PRETS179

[lukasz2]

Hi,

How properly constrain model including PRETS179 element to be converged? I`m trying to avoid this message...

Preconditioned conjugate gradient solver error level 1. Possibly, the model is unconstrained or additional iterations may be needed. Try running with a multiplier MULT > 1 in EQSLV command (3 > MULT > 1).

but the only way is to constrain it (all DOF = 0) in both sides where pretension is acting...

Thanks,
Lukasz

 

[Drej]

Your model is trying to fly apart because of poor initial conditions. Try attaching weak springs to your structure (and constrain them) and then solve.


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[Drej]

Also, don't forget that you need to consider the pre-tension node.

From ANSYS help:

"The pretension node K has only one translation degree of freedom UX, which defines the relative displacement between the two sections A and B in the pretension load direction. Sliding motion is prevented automatically. If the pretension node and the bolted structure are not well constrained, rigid body motion can occur. Therefore, in the beginning of each load step, you should verify the boundary conditions for bolt structures carefully."


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[cbrn]

Hi,
in addition, consider that the pretension elements are not the whole problem: if you want to model a preloaded bolt with the PRETS179, you also have to setup the proper Contact Pairs for the areas of the bolt/flanges interfaces. I suspect you are missing some...

Regards