Learning Forum

[Peter Yip]

Hi all,

On my quest to understand all the parameters involved in preparing a successful high-speed impact simulation, I found a thread called, "On Erosion" (see here: /forum/forums/topic/on-erosion/) that spurred a few questions about how MAT_ADD_EROSION works. If an element is removed from the calculation, say after some EFFEPS condition is met, then does the energy from that eroded element get averaged to the other neighboring elements? How does an eroded node still carry momentum (stated in link) since it is effectively removed from the simulation?

If I have an impact configuration with a brittle ceramic projectile hitting a rigid wall (fictitious situation just to have some complete fracture/shatter or material), I'm assuming then finite element is just not appropriate for this case even with erosion criteria?

Any clarification/understanding is greatly appreciated.

Peter 

[Jim Day]

glstat and matsum will include "eroded" energies that track the contributions of element eroded by failure criteria. In the course of deleting/eroding elements, some nodes are typically liberated from the remaining mesh. You can see those nodes when postprocessing with LS-PrePost by selecting View>Show Deleted Nodes.

[Peter Yip]

Jim,

Thank you for the information. I will be sure to include those in my ASCII output and track the energies in my next run. Is there a "rule-of-thumb" threshold that makes sense in terms of what energies I should view as acceptable? Ideally, energy should be conserved, but I recognize that can be difficult in high speed impact problems where large deformations and element deletions may be necessary. However, I'd imagine it can't be violated that bad? I may be looking at the problem incorrectly, so if that is the case, I'm happy to discuss further.

Thanks,

Peter

[Jim Day]

Notes concerning energy balance are available in this text file ... https://ftp.lstc.com/anonymous/outgoing/support/FAQ/energy_balance . (This link is public; I confirmed it can be found via Google.) Total energies in glstat include the eroded energies, so the energy balance checking takes erosion into account.