On the prediction of wrinkling in flexible roll forming

Flexible roll forming process is an advanced manufacturing process, for producing complex and lightweight profiles with variable cross-section. One of the major observed defects in this process is the flange wrinkling of the profiles, which has limited its development especially for the automotive industry. In this paper, the deformation mechanics of the flexible roll forming process is revisited, and the methodology for predicting the onset of wrinkling, which had previously been developed based on the wrinkling limit curve in the space of effective strain versus stress triaxiality, is improved. Then, a new criterion based on the wrinkling limit curve is proposed to predict the possibility of wrinkling in finite element analysis. The criterion is applied to analyze the influence of geometric parameters of the variable cross-section profile and material properties of the sheet on the occurrence of wrinkling. The prediction accuracy is evaluated by performing experiments with different profile shapes. Results show that the new proposed criterion can successfully predict the onset of wrinkling in the flexible roll forming process, and its utilization is recommended for predicting wrinkling in the finite element analysis of sheet metal forming processes.