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

TL;DR

This paper introduces a variational phase-field model for fracture and fatigue in shape memory alloys, capturing complex behaviors like damage localization, transformation strains, and fatigue life prediction with promising experimental agreement.

Contribution

It presents a novel phase-field model coupling damage and phase transformation in SMAs, including a transformation strain limit and fatigue prediction capabilities.

Findings

Model predicts damage localization and delayed fracture.

Simulation results align with experimental fatigue data.

The model distinguishes safe and critical loading scenarios.

Abstract

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.