bolt preloaded and friction coefficient

[alexander..sokolov]

Hello everyone!

In static stress with linear material:

I try to simulate simple model:  we have one plate of concrete, and to plate of steel places above and below concete plate, and we make hole throu all parts (20мм) and inseret bolt with nut. Diametr bolt - 16мм, preload - 10000N. All contacts between parts - surface with friction coefficient - 0,45. And we apply horizontal force to each steel part - 1N, and midle part - fixed. Bolt without tight to fit! And result of displacement - too large!!!  And it's look like preloaded doesn't work in may case! Please help me to undestund what I make wrong? (material of bolt - steel). And I've noted - nothing change if I make contact surface without friction coefficient.

I will be happy to get any advice!!! Please help me)

[arizawilmer]

Hello

My guest is that the error in in the bolt . I did someting similar to what you propose and  the results are different.  When you add the bolt  select all the internal surfaces of the hole.

[alexander..sokolov]

Thanks for answer!) And you apply horizontal force 1N to above and below plate?

[arizawilmer]

Yes...as you bolt preload is bigger than the load it shows the deformation
of the steel sheets by the preload....

[alexander..sokolov]

And I try to make it again and again), and I get again so large displacement! Please look at my model, I attach it.

[alexander..sokolov]

Yes...as you bolt preload is bigger than the load it shows the deformation
of the steel sheets by the preload....
ОК, thank you!)

[arizawilmer · Accepted solution]

Hello ...you have to create a contact between the bolt part and the other elements one by one connect then with a bond connection. i used serface a it works...by some reason it is not attaching the default contact to the parts....

[alexander..sokolov]

Ooo! Thank you very much for youre activiti!!!!!! It's nice and perfect idea! I did exactly as you write and unfurtenatly get again large deformation!(( It's miracle and something magical. We both use the same version and the same model, but results different!  I woud appreciate if you upload last model!))   (P.S. I try to delete all result, delete mesh and make analize - but nothing change)  Thank you very much!)

[alexander..sokolov]

Thank you very much! Once I get normal result! And I can't undestand why sometimes it works, but very often it doesn't work. 

[bryan_mcnatt]

I think the bolt preload value that you're adding only applies to the bolt itself.  I don't think the software takes that value and uses it to press the parts between the bolt head and nut together.  That preload value is used to determine bolt stress due to the combined loading of the pre-load and whatever else you might be doing in your model which would load the bolt further.  I think to acually press the top part against the bottom part with the bolt pre-load force you're attempting, you'd have to add such a force separately.  Can someone else confirm my understanding on this?  Or, straighten me out too!

[AstroJohnPE]

Sorry blaeiouk, but you are wrong. The bolt preload generates an axial force in the bolt which is resisted by the compression of the parts. No other loads are required to see a load in the plates.

There is a slight chance that the issue in this situation is the language. Not the spoken language of the people posting messages but the "language" of the computer; that is, the regional settings. In the original post, the displacement contour indicated that the comma (",") was being used as the decimal separator. So if the user entered the friction coefficient as 0,3 or whatever value, the software may not have been able to understand that and interpretted it as 0. The user should try 0.3 to see see if it makes a difference.

[bryan_mcnatt]

Thanks John.

 I think my past misunderstanding stemmed from this statement in the Help:

I just ran a simple model to show myself that you're right ().  I don't recall the model or situation that led me to interpret or believe such.  Glad to have this cleared up and maybe others can benefit from this clarification.

[alexander..sokolov]

Hello!) Thank's AstroJohnPE for advice! I check this moment (about "," and ".") And I try apply force insted of bolt preload - just check about friction, and in this case everithing is good. (in below picture I aplly vertical forcec and horizontal forcec to top and down plate) But if I make simulation with bolt - my plate flaw away). And, yes it's look like friction =0.  i show below my model with bolt conection.  (In my model diametr of bolt less than hole diametr, and  we conection bolt with plates  with  two contacts  : nut and bolt head.