Work hardening descriptions in simulation of sheet metal forming tailored to material type and processing

• A set of equations for the flow stress of metals is derived that covers a wide range of applications.
• Stage IV hardening observed is considerably larger than expected from the measured mean cell size as a function of strain.
• A reference hardening model including the dynamic effect of strain rate and temperature.
• A model that describes the recovery effect for forming applications at enhanced temperatures.
• An advanced description for dual phase metals is developed that includes the effect of kinematic hardening.

In the previous decades much attention has been given on an accurate material description, especially for simulations at the design stage of new models in the automotive industry. Improvements lead to shorter design times and a better tailored use of material. It also contributes to the design and optimization of new materials.The current description of plastic material behaviour in simulation models of sheet metal forming is covered by a hardening curve and a yield surface. In this paper the focus will be on modelling of work hardening for advanced high strength steels considering the requirements of present applications. Nowadays work hardening models need to include the effect of hard phases in a soft matrix and the effect of strain rate and temperature on work hardening.Most material tests to characterize work hardening are only applicable to low strains whereas many practical applications require hardening data at relatively high strains. Physically based hardening descriptions are used for reliable extensions to high strain values.