Flange wrinkling in flexible roll forming process

Flexible roll forming is an advanced sheet metal forming process for producing variable cross section profiles. Flange wrinkling at the transition zone where the cross section changes is a major defect in the flexible roll forming process. In this paper, the flange wrinkling at the transition zone is studied using finite element analysis. The results showed that the strip deformation at the transition zone can be considered as a combination of two strip deformations observed in the conventional roll forming process and the flanging process. According to finite element analysis results, when the flange wrinkling occurs, compressive longitudinal strain is smaller than the necessary compressive longitudinal strain calculated by mathematical modeling to obtain the intended profile geometry in the compression zone. Therefore, comparison of compressive longitudinal strain obtained from the finite element analysis and the necessary compressive longitudinal strain is a good criterion to predict the flange wrinkling occurrence. A flexible roll forming setup was developed. Longitudinal strain history is obtained from the finite element simulation and is compared with the experimental data from the flexible roll forming setup. Results show a good agreement and confirm the finite element analysis.