Acoustic emission (AE)


The momentary contact between moving surfaces caused by either inadequate lubrication or the deterioration of surface condition leads to local energy loss in the form of multiple transients (for example due to friction and impacts). The elastic wave energy which these transients generate is broadband.

When acoustic emission (AE) is applied to operating machinery, it is used to directly detect the high-frequency part of these transient wave-packets originating from bearings and gearteeth. A benefit of high-frequency detection is the reduction in background noise, due to both normal running and adjacent machinery, enabling high sensitivity to fault conditions to be achieved.

Because AE signals provide dynamic real-time information from operating machinery, the technique can be applied to both rotating and non-rotating machinery. Various analysis methods can be used to extract useful information from the AE signals. At its simplest, the overall level of activity provides a useful parameter for trending purposes. On rotating machinery the frequency of modulation of the AE signal enables the identification of particular fault types. On non-rotating machinery, detail within the ‘AE signature’ can be related to the known sequence of actions and deviations from the normal signature detected. AE instrumentation is available for both periodic and continuous application.