## Question about Steel and Aluminium

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Hi guys, need some help here regarding a physics question.

My question is if you can get a softer material to penetrate a harder one?

Assuming you have a steel wall, if you fire an aluminium bullet at it at different speeds, is there a point where the speed is great enough to penetrate the steel wall?
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Nando
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Joined: 10 Mar 2012

You can get a fast big wooden projectile to penetrate a thin steel sheet if you wanted.

What's the context? Perhaps machine tools or bearing surfaces in machinery might be more useful?
richard_leeds
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an example is a bullet a bullet is made of a relatively soft metal usually lead but can penetrate multiple sheets of aluminium
And so you touch this limit, something happens and you suddenly can go a little bit further. With your mind power, your determination, your instinct, and the experience as well, you can fly very high.
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AlpineF1
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well the germans used armor piercing missiles during ww2, it had a copper jet which pierced through a tanks armour
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N12ck
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Joined: 19 Dec 2010

Yea i understand if you had a paper thin steel sheet and a big cube of Aluminium you would eventually break it but if we assume the steel wall is 6cm thick?

Is there any way to calculate how much momentum an aluminium bullet would need in order to penetrate 6cm thick Steel?
"Il Phenomeno" - The one they fear the most!

"2% of the world's population own 50% of the world's wealth."
Nando
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Joined: 10 Mar 2012

N12ck wrote:well the germans used armor piercing missiles during ww2, it had a copper jet which pierced through a tanks armour

At what speeds did those missiles fly at? Mach 1, 2?
"Il Phenomeno" - The one they fear the most!

"2% of the world's population own 50% of the world's wealth."
Nando
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Joined: 10 Mar 2012

Nando wrote:
N12ck wrote:well the germans used armor piercing missiles during ww2, it had a copper jet which pierced through a tanks armour

At what speeds did those missiles fly at? Mach 1, 2?

I cant find any quoted figure, but the missile would be fired, and outside of the tank the missile would detonate, firing the copper jet at the armour and subsequently pierce it -note it is not the detonation which pierced the armour, but it was the copper travelling extremely fast
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N12ck
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Joined: 19 Dec 2010

N12ck wrote:
Nando wrote:
N12ck wrote:well the germans used armor piercing missiles during ww2, it had a copper jet which pierced through a tanks armour

At what speeds did those missiles fly at? Mach 1, 2?

I cant find any quoted figure, but the missile would be fired, and outside of the tank the missile would detonate, firing the copper jet at the armour and subsequently pierce it -note it is not the detonation which pierced the armour, but it was the copper travelling extremely fast

Just from a i guess ignorant point of view that makes no sense

You have a soft material which somehow, at some speed overcomes it´s weakness and overcomes the strength of the tank armor.

I know in modern times they use Tungsten or depleted uranium because you have to have a harder material or something that will pretty much melt through the armor.

I find this fascinating to say the least and i don´t understand how it can be done since it´s a softer material.

My brain tells me that if you have a softer material, take Copper, and shoot it towards a tank armor.
If you increase the speed it will only destroy the copper faster?

I´d like to know how and why it overcomes this purely on momentum.
"Il Phenomeno" - The one they fear the most!

"2% of the world's population own 50% of the world's wealth."
Nando
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Joined: 10 Mar 2012

I have gotta be honest, I don't understand it either, all I know is it exists,

quite possibly, maybe some partial melting my take place which may make it easier to penetrate would be my immediate guess,
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N12ck
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Joined: 19 Dec 2010

Its the same as a lump of wood thrown at a thin foil of metal. That is easy to imagine, and the other examples above are the same idea, ie lead bullet through steel sheet, or shrapnel through a helmet.

Don't forget there are also metallurgical factors beyond mere momentum, its not just something hard battering on something soft, I suspect that analogy is probably on valid for very simple things. You also need to factor in heat, shape of object, shape of projectile, and so on.

