In the large-scale production of vehicle seats, high-strength to ultra-high-strength steel alloys are the most dominant due to high requirements. The development potential of light-weight metallic construction methods using steel and aluminium has almost completely been exhausted.
The objective of the funding project was to reduce the weight of the of a seat structure by using extruded magnesium and a novel process route in manufacturing. A lighter backrest structure was to be conceived, designed and evaluated. This pre-development process integrated numerical as well as experimental methods, concluding in the validation of the generic substructures.
The project was funded by the Federal Ministry for Economic Affairs and Energy, with TÜV Rheinland Consulting GmbH acting as project management agency. As a leading global car seat manufacturer, Faurecia Autositze GmbH was responsible for coordinating the network. KODA Stanz- und Biegetechnik GmbH, being an SME, made significant contributions in toolmaking and to the manufacturing routing. On the research side, the DLR-Institut für Fahrzeugkonzepte designed the seat structure taking into account process routing and material properties. With regard to stable thermo-mechanical forming, joining by friction stir welding and concepts to prevent corrosion, the Helmholtz-Zentrum Geesthachtt contributed their expertise with magnesium materials. As a subcontractor, JUBO Technologies GmbH made significant contributions to the success of the project in surface technology.
Fumas
Impressions of the development process (left: CAD representation of the welded primary concept of the Mg backrest structure; right: Prototype of the bonded secondary concept)
Two alternative concepts were developed involving an extruded ME21 alloy. Magnesium-magnesium joining is implemented in both by means of Friction Stir Welding (FSW). The distinction is made by the magnesium-steel connection on the seat surface: Here, FSW is used again in the primary concept, while injection bonding was investigated in the secondary concept. Both variants were produced as prototypes and tested in a simplified rear crash test.
These idealised rear crash tests on the prototypes with epoxy bonded joints showed that minor improvements should probably be sufficient to meet the requirements. Deviating away from the joining technology, the core assembly of the FUMAS project could be validated as a workable magnesium crash structure.
Contact
Dr.-Ing. Elmar Beeh
Head of Department
German Aerospace Center (DLR)
Institute of Vehicle Concepts
Material and Process Applications for Road and Rail Vehicles
