Investigating the Slowness Characteristics in Acoustic Emission Tomography

Images of the inside of any structure can be achieved non-invasively using tomographic acquisition and processing methods. Acoustic emission tomography (AET) is a method of non-destructive testing technique that uses acoustic waves to visualize the image and diagnose the anomalies inside the structure. One of the key parameters in AET is the slowness (reciprocal of the velocity) phenomenon, where the propagation speed of AE wave varies in some areas of the structure. This can lead to significant information from the imaging results and limit the applications of the structure in certain cases. In this paper, we present a comprehensive study of Acoustic Emission (AE) testing, the time of arrival (TOA) of AE signal to each sensor, and calculate the slowness inside the material for reconstructing tomographic images. We analyze the slowness mechanisms and visualize the slowness in a two-dimensional plot. Standard Hsu-Nielsen (H-N) method has been used as an AE source. TOA is the basic function for finding slowness. The principle of iterative algorithms is used to find a solution for slowness in a specific cell by successive estimation.