flange joint behaviour

[michele81]

I'd need a comparison of the loads in a flangeed joint.
attached I carry the classic tensor diagram of a bolted connection, on the left only preloaded with δs deformation of the vines and δf deformation of the flanges and v precarious condition; right with a f forceb which tends to separate the flanges.
Now I have the opposite problem, so my strength fb is a button force that tends to further compress the flanges. the preload is given to avoid vibrations and consequent destruction of the joint.
under these assumptions the left tensor diagram how does it change?

my hypothesis is that it behaves similarly to the photo but symmetrical compared to point v, with the deformation δf growing and that δs decreasing.

Any thoughts about that?

 

[luigi.paiano]

Can you explain better?? I didn't understand the question well

 

[michele81]

the photo that I uploaded represents the operation of a bolted joint with preload on the bolts subject to a force that tries to remove the bolted surfaces. the preload is used to avoid the detachment of these surfaces during the working cycle.
my case is the opposite: the force that is applied does not tend to remove the surfaces but to compress them further among themselves. being this force button, the preload serves to avoid vibrations.
I was interested in evaluating the diagram in the presence of this force that tends to increase the deformation δf (compression of the surfaces to be blocked) to understand if and how the bolts are discharged to each cycle.

 

[luigi.paiano]

I think you have to calculate the load part that is discharged on the bolts and that on the flange.
you should first calculate the stiffness of both.there are approximate formulas for this.
do this you can write fb=fi+(kb/(kb+kc))fe where fi is the preload,kb the stiffness of the bolt,kc that of the flange and fe is the external force( taken with his sign).
for the flange instead fc=fi-(kc/(kc+kb))) I hope to have been of help and to have understood the question

 

[luigi.paiano]

stiffness however you can get it from the chart you posted

 

[michele81]

stiffness however you can get it from the chart you posted

Thank you.
In fact, my doubt concerns just how to insert the fb force because the rigidities I have already calculated them, and the relationships to be used for the case I posted I know them.