Acoustic Emission Acoustic Emission (AE) are transient elastic waves during the rapid release of energy from localized sources within a material. AE waves range in frequency from a few kHz to several MHz. The source of these emissions in metals is closely associated with the dislocation movements accompanying plastic deformation and the initiation and extension of cracks in a structure under stress. Sources of AE include melting, phase transformation, thermal stresses, cool down cracking, friction mechanisms and stress build up. The AE sensor can be used to monitor processes such as: · Stamping · Deep Drawing · Industrial cutting tool Breakage · Fracture of metal or composite pressure vessels · Fracture of stressed structures/ bridges · Detecting loose parts in an electronic assembly · Detecting, locating and evaluating flaws in materials · Insect activity in wood · Steam valve leaks · Partial discharge in industrial transformers AE sensors can warn of faults when they are occuring, not just whether or not they exist like traditional nondestructive text methods, i.e. x-ray, dye penetrants, eddy current, ultrasonic transmission or microscopic inspection. Detectable AE signals are emitted before visual signs of fracture or cracking appear. 42 www.kistler.com