Improved FEA of deep drawing at elevated temperatures of magnesium sheet materials based on a realistic modelling of their formability at process conditions

• Applicant: Professor Dr.-Ing. Bernd-Arno Behrens
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2007 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 44192561

The objective of the preceeding project was an improved model of temperature-dependent hardening and softening behaviour of a common magnesium sheet material AZ31 for a more accurate FEA of its forming via deep drawing at elevated temperatures. The quality of the improved model was assessed based on a comparison between simulation and experimental results of a deep drawing process on rectangular cups. The use of the determined flow curve, which realistically reproduces both hardening and softening of the material, in the FEA of the process leads to its higher accuracy compared to the FEA of the process with a conventionally extrapolated continuously increasing flow curve. However, numerical prediction of a deformation localisation and subsequent crack formation in the formed part was not possible as the forming path at the critical material point was outside the validity range of the forming limit curve.The objective of the new project is characterisation of formability of the magnesium sheet material AZ31 in a range of stress and strain states wider than that of the forming limit curve. The characterisation is to be carried out with the help of a method for determination of sheet metal formability based on shear-tensile tests on shear-tensile specimens combined with a method for determination of conventional forming limit curves based on stretching tests on waisted sheet blanks at process-relevant temperatures. The obtained data is to be integrated into a thermo-mechanical simulation of deep drawing at elevated temperatures. Thus, the influence of the stress state and temperature on formability of the studied material is to be described. Furthermore, it should be investigated if an improved formability prediction in the process simulation can be achieved with the determined formability description for process-relevant stress states and temperatures. With project results, an improved material modelling for magnesium sheet materials as well as a process limit extension of their processing via forming are expected to be achieved.

• DFG Programme: Research Grants