Study On Penetration And Fragmentation Of Penetrator With Enhanced Lateral Effect

The penetrator with enhanced lateral efficiency(PELE)is made of an outer jacket of high-density material and an inner filling of low-density material.As a new concept ammunition,PELE has no high explosives inside.When a PELE perforates a thin metallic plate,the axial compressing energy accumulated in the penetration process,can turn into radial expansion energy due to the Poisson effect.Compared with a conventional penetrator,PELE penetrators show larger lateral damaging efficiency because its jacket can turn into fragments with very high radial velocities.The fragment forming mechanism of PELE is very complicated,and the interactions of the inner fillings,the outer jacket and the target plate have to be considered.In the whole process of PELE penetration and perforation,the kinetic energy of the scattering fragments mainly comes from the energy accumulated by the axial shock wave.However,the magnitude of the axial shock wave is affected by many factors,such as the initial conditions,the material properties of penetrator and the target plate,and the thickness of the target plate.The research on projectile penetration and fragmentation mechanism can provide a theoretical basis for the design and performance improvement of the ammunition.In this paper,the theoretical analysis,experimental research and numerical simulation method of the PELE projectile penetration and the shell of the broken mechanism and influencing factors were studied.The main contents include several aspects as follows(1)By using the shock wave theory,the process that penetrator with enhanced lateral efficiency(PELE)penetrated a thin metal target was analyzed.The energy loss of the PELE in the process of penetrating the target plate can be divided into three parts: the energy obtained by plug when jacket and filling impact the target,the increased internal energy of jacket and filling,and the shear energy dissipated in the outer and inner edge on the front end of jacket in the process of penetrating the target.Based on the principle of conservation of energy and the method to determine these energies,the approximate formula of the axial residual velocity of PELE was presented.With this formula,we could calculate the axial residual velocity and the calculated results were in good agreement with the experimental data.Comparison the energy loss in the different conditions showed that the filling material has little effect on projectile penetrating ability,and the energy that the plug obtained was largest while the shear dissipated energy can be neglected.(2)According to the theory of Mott-Grady fragmentation and the hypothesis of the expansion process of PELE projectile shell,the theoretical analysis method of the distribution range of fragments scale is given.The correctness of the theoretical analysis is tested by experiments.By theoretical analysis and experimental study,projectile shell fragment size distribution is mainly affected by material density,crushing energy consumption,critical fracture strain and strain rate.The fragments width and number are greatly influenced by inner core material.With the increasing of density and elastic modulus of the inner core material the width of front-end fragment decreases the number increase,the radial velocity becomes large.The shell fragment length is determined by projectile impacting target speed and less affected by the inner core material.(3)In the process of a PELE penetrator penetrating into a metallic thin plate,the deformation of the front part of PELE can be simplified into two phases: One-dimensional axial compression during penetration and radial free expansion during complete perforation.According to shock wave theory,it can be assumed that the kinetic energy of a PELE penetrator accumulates as compression energy in the first phase and is then completely released as the kinetic energy of fragments in the second phase.With this assumption,the scattering radial velocity of fragments after a PELE penetrator perforates a thin plate can be calculated.A comparison of experimental data for radial velocities obtained from various impact conditions with date calculated using the model presented here was consistent.Further analysis shows that the maximum radial velocity of fragments is tightly correlated with the bulk modulus and the Poisson’s ratio of both the jacket and the filling of the PELE penetrator,and increase with an increase in both.For the same impact velocity,the radial velocities of the scattered fragments increase with increase of both the thickness and the shock impedance of the target plate.In addition,a model for calculating the axial velocity of the projectile penetrating the thick target is given.(4)Based on numerical simulation software,simulation algorithm,material model,model participation,grid and erosion strain selection,a numerical simulation method for PELE projectile penetration and shell crushing is given.Through experiment and numerical simulation data analysis,the relationship between axial velocity,radial velocity,rupture length of the projectile fragments and the projectile and target materials,the position of the shell body bottom,body inside and outside diameter ratio,is given.