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The development of light-weight vehicles that are safe and durable has become an imperative for the automotive industry. The complexity of the vehicle design, the variety of available material grades, and the disparate needs (imposed by energy absorption, intrusion resistance, durability and stiffness) can make the search of light-weight design quite daunting and tedious. Optimization techniques, used in conjunction with CAE analyses, can be effective in arriving at a viable design by searching a wide spectrum of alternatives in the design space. Through a case study involving mass and material optimization, it is shown that utilization of advanced high-strength steels (AHSS) can be exploited judiciously to arrive at strong, stiff, and durable automotive structures. Multiple linear load cases, along with a non-linear roof crush load are considered in this study.

The front bumper of a current production vehicle, which is made of hot-stamped 15B21 aluminized steel, was studied for mass and cost reductions using the Advanced High Strength Stainless Steel product NITRONIC® 30 (UNS Designation S20400) manufactured by AK Steel Corporation. This grade of stainless steel offers a combination of high ductility and strength, which was utilized to significantly modify the design of the bumper beam to incorporate geometry changes that improved its stiffness and strength. The structural performance of the bumper assembly was evaluated using LS-Dyna-based CAE simulations of the IIHS 40% Offset Full-Vehicle Impact at 40 mph with a deformable barrier, and the IIHS Full Width Centerline 6 mph Low-Speed Impact. Optimization of the bumper beam shape and gauge was performed using a combination of manual design iterations and a multi-objective optimization methodology using LS-Opt.