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Fucking NERA everywhere


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On 10/21/2017 at 7:44 AM, Collimatrix said:

 

 

 

2)  I believe that the heavy ERA designed specifically to counter KEPs is designed to snap the projectile.  Other reactive armors don't necessarily work the same way.  I've seen papers on ERA with low-density ceramic and polymer flyer plates, and it apparently works as well as steel on a weight basis.  Look up "The Defeat of Shaped Charge Jets by Explosively Driven Ceramic and Glass Plates" by Paul Hazell if you have access to journals and you're curious.  That said, there may be some use of heavier materials in reactive armor arrays.  @SH_MM is of the opinion that the depleted uranium in the Abrams' armor is incorporated into some sort of NERA, although I personally suspect otherwise.

 

 

Im curious if other properties of the material besides just its density and hardness have more of an effect on the flyer plate/projectile interaction. In this guy's models going from HHS to tungsten alloy doesnt seem to have a major difference other than a bit more upward deflection. It seems to hint at things like heat capacity might be at play when resisting the atomizing of the plate and projectile eating up more energy. 

 

 

 

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  • 1 year later...
On 2/20/2017 at 2:27 PM, Militarysta said:

Im not sure is some values above are corret.

Some book form Russia give diffrent values:

STEF:

http://i.imgur.com/mV0Cc2L.jpg

http://i.imgur.com/4qWnBQF.jpg

 

http://i.imgur.com/Fa32YcD.jpg

 

 

 

Sorry, if my question will be stupid, but this table suggests there is no better armor material than the "good old" steel.

 

According to my understanding ME efficiency shows the armor efficiency when we keep the plate' thickness constant, and TE efficiency shows the armor efficiency when we keep the late' mass constant.

Take an example:

in the case of SiC a 20mm plate has a 20*0.34=6.8mm protection. In the case of TE efficiency 20*(7.85/3)=52.2mm thick plate has a same mass than a 20mm steel plate. 52.2*0.34~18mm which gives us 18/20=0.9 TE coefficient

 

So, why the hell makes anybody armor out of anything other than steel? Especially if we take into the account that HHS gives us around 1.1 ME/TE coefficient.

 

Is it possible that use a backing plate and appropriate interlayer material in a structure something like this, improves the ceremics' performance drastically?

Or just me understand wrong something int he abovementioned table?

 

SovSzmm.jpg

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2 hours ago, speziale said:

According to my understanding ME efficiency shows the armor efficiency when we keep the plate' thickness constant, and TE efficiency shows the armor efficiency when we keep the late' mass constant.

I think you've got that backwards

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9 hours ago, speziale said:

According to my understanding ME efficiency shows the armor efficiency when we keep the plate' thickness constant, and TE efficiency shows the armor efficiency when we keep the late' mass constant.

Take an example:

in the case of SiC a 20mm plate has a 20*0.34=6.8mm protection. In the case of TE efficiency 20*(7.85/3)=52.2mm thick plate has a same mass than a 20mm steel plate. 52.2*0.34~18mm which gives us 18/20=0.9 TE coefficient

 

No, this isn't correct. The mass efficiency (ME) doesn't say anything about the plate thickness; keeping the plate thickness constant will lead to an incorrect representation of ME. Mass efficiency just shows the efficiency of an armor material/array compared to a reference armor material/array (typically by definition RHA). So if you have an armor material with a ME of 2, then at a constant mass it will provide twice as much protection as the reference material, i.e. even though you only have 100 kilograms of the material, you would need 200 kilograms of steel armor to reach the same level of protection.

As the density of the materials can be different, the thickness of these two materials needed to reach the same protection level can be quite different. E.g. lets assume that the first material (with a ME of 2) is some kind of low-density reinforced plastic with only a fourth of the density of steel. This would not change the ME, but it would mean that you'd need 200 milimetres of this material to reach the same level of protection as provided by a 100 mm thick steel plate (as 200 mm of the material will have the same weight as 50 mm of steel while having a ME of 2, i.e. being twice as effective per weight). So the thickness is completely irrelevant for the ME.

 

However the above example also shows us the thickness efficiency (TE) of the materials, i.e. the protection provided by an armor material/array for a given thickness compared to a reference material/array (which again by definition is typically RHA). Given that 200 mm of the hypothetical material (something reinforced plastic) provide the same level of protection as 100 mm steel, the TE is 0.5 (half as much protection is provided per thickness).

