I have recently compared Pretension by means of load with Pretension by means of length adjustment using as reference a model that was hand calculated.
The reference in case you are interested was suggested by Calc_em user.
My main interest wasn’t the Stresses at the thread. I’m assuming that the type and number of bolts are correctly selected for the service.
My interest was the behavior at the contact area as it is critical for flanged pressure vessels leak control. Gaskets need to keep a minimum seating pressure in service condition and do not exceed a maximum in assembly condition not to break it.
What I can say according to my results is that preload by means of load can’t properly capture the separation point nor the external load split into Bolt and Contact Area.
It keeps VM constant in the bolt during the external load increase. (External load increase between 1s and 2s in search of the contact separation point )
Length adjustment can capture the small bolt load increase (FSA with it’s corresponding Stress increase).
Preload with length adjustment has deliver an unexpected deviation at the separation point below 0.02%.(FEA result 2059.6KN against analytical solution 2060KN)
Length adjustment has the drawback that you need a first run to adjust the length. Preload by force can’t capture post separation behavior. Convergence fails in ccx.
