Double points of the slowness surface of the system of crystal acoustics for tetragonal crystals

Abstract

The aim of this paper is to study the location and the geometrical properties of the double points of the slowness surface associated to the system of linear crystal-elasticity in three space dimensions for tetragonal crystals. It will turn out that compared with the case of cubic crystals, the location of these double points is more involved. Moreover, for some specific choices of the “so-called” stiffiness constants, a new type of singularities namely “biplanar” ones, will appear.