Advanced Materials, Manufacturing Processes Foster Successful
Try-Outs Of ULSAC Concept
DETROIT, MI, February 16, 2000 – Comparisons of finite
element analysis and initial measurements of demonstration hardware
indicate that the UltraLight Steel Auto Closures (ULSAC) frameless door
design has achieved the program’s aggressive design objectives for
improving mass and structural efficiency.
Preliminary results indicated a mass savings of approximately 27
percent, compared to a benchmark average of similar doors in eighteen
1997-model year vehicles from Asia, Europe and North America.
Porsche Engineering Services of Troy, Mich., which is conducting the
ULSAC study on behalf of a consortium of the world’s leading steel
producers, fabricated the demonstration hardware to validate its initial
design.
In building the frameless door demonstration hardware, PES
successfully stamped outer panels in thicknesses of 0.6 mm and 0.7 mm
high-strength steel sheet and used
different grades and yield strength levels, including bake hardenable
(210, 260 MPa), dual phase (500, 600 MPa), rephosphorized (260 MPa) and
isotropic (260 MPa).* These gauges are relatively thin in comparison to
typical door outers on current automobiles.
Use of these grades and gauges represent significant advancements and
lead directly to the substantial weight savings and structural
performance that are the hallmarks of the project. Three of the six
grades (bake hardenable 210, 260 MPa and dual phase 600 MPa), which are
state-of-art steels for closures and representative grades for
comparison purposes, will undergo dent testing.
With the fabrication and testing of demonstration hardware, the ULSAC
project is nearly complete. Final results will be available in May in a
comprehensive engineering report detailing the design, CAE results,
physical testing, material and manufacturing specifications, economic
analysis and cost model, and other key data. Available at the same time
will be demonstration hardware consisting of assembled doors and sets of
individual parts.
The validation phase of the ULSAC project seeks not only to validate
the design, but to demonstrate manufacturing feasibility. The validation
work encompasses:
- Detail design optimization and CAE analysis of structural
performances
- Forming simulation of stamping and hydroformed parts
*Bake hardenable steels increase in strength when
undergoing a "baking" treatment, such as that used to cure automotive
paints.
Dual phase steels have two principal metallurgical
phases, or structures. These steels rapidly increase in strength as they
are formed into automotive parts.
Rephosphorized steels have small additions of
phosphorus that provide an economical means to increase the strength of
automotive sheet steels.
Isotropic steels have nearly the same strength and
properties in all directions.
- Build of door structure assemblies, for testing and demonstration
hardware
- Comparative testing for dent-resistance and oil-canning (dimple
testing)
- Testing for structural performance
- Validation of forming simulation with strain analysis
- Documentation of manufacturing parameters such as press environment,
lubrication, tonnage, etc.
- Documentation of material properties
- Documentation of dimensional control data
- Economic analysis to evaluate cost effectiveness
PES and its subcontractor Schuler/SMG (Stuttgart, Germany) will
conduct additional try-outs using an active hydromechanical sheet
forming process. If successful, this alternative forming approach could
yield door outer panels with favorable dent resistance. Results of the
sheet hydroforming try-outs will be available in early 2001.
Other fabrication highlights include PES’s successful use of an
ultra high-strength steel tube of 1.5 mm wall thickness and 600 MPa
yield strength for the door intrusion beam. PES also effectively
incorporated hydroformed high-strength steel for hinges and latch tubes,
which additionally achieved excellent fit in the door assembly.
A comprehensive discussion of this information is available in ULSAC
Technical
Transfer Dispatch #1.
The Automotive Applications Committee (AAC) is a subcommittee of the
Market Development Committee of AISI and focuses on advancing the use of
steel in the highly competitive automotive market. With offices and
staff located in Detroit, cooperation between the automobile and steel
industries has been significant to its success. This industry
cooperation resulted in the formation of the Auto/Steel Partnership, a
consortium of DaimlerChrysler, Ford and General Motors and the member
companies of the AAC.
American Iron and Steel Institute/
Automotive Applications Committee:
AK Steel Corporation
Bethlehem Steel Corporation
Dofasco Inc.
Ispat Inland
Inc.
National Steel Corporation
Rouge Steel
Company
Stelco Inc.
United States Steel Corporation
WCI Steel, Inc.
Weirton Steel Corporation