Hardware Fabrication Validates Advanced Design for Light Weight, Low Cost Steel Closures for Vehicles

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