13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Low velocity perforation of an aluminum alloy: experiments and simulations Léonard Antoinat1,*, Régis Kubler1, Guillaume Achard1, Jean-Luc Barou2, Philippe Viot2, Laurent Barrallier1 1 MSMP, Arts et Métiers ParisTech, 13617 Aix en Provence, France 2 Arts et Métiers ParisTech, I2M, UMR 5295, 33405 Talence, France * Corresponding author: leonard.antoinat@ensam.eu Abstract Low velocity perforation of an aeronautical aluminum alloy sheet 2024 T3 subjected to impact is studied in this paper. The main objective is to compare experimental results and simulations by analysis of the failure. The perforation test is made with an instrumented 3 meter drop test. The striker has a large diameter (45 mm) and a conical shape. Sheets’ thickness is 2 mm. The influence of the impact velocity is analyzed. A phenomenological behavior law of the sheet’s material is implemented in the finite element code Abaqus/Explicit. Thus, 3D simulations of perforation are performed using a damage evolution law and a ductile failure criterion. To understand the phenomenon, the perforation force and the sticker velocity will be analyzed. Simulations are validated by experimental tests and compared with an analytical model. Keywords Dynamic perforation, Aluminum, Experiments, FE Simulations, Analytical perforation model 1. Introduction An increased attention in impact issues is paid by authors working on various engineering fields like aeronautic [1], naval [2], and automotive [3]. Impact on ductile material involves high strain rates effects [4] and temperature effects [5]. Thus, the knowledge of material dynamic behavior is necessary. Particular constitutive laws are known to be adapted for this type of issue [6]. The ductile target perforation is a specific case of impact studies. Perforation tests can be classified in categories according to the test velocity is high [7] or low [8], or according to the different striker's geometries (diameter, nose shape,…). An energetic approach is recommended to understand perforation issue. The energy absorbed by the target during impact Ea can be calculated using the difference between the initial kinetic energy and the final kinetic energy [8]. The ballistic limit Vbl is known to be the minimal initial velocity involving perforation. In order to have a better understanding of the rupture phenomenon and in order to compare with simulation results, it is necessary to know the force applied to the target and/or the striker displacement, during impact. This is the reason why some authors use the Hopkinson bar theory [9] [10] or an instrumented pneumatic accelerator or drop test [9] to be able to plot the curve of the force versus the time and/or the displacement. Low velocity perforation of an aeronautical aluminum alloy sheet 2024 T3 subjected to impact is studied in this paper. Unlike Rodriguez-Martinez [8] who studied the perforation of thin target (1 mm), the idea is here to work with thicker plates (2 mm) and with a larger striker (45 mm). A two-pronged approach for perforation is proposed here: an experimental approach with the use of a drop test and a modeling approach including a finite element (FE) approach and an analytical approach. Results are compared and discussed.
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