The cumulative effect in military affairs is the strengthening of the destructive effect of an explosion by means of its concentration in a certain direction. A phenomenon of this kind in a person unfamiliar with the principle of its action is usually surprising. Due to a small hole in the armor, when a cumulative projectile hits, the tank often completely fails.
Where is used
Actually, the cumulative effect itself was observed, probably by all people without exception. It occurs, for example, when a drop falls in water. In this case, a funnel and a thin jet directed upwards form on the surface of the latter.
The cumulative effect can be used, for example, for research purposes. Creating it artificially, scientists are looking for ways to achieve high speeds of substances - up to 90 km / s. This effect is also used in industry - mainly in mining. But he, of course, found the greatest application in military affairs. Ammunition operating on this principle has been used by different countries since the beginning of the last century.
Shell design
How are the ammunition of this variety manufactured and operated? A cumulative charge arises in such shells, due to their special structure. In the front of this type of ammunition there is a cone-shaped funnel, the walls of which are covered with a metal lining, the thickness of which can be less than 1 mm or several millimeters. A detonator is located on the opposite side to this recess.
After the latter is triggered, due to the presence of a funnel, a destructive cumulative effect occurs. The detonation wave begins to move along the axis of the charge into the funnel. As a result, the walls of the latter collapse. With a strong impact in the lining of the funnel, pressure increases sharply, up to 1010 Pa. Such values ​​far exceed the yield strength of metals. Therefore, he behaves in this case like a liquid. As a result, the formation of a cumulative jet, which remains very solid and has a large striking ability, begins.
Theory
The appearance of a metal jet due to the cumulative effect is not due to the melting of the latter, but to its sharp plastic deformation. Like liquid, the ammunition cladding metal forms two zones when the funnel collapses:
a thin metal stream proper, moving forward at a supersonic speed along the charge axis;
pest-tail, which is the “tail” of the jet, which accounts for up to 90% of the metal lining of the funnel.
The speed of a cumulative jet after a detonator explosion depends on two main factors:
What ammunition can be
The smaller the angle of the cone of the projectile, the faster the jet moves. But in the manufacture of ammunition in this case, special requirements are imposed on the lining of the funnel. If it is of poor quality, a jet moving at a high speed can subsequently collapse ahead of time.
Modern ammunition of this type can be made with funnels, the angle of which is 30-60 degrees. The speed of the cumulative jets of such shells that occur after the cone collapses reaches 10 km / s. In this case, the tail part has a lower speed due to the larger mass - about 2 km / s.
Origin of the term
Actually the word "cumulation" itself came from the Latin cumulatio. Translated into Russian, this term means “accumulation” or “accumulation”. That is, in fact, in shells with a funnel, the energy of the explosion is concentrated in the right direction.
A bit of history
Thus, the cumulative stream is a long thin formation with a “tail”, liquid and at the same time dense and rigid, moving forward at great speed. Such an effect was discovered long ago - back in the 18th century. The first assumption that the energy of the explosion can be concentrated as necessary was expressed by engineer Fratz von Baader. This scientist conducted several experiments related to the cumulative effect. However, at that time he failed to achieve any significant results. The fact is that Franz von Baader used black powder in his research, unable to form detonation waves of the required strength.
For the first time, ammunition operating on a cumulative principle was created after the invention of high-explosive explosives. In those days, a cumulative effect was simultaneously and independently discovered by several people:
Russian military engineer M. Boriskov - in 1864;
Captain D. Andrievsky - in 1865;
European Max von Forster - in 1883;
American chemist C. Munro - in 1888
In the Soviet Union in the 1920s, Professor M. Sukharevsky was engaged in a cumulative effect. In practice, the military first encountered him during the Second World War. This happened at the very beginning of hostilities - in the summer of 1941. German shaped-charge shells left small melted holes in the armor of Soviet tanks. Therefore, initially they were called armor-burning.
Such shells BP-0350A were adopted by the Soviet army in the 42nd year. They were developed by domestic engineers and scientists based on captured German ammunition.
Why breaks through armor: the principle of the cumulative jet
During the Second World War, the features of the "work" of such shells have not yet been well studied. That is why the name “armor-piercing” was applied to them. Later, already in the year 49, the cumulative effect in our country was taken up closely. In 1949, the Russian scientist M. Lavrentiev created the theory of cumulative jets and received the Stalin Prize for this.
