Hard projectile penetration and trajectory stability

Abstract

Abstract:We present a general framework to describe the dynamics of a hard projectile penetrating into a solid target. Rigid-body dynamics, differential area force law and semi-empirical resistance function are used to formulate the motion of the hard projectile. The proposed model is capable of predicting the projectile trajectory under various oblique and yaw angles. Critical conditions for the occurrences of the instability and the reverse of the projectile trajectory are discussed. It was found that the relative location of mass centre of the projectile has strong influence on the control of the rotation of the projectile, and thus, the projectile stability and the change of trajectory direction. The validity of the proposed model is limited to deep penetration and when the wake separation and reattachment between projectile body and target have negligible influence on the target resistance to the projectile.

Trajectory instability and convergence of the curvilinear motion of a hard projectile in deep penetration

“…Experimental results in [20] indicated the trajectory convergence, i.e. the projectile trajectory gradually becomes straight after a curvilinear motion in target medium, which has also been observed in [17]. However, this phenomenon was neglected in further studies.…”

“…[17][18][19][20][21]) based on DAFL approach and semi-empirical resistance function. It has been found that the projectile trajectory may change abruptly around a critical impact velocity, which was considered as a trajectory instability problem [17]. Experimental results in [20] indicated the trajectory convergence, i.e.…”

“…Curvilinear motion and instability of projectile trajectory were discussed in [17] as two different problems, in which the trajectory instability was described based on the conventional instability concept by introducing non-axisymmetrical disturbances and imperfections. In a conventional instability problem (e.g.…”

“…However, it has been found that the critical impact velocity for the occurrence of projectile instability depends on the non-axisymmetrical disturbances no matter how small they are. For example, it was shown in Fig.15 of [17] that the critical impact velocity for the trajectory instability depends on the initial disturbance of the attack angle, i.e. the critical impact velocity continuously increases with the decrease of initial attack angle without a clear finite asymptote limit when the initial attack angle approaches to zero.…”

“…(c) Geometry and mass distribution of the projectile: It was found in [17] that the relative location of mass centre of the projectile has strong influence on the rotation of the projectile, and thus, on the projectile stability and the curvilinear motion. 3.…”