I am running a tensile test on a sample with a notch in the middle. I have created a UDMGINI code resembling MaxPS damage that works perfectly like the Built-in MaxPS damage of Abaqus. Now, I want to use my UDMGINI code of MaxPS alongside defining simple Elastic behavior in a UMAT code.

I know that to use both UDMGINI and UMAT in a single FORTRAN code, I need to add *surface behavior to both *Assembly and *Materials in the keywords. However, the results are not the same as when I just run my MaxPS code (without UMAT). To be more specific, instead of detachment, two sides of the crack plane start sliding on each other.

How should I change the *Surface behavior keyword? Is there another way to use UDMGINI and UMAT with each other?