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# Abaqus warning-Geometric non linearity for solutions of crack problems

## Abaqus warning-Geometric non linearity for solutions of crack problems

(OP)
Hi

Is there any points to consider while conducting geometric non-linearity in cracked plates when the aim is SIF calculations.
Abaqus issued the following warning which raised my concerns

K factors output has been requested in a large deformation (*step, nlgeom) analysis. The results might not be accurate.

there was quite a stability in the convergence of the step increments provided that kind of large steps (0.1/ 10 steps) have been adopted

Thanks

### RE: Abaqus warning-Geometric non linearity for solutions of crack problems

It's just a warning. K factors are only valid for linear problems, so the warning is to be careful when you might have large deformation (possible with NLGEOM).

### RE: Abaqus warning-Geometric non linearity for solutions of crack problems

(OP)
so what's common to use in case of NLGEOM instead of K1?
Is J-Int still valid in this case?
If I want to compare 2-cases with/and without NLGEOM which fracture parameter could be adopted from FE results?

Thanks

### RE: Abaqus warning-Geometric non linearity for solutions of crack problems

Yes, the J-integral can be used in nonlinear cases. For linear cases it is equivalent to the K factos. You find more details on that in books or papers on fracture mechanics.

### RE: Abaqus warning-Geometric non linearity for solutions of crack problems

(OP)
Mustaine3
Provided that we calculated the J-integral from the nonlinear geometric analysis. can we derive the SIFs from the J-integral in Abaqus, please?
It seems that the deviation for linear cases available, in such cases NLGEOM is it same derivation of SIF from J integral?
Thanks

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