The study built upon research EDAG carried out in 2012 for the U.S. Environmental Protection Agency (EPA) examining mass reduction, safety and cost variables in a mid-size crossover Toyota Venza. The EPA study aimed to reduce vehicle mass by 20% while meeting all NHTSA and IIHS safety standards, and maintaining or improving performance, handling and braking.
The previous study found that using a maximized high-strength steel (HSS) Venza body resulted in a body mass reduction of only 14% over the baseline production vehicle body, and that the study's total vehicle mass reduction target could not be met without the use of aluminum closures and chassis components.
The new study focused on taking the steel Venza BIW and developing a CAE concept for an aluminum BIW with equivalent performance but with a target BIW mass reduction of more than 30 percent% over steel, subject to the following criteria:
- The project is a "feasibility study" only.
- The concept was to employ a riveted and bonded construction with use of extrusions, sheet, and castings.
- The use of castings in the BIW was to be minimized or reasons of cost and complexity.
- Aluminum materials used in the study will be based on "existing technology" only.
- No detailed manufacturing feasibility will be performed in this stage of the project.
For the feasibility study, EDAG selected four basic aluminum materials: 6022 T6 Alloy Sheet; 5754 O Alloy sheet; 6082 T6 Extrusion; and generic casting. Properties of the metals were supplied by the Aluminum Association and a basic material model created in LS-DYNA using MAT 24 (PWL or BL stress strain curves only).EDAG emphasized that this was only a structural feasibility study (i.e., formability and environmental factors were not considered).
The cost increase was about $1 per kilogram of weight saved, which consumers will recoup in fuel savings in less than two years of operating the more efficient vehicle.
The research was presented at the Society of Automotive Engineers (SAE) World Congress 2013 in April during a panel discussion on advances in lower weight materials. It comes at a time when automotive aluminum use is at an all-time high, with automakers announcing plans to incorporate more of the metal into vehicle designs-doubling aluminum's 2008 share of the automotive metals mix by 2025.