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Steel vs.
Aluminum:
UltraLight Steel Auto Body (ULSAB)
The ultra-light steel auto body
was a $22 million project to design a vehicle by optimizing
the inherent properties of steel and using state-of-the-art
manufacturing processes. To begin the process, midsize 4 door sedans
were benchmarked to determine current performance standards.
Thirty-two different cars representing varying worldwide customer
requirements were selected for benchmarking. ULSAB
uses High Strength Steel and Ultra High Strength Steel for more than
50 per cent of the body structure. ULSAB defines High Strength
Steel as yield strength 210 through 550 MPa and Advanced High Strength
Steel as yield strength above 550 MPa. Material thickness from
0.65 mm to 2.0 mm. HSS
and UHSS were used where the design required certain crash and strength
characteristics.
| 1997
Current Vehicle Averages |
| Mass: |
271 kg |
|
| Static
Torsional Rigidity: |
11,531
Nm/deg |
|
| Static
Bending Rigidity: |
11,902
N/mm |
|
| First Mode: |
38 Hz |
|
| |
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| ULSAB |
| Mass: |
205 kg |
|
| Static
Torsional Rigidity: |
19,056
Nm/deg |
|
| Static
Bending Rigidity: |
12,529
N/mm |
|
| First Mode: |
51 Hz |
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Crash
Targets
- 35 mph NCAP 0
deg Frontal
- 55 km/h 50 deg
AMS Frontal offset
- 35 mph Rear
moving Barrier
- 50 km/h European
Side Impact
- Roof Crush
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Results
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ULSAB met all crash
requirements even at speeds exceeding some requirements.
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Compared to the
average of the benchmark fleet, the ULSAB structure saved 25% in
mass. Compared to the heaviest of the benchmark vehicles,
ULSAB saved 36% in mass.
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Torsion and bending
tests were improved by 80% and 52% improvement respectively
-
First body structure
mode indicates a 58% improvement
Although, reducing weight
without sacrificing performance was ULSAB's priority, affordability was
also important. The cost model used comprehends United States
manufacturing costs, including investments for both plant and tooling,
piece fabrication, costs and assembly costs, through to the end of the
body shop. The model estimated the ULSAB body structure to cost $947,
proving that a steel automotive body structure can be designed and
manufactured to achieve reduced weight objectives with no cost penalty
and a potential for cost reduction!
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