Mass Reduction: a Report by fka

Vehicles have historically been predominately made from conventional steel. Competition of OEMs and governmental demands for safer, lighter and more fuel economic cars led to the market entry of new materials such as new high-strength steels or aluminium. In this study especially the potential mass reduction impact of aluminium in comparison to conventional steels as well as to new steels is examined.

The main target of this study, conducted by Forschungsgesellschaft Kraftfahrwesen mbH Aachen (fka) on behalf of WorldAutosteel,  is to visualise the weight difference between steel and aluminium and to communicate a feeling what a real weight difference can be. Especially the difference between recent and optimised steel design compared to aluminium is pointed out. So a perception of the differences between aluminium and steel concerning the mass potential of the body-in-white (BIW) is given. Therefore the following two often-stated assumptions are analysed:

  1. Vehicle mass can be reduced by 25 % through the application of modern high-strength
    and advanced high-strength steels,  and
  2. vehicle mass can be reduced by up to 50 % by the application of aluminium.

The basis for these percentage comparisons is usually a 1990’s-era former steel design. In this steel design very little high-strength or advanced high-strength steels were used. The other side of the spectrum for steel designs is the optimised steel design that contains up to 90 % high-strength (HHS) or ultra high-strength steels (UHSS). Today’s vehicles are built in recent steel design that can be settled between the former and the optimised steel design.
Besides several vehicle body structures and components made of steel and aluminium are described and compared concerning their weight reduction potential. To compare mass in a neutral way, performance of the body structures and components must also be checked. But to establish fundamental reference points, a detailed description of material characteristics and basic structural behaviour for different materials are demonstrated first in this document.

To show the potential of aluminium and recent steel body structures, the body-in-white (BIW) of several vehicles is specified concerning body mass. To show the potential of optimised steels concept cars like the UltraLight Steel Auto Body, the Arcelor Body Concept and the ThyssenKrupp Steel NewSteelBody (NSB®) are summarised, showing mass reduction potential, performance and costs. Furthermore the weight development in the period of time between 1990 and 2005 is shown with the example of several vehicles.

Different components such as hoods, bumpers and front ends are compared concerning steel and aluminium applications based on similar performance. The analysis of hoods is based on studies by Forschungsgesellschaft Kraftfahrwesen mbH Aachen (fka) and the UltraLight Steel Auto Closures (ULSAC) study for engine hoods. Also the bumper and front end chapters are based on fka studies.