Warm forming simulation of Al–Mg sheet

The accuracy of warm forming simulations depends to a large extend on the description of the yield surface with temperature and strain-rate dependent hardening and on the modeling of friction. In this paper, the anisotropic behavior of the sheet is described by using the Vegter yield locus, which is purely based on experimental measurements. For work hardening, the dislocation based Nes model is used, in which the evolution of microstructure is defined by three internal state variables. The model incorporates the influence of the temperature and strain rate effect on the flow stress by means of the storage and dynamic recovery of dislocations. It is demonstrated that the Nes model is able to describe the flow stress of Al–Mg alloys up to 250 °° C at different strain rates. It also represents the negative strain rate sensitivity behavior of Al–Mg alloys at temperatures below 125 °°C. The simulation of uniaxial tensile tests shows that the model is able to predict the strain localization. Cylindrical cup deep drawing simulations are presented using shell elements. Data from experimental deep drawing tests is used to validate the modeling approach, where the model parameters are determined from tensile tests.