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Creating better automotive components

July 22, 2002

Car manufacture uses a wide range of different materials. Among the metals, steels lead the way followed by aluminum and - to an increasing extent - magnesium. With the latter the argument of reduced weight and therefore lower fuel consumption is a very popular one. But the real issue is about availability and price, along with the production technologies favored by the industry. Magnesium offers the advantage that it can also be cast to make complex components with filigree structures. Less bolting, riveting and welding is required, which reduces the number of production steps. The ”Magnesium Lightweight Construction” industry-oriented strategic network reflects this with the example of a dashboard support, which is already being used on the new Opel Vectra and Vauxhall Vectra in the UK. Five Fraunhofer Institutes are pooling their know-how in order to achieve a leading position in this sector of technology.

As its designation would suggest, a dashboard support provides the mounting for all the displays and devices installed in the car’s instrument panel. It spans almost the entire width of the car, but is largely concealed by plastic lining. If a part like this is to be cast in magnesium, the diverse factors which it will encounter over its service life in the car must be carefully addressed during the development phase. Depending on the component and the application, factors requiring attention will include thermal expansion, corrosion, strength and crash behavior. These are not only examined on the actual component but are also studied by means of computer simulation. Owing to the length of the support and its proximity to the occupants, crash safety plays a major role. All the stresses that occur, the position of the bolt connections to the car body and the properties of the material are entered into the computer. It simulates the deformation of the component through to when and where it would eventually fracture. “It has to be borne in mind that its mechanical properties are not the same everywhere,” emphasizes Silke Sommer from the Fraunhofer Institute for Mechanics of Materials IWM. “They differ according to wall thickness and the parameters specified for casting.”

Real tests in which a heavy pendulum weight crashes against the component provide crucial information. Were the forecasts right or do the calculations need to be modified? Once the simulations have passed the test they can be applied to other parts. This leads to the speedier development of safer components and opens the way for the use of magnesium in car manufacture.

Fraunhofer-Gesellschaft