Prediction of Primary Fragmentation Characteristics of Cased Munitions

摘要

Safety to the public and nearby operational personnel during unexploded ordnance (UXO) operations is of the utmost importance. An accidental explosion produces hazards from primary fragments, blast overpressure, ground shock, and noise. The effects used to determine withdrawal distances for UXO operations are predominantly blast overpressure and primary fragmentation. For most ordnance the fragmentation range is much larger than the inhabited building distance (IBD) for blast overpressure. In order to determine the withdrawal distance for primary fragmentation, the fragmentation characteristics of the munition must be determined. The Structural Branch of the U.S. Army Engineering and Support Center, Huntsville (USAESCH) uses methods described in TM 5-1300, 'Structures to Resist the Effects of Accidental Explosions' to determine the fragmentation characteristics of cased, cylindrical munitions. These characteristics include initial fragment velocity, weight of the largest fragment, average fragment weight, the total number of fragments, and the fragment weight for a given confidence level. These methods are applicable only for primary fragments resulting from a high-order detonation of a cylindrical casing with evenly distributed explosives in direct contact with the casing. For casings that are not uniform in thickness or diameter along the entire length, the casing must be modeled using a series of equivalent cylinders. The method is a trial-and-error procedure involving iterating on geometry to match the total modeled explosive weight to the actual explosive weight. These calculated fragmentation characteristics are used for a wide variety of purposes such as fragment range, striking energy, areal debris density and fragment penetration. The calculation methods, some modeling tips, and an example are presented.