FEM stress state analysis on springback reduction methods: Variable blank holder force and stake bead

Abstract

The sheet metal forming process is characterized by elasto-plastic strains. Therefore, after removing the stamped part from the dies, it presents the springback phenomena. The present paper analyzes the adoption of a springback reduction methods in a hat bending forming process, i.e, the use of variable blank holder force (VBHF) and stake bead (SB). Based on a Finite Element Method (FEM) stress state analysis, springback magnitudes were correlated to the stress moment in the hat shape side wall. Both springback reduction methods, VBHF and SB, were well described and its practical and economic use in the industry discussed. The FEM stress state anlaysis showed a great correlation to the springback phenomena.