10 months ago
High Explosive Anti Tank Shell
HEAT is shell with shaped charge with cumulative insertion. Detonation of such charge cause deformation of insertion into ray of mass with speed of few thousand m/s. Main idea behind this shell is that the armor penetration doesn't depend on the impact energy.
Detonation of cumulative charge will cause formation of cumulative flow which is divided into three main parts and fourth in some cases.
Cumulative ray - Formed by material of cumulative insertion with speed around 2000 - 10000 m/s. It has parts with different speed and diameter. Diameter of ray is around 1/10 of cumulative insertion base diameter. Cumulative ray is the main part which causes penetration. Important factors are speed and distribution of weight in parts of this ray.
Thumper - Rest of the material from cumulative insertion with speed around 300 - 1000 m/s. It doesn't have influence on penetration.
Part of the combustion gases from detonation - The main effect of those gases is thermal effect after penetration, but pressure effect is too small to consider it important.
Edge parts of not fully deformated insertion - Not important to anything at all.
Issues with HEAT shells
To achieve the best penetration effect we have to respect that the cumulative ray is less effective when rotation of shell is faster than 2000 rpm, because ray will become more dispersed. This means that HEAT shells were less accurate and had different ballistic curve due to this reason.
Second thing is that you have to give to the charge some distance to form ray with maximum speed. That means the shell has to have the cap with empty space in front which is causing problems with weight distribution in the shell, so another setback for ballistics.
Area of penetration is very small and the area of effect is very narrow. So this means that you have to hit important construction point to do damage.
Mechanism of penetration
Mechanism is described as hydraulic impact/penetration. It means that cumulative ray is causing much more dynamic pressure on the armor than it can withstand in such small focused area.
The HEAT shell works like this, you fire it and when it impacts the armor, it will detonate. Due to shape of the charge and insertion inside of shell it forms very focused ray of mass under heavy pressure. Energy of this pressure gives to the ray enormous speed and when heated mass about this speed hits the armor, speed is going to change again into pressure with support of heated metal material flow. After penetration this ray of mass continues in its way. There is no combustion of air inside of tank like some people say, but you have very fast and very hot "bolt" of metal going straight through the tank and behind this flies heavy chunk of metal shrapnel, sometimes a few smaller pieces. This thumper often closes entry or exit point of the hit because it is not fast enough to go through, so it becomes merged with metal of armor.