Technology Research On The Formation Of Explosively Formed Projectile Warheand With Wave Shaper

In the team of anti-armor ammunitions which attacking cluster tank at a long rang, terminal sensitive projectile is the highest cost-effectiveness one. The explosively formed projectile (EFP) is one of the key technologies in terminal sensitive projectile system. A mountain of research and development work in the area of EFP technology has been carried out in recent decades, however, with the development of new armor technology, designing more powerful EFP, which has high initial velocity, large length-diameter ratio,and high flight stability, is a major issue to be addressed.Designers are often confronted by a problem wherein the wave shaper should be embedded in charge passively; for example, sensing elements have to be embedded in charge to decrease the length of the warhead in many smart ammunition systems. Thus, the wave shaper has to be embedded in charge to clothe these sensing elements. In addition, the wave shaper could be embedded in charge actively, such that EFP length-diameter ratio can be increased because of detonation wave shaping by using the wave shaper.The effect of wave shaper and liner on formation of EFP has been reported in this paper. Methods of avoiding breakage at the nose of the EFP and match relationship between wave shaper and liner have been obtained. Finally, good shape EFPs high velocity and large length-diameter ratio have been obtained by optimizing the warhead. The main contents could be summarized as follows:(1)An analytical model for liner element collapse velocity calculation is presented, which includes the model of calculating liner element collapse velocity driven by detonation wave, the model of calculating liner element collapse velocity driven by Mach wave, the model of calculation attack angle of the detonation wave, and the model of calculating mass of effective charge. The analytical can use to study the effect of wave shaper and liner on the formation of EFP. X-ray experiment results show that the error of calculation velocity of the EFP is below 10%, which indicates the analytical model is reliable.(2) An analytical model for Mach wave parameter calculation is presented based on three-shock theory. The parameters of Mach waves, such as the growth angle, their radius, their velocity along the plane of symmetry, and the pressure behind them, can be determined. The analytical can use to study the effect of wave shaper on the Mach wave parameters, and methods of avoiding breakage at the nose of the EFP could be obtained. Results show that, avoiding the occurrence of Mach waves by reducing the incident angle fails to avoid breakage at the nose of the EFP, but lowering the pressure behind the Mach wave by increasing the incident angle avoids breakage at the nose of the EFP.(3) The effect of wave shaper and liner on formation of EFP has been studied by analytical calculation and simulation. Match relationship between wave shaper and liner has been studied too. Analytical results show that increasing the wave shaper diameter and reducing the liner radius of curvature can significantly increase the EFP length-diameter ratio. When the large diameter wave shaper is used, the large radius of the curvature liner should be chosen to match the wave shaper. If the small radius of the curvature liner is used, the small diameter wave shaper should be chosen to match the curvature liner so that the breakage at the nose of the EFP can be avoided. If the wave shaper diameter and liner radius of curvature are unlimited, a small diameter wave shaper and a small radius of the curvature liner should be used to obtain the highest penetration capability of the EFP.(4) An analytical model for calculating the time of shock wave propagating in the wave shaper is presented. The calculation results show that three typical detonation wave contours can be formed in the main charge by changing the thickness of the wave shaper. Effect of the three typical detonation wave contours on the formation of the EFP can be analyzed, and the good shape EFP can be obtained by optimizing the detonation wave contour. Results show that, the conical detonation wave can greatly increase EFP length-diameter ratio, but the Mach wave may break the nose of the EFP. The spherical detonation wave prevents an increase in the EFP length-diameter ratio. The plane detonation wave can increase the EFP length-diameter ratio and keep the nose of the EFP integrated. The thickness of the wave shaper should be less than and approximately equal to the critical thickness to ensure that the detonation wave can increase the length-diameter ratio of the EFP.To verify the reliability of the simulation results, X-ray experiments and depth of penetration experiments on three warheads are carried out. In the three warheads, there is no wave shaper, with a small diameter wave shaper (the wave shaper diameter is 0.5 times the charge diameter), and with a large diameter wave shaper (the wave shaper diameter is 0.8 times the charge diameter), respectively. The results show that, EFP velocity errors are 9.1%, 5.1%, and 3.3%, EFP length-diameter ratio errors are 18.6%,9.5%, and 13.9%, depth of penetration errors are 9.1%,12.2%, and 5.9%,the respectively. Those errors indicate the simulation results are believable.