Effect of material thermo-viscoplastic modeling on the prediction of forming limit curves of aluminium alloy 5086

International audienceA solution to improve the formability of aluminium alloy sheets can consist in investigating warm forming processes. The optimization of forming process parameters needs a precise evaluation of material properties and sheet metal formability for actual operating environment. Based on the analytical M-K theory, a Finite Element (FE) M-K model was proposed to predict Forming Limit Curves (FLCs) at different temperatures and strain rates. The influences of initial imperfection value (f 0) and material thermos-viscoplastic model on the FLCs are discussed in this work. The flow stresses of AA5086 were characterized by uniaxial tensile tests at different temperatures (20, 150 and 200°C) and equivalent strain rates (0.0125, 0.125 and 1.25 s −1). Three types of hardening models (power law model, saturation model and mixed model) were proposed and adapted to correlate the experimental flow stresses. The three hardening models were implemented into the FE M-K model in order to predict FLCs for different forming conditions. The predicted limit strains are very sensitive to the thermo-viscoplastic modeling of AA5086 and to the calibration of the initial geometrical imperfection which controls the onset of necking