In the end, the researchers were able to find out that the high breakdown ability of shells of this type with high temperatures is absolutely not connected. When a detonator detonates, a cumulative jet forms, which when in contact with the tank’s armor creates a huge pressure on its surface of several tons per square centimeter. Such indicators exceed, including the yield strength of the metal. As a result, a hole with a diameter of several centimeters forms in the armor.
The jets of modern ammunition of this type are capable of flashing tanks and other armored vehicles literally through. The pressure when they act on the armor is really huge. The temperature of the cumulative projectile jet is usually low and does not go beyond the values ​​of 400-600 ° C. That is, it cannot actually burn through the armor or melt it.
The cumulative projectile itself does not come into direct contact with the material of the tank walls. It explodes at some distance. Parts of the cumulative jet move after it is ejected at a different speed. Therefore, during the flight, it begins to stretch. When reaching a distance of 10-12 diameters of the funnel, the jet breaks up. Accordingly, it can have the greatest destructive effect on the armor of a tank when it reaches its maximum length, but does not yet begin to collapse.
Crew defeat
The cumulative jet that penetrates the armor penetrates the interior of the tank at high speed and can affect crew members as well. At the moment of its passage through the armor, pieces of metal and its liquefied drops come off from the latter. Such fragments, of course, also have a strong damaging effect.
The jet penetrated into the tank, as well as pieces of metal flying at tremendous speed, can also fall into the combat stocks of the vehicle. In this case, the latter light up and an explosion occurs. This is how cumulative shells act.
Advantages and disadvantages
What are the advantages of cumulative shells? First of all, the military refers to their advantages that, unlike the sub-caliber, the ability to penetrate armor does not depend on their speed. Such shells can also be fired from light guns. Also, such charges are quite convenient to use in jet grants. For example, in exactly this way the RPG-7 manual anti-tank grenade launcher. The cumulative stream of such weapons armored tanks with high efficiency. The Russian RPG-7 grenade launcher is still in service today.
The after-effects of the cumulative jet can be very damaging. Very often, she kills one or two crew members and causes an explosion in ammunition stockpiles.
The main disadvantage of such weapons is the inconvenience of their use of the "artillery" method. In most cases, in flight, the shells are stabilized by rotation. In cumulative ammunition, it can cause the destruction of the jet. Therefore, military engineers make every effort to reduce the rotation of such shells in flight. A variety of methods can be used for this.
For example, in such ammunition, a special cladding texture may be used. Also for this type of shells are often complemented by a rotating body. In any case, it is more convenient to use such charges in low-speed ammunition or even stationary ones. This can be, for example, rocket-propelled grenades, shells of light guns, mines, ATGMs.
Passive protection
Of course, immediately after cumulative charges appeared on the armament of the armies, means began to be developed that would prevent them from defeating tanks and other heavy military equipment. For protection, special remote screens were developed, installed at a certain distance from the armor. Such tools are made of steel gratings and metal mesh. The effect of the cumulative jet on the armor of the tank, if any, is nullified.
Since when it hits the screen, the projectile explodes at a considerable distance from the armor, the jet manages to collapse before it reaches it. In addition, some varieties of such screens are capable of destroying the contacts of the detonator of a cumulative ammunition, as a result of which the latter simply does not explode at all.
What protection can be made of
During the Second World War, the Soviet army used quite massive steel screens. Sometimes they could be made of 10 mm steel and carried out by 300-500 mm. During the war, the Germans everywhere used lighter steel mesh protection. At the moment, some durable screens are able to protect tanks even from high-explosive fragmentation shells. Causing detonation at some distance from the armor, they reduce the degree of impact on the car shock wave.
Sometimes, multilayer shields are currently used for tanks. For example, a steel sheet 8 mm thick can be carried out onto a 150 mm machine, for example, after which the space between it and the armor is filled with lightweight material - expanded clay, glass wool, etc. Next, a steel mesh is placed over such a screen by 300 mm. Such devices are able to protect the machine from almost all types of ammunition with explosive explosives.
