Analysis of ductile damage with sigmoidal hardening

Hexagonal Closed-Packed (HCP) materials are widely used in engineering applications – from transportation to biomedical devices. Magnesium alloys are a class of HCP materials that are promising candidates because they are cheaper, more light-weight, and biodegradable, compared to titanium, and aluminum. However, their damage mechanisms are poorly understood, because of its multi-stage stress-strain response, often referred to as sigmoidal (or S-shaped) hardening. This makes it difficult to obtain robust engineering projections regarding their durability and damage tolerance. The goal of this research is to investigate the coupled effects of the material characteristics and specimen geometry on the macroscale damage behavior of magnesium alloys. Two plasticity models considered are Power-law hardening and Sigmoidal hardening. Also, damage modeled using is the GTN model. Four specimen geometries modeled using finite elements in ABAQUS/STANDARD (Rights Reserved) to account for increasing levels of stress triaxiality (T).