About IIAET
The India Institute of Acoustic Emission Testing is a registered Society. The objects and purpose of this Society are constituted to promote the scientific development of Acoustic Emission Testing Facilities in India. It also provides a common platform for its registered members to share the information. Compared to other NDT methods like magnetic particle testing or dye penetrant testing, acoustic emission testing is relatively new.
It was first used in the early 1980s as a way for inspectors to test polymer matrix composites (PMCs). The sensors used to record acoustic emissions use a piezoelectric material. Piezoelectricity is the production of electrical charges by the introduction of mechanical stress. Imagine setting using a crane to set a slab of granite on to the top of a bus.
The heavy granite will push down onto the bus, generating stress and electrical charges. And these charges are a type of piezoelectricity.
Piezoelectricity was first discovered in 1880, by two brothers named Pierre Curie and Paul-Jacques Curie. But it was not used for much of anything until the early 1920s, when an inventor named Walter Cady experimented with using piezoelectricity for stabilizing electronic oscillators.
Around sixty years later, researchers began testing piezoelectricity for identifying defects in polymer matrix composites. Today, the sensors used for acoustic emission testing are called piezoelectric acoustic wave sensors, because they apply an oscillating electric field in order to generate a mechanical wave.
This wave then travels through a material and becomes an electric field, which can be measured by an inspector.
Although AE is a promising NDT method it is still in its infancy, and will require years of research and development before it is a completely reliable, stand-alone inspection technique.
One interesting new application for AE is using it to detect earthquakes before they actually happen, but this application is also just in the early stage of development.
Acoustic emission testing is an inspection method that uses the release of ultrasonic stress waves to identify defects in materials. These ultrasonic waves are not introduced from an external source, as they are in ultrasonic testing, but rather originate from within the material being inspected.
Acoustic Emission Testing is also called Acoustic Emission (AE), Acoustic Testing (AT, Acoustic NDT, or AE Testing.
Acoustic emissions happen when a material is under stress, either from holding a heavy load or from extremes of temperature.
These emissions typically correspond with some kind of defect or damage being done to the structure emitting them—and this damage is what inspectors are looking for when they do an AE test.
Sources of acoustic emission can include:
• Phase transformation
• Thermal stress
• Cool down cracking
• Melting
• Bond and/or fibre failure
