Learning Forum

[bobsik641]

Hello everyone! 

I'm doing two simulations in the Explicit Dynamics module. Regarding the solver output, both Momentum Summary and Energy Conservation (energy error=0) are fine. However, there is some Hourglass energy,  which exceeds the conventional 5% of the Internal Energy. How can it be solved in these cases?

Projectile impact: erosion on material failure, materials: two different explicit structural steels, but the same erosion criteria (Max Principal  Strain=0.3,Max Shear Strain=0.5). Only a 90deg slice is analysed, proper symmetry conditions imposed. 

Cylinder impact: erosion on material failure, materials: cylinder- explicit steel (Max Eq Plastic Strain=0.2), disk- explicit AL (Max Eq Plastic Strain=0.4). Only a 90deg slice is analysed, proper symmetry conditions imposed. 

 EDIT: I reduced the target plate size and then refined the mesh on both features, but it didn't resolve the issue

 

[bobsik641]

 I cannot attach nor JPG, nor PNG screenshots, so you can access everything here

 

https://docs.google.com/document/d/1Ry3i25JkLQWjQfqkkaBd5buiKVSLpGJjBdsuOSZeagI/edit?usp=sharing

[bobsik641]

bump

[Wenlong]

You may have already tried this, but just checking: have you tried changing the hourglass damping control to "Flanagan Belytschko"?

Regards,

Wenlong

 

[bobsik641]

Thank you, I really appreciate your help. Flanagan-Belytschenko did some fantastic work. The hourglass energy was vastly reduced. I used a stiffness coefficient of 0.03 (as suggested by  a LS-DYNA manual) so as not to add excessive stiffness to the model.

 

That hourglass damping control had once spoiled my solution, so I didn't even think about using it.