Abstract:
This paper presents a localizing gradient damage model with evolving micromorphic stressbased anisotropic nonlocal interactions. The objective is to model mesh independent fracture
behavior of quasi-brittle materials, and to avoid the issues associated with the existing gradient
enhanced damage models. In the proposed model, an evolving anisotropic nonlocal interaction
domain governs the spatial diffusive behavior, which helps to maintain a localized damage
bandwidth during the final stages of loading. The anisotropy in nonlocal interactions is captured
through an anisotropic gradient tensor, which defines the orientation of the diffusive interaction
domain based on the principal stresses at a given material point. In this paper, a smooth
micromorphic stress tensor is utilized for the determination of principal stress states, to enforce a
properly oriented interaction across the bandwidth of the damage process zone throughout the
loading process. The proposed approach also enables the usage of low order finite elements
without any oscillatory micromorphic or nonlocal equivalent strain response in the later stages of
deformation. The accuracy and performance of the proposed model are demonstrated
numerically in plane strain/stress for mode-I, mode-II and mixed-mode loading conditions.
