An Overlay j2 viscoelastic viscoplastic viscodamage model for stable shear localization problems

This work formulates simple isotropic local Overlay J2-viscoelastic-viscoplastic-viscodamage constitutive model (o-J2-VVV)which encompasses the merits of both the plastic and continuum damage formulations. The plastic component of the model account for inelastic permanent strains, while the damage component account for loss of stiffness. The plastic and damage softening moduli are regularized according to the material mode II fracture energy and the element size. The Orthogonal SubGrid Stabilization Method (OSGS) is used to ensure existance and uniquess of the solution for strain shear strain localization processes, attaining global and local stability of the corresponding discrete finite element formulation. Consistent residual viscosity is used to enhance robustness and convergence of the formulation. Numerical examples show that the formulation derived is versatily, fully stable and remarkably robust, The solutions obtained are completely mesh independent, unlike those obtained with the ill-posed standard approaches.