Define EOS in LS-DY...
 
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Define EOS in LS-DYNA

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Posts: 3
 LuBo
Topic starter
(@lubo)
Unpaid Intern
Joined: 1 year ago

Hello everyone,

I would like to implement a standard tensile test using Johnson Cook damage mechanics. I have to specify EOS for the MAT 15 Johnson Cook material. I do not understand exactly why I have to specify this so precisely. Can someone explain this to me? Do I understand correctly that this represents the denominator in the triaxiality formula for plastic strain? But with steel, the volume does not change plastically during a tensile test?

And what EOS do I specify for this if I want to simulate an S500, S700, S770 and S960 Steel? Where can I find parameters in this Case?

Thank you very much who can help me here in my desperate search.

 

Best Regards Luise

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Posts: 37
(@geardyn-1)
Lab Tech
Joined: 5 years ago

hi LuBo,

An equation of state (EOS) is equivalent a fluid model. Specifically, an EOS is a fluid model that takes a molar composition (z) and predicts the phase and volumetric behavior of the fluid (e.g. densities, viscosities and formation volume factors) over a wide range of pressure (p) and temperature (T).

in your case for high velocity projectile impact , the projectile after impact undegoes phase change and at the region of impact the material behaves as fluid . to effectively capture this phenomenon and the damage EOS must be used. for low velocity and static analysis there is no use of EOS. 

For the values of EOS , search for the publication from Tore Borvik . The author has published numerous research using the mentioned materials.

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Posts: 3
 LuBo
Topic starter
(@lubo)
Unpaid Intern
Joined: 1 year ago

Thanks a lot for your Answer!!

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Negative Volume
Posts: 641
Admin
(@negativevolume)
CEO
Joined: 5 years ago

I know this was a few months ago but @lubo could also try using simplified Johnson-Cook Mat 98 or tabulated johnson-cook Mat_224. 

James Kennedy puts together a good explanation here:

https://groups.google.com/g/ls-dyna2/c/J8Wwh5gUXHA?pli=1

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