Research on f-k Domain Modal Separation Method for Guided Wave Array Non-destructive Testing

Ultrasonic guided waves offer several advantages, including fast propagation speed, low attenuation, and sensitivity to small damages. These waves are extensively employed in non-destructive testing of plate structures due to the varying sensitivity of different guided wave modes to damage, which enhances the accuracy of damage imaging. However, the presence of multiple modes of guided waves poses challenges such as aliasing of time-domain signal wave packets and difficulty in identifying damage information. To address these challenges, this study proposes the utilization of the f-k domain filtering method. By considering the corresponding relationship between the propagation direction of the guided wave and the frequency wavenumber matrix, combined with the characteristics of the differences in wavenumbers of different modes at the same frequency, a three-dimensional (3D) window function is constructed using numerical simulation and experimental methods. This window function facilitates the extraction of different modes and their corresponding damage reflection signals. Simulation and experimental results demonstrate the suitability of the modal separation method for extracting different modal damage reflection waves in the guided wave damage detection of aluminium plates. Furthermore, when the material parameters of a composite plate are unknown, the imaging data extraction method can be employed to extract the single-mode reference wavenumber for window function construction, enabling single-mode extraction.