TABLE OF CONTENTS The word acoustic is derived from the Greek word akoustikos, which has to do with hearing. For centuries, the precursor to structural collapse has been sounds that are emitted prior to the failure of a supporting member. A tree branch emits a cracking sound before it actually breaks and stepping onto thin ice produces sounds that warn of impending collapse. Acoustic emission (AE) in this form is to the ears what visual inspection is to the eyes. The analysis of these emissions has become a science in itself.
Acoustic emission testing (AET) has become a recognized nondestructive test (NDT) method commonly used to detect and locate faults in mechanically loaded structures and components. AE can provide comprehensive information on the origination of a discontinuity (flaw) in a stressed component and also provides information pertaining to the development of this flaw as the component is subjected to continuous or repetitive stress.
Discontinuities in components release energy as the component is subjected to mechanical loading or stress. This energy travels in the form of high-frequency stress waves. These waves or oscillations are received with the use of sensors (transducers) that in turn convert the energy into a voltage. This voltage is electronically amplified and with the use of timing circuits is further processed as AE signal data. Analysis of the collected data comprises the characterization of the received voltage (signals) according to their source location, voltage intensity and frequency content.
The major difference between the AE method...
