By Michael Freeze
Members of the steel industry provided some insight and analysis on high-strength steel properties and reparability on Thursday. The three-man group, David Anderson of American Iron & Steel Institute, Jody Shaw of United States Steel Corp. and Blake Zuldema of Mittal Steel USA gave attendees a snapshot of the fundamental work being done within the last year. Specifically, the group elaborated on the Lightweight Front End Structure project (LWFES), a partnering effort Shaw co-chaired with domestic automakers Ford and GM.
The objective of the LWFES project was to document solutions that balance the interaction of material, manufacturing and performance in the lightweighting of steel automotive structures. The project's focus was on the automotive front-end system solutions that address high-volume manufacturing and assembly.
According to the project's progress report, the advanced high-strength steels (AHSS) solutions would provide choices and consequences that address real-world challenges faced in the vehicle development process. A comprehensive knowledge-base design tool was developed to capitalize on a set of robust AHSS automotive design guidelines relating choices to consequences.
"On the front rail bumper system, we save 25-30 percent of the mass of the rail bumper system using advanced high-strength steels," says Shaw. "Then we built a national property - a retrofitted production vehicle, then crashed it into a wall and validated the results."
Analytical and physical testing was carried out on both the original and the redesigned rail system. The AHSS rail system and bumper were manufactured and tested to compare performance with the conventional design it replaced. The group conducting an NCAP 35-mph rigid-barrier impact test on the donor vehicle and encountered on a slight problem.
"We built two vehicles," says Shaw. "The first one messed up and hit the wall at 17 mph, which wasn't the full 35 mph end cap test. So, we thought we'd challenge our repair procedures."
According to the project's progress, the AHSS design achieved a mass reduction of 8.77 kg (22.36 percent) compared to the baseline design. The performance of the AHSS design was similar to that of the baseline design. After moving ahead with the 35-mph rigid-barrier impact test with the AHSS rails and bumper, it further validated the AHSS design.
The group concluded that the use of AHSS in conjunction with effective part design can result in significant mass reductions without compromising crash performance.
"Overall, we wanted to provide input to our customers the way we think high strength steel should be repaired," concludes Shaw. "And hopefully, our customers will develop repair procedures to send out to repair shops."