Spall Control in the Projectile Explosive Driving

In the process of projectile explosive driving, the front surface of the projectile whose thickness is larger than a certain size is usually packaged to reduce the negative pressure and prevent spalling.It is found that two negative pressures may be produced in the packaged projectile under the explosive load pulse.The first negative pressure is only relevant to the type of the package material, in addition to which, the second negative pressure also depends on the thickness of package material.With the given projectile and package material, the critical condition satisfied by loading pressure of shock wave and unloading pressure of rarefaction wave is derived.The first negative pressure is prevented under this condition.Furthermore, when the value of the first negative pressure is zero, in order to prevent the second negative pressure, the critical thickness of the package material is obtained in this paper.The projectile Fe, Al packaged by different materials are simulated by AUTODYN simulator and the analytical results are in good agreement with those of numerical results.Besides, the contrast of rectangular and triangular shock wave is given.This work will provide reference for engineering design of the package materials in the process of projectile explosive driving.