Chen ◽  
Dandan Ma
Keyword(s):  
Independent Component Analysis ◽  
Fourth Order ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Dispersion Compensation ◽  
Single Mode ◽  
Component Analysis ◽  
Independent Component ◽  
Mode Separation ◽  
Fourth Order Cumulant

Ultrasonic Lamb wave testing has been successfully applied in nondestructive testing. However, because of Lamb wave multimodal and dispersion characteristics, the received signals are often multimodal and overlapping, which makes them very complicated. This paper proposes a mode separation method by combining dispersion compensation with the independent component analysis of fourth-order cumulant. Taking two-mode overlapped signals as an example, the single-mode dispersion compensation is performed according to the measured distance difference between the two sets of signals. The two sets of signals are returned to the same distance. The fourth-order cumulant independent component analysis method is further used to process the Lamb wave signals of different superposition situations at the same distance. The corresponding mode signal contained in the two sets of signals is separated through the joint diagonalization of the whitened fourth-order cumulant matrix. The different modes are compensated and separated successively, achieving the multimodal signal separation. Experimental results in steel plates show that the presented method can accurately achieve mode separation for the multimodal overlapping Lamb waves. This is helpful for the signal processing of multimodal Lamb waves.

A Method of Dispersion Compensation Based on Warped Frequency Transform

2013 ◽  
Vol 718-720 ◽  
pp. 2062-2067 ◽  
Author(s):  
Shang Chen Fu ◽  
Zhen Jian Lv ◽  
Ding Ma ◽  
Li Hua Shi
Keyword(s):  
High Resolution ◽  
Velocity Dispersion ◽  
Lamb Waves ◽  
Group Velocity Dispersion ◽  
Dispersion Compensation ◽  
Imaging Method ◽  
Finite Element Software ◽  
Damage Imaging ◽  
Resolution Imaging ◽  
Multi Mode

The use of Lamb waves for structural health monitoring (SHM) has complicated by its multi-mode character and dispersion effect, which impacts the damage positioning and high-resolution imaging. The group velocity dispersion curves of Lamb waves can be employed to warp the frequency axis, and then to establish warped frequency transform (WFT) to process Lamb waves. In this paper, received signals are directly compensated with warped frequency transform to suppress dispersion, and a new imaging method is proposed based on warped frequency transform. The propagation of Lamb waves in damaged aluminum plate is simulated by finite element software ABAQUS, results show that warped frequency transform can effectively compensate dispersive wave-packets, and high-resolution damage imaging can be obtained by the proposed method.

Excitation series design and pulse compression synthesis for high-resolution Lamb wave inspection

2018 ◽  
Vol 18 (5-6) ◽  
pp. 1464-1478
Author(s):  
Jiadong Hua ◽  
Liang Zeng ◽  
Jing Lin ◽  
Liping Huang
Keyword(s):  
Lamb Wave ◽  
Pulse Compression ◽  
Lamb Waves ◽  
Dispersion Compensation ◽  
Synthesis Method ◽  
Side Lobe ◽  
Main Lobe ◽  
Window Functions ◽  
Windowing Technique ◽  
Lobe Width

Lamb wave pulse compression is a promising technique for ultrasonic nondestructive evaluation and structural health monitoring, in which the excitation waveform is designed to exhibit attractive auto-correlation characteristics including short main-lobe width and small side-lobe amplitude. However, narrowing main-lobe will increase side-lobe amplitude, and vice versa. Conventional time windowing technique is a balance between main-lobe width and side-lobe amplitude. An improvement over time windowing is proposed using pulse compression synthesis method. In this method, a series of excitation waveforms are used to actuate Lamb waves, each response is processed by pulse compression, and all the compression signals are summed together. The excitation series are constructed as linear chirps weighted with different combinations of rectangular and Hanning window functions. The selection of the combination coefficients is optimized to ensure best signal summation. The effectiveness of the proposed method is demonstrated by an experiment, and the robustness to inaccuracy in dispersion compensation is also evaluated. Application of the proposed method for damage detection is demonstrated by a further experiment.

A new chromatic dispersion compensation method based on genetic algorithm

2013 ◽  
Author(s):  
Chun-wu Liu ◽  
Jiang-yi Qin ◽  
Zhi-ping Huang ◽  
Yi-meng Zhang
Keyword(s):  
Genetic Algorithm ◽  
Dispersion Compensation ◽  
Chromatic Dispersion ◽  
Compensation Method
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