It ain’t heavy its collaboration

An unpresidented technical collaboration between 35 steel companies has resulted in the launch of a superior steel autobody which is 25% lighter than the project’s benchmarked car bodies (see left).

ULSAB (UltraLight Steel Auto Body) cost $22M to develop in a four year project to make a lightweight and structurally sound autobody which was also affordable and viable for high volume production. The result can reduce car weight for mainstream markets and costs less to build than other body structures in its class: $947 to manufacture and assemble a ULSAB structure compared to $980 for the Year 2000 reference structure.

Steel is still the preferred material of the auto industry and ULSABrealises substantial weight reductions and is easy to recycle. There are no safety or reliability compromises, in fact the body has improved strength and rigidity.

The body structure weighs 203kg: 25% less than the average bench marked in the concept phase of the study. Torsion and bending tests show 80% and 52% improvements respectively. Throughout the project performance measures included analysis of static torsional rigidity, static bending rigidity and body structure modes. Static torsional and bending rigidity refer to body stiffness and the body structure modes refer to the shapes the body assumes at its natural frequencies, which can influence noise vibration and harshness. These factors affect the ride and handling and structural feel of an automobile and have a direct impact on ride satisfaction.

Crash Behaviour

Super-computer analysis indi-cated excellent crash behaviour in the following crash events:

* 35mph frontal NCAP (speed exceeds legal safety requirements by 17%)

* 55km/h 50% offset AMS frontal impact

* 35mph rear moving barrier (speed exceeds exceeds legal safety requirements by 17%)

* European side impact Roof crush

Holistic approach

ULSAB was developed as an integrated system not the assembly of individual comp-onents. Emphasis was on total structure analysis: looking at how changes in one area effect another.

It is a monocoque structure with key hydroformed parts. Body parts are reduced by 20% to 96 major parts, and 158 total parts.

The materials and processes used are all commercially available: high strength steels, steel sandwich material, tailored blanks, hydroformed components and assembly laser welding for reduced weight and structural efficiency. High strength steel is used for 90% of the structure some grades and thicknesses of steel not commonly used in auto bodies. These absorb equivalent energy with less mass than mild steel and can handle the greater springback and draw angle of high strength steel during stamping.