Material Characterization by Acoustic Line-focus Beam

Abstract

The line-focus-beam acoustic microscope system has been successfully developed for the material characterization especially in the velocity measurements of leaky waves on the boundary of water/ samples through the V(z) curve measurements.^1–4 V(z) curves also contain another information, i.e., attenuation of the relevant leaky waves. The material characterization would be completed by measuring two physical quantities, i.e., attenuation in addition to velocity. The wave attenuation is mainly caused by three important effects: 1) the water loading on samples, 2) the acoustic absorption, and 3) the structural scattering due to surface roughness, grains, pores and boundaries. The effects of the two quantities of leaky waves on V(z) curves have been already clarified by theoretical analysis based on field theory and numerical calculations for the acoustic line-focus beam.⁵ It has been also shown that the attenuation could be estimated from the shape of V(z) curves by comparing experiments and theoretical calculations. However, no experimental procedure has been established so far for direct determination of the two quantities of both velocity and attenuation from V(z) curves.