Ultrasonic damping in polycrystalline materials

Paper in proceeding, 2018

The grains in a polycrystalline material, typically metals, act as scatterers of ultrasonic

waves and thus give rise to attenuation of the waves. The grains have

anisotropic stiffness properties, typically orthotropic or cubic. A new approach

is proposed to calculate damping in a 2D setting starting from the scattering by

an anisotropic circle in an isotropic surrounding. This problem has recently been

solved, giving explicit, simple expressions for the elements of the transition (T) matrix

(which gives the relation between the the incoming and scattered fields) when

the circle is small compared to the ultrasonic wavelengths. The T matrix can be

used to calculate the total scattering cross section, which in turn can be used to estimate

the damping in the material. Explicit expressions for the damping coefficient

for longitudinal and transverse waves are obtained in this way.