Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 14 users online :: 3 registered, 0 hidden and 11 guests


Most users ever online was 106 on Sat Jun 14, 2014 4:35 pm

Registered users: Bing [Bot], Google [Bot], Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Penatration, and what causes it.

A place to ask general spud cannon related questions.
Sponsored 
  • Author
    Message

Penatration, and what causes it.

Unread postAuthor: LucyInTheSky » Tue Apr 17, 2007 6:03 am

Is it the momentum or the kenetic energy that penetrates?

I know its the momentum thats the recoil and the blasting back of the victum but what is the penetration decided by?

For example if a bullet was 0.01kg and traveling at 1000m/s it would have the KE of 5000J and momentum of 10kg m/s.

So would a car with a metal pole the same area of a bullet sticking out the front of it panetrate the same as the bullet if it drove into something at (its mass is 1000kg):
3.16m/s as it would have the same KE
or
0.01m/s as it would have the same momentum.

I was thinking it may be the KE, and even further the J/cm^2.
However this could even be true for kg-m/s-/cm^2 (but thats pretty long).

Thanks for answering.
  • 0

If your getting chased off a police dog, try not to run through a tunnel then onto a small see-saw then through a ring of fire. They are trained for that!
User avatar
LucyInTheSky
1st Lieutenant
1st Lieutenant
 
Posts: 293
Joined: Fri Apr 21, 2006 11:46 am
Reputation: 0

Unread postAuthor: Hotwired » Tue Apr 17, 2007 6:26 am

  • 0

User avatar
Hotwired
Lieutenant General
Lieutenant General
 
Posts: 2598
Joined: Fri Oct 13, 2006 5:51 am
Location: UK
Reputation: 0

Unread postAuthor: LucyInTheSky » Tue Apr 17, 2007 6:33 am

Thanks for that Hotwired it was intressting and did state how the kinetic enrgy is the dangerous thing, but didnt mention penetration.

Cheers.
  • 0

If your getting chased off a police dog, try not to run through a tunnel then onto a small see-saw then through a ring of fire. They are trained for that!
User avatar
LucyInTheSky
1st Lieutenant
1st Lieutenant
 
Posts: 293
Joined: Fri Apr 21, 2006 11:46 am
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Tue Apr 17, 2007 7:03 am

Penetration is a function of many things. If there's one area of research where the search for better penetration is most intense, it's in the field of anti-tank weapons, namely those that function mechanically as opposed to relying on explosives.

Let's take a state of the art projectile as an example, here's a 125mm APFSDS round:

Image

In order to achieve optimal penetration, the following parameters are important:

1) high velocity - if a projectile travels slowly, the target will have time to deform and absorb the blow without penetration, and therefore in order to penetrate well you need as high a velocity as possible. A typical anti-tank round is travelling at around 5,000 fps.

2) high sectional density - in order to maintain its momentum, and transfer the energy in a concentrated manner, you need a projectile that is as heavy and narrow as possible - this is why APFSDS rounds are made of very dense materials such as tungsten or depleted uranium, which being long and thin to give the distinctive arrow shape.

3) high projectile hardness - nature will always choose the path of least resistance, so if the target material is tougher than the projectile, the impact energy will go towards shattering or deforming the projectile as opposed to the target.

edit: fixed illustration

edit 2: again...
  • 0

Last edited by jackssmirkingrevenge on Thu Mar 22, 2012 11:20 pm, edited 3 times in total.
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 23940
Joined: Thu Mar 15, 2007 11:28 pm
Location: epoxy batcave
Reputation: 50

Unread postAuthor: flameray » Tue Apr 17, 2007 7:07 am

Just a quick physics lesson.

Kinetic energy does play a major role in penetration, however the main penetration power comes directly from the surface area of the projectile.

Eg If you shoot a sharpened bullet (low surface energy to Kinetic energy ratio), it will penetrate a lot more than a flat potato (higher surface energy to Kinetic energy ratio)

Hope that helps
  • 0


flameray
Private
Private
 
Posts: 5
Joined: Sun Mar 25, 2007 6:36 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Tue Apr 17, 2007 7:18 am

A simple comparison is to look at typical airguns in the UK, which are legally limited to the same kintetic energy of 12 ft/lbs.

A typical 0.22 pellet weighing 16 grains travels at 581 fps for 12 ft/lbs.

A typical 0.177 pellet weighing 8 grains travels at 822 fps for 12 ft/lbs.

The 0.177 pellet only has 70% of the momentum of the 0.22 pellet, but will penetrate further by virtue of its higher velocity and smaller diameter.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 23940
Joined: Thu Mar 15, 2007 11:28 pm
Location: epoxy batcave
Reputation: 50

Unread postAuthor: LucyInTheSky » Tue Apr 17, 2007 7:31 am

Ok thanks guys,

So can we conclude that the main factor in penetration is J/cm^?
  • 0

If your getting chased off a police dog, try not to run through a tunnel then onto a small see-saw then through a ring of fire. They are trained for that!
User avatar
LucyInTheSky
1st Lieutenant
1st Lieutenant
 
Posts: 293
Joined: Fri Apr 21, 2006 11:46 am
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: Hotwired » Tue Apr 17, 2007 7:36 am

Pretty much.

