Thanks Akhsay,

The gap here is visible only because of mid-surface and solid body. I tried to use the frtictional contact "Adjsut to Touch".

For linear analysis, the solution is converged but bolt pretension load(which is 15500N) is not able to tighten the clamp. If i check working load in bolt tool then it is showing the 15500N. Also the stresses are coming at the bolt shank location only. 

please check the image 


As you can seee here, if i take the non linear material properties then the results are very different which is at a very minimal load. The solution was not converged with non-linear material which i need to check as you commented.

do i need to make changes in contact also.