Element Removal in CalculiX for Fracture

I’m currently looking into converting some Abaqus fracture simulations (Charpy Impact & Compact Tension tests) into Calculix. I’m currently using an Abaqus VUMAT that has a flag which deletes elements in the mesh once the material damage reaches a certain amount (specifying the state variable # corresponding to deletion as *Depvar, Delete=#), but I am struggling to determine if Calculix has a similar capability. Any suggestions would be greatly appreciated.

I’m not sure if this can work but maybe the *MODEL CHANGE card? Page 526 of ccx 2.17 manual.

With this option, one can activate or deactivate elements and contact pairs. Furthermore, one can turn the mechanical strain in existing elements into residual strain at the start of a new step.

Not sure if can be combined with the *DEPVARs.

That is interesting but from further reading I think *MODEL CHANGE wouldn’t be able to dynamically remove elements. After reading some of the Abaqus documentation on element deletion however, I think I may be able to work around that though by just setting all of the stresses to zero in the element once the damage criterion is met, so I’ll just have to modify the user material a bit. Thanks for the quick response and help.

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You are welcome :slight_smile:. Sounds like a good workaround.

Just be aware that if you reduce the stiffness to 0, you could get an ill conditioned stiffness matrix (one could use for instance 1e-6). Furthermore, the elements are still populated in such a matrix and might cause some troubles if not removed from the analysis. Anyways, just try.

That’s a good point, thanks. Currently I am using Explicit Dynamics though, so it shouldn’t be too big of a deal.