Fragment Velocity Distribution of Controlled Fragmentation Warhead Under Eccentric Point Initiation

Abstract Three-Point eccentric initiation is one of the most common technologies of directional warhead for enhancing fragment lethality against targets. The fragment velocity distribution is a significant concern in warhead design. However, there is as yet no reasonable theory for predicting the fragment velocity distribution of a specific enhanced shell under three-point eccentric initiation; existing approaches are either limited to single or double-point eccentric initiation scenarios or ignore the effects of detonation gas leakage on fragment acceleration. In this paper, through theoretical analysis and numerical simulations, a new model was established to study the fragment velocity distribution of warhead shells under the combined effects of gas leakage and three-point eccentric initiation. Firstly, an equation for detonation velocity gain of explosives under three-point eccentric initiation was developed by numerical simulations, where the shells were set to be free from disintegration and gas leakage. Secondly, the fracture strain or radius of controlled fragmentation warhead was solved by the disintegration model established in our previous work. Then the equations for detonation velocity gain and the fracture strain were associated with a proposed gas-leakage equation in which the gas expansion was assumed to be locally isentropic. Finally, theoretical analysis was conducted by solving the associated equations. Grooved cylindrical shell was explosively expanded to disintegrate to verify the proposed model. Theoretical predictions of the fragment velocity distribution showed good agreement with experimental results, indicating that the model was suitable for predicting the fragment velocity distribution of an explosively-driven metal grooved cylinders under three-point eccentric initiation. Besides, this study provides an insight into the differences of fragment velocity enhancement among single point initiation, double point initiation and three point initiation.