Detection of the point of impact on a stiffened plate by the acoustic emission technique

The applicability of guided waves to predict the point of impact in a stiffened plate is investigated. The conventional triangulation technique cannot predict the point of impact in a stiffened plate because the triangulation technique assumes that the wave speed is independent of the direction of propagation, which is not true for stiffened plates. An alternative method based on the optimization scheme was proposed by Kundu et al (2007 J. Acoust. Soc. Am. 122 2057-66) to locate the point of impact in plates by analyzing the time of arrival of the ultrasonic signals received by passive sensors attached to the plate. After successful extension of this technique to predict the point of impact in anisotropic but homogeneous composite plates (Kundu et al 2008 Ultrasonics 48 193-201) it is investigated in this paper whether this technique works well for predicting the point of impact in an inhomogeneous plate where the stiffeners make the structure inhomogeneous. Experiments are carried out by dropping ping pong and metal balls on the plate to simulate the impact phenomenon and recording acoustic signals by passive transducers adhesively bonded to the plate at three different locations. The impact points are predicted and compared with the actual locations of impact.