Learning Forum

[fatemesafarieng]

Hi, 

I am currently running vehicle collision simulations with guardrails using LS-DYNA. However, I noticed that the hourglass energy in my model becomes negative midway through the simulation, as shown in the attached figure. I have tried adjusting the hourglass control coefficients and switched from Type 4 to Type 5, but the issue still persists.

Could you please advise on how to resolve this problem? Any suggestions or recommended settings for managing hourglass energy in such cases would be greatly appreciated.

Thank you in advance for your assistance.

 

Best,

Fatemeh

 

[Alex R.]

Hello Fatemeh,

Negative energy is indicative that the elements are undergoing severe deformation. The best would be visualizing hourglass energy in the model and inspecting the elements that are observing negative values, searching for instability. To include hourglass energy in d3plot please see SHGE in *DATABASE_EXTENT_BINARY for shells and HDYRO=4 in *DATABASE_EXTENT_BINARY for solids.

Another option would be running the model with fully integrated elements please see ELFORM = 16 or -16 for shells and ELFORM = 2, -1, -2 for Solids.

Please let me know how it goes.

Thank you,

Alex

[obreitenberg66]

 

@Raft Wars is going great, thanks for sharing.