Hello Wenlog 

Thank you for your reply, 

that didn't work well.. 

I am trying to find the effects of geometry at material( crack zone material model) on the denbonding fracture contacts. 

I have defined 3 crack zone materials (same critical fracture Energy for Normal separation/ different maximum normal contact stress)  and I have also defined three geometries ( I am using a unit cell from a hex lattice). the goal is to see with FEM how these different models compare ( through generating a load-displacement graph) - so it would be nice to see the nonlinear relationship fully go down to zero after breaking the contact ( also to compare the areas under the curve

some models converge easily others I have tried relentlessly to even get to its nonlinear behaviour ( load-displacement curve). 

also one model requires me to define the elasticity of the crack zone material, which is a little strange (??) 

if you have any feedback or suggestion, please let me know!