13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- 4.6 m/s and 4.5 m/s for respectively 4, 5 and 6 petals. This tendency is not confirmed by drop tests’ results (Table. 2). 5. Conclusion and remarks Thin sheets of 2024 AA were perforated, on a drop test, by a 60° and 45 mm diameter conical striker for a range of velocity from 2.7 m/s to 6.9 m/s. The energy needed to perforate is about 160 J. Four or more than four petals always appear in the sheet during perforation. A numerical model and an analytical model were proposed. Shell element model coupled with Johnson Cook viscoplastic and damage laws is adapted to simulate the perforation of thin sheet of aluminum alloy. The ballistic limit velocity, the residual velocity as well as the impact are in good agreement with experimental data. It can be shown that simulated force during impact is below the experimental force. The analytical model also predicts the residual velocity. Simulations using an anisotropic material model for rolled sheets are underway and predict petals’ formation during perforation (Fig. 8). Future analysis of pictures taken by high speed camera, beneath the sheet, will permit to perform image correlation for strain measurements in order to correlate the simulated strain field and the experimental strain field and therefore to better analyze the crack propagation (fracture criterion). Figure 8. Simulation versus experiment for an initial velocity of 6.9 m/s using an anisotropic material model. Acknowledgements The financial support of this work from OSEO, a structure for the benefit of SMEs and innovation, is gratefully acknowledged. References [1] K. E. Jackson, R. L. Boitnott, E. L. Fasanella, L. E. Jones and K. H. Lyle, A History of Full-Scale Aircraft and Rotorcraft Crash Testing and Simulation at NASA Langley Research Center, 4th Triennial International Aircraft and Cabin Safety Research Conference, 2004. [2] A. Tassin, Modélisation tridimensionnelle d’impacts hydrodynamiques pour l´étude du tossage des bulbes d´étrave., 2010.
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