PreTension Load direction of a Bolt in ANSYS APDL

[struclearner]

Dear Professionals,
I appreciate the response & comments. In the ANSYS APDL, the Clamp Force/Pre Load applied at the Pre Tension section of a Bolt represented by solids elements is shown by a Force labeled FX, not in the direction of Pre Load, i.e. along the Bolt axis, in the list, the magnitude of the force is clamp force applied. Why this force vector is not in the specified direction?
There are very high stresses at the pre tension section separation plane, is this usual in ANSYS? and can be ignored as Boundary Condition stresses.
Thank you very much for the help.

 

[rickfischer51]

Pretension is an idealization and I dont think it is intended to be used when the goal of the analysis is the bolt. If I wanted to analyze the bolt, I would model the bolt and nut slightly shorter than the thickness of the flanges, place one end (under side of the bolt head, for example) even with its bearing surface, and connect them with bonded contact. The nut will now be penetrating into its bearing surface. Place sliding contact between the underside of the nut and the bearing surface on the flange. Set KEYOPT 9 to 2 so that the effect of penetration is ramped. this should apply tension to the bolt, and you can evaluate stresses.

Rick Fischer
Principal Engineer
Argonne National Laboratory