Paper detail

Variational phase-field modeling of fracture and fatigue in shape memory alloys

We propose a novel variational phase-field model for fracture and fatigue in pseudoelastic shape memory alloys (SMAs). The model, developed in a one-dimensional setting, builds upon the Auricchio-Petrini constitutive formulation for SMAs and couples damage evolution with phase transformation. We study analytically and numerically the homogeneous and localization responses of a bar under both monotonic and cyclic loading, and we investigate various macroscopic behaviors by tuning the constitutive parameters. A key feature of the model is the introduction of a transformation strain limit, beyond which the material is fully martensitic and behaves elastically. This leads to a distinctive behavior in which the region of localized damage widens, yielding a delay of fracture. The capability of the model to predict the fatigue performance is demonstrated by simulating the uniaxial response of Ni-Ti multi-wire samples under different loading conditions. The results show promising agreement with experimental fatigue life data, enabling the discrimination between safe and critical loading scenarios.