it looks like you have a reasonable setup
what problem are you running into?
have you applied the appropriate contacts?
if you have simulation professional or higher, i would recommend running this in 2d axisymmetry
Thanks for your comment
i am using 2d axissymmetry.in which contacts used in mating area?
i am not a simulation professional.
Are the threads modeled as a helix, or a revolve? it changes the root diameter if it is a revolve--I'm not sure how big the effect on the thread stress would be though. And it sounds from your post as if you are particularly worried about the threads pulling out--or that they already did and your trying to figure out why. If it's a helix, it's not really axisymmetric. Again, I'm not real sure what the effect would be.
Your fixtures and loads look reasonable. You'll need to change your global contact from bonded to no penetration. You'll need very small elements to capture anything reasonable, because in real life the strain gradients in screws are going to be very steep.
I'd like to see the results when this runs.