Research On Underwater Explosive Forming Projectile Based On Kinematic Stability And Penetration Performance

The underwater weapon warhead is an effective weapon to destroy the enemy’s surface and underwater targets.With the development of science and technology,the protective ability is several times as before.In view of the advantages of EFP in water,which can use cavitation effect to maintain low resistance,break through target melting and strength blockade,and have great effect after penetration and good damage effect,in-depth study of underwater EFP design is of great significance to improve target damage effect for the research and development of new and powerful warhead.On the basis of a large number of research on EFP technology in conventional air,in order to explore the difference between EFP forming and penetration performance in air and water,the EFP shaped warhead can achieve a good explosion forming configuration in water environment,and effectively damage the protective structure of typical underwater targets.For example,in view of the typical underwater protective structure with double shell and liquid layer,EFP can maintain good movement stability and penetration performance through the liquid layer to damage the interior of the target.In this paper,the following aspects of the design and exploration of the underwater EFP warhead are carried out.Combined with the formation theory of EFP,the key factors affecting the formation characteristics of EFP and the influencing laws are analyzed.According to the design requirements of EFP in water medium,the influence of water medium on the theoretical model of the initial collapse velocity of the cover micro element is analyzed.On this basis,combined with the design thinking and process of conventional EFP shaped warhead in air,the design thinking of EFP in water medium environment is correspondingly considered and analyzed.The results show that the thickness of the liner is the key factor affecting the formation characteristics of EFP.The larger the wall thickness is,the smaller the crushing speed of the micro element is,and the smaller the ratio of length to diameter of EFP is.The formation of EFP in water medium will gradually be affected by the viscous resistance of water from the edge along the bus to the axis,so the crushing speed difference of the micro element along the bus will be larger than that in air,which will lead to the formation of EFP.In this paper,the theoretical analysis is used to guide the numerical simulation to complete the preliminary design work,on the basis of which,the follow-up test can be more accurate.Based on the motion stability,four kinds of EFP(Backward-Folding,long rod,ForwardFolding and Radial Collapse)in air and underwater forming characteristics were compared and numerical experiments were carried out based on the motion stability the results of theoretical model analysis;Based on the penetration performance,four factors(blast height,radius of curvature,liner thickness,shell thickness)numerical simulation experiments were carried out for the Backward-Folding EFP.The effects of forming factors on the formation and penetration characteristics of EFP in water are obtained.The results show : Consistent with the theoretical analysis.Under the same charge condition,the kinetic energy obtained by Backward-Folding EFP,long rod EFP,Forward-Folding EFP and Radial Collapse EFP increases,corresponding to the increase of 26.7%,20.0%,10.0% and 66.7% of the wall thickness required for good formation in water,and then the EFP structure with similar characteristics can be obtained by adjusting the curvature radius of the liner.The influencing factors of EFP’s penetration performance after entering the water for 10 cm are listed from the main to the secondary order:the air blast height,the curvature radius,the liner thickness,the shell thickness.Finally,the spherical shaped charge with backward flip forming mode is selected for the EFP shaped warhead in water.The forming parameters of EFP shaped warhead in water are finally determined: H = 45 mm,r = 21.2mm,δ = 2.5mm,d = 1.2mm.Finally,the numerical simulation of the process of the underwater EFP warhead damaging the typical double shell protective structure is carried out,and the penetration characteristics of the double shell structure are obtained.The simulation results show : The designed EFP warhead can effectively damage the small underwater target with double shell protective structure.The mass loss of the EFP begins to occur at about 120 mm of the penetration into the water,and the damage ability decreases greatly.The mass loss begins to become severe at about170 mm of the penetration into the water,reaching the damage ability limit.The feasibility of the underwater EFP warhead designed in this paper is verified.