On the Development of Novel Light Weight Profiles for Automotive Industries by Roll Forming of Tailor Rolled Blanks

Abstract

Due to continuously increasing demands on safety, comfort and ecological performance, different lightweight construction concepts have been searched for and applied by the automotive industry lately. This paper focuses on the development of novel light weight profiles by roll forming of tailor rolled blanks (TRBs). It covers analytics, experiments and FE analysis. At the beginning, state of the art tools were used for a fundamental process layout. The results show, that their application with respect to the varying sheet thicknesses within the blanks is generally acceptable. However, it may be concluded that TRBs as semi-finished products for roll forming operations call for a well adapted pre-cut of the blank. In a second step, roll forming of TRBs to a symmetrical U-profile with constant roll gap was investigated. For this purpose, experiments on a conventional roll forming line and corresponding FE simulations were conducted. Both show very similar results for the final bending angle of the part. Nevertheless, variability in bending angle of up to 14.3° is witnessed between the areas of different sheet thickness on one part. Thus, one may conclude, that a sheet thickness dependent adaptation of the roll gap is necessary for closer tolerances. A vertical and horizontal adjustability of the rolls seems appropriate to meet this purpose. With respect to these findings, two different tool kit concepts were developed and investigated by means of FE analysis. Both aim at a real-time adjustment of the roll gap to the actual sheet thickness within the stand. On the one hand, a force-driven self-positioning of the rolls was simulated. On the other hand the positioning of the rolls was preset in accordance to the feed of the sheet and its thickness distribution. Both concepts are discussed by their effect on the final bending angle of the roll formed U-profile.