Propagation of Ultrasound in Crystals

A crystal is an anisotropic medium, so that its equation of motion in the linear approximation must be expressed in the general form (I.11). The stress σ_jk can be expressed in the same approximation in terms of the strain with the help of relation (I.13c) : XI.1 σik=ciklj∊lj, https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429332227/64e5e3df-c95f-4a2a-a02e-98ef4c2d440f/content/equ11_1.tif"/>