Application of Modal Acoustic Emission Technique for Recognition of Corrosion Severity on a Thin Plate

摘要

Corrosion poses a significant safety inspection problem in large industrial structures, where access for conventional inspection techniques is very limited. The theory of modal acoustic emission (MAE) was used to recognize the correlation between corrosion severity and the waveform of signals. The particle displacements of plates were investigated theoretically. The chemical reaction between hydrochloric acid and a steel plate was used to simulate the corrosion process. The amplitude difference of the extensional (S0) and the flexural wave mode (A0) was analyzed. It found that when the corrosion depth was slight, no matter its surface was large or small, the amplitude difference had almost no difference. When the corrosion depth reached to two thirds of the thin plate, the amplitude difference was almost half the amplitude of S0 in small surface corrosion pits, while the amplitude difference reached to 1.5 times of S0 in large surface pits. As a conclusion, the MAE technique is able to detect the plate-like structure corrosion in a long distance, and the amplitude of A0 is identified as the critical index for the corrosion severity.