Almost like steel, but with nuances: light alloys in tank armor against cumulative shells

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Almost like steel, but with nuances: light alloys in tank armor against cumulative shells

It is widely believed that armor made of light alloys, especially aluminum, due to its low physical and mechanical properties, is suitable exclusively for light combat vehicles such as infantry fighting vehicles and armored personnel carriers and can only provide protection against bullets and small-caliber ammunition from automatic guns. Therefore, the use of these materials as fillers for tank armor supposedly has no benefit at all.

In this material, based on test results, we will show that this is not so. Alloys based on aluminum, magnesium and titanium against cumulative projectiles at certain thicknesses show themselves no worse than steel.




Aluminum, magnesium and titanium


Perhaps we need to start with the fact that the tests described in this material were carried out forty years ago in the USSR and were widely replicated in the specialized scientific literature. The purpose of their implementation was to determine the anti-cumulative resistance of light alloys used as a filler tank armor, as well as determining the dependence of their protective ability on the thickness of the layers.

As part of these activities, the following three alloys were selected as test subjects.

Based on aluminum - the ABT-102 armor alloy with the addition of zinc and magnesium, from which hulls for the famous BMP-3 are still made today. Its density is 2,78 grams per cubic centimeter, tensile strength is 460 MPa, hardness is 140 HB and dynamic modulus of elasticity is 70 GPa.

Magnesium-based - MA2-1 alloy with aluminum, zinc and manganese. Its density is 1,79 grams per cubic centimeter. Tensile strength – 270 MPa, hardness – 60 HB, dynamic modulus of elasticity – 40 GPa.

Based on titanium - VT-6 alloy with aluminum, vanadium and iron. Its density is 4,43 grams per cubic centimeter. The tensile strength is the highest relative to the previous ones - 850 MPa, hardness - 300 HB. Dynamic modulus of elasticity – 130 GPa.

Sheets with thicknesses of 140, 280 and 420 millimeters were made from titanium and aluminum alloy, and only 140 and 280 mm from magnesium alloy. All of them (separately, of course) were placed between two steel barriers, thereby simulating tank armor like a “sandwich”.

Cumulative 105 mm M456 projectile. During the experiment, we focused on its armor penetration
Cumulative 105 mm M456 projectile. During the experiment, we focused on its armor penetration

The thickness of the front steel plate was 107 millimeters along the path of the cumulative jet. This indicator was due to the need to exclude high-explosive and impact impacts on the materials under study. But the thickness of the rear steel barrier was selected in such a way that the cumulative jet, which has residual penetration after overcoming the front plate and light alloy, could not penetrate it - this way it was possible to evaluate the contribution of aluminum, magnesium and titanium fillers to the overall protection.

As for the destructive weapon itself, its role was played by cumulative shells with an armor penetration of 330–350 millimeters, similar to shells for 105-mm rifled guns for NATO tanks.

When is it protected like steel?


Generally speaking, a comparison of the resistance of steel and, for example, aluminum armor is often associated with the fact that the thickness of the latter, in order to provide the required level of protection, must always be greater. After all, we are talking about a compromise - if you want less weight, you pay with increased dimensions of armored parts made from materials of lower density.

And you don’t have to look far for examples: in the BMP-3, the thickness of the ABT-102 alloy reaches up to 50 millimeters, although the same level of protection can be provided by 15–20 mm sheets of high-hard armor steel.

But in the case of using light alloys in tank armor, the situation is somewhat different.

During the shelling of tank armor simulators with 140 mm layers of ABT-102 aluminum alloy, it turned out that its contribution to the overall protection of the armor part is on average 149 mm. In other words, every millimeter of its thickness in a barrier is practically equivalent (even slightly superior) to the same millimeter of steel armor. At the same time, the mass of a 140-mm layer of ABT-102 corresponded to the mass of a steel sheet of a similar shape with a thickness of 50 millimeters.

In the turrets of T-64 tanks of early series, aluminum alloy filler was used
In the turrets of T-64 tanks of early series, aluminum alloy filler was used

Slightly smaller, but still impressive results were shown by shelling armor with a 140-mm layer of MA2-1 magnesium alloy. Its contribution to the overall protection of the armor part averaged 140 mm. Like ABT-102, MA2-1 against cumulative ammunition with such a thickness is almost equivalent to steel armor, but weighs even less - like a 32-mm steel sheet.

