What is Acoustic Emission Monitoring?
Acoustic emission (AE) monitoring is a non-destructive testing method that detects the elastic waves a solid releases when it cracks or deforms.
How it works
A solid releases stored elastic energy quickly when its structure changes in an irreversible way. A crack that forms, or plastic deformation, are two examples. The energy travels through the solid as waves. Transducers on the surface detect these waves. A group of transducers can find the source, because the waves reach each transducer at a different time.
Emissions below 1 kHz and up to 100 MHz have been reported. Most of the energy is between 1 kHz and 1 MHz. Non-destructive testing typically uses 20 kHz to 1 MHz.
Where it is used
AE is used to monitor the health of structures such as bridges and pipelines. Long-term monitoring can find cracks in pressure vessels and pipelines. ASTM E1316 lists acoustic emission among the testing methods whose terms it defines.
Limits
Friction, cavitation and impact also produce AE. A reading is not a proof of damage until an analyst has separated these sources from cracking.
Airfield inspection
No source in this fact-check ties AE monitoring to airfield lighting, pavement or obstacle inspection, so this page makes no claim about it.
Frequently Asked Questions
- How is acoustic emission testing different from ultrasonic testing?
- Acoustic emission testing listens to waves that the material itself produces. It does not send waves into the material. Ultrasonic testing sends in its own waves and reads how they change.
- What is the Kaiser effect?
- The Kaiser effect is the behavior of a material that stays quiet under repeated loading until the load goes above the highest earlier load. It is named after Joseph Kaiser, who first studied it in the 1950s.
- Does every acoustic emission mean damage?
- No. Friction, cavitation and impact also produce acoustic emission, and none of them involves material failure. An analyst must separate these signals from the signals of cracking.
References
- wikipedia-acoustic-emission
- Acoustic emission Wikipedia
- wikipedia-kaiser-effect
- Kaiser effect (material science) Wikipedia
- astm-e1316
- ASTM E1316-23a, Standard Terminology for Nondestructive Examinations ASTM International
This is a reference entry. TarmacView provides drone inspection services and doesn't sell the equipment or materials described in this glossary.