plasticity model with damage ductile criterion

Hello ,

 I´m working in my thesis with abaqus only since 4 months, so I´m quite new. I have to simulate the welding of two sheets with electromagnetic pulse process. Under these kind of processes the material is load under high values of velocity and deformations. Taking into account these conditions I have chosen three different flow plasticity models:

-Isotropic plasticity model without strain rate with johnson cook damage ductile criterion.

-Johnson Cook  plasticity model with johnson cook rate dependance with johnson cook damage ductile criterion.

-Johnson Cook plasticity model with johnson cook rate dependance.

The third one is not showing the wavy interface in the bond between both materials which is so typical  of these kind of processes. The second one is not  neither showing it. The first one is the only one that is giving "correct" results.

I don´t understand why I have to use a damage ductile criterion to see these wavy interface as, under the conditions that I´m working, sheets are just welded, not fractured (the damage energy is 0). I neither understand why I can´t see this wavy interface using Johnson cook and I can see it  with isotropic, if J-C is the closer model to reality. I think that maybe the problem can be in the different calculations of the equivalent plastic strain because when I used johnson cook the PEEQ is almost zero around the welded zone. 

I would be really glad if somebody could help me.

Thanks,