A finite strain isotropic/kinematic hardening model for springback simulation of sheet metals

Crucial for the accurate prediction of the blank springback is the use of an appropriate material model, which is capable of modelling the typical cyclic hardening behaviour of metals (e.g. Bauschinger effect, ratchetting). The proposed material model combines both nonlinear isotropic hardening and nonlinear kinematic hardening, and is defined in the finite strain regime. The kinematic hardening component represents a continuum extension of the classsical theological model of Armstrong-Freclerick kinematic hardening. The evolution equations of the model are integrated by a new form of the exponential map algorithm, which preserves the plastic volume and the symmetry of the internal variables. Finally, the applicability of the model for springback prediction has been demonstrated by performing simulations of the draw-bending process.