P 930 – Extension of the forming limits of high strength steels in bending processes using innovative process management and tools
Because of increased requirements of customers for economical and ecological products innovative lightweight structures are increasingly used. This demands the use of lightweight materials. In addition to aluminum, magnesium and titanium especially ultrahigh-strength steels are used, which are characterized by a high weight-specific strength and economic efficiency.
Because of the high strength and low ductility of these materials it is necessary to adapt or modify conventional forming technologies in order to process these materials. Especially in air bending, the process limits are reached early so that customer-specific requirements can not be accomplished. This is particularly true when using bending radii which are smaller than the thickness of the material used. Furthermore, the increased strength results in higher bending forces, which results in higher residual stresses and springback. However, the requiered dimensional and geometrical accuracy is not reached.
Therefore, the failure behavior of high strength steels in air bending and roll forming were investigated in this research project. The generated knowledge of the material behavior was used to adapt conventional bending processes in order to process these materials. For that, the conventional bending processes were modified by applying an additional stress during the process. The experimental results show that the stress superposition leads to an extension of forming limits when processing high strength steels. In addition to the experimental studies, numerical investigations were carried out. For this, conventional material testing methods were used. Furthermore, advanced material models were also applied to investigate the damage accumulation. The generated knowledge was used to optimze the processs and to obtain a deeper process understanding of the process. Following this, the previously generated knowledge of the processes was used to manufacture an industry-oriented prototype.
Only available in german language.
FOSTA – Research Association for Steel Application