Identification of an advanced hardening model for single phase steels

Sheet metal forming processes cover a wide range of applications in industry. In order to model sheet metal forming processes using numerical simulation an accurate description of the material behavior is required. To this end a material model has been implemented which is capable of capturing the move- ment and proportional expansion of the yield surface along with the change in the shape of the yield surface. The former is described as kinematic and isotropic hardening, respectively, and the latter is termed as distortional (cross) hardening. Once the model is implemented the second step consists in identifying the material parameters. In this contribution, a strategy for the identification of material param- eters is presented. The strategy is based on identifying the isotropic hardening, combined hardening (isotropic-kinematic hardening), and complete hardening model (isotropic-kinematic-cross hardening) sequentially, in such a way that the parameter values identified in the previous step are used as start- ing values for the next step. Hence, the isotropic and kinematic hardening are first identified using the monotonic shear and Bauschinger shear test data, then the distortional (cross) hardening effect is de- termined using orthogonal tension-shear data using the isotropic-kinematic hardening parameter values as starting values. The material model was implemented in LS-DYNA using user defined material and LS-OPT based parameter identification for the steels LH-800 and DC06 is performed. The identified pa- rameters are first validated and then used in F.E. simulations using ABAQUS and LS-DYNA. A complete account on application of identified material model is presented in the talk ”Numerical investigation of draw bending and deep drawing taking into account cross hardening” presented at this meeting.