FRAGMENTATION OF HE PROJECTILE CASINGS: FRAGMENT MASS DISTRIBUTION LAWS AND PHYSICS BASED FRAGMENTATION MODELS

Predrag Elek,

Slobodan Jaramaz,

Dejan Micković

Apstrakt:

Subject of the present research is modeling of fragmentation of HE warheads casings, as the phenomenon of the utmost importance for fragmentation warheads design and efficiency analysis. Therefore, central objectives of the research are: (i) formulation the physical relations that enable determination of the characteristic fragment size and mass, and (ii) determination of the fragment mass distribution law.

In the first chapter, definitions of the basic concepts are given, the key characteristics of the dynamic fragmentation processes are indicated, and different approaches to the fragmentation modeling are reviewed.

In chapter two, empirical laws of fragment size and mass distribution have been considered. Random fragmentation of a space applying geometric statistics is analyzed first. The relevant empirical laws of fragment mass distribution are also analyzed: the generalized Mott law, the generalized Grady-Kipp distribution, the lognormal, the Weibull, and the Held distribution. The criteria for comparison of different theoretical distributions are established based on the optimization of the free parameters in analyzed models and computation of the adjusted coefficient of determination. Statistical analysis of these criteria on the available database of 30 experimental results of HE projectiles fragmentation has shown that three-parametric generalized Grady-Kipp distribution provides the best description of experimental data. This model is suggested for prediction of HE projectiles fragment mass distribution.

Physically based fragmentation models are the subject of analysis in chapter three. The Mott's one-dimensional fragmentation of the ring (cylinder) model is thoroughly analyzed first. Then, the analytical approach to this model is considered and energy-based constrains of the model has been introduced. The generalization of merged model is formulated for the cases of 2D and 3D fragmentation. Also, the Grady's pure energetic model has been considered as well as the important modification of Glenn-Chudnovsky. The analyzed models enable prediction of the characteristic size and mass of generated fragments.

Key words: projectile, high explosive projectiles, projectile fragmentation, casings, fragmentation effect, mass distribution law, statistical analysis.