To create a counterweight to the challenge of the Aluframe, the 33 main flat steel producers of the world founded the ultralight steel auto body (ULSAB) project. To balance the lower specific weight of the alternative materials, the ULSAB consortium used an holistic design approach by Porsche Engineering, various grades of high strength steels and some of the advanced steel forming technologies like structural bonding, hydroforming, laser seam welding and tailor blanking. Structural bonding is a combination of traditional spot welding with adhesives. In weld bonded structure, the spot welds tends to act as crack arrestors, thereby inhibiting crack propagation. Typically, the amount of collapse for a weld bonded structure is about 15 % less than for a spot welded variant. Hydroforming is a relatively new technology for the automotive industry which enables a variety of irregular cross-sections by hydraulic expansions into dies. The use of hydroformed parts in place of stamped assemblies eliminates flanges, giving improved structural performance with a consequent reduction in forming and welding costs. Hydroforming is currently used subframes for the Vauxhall Vectra and the Ford Mondeo. Laser beam welding is used for the continuous joint between the roof and its adjoining parts. This gives an extremely rigid structure compared with conventional intermittent spot welds. Laser beam welding is currently used by some car maker like Volvo and Opel. Tailor blanking allows the combination of different steel thickness and grades to a laser welded composite panel. Its eliminate reinforcements and stiffeners, reduce the amount of subassemblies and forming dies. Tailor blanking are being used extensively on many car models throughout the world, but the ULSAB car project is up-to-date the most advanced use of tailor blankings. In the phase 1 of the ULSAB project, a weight of 205 kg was achieved for the body in white, about 65 kg less than the current average value. Despite the lower weight, the torsional rigidity could be improved by 69 %. The structural efficiency in terms of static torsional rigidity against weight war more than double the current reference value. The production cost could be reduced by 14 %.
Steel - the automotive material of the future
Stahl - Der Werkstoff der Zukunft im Fahrzeugbau
Steel World ; 1 , 2 ; 78-82
1996
5 Seiten, 9 Bilder, 3 Tabellen
Aufsatz (Zeitschrift)
Englisch
Steel - the automotive material of the future
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