Learning Forum

[mustafa.shqair]

Hello,

If i am using the CZM model in the case of debonding, where i have the values of the maximal normal energy and the maximal normal stress and i know that in my case the tangential stress is dominant ( there are both normal and tangential). I used the 60% rule to have the vaue of the maximal tangential stress from the maximal normal stress. Then also since i do know the value of the maximal tangential energy i have just multiplied the value of the maximal normal energy by 60%.

I am having difficulties in convergence. My question is can i use the CZM mixed mode eventhough i know that the tangential stresses are dominant (but there are normal ones that i can not ignore)? If i used the CZM mode II i will ignore the normal stresses and this is not the case. Another question, can i put both modes of fracture but with determening which is the dominant one? Is the 60% of normal stress is always the tangential stress? Can the problem be the value of the tangential energy that i have assumed to be 60% of the normal energy?

Thanks in advance.

[Bhargava Sista]

Based on your description, mixed mode CZM is the right approach. I'm not sure about the 60% rule, it depends on the adhesive material and the bond.nRegarding the convergence issues, it is possible to run into some instabilities while using CZM due to sudden loss of stiffness. In the CZM definition you can artificial damping factor which helps to some extent. beyond that one can also use nonlinear stabilization (or use transient analysis if the snap-back is prominent) to address the convergence issues.n

[mustafa.shqair]

Thank you so much for your comment. My question was for example if i am using the mixed mode fracture, since both normal and tangential stresses exist with a slight dominance of the tangential direction, can we put when defining the CZM parameters in the mixed mode which direction is dominant. Concerning the damping coefficient, I have noticed that when i am changing it from 1e-2 s to 1e-3 s to 1e-4 s, there are alot of changes in the debonding map, then how can i choose the best coefficient?n