Material failure and element deletion in Abaqus/Explicit

[Konsti]

Hi,
I'm trying to implement material failure in its simplest form, as it is available in Abaqus/CAE at the elasticity table (fail stress). Even when I put small values (e.g. 0.2), the analysis shows my slab reaching a stress of 68 without failing. Where am I wrong? How can I correctly implement shear failure stress in slabs? I have tried the Hashin model for orthotropic slabs (closer to my actual material - wood), but still no failure.
I have to use the explicit solver for other reasons.
Thanks in advance,
Konstantinos

 

[FEA way]

In such cases you should always plot output variables related to the selected failure criterion (CFAILURE for this one). But keep in mind that these particular measures are just indicators of failure and don't cause any stiffness degradation. You can find the details in the "Plane stress orthotropic failure measures" chapter of the documentation.

 

[Konsti]

Thanks FEA way,
So to achieve the stiffness degradation I would have to use a damage model. However the same as the above (i.e. no failure) happens when I implement the Hashin criterion. I don't see what is so wrong...

 

[FEA way]

Apart from damage initiation criterion (Hashin in this case) you will need a damage evolution criterion that describes the rate of stiffness degradation once the initiation criterion is fulfilled.

 

[Konsti]

Yes, already doing that (with the default linear energy dissipation). It seems to work with beam elements (huge loss of stiffness as expected) but I cannot choose element removal in CAE or in the .inp file, is this normal?
When I apply it to shell elements I still can't cause this stiffness degradation. At least it's not obvious on which axis it happens: my Mises and in-plane stresses are far higher than the damage initiation stresses and still no degradation even with a damage evolution law.

 

[FEA way]

Plot the output variables related to selected damage evolution criterion (they are listed in the documentation). This should show you what actually happens with damage in this model.

 

[Konsti]

I get this...

 

[FEA way]

Make sure that you use proper damage model with proper element type.

These output variables are for damage initiation while in this case you should request and plot variables for damage evolution (STATUS and DAMAGE...).