Ultrasonic wave propagation predictions for polycrystalline materials using three-dimensional synthetic microstructures: Attenuation.

Ultrasonic attenuation plays a crucial role in inspection for heterogeneous materials such that theoretical models are critical for improved measurements. In this article, several assumptions often used in these models are examined with respect to their influence on attenuation. Here, dream.3d software is used to generate 10 ensembles with different volumes, each containing 50 realizations of equiaxed grains with cubic single-crystal symmetry, from which attenuations are calculated. Comparisons are then made with attenuation values derived from classical theories. These theories often decouple the spatial and tensorial components of the microstructure, assume statistical isotropy, and use a spatial correlation function that has a specific exponential form. The validity of these assumptions is examined by calculation of the spatial statistics to obtain the attenuations in their most general form. The results of Voigt-averaged results for nickel at 15 MHz show that the longitudinal and transverse attenuations are about one-third and one-fourth of those obtained from the theory, respectively. Such a difference is attributed to the relevant spatial correlation functions. The results also show a slight anisotropy in the attenuation. Finally, for microstructures with narrow grain size distributions and weak texture, the decoupling assumption is shown to be valid.