New methods for onset detection of acoustic emission signals

Acoustic Emission (AE) monitoring can be used to detect the presence of damage as well as determine its location in Structural Health Monitoring (SHM) applications. The onset time of AE signals detected at different sensors in an array is used to determine their relative time difference of arrival which is essential in performing localisation of the signals’ originating source.Typically, this is done using a fixed threshold which is particularly prone to errors when not set to optimal values. This paper presents three new methods for determining the onset of AE signals without the need for a predetermined threshold. The performance of the techniques in terms of location accuracy is evaluated using AE signals generated during fatigue crack growth and compared to the established fixed threshold method. It was found that the mean absolute error in performing 1D location using the new methods was between 11.6 to 14.3 mm compared to a range of 19.3 to 37.2 mm for the conventional Fixed Threshold method at different threshold levels.