Metal Forming Characterization and Simulation of Advanced High Strength Steels

The remarkable evolution of steel technology in recent years has resulted in the development of new High Strength Steels (HSS) that are increasingly used in today's automobiles. The advanced performance of these grades in ductility and rapid hardening characteristics provides an opportunity to stamp complex geometries with in-panel material strengths far exceeding those of conventional high strength grades of steel. This provides an opportunity to improve an automotive body's performance in crash, durability and strength while reducing the overall weight of the vehicle. An improved understanding of the forming characteristics of these advanced HSS and accurate prediction of the material processing strain will allow vehicle designers to fully explore the opportunities of increased yield, strain hardening, formability and strength and the potential this creates to reduce mass and improve the performance of the automotive body.

In this study, material testing is performed on five different grades of steel, including conventional mild steel, conventional HSS and several grades of advanced HSS, to establish material properties, forming characteristics, springback characteristics and stamping failure criteria. This data is then incorporated into a forming simulation for correlation between test and simulation. A T-channel, which incorporates several different forming modes typical of automotive stampings, is stamped in the lab and then simulated on the computer. Comparison shows good correlation of the predicted and actual strains and splitting failures. The study provides conclusions on the advantages of the advanced HSS grades to meet the cost-effective weight reduction requirements of the automotive body.