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criterion to stop crack analysis in xfem

Dear all,

my problem is dealing with a fatigue crack propagation analysis using XFEM (linear elastic case) with a prescribed initial imperfection in the modeled solid. What is the criterion to exit from such a kind of analysis?

Thank you in acvance!

The stress intensity factors or J integral will probably surpass a given
limit  (fracture tenacity)  meaning that the studied solid would
then be completely ruptured (inversely - I guess - they could decrease
until the crack stops propagating). In terms of simulation : the stress
intensity factors or J integral can be verified at each propagation step
to see if they're outside of the domain of propagation or a finite
number of steps are defined beforehand or your simulation crashes
because all ( or one of ) the crack fronts have reached the edge of your solid
and/or your xfem domain.

 

@mforbes

Thank you for your answer! By fracture tenacity you mean the fracture toughness Kc of the material, I suppose? I think that comparing Kic (fracture toughness in Mode I) with KI (Mode I SIF) is the suitable criterion to answer in my case. If Kic < KI the analysis stops. Of course prediscribed crack segments or the conditions when the crack reaches the boundary of the solid, are common cases to stop the algorithm.

But I've noticed also something: Suppose you have the case of a single edge notched specimen (see figure). For every magnitute of force F the crack will grow, even F is small or large. Why is that? (in each step of xfem analysis, I always solve [K]{d} = [F] with corresponding enriched K with the same initial value of F).  


 

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