Local stress measurement on polycrystalline aluminum by an acoustic microscope

Abstract

The purposes of this work are to establish a high-resolution measurement of the leaky Rayleigh wave velocity with an acoustic microscope for polycrystalline metals and to measure local stresses with the acoustoelasticity of the Rayleigh wave. The V( z) signal acquisition system of conventional acoustic microscopes has been updated to enhance the velocity resolution. A new procedure of digital signal processings has been proposed for finding the accurate oscillation interval of the V( z) to measure precisely the leaky Rayleigh wave velocity. The relative velocity variation of the leaky Rayleigh wave has been reduced to 0.01% for 2017 aluminum alloy by using this signal acquisition and processing. The biaxial stress field around a small hole under tension has been measured by the proposed method and the results are compared with stresses estimated by finite element analysis.