Ultrasonic Discrimination of Samples With Differently-Distributed Grain Sizes and Equal Average Grain Size

Abstract

AbstractMaterials can have distributions of grain sizes. These distributions can have effects on the material's mechanical properties that are more complicated than an average grain-size dependence. The omission of distribution effects on properties is understandable in view of the great amount of labor required in the experimental measurement of grain volume distribution, together with the predominantly two-dimensional nature of micrography-based grain-size estimation. Ultrasonic techniques have been used to nondestructively measure the grain size of materials on a scale of microns. We suggest using ultrasonic attenuation as an alternative to micrography for three reasons. One advantage is that the ultrasonic dependence on size is a true, three-dimensional dependence. Secondly, through careful selection of wavelength, various grain-size distribution parameters can be extracted. The third justification is that ultrasonic techniques are quick and nondestructive. Previous theoretical development will be reviewed, and the experimental verification will be presented. Through numerical modeling we show the advantages of using ultrasonic techniques that are sensitive to grain-size distribution parameters. We demonstrate that samples with equal average grain size but different grain-size distributions have significantly different attenuation wavelength dependencies.