Streamline reversal in hypervelocity penetration

We report a direct observation of the "streamline" reversal of eroded rod m aterial proposed by Alien and Rogers in 1961 [1]. Alien and Rogers suggeste d that the "turning" of high velocity long-rod penetrator material at the t arget interface could be viewed as a reversal of the direction of a "stream line" with only a change of sign in the velocity. Alien and Rogers' streaml ine reversal model has two important consequences. First, the eroded debris has a speed of v(d) = 2u - v relative to the target, where v is the impact velocity and u is the speed of penetration of the rod relative to the targ et. Secondly, a consequence of v(d) = 2u - v is that the length of the rod debris, l(d), is given by the difference in the initial length of the rod, l(o), and the remaining length of the rod, l, i.e., l(d) = l(o) - l. Result s of a time-resolved experiment for a tungsten penetrator into a polycarbon ate target at 3.61 km/s and a corresponding numerical simulation are consis tent with streamline reversal. Numerical simulations are then used in a par ametric study to investigate the effects of various density ratios between penetrator and target materials, (C) 1999 Elsevier Science Ltd. All rights reserved.