A specified problem is adopted here to study wave propagation properties in a solid of different states i.e.

elastic

elastoplatic and strain localization. When the strain localization occurs

or solution of governing equation is in bifurcation

the classical constitutive model can not be used to analyze further material failure. Gradient dependent constitutive model

contrarily

can improve the capability someway

but characteristic dimension employed in material sacrifices high frequencies. And the capability of viscosity dependent constitutive model relies on what viscosity compose

if density and modulus

it can improve; if density only

it cannot.