Tip Failure and Residual Velocity in Impact of Hollow Al-6061 T6 Projectiles on Thin Al-6061 T6 Plates

Hollow Al-6061 T6 cylinders weighing 11 g, after being accelerated through a four-stage electromagnetic launcher at upto 434 m/s, impact on 3 mm thick Al-6061 T6 plates. Plate perforation occurs at 367 m/s and residual velocity of the projectiles is obtained. Post-impact, the projectiles fail by ejection of tip as a thin ring. Simulations are carried out using Smooth Particle Hydrodynamics technique using either Bao-Wierzbicki or a recent parameterization of the Johnson-Cook failure model for Al-6061 T6. Trend in the residual velocities is insensitive to the failure model employed. Tip failure is reproduced in both failure models. Thus, the tip failure in the hollow AL-6061 T6 projectiles is adequately explained as an instance of ductile failure. The target plates fail by petalling which is reproduced in the simulations as well.