I am working static study of a rectangular box which sees 3000psi on all outer surfaces. The lid which has 6 screws (3 on each side) to hold both box and lid together. I used bolt connector for those screws for this study. When I saw the "deformed result" of the study, I realized that box is getting deformed at center portion as if there is no screw there holding both parts.
Then I did another study, with same above settings except, I gave "on cylindrical faces" fixture for all mating screw surfaces (both threaded hole on the box and clearance hole on lid) by restraining radial direction translation as zero. Then deformed result shows as if all fastened surfaces are tied together.
I was just wondering, why deformation was different when I just bolt connector? Please take a look at the attached doc, which compares both studies.
I would greatly appreciate, if someone could help me understanding it.
Windows 7 X 64 bit