Adhesive lap joint - Distortion in cohesive region

[san02]

Hi Everyone,I had been doing double lap adhesive joint analysis. Using Cohesive element COH2D4 in adhesive region 0.02 inches. Aluminium and Steel adherends (0.1 inches)with CPS8 elements full integration. Quad mesh in both types. Continuum approach is used in cohesive region. The analysis is working for 0.01 mesh size upto 0.006 mesh size in cohesive region, but when I decrease the mesh size for convergence study some elements in the cohesive region gets distorted, How to prevent the distortion ??
I have also attached the images of distorted elements in mesh.
Thanks
Santhana

 

[san02]

Sorry to not mentioned about contacts. Contact pair - Tie Constraints were used. Poisson's ratio for adhesive is 0.35

Thanks
San