Acoustic Emission

Acoustic Emission Testing (AET) is a nondestructive testing method that is based on the generation of waves produced by a sudden redistribution of stress in a material. When a piece of equipment is subjected to an external stimulus, such as a change in pressure, load, or temperature, this triggers the release of energy in the form of stress waves, which propagate to the surface and are recorded by sensors. Acoustic emissions can come from natural sources, such as earthquakes or rockbursts, or from the equipment itself such as melting, twinning, and phase transformations in metals. Detection and analysis of AE signals can provide information on the origin and importance of discontinuities in a material.

Main Advantages of Acoustic Emission Testing:

AET is different than other NDT techniques in two major ways:

1. Instead of supplying energy to the object under examination, AET listens for the energy released by the object naturally. AE tests can be, and often are, performed on structures while they are in operation, since this provides adequate loading for propagating defects and triggering acoustic emissions.
2. AET deals with dynamic processes in a material. This is particularly useful because only active features are highlighted during the examination. Thus, it is possible to discern between developing and stagnant defects. However, one should be aware that it is possible for flaws to go undetected if the loading isn’t high enough to cause an acoustic event that can be detected by the system.