Armor with a 140-mm layer of titanium alloy VT-6 gave generally similar performance. His contribution to overall defense is 142 millimeters on average. That is, like the previous two materials, it has anti-cumulative resistance parameters similar to steel in a given thickness. True, due to its higher density, the mass of a 140 mm sheet of this alloy is much higher and is equal to the mass of a steel plate 80 mm thick.

Thus, the use of light alloys for protection against cumulative weapons in tank armor is completely justified when it comes to an alternative to steel masses. Moreover, with similar anti-cumulative resistance, they weigh several times less than steel - the weight benefit is obvious.

But there is one important nuance here.

You can't go too far in terms of thickness


The fact is that the light alloys discussed above have anti-cumulative resistance comparable to steel only in limited thicknesses. With their significant increase, the efficiency drops noticeably due to the establishment of a stable regime of penetration of the cumulative jet into an obstacle with low density and low strength characteristics.

For example, when firing at an armor simulator with a layer of ABT-102 aluminum alloy 240 mm thick, its contribution to the overall protection is on average 151 millimeters, which is only 2 mm more than in experiments with 140 mm aluminum layers. If the layer thickness is increased to 420 mm, then the contribution, although it increases, but not much - on average, only 177 mm.

At the same time, a layer of ABT-102 with a thickness of 420 mm weighs the same as a steel plate of a similar shape with a thickness of 150 mm. So the benefit in terms of mass is almost completely lost.

Aluminum filler in the upper frontal part of the hull and the frontal part of the turret of the Object 432 tank
Aluminum filler in the upper frontal part of the hull and the frontal part of the turret of the Object 432 tank

With titanium alloy VT-6 the situation is even worse.

When the thickness of its layer increases to 280 mm (the mass of the layer corresponds to 160 mm of steel), its contribution to protection averages 163 millimeters. If the titanium alloy layer is increased to 420 mm, then its contribution to the overall protection is on average 170 mm. Moreover, in this case it will weigh like an array of steel 240 millimeters thick.

As for magnesium MA2-1, an increase in the layer of this material in the armor generally leads to a decrease in the contribution to the overall protection: with a thickness of 280 mm, it produces an average of only 134 mm equivalent from a cumulative jet. The latter is due to the fact that such a fragile and low-strength alloy does not have any significant braking effect on the tail parts of the cumulative jet.

Based on all of the above, light alloys, although they are very useful materials that make it possible to lighten the weight of a tank’s armor protection, should be used only within critical thicknesses.

In other words, the main thing is not to overdo it, otherwise you won’t achieve any gain in weight and durability comparable to steel.

Sources:
A. I. Anisko, V. N. Bryzgov, N. M. Grishina “Anti-cumulative resistance of light alloy fillers.”
V. A. Grigoryan, A. N. Beloborodko, N. S. Dorokhov and others. “Particular issues of finite ballistics.”
34 comments
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  1. +2
    10 July 2024 05: 17
    I wonder if they tried to fill this inner layer with some kind of refractory filler such as expanded clay, perlite, vermiculite? Could he cut this stream?
    1. +5
      10 July 2024 05: 26
      Quote from Hipper
      I wonder if they tried to fill this inner layer with some kind of refractory filler such as expanded clay, perlite, vermiculite? Could he cut this stream?

      We tried corundum, it helps!
      1. +7
        10 July 2024 05: 36
        We tried corundum, it helps!

        And we tried sand wassat
        1. 0
          10 July 2024 05: 43
          Quote: Eduard Perov
          And we tried sand

          For export! Sand for export, but at speculative prices, this is strong. laughing
          1. +5
            10 July 2024 05: 46
            For export! Sand for export, this is strong.

            Why export? All tanks of the T-72A and T-80B\BV type have a sand "head". what
            1. 0
              10 July 2024 05: 50
              Quote: Eduard Perov
              Why export? All tanks of the T-72A and T-80B\BV type have a sand "head".

              Because only tanks with sand cores were exported, EMNIP.
              1. +3
                10 July 2024 05: 58
                Because only tanks with sand cores were exported, EMNIP.

