Obtaining complementary Lamb wave dispersion information by two signal processing methods on an all-optical non-contact configuration

We present the experimental realisation of an all-optical non-contact tool for the extraction of the Lamb wave propagation dispersion characteristics in thin plates. We describe and assess two different signal processing approaches used to transform the acoustic impulse response optically generated and measured into a frequency response from which to extract the Lamb wave dispersion curves. We demonstrate that the two different techniques enable complementary portions of the ultrasonic transmission path to be addressed.<p></p> Finally we demonstrate the sensitivity of this approach, in terms of material testing, to thermal changes in the ultrasonic transfer function and its capability to respond to damage to the sample structure