<title>A fundamental study of an inspection method for thin-walled structures using lamb waves induced by chirp signals</title>

Abstract

In this study, a new NDT-method is proposed for inspecting delaminations in the composite plates (1mm-thickness CFRP layer with 1mm-thickness aluminum liner) Lamb waves (plate waves) generated by chirp signals (250-1000 kHz, 4Vp-p) were used for the inspection. We first studied characteristics of excited signals from the pulser when the chirp signal is used as an input signals. The amplitude of the excited signal from the pulser is changed with frequency due to the resonant characteristics of the transducer, although, wide range of the frequency components can be generated by using chirp signals. Two transducers were mounted on the composite plate, and inspection was conducted by using lamb waves. The amplitude, velocity and scattering of lamb waves on damaged and sound zone were compared. When the transducer is on the delamination area, low frequency components of the lamb wave drastically attenuated and could easily detect the delaminations. While, when the delamination is between two transducers, characteristics of lamb waves are similar to those on the sound area and difficult to separate each other with reasonable accuracy. Further modification of experimental method is needed to accomplish new inspection method.