 

 

I am not sure what these excerpts from Russian and Polish documents say, as I can only use a translator to understand them. But it seems that these are not directly ME and TE, but rather coefficients showing how much mass/thickness compared to steel is needed to provide the same level of protection. It is clearly not TE/ME in case of the Polish document, as this lists polyethylene (i.e. simple plastic) in an array with steel plates with a "thickness cofficient" of 7.1 against APFSDS rounds. As steel + polyethylene does not provide ~7 times the protection for a given thickness (nor does it allow reducing armor thickness significantly compared to pure steel), I would rather assume that this means something along the line of "a polyethylene array with preceeding steel plates need to have 7.1 times the thickness to provide the same protection as a simple steel plate".

 

9 hours ago, speziale said:

So, why the hell makes anybody armor out of anything other than steel? Especially if we take into the account that HHS gives us around 1.1 ME/TE coefficient.

 

The mass efficiency of simple Al2O3 armor with relatively low purity (95%) is in the area 2-2.5 against small arms when place atop of to an aluminium baseplate. This allows a massive weight reduction compared to steel armor. The efficiency of the armor (and the multi-hit capability) can be further increased by using a higher purity ceramic, a higher strength backplate, an elastic backing in the deformation zone behind the ceramic tile (preferably something like Kevlar/Twaron/Dyneema or UHMWPE) and a cover plate/splinter foil.

 

This means that the ME of Al2O3 can likely exceed 3. For high-performance "nano-ceramics", it can reach up to 5 against small arms. Against APFSDS ammo, the ME will be lower but still decent compared to steel.

 

9 hours ago, speziale said:

Is it possible that use a backing plate and appropriate interlayer material in a structure something like this, improves the ceremics' performance drastically?

 

It will significantly improve the protection provided by ceramics, yes. It is also a necessity to ensure that the ceramics don't disintegrate after one hit.

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2 hours ago, SH_MM said:

 

No, this isn't correct. The mass efficiency (ME) doesn't say anything about the plate thickness; keeping the plate thickness constant will lead to an incorrect representation of ME. Mass efficiency just shows the efficiency of an armor material/array compared to a reference armor material/array (typically by definition RHA). So if you have an armor material with a ME of 2, then at a constant mass it will provide twice as much protection as the reference material, i.e. even though you only have 100 kilograms of the material, you would need 200 kilograms of steel armor to reach the same level of protection.

As the density of the materials can be different, the thickness of these two materials needed to reach the same protection level can be quite different. E.g. lets assume that the first material (with a ME of 2) is some kind of low-density reinforced plastic with only a fourth of the density of steel. This would not change the ME, but it would mean that you'd need 200 milimetres of this material to reach the same level of protection as provided by a 100 mm thick steel plate (as 200 mm of the material will have the same weight as 50 mm of steel while having a ME of 2, i.e. being twice as effective per weight). So the thickness is completely irrelevant for the ME.

 

However the above example also shows us the thickness efficiency (TE) of the materials, i.e. the protection provided by an armor material/array for a given thickness compared to a reference material/array (which again by definition is typically RHA). Given that 200 mm of the hypothetical material (something reinforced plastic) provide the same level of protection as 100 mm steel, the TE is 0.5 (half as much protection is provided per thickness).

 

Hi SH,

 

Thank you for your answer.

But I think remains some questionmarks.

First: logically in the case of an efficiency measure higher number means higher efficiency. So, efficiency value above 1 means that given material is „better” than the RHA.

 

I think our interpreation is same in the case of ME. According to your interpretaion 100/0.34~295 kg SiC do you need to reach the same level of protection of 100 kg RHA. But this statement is equal with that 100kg SiC provides you 34 kg RHA equivalent protection (what I said earlier).

 

But I think your interpreation about TE is not consistent with the table’ statement. See your example:

 

we have a „material X” with 2 ME and 25% densitiy of the steel (around 2 g/cm3)

so, to reach 200kg RHA equivalent protection we need 200/2=100kg of „material X”. But if our 200kg RHA plate is 100mm thick (it means it is roughly a 100mm*500mm*500mm steel plate) we need 200mm of „material X”, which gives us TE=0.5.

But substitue the values of the SiC (0.34 ME, and 0.9 TE, density ratio=3/7.85~0.38):

200/0.34=588 kg and you can reach this value if you use a 770mm(*500mm*500mm) thick plate. Which gives us 100/770~0.13 TE.

