Microstructural Characterization of Materials by a Rayleigh Wave Analysis

It is well known that material characteristics properties such as anisotropy, grain size, damage, roughness, can affect the Rayleigh wave propagating on a sample surface. The acoustic microscopy using broad-band pulses is one of the methods which can generate Rayleigh waves in a simple way. The acoustic energy generated by a transducer in the coupling medium reaches the sample surface and is partially reflected into an axial echo and converted into a Rayleigh wave at the Rayleigh critical angle θR. With an impulse excitation, these two echoes are resolved in time. In this case, the Rayleigh velocity can be also obtained through a time of flight measurement. One of the challenge of this technique is to be able to perform time measurements with the necessary accuracy in order to detect shifts in the material properties