Learning Forum

[Abhilash_G]

Hello, I am simulating a bolted joint having 2 flanges and a gasket in between. The flanges are have 4 bolts at the diagonal and I am using 'Bolt pretension' feature to simulate it. I am using 3 load step adjustment , load (30kN) and lock and I am seeing a sharp increase in the preload (goes around 60kN) in the solution after probing.

I have checked all the associated parameters like contacts, gasket LD curves, etyc and they seem to be well. So could you suggest any possible solution/ reason for such high preload gain ?

Thanks,

Abhilash

[Akshay Maniyar]

Can you share the images of your model setup, bolt pretension and the plot for preload, so that forum members can help you in much better way.
Thanks,
Amaniyar

[John Doyle]

Try to eliminate or minimize all the collective penetrations in the contact pairs within the bolt pretension load path. For example, if you have bonded contacts between bolt head/nut and plates, switch to MPC formulation. If you have frictional contacts between plates, increase the stiffness factor to '10' and turn off stiffness updating. Confirm that the resulting penetrations are considerably smaller than the adjustment in bolt pretension needed to achieve convergence.