Fatigue crack growth in anisotropic aluminium sheets -- phase-field modelling and experimental validation

TL;DR

This paper presents a phase-field model for simulating fatigue crack growth in anisotropic aluminium sheets, validated through experiments, capturing crack paths and growth rates influenced by manufacturing-induced anisotropy.

Contribution

It introduces a novel phase-field modeling approach incorporating anisotropic fracture toughness and fatigue weakening, specifically tailored for cold-rolled aluminium sheets.

Findings

Model accurately predicts crack path direction.

Model reproduces fatigue crack growth rate.

Validation confirms model's effectiveness for anisotropic materials.

Abstract

Fatigue crack growth is decisive for the design of thin-walled structures such as fuselage shells of air planes. The cold rolling process, used to produce the aluminium sheets this structure is made of, leads to anisotropic mechanical properties. In this contribution, we simulate the fatigue crack growth with a phase-field model due to its superior ability to model arbitrary crack paths. A fatigue variable based on the Local Strain Approach describes the progressive weakening of the crack resistance. Anisotropy regarding the fracture toughness is included through a structural tensor in the crack surface density. The model is parameterised for an aluminium AA2024-T351 sheet material. Validation with a set of experiments shows that the fitted model can reproduce key characteristics of a growing fatigue crack, including crack path direction and growth rate, considering the rolling direction.