How effective is perforated steel armour against heat rounds?

[ramontxo]

I assume that the relative size of the holes versus the molted metal jet is relevant, but in general, does perforated steel works better than homogenous plate or worse against heat? As always thanks in advance to the far more learned

[TTK Ciar]

Deleted (Double-post)

Edited January 14, 2012 by TTK Ciar

[TTK Ciar]

I assume that the relative size of the holes versus the molted metal jet is relevant, but in general, does perforated steel works better than homogenous plate or worse against heat?

Regarding the metal jet, I strongly recommend you read Pike's article on shaped charges. Specifically:

it has been established by X-ray diffraction that the jet is solid metal and not molten

To my understanding, you are correct -- the ratio of penetrator diameter to aperture size is important. Perforated plate is effective because of the edge effect, as described in the paper Impact of the 7.62mm APM2 Projectile Against the Edge of a Metallic Target. If the penetrator hits between the apertures and strikes only steel, then the perforated steel plate is only as effective as steel (actually less, due to the free edge effect), and if the penetrator hits an aperture and misses the steel entirely, it of course passes through without being effected. It is when the penetrator strikes the boundry between the edge of the aperture and the edge of the steel that it is damaged by powerful internal shearing forces.

 

The penetrating tip of a HEAT jet is very small -- about 3% to 7% of cone diameter. This means a 75mm shaped charge might only produce a 4mm diameter penetrating jet. To assure that this jet hits an edge, the perforated steel plate would need 4mm apertures no more than 2.8mm apart. Apertures any larger would increase the probability that the jet would pass through a hole without interaction, and spacing the apertures any wider would increase the probability that the jet would hit only solid steel.

 

I don't know for certain, but I expect perforated steel components are most often optimized against long-rod penetrators, which are considerably larger (25mm typical diameter). So while there is a chance that a penetrating jet might hit an edge, it isn't very likely.

 

It's conceivable that someone might arrange a small-aperture perforated steel component in front of a large-aperture component, but this seems unlikely because the diversity of HEAT munitions would make optimizing aperture size and spacing difficult, and there are counters known to be more effective against shaped charge jets (ERA, NERA, EEA, ARENA/TROPHY-like interceptors, etc).

[Voyager]

...and there are counters known to be more effective against shaped charge jets (ERA, NERA, EEA, ARENA/TROPHY-like interceptors, etc).

 

Those underlined rather against HEAT weapons because Active Protection Systems goal is to destroy weapon/warhead before reaching target's armor.

[TTK Ciar]

Those underlined rather against HEAT weapons because Active Protection Systems goal is to destroy weapon/warhead before reaching target's armor.

Yes, exactly .. I should have worded that better.

[ramontxo]

Regarding the metal jet, I strongly recommend you read Pike's article on shaped charges. Specifically:

"it has been established by X-ray diffraction that the jet is solid metal and not molten"

 

 

To my understanding, you are correct -- the ratio of penetrator diameter to aperture size is important. Perforated plate is effective because of the edge effect, as described in the paper Impact of the 7.62mm APM2 Projectile Against the Edge of a Metallic Target. If the penetrator hits between the apertures and strikes only steel, then the perforated steel plate is only as effective as steel (actually less, due to the free edge effect), and if the penetrator hits an aperture and misses the steel entirely, it of course passes through without being effected. It is when the penetrator strikes the boundry between the edge of the aperture and the edge of the steel that it is damaged by powerful internal shearing forces.

 

The penetrating tip of a HEAT jet is very small -- about 3% to 7% of cone diameter. This means a 75mm shaped charge might only produce a 4mm diameter penetrating jet. To assure that this jet hits an edge, the perforated steel plate would need 4mm apertures no more than 2.8mm apart. Apertures any larger would increase the probability that the jet would pass through a hole without interaction, and spacing the apertures any wider would increase the probability that the jet would hit only solid steel.

 

I don't know for certain, but I expect perforated steel components are most often optimized against long-rod penetrators, which are considerably larger (25mm typical diameter). So while there is a chance that a penetrating jet might hit an edge, it isn't very likely.

 

It's conceivable that someone might arrange a small-aperture perforated steel component in front of a large-aperture component, but this seems unlikely because the diversity of HEAT munitions would make optimizing aperture size and spacing difficult, and there are counters known to be more effective against shaped charge jets (ERA, NERA, EEA, ARENA/TROPHY-like interceptors, etc).

Thanks, as always i learn a lot here (and for the very interesting link, 25 millions g ... )

Edited January 26, 2012 by ramontxo

[Sami Jumppanen]

The penetrating tip of a HEAT jet is very small -- about 3% to 7% of cone diameter. This means a 75mm shaped charge might only produce a 4mm diameter penetrating jet. To assure that this jet hits an edge, the perforated steel plate would need 4mm apertures no more than 2.8mm apart. Apertures any larger would increase the probability that the jet would pass through a hole without interaction, and spacing the apertures any wider would increase the probability that the jet would hit only solid steel.

 

 

I was thinking that the spacing of those apertures doesn't need to be optimised against penetration but more likely it would be mostly to save weight in some composite armour material. To put HEAT aside i was thinking that there could be maybe 2 layers in that armour and the first one would be the perforated plate and the second one would be thick enough that anything that might fit though the aperture is stopped. Not sure if those apertures would be effective against anything bigger in that case but maybe the size could be enlarged by sloping the plate.

 

I'm just tired and rambling...

[istvan47]

Anyway, Lao-Tse would be happy to hear that -even in a armour- the hollow matters. Just like in a HEAT charge, BTW: hollow vs hollow, who would win?