On the Fragmentation of Explosively-driven Plastic/steel Layered Cylinders

Abstract

While over the past century fairly extensive work has been carried out on explosively-driven metallic envelope fragmentation, as the development of explosive materials and warhead configurations continued, the issue under consideration is still topical. The current paper aims to investigate the fragmentation characteristics of explosively-driven steel cylinders when double layer envelopes are used. Mott�s approach was modified in order to account for such particular configuration (layered envelope). Several tests in a simplified type procedure were performed aiming to confirm the theoretical approach.

The Application of Mott’s Distribution in the Fragmentation of Steel Coaxial Cylinders

“…for such configurations, based on the approach proposed by Rotariu [15]. The resulting distribution represents a combination of classical Mott distributions in which the cumulative number of fragments is related to the second-order radical of the fragment mass.…”

“…The materials were chosen from the material database of AUTODYN [28]. For the Lagrange parts, the effective plastic strain equal to 1 was established as the failure criterion, with the option of a stochastic variance of 16, a minimum fail fraction of 0.9 and a random seed, values used in a previous study [29]. The Euler part was meshed by a network of nodes defining 0.5 × 0.5 mm square finite elements.…”

“…To evaluate how the existence of two or more coaxial cylinders influences the fragmentation when a centrally placed explosive charge detonates, the following configuration inspired from a real configuration used in experiments [15] was imagined: a central charge made of RDX with a diameter of 37 mm and a length of 65 mm, which is encapsulated in a steel case of the same length, and with a total wall thickness of 14 mm. In addition to the variant in which the metal case is made from a single body, five other variants were taken into account, three with two cylinders and two with three coaxial cylinders; see Figure 10.…”

“…In a more recent theoretical and experimental research [15], the fragmentation of a metal cylinder was studied for a setup configuration in which the metal is not in direct contact with the explosive charge, with an inert layer being used to separate them. Starting from the approach proposed by Mott, a modified formula was deduced for the characteristic mass µ.…”

“…Even if the subject of natural fragmentation has been extensively analyzed by numerous researchers, there are no studies dedicated to the derivation of specific formulas for multilayer structures like two or more coaxial metallic cylinders. The present research represents a theoretical study dedicated to the calculation of the natural fragmentation for such configurations, based on the approach proposed by Rotariu [15]. The resulting distribution represents a combination of classical Mott distributions in which the cumulative number of fragments is related to the second-order radical of the fragment mass.…”