An electromagnetic ultrasonic synthetic aperture focusing imaging method based on wave packet decomposition optimisation to eliminate artefacts

Electromagnetic acoustic transducer testing technology (EMAT) has the advantages of non-contact, no coupling agent, and easy excitation of different waveforms. It has advantages in applications such as high-temperature online detection. Synthetic aperture focusing technique (SAFT) can use a single ultrasonic array element to achieve high-resolution imaging, providing a new idea for electromagnetic ultrasonic imaging detection. The efficiency of electromagnetic acoustic transducer is low and the signal components are complex. How to eliminate imaging artefacts is a problem that needs to be studied. This paper analyzes the sound field distribution of common types of electromagnetic ultrasound transducers and the causes of noise wave packet generation, and proposes a wave packet decomposition technology based on the zero-mean normalised cross-correlation criterion. Decompose the defect echo signal, optimise the waveform, and increase the number of signals through interpolation algorithms. Experiments show that the proposed method can effectively eliminate artefacts and improve the quality of electromagnetic ultrasonic synthetic aperture focusing imaging.