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[Solution]

When you receive this Warning Message, an already cracked element is attempted to be cut a second time. Cutting an element twice is not supported in the XFEM. Accordingly, the respective crack is not grown. Instead, the solver procedes with the load application until the predicted crack growth direction changes such that a different (yet uncracked) element would be cut, or until the load is fully applied. (In doing so, the substep size is often decreased to the minimum possible, leading to very slow simulation progress and large rst files.) This situation can e.g. occur, when the crack gets deviated from its physically preferred crack growth direction (e.g. due to numerical inaccuracies). In the following crack growth step, the solver would most probably try to correct the former deviation. If the foregoing deviation was big enough, this correction might lead to the intention to cut the crack tip element for a second time (which is not allowed, as stated above). A possible cause for such numerical inaccuracies could be a too small stress evaluation radius (CINT,RADIUS) when using the maximum circumferential stress criterion (STTMAX) for crack growth direction determination. Please check the attached picture for illustration.

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