Dynamic protection
Such a screen is also called reactive armor. The protection of this species in the Soviet Union was first tested in the 40s by engineer S. Smolensky. The first prototypes were developed in the USSR in the 60s. The production and use of such protective equipment in our country began only in the 80s of the last century. This delay in the development of reactive armor is explained by the fact that it was initially recognized as unpromising.
For a very long time, the Americans did not use this type of defense either. The first to actively use reactive armor began the Israelis. Engineers from this country noticed that with an explosion of ammunition stockpiles inside the tank, the cumulative stream does not penetrate the car through. That is, a counter-explosion is capable of holding it back to some extent.
Israel began to actively use the dynamic protection against cumulative shells in the 70s of the last century. Such devices were called "Blazer", made in the form of removable containers and placed outside the armor of the tank. In them, a Semtex explosive based on RDX was used in them.
Later, the dynamic protection of tanks against cumulative shells was gradually improved. At present, in Russia, for example, Malachite systems are used, which are complexes with electronic control of detonation. Such a screen is capable of not only effectively counteracting cumulative projectiles, but also destroying the most modern NATO subcaliber DM53 and DM63, designed specifically to destroy the Russian dynamic defenses of the previous generation.
How a jet behaves under water
In some cases, the cumulative effect of ammunition may be reduced. For example, the cumulative jet under water behaves in a special way. Under such conditions, it breaks up already at a distance of 7 diameters of the funnel. The fact is that at high speeds punching water jet is about as "heavy" as metal.
On Soviet cumulative ammunition for use underwater, for example, special nozzles were installed to facilitate the formation of a jet and equipped with weighting agents.
Interesting Facts
Of course, in Russia at the moment, work is underway to improve, including the most cumulative weapons. Modern domestic grenades of this variety, for example, are able to break through a metal layer more than a meter thick.
Weapons of this variety have been used by different countries of the world for a long time. However, various legends and myths still circulate about him. So, for example, sometimes on the Web you can find information from the fact that cumulative jets when they enter the tank’s internal space can cause such a sharp pressure surge that this leads to the death of the crew. Terrible stories including the military themselves often tell about this effect of cumulative waves on the Internet. There is even an opinion that during the hostilities, Russian tankers travel specially with open hatches in order to relieve pressure in the event of a cumulative projectile.
However, according to the laws of physics, a metal jet cannot cause such an effect. Shells of this type simply concentrate the energy of the explosion in a certain direction. To the question of whether the cumulative jet burns through or pierces the armor, there is, therefore, a very simple answer. When meeting with the material of the tank walls, it slows down and really exerts strong pressure on it. As a result, the metal begins to spread on the sides and wash out with drops at high speed inside the tank.
In this case, the material liquefies precisely because of pressure. The temperature of the cumulative jet is low. In this case, of course, she herself does not create any significant shock wave. The human body is capable of piercing a jet through. Drops of liquid metal, detached from the armor itself, also have a serious destructive power. But the shock wave from the explosion of the ammunition itself is not able to penetrate the hole made by the jet in the armor. Accordingly, no excess pressure inside the tank occurs.
According to the laws of physics, the answer to the question of whether the cumulative jet pierces or burns through the armor is thus obvious. Upon contact with the metal, it simply dilutes it and passes into the machine. She does not create excessive pressure behind the armor. Therefore, it is certainly not worth opening the hatch of the car when the enemy uses such ammunition. On top of that, on the contrary, it increases the risk of shell shock or death of crew members. An explosive wave from the projectile itself can penetrate into the open hatch.
Experiments with water and gelatin armor
You can recreate the cumulative effect if desired, even at home. This will require distilled water and a high voltage arrester. The latter can be made, for example, from a cable, soldered to its braid coaxially with the main residential copper washer. Next, the central wire must be connected to the capacitor.
The role of the funnel in this experiment can be played by the meniscus formed in a thin paper tube. The spark gap and capillary must be connected with a thin elastic tube. Next, pour water into the tube using a syringe. After the meniscus is formed at a distance of about 1 cm from the arrester, it is necessary to insert a capacitor and close the circuit with a conductor mounted on an insulating rod.
In the breakdown region, such a home experiment will develop a lot of pressure. The shock wave will run to the meniscus and collapse it.