Asymmetries and Their Impact on Explosively Formed Projectiles Performance

Abstract: Shaped Charges (SC) are explosives which are set up to concentrate the energy of an explosive to deform a thin metal cover, so called liner into either a jet of particles or a solid projectile, the latter one is refered to an Explosively Formed Projectile or EFP. The purpose of this project is to map out the effect of different asymmetries in different parts of the EFP. Several asymmetries are investigated such as cavities in the explosive, offset positions of the point of detonation as well as an array of errors concerning the liner. Using ANSYS Space Claim for modelling and IMPETUS for simulating the combustion of the explosive and deformation of the liner.  By analyzing the velocity of the projectile in both the direction it is pointed in and in the direction of the asymmetry a mapping of how potential production errors effect its performance. The following is some of the most interesting results acquired:  There is close to no difference having the detonation point further in, there is however a crucial difference in performance for the remaining asymmetries. Rust gives an asymmetrically deformed projectile, although rust on the inside perimeter of the liner gives better results than having the rust on the outside perimeter it still gives a close to useless projectile because of its form. Skewed detonation seems to give approximately 1 m/s velocity per 0.5mm of distance from the central axis. Although the simulations run here only gave a miss of around a decimeter the rotational velocity of the projectiles is what is most worrying. When it comes to cavities in the HE there is a clear pattern of the effects getting worse the closer to the liner the bubbles are. The Offset detonation shows most rotation.