Controlled tumbling of projectiles—I. Theoretical model

Abstract

The present investigation is concerned with the generation of controlled tumbling of a blunt-nosed hard-steel projectile and, to some extent, the effect of this tumbling on targets struck subsequently. The mechanism for producing this motion from an initial state of translation in the direction of the projectile axis consisted of the impingement of the bullet on the edge of deflector plates of aluminum, steel or plastic of various thicknesses with various degrees of overlap. These initially plane rectangular plates were rigidly held on three sides and struck at the center of the fourth, or free, edge. This first portion of the study consists of the continuum-mechanical analysis of the impact of the projectile on the plate and the subsequent motion of the projectile. A mode shape analysis is employed to ascertain the deplection of the plate with the impact area modeled as a hexagon. The projection is considered as rigid and its motion as planar prior and subsequent to the impact with the deflector plate, which is modeled as a rigid-perfectly plastic material. The numerical predictions of the theoretical development, the experimental set-up and the data derived from the tests, as well as a comparison between the analytical and measured values, are presented in a companion paper [Ruiz and Goldsmith, Int. J. Impact Engng Vol. 7, in press (1988)].