Mode Recognition of Lamb Wave Detecting Signals in Metal Plate Using the Hilbert-Huang Transform Method

Abstract

The dispersion and multiple modes characteristics which exist in the propagation of Lamb waves (LW) in metal plates make it extremely hard to analyze and recognize the detection echo signals of defects. As a newly developed time-frequency analysis method in recent years, Hilbert-Huang transform (HHT) is one of the powerful tools to analyze non-stationary signals. The experimental LW detecting system for single aluminum plate is setup in this work, and the LW detecting signals are analyzed by HHT. The overlapped LW detecting signals of different modes are recognized by the means of extracting flight time of intrinsic mode functions (IMFs) after Hilbert transform (HT). The experiment results, agreeing well with the theoretical analysis, indicate that the HHT method can clearly recognize overlapped LW detecting signals of different modes in metal plates, but could hardly recognize that of the same mode. HHT can be an effective method to recognize LW detecting signals of different modes in metal plates.

Lamb wave based damage detection in metallic plates using multi-headed 1-dimensional convolutional neural network

“…The multi-headed CNN configuration offers enhanced classification abilities by extracting higher order features from the 1D data [41]. Then the 1D-CNN model is trained on a portion of database using Adam optimization algorithm, which is appropriate for nonstationary and non-linear data such as Lamb wave signals [8,28,29]. At a later stage, the trained 1D-CNN architecture is tested to recognize damage features within unseen experimental Lamb wave responses acquired from the Al-5052 plate with a real notch-like cavity.…”

Mode identification of broadband Lamb wave signal with squeezed wavelet transform

“…Zhang applied the method to analyse both directly arriving and boundary-reflected Lamb wave modes of opposite types (S0 and A0) [16]. The EMD and HT method was also used to extract arrival times of Lamb waves for imaging applications [17].…”