The decomposition FÂ =Â FeFp, material symmetry, and plastic irrotationality for solids that are isotropic-viscoplastic or amorphous

The symmetry-based framework allows us to show that for typical boundary-value problems involving isotropic, viscoplastic solids or amorphous solids, if a problem has a solution, then every time- and space-dependent rotation of the relaxed spaces also yields a solution, and it is possible to choose this rotation such that the transformed solution is inelastically spin-free: Wp ≡ 0. Thus, when discussing such materials, we may, without loss in generality, restrict attention to flow rules that are inelastically irrotational.