Long Tubular Penetration Models.

Abstract : The penetration mechanics of a thick walled tubular penetrator is examined as ratio of the outer to inner diameter is increased from values of 0.4 to 0.74. Since the craters are characterized by depth and radius, analytical models for the crater radius due to tubular penetrators are developed. A two stage cavity expansion model is provided, which is based on the observations that in the first stage, the eroded penetration element exerts pressure on the target and opens a cavity. In the second stage, the inertia imparted to the target is responsible for the further expansion of the cavity. The analysis includes the centrifugal force exerted by the penetrator, radial inertia of the target, and the strength of the target. The crater radius is also determined from the energy and momentum principles and the results are compared with other results. The results obtained from the momentum principle provide good agreement with the other models in spite of its simplicity. The penetration velocity for tubes, which is less than that of rods, thus cannot be obtained from the modified hydrodynamic theory, is determined from computer simulations on behalf of the penetration efficiency. Numerical simulations using AUTODYN-2D are conducted for comparison with the analytical predictions and these confirm the phenomenological assumptions in the models.