i am simulating a 2D crack. at the interface of 2 rectangles made of different materials. so i have 2 set of nodes at the interface,after simulating the crack do i need to merge the nodes upto the crack front ? for solving.

kcalc command in ansys is giving me much lower values of stress intensity factor. i am inputting  my pressure load 70 psi and am getting K vale 2603psi(inch)^0.5 which is not even reaching the thresshold value in the da/dn curve even for  the longest possible crack. so i feel my results are wrong.can anybody help me with this