Fracture Analysis of Sheet Aluminum Alloy AA2024-T3 Through a Complex-Loading Cross-Die Test

Abstract

Lightweight materials such as aluminum alloys are, nowadays, well recognized as one of the most popular choices in the aerospace industry owing to their fantastic strength-to-weight ratio. Their fabricability is, nevertheless, doubtful down to their low elongation, especially in the present day where geometrical complexity is hugely demanded. Truly understanding fracture behaviors of such sheet metal would benefit all involved parties. To achieve that challenging goal, proper fracture-analysis models and implementation methods are definitely crucial. This work proposes the recent Lou–Huh fracture criterion to describe the rupture behavior of sheet aluminum alloy AA2024-T3. To build such a damage mechanics model, a string of Nakajima stretching and notched tensile tests must be performed to acquire critical strain data, precisely measured using the 2D-DIC principle. The data are used to calibrate the model. A fracture locus (FL), defining an extensive AA2024-T3 fracture threshold, is then established out of the fine-tuned model. The FL is directly coupled into an ABAQUS/Explicit FE process simulation model via the Fortran-based subroutine VUMAT. This leading-edge implementation can supposedly emulate realistic damage evolution by monitoring and actively removing the elements whose degree of injury has reached a certain limit. At the end, the complete integrative FE model is empirically validated through an industrial X-shaped specimen, deformed under nonlinear strain paths. Fracture locations, shapes and development on the FE-simulated specimen are observed and contrasted with those on the experimental one. It is obviously shown that the results from both approaches agree remarkably well in all aspects. When compared with the famous fracture forming limit curve (FFLC), the Lou–Huh FL combined with the element-removal VUMAT implementation clearly outperforms. In summary, the proposed model and the implementation procedure are practically outstanding fracture evaluators of AA2024-T3, wonderfully predicting and vividly laying bare crack appearance and growth.