Crack propagation problem

[mkermani]

Hi
I am trying to model crack propagation using critical stress criterion. But Abaqus shows this error:
"**ERROR: Nodes adjacent to 1 current crack-tip nodes have debonded. The current crack-tip nodes cannot be debonded since the distances measured may be beyond the next crack tip nodes or the rest of the bonded surfaces have debonded. Critical stress criterion may not be applicable anymore. The nodes have been identified in node set ErrNodeCrackTipNodeDStep2Inc494."
I changed a lot of variables including the nodes position to increase the distance between nodes, but it doesn't work.
I will be very grateful if sombody help me.

 

[Cockroach]

That's because the crack is a discontinuty across the surface. I think that SolidWorks does a better job in it. Try modelling the crack as a seam which is subject to lateral and transverse loading.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[xerf]

The stress criterion is evaluated ahead the crack-tip
....as long as there's some ligament left.

Are you sure the the surfaces (initially in contact) are long enough (i.e., they still contain bonded nodes) such that the position at which the critical stress criterion is evaluated to be before the last pair of bonded nodes ?

 

[xerf]

Also , it might be better to post this on the ABAQUS forum:

http://www.eng-tips.com/threadminder.cfm?pid=799

 

[mkermani]

Thank you all for your answers
I think I could find the answer elsewhere. I decrease the total time of analysis. it can reduce the propagation of stress between nodes and the nodes debond before stress in next bond reaches the critical stress. BTW (for answering the question of Xref) I have enough nodes bonded before the end of process.
But now other problem happens.
The stress in each node reaches the critical stress and then the contour of stress goes to the next bond and stress increase again but the previous bond is steel bonded ( it isn’t separated).
Can you tell me why the nodes remain bonded when the fracture criterion is satisfied?
Thank you