Cohesive crack - how to verify model? Cant figure out how to output stress intensity factor...

Hello,

I am simulating crack propagation with cohesive elements. In order to verify that my model is working correctly I wanted to compare it to some real world data or benchmark examples. One such example is in the Abaqus Benchmarks manual - a flat plate with a crack in the center.

However in that example, and in fact in all other fracture data manuals I can find, usually only the stress intensity factor is listed for any example problems. So for example in the plate with crack in the center, I know what the correct stress intensity factor is for certain dimensions of the plate and load. This means if I can model the same plate and crack in Abaqus, and extract the stress intensity factor from my Abaqus model, I would be able to compare it to this correct value and verify the model.

My crack propagation model however uses cohesive elements since I need to study the crack propagation with load. I do not know of any way to get this model to give me the stress intensity factor for the crack. It damages and deletes the cohesive elements correctly once the stress increases beyond damage initiation as the crack propagates, but I have no way of knowing what the stress intensity factor is. Cohesive zone model does not appear to output j-integral value either.

So I cannot compare my model with the benchmark example. And I therefore cannot verify the model. Do any of you know how I can request Abaqus for stress intensity factor from a cohesive zone model of crack propagation?

Alternatively do you know any other way I can compare a cohesive zone model with a benchmark example to verify it is working correctly? Possibly some other field/history output that can be compared with given stress intensity of benchmark examples?

For the record I have no background in fracture mechanics (I am an aerodynamacist), so everything I have learnt about cracks over the last few weeks is from the Abaqus manual and google. Let me know if there is some flaw in my logic here (and any solution). Thank you for any help/advice you can give me.