Influence of Stress State on the Mechanical Impact and Deformation Behaviors of Aluminum Alloys

Abstract

Under impact loading conditions, the stress state derived from the contact between the projectile and the target, as well as from the subsequent mechanical waves, is a variable of great interest. The geometry of the projectile plays a dertermining role in the resulting stress state in the targeted structure. In this regard, different stress states lead to different failure modes. In this work, we analyze the influence of the stress state on the deformation and failure behaviors of three aluminum alloys that are commonly used in the aeronautical, naval, and automotive industries. To this purpose, tension-torsion tests are performed covering a wide range of stress triaxialities and Lode parameters. Secondly, the observations from these static tests are compared to failure mode of the same materials at high impact velocities tests with the aim of analysing the role of stress state and strain rate in the mechanical response of the aluminum plates. Experimental impacts are conducted with different projectile geometries to allow for the analysis of stress states influence. In addition, these experiments are simulated by using finite element models to evaluate the predictive capability of three failure criteria: critical plastic deformation, Johnson-Cook, and Bai-Wierzbicki.

A new Dynamic Plasticity and Failure Model for Metals

“…Figure 23 shows the comparison of the numerically predicted perforation mode with the experimental observation for the 4 mm thick 2024-T351 aluminum plate struck by the flat-ended projectile. It is clear from Figure 23a that the final perforation pattern predicted by the present model is in good agreement with the experimentally observed shear plug failure as shown in Figure 23b [53]. The radius of the plug sheared out from the plate is virtually the same as that of the projectile.…”

“…The usefulness and the accuracy of the present new plasticity and failure model are also verified against the test data for the perforation of 2024-T351 aluminum alloy plates struck transversely by flat-ended and spherical projectiles, as examined by Rodriguez-Millan et al [53]. For the sake of comparison, the numerical results with the JC constitutive model together with the JC failure criterion or the BW fracture criterion as reported by Rodriguez-Millan et al [53] are also presented and discussed.…”

“…Figure 21 shows the finite element model used in the numerical simulations. Figure 22 shows the comparison of the numerically predicted residual velocities with the experimental data for the perforation of the 2024-T351 aluminum alloys plates struck by the flat-faced projectile at normal incidence [53]. It is clear from Figure 22 that that residual velocities predicted by the present model are generally in good agreement with the test data.…”

“…Moreover, the ballistic limit velocity predicted by the present model is in good agreement with the experimental observation (300 m/s) while the ballistic limit velocities predicted from the JC constitutive model together with the JC failure criterion or the BW fracture criterion are much lower than the experimental value as can be seen from Figure 22. Figure 22 shows the comparison of the numerically predicted residual velocities with the experimental data for the perforation of the 2024-T351 aluminum alloys plates struck by the flat-faced projectile at normal incidence [53]. It is clear from Figure 22 that that residual velocities predicted by the present model are generally in good agreement with the test data.…”

“…Due to symmetry boundary conditions in the X-Z plane and Y-Z plane, only a quarter of the bar specimen is modeled, to save computing time. The values of various parameters employed in the JC constitutive model and the JC failure criterion and BW fracture model were obtained by Rodriguez-Millan et al [53] for 2024-T351 aluminum. The values of various parameters used in the present plasticity and failure model for 2024-T351 aluminum are listed in Table 1.…”