                The T-72S did not have sand, as did the T-80U supplied to other countries. But if we talk specifically about the T-72M/M1, then yes, there was nothing made of filler other than sand or solid steel armor.
                1. 0
                  10 July 2024 06: 03
                  Well, this is no longer the USSR, but the Russian Federation. It was special, everything was sold out.
                  Quote: Eduard Perov
                  T-72S did not have sand
                  They just write that they sent S-ki with sand to Iran.
                  1. +1
                    10 July 2024 10: 18
                    I don’t remember, somewhere they used metal-ceramic or carbide balls as a filler? Perhaps not with us. recourse
                    1. +1
                      10 July 2024 10: 26
                      Quote from Enceladus
                      I don’t remember, somewhere they used metal-ceramic or carbide balls as a filler? Perhaps not with us.

                      https://topwar.ru/195906-keramika-v-tankovoj-brone-zaschita-ot-kumuljativnyh-snarjadov.html
                      1. +1
                        10 July 2024 10: 27
                        Oh pasip! Yes, I remember the article - I need to re-read it, restore it, so to speak... Eh... old age is not a joy wassat hi
                        ZY hi drinks
                      2. +2
                        10 July 2024 10: 38
                        Quote from Enceladus
                        Oh pasip! Yes, I remember the article - I need to re-read it, restore it, so to speak... Eh... old age is not a joy

                        Thanks to the author, this is also his article.
                      3. +1
                        10 July 2024 10: 41
                        Quote: Vladimir_2U
                        Thanks to the author, this is also his article.

                        Well, so... but also for you... Well, Lyova! Well, detective! (c) Features of the national hunt laughing This is where he found the PM after the tree with dynamite.... although another lol
  2. +5
    10 July 2024 05: 30
    Titanium alloys are a bit expensive, although they are much stronger and more heat-resistant than aluminum alloys. And thick, but light armor is needed, Bradley and even M113 have shown themselves well in terms of durability.
    1. +10
      10 July 2024 05: 53
      our drone pilots admitted that the Bradley is a very durable machine. although everyone laughed at it, they even made a movie (the Pentagon wars, a good comedy), but it turned out to be an excellent car (but the idiots will downvote this comment, because all of their equipment is not ours, guano, only ours can be good)
      1. -1
        10 July 2024 06: 41
        That’s why they laughed (and laugh), because Bradley generally cut on a cosmic scale.
        And although that film looks like a comedy, in many key details it faithfully reproduces the original book, and this book is far from humorous and was written by a person who was directly involved in the development and testing of Bradley.
        And he wrote it not with the desire to laugh, but on the contrary, as an attempt to show how “rotten everything is in the Kingdom of Denmark.” That is, in the Pentagon.
        Instead of a fast, stealthy and cheap “combat taxi”, they ended up with an expensive, hefty sub-tank. And everyone understood everything, but money always wins.
        The project for littoral ships is from the same opera. It’s just that Bradley was created during the Cold War, so they didn’t throw the half-baked thing in the trash, and there was no time to start development from the beginning.
        1. +8
          10 July 2024 14: 26
          It's not a cut, but our fighters put Bradley in 1st place in terms of survivability. It is generally very difficult to set it on fire right away. The thing turned out to be very worthy. Intelligence has a conversation on this topic with a soldier from the UAV company. - "BEST IN THE HOME 3: SURVIVALITY OF ENEMY "ARMOR"". So it was too early for everyone to laugh.
        2. +4
          10 July 2024 15: 14
          Similar films can be made about many types of weapons and military equipment. For example, about the same moment 29.
  3. +5
    10 July 2024 05: 39
    But what if there are 2-3 sheets of 140mm across 20-30mm steel armor plates? I would also like to read a similar article for BOPS and impact cores. although the role of BOPS is falling more and more, and the role of cumulative weapons and control units is increasing. I would also like to talk about the resistance of armor and alloys to fracture and other deformations from high-explosive effects, because in the same Ukraine, tanks with artillery with close explosions were taken out more often than with BOPS (IMHO, I could be wrong)
  4. +1
    10 July 2024 07: 27
    The relationship between weight and size characteristics is more or less clear. And with the cumulative jet, what happens and why did you come to the conclusion that these alloys can be used?
    1. +3
      10 July 2024 09: 08
      And what happens with the cumulative jet...

      To a first approximation, a jet of liquid metal from a cumulative cone penetrates into the layer of liquid armor. Extremely high pressures during the interaction of metals cause stresses significantly exceeding the plastic limit.
      This approximation allowed Mikhail Alekseevich Lavrentyev to create the theory of cumulative penetration. Here is a popular article _https://topwar.ru/224161-kumuljativnyj-jeffekt-akademika-lavrenteva.html. In addition to this article, I will provide scans from the book Mikhail Alekseevich Lavrentiev and Boris Vladimirovich Shabash
      Methods of the theory of functions of a complex variable M., 1965, 716 pp.
      they contain a qualitative description of the process. And the details of what and how happens with the above reservation are obviously not for open sources.
      1. +1
        10 July 2024 12: 16
        The book describes the physical process of the cumulative effect in relation to armor. I was wondering how the light alloy armor itself affects the cumulative jet? For example, maybe it dampens its speed, reduces its kinetic energy?
        1. +2
          10 July 2024 13: 55
          For example, maybe it dampens its speed, reduces its kinetic energy?

