Reply To: Negative eroding contact energy in impact testing

[Reno Genest]

Hello Jordan,

You mean negative eroded internal energy and not eroding contact energy correct?

Do you have shell elements in your model? Negative internal energy indicates a problem with the model. See the following link:

Internal Energy — Welcome to the LS-DYNA support site

From our knowledge database: "If you subtract "eroded internal energy" from "internal energy", you have the internal energy of elements which remain in the simulation."

So, the eroded internal energy is the internal energy of elements that have failed and got deleted (eroded) from the simulation. This means that the internal energy just before these elements were deleted was negative which is not correct. 

If you remove the failure criteria in your model, do you get negative internal energy for certain parts? Check internal energy by part using the matsum database.

You can try to add *DAMPING_PART_STIFFNESS to the model and see if you get rid of the negative internal energy.

Which version of LS-DYNA are you using? Have you tried with the latest version?

Also, have you tried SMP vs MPP?

You can review the crash guidelines and see if you can solve the problem:

https://ftp.lstc.com/anonymous/outgoing/support/PRESENTATIONS/Crash_Guidelines.pdf

 

Let me know how it goes.

 

Reno.