Experimental and numerical study on the ballistic impact behavior of 6061-T651 aluminum alloy thick plates against blunt-nosed projectiles

To reveal the effect and necessity of introducing the Lode angle into a fracture criterion in ballistic performance simulations of metallic Plates, experimental and numerical work were carried out on 6061-T651 aluminum alloy (AA6061-T651) thick Plates. Firstly, a series of ballistic tests were conducted via a one-stage gas gun test facility that blunt-nosed projectiles of phi 12.68 mm penetrated onto 20 mm thick AA6061-T651 Plates at impact velocities ranging from 280.0 m/s to 400.0 m/s. Subsequently, experimental results in terms of initial versus residual velocities of the projectiles and the failure characteristics of the Plates were reported. Experimental results showed that shear plugging was the dominating failure mode of the perforated Plates. Meanwhile, numerical results corresponding to the ballistic tests were obtained using finite element (FE) simulations via the commercial software ABAQUS/Explicit. Specially, we compared the results between simulations using a Lode dependent fracture criterion and a Lode independent. Finally, the FE simulations indicated that using a Lode dependent fracture criterion better predicts the ballistic behavior of the thick AA6061-T651 Plates under impact of blunt-nosed projectiles. It is also found that the Lode angle affects the fracture behaviour of the AA6061-T651 significantly. And this effect decreases with the increase of the materials' ductility.