fastener with bolt

[expcic]

Good evening,

I need a little help.
I am conducting a static-structural fem analysis on a structure that is fixed by screw+washer+shaft+nut.
I want to know what type of displacement bond should be imposed on the nodes of the structure area in contact with the two washers (which are pressed against the structure due to the tightening of the bolt).

I have imposed a complete ink condition for the area concerned. the analysis does not give strange results only that in proximity to the washer there is a peak of tension that I would like not to attribute to wrong conditions of bond.
to note that at the moment it is not interesting to know the stresses to which the screw is subjected.

I would ask you to give me any help because on the basis of this I must make very important technical choices

Thank you very much

 

[cacciatorino]

I am conducting a static-structural fem analysis on a structure that is fixed by screw+washer+shaft+nut.
I want to know what type of displacement bond should be imposed on the nodes of the structure area in contact with the two washers (which are pressed against the structure due to the tightening of the bolt).

You have to consider the precarious screw otherwise, considering the unpretended bolt, you will get an unrealistic simulation. It usually works by modeling the stem as a beam element and then applying a negative delta-t in order to put it in tension. the beam element then binds to the surfaces of the head of the screw and the nut, without putting the washers in the middle. I believe that the disaster you have considered goes well, in the hypothesis of small deformations (if you see born very strong bending moments on the beam element then there is something that does not go in the model, the screws normally should work mainly on traction).

 

[expcic]

Thank you so much!! !
after your answer I managed to solve the problem: I also referred to a file that I attach just back home, on which are illustrated the various modes of simulation of bolted joints including the one you mentioned.:finger::finger: