Signal-based acoustic emission techniques in civil engineering

The acoustic emission (AE) technique can be a useful method for the investigation of local damage in materials. One of the advantages compared to other techniques is the recording of the damage process during the entire load history without any disturbance to the specimen. Differences between the traditional parameter-based and newer signal-based techniques are described along with some examples of measurements to study the steel-concrete interaction in reinforced-concrete cubes. Signal-based procedures, such as accurate 3D localization of damage sources, solutions for fault plane orientation, and moment tensor inversion, are described with respect to applications in civil engineering. The more quantitative analysis of the signals is based on a 3D localization of AE sources (hypocenters) and the recordings obtained from a sensor network. Using moment tensor inversion methods, the radiation pattern of acoustic emission sources and the seismic moment (as an equivalent to the emitted energy), as well as the type (Mode I, Mode II, and mixed modes) and orientation of the cracks, can be determined.