The approach was to match the accelerations of the center of gravity (CG) of the aluminum vehicle to the steel version. The location of the CG is shown in the figure below.
All the steel body components were replaced by aluminum equivalents. In some cases, the thicknesses were adjusted to maintain the crash performance and vehicle stiffness. The spot welds were also changed from a conventional to a weld-bonded configuration, and tailored blank technology was used. The final aluminum version matched the steel vehicle as shown below. The stiffness of the aluminum vehicle was 67% that of the steel version, while the mass of the vehicle was reduced by a significant 200 kg (440 lb).
The true test of crash performance is the damage to the potential vehicle occupant as measured by the crash test dummy. The most important measures are the head and chest accelerations, as shown in the next two figures.
The performance of the aluminum vehicle during the critical time period, 0 to 100 msec, was almost exactly the same as the steel vehicle from the occupant's point of view.
This program was successful in showing that the mass of a vehicle is not the only factor that determines safety, provided proper design practices are followed. A steel vehicle was converted to aluminum, a process which reduced the mass by 200 kg (440 lb), and the crash performance was equivalent from the vehicle occupant's point of view.
Note: This information was presented at the 1998 International Body Engineering
Conference & Exposition (IBEC) as paper number 982389.