Acoustic emission (AE) is the release 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 is occurring 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 waves generated by sources of AE are of practical interest in structural health monitoring , quality control, system feedback, process monitoring and other fields. In SHM applications, AE is typically used to detect, locate and characterise damage.
The Low Level Measurements Group currently is working on prototyping AE features that may be used to characterise the physical underlay of a micro – macrofracture process. This is undergone using the Physical Acoustics Corp. 8 channel AE recording system.