Design of Channel Type Indirect Blank Holder for Prevention of Wrinkling and Fracture in Hot Stamping Process

Abstract

The hot stamping process has been used in the automotive industry to reduce the weight of the body‐in‐white and to increase passenger safety via improved crashworthiness. In this study, a new form die with a simple structure that can prevent defects such as wrinkle and fracture is proposed for the manufacture of hot stamped components. The wrinkling at the flange cannot be eliminated when using a conventional form die. It is known that the initiation of wrinkling is influenced by many factors such as the mechanical properties of the sheet material, geometry of the sheet and tool, and other process parameters, including the blank holding force (BHF) and the contact conditions. In this research, channel type indirect blank holder (CIBH) is introduced to replace general blank holder for manufacturing the hot stamped center pillar. First, we investigate the tension force acting on the blank according to the channel shapes. We determine the appropriate range by comparing the tension force with the upper and lower BHFs in a conventional stamping process. We then use FE‐analysis to study the influence of the slope angle and corner radius of the channel on the formability. Finally, the center pillar is manufactured using the form die with the selected channel.