Simulation of acoustic emission signal attenuation of corrosion defects on tank bottom plates under pulsed high current excitation

Aiming at the problem of significant attenuation of electromagnetic acoustic emission signals in the detection of pore-etching defects on the bottom plate of storage tanks, this study reveals the mechanism of electromagnetic acoustic emission and its propagation and attenuation law by constructing a numerical model of electromagnetic-acoustic coupling. Based on the finite element method, a numerical model of Q235 steel plate with pore-etching defects is established, and the generation mechanism of electromagnetic acoustic emission in the defective region under the excitation of strong pulsed current is elucidated. The study shows that: the pulsed current generates Lorentz force perturbation at the edge of the defect, which excites the broadband acoustic emission signal; the acoustic wave propagation shows a significant dispersion effect, with the high-frequency component decaying rapidly in the near-field region (0-25mm), the middle- and low-frequency components forming the dominant modes in the transition region (25-50mm), and finally tending to decay stably in the far-field region (>50mm). The reliability of the model is experimentally verified, and a quantitative relationship between the excitation current and the attenuation coefficient is established. The results provide a theoretical basis for optimising the excitation parameters and sensor layout, which is of great engineering significance for improving the defect detection accuracy of the tank bottom plate.