 

According to your interpretation the TE=ME/density ratio, where density ratio=steel/material X

But in the table the TE=ME/(1/density ratio)!

Let’ see the STEF: it has a density ratio 7.85/2=3.925. Let’ take my equation TE=ME/(1/density ratio)=0.63/(1/3.925)=~2.45, as in the table

 

2 hours ago, SH_MM said:

 

I am not sure what these excerpts from Russian and Polish documents say, as I can only use a translator to understand them. But it seems that these are not directly ME and TE, but rather coefficients showing how much mass/thickness compared to steel is needed to provide the same level of protection. It is clearly not TE/ME in case of the Polish document, as this lists polyethylene (i.e. simple plastic) in an array with steel plates with a "thickness cofficient" of 7.1 against APFSDS rounds. As steel + polyethylene does not provide ~7 times the protection for a given thickness (nor does it allow reducing armor thickness significantly compared to pure steel), I would rather assume that this means something along the line of "a polyethylene array with preceeding steel plates need to have 7.1 times the thickness to provide the same protection as a simple steel plate".

 

don't get me wrong i don't think armor developers are stupid. I simply do not understand how, based on the given table, it comes out that it is worth using ceramics in the armor. But if I understand correctly what you say, these values are not  "actual" TE and ME values. But don't you know how much I argued on other forums, typically with Russian tank fans, who, typically based on such misinterpreted tables, always wanted to conclude that Russian tanks are the "kings"

 

2 hours ago, SH_MM said:

 

 

.... further increased by using a higher purity ceramic, a higher strength backplate....

 

 

based on this, is it possible that in the Leopard2 "D"-tech armor the steel backplate of the ceramic "sandwiches" changed to the "mysterious" wolfram-titanium alloy?

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2 hours ago, speziale said:

I think our interpreation is same in the case of ME. According to your interpretaion 100/0.34~295 kg SiC do you need to reach the same level of protection of 100 kg RHA. But this statement is equal with that 100kg SiC provides you 34 kg RHA equivalent protection (what I said earlier).

 

The issue here is that the documents do not use the same definition of mass efficiency as we do. The mass efficiency of silicon carbide is not 0.34, it is much higher. The documents use weight coefficients based on a different criteria (probably something that was established back in the Warsaw Pact).

 

3 hours ago, speziale said:

don't get me wrong i don't think armor developers are stupid. I simply do not understand how, based on the given table, it comes out that it is worth using ceramics in the armor.

 

You are interpreting the table wrong; otherwise every tank would be made out of polyethylene - providing 7 times as much protection as steel per weight and having a "TE" of 1.

 

3 hours ago, speziale said:

based on this, is it possible that in the Leopard2 "D"-tech armor the steel backplate of the ceramic "sandwiches" changed to the "mysterious" wolfram-titanium alloy?

 

A lot of things are possible, without any more detailed information we can only randomly speculate.

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39 minutes ago, SH_MM said:

 

The issue here is that the documents do not use the same definition of mass efficiency as we do. The mass efficiency of silicon carbide is not 0.34, it is much higher. The documents use weight coefficients based on a different criteria (probably something that was established back in the Warsaw Pact).

 

 

You are interpreting the table wrong; otherwise every tank would be made out of polyethylene - providing 7 times as much protection as steel per weight and having a "TE" of 1.

 

 

A lot of things are possible, without any more detailed information we can only randomly speculate.

 

Ok. Understood.

 

BTW I found a paper about the ceramic armor which claims around 5 ME coefficient (against handheld weapons' bullets).

 

https://patents.google.com/patent/WO2002068373A2

 

imgf000036_0001.png

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18 hours ago, speziale said:

 

Sorry, if my question will be stupid, but this table suggests there is no better armor material than the "good old" steel.

 

According to my understanding ME efficiency shows the armor efficiency when we keep the plate' thickness constant, and TE efficiency shows the armor efficiency when we keep the late' mass constant.

Take an example:

in the case of SiC a 20mm plate has a 20*0.34=6.8mm protection. In the case of TE efficiency 20*(7.85/3)=52.2mm thick plate has a same mass than a 20mm steel plate. 52.2*0.34~18mm which gives us 18/20=0.9 TE coefficient

 

So, why the hell makes anybody armor out of anything other than steel? Especially if we take into the account that HHS gives us around 1.1 ME/TE coefficient.

 

Is it possible that use a backing plate and appropriate interlayer material in a structure something like this, improves the ceremics' performance drastically?

