科研之友
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摘要
Modern automotive bodies are made of high and ultra high strength steel up to 90 mass percent of the body in white. These steels do not only possess a high light weight potential but also increase crash performance of the passenger cabin. The described benefits are facing the problems of forming these steels. With a low formability at room temperature and high flow stresses the complexity of parts out of these materials is limited. In a warm forming process with temperatures up to 600 degrees C the formability could be increased and the process forces could be decreased. Especially high complex parts are produced by hydroforming a technology allowing undercuts and uniform strain distributions in the part. For temperatures up to 600 degrees C there is a need of an appropriate medium for hydroforming. Fluids normally used at room temperature are only temperature stable up to about 350 degrees C and tend like gases to leakage. Using a granular material like small ceramic beads allow high temperatures and reduce the risk of leakage. The Drucker-Prager-Cap material model allows to describe this medium for the numerical simulation. The accuracy of the numerical simulation with the gained material model is compared with different experiments in which the parameters were identified and a real part geometry of a cup formed with granular material as medium.
- 出版日期2010-4
