Air Bending Process for Load Optimised Profiles

In this paper the air bending of Tailor Rolled Blanks (TRB) to load optimised profiles is investigated. A new flexible modular tool system has been developed in order to locally adapt the die height to the spring back which is more pronounced in thinner areas in comparison to thicker areas of the TRB. With the new tool system the dies can be modulated according to the thickness distribution of the Tailor Rolled Blank, whereas the amount of die lifting depends on the thickness difference and the corresponding variance of mechanical properties. In bending tests with several specimens having a constant thickness a linear relation between the increasing part angle and a stepwise increased die lifting was observed. With this linear dependency the amount of die lifting can be calculated and thus applied on bending of TRB. Special consideration is required for the die adjustment in the area of the linear thickness transition, therefore three different die arrangements have been investigated. The results of different bending tests are compared and evaluated in order to apply the new technique to form a new car body floor structure in profile intensive construction. By using load optimised profiles in combination with a steel 22MnB5 which has been heat-treated at defined sections the survival space of a car passenger in a side pole impact has been enormously increased by more than 40 %.