Research on warpage in roll forming of the hat-shaped part using a five-boundary condition forming angle distribution function

In this study, the small-section profile hat-shaped roll bending part is used as the research object. Aiming at the issue of lacking scientific theory guidance for the bending angle distribution in roll forming, which leads to defects in the forming process and reduces the forming accuracy and quality of the product, a forming angle distribution function with five-boundary condition is proposed. Furthermore, an optimal forming angle distribution method is optimized and obtained on the basis of the distribution interval of forming angle under five-boundary condition determined by the previous research. Then, the generation mechanism of the warpage defect of the hat-shaped roll bending part is simulated and analyzed based on the optimized distribution method for the first time. Through the change of the maximum deviation of z-coordinates, z′, and fluctuation of the edge wave, ∆z, the influence of the forming angle, sheet thickness, and material yield strength on the warpage defect in the roll forming process is studied and verified by experiments. The results show that the stress, strain, fluctuation of the edge wave, and maximum deviation of z-coordinates based on the optimized distribution method are smaller than those of other distribution methods, showing its superiority in forming process. In addition, the peak longitudinal strain increases as the forming angle increases and the warpage decreases as the sheet thickness and yield strength increase.