Dynamic Fracture and Fragmentation Characteristics of Metal Cylinder and Rings Subjected to Internal Explosive Loading

Abstract

Dynamic fracture and fragmentation characteristics of explosively driven rings and cylinders are important issues in the field of weapon effectiveness and protection. However, the comparison of fracture characteristics between metal cylinder and rings, and the fracture characteristics of the metal shells at different axial positions, are rarely touched. In the present work, a recovery tank was used to collect fragments, and witness plates were used to investigate the fragment spatial distributions. Before the test, the representative positions of metal shells were plated with copper layers to locate the original position of the recovered fragments. After the test, scanning electron microscopy and optical microscope were used for characterizing the microstructure of the recovered fragments from different positions. Then, the recovered fragments were weighed and measured to investigate their mass and size characteristics. In addition, numerical simulation was used to further investigate the fracture mechanisms of explosively driven cylinders and rings. It was found that the projection angle axial distribution of the fragments for the metal cylinder was similar to that of the fragments for the metal rings. However, the fracture characteristics of the metal rings were significantly different from those of the metal cylinder. The adiabatic shear band played a key role in the fracture process of the metal cylinder, whereas the adiabatic shear band had little chance to initiate in the fracture process of the metal rings because the metal rings could deform uniformly with much fewer strain localizations due to their much lower length. The fracture surfaces of the fragments from different positions of the metal cylinder were very smooth, whereas dimples were found in the fracture surfaces of the fragments from different positions of the metal rings. The mass distribution of the fragments from the metal rings was more uniform than that of the fragments from the metal cylinder, and the circumferential rupture strains of the metal rings were much larger than those of the metal cylinder.

Real-time simulation of a fragmenting explosion for cylindrical warheads

“…The experimental witness plates show a “random” group of fragment impacts. Figure 17 shows witness plates of fragment impacts from Arnold and Rottenkolber, 21 An et al, 24 and Swiderski et al 22 Although these witness plates indicate “random” fragment hits, the inserted lines, which “connect” three or more impacts, show that fragments hitting a target may be linked.…”

“…The simulation is also compared with experimental witness plates created by Arnold and Rottenkolber, 21 An et al, 24 and Swiderski et al 22 The witness plates are similar and there is an indication that fragment hits and the same angle of projection form a straight line. Delivering fragment impacts as craters rather than points and including small yaw angle rotations would enable the simulation to be more accurate.…”

“…This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. 21 An et al, 24 and Swiderski et al 22…”

The effect law of shell surface crack propagation under implosion loading

“…Table 5 shows the maximum principal tensile strain parameters of the three shell materials, where the failure strain values of 40CrMnSiB steel were measured by mechanical tests, and the maximum tensile failure strain values of 2024AL and OFHC copper were obtained from the literature [21] and [26] respectively, showing that there are significant differences in the ductility of the three materials. Studies of the fracture process of metal cylindrical shells under implosion loading have shown that the crack shape nucleation locations in the cylindrical shell space exhibit certain characteristics of random distribution [27,28], which is related to the inherent microdefects of the material itself. To describe the initial imperfection distribution of the shell material during the numerical simulation, the Mott random failure probability model [1] associated with shell fragmentation is introduced to define the variance of the unit failure strain such that each unit has a different failure strain.…”