On the fracture locus of AA7075-T651

The overall goal of this work-in-progress is to try to establish the fracture locus (i.e. the equivalent strain to fracture as a function of the stress triaxiality factor) for the high-strength AA7075-T651 aluminium alloy. Experiments on several specimen geometries enabled us to reach stress triaxialities in the range from sigma* = 0 for shear tests to sigma* = 1.4 for notched specimen tensile tests. For shear tests, failure occurred by strong strain localization. However, local stresses and strains can not be deduced directly from these tests. Consequently, Digital Image Correlation (DIC) was used to extract the local strain fields to failure. In parallel, numerical simulations of the tests were run using the non-linear finite element code LS-DYNA to extract the evolution of the local stress triaxiality during straining. Based on a combination of both experimental and numerical data, the failure locus of the material can be constructed.