New area rules for penetrating impactors

Area rules are established for a high-velocity normal penetration of a sharp and undeformable impactor into a ductile target under a condition of a localized impactor-target interaction. An impactor with a polygonal form of cross sections and a three-dimensional impactor of a close shape with the same distribution of the cross-sectional area along the longitudinal axis are considered. It is shown that under some additional requirements the difference in the ballistic limits of these two impactors is of the order of ε² where ε is of the order of the difference in their shapes. The established area rule is valid also for the drag force applied to flying projectiles under a wide range of conditions of high velocity flight.