UltraLight Steel Auto Body - Final Report - American Iron & Steel ...

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ULSAB’s hydroformed side roof rail provides an essential load
path for structural performance and crash energy management
from the top of the ‘A’ pillar along the roof, into the ‘B’ and ‘C’
pillars and into the rear of the structure. The hydroformed side
roof rail reduces the total number of parts and maximizes section
size, allowing for both mass and cost savings.
The raw material for the side roof rail is a welded, high strength
steel tube of thickness 1.00 mm and outside diameter of 96 mm.
The yield strength is 280 MPa.
Tubular hydroforming
Sheet hydroforming was chosen for the roof panel for weight
reduction. This process provided the opportunity to manufacture
the roof panel at a thinner gauge and still achieve a work
hardening effect, especially in the center area where the degree
of stretch is normally minimal.
With sheet hydroforming, the work hardening effect is achieved by
using fluid pressure to stretch the blanks in the opposite direction
towards the punch. This plastic elongation causes a work
hardening effect in the center area of the blank. In the second
step, the punch forms the panel towards controlled fluid pressure
achieving excellent part quality because there is no metal-to-metal
contact on the outer part surface. The roof panel is manufactured
in 0.70 mm high strength isotropic steel with a yield strength of
210 MPa.
ULSAB Final Report