“…Equation 46 accounts for the linear temperature dependence of elastic wave velocities in isotropic materials. Based on the assumption of finite static strain for temperature changes and small‐amplitude acoustic waves, the fourth‐order Taylor thermoelastic constants are introduced to develop nonlinear thermoelastic models to account for the second‐order (Telichko & Sorokin,
2015) and third‐order (Yang, Fu, Fu, et al.,
2019) nonlinear temperature dependence of elastic wave velocities for cubic crystals and isotropic materials, respectively. For example, the third‐order nonlinear thermoelastic model for isotropic materials is defined as
where the synthetical third‐ and fourth‐order Taylor thermoelastic constants (
,
) and (
,
,
,
) for elastic P‐ and S ‐waves, respectively, are written as
…”