Damage in Sheet Metal Bending of Lightweight Profiles

Funding: German Research Foundation (DFG)
Project: CRC/TRR 188 • Subproject A05
Contact: Dr.-Ing. Rickmer Meya

Bent parts made of high-strength steel materials are often produced by processes such as air or die bending.

The stress state and, thus, the damage is only slightly influenced by conventional process parameters during air bending so that the so-called RSS bending was developed. This process is able to superpose compressive stresses in the forming zone in a controlled manner. Thus, damage can be reduced. The hypothesis that damage control based on the modification of the hydrostatic stress state can significantly increase the performance of bent parts in terms of absorbed impact energy, stiffness, and fatigue strength has been confirmed. To determine the notched impact strength of bent sheets, a modified specimen with a groove has been developed which generates a stress concentration directly in the forming zone. Due to the stress superposition during RSS bending and the resulting reduced damage, the absorbed impact energy is increased by up to 19% (see figure).

Influence of different bending methods on damage and performance