Hi everyone,
I am working with abaqus by using XFEM.
I am modelling a Single Lap Joint and I have simulated the crack propagation within the adhesive. Nonetheless, I also want to extract the Load-Displacement curves from my simulation model. The thing is, wen I plot them, I get extremelly high values, which are not correct as well as the curve does not show that a crack has been initiated and propagated by having a decrease in the load.
If someone has been through the same problem as I, or has the knowledge of simulating XFEM in Abaqus, please help me!
Thank you in advance :)
Hi Joanna,
It´s a brittle adhesive and I've used the traction-separation law MAXS. In terms of converging, the crack propagated till the substrates and did no go any further for the total separation of the adhesive from the substrate.
Hello Catarina,
Have you tried playing around with the MAXS value? If your peak force in the F-d diagram is too high, that could be the cause. Because if MAXS is too high for the mesh size you are using, the crack won't initiate when it should. Another possiblity is to reduce your mesh size. Since you're using a cohesive law, the model should be forming a cohesive zone, where the stiffness of the element is degraded, but not yet zero.
When using CZM, the rule of thumb is that your cohesive zone size should be 3-5 elements, but I'm not sure if that also applies to XFEM.
Do I understand correctly that the stiffness of your model is not decreasing, even after crack initiation? Are you using viscous regularisation? If so, it sounds like your viscous regularisation might be too strong, which prevents the cohesive zone from softening appropriately. One way you can check this is by looking at the amount of energy dissipated by the viscosity ('creep dissipation' in Abaqus). Since in this case the viscosity is a numerical 'trick' rather than a physical effect, the enery dissipated by the viscosity should be negligible compared to the strain energy or damage dissipation. If it's not, that's a hint your viscosity is too strong and you should lower the viscosity parameter.
https://books.google.iq/books?id=gDYNDgAAQBAJ&pg=PA320&lpg=PA320&dq=Load-Displacement+curves+with+XFEM+in+Abaqus&source=bl&ots=kjX5Dc4D7i&sig=ACfU3U10LqkCs6v-kLXqxwkpl5c6ZewoaQ&hl=ar&sa=X&ved=2ahUKEwjL3-ru_NvpAhUMUcAKHY3wDG8Q6AEwDnoECAsQAQ
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