Here's a good place to start http://en.wikipedia.org/wiki/Armor-pier ... _and_shell

and here's one that only uses kinetic energy http://en.wikipedia.org/wiki/Kinetic_energy_penetrator
richard_leeds
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Joined: 15 Apr 2009
Location: UK

Edit: keep in mind we posted at the same time Richard.

That would explain some of it (N1ck)

Perhaps it´s like the depleted uranium. The Missile hits the tank, a trigger is "triggered" and due to the incredible forces the Copper heats up to insane temperatures that will melt it´s way through the tank armor.

Please anyone that could chime in on this? I´m actually asking all of this for a reason but fear of the thread being removed i will keep all of you in the dark so we can focus on physics and only physics.
"Il Phenomeno" - The one they fear the most!

"2% of the world's population own 50% of the world's wealth."
Nando
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Joined: 10 Mar 2012

It's off topic chat so feel free to ask your question, it would make a much better conversation than abstract generalities
richard_leeds
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Joined: 15 Apr 2009
Location: UK

richard_leeds wrote:Its the same as a lump of wood thrown at a thin foil of metal. That is easy to imagine, and the other examples above are the same idea, ie lead bullet through steel sheet, or shrapnel through a helmet.

Don't forget there are also metallurgical factors beyond mere momentum, its not just something hard battering on something soft, I suspect that analogy is probably on valid for very simple things. You also need to factor in heat, shape of object, shape of projectile, and so on.

Here's a good place to start http://en.wikipedia.org/wiki/Armor-pier ... _and_shell

and here's one that only uses kinetic energy http://en.wikipedia.org/wiki/Kinetic_energy_penetrator

"The opposite technique to KE-penetrators uses chemical energy penetrators.
There are two types of these shells in use: high explosive anti-tank (HEAT) and high explosive squash head (HESH).
They have been widely used against armour in the past and still have a role but are less effective against modern composite armour, such as Chobham or Kanchan, as used on main battle tanks today.

The principle of the kinetic energy penetrator is that it uses its kinetic energy, which is a function of mass and velocity, to force its way through armour. If the armor is defeated, the heat and spalling (particle spray) generated by the penetrator going through the armor, and the pressure wave that would develop, would destroy the target.[1]
The modern KE weapon maximizes KE and minimizes the area over which it is delivered by:
being fired with a very high muzzle velocity
concentrating the force in a small impact area while still retaining a relatively large mass
maximizing the mass of whatever (albeit small) volume is occupied by the projectile—that is, using the densest metals practical, which is one of the reasons depleted uranium is often used.
This has led to the current designs which resemble a long metal arrow."

So it seems they do indeed use the densest material they can find.
"Il Phenomeno" - The one they fear the most!

"2% of the world's population own 50% of the world's wealth."
Nando
14

Joined: 10 Mar 2012

Nando wrote:Edit: keep in mind we posted at the same time Richard.

That would explain some of it (N1ck)

Perhaps it´s like the depleted uranium. The Missile hits the tank, a trigger is "triggered" and due to the incredible forces the Copper heats up to insane temperatures that will melt it´s way through the tank armor.

Please anyone that could chime in on this? I´m actually asking all of this for a reason but fear of the thread being removed i will keep all of you in the dark so we can focus on physics and only physics.

I expect it is down to melting aswell, but note the melting is produced by the energy it has already, so its momentum, what is this reason? I am curious and interested
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N12ck
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Joined: 19 Dec 2010

richard_leeds wrote:It's off topic chat so feel free to ask your question, it would make a much better conversation than abstract generalities

Are you really sure, this can open up a Pandoras Box even if i don´t have any intention of doing so,

What i can do is present a video of this scenario, and then we can discuss if im thinking right?

The problem if i´m right is the pandoras box thing. It can get ugly. real ugly in fact.
"Il Phenomeno" - The one they fear the most!

"2% of the world's population own 50% of the world's wealth."
Nando
14

Joined: 10 Mar 2012

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