Universal scaling of transverse wave attenuation in polycrystals

Abstract

A single mode approximation for the transverse attenuation coefficient in polycrystals is obtained from the far field approximation model (Rokhlin et al., 2015). The model is applicable in all frequency ranges to polycrystals with ellipsoidal grains of triclinic symmetry and is shown to be in favorable agreement with other second order models. In the frame of this model, the transverse wave attenuation coefficient depends on a single elastic scattering factor only (it solely encompasses dependence on the crystallite elastic moduli and the elastic covariance). Therefore in this approximation the attenuation coefficient can be scaled with this factor (normalized), obtaining the universal (master) curve. The admissibility of scaling is supported by the use of the second order model (the type of Stanke-Kino) for a large number of material systems with different grain anisotropies. Within the second order model, the behavior of the scaled transverse wave attenuation coefficient versus frequency is nearly independent of the material system and is a function of the grain geometrical characteristics only. The scaling of the transverse wave attenuation coefficient is tested on the measurements for Ti alloy samples performed in this work and a large set of experimental data obtained for different material systems available in the literature. The results confirm the scaled coefficient independence of the material and good agreement between the data and the universal attenuation curve.