Deformation waves in thermoelastic media and the concept of internal variables

Nonlinear thermoelastic continua with Fourier's type of heat conduction illustrate complex systems composed of internal and reaction-diffusion subsystems. An evolution equation is derived for the observable variable (deformation) when temperature effects are viewed as internal processes. This approach, which pertains to the so-called instantaneous wave analysis, shows that thermal losses accompanying the deformation wave correspond to the low-frequency approximation.