by the material during failure or stress, and not on the material's effect on externally generated waves. Part failure can be documented during unattended monitoring. The monitoring of the level of AE activity during multiple load cycles forms the basis for many AE safety inspection methods, that allow the parts undergoing inspection to remain in service. The technique is used, for example, to study the formation of cracks during the welding process, as opposed to locating them after the weld has been formed with the more familiar ultrasonic testing technique. In a material under active stress, such as some components of an airplane during flight, transducers mounted in an area can detect the formation of a crack at the moment it begins propagating. A group of transducers can be used to record signals, then locate the precise area of their origin by measuring the time for the sound to reach different transducers. The technique is also valuable for detecting cracks forming in pressure vessels and pipelines transporting liquids under high pressures. Also, this technique is used for estimation of corrosion in reinforced concrete structures. In addition to non-destructive testing, acoustic emission monitoring has applications in process monitoring. Applications where acoustic emission monitoring has successfully been used include detecting anomalies in fluidized beds, and end points in batch granulation. Standards for the use of acoustic emission for non-destructive testing of pressure vessels have been developed by the ASME, ISO and the European Community. See also Ultrasonic homogenizer Ultrasonic testing References External links and further reading History of the Latin American Working Group on Acoustic Emission. Wolfgang Sachse, Kusuo Yamaguchi, James Roget, AEWG (Association) books.google.co.uk 100 page entries from search criteria : AE within this text () Nondestructive testing Acoustics Materials science