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muddmaster (Automotive) (OP)
14 Jul 06 9:55
Hello!

I am a new user to this forum, but have seen many great posts here in the past.  I am hoping that one of the many experts may be able to help me out too.

I am looking for specific material information on a military grade steel: MIL-A-46100.

I recognize the difficulty of this request, since this grade is a ballistics requirement, and not an explicit strength / strain requirement.  However, I am looking to use this material in an explicit software, in which I need to know specific material properties and failure modes.

I would like to represent this material using the Johnson Cook material model and damage model.  Does anyone have, or know where I could get, J-C data for steel with this specification?  Or, I would be satisfied with true stress-strain curves in tension and torsional loading, from which I think I can extract the J-C parameters myself.

Thanks in advance,
Nick
Helpful Member!(3)  TVP (Materials)
14 Jul 06 12:28
Johnson-Cook parameters for Rolled Homogeneous Armor are as follows:

A = 0.7922
B = 0.595
C = 0.014
n = 0.26
m = 1.03

Sources for this information can be found by using a search engine such as Scirus:

http://www.scirus.com/srsapp/search?q=Johnson+Cook+armor+steel&ds=jnl&ds=nom&ds=web&g=s&t=all
muddmaster (Automotive) (OP)
14 Jul 06 14:26
Thank you for your quick response!

I was not aware of the Scirus search engine, but I can now see it is extremely valuable.

After reading some of the references you cited, I have a further question:

How do these J-C parameters vary between grades of steel?

I see that most of these references are citing an RHA steel - but what designation.  Most of the papers (including the one you cited above) refer to J-C parameters that are typical for a 4340 steel.  Does this mean that RHA ~ 4340?

One of the references in particular, lists the constants for an RHA (MIL-A-12560), and in this case the parameters are somewhat different from the ones you've listed above (Rajendran, 1998, "Penetration of Tungsten Alloy Rods into Shallow-Cavity Steel targets")

Furthermore, another reference causally indicates that to modify the J-C parameters between Rc30 to Rc37, one simply multiplies the A and B constants by 1.5.  Where does this relationship come from, what does it mean, and is it accurate?  (Anderson, 1999, "Hydrodynamic Approximation for Long-Rod Penetration")

Thank you again for your support
I look forward to your next reply

Nick

TVP (Materials)
14 Jul 06 15:25
Nick,

J-C parameters will vary depending on the composition, processing, and subsequent microstructure of the steel.  If you are not already aware of it, this type of data is extremely rare, and requires a great deal of testing to acquire.  This means that this data does not really exist out in the public domain.

Regarding RHA, it is not the same as SAE 4340.  The MIL standard shows the chemical composition for RHA, which has a lower range of carbon than 4340, among other differences.  You can find the composition of 4340 on Matweb or other any number of other sites.

I am not an expert on large strain/large strain rate deformation, and therefore I have no idea what the answers are to your last three questions.  The people that are experts on this type of analysis generally fall into two categories: researchers working on metal forming and machining applications or scientists/engineers working for the United States government at national labs that specialize in weapons testing and modelling.  I suggest you obtain some references on the subject for more information, such as those from the Scirus search.
muddmaster (Automotive) (OP)
14 Jul 06 15:36
Thank you again for your reply.
I appreciate your feedback, and will continue to seek other references from Scirus...

If in the future you happen across any of the data I was interested in, I'd appreciate it if you could let me know.

Thanks
Have a great weekend!

Nick
CoryPad (Materials)
14 Jul 06 16:05
Talk about needle-in-a-haystack request!  Since this is your first posting to this site, I will give you some advice: when you get an answer to an almost impossible question within 2.5 hours, you should click the link "Thank TVP for this valuable post!".

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

muddmaster (Automotive) (OP)
14 Jul 06 16:12
Thanks CoryPad for the suggestion...
Already did that - twice :)

and yeah, i knew it was an oddball request - It seems like I've looked everywhere for this information - if you have any other suggestions on where to look, I'm all ears :)

Have a good weekend
Nick
CoryPad (Materials)
15 Jul 06 14:45
Apparently you were unsuccessful, as no stars appear on this thread.  If you click the first link, it pops up a box asking if you are sure.  Maybe you don't see those (I think they use JavaScript).

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

muddmaster (Automotive) (OP)
17 Jul 06 8:06
Aha!,Thanks Cory
I hadn't seen the popup before - I got it now

Thanks again to Cory and TVP for their suggestions!

Have a great day all!

Nick

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