Abstract:
This project report describes a numerical modeling of explosively formed projectiles
(EFP) passing through void and water. Explosively formed projectiles are being used for
neutralizing sea mines. Penetration through water is studied by using copper, and
Tungsten made liners. Copper made liners show poor performance in water as they
eroded immediately on passing through water; however their length of penetration can be
extended to some extent by changing liner thickness (contour type thickness) and by
making solid final shape. Their penetration length can also be increased by replacing
copper with tungsten from 4 to 8 times. Liner curvature is very sensitive parameter to its
final shape and velocity. In this report a good exercise is done by varying liner curvature
and optimum curvature for that particular design (theta=120 degree) is obtained. Effect of
moving water on EFP performance is also studied and it is concluded that if water is
moving in opposite direction, with normal river speed, then it has no pronounced effect
on the EFP performance. Of all the available explosives HMX shows better results as it
has higher density and detonation velocity. EFP devices are similar to a shaped charge,
except the apex angle of the liner, which is greater than or equal to 120° (depending upon
material used). EFPs are low-velocity devices as compared to shaped charges and have a
tip velocity of 2-3 km/s(7-12km/s in case of shaped charges). However, they generate
large diameter, high mass projectiles and produce large holes in the target material.
Underwater mines clearance is a difficult and demanding task. Under water munitions
cannot be defused, neutralized or transported to any other places. If the velocity of
explosively formed projectile (EFP) is low enough and the hole it creates in the casing of
the underwater munitions is large enough, explosive charge contained in it will burn
without detonation thus ensuring that mine has safely defused.
