Research on Acoustic Emission Source Location Imaging in Aluminum Alloy Plate-type Structure

Abstract

Abstract The time reversal focusing and imaging technique is often used to locate the acoustic emission (AE) source on a plate-type structure. Because of the computational error caused by the dispersive modes of the raw AE signal, the AE source is sometimes located in the adjacent region of its real position and the pseudo-AE source will be focused in the location image of the AE source. This study is interested in how to effectively avoid the focusing of the pseudo-AE source. Thus, in this article, a Shannon wavelet transform with “Morlet” mother wavelet was used to isolate S0 modes from raw AE signals. The modulus value curves of the isolated S0 modes were treated by time reversal, time delay, and superposition at every grid point in the monitoring area, based on the time reversal focusing principle. The AE source was located at a certain grid point where the peak of the superposition curve is maximal. The monitoring area imaging was realized by defining every grid point’s pixel value with the peak of the superposition curves. The validating experiment was done in a 600 mm by 600 mm monitoring area which is on a 5052 aluminum alloy plate with dimensions of 1,200 mm by 1,200 mm by 3 mm. Comparing with the traditional square location method based on time difference of arrival (TDOA) calculation, the localization accuracy was improved and the maximal radial error is lower than 30 mm. Furthermore, the proposed localization method has a certain ability to overcome the effect of the plate size and local curvature.