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Did sandbags on Shermans do anything?


sevich

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Completely ignoring the formulae which Brone provided, I slapped together an Excel worksheet to do the calculations using the simplified formula.

 

Using solver seems to show that gravel and concrete applique will always result in a worse areal density than steel when faced with WW2-style HEAT warheads.

 

Which is actually a bit odd, given that so many materials provide better density efficiency against HEAT in the present day. It does seem to accord with the idea that slapping surplus armour plate onto the front of a sherman was a better idea than adding sandbags or concrete.

 

I wish the simplified model paper provided material coefficients for more than a few materials, so I could test this out a bit.

 

 

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1 hour ago, Bronezhilet said:

 

Does this help?

 

Also, this is probably a thing with sand barriers as well:

78024f4cb0.png

 

This was actually very useful.

 

The simplified model I'm using is about 80% accurate for the results obtained with dry soil.

 

The parameters are:

Phi (5' warhead): 127

k1 (WW2 warhead): 5

k2 (soil): 1

k2 (steel): 0.3

pTarget (soil): 1600

pTarget (steel): 7850

pJet (copper liner): 8960 

 

Formula:

2dTgQL7.jpg

 

Edit: the spreadsheet runs the penetration of the jet in the applique layer (soil in this case), then determines a residual penetration ratio based on the applique thickness/total penetration depth. This ratio is then applied to the penetration thickness of the target (steel in this case) to get the residual penetration depth.

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On 6/12/2017 at 1:35 AM, roguetechie said:

One question I've always had is whether there's anything resembling a "focal point" with HEAT type warheads...

 

What I mean by this is can you engineer them with a sort of optimal penetrative depth to where the jet or EFP starts to spread out just as it's getting into the crew compartment of what you're intending to kill with a particular product?

 

If I wasn't on watch lists before... I am now, but I really want to know.

 

I don't believe you could get it to work that way.

 

As I understand it, a shaped charge jet isn't like light being bent through a lens, coming to a focal point, and then spreading outwards again.

 

The reason that the jet spreads out is that different parts of the jet are moving at different velocities, so the jet stretches out and breaks up if given enough room.  Improvements in shaped charge design over the years have meant that the jets hold together over much greater distances than they used to, however.

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4 hours ago, roguetechie said:

That seems like a pretty reasonable explanation to me, thank you.

 

The extent of my knowledge about shaped charges EFP & HEAT rounds is that they don't work the way the TV explanations say they do.

 

 

Yes; most of the popular stuff is absolute rubbish.  For the low, low price of not quite a kilobuck, you too could own an introductory textbook on how these things work!

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8 hours ago, Collimatrix said:

 

I don't believe you could get it to work that way.

 

As I understand it, a shaped charge jet isn't like light being bent through a lens, coming to a focal point, and then spreading outwards again.

 

The reason that the jet spreads out is that different parts of the jet are moving at different velocities, so the jet stretches out and breaks up if given enough room.  Improvements in shaped charge design over the years have meant that the jets hold together over much greater distances than they used to, however.

Actually, you can if you can control the breaking up of the jet. Yesterday I found a paper which had simulations of the penetration of a segmented jet, but I can't find it anymore. :(

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3 hours ago, Collimatrix said:

 

 

Yes; most of the popular stuff is absolute rubbish.  For the low, low price of not quite a kilobuck, you too could own an introductory textbook on how these things work!

I suspect that there was active disinformation about how shaped charges work at some point, which has subsequently seeped into the general knowledge about them.

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