Deformation of Hemispherical-Nose VAR 4340 Steel Projectiles Striking 6061-T6511 Aluminum Targets at Oblique Angles
摘要
In this paper, we analyze the deformation of hemispherical-nose, 0.023 kg, 7.11 mm diameter, 71.12 mm long vacuum-arc-remelted (VAR) 4340 Rc 37, 39 and 45 steel projectiles striking 6061-T6511 aluminum targets over a range of angles of obliquity and striking velocities obtained from previous experiments and numerical simulations. For the experiments, the projectiles were launched using a 20 mm powder gun at striking velocities between 0.7 and 1.0 km/s into 254 mm diameter aluminum targets with angles of obliquity of 0°, 15° and 30°. The initial conditions obtained from the experiments were used to simulate the final configuration and permanent deformation of a projectile without erosion within the target. For the simulations, two different elastic-viscoplastic phenomenological constitutive models were used, one for the projectile and the other for the target. Both of the constitutive models accounted for compressibility, strain hardening, and strain rate sensitivity. The projectile deformation was modeled with an explicit transient solid dynamic finite element code, while the target was modeled with an analytical distributed load function derived from the dynamic expansion of a spherical cavity that included a finite boundary function (decay function) to represent a target’s free surface effect from the angle of obliquity. Results from the previous work illustrated the deformed final projectile positions and deformations were in good agreement with post-test radiographs from the experiments at the lower striking velocities; however, at the higher striking velocities, the projectiles in the simulations in several cases exhibited more bulging than those in the experiments. Therefore, in the present study, possible reasons for the differences observed between the experiments and simulations are investigated.