Or just me understand wrong something int he abovementioned table?

 

SovSzmm.jpg


One thing that I do know is that the materials, and how they react/interact with the projectile, can also interact with other materials in the armor. The easiest armor to see this is reactive armors (explosive reactive or non explosive): the inter layer of rubber or explosive is often a terrible armor material in its own right, but it’s effects on the other layers in the array cause both ERA and NERA to be nearly ubiquitous today. This is a more niche and simple example than some of the interactions that may or may not go on with these other materials, but I use it as a precedent for how all the layers in a complex array work with one another. 
 

Another example I can think of is the XM60’s silica filled front plates, or Russian STEF sandwiches. Both silica and STEF (fiberglass) are poor for large kinetic projectiles, but they have some beneficial properties when combined as such, even if their raw ME or TE numbers are not impressive. 

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21 hours ago, Lord_James said:


One thing that I do know is that the materials, and how they react/interact with the projectile, can also interact with other materials in the armor. The easiest armor to see this is reactive armors (explosive reactive or non explosive): the inter layer of rubber or explosive is often a terrible armor material in its own right, but it’s effects on the other layers in the array cause both ERA and NERA to be nearly ubiquitous today. This is a more niche and simple example than some of the interactions that may or may not go on with these other materials, but I use it as a precedent for how all the layers in a complex array work with one another. 
 

Another example I can think of is the XM60’s silica filled front plates, or Russian STEF sandwiches. Both silica and STEF (fiberglass) are poor for large kinetic projectiles, but they have some beneficial properties when combined as such, even if their raw ME or TE numbers are not impressive. 

 

Interesting thing about the STEF, when the soviets tested the 60-105-50 array against the Hetz, they were extremely surprised when the Hetz perforated this array from 2km. Hetz has around a (nominal) 130mm perforation at 2km against a target sloped at 68 deg. It means, the STEF worths almost nothing against the Hetz. Especially, if we take into the account tht 60-105-array in its own (without STEF) act as a spaced armor, which gives around 10% high protection than if it would be a simple 110mm steel plate. So, it gives us, that 105mm STEF delivered only 8-10mm RHA protection against the Hetz. 105mm STEF' weight is equal around 27mm RHA, so it gives us the ME coefficient could be in the 0.3-0.35 range

 

But in the T-80BV/U glacis soviets used a 50-35-50-35-50 array, which gives around (nominal) 200mm protection. So, even if we take into the account that 50-50-50 array act as a spaced armor which gives around 10% higher protection we get the 70mm STEF gives around 30mm RHA protection against long rod penetrator. 70mm STEF' weight is equal around 18mm RHA, so it implies ME coefficient could be around 1.6-1.7.

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3 minutes ago, speziale said:

Interesting thing about the STEF, when the soviets tested the 60-105-50 array against the Hetz, they were extremely surprised when the Hetz perforated this array from 2km.

 

No, Hetz did not defeat the Soviet glacis armor array at 2,000 metres and specifically not the improved armor array (with 60 mm front plate and 50 mm back plate) of the T-72A. It could defeat the original array (80 mm steel, 105 mm STEF, 20 mm steel backplate) at shorter ranges.

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36 minutes ago, SH_MM said:

 

No, Hetz did not defeat the Soviet glacis armor array at 2,000 metres and specifically not the improved armor array (with 60 mm front plate and 50 mm back plate) of the T-72A. It could defeat the original array (80 mm steel, 105 mm STEF, 20 mm steel backplate) at shorter ranges.

 

Both this article and Mikhail Rastopshin in this article stated that it can.

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On 10/21/2022 at 8:55 PM, watch_your_fire said:

Can I get a summary of what these graphs show?

 

The 28-77 means the aspect of the armor' layers. I mean, in the case of 60-105-50 armor the total thickness of the array is 215mm. So, the aspects are 60/215~0.279 and (60+105)/215~0.77

The charts below that show some parameters' dvelopment in the certain layers.

Neither me know what are on charts in every cases. But, the charts labelled with "V" and "L" are the velocity and lenght.

So, you can see, that in the case of the 60-105-50 armor there is no velocity drop and length erodation in the middle STEF layer.

 

But, in the case of the 5layers armor (50-35-50-35-50; T80BV and T80U), in the first STEF layer there is some velocity drop and some length erodation. In the second STEF layer there is no lenght erodation but there is a significant velocity drop, which resulted in significant lenght erodation in the last steel layer.

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