Acoustic Emission

Acoustic Emission (AE) is an NDE technique that measures the elastic energy released in the form of acoustic waves in materials that undergo irreversible structure changes (e.g., plastic deformation, cracking, rupture). The emitted acoustic waves are captured by sensors attached to the material’s surface. The technique considers the wave arrival time and the wave propagation speed to accurately locate in space and in time the wave source and the waveform shape to characterize the origin of nature (damage mode, crack orientation, etc.). AE monitoring systems have the ability to effectively inspect large and complex structures, are cost-effective and perform in the long-term. For these reasons, AE is the most commonly implemented NDE method in civil engineering and especially in concrete structures inspection. For several decades, AE is employed in numerous studies to fully assess and characterize cracks nucleation and propagation, damage mode and source on concrete. As concrete design and technology evolves, AE application is challenged. A case study application of AE highlights the recently developed smart autonomously healed concrete structures, the “concrete of the future.” It is shown that AE aims to develop a sensing tool; a sensor array is sufficient to detect, locate (and trigger if needed) the healing activation processes, quantify damage before and after repair. An overview of studies performed in the recent years shows the performance of AE on healing systems carrying agent that is encapsulated or embedded into advanced vascular networks.