HELP : finding law paramaters for ballistic impact in 3D ((Hydro) Johnson Cook), ball and plate
Hello altair community,
For a class project, we are trying to simulate a ball piercing through an aluminium plate at high speed.
We did a first try with plate in Shell element using the Johnson Cook law, and the results were accurate enough.
Now we try it in 3D, but the simulation is unrealistic :
Message we get :
EXCEEDED EPS_MAX ON SOLID ELEMENT NUMBER 34877: DEVIATORIC STRESS SET TO 0 ON INTEGRATION POINT
I know that the eps_max is exceeded (set to 0.1), this is what we want, but how do I tell the software to make the rupture happen ?
I also read the wiki and I found this concerning element deletion in Jc law :
When εpεp reaches the value of εmaxpεpmax in one integration point, then based on the element type:
- Shell elements: The corresponding shell element is deleted.
- Solid elements: The deviatoric stress of the corresponding integral point is permanently set to 0; however, the solid element is not deleted
Some other info : Interface type 7, min gap 0.1, 200m/s, mass = 40g, E(ball) = 2 000 000 MPa
From here, we concluded that maybe the regular JC law cant work in our 3D case ??
Then, we tried Hydro Johnson Cook, but again, the results are not what we expected :
The closest we got is this :
Here are all the law parameters :
Thank you for your help,
I attached the files of the Hydro JC
Answers
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Hi @L_utbm,
The behavior you are describing is expected with the set of parameters you are using.
You need to define a failure model and some erosion parameters. This will allow you to calibrate the damage initialization&evolution and the quality criteria to trigger element erosion.
Here is a presentation that should be helpful for you:
I hope this helps.
Regards,
Mathis
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