1000J on a 0.1cm3 area is a better penetrator than 1000J on 1.0cm3 after all.
  • 0

User avatar
Hotwired
Lieutenant General
Lieutenant General
 
Posts: 2598
Joined: Fri Oct 13, 2006 5:51 am
Location: UK
Reputation: 0

Unread postAuthor: From_Hamsterdam » Tue Apr 17, 2007 7:54 am

More force over a smaller area has the most influence on penetration.

But also hardness plays a part in penetration. A pure lead slug might dent a steel plate, but a lead slug with a tool steel tip mill have more penetration. This is a more important in more powerful weapons.

This can be seen in tungsten tipped bullets and steel cored bullets(a steel rod inside a normal bullet).
  • 0


From_Hamsterdam
Staff Sergeant
Staff Sergeant
 
Posts: 110
Joined: Thu Feb 15, 2007 8:26 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Tue Apr 17, 2007 8:50 am

LucyInTheSky wrote:So can we conclude that the main factor in penetration is J/cm^?


It's a sum of all the factors I mentioned above case in point:

1000J on a 0.1cm2 area is a better penetrator than 1000J on 1.0cm2 after all.


Not necessarily;

1000J on a 1.0cm<sup>2</sup> area delivered suddenly by a hard projectile will penetrate more than 1000J on a 0.1cm<sup>2</sup> delivered slowly by a soft projectile.
  • 0

Last edited by jackssmirkingrevenge on Tue Apr 17, 2007 11:51 am, edited 1 time in total.
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 23940
Joined: Thu Mar 15, 2007 11:28 pm
Location: epoxy batcave
Reputation: 50

Unread postAuthor: Hotwired » Tue Apr 17, 2007 9:02 am

In equal scenarios which I expected it to be taken as then my point is true.

I'm aware a good penetrating projectile is hard, dense, thin, long, fast, and stabilised but that had already been posted.
  • 0

User avatar
Hotwired
Lieutenant General
Lieutenant General
 
Posts: 2598
Joined: Fri Oct 13, 2006 5:51 am
Location: UK
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Tue Apr 17, 2007 9:05 am

With all other factors being equal, then your statement is correct, but given the fact that there are so many other variables involved that can equally affect penetration in a drastic manner, it's a bit of a sweeping statement to say that J/cm<sup>2</sup> is the major factor involved.
  • 0

Last edited by jackssmirkingrevenge on Tue Apr 17, 2007 11:52 am, edited 1 time in total.
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 23940
Joined: Thu Mar 15, 2007 11:28 pm
Location: epoxy batcave
Reputation: 50

Unread postAuthor: Solo » Tue Apr 17, 2007 9:20 am

yeah, this is a good topic, it's something I've been wondering about. If you look at it from an energy perspective, you have KE=1/2*m*v^2. Then you also have E=f*d. So the higher your energy is, and the less force your projectile has to produce to penetrate (ie, make it sharp and keep the diameter down) the deeper it penetrates. So a high sectional density is defintely one of the keys. Which is what makes the arrow such a neat projectile: the old cultures were really onto something! Achieving aerodynamic stabilization and high sectional density all in one.

Heh, yeah, soft projectiles don't penetrate as well, for sure. A potato slug from my N-3 will go through 4 aluminum drink cans, but a marble takes out 10 and keeps right on plowing. (The potato really tore those 4 cans up, though.)
  • 0

User avatar
Solo
Private First Class
Private First Class
 
Posts: 33
Joined: Fri Jan 05, 2007 10:45 am
Reputation: 0

Unread postAuthor: joannaardway » Tue Apr 17, 2007 9:22 am

I hate to tell you this, but area is measured in square centimetres, not cubic centimetres.

I'm of the opinion that the factor involved in damage is really pressure on the target. (Not air pressure of course)
This can be figured by dividing momentum by impact time and cross-sectional area.

Essentially this is in proportion to J/cm^2, with a constant defined by target and projectile hardness.
  • 0

Novacastrian: How about use whatever the heck you can get your hands on?
frankrede: Well then I guess it won't matter when you decide to drink bleach because your out of kool-aid.
...I'm sorry, but that made my year.
User avatar
joannaardway
Brigadier General
Brigadier General
 
Posts: 949
Joined: Mon Oct 09, 2006 4:57 pm
Location: SW Hertfordshire, England, UK.
Reputation: 0

Unread postAuthor: Hotwired » Tue Apr 17, 2007 9:24 am

:P

We all make mistakes and unless others are concentrating they copy them too :wink:
  • 0

User avatar
Hotwired
Lieutenant General
Lieutenant General
 
Posts: 2598
Joined: Fri Oct 13, 2006 5:51 am
Location: UK
Reputation: 0

Next

Return to General Spud Cannon Related

Who is online

Registered users: Bing [Bot], Google [Bot], Yahoo [Bot]

Reputation System ©'