Our study deals mainly with the stainless-steel characterization. A first approach demonstrates the high sensitivity of this method concerning the roughness of the surface. In this case, the Rayleigh velocity versus the frequency is shown to be constant on a polished surface and decreases on machined surface (R_a between 0.2 µ m and 2 µ m). The effects of microstructure are then analyzed. First, the texture is studied and the velocity variation due to rolling (reduction rate of 50%) is measured. This method enables also to detect grain size variations in the 10µm-100µm range. At last, we show a 0.4% velocity variation due to machining induced damage.

An impulse Modeling of the generation and the propagation phenomena is also performed for several materials. The different reflected waves and the attenuation are taken into account in the computations in order to describe accurately the wave-front shape and the amplitude of the measured acoustic signals.