Tuesday, 22 March 2016

Fragmentation vs Tanks

Previously, our friends at the Armoured Journal (Bronetankoviy Vestnik) looked at how to model the amount of damage an HE shell does to a tank. This article discusses a similar topic, but looks at how fragments from HE and HEAT shells behave once they hit a tank with the goal of damaging as much of the tank's external equipment as possible.

The article separates the effect of the fragments into two stages: primary (fragments of the shell fly from the explosion to the armour) and secondary (fragments bounce off the armour, spread out further across the surface the shell hit). Trials demonstrated that the secondary effect of HE and HEAT shells when fired at domestic tanks is more or less equivalent. However, the primary effect is drastically different.

Fig. 1: Spread of fragments from a HEAT shell after explosion (the dispersion ellipse is shown in a dotted line and is rotated 90 degrees.

The area damaged by the fragments is proportional to the length between the contact point between the shell and armour and the top of the cone from which the fragments spread, h0. Naturally, h0 is greater for longer shells. Experiments also revealed that a HEAT shell's h0 is about twice as much as that of an HE shell, meaning that the area in which a HEAT shell could hit and still knock out a Leopard 2's sight was 1.5 times larger than the same area for an HE shell.

Fig. 2: Damage diagram for a Leopard 2 tank hit with fragments from a HEAT shell (top) and HE shell (bottom).
1 - Gun sight.
2 - Shell. Fragments distribution is shown in a hatched area.

The fragmentation from a 125 mm BK-14M HEAT shell at impact velocity of 900 m/s and an angle of 20 degrees is shown in the following table:

Fragmentation
Angle of fragments
Average density
% of fragments that can penetrate an aluminium screen x mm thick:
x=5
x=60
Primary
47-38
500
50
10
Primary
38-12
500
19
-
Secondary
0-7
300
33
-
Secondary
7-22
140
4
-

Fig. 4: Formation of a secondary fragmentation stream.
1 - HEAT shell
2 - Armour
3- Test screens

4% of primary fragments create a hole with a maximum height or width of 50-100 mm, 11% 10-50 mm, and the remaining fragments less than 10 mm. Secondary fragments are smaller and make holes no larger than 30 mm. The majority of the fragments are within 7 degrees of the armour surface.

Via andrei_bt.

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