Compressible models of shaped charge jet in water

Abstract: Shaped charge jet penetration belongs to hypervelocity penetration, and compressibility of projectile/target material should be considered in the process of penetration. Water has similar compressibility as polymer solid materials (such as Plexiglas and PMMA) and it also belongs to high compressibility materials. Therefore, compressibility should be considered when studying jet into water. Referring to the general compressible solid model, we derived a special complete compressible model regarding to the special case of jet into water in this paper. Meanwhile, we derived an approximate model according to Mie-Grüneisen EOS which were much easy to calculate. In order to solve the shortcomings of complex constructor function and implicit solution of stagnation pressure in approximation model of Mie-Grüneisen EOS, we also derived an approximation model based on Murnaghan EOS. Then, we substituted the relationship between jet velocity and penetration velocity of three models into virtual origin model and studied the influence of water compressibility on penetration efficiency. We also compared these models with experiment, and we found that although the approximate model based on Murnaghan EOS had some errors compared with complete model, its predictability was still good. So, we could conclude that jet penetrating water had similar penetration efficiency with jet penetrating high compressible polymer solid materials. Therein we could expand the scope of compressible model, and we also found that jet head velocity and penetration speed were the main affecting factors of stagnation pressure.