Signal-Based AE Analysis

Signal-based AE techniques use the entire transient waveform resulting from an AE event. As such, more information is available allowing for improved interpretation of fracture processes in a material or structure. Two signal-based approaches are presented and discussed in this chapter: Waveform analysis and quantitative analysis. The former has received increasing attention due to the recent developments and wide availability of machine learning algorithms. The latter is a classic approach that has its origin in seismology. The main approach associated with quantitative analysis is moment tensor inversion (MTI). While MTI requires accurate 3D source localization from an extensive network of sensors, waveform analysis can theoretically be performed with a single sensor. A comparison between signal- and parameter-based AE analyses is presented first. Subsequently, the measurement process is explained and its main influences on the recorded signals are discussed. Finally, waveform analysis and quantitative analysis approaches are described in detail, along with application examples from the literature.