An experimental approach for blankholder force determination for DP600 with different material flow strain rates in the flange during stamping

Abstract

Manufacturing efficiency is directly related to the parameters of the process and the material used. In sheet metal industry, the manufacturing process often results in changes in design of the tool to safely stamp the product. These changes in design could occur due to use of a new material with better formability, adjustments to the design of tools and/or the process parameter variation. In order to avoid the trial-and-error procedure, forming limit curve is an effective method for this assessment and is widely used by several authors in recent publications, that is, the use of forming limit curve could be useful to decrease the trial-and-error procedures and tool-developing expenses. Despite being widely used in the industry, a process parameter that has been barely researched is the influence of blankholder force on the drawability of advanced high-strength steels, which contains multiple phases on microstructural level. The main aim of the present study was to analyze the influence of the blankholder force on the formability of DP600 steel. Blankholder forces of 130, 80 and 58 tons were considered. The experimental results led to a detailed understanding of the blankholder force influence during the process. The blankholder force variation promoted different material flow strain rates in the flange during the stamping—higher strain rate increased the bending effect on the die radius. As a result, an experimental approach that allows the blankholder force determination as a function of the different strain rates of the flange flow of the stamped sample was proposed.