Acceleration waves in simple and linear viscoelastic micropolar materials

In this work the conditions of propagation of acceleration waves are studied in different types of micropolar media: (a) in simple media whose constitutive equations are given in functional form, (b) in linear viscoelastic media of which the constitutive equations are obtained in the limit of small deformations from a simple micropolar medium obeying the axiom of fading memory. In contrast to the first case, two kinds of acceleration waves can propagate independently in the second case.