Optimization of biaxial tensile specimen shape from numerical investigations
Résumé
In innovative industrial processes such as hydroforming or incremental forming, strain rates up to 500s-1 can be reached. As a result, experimental setups allowing to obtain large deformations from static to intermediate strain rate levels have to be developed to predict the formability limits of sheet metal materials. The proposed experimental device is a servo-hydraulic testing machine provided with four independent dynamic actuators allowing biaxial tensile tests on cruciform specimen. The main difficulty to define an appropriate cruciform specimen shape is to force the onset of necking in the central region. In this paper, different specimens used in previous studies are numerically investigated through FE simulations. A modified cruciform specimen shape is then proposed and the best set of geometrical dimensions is defined from a parametric study. Finally, the efficiency of the proposed specimen shape is validated by experiments. Numerical and experimental results, i.e., the strain level in the specimen and the onset of necking are compared and discussed to boundary conditions corresponding to an equi-biaxial tensile test.
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