The interest in using magnesium for safety components is rapidly growing in the automotive industry. But their applicability is essentially dependent on the availability of reproducible and sufficient mechanical properties. Magnesium die casting components however often display large variations in the mechanical behavior as a result of their local microstructure (imperfections and grain morphology). In this study the instrument panel of the new Opel Vectra (model 2002) was characterized using quasistatic and dynamic round miniature and flat tensile test specimens. The aim was to identify the local variations in the mechanical properties (strength, ductility, fracture behavior) across complex magnesium die casting components and to establish quantitative correlations between the determined local mechanical properties and the corresponding local microstructure. The experimental method, which was developed at Fraunhofer Institute of Materials (IWM) is characterized. In order to detect imperfections on the fracture surfaces of the broken miniature specimens one half was investigated using a scanning electron microscope (SEM). The imperfections are divided into pores and micro-cracks for later correlations between the local grain morphology and the materials data gained in tensile tests. The amount of imperfections was measured using the quantitative image analysis program ImageG. The second half of each miniature tensile test specimens was prepared for metallographic investigations. With the aid of microstructural analyses of the tested specimens empirical correlations between the local grain structure and the resulting local mechanical properties were derived. The correlations between the local die casting conditions and the corresponding grain morphology conventional die casting simulations can be used to establish 'topographic maps of the local material properties' as a function of the die casting design and a certain set of process parameters. Crash simulations of the instrument panel were carried out to define the distribution of local loading conditions, the global deformation and the local fracture under crash conditions. The simulations were verified by component tests conducted by the Adam Opel AG. With the linkage between the crash simulations and the advanced die casting simulations a tool has been derived which allows a time-saving and costly virtual development method of safety related structural components.
Correlation of local mechanical properties and corresponding microstructure of an AM50 die cast instrument panel for an improved crash worthiness design
Lokale Werkstoffcharakterisierung für Verknüpfungen von Gieß- und Crashsimulationen für ein Instrumentenpaneel aus der Druckgusslegierung AM50
2002
7 Seiten, 8 Bilder, 2 Quellen
Conference paper
English
Magnesiumlegierung , Druckgusslegierung , Automobilindustrie , Sicherheitseinrichtung (Fahrzeuginsasse) , mechanische Eigenschaft , Mikrostruktur , Pore , Mikroriss , Korngefüge , Zugfestigkeitsprüfung , REM (Rasterelektronenmikroskop) , Korrelationsverfahren , metallographisches Untersuchen , Aufprallversuch , Verformung , Materialbruch
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