          I think that to get answers to such questions you should not ask here. In Soviet times, the description of the functions of every third rivet was classified as chipboard. I don’t know how now.
        2. 0
          11 July 2024 01: 25
          I can assume that light metals begin to evaporate under the influence of a cumulative jet, absorbing a considerable amount of thermal energy; for aluminum, for example, the enthalpy of vaporization is several times higher than that of water.
          But what kind of tricks they made, that the slab was made twice as thick and the cumulative jet flew further, I don’t really understand
      2. 0
        10 July 2024 15: 23
        Quote: Sensor

        To a first approximation, a jet of liquid metal from a cumulative cone penetrates into the layer of liquid armor.

        Within the framework of the hydrodynamic scheme, it would be interesting to consider the option of propagating a cumulative jet not “in an environment with constant pressure” but in a layer of gradient density, with the direction of the gradient perpendicular to the vector of movement of the jet. Such gradients, in theory, can be obtained in metal alloys of different densities. Is this the reason for the limited success of aluminum armor? If its effectiveness is due only to a thin gradient layer, then its further thickening does not provide any advantages.
    2. +4
      10 July 2024 10: 17
      Quote: Semak
      what is happening and why did you come to the conclusion that these alloys can be used?

      We described it more or less above, but it could be a little simpler. Under such pressure, metals behave like liquids and accordingly obey hydrodynamics. Actually, the cumulative jet does not burn through (you probably remember the story when we called cumulative shells armor-piercing) and does not penetrate - it “washes” the armor, if you can say at the everyday level. And the fact that there is supposedly melted metal at the edges - it does not melt - but just flowed out, so to speak.
      1. +2
        10 July 2024 12: 28
        The process of rapid transition from one state of aggregation to another has not been fully studied, much less the process of transfer of kinetic energy into thermal energy. There are problems there. More heat is released than expected by calculations.
  5. +1
    10 July 2024 12: 06
    Hardware and electronics are now available and relatively cheap. Therefore, we must strive for unmanned vehicles that do not need protection from cumulative projectiles. Its protection will be mass distribution, small dimensions and mobility....
  6. +5
    10 July 2024 12: 16
    It's all war, yes war. We would like to conduct a study of these alloys for car bodies. Our Deripaska is choking, selling aluminum for next to nothing. And then, maybe, for once, UAZs would get stainless steel ones.
    1. +2
      10 July 2024 15: 04
      And then, maybe, for once, UAZs would get stainless steel ones.

      Rolled sheets OT-4-1 5616 RUR/kg.
      _https://www.metprokat.su/produkciya/titan/list/ot4-1/
      The strength characteristics are worse than those of VT-6 (Ti-6Al-4V), but at a lower price.
      I understand that I really want to have a stainless UAZ. Speaking of corrosion resistance, titanium and iron make an excellent galvanic pair.
  7. +1
    10 July 2024 12: 21
    Well, combined armor was invented about 40 years ago, but in fact they don’t install anything else now. For now, the best protection option is dynamic protection.
    1. +1
      10 July 2024 21: 13
      Quote: PoruchikGT
      For now, the best protection option is dynamic protection.

      DZ without a layer of armor underneath is useless. It only breaks the stream into several drops with less energy and the armor should then stop these drops.
  8. 0
    11 July 2024 01: 32
    Will there be an article about liquid armor? Nobody tried to approach the matter properly, and not just by placing tanks with diesel fuel in vulnerable places? Maybe the tank can be lined with a couple of layers of 0.5 plastic bottles and you won’t be able to break through it? Or twenty centimeters of paraffin?
    In general, sometimes one gets the impression that the cumulative effect has not been studied in the normal way, but is simply making shells and seeing whether it will penetrate or not, and then expressing their conjectures on the fingers
  9. 0
    13 July 2024 08: 58
    Quote: Saxahorse
    DZ without a layer of armor underneath is useless. It only breaks the stream into several drops with less energy and the armor should then stop these drops.

    For lightly armored vehicles, installing emergency protection is problematic due to the impact of the emergency protection itself on its rather thin armor when triggered. On the same Bradley, it was necessary to add an additional layer between the main armor and the remote sensing blocks.