Analysis of springback of aluminum and high-strength steels through a new large strain anisotropic elastoplastic formulation based on elastic corrector rates

Aluminum and high-strength steels (HSS) are increasingly being employed in the sheet metal forming in the automotive, aeronautical, and household appliances industries. These metals are characterized by substantially larger strength-to-moduli ratios than classical steels, and result in much more important elastic unloading (springback) effects which must be accurately predicted to avoid quality issues. Finite element simulations typically show lower accuracy in predicting springback than in predicting plastic deformation. The accuracy of springback predictions may be affected by relatively small errors in the computation of the loading stress or the plastic strain contribution, which may result in larger relative elastic unloading strain errors, due to their strength-to-moduli ratios. In this work we address the prediction of the springback effects in aluminum and HHS employing a novel hyperelastic-based multiplicative large strain elastoplasticity model. We demonstrate that employing a simplest Prager-based combined hardening with this formulation, accurate consistent predictions of springback are obtained, even without resorting to typical improvements like strain-dependent elastic moduli or hardening for yield surface shape evolution.