An experimental and numerical study for the damage characterization of a Ti-6AL-4V titanium alloy

In this paper, modified Mohr Coulomb (MMC) and Lemaitre's damage model have been calibrated for a Ti-6Al-4V titanium alloy. A large uniaxial and multiaxial experimental program has been carried out on round, flat, smooth and notched, specimens. All experimental tests have been numerically reproduced adopting finite element models: most of the tests have been used to define the material parameters for the investigated damage models, exploiting an inverse method; some selected tests have been used to validate the calibrated damage criteria. Specifically, after the calibration stage, the capability of the material models to be transferred to a different and more critical scenario (high triaxiality and strain gradient) has been investigated by means of a three point bending test on a notched specimen. Moreover, in the paper, the advantages and drawbacks of Lemaitre's continuum damage mechanics (CDM) and MMC approaches have been addressed and discussed. Furthermore, a metallographic analysis using a scanning electron microscope (SEM) has been carried out and images of the specimen's fracture surface have been acquired in order to investigate the potential different fracture mechanisms, depending on the stress state.