Impact localization in an aircraft fuselage using laser based time reversal

Abstract

ABSTRACT This study presents a new impact localization technique that can pinpoint the location of an impact event within a complex aircraft fuselage using a time reversal concept and a scanning laser Doppler vibrometer (SLDV). First, an impulse response function (IRF) between an impact location and a sensing piezoelectric transducer is approximated by exciting the sensing piezoelectric transducer instead and measuring the response at the impact location using SLDV. Then, training IRFs are assembled by repeating this process for various potential impact locations and sensing piezoelectric transducers. Once an actual impact event occurs, the impact response is recorded and compared with the training IRFs. The correlations between the impact response and the IRFs in the training data are computed using a unique concept of time reversal. Finally, the training IRF, which gives the maximum correlation, is chosen from the training data set, and the impact location is identified. The proposed impact technique has the following advantages over the existing techniques: (1) it can be applied to isotropic/anisotropic plate structures with additional complex features such as stringers, stiffeners, spars and rivet connections; (2) only simple correlation calculation based on unique time reversal is required, making it attractive for real-time auto mated monitoring; (3) temperature variation barely affects the localization performance; and, (4) training is conducted using non-contact SLDV and the existing piezoelectric transducers which may already be installed for other structural health monitoring purposes. Impact events on an actual aluminum fuselage specimen are successfully identified using the proposed technique. Keywords: Impact localization, Time reversal, Laser Doppler vibrometer, Laser ultrasonics