On the Evaluation of Stress Triaxiality Fields in a Notched Titanium Alloy Sample Via Integrated Digital Image Correlation

Abstract

This paper presents a coupled experimental/numerical procedure to evaluate triaxiality fields. Such a 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 code (abaqus) is used in an integrated approach to digital image correlation (DIC). With the proposed procedure, samples with complex shapes can be analyzed independently without having to resort to other tests to calibrate the material parameters of a given constitutive law to evaluate triaxilities. The regularization involved in the integrated DIC (I-DIC) procedure allows the user to deal with experimental imperfections such as cracking of the paint and/or poor quality of the speckle pattern. For the studied material, different hardening postulates are tested up to a level of equivalent plastic strain about three times higher than those achievable in a tensile test on smooth samples. Different finite element (FE) discretizations and model hypotheses (i.e., 2D plane stress and 3D simulations) are compared.