Calibration of a constitutive material model for Al 6061-T6 aluminium alloy

The definition of a complex operative scenario, that introduces large strains and failure, is a present challenge in the design of critical me-chanical components. Although full scale testing is, at present, fun-damental for a reliable approach to structural integrity evaluation, an economical and alternative method as numerical simulation is now an increasingly chosen, especially due to the develop of computing performances. In particular, the numerical assessment of the ductile fracture in metallic components represents an innovative and chal-lenging field in the structural integrity scenario. Aerospace, automo-tive and manufacturing industries have recently boosted their inter-est in this kind of simulations with the aim, little by little, to make these approaches reliable also for the certifications. However, in or-der to obtain reliable and realistic results, a complete calibration both of true stress-strain curve and failure is required. Starting from the need to characterize the material for further impact simulations, the work described in this study contains a complete characterization of the mechanical properties of Al 6061-T6 aluminium alloy for how concern material hardening and fracture locus. The calibration has been carried on through a series of experimental tests on simple specimens, with similar geometry, but subjected to different stress triaxiality, thanks to the use of a multiaxial hydraulic test machine. All the experimental tests have been numerically simulated and, based on the results of these analyses, a complete material constitu-tive model has been calibrated. Finite Element models are in fact ex-tensively used during the calibration process in order to reproduce numerically (virtually) the quasi-static tests. In particular the work presented in this paper is focused on the calibration of a ductile fail-ure criterion using the Bao-Wierzbicki [1] framework: this approach represents the state of the art about the criteria based on the stress triaxiality and it is indirectly already implemented in most common finite element codes.