Determination of Fracture Loci for Anisotropic AA6063-T6 Extrusions

摘要

As alloy development increases in complexity so do the fracture criteria that describe these materials. For example, aluminum extrusions are processed such that the crystallographic texture and grain structure introduce anisotropy in the constitutive behavior of the material. Furthermore, the stress state has a significant impact on the failure strain. In this work, strain mapping based on the digital image correlation method is used to obtain an experimental failure criterion for AA6063 extrusions in the T6 condition. An experimental program is developed to determine the fracture strain in sample geometries which cover a wide range of stress states. In order to account for the anisotropic nature of the extrusions, samples are tested in the extrusion, 45 and transverse directions for each sample geometry. The fracture strains are extracted from the experiments and the finite element method is used to calculate the triaxiality for each testing condition. Fracture loci are developed for each direction based on a Modified Mohr-Coulomb expression. The results reveal the anisotropic nature of these aluminum extrusions and suggest that the material testing direction must be considered to accurately predict fracture.