An experimental–numerical investigation on aluminium tubes subjected to ballistic impact with soft core 7.62 ball projectiles

An experimental–numerical investigation of the ballistic impact of 7.62×51 mm soft-core ball 9.5 g projectiles on aluminium tubes is presented in this paper. The tubes are made of Al-6061-T6 and simulate actual components of a helicopter tail rotor drive shaft. Several tests have been carried out: a real gun has been used to produce ordnance velocities and a dedicated support frame has been built to perform impact tests with an angle of obliquity (in order to reproduce the most critical damage on the component that is subjected to torsional service load). Initial and residual velocity of the bullets, shape and dimensions of the damage, and the residual stresses on the components, have been measured. cal models of the impact have been developed with the commercial Finite Element code ABAQUS/Explicit. The Johnson–Cook (JC) constitutive model and the Bao–Wierzbicki (BW) ductile fracture criterion have been calibrated for Al-6061-T6 and have been used for the analyses. The effect of the bullet type on the damage has been investigated; therefore the ball bullet has been fully modelled (core and jacket) to highlight the effect and danger of this type of soft core bullet in case of impact against aluminium thin structures. Numerical models are in good agreement with the experimental results; more specifically they show a satisfactory capability to reproduce the residual velocity of the bullets and the failure mode, as well as the residual stress fields on the tubes near the damaged zone.