Acoustic emission

Acoustic emission (AE) is the phenomenon of radiation of acoustic (elastic) waves in solids that occurs when a material undergoes irreversible changes in its internal structure, for example as a result of crack formation or plastic deformation due to aging, temperature gradients, or external mechanical forces.

In particular, AE occurs during the processes of mechanical loading of materials and structures accompanied by structural changes that generate local sources of elastic waves. This results in small surface displacements of a material produced by elastic or stress waves generated when the accumulated elastic energy in a material or on its surface is released rapidly.

The mechanism of emission of the primary elastic pulse AE (act or event AE) may have a different physical nature. The figure shows the mechanism of the AE act (event) during the nucleation of a microcrack due to the breakthrough of the dislocations pile-up (dislocation is a linear defect in the crystal lattice of a material) across the boundary in metals with a body-centered cubic (bcc) lattice under mechanical loading, as well as time diagrams of the stream of AE acts (events) (1) and the stream of recorded AE signals (2).