Ballistic Protection Value of Sloped Armor

Gentlemen,

Thanks to a lot of input from a lot of people on numerous websites I have received the documentation I need to pursue this topic some more.

I will post my results when I am finished.

Thanks for all of your help.

:smok:

 

Gents,

Have found a short version on ballistic protection value of sloped armor. Have conversed with the author and his soure is R.M. Ogorkiewicz as well.

http://homepage.ntlworld.com/paul.a.all ... s/mftw.htm

Enjoy!

:smok:

 

RMO work is always important especially the modern stuff, but the 'Armor ' books were written in the late 1980s [as I recall] so they are quite dated.

Penetration is dependant of projectile length, while resistance is dependant on ratio of plate thickness to projectile diameter. However armor thickness over a AFV aspect is constant requardless of slope. Inother words 45mm @ 60° is the same armor mass as 90mm @ 0°.On top of this the reaction of projectiles to the degree of slope is dependant on the projectile nose design and the projectile velocity as well as geometray [length over diameter or L/d ].

Modern flat nosed penetrators with L/d of 10:1 or more impacting above 1000m/s penetrate more slanted armor than vertical armor ,cause in addition to the nose digging in right away, the longer penetrator rotates a to the perpendicular upon entry and exit , thus following a 'S' shape. But the same penetrator with a sharp nose will end up penetrating about 10% more sloped armor than vertical armor due to the sliding action before the penetrator digs in.

The same penetration with a shorter rod [3:1 L/d IE APC ] would be effected mosly by the sliding , rotating and exiting phases. Thus flat nose penetrators are almost as good at penetrating slanted armor as vertical , while sharp penetrators are really poor against slanted armor compared to vertical plates.

 

Paul,

If you can offer up some good source mateial on this I would really appreciate it. The discussion has been on WW2 armor and weapons, not modern. The books were actually written in the 60's, and RMO has done a lot since then of course.

Since the laws of physics do not change however, you have got my interest when you say "quite dated".

Thanks!

:smok:

 

http://www.ciar.org/ttk/mbt/

You can try the following source since I've uploaded a ton of ballistics papers there and just sent another 20-30 or more. Theirs enough material their to last years of studying. Also you should join the "Tankers Yahoo site" if you wish to speak to Lorrin and Robert directly.

While you are right the laws of physics don't change but many other things have like testing criteria and recording . For example many tests in the past featured multiple penetrations within the same plate.Test criteria demanded a minimum distance between penetrations to be considerd valid. Today with the same weapons you will never find more than one impact per test plate.Studies on the effects of reflecting waves have shown that armored plates are badly weakened in such instances with increasing effects. So with APFSDS it seems that you need single test plates atleast 30-50 times the rod diameter. WIth AP/APDS level impacts it appears that 10-20 times projectile diameter is sufficent.

In past standard measurment was perforation velocity. This means the velocity to achieve penetration of a plate.Criteria surrounded what percentage number of complete or partial penetrations would satisfy requirements. If you have read Bird and Livingston, you will know that Russians used certified penetration [80% of impacts must result in perforation of the plate] and inital penetration [20% of impacts must result in perforation] ..others used the 50% ballistic limit velocity.

These are not the perfered measurement in modern tests. Modern tests of APC/APDS/APFSDS/HEAT use residual penetration measurements. A semi infinite target is penetrated to the maxium for given velocity. Then a series of targets is placed infront of this type of reference plate and the residual penetration is measured and compared. The difference is assigned to the test plate.Semi infinite reference plate is used since its are very stable and easly compareable to other similar results.


It seems that it is much easier to measure post penetration performance based on residual penetration results as opposed to perforation velocities.

 

Thanks Paul,

I have downloaded numerous articles and will sort through them. I do hope however that the authors list their source material. I will want the books in my library, specifically those that relate to WW2 weapons and armor, and those with formula's for computation.

Do you have any resources that show ammunition type and availability by nation for WW2 (tank weapons). Also, I am looking for more good source information on penetration ability of each tank weapon by ammo type, by nationality. I have a lot of this but want more as there are conflicts in data.

I see you have run on a Unix platform. I really miss it. Ran on a Unix for years at work for statistical analysis. I am not in that field anymore as I got away from "Corporate America". Sure wish I had our setup though.

Can you give me the website address for the Yahoo group?

:smok:

 

Problem is these are scientific papers not Academic papers, so you won't find much in the way of books [too new] . You might try Jonas Zukas as an author . He has two good books on High velocity impact dynamics.

Check out the Yahoos site in the file section. I down loaded drawings of soviet penetrators during the war, and others supplied what they could find ....you have to join Yahoos first to join the group.

http://groups.yahoo.com/group/tankers/?yguid=10875364

Just to be clear this site is TTK Ciars site and he allows me to upload material from time to time.

 

I have looked over TB19, TB 11, 12, 14, & 25 and the scope of the assessment is too narrow for my needs. They are primarily dealing with tungsten core projectiles.

The docs so far certainly do not address standard types of ammo used in WW2, not do I see anything of value for WW2 types of armor and weapons.

Still, it is obvious the gents know their stuff and I will have to spend more time going over the docs.

:smok:

 

Enjoy Gentlemen. While my time restraints does not allow me time to go into detail, I wanted to share this image with you. I think that a number of you will find it interesting and informational.

Source: R. M. Ogorkiewicz

Have fun!

:smok: [/img]

 

I have been told that the effect of sloped armour varies depending on the type of round hitting it. Sloped armour is effective against normal armour piercing rounds but the effect is decreased when using capped armour piercing rounds or hollow charges.

I have no sources to back this up, I am only looking for a comment.

 

Absolutely correct. That is why you see me asking some people "what type" of ammo are they quoting when they list penetration stats.

Shaped charge ammo is only concerned with the "actual" thickness of the armor, not effective. Christian A. gave a website with the info on this.

APBC ammo is slightly more effective against sloped armor than regular AP. One can simply look at known penetration curves for APBC and Std. AP to see how much more so. The sloped armor still has its effect as listed above on the chart, but you will see when looking at penetration curves, that the APBC does in fact penetrate more armor.

APBC is more effective against "face hardened" armor as well but unfortunately, I do not have any reliable data that shows how much so by weapon type.

:smok:

 

Thanks.

I noticed, when reading through the thread, that I have asked a similar question before. But hey, nothing wrong in reviving this topic.

 

Hi guys, and especially Greg. Joined yesterday, and just trolling through and replying to whatever grabs me.
Thanks for the quot Greg. That site is no longer active and I'm now moving (slowly) to http://www.cybamall.com/oli/home.html.
All my stuff sill get put there.
As for pentration being dependant upon pentrator length - not so much in WWII, but more with APFSDS rounds. I have about a dozen different formulae, all by "professional experts" and mostly incomptible:
one is purely dependant upon energy, one upon relative densities, the one on my old site, and Lanz-Odermatt. All of these will be sifted through and worked into another paper.
I think the best illustration I can give is from a trip to Farnbourough many years ago:
Royal Ordnance Factories had a stand with APFSDS rounds that I kept visiting, when they asked why I kept going back I told them that in my opinion something looked wrong with the rounds.
"Correct", they said, "these are public viewing dummies, some details are altered" "Ok, what's the real thing look like?" I asked.
The reply was a simple laugh and the comment "Piss off".
IMHO ANYTHING in an open source is bound to be incomplete, incorrect or misinformation, and like Bill Sweetman said in his book about Stealth, "a writer needs access to classified material like a duck needs a bicycle" - if classified stuff even confirms what you've worked out you can't publish it! :kill:
Oli