A new ultrasonic guided wave signal processing method for UNDE of laminated composite material

A new ultrasonic guided wave signal processing method for ultrasonic nondestructive evaluation (UNDE) of laminated composite material has been developed in this paper. The key part of the method is the empirical mode decomposition (EMD) method and short-time Fourier transform (STFT) with which the characteristic parameter can be introduced to represent the size of flaw in laminated composite plate. EMD method is widely recognized to be efficient to nonlinear and non-stationary signals. STFT provides more accurate energy-frequency-time distribution for intrinsic mode functions of ultrasonic guided wave signal compared with Hilbert transform and instantaneous frequency algorithm of Hilbert-Huang Transform (HHT). The dispersive and anisotropic nature of laminated composite will be studied theoretically. In the experimental study, ten plates with different size of disbonded defect. In comparison with the results from the theory and experiment, it is confirmed that the new method is efficient for signal processing propagation of for UNDE of laminated composite plate.