The quality of the results of simulations significantly depends on an accurate specification of material parameters. For some shape forming operations, e.g. by expanding mechanical mandrel, embossing operations, etc., strain rate effects are not considered to be important and the results of quasi-static material tests may be adequate. However, for other operations, such as DWI pre-forming and HVF shape forming, strain rate effects are significant and consequently estimation of the material response under dynamic loading conditions will be necessary. The first requirement is the determination of the material's stress-strain response up to rupture. Given the presence of initial anisotropy due to processing, this necessitated testing in three different material orientations.
To identify the strain rate dependent material properties, the split Hopkinson bar experimental test was used. Clear strain rate dependency was obtained; which was incorporated into material models used for simulations of the shaping processes