Forming study on a tailor rolled blank (TRB) structure- formability evaluation and model verification

Abstract

Tailor rolled blank (TRB) technique, as a relatively novel configuration, is of potential to fulfill the lightweight design. The examination of TRB defects in stamping process using traditional forming limit curve (FLC) is challenging. In this paper, the forming limit surface (FLS), which considers thickness changes, was used to evaluate the formability of front longitudinal beam (FLB) with TRB structure. A numerical model was developed to study the strain distributions and thickness transition zone (TTZ) movements during the TRB forming process. The effects of tool parameters (die clearance and draw-bead) on formability and TTZ movement were investigated. Results showed that the adaptive die gaps and segmented draw-beads were required in tool design to reach a better forming quality in the formed part. Besides, TTZ movement appears to be more structural dependent because the movements near the area with transition corner were larger and suffered smaller impact from parameter changes. The measured thicknesses of typical sections from formed part agree well with those predicted by simulation. This result confirms that the simulation strain used in formability evaluation was relatively reliable.