Measurement of ultrasonic attenuation in material surface layer by spectroscopic technique with ultrasonic reflectivity measurement

The attenuation of surface acoustic waves is a useful parameter for estimating grain size, porosity and microstructure, which are closely related to electrical and mechanical properties of materials. In the present paper, a novel method for the determination of ultrasonic attenuations in the surface layer of materials using an ultrasonic spectroscopic technique is proposed. The method is based on absolute measurement of the reflection coefficient of the materials and analysis of its spectral behavior. The attenuation are determined by detecting the frequency of least reflection and by estimating a locus of zero points of the reflection coefficients in the complex plane. An experiment with annealed carbon steel was demonstrated. The reflection coefficient calculated with the attenuation estimated by the present method indicated a frequency dependence similar to the experimental result. This reveals that the estimated attenuations are good approximations of the actual acoustic response of materials.