Fatigue damage characterization at the early stage is difficult using conventional inspection methods. Low-frequency nonlinear guided waves have shown promising sensitivity to fatigue damage. However, the frequency pair selection for wave mixing in the quasi-synchronism range relies on numerous trials to achieve good performance of combinational harmonic generation and to reduce the overlapping between the combinational and second harmonics, since an infinite number of combinations can be selected for the frequency pair. In this study, a frequency pair selection method is proposed to simplify these tedious procedures and to provide a guide on the selection of frequency pair for quasi-synchronous wave mixing. The proposed method can be applied to different quasi-synchronous wave modes, and a S-index is introduced to characterize the performance of the combinational harmonic generation. In this study, the fundamental symmetric mode (S0) waves are used for collinear wave mixing. The frequency pairs with different S-indices are used for wave mixing, and to demonstrate the effectiveness and performance of the proposed method on predicting the combinational harmonic generation. The web of a tapered flange beam construction section is modelled in the numerical simulation, which shows similar results as a thick plate and combinational harmonic can be generated. The numerical results show good agreement with the S-index prediction, and the overlapping between combinational and second harmonics decreases with the increase of S-index. The results with lower values of S-index show significant coupling between fundamental harmonics, which results in significant overlapping between combinational and second harmonics. Fatigue damage characterization using quasi-synchronous wave mixing shows the potential to be applied on thick plates. The finding of this study provides a guide on the selection of frequency pair for quasi-synchronous wave mixing.
This paper presents a two-phase imaging methodology to characterise damage in composite laminates utilising Lamb
waves generated by integrated piezoceramic transducers. The proposed methodology uses the transducers to sequentially
scan the composite laminates before and after the presence of damage by transmitting and receiving Lamb wave pulses.
In phase one the damage localisation image is reconstructed by analysing the cross-correlation of the wavelet extracted
information from scatter signals with the excitation pulse for each transducer pair. A potential damage area is then
reconstructed by superimposing the image observed from each actuator and sensor signal path. In phase two Lamb wave
diffraction tomography is used to reconstruct an image quantifying size and shape of the damage based on the same set
of measurement data and identified damage location in phase one. The two-phase imaging approach together with the
modified diffraction tomography reconstruction algorithm enables a significant reduction of the required number of
transducers without the need to know the damage location in advance. Numerical and experimental results are presented
to demonstrate the efficiency, accuracy and sensitivity of the proposed methodology.
Conference Committee Involvement (4)
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2025
17 March 2025 | Vancouver, Canada
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2024
25 March 2024 | Long Beach, California, United States
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2023
13 March 2023 | Long Beach, California, United States
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems
7 March 2022 | Long Beach, California, United States
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