FE modelling of the semi-hot forming of 7000 aluminium sheet and prediction of component properties after ageing with ANN.

Due to the ever-stricter emission limits for automobiles, lightweight construction is becoming increasingly important in the automotive industry. Vehicle mass can be reduced through improved manufacturing processes, design methods and materials. Aluminium alloys of the 7000 series offer immense lightweighting potential due to their high specific strengths. At room temperature, however, the elongation at break of aluminium is low, resulting in poor cold formability. By means of semi-hot forming (SHF 150-250 °C) or hot forming (350-450 °C), formability can be increased due to the elevated process temperature. When using SHF, energy costs can be saved compared to hot forming and production can be more efficient both economically and ecologically.

Numerical process analysis of the forming of components made of 7000-series aluminium has so far only been used to a limited extent. The focus of research work has been on forming processes in the cold state or on experimental investigations of hot forming. The subsequent heat treatments, such as cathodic dip coating (CDC), have also not been modelled. Furthermore, final properties such as residual tensile strength and formability after forming of 7000 series alloys, which are also influenced by heat treatments, currently cannot be represented.

Therefore, the research need for a detailed numerical simulation model to represent the SHF of 7000 aluminium can be derived from the immense potential of SHF. The model should describe the temperature-dependent material flow, strain hardening and failure behaviour at the process conditions relevant for the HWU. For this purpose, a detailed material characterisation has to be performed. Furthermore, trained ANN offers the potential to extend the conventional transfer of results after a numerical simulation. For this purpose, ANN are trained and verified on the results of different thermo-mechanically treated tensile tests. In combination with numerical finite element simulation, the ANN should predict the final component properties after cathodic dip coating.