Acoustic emission (AE)

What is NDT? 

Acoustic emission is a technique that is being used increasingly in the field of structural integrity assessment using fracture mechanics.

The dynamic behaviour of defects is extremely important as a small defect that is growing may well be more significant than a larger stable defect. Acoustic emission is the method used to investigate the behaviour of defects under stress. The test structure is subjected to a stress (usually slightly greater than the normal maximum load) by mechanical, pressure or thermal means. Under these conditions crack growth, local yielding and corrosion product fracture may occur resulting in a sudden release of energy, part of which will be converted to elastic waves. These elastic waves are readily detected by piezoelectric transducers which, by using methods of triangulation, can give positional information about the emitting defect. The amplitude of the received signals can also be used to give an indication of the rate of growth of the defect.

Acoustic emission is a very sensitive test method and one transducer can adequately monitor a large area or structure. It is vital that there is a degree of confidence (resulting from experience) in the method as the test is dynamic and cannot be verified by repetition.