65. On the Evaluation of Stress Triaxiality Fields via Integrated DIC: Influence of Mesh Discretization and Mesh Type

This paper presents a coupled experimental/numerical procedure to evaluate stress triaxiality fields. Such type of analysis is applied to a tensile test on a thin notched sample made of Ti 6–4 alloy. The experimental data consist of digital images and corresponding load levels, and a commercial finite element code (Abaqus) is used in an integrated approach to Digital Image Correlation (DIC).

With the proposed procedure, a given non-homogeneous sample can be analyzed independently without having to resort to other tests to calibrate the material parameters of a chosen constitutive law. For the studied material, different hardening postulates are evaluated up to a level of equivalent plastic strain about three times higher than those available in uniaxial tensile tests on smooth samples. Different finite element discretizations and model hypotheses (i.e. 2D plane stress and 3D simulations) are compared. The results show that, even for thin samples, 3D analyses are required for a correct evaluation of the stress triaxiality field. Furthermore, this FE-regularized image correlation is possible with a much finer local mesh than non-regularized global DIC.