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ArcelorMittal S-in motion seat study cuts weight by up to 18.3% with AHSS; introduction later this year

In 2010, leading global steelmaker ArcelorMittal launched its S-in motion range of lightweight steek solutions. (Earlier post.) Since then, the company has steadily expanded the range of solutions, which now cover many other types of vehicles and vehicle parts, including hybrid and electric vehicles, pick-up trucks, mid-size sedans and SUVs.

Front seats are the latest vehicle component to be examined as part of the ongoing development of lightweight S-in motion solutions, with a reduction in weight of up to 18.3%. The S-in motion Front Seats project identified where advanced high strength steels (AHSS) could be used to optimize and lightweight components while maintaining safety and performance. The scope of the study was a typical front seat for a C-segment passenger vehicle.

Top: Steel frame structure of S-in motion front seats. Bottom: Potential weight savings for each component of the Ultimate S-in motion seat. Click to enlarge.

Commercially available seats weigh between 11.5 and 12.8 kilograms (25.35 and 28.22 lbs); the S-in motion team first defined a baseline seat which weighed in at 12.4 kilograms (27.34 lbs). The team’s goal was to cut this to around 10 kilograms (22 kg) per seat using an optimized design and the latest AHSS (advanced high-strength steel).

The Global R&D team looked at a range of steel solutions including high-strength low-alloy (HSLA) grades, and more advanced dual-phase and complex-phase steels. Fortiform—ArcelorMittal’s range of steels for cold forming was also considered.

As a third-generation AHSS, Fortiform provides the opportunity for additional weight reduction thanks to its higher mechanical properties and excellent formability. Fortiform is particularly suitable for automotive parts with complex shapes which require crash resistance.

The use of AHSS was combined with part redesign to take maximum advantage of the advanced mechanical characteristics of the new steels. These parts included the backrest side-member, cushion side-member, gusset, and brackets. Some parts, such as the backrest side-member were redesigned by the S-in motion team to reduce the number of parts. This reduced both weight and assembly time without affecting safety.

The research team developed two S-in motion front seat designs as a part of the project.

  1. The Ultimate design reduced the weight of the seat from 12.4 to 10.1 kilograms (22.27 lbs), a saving of 2.3 kilograms (18.3%) per seat. With two front seats, the total saving could be 4.6 kilograms (10.14 lbs) per vehicle.

  2. The Efficient design reduced the weight of the seat to 10.4 kilograms (22.93 lbs), a saving of 2.0 kilograms (15.5%) per seat. However, this solution is achievable at a slightly lower cost to manufacturers. In high-volume production (over half a million seats per year), both S-in motion seat designs can reduce costs.

The two options allow seat makers to achieve a compromise between weight savings and cost without affecting safety. Both options were validated against crash load cases (front and rear crashes and luggage retention) and static load cases (seatbelt anchoring, and backrest and cushion stiffness). Material failure analysis was also performed. In all cases, both S-in motion seat concepts performed according to design standards for passenger vehicles.



Although the S-in motion Front Seats study looked at front seats for a C-segment vehicle, the solutions are applicable to other vehicle segments. The S-in motion seats would fit most C- and D-segment vehicles. The new S-in motion seat designs will be rolled-out to customers in the last quarter of 2017.



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