Ultrasonic testing signal image processing based on improved set empirical mode decomposition

In view of the fact that the ensemble empirical modal decomposition (EEMD) method can avoid the modal aliasing phenomenon of the EMD method, it is still lacking in noise removal and retention of effective feature signals, so an ultrasonic nondestructive testing signal processing method combining EEMD and wavelet packets is proposed. In this method, the original signal is first processed by EEMD to ensure that the modal aliasing phenomenon is eliminated. However, this will cause the loss of some characteristic signals, and the lost signals will be retrieved through wavelet packet processing to improve the signal-to-noise ratio. In the process of decomposition signal reconstruction, the correlation coefficient method is used for feature selection, and the effective defect signal with high correlation coefficient is selected for reconstruction, which can not only effectively suppress modal aliasing, but also retain more feature signals. Through the experimental verification of the actual signal, the proposed improved method obtains a better signal-to-noise ratio, a lower root mean square error and a higher correlation coefficient, which is more suitable for processing ultrasonic nondestructive testing signals.