Surface Characterization of Material Using Rayleigh Velocity Measurement in the Broad-Band Mode

The surface damage of materials can be characterized by measuring the variation of the Rayleigh wave velocity. There is also a need to study the effect of the anisotropy and the gradient of the damage versus the depth. The acoustic microscopy using broad-band pulses is one of the methods which can produce interesting results in a simple and fast way. In this case, the Rayleigh velocity can be also obtained through a time of flight measurement. In order to have a sufficient separation between the different components of the reflected echoes, it is necessary to properly select the geometrical and acoustical parameters, and that requires a sufficient comprehension of the phenomena. One of the challenge of this technique is to be able to perform time measurements with the necessary accuracy. We will show also that it is possible to extract conventional V(z) curves for a given frequency