Acoustic emission for physical examination of metals

Acoustic -emission techniques are beginning to be frequently used as a means of detecting and locating deformation and fracture processes in both metallic and non-metallic engineering structures. This has happened despite a relatively poor understanding of the basic physical processes involved in the generation, propagation, and detection of acoustic -emission signals, and of the influence in metals of factors such as composition and microstructure, upon the acoustic emission from different types of deformation and fracture processes. The measurement of acoustic emission, potentially, could yield much information about dynamic aspects of these processes. However, it is shown that the limitations of existing acoustic-emission recording instrumentation have enabled only qualitative information to be obtained to date. Even this data, however, has demonstrated that metallurgical variables greatly affect the acousticemission response of metals, and simple models to account for this are discussed.