Products and solutions, 2001-09-11, 02:00 AM
New steel door concept cuts weight by 22 percent
At IAA 2001 Thyssen Krupp Stahl AG will be presenting an ultralight steel auto door developed by the ULSAC consortium. The door weighs 22 percent less than the reference door selected when the project started in 1998, which at the time was the lightest door in volume production. Although lighter, the new door is no more expensive than conventional steel doors.
ULSAC (Ultra Light Steel Auto Closures) is an international consortium of 33 steel producers, one of them ThyssenKrupp Stahl. This initiative, a follow-up to the ULSAB (Ultra Light Steel Auto Body) project, was formed to develop weight-optimized steel automotive closures. Closures such as engine hoods and deck lids account for some six percent of a car`s overall weight.
The part on show at IAA is a front door structure which, including small parts, is made up of 25 individual components. It owes its low weight of exactly 10.467 kilos to a completely new design principle. Key to this is a tubular frame which forms the backbone of the door, bearing the main loads and rendering the conventional door inner panel and various reinforcements superfluous. The panels for the door`s outer skin are mounted on the frame.
The hinge and lock tubes on the inner frame are hydroformed parts, while the two horizontal tubes are made from high-strength DP 800 dual-phase steel, which has a tensile strength of up to 1,000 megapascals. This gives the ULSAC door the kind of crash stability for which conventional doors need an additional steel side intrusion beam. The ULSAC consortium tested the crash strength of its door in comparison with three frameless side doors from current production models. The ULSAC door showed itself to be far superior, withstanding side intrusion of almost 400 millimeters before failure and thus absorbing considerably higher forces than the production doors.
Obviously, the ULSAC companies also examined their new door design for economic viability. Calculations were based on the ULSAB cost model, which assumes production of 60 vehicles per hour, or 225,000 vehicles per year. The findings showed that volume production of the new door is possible at no additional cost. Highly attractive in both technical and economic terms, the ULSAC door has aroused a great deal of interest in the auto industry, and several major carmakers have already announced that they intend to consider the concept in their future developments.
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