Aluminium Versus Steel for Automotive Body Weight

The latest in a continuing series of research studies suggest strongly that steel auto body structures in the near future can be as lightweight as aluminum bodies, while meeting all crash performance standards and at comparable cost of current steel structures.

Figure 1.

The studies also address crucial manufacturing challenges showing that car manufacturers fabricate and form advanced steel designs thus accelerating implementation of this technology into production vehicles.

FutureSteelVehicle Design

In its FutureSteelVehicle design, along with a weight reduction of 35%, the most recent studies of the steel industry increase the mass savings to 39% when compared to a baseline steel body structure carrying an internal combustion engine, adjusted for a battery-electric powertrain and year 2020 regulatory requirements.

The optimized FSV body will weigh just 176.8 kg, placing steel on par with today’s aluminium production designs. An industry database of present production vehicles (A2mac1) shows these light-weight advanced high-strength steel (AHSS) body structures, designed to carry heavier electrified powertrains, fall in line with the lightest internal-combustion-engine aluminium vehicles, and are on par with other concepts featuring multi-material solutions.

The incorporation of FSV technology in the study results show that car makers can avoid pursuing more costly alternatives involving competing materials and multi-material designs to achieve their goals.

Cees ten Broek, Director of WorldAutoSteel stated that the latest light-weighting projects show the continuing potential of steel and demonstrate how car makers can take advantage of steel’s design flexibility and use advanced high-strength steels (AHSS) to meet their difficult challenges for improving fuel economy and reducing green-house gas emissions.

Recent Study Results

The two most recent studies known as “FSV Final Gauge Optimization” and “FSV Near-Term Front Longitudinal Rail Shape” streamlined the FSV design and devised alternative geometry (for the front rails), respectively. The former resulted in a further mass reduction of 11.6 kg, compared to the initial FSV design, bringing the total weight savings to 39%. The latter validated two different however comparable front rail designs expanding the range of solutions available to car makers.

The first study after announcement of the FSV in May 2011 was 3B (Draw Bead, Blank Geometry and Binder Pressure) Forming and Crash Optimization. This resulted from continuing development of the multi-disciplinary optimization (MDO) process that enabled the “Nature’s Way” design used in FSV and solved the remaining forming issues presented by the FSV’s unique front rail structure.

Through this design optimization work, the highly efficient, light-weight Front Rail design is now a suitable option for future production vehicles. Further, while using the 3B Forming Process, the optimization software now fully comprises solutions to AHSS formability issues.

Figure 2. An industry database of current production vehicles(A2mac1) shows these light-weight Advanced High-Strength Steel (AHSS) body structures, designed to carry heavier electrified powertrains, fall in line with the lightest internal-combustion-engine aluminium vehicles, and are on par with other concepts featuring multi-material solutions.

Intensive use of AHSS, as demonstrated by the FSV also contributes to lower total green-house gas emissions over the entire vehicle life cycle, when compared to higher cost, more energy-intensive low-density materials. This benefit in lower total life cycle emissions indicates that steel use is consistent with a growing movement toward regulations that comprehend all sources of emissions, not only those from the vehicle-use phase.

FSV Programme

The FSV programme developed optimized AHSS body structures for four proposed 2015-2020 model-year vehicles: battery electric (BEV) and plug-in hybrid electric (PHEV) A-/ B-class vehicles; and PHEV and fuel cell (FCEV) C-/D-class vehicles.

The design and material advancements of FutureSteelVehicle are equally applicable for any automobile type although its development focused on electrified powertrains.

The FSV programme uses more advanced steels and steel technologies in its portfolio and consequently adds to the tool sets of automotive engineers around the world. It uses more than 20 new AHSS grades, showing materials that are expected to be commercially available in the 2015 – 2020 technology horizon. The FSV material portfolio includes dual phase (DP), transformation-induced plasticity (TRIP), twinning-induced plasticity (TWIP), complex phase (CP) and hot formed (HF) steels, which reach into GigaPascal strength levels and are the newest in steel technology offered by the global industry. These steels answer the call of automobile manufacturers for stronger, formable steels needed for lighter structures that meet increasingly stringent crash requirements. They are evidence of steel’s continual self-reinvention to meet automotive design challenges.

Conclusion

The design flexibility of steel enables the use of the award-winning, state-of-the-future design optimisation process that develops non-intuitive solutions for structural performance. The resulting optimized shapes and component configurations often mimic Mother Nature’s own design proficiency, which allows engineers to place specific materials precisely in the structure to most efficiently meet structural and strength requirements for managing vehicle loads.

This information has been sourced, reviewed and adapted from materials provided by WorldAutoSteel (World Auto Steel).

For more information on this source, please visit WorldAutoSteel (World Auto Steel).