ballistics

[deusexmachina]

Hi: To start off this is not a homework question.

Here is my problem and the info I have,it falls under physics and engineering.

 

you have a 6"x8" piece of Titanium 2.54mm thick. This piece of metal has dents in it from 1 to 25mm deep.

 

What I need is a chart that shows the amount of kinetic energy required by a projectile to make the deformation at the point of impact. I think this info should be available someplace but I dont know where to start looking. I am sure a formula exists to solve this but im not a engineer. I dont know what other info you need to solve this problem. The projectile will vary that is why I need a chart to find the minimum amount required given an amount of energy put in.

An exaple of a question is "can a projectile(with x amount of kenitic energy at point of impact) make a dent in titanium to (y) depth. I want to look at the chart and be able to say yes or no. I hope somebody can solve this or point me in the right direction. Thanks for all your help.

[InigoMontoya]

An exaple of a question is "can a projectile(with x amount of kenitic energy at point of impact) make a dent in titanium to (y) depth. I want to look at the chart and be able to say yes or no. I hope somebody can solve this or point me in the right direction. Thanks for all your help.

It's not that easy. Hardness of the projectile matters. Mass of the projectile matters. Sectional density of the projectile matters. Velocity of the projectile matters. LOTS of variables here.

 

And I don't just mean in the "mass and velocity determine energy" way. As one who used to play with armor for a living... I've seen light weight but very high energy projectiles fail to penetrate armor that was easily penetrated by much heaver but much lower energy projectiles. Energy is important. Yes. But so is momentum. Also note that differing velocities may yield different failure mechanics in your titanium plate which in turn affects deformation.

 

Blah blah blah. The point is that you're going to need to narrow the scope of your question to get a meaningful answer.

Edited February 16, 2011 by InigoMontoya

[deusexmachina]

Thanks for the reply: I will try to narrow this down .

The plate is a second chance T-15 trauma plate (titanium 2.54mm thick 6" x8' wide

the projectile will be from 1.74 gram to 2.59 gram in weight,no wider then a .226 cal no smaller them a .17 cal

with a muzzel velosity of 900 to 1500 FPS max

with energy = 85-150 ft.lbs max

made of lead or copper jacket(a bullet)

under 10 foot range

 

given theses paramaters can you dent the plate between 1 to 10 mm in depth I dont think this small of a projectile can even dent titanium and if so to what depth given limits?

I hope that clears it up a bit, what need is a comparason chart within margins of error. so I can look at it and say "ok a dent 10mm deep in this plate it can only be this type of bullet.or in this range of bullets"or somthing to that extent.

thanks again.

 

 

 

thanks for the answer i updated the info i hiope this helps a bit.

 

It's not that easy. Hardness of the projectile matters. Mass of the projectile matters. Sectional density of the projectile matters. Velocity of the projectile matters. LOTS of variables here.

 

And I don't just mean in the "mass and velocity determine energy" way. As one who used to play with armor for a living... I've seen light weight but very high energy projectiles fail to penetrate armor that was easily penetrated by much heaver but much lower energy projectiles. Energy is important. Yes. But so is momentum. Also note that differing velocities may yield different failure mechanics in your titanium plate which in turn affects deformation.

 

Blah blah blah. The point is that you're going to need to narrow the scope of your question to get a meaningful answer.

[InigoMontoya]

Within the bounds of your question, I've no idea. You're obviously interested in body armor and (I'm guessing) secondary fragments. Back when I played with armor I was interested in... Let's just say "larger systems and higher energy events" and leave it at that. The point being that my experience was far enough outside your parameters I simply have no gut feel for it.

 

That said, you do have a well bounded problem at low energy levels. Things should scale pretty nicely. I've no idea what your table will look like but I believe such a table could be made.

 

One thing to beware of... If I'm right about your interest being secondary fragments, you need to be aware that geometry will matter. By that I mean: Suppose you have a cube coming at you. Whether that cube hits face first, edge first, or corner first will matter. Extrapolate that statement as required.

[sound]

Hi: To start off this is not a homework question.

Here is my problem and the info I have,it falls under physics and engineering.

 

you have a 6"x8" piece of Titanium 2.54mm thick. This piece of metal has dents in it from 1 to 25mm deep.

 

What I need is a chart that shows the amount of kinetic energy required by a projectile to make the deformation at the point of impact. I think this info should be available someplace but I dont know where to start looking. I am sure a formula exists to solve this but im not a engineer. I dont know what other info you need to solve this problem. The projectile will vary that is why I need a chart to find the minimum amount required given an amount of energy put in.

An exaple of a question is "can a projectile(with x amount of kenitic energy at point of impact) make a dent in titanium to (y) depth. I want to look at the chart and be able to say yes or no. I hope somebody can solve this or point me in the right direction. Thanks for all your help.

can you be a little more specific how many dents does it have

[DrRocket]

Hi: To start off this is not a homework question.

Here is my problem and the info I have,it falls under physics and engineering.

 

you have a 6"x8" piece of Titanium 2.54mm thick. This piece of metal has dents in it from 1 to 25mm deep.

 

What I need is a chart that shows the amount of kinetic energy required by a projectile to make the deformation at the point of impact. I think this info should be available someplace but I dont know where to start looking. I am sure a formula exists to solve this but im not a engineer. I dont know what other info you need to solve this problem. The projectile will vary that is why I need a chart to find the minimum amount required given an amount of energy put in.

An exaple of a question is "can a projectile(with x amount of kenitic energy at point of impact) make a dent in titanium to (y) depth. I want to look at the chart and be able to say yes or no. I hope somebody can solve this or point me in the right direction. Thanks for all your help.

 

 

InigoMontoya is right, this is not any easy problem. Good penetration mechanics analysis requires sophisticated hydrocodes and very high rate naterials properties all implemented on high-end workstations. It is not some direct correlation between kinetic energy and dent depth or penetration.

 

That said. 2.54 mm (0.10 in) is not a very thick metal plate, and it should be easily penetrated by a bullet, enen a .22 at the modest velocities that you quote. The bullet weights and velocities that you quote suggest a .22 long rifle.

 

If what you are seeing is only a dent, then I would venture to guess that the bullet has lost a lot of energy and likely been deformed by the fabric, probably an aramid fiber like Kevlar, before it encounters the plate. Dent depth will be highly dependent of the the specific alloy and heat-treatment used which affect hardness, ductility and toughness.

 

As a practical matter, if it were me and I was getting that sort of response with a .22 rimfire, I would get a better vest -- or better yet avoid being shot. A bigger gun would probably be a serious threat.

[forufes]

easy.

check "Brinell's hardness test", it's the inverse of what you want. but it'll give you what you want pretty much directly.

yay i'm useful