Attenuation characteristics of in-plane wave propagation in two-dimensional polycrystalline microstructure

This work investigates the propagation of multi-modal in-plane wave in two dimensional (2-D) polycrystalline microstructure using finite element (FE) simulation. The attenuation characteristics of in-plane wave are studied and compared to that of conventional bulk wave. A cubic polycrystalline material is considered with random grains orientation resulting in material in-homogeneity. Such structural in-homogeneity causes discontinuities at the grain boundaries resulting in wave scattering. The microstructure is generated using a controlled Voronoi tessellation with an appropriate log-normal distribution and imported into a commercial FE platform. In-plane wave is simulated using the developed FE model and validated by comparing group velocity and wave attenuation available in existing literature. Next, simulation of in-plane wave propagation is performed at different frequencies in the low frequency Rayleigh regime. In-plane wave produced circular wavefront in 2-D structure unlike a straight wavefront in non dispersive bulk wave propagation. As a result, in comparison to bulk wave, in-plane wave attenuation is found to be significantly higher. Additionally, due to circular wavefront, the frequency dependency of attenuation is also altered as observed in the detailed parametric study conducted. The study of in-plane wave propagation is an important step towards wave based characterization of microstructural flaws and defects.