On the fracture of aluminum plates perforated by rigid flat-nosed projectiles

We present a series of 2D numerical simulations for the perforation process of aluminum plates impacted by rigid steel cylinders. The simulations accounted for the residual velocities of these projectiles as a function of their impact velocities, as obtained recently by several workers. The aluminum plates in these works were made of the quasi-brittle 2024-T351 and 7075-T651 alloys, and the more ductile 6061-T651 alloy. The material properties of these alloys, for their strength and failure parameters, were taken from published works. We find that the ductility/brittleness property of these alloys is related to the different values of their corresponding strains to failure at shear states. Our simulations for the two quasi-brittle alloys resulted in good agreement with the measured data. On the other hand, the simulations for the 6061-T651 alloy agreed with the corresponding data only when we used a relatively low value of the Taylor-Quinney coefficient for this alloy. We also highlight various problems with the issue of mesh sensitivity in simulating the perforation of metallic plates by rigid cylinders. Particularly, we found that these simulations do not converge to definite values for the residual velocities even when the mesh size is reduced to 0.025 mm. Moreover, we found that the experimental data for the residual velocities can be accounted for by different failure curves, depending on the mesh size of the simulation. Thus, a given failure criterion cannot be validated by such simulations.