Delta-T Acoustic Source Localization for Plate with Holes

Abstract

Acoustic Emission is a powerful tool for real-time condition monitoring of structures, based on the principle of propagating elastic waves resulting from sudden stress variations. It is a passive Non-Destructive Testing technique that is capable of detecting and locating crack growth and impact over larger areas unlike traditional methods. Time-of-arrival source location technique, which triangulates the signal arrival time of the propagating waves, assumes straight wave propagation path and fails when applied to complex geometrical profiles. Delta-T method, an experimental gridbased methodology, has reportedly been capable of overcoming the limitation with successful source location on composites and metal plates with circular holes. Since square holes have edges that form perpendicular barriers to the direction of incident waves, they result in longer wave propagation paths and have a higher propensity of blinding sensors from the propagating waves. This study extends the evaluation of Delta-T method to plate with square holes. Maps of difference in arrival times between sensor pairs are obtained for three square stainless steel plates with no hole, a circular hole and a square hole respectively. The validation points are then located by overlapping contour lines obtained from the respective Delta T maps. Experimental results indicate that Delta-T method provides an improvement in accuracy of 11 times over TOA for the source location estimation on plate with square hole and gives 5 times more precise estimation across all 3 metal plates with different geometries.