Characterisation and Optimisation of a Failure-Model for High Strength Aluminium Alloys

In the present work an effective parameter identification for the evaluation of a failure model for FE-simulations has been carried out. This failure model is suitable to calculate different fracture elongation values among occurring triaxiality of a high-strength aluminium sheet metal alloy (AA7075). Various specimen geometries have been selected to achieve different loading states (triaxiality). For biaxial strains a forming limit curve (FLC) is converted by using mathematical formulations. To measure the equivalent local strains in the event of fracture an optical measurement system has been installed and adapted to a tensile testing machine. The failure curve and the material model which includes the extrapolated flow curve are implemented into the FE-simulation model. In order to improve the accuracy of the failure-curve a parameter optimization has been carried out. It shows that by using the optimised failure curve a high correlation between experimental and calculated force-displacement curves for any given specimen geometry can be achieved.