In order to obtain the dispersion rule of fragments about the asymmetric shell subjected to internal blast loading, two different cross section structures, concave-shaped and convex-shaped, were carried out by experimental and numerical methods. The simulation results well coincided with the experimental results, and the spatial distribution and fragment velocity were obtained. The optimal curvatures for the different concave structures changed from 4r to 6r (r represents the charge radius), as the central angle of concave structure changed from 90° to 120°. However, the optimal curvature changed weakly when the central angle of concave structure was larger than 120°. In addition, a formula which can rapidly predict the projection angle range was fitted for the convex structure. The conclusions can provide a reference for concave-shaped and convex-shaped structures to achieve a higher effectiveness of fragments.

The deformable warhead is a common type of anti-missile warheads, and the geometric configuration of deformable warhead is close to D shape under the lateral blast loading of auxiliary charge. In this article, the spatial distribution of fragments is taken as the research object, and an empirical model for evaluating the spatial distribution of fragments is expected to be established. First, the empirical model was designed based on dimensional analysis and quadratic interpolation. Then, three different D-shaped structures (D-90°, D-120°, D-150°) were studied by the numerical simulations and experiments. In order to minimize the influence of the axial sparse waves at both ends, only the middlemost layer of fragments was researched. The relationships among d/r, sin a, and sin b were obtained (where d represents the initiation distance, a represents the initial position angle, and b represents the scattering angle). With the scattering angle b and target distance l, the spatial distribution of fragments can be deduced. Based on the fitting formula and the parameters of D-shaped structures, the relationships between d/r, sin a, and sin b of arbitrary D-shaped casing (D-u) were obtained using quadratic interpolation. Finally, D-105°structure was verified by numerical simulation and empirical formula, both of which coincided well with each other. Therefore, the empirical model can be used to rapidly evaluate the spatial distribution of fragments, especially suitable for the D-shaped structure with a large length-diameter ratio.

An experimental investigation on deformation shape of a cylindrical shell with internal medium subjected to lateral contact explosion was carried out briefly. Deformation shapes at different covered width of lateral explosive were recovered experimentally. Based on the experimental results, a corresponding analytical approach has been undertaken with rigid plastic hinge theory. In the analytical model, the cylindrical shell is divided into end-to-end rigid square bars. Deformation process of the cylindrical shell is described by using the translations and rotations of all rigid square bars. Expressions of the spring force, buckling moment, and deflection angle between adjacent rigid square bars are conducted theoretically. Given the structure parameters of the cylinder and the type of the lateral explosive charge, deformation processes and shapes are reported and discussed using the analytical approach. A good agreement has been obtained between calculated and experimental results, and thus the analytical approach can be considered as a valuable tool in understanding the deformation mechanism and predicting the deformation shapes of the cylindrical shell with internal medium subjected to lateral contact explosion. Finally, parametric studies are carried out to analyze the effects of deformation shape, including the covered width of the lateral explosive, explosive charge material, and distribution of initial velocity.

Abstract:The energy output characteristic of an asymmetric cylindrical structure under internal explosion loading has significant research value in the field of the national defense industry. This paper took the D-shaped structure as the research object. Three groups of experiments (D-90 • , D-120 • , D-150 • ) were carried out. The D-shaped structure showed that fragments are concentrated in the middle and are sparse on both sides. Moreover, the fragment density decreased with the increase of the azimuth angle. The fragment velocities, which were measured from high-speed photography and an oscilloscope, coincided well with each other, and decreased with an increase in the central angle. Compared with the cylindrical structure, the fragment energy gain of the D-shaped structure is significant; the total energy and energy density of the three D-shaped structures were very close to each other. This indicates that D-120 • is the optimal solution among the three D-shaped structures and it can provide guidance for the future design of D-shaped structures to achieve higher energy output.