On singular features of acoustic wave propagation in weakly dissipative anisotropic thermoviscoelasticity

The joint effect of viscosity and heat conductivity on the propagation of p lane bulk acoustic waves is studied in the low-loss approximation. Weak dis sipation has significant impact on wave proper ties in the neighborhood of those acoustic axes (directions of phase-speed degeneracy occurring in the absence of dissipation) which ale not parallel to symmetry axes and which t herefore split into pairs of degenerate complex wave vectors not lying in s ymmetry planes. The bifurcation nature of the wave branches in the neighbor ing domain and the drastically changing polarization features are analyzed. Wave solutions containing linear spatial dependence of the pre-exponential amplitude admitted along pairwise directions of wave-vector degeneracy are studied.