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verneinvirgile6-Contributor
6-Contributor
May 1, 2020
Question

Dear experts in fasteners simulation : Bolt with friction

  • May 1, 2020
  • 2 replies
  • 4582 views

Dear Forum , I'm a french teacher an I used to use CREO 5.0.3.0. I built a course about fastener design and calculs and I would like to show to students the link between calculus ans simulation , for introduce parameters to the students , I've chosen to use a simple model , 2 parts joined with a blot 

verneinvirgile_0-1588340355126.png

When I perform a simulation with a axial force I find the same results as the calculation (I've join the PDF in french ) 

 

Now I want to perform a simulation with a tangential force ,   

verneinvirgile_0-1588340355126.png

And now It's more complexe, 

I Anchor the pink part , I apply a tangentiel force (500 N) on the yellow part . 

This is  bolt définition with a preload of 8000 N 

 
 
 

bolt defintion.PNG

I define a interface with a infinite friction and a friction indicator at 0.5 

 

interface .PNG

 

the analyse settings 

analyse settings .PNG

 

and here are all the results 

resultats .PNG

 

Result analyse : to do simple , the preload is 8000 and the indicator is 0,5 , in theory the max tang force will be 4000 N before slipping. 

the fastener shear force is low but about 10N , weird ... and the slippage is present ,  it could not be 

 

If I read that from CREO : 

Create Slippage Indicators—Creates three slippage indicator measures. It is available for selection only if you select the Infinite option for friction. All the slippage measures are created automatically. For a frictionless interface, no slippage measures are created.
These measures check if slippage occurred in the contact region during a static analysis with contacts. If any of the slippage indicator measure values is positive during a static analysis with contacts, a warning appears in the summary report (.rpt file). This warning indicates that the surfaces in contact may have slipped relative to each other. In this case the assumption of infinite friction is inaccurate.

I can see that interface1_any_slippage is positive 

 

If I read that from CREO : 

Si=T—N*
 
 <= 0
where 
 
 is a coefficient of friction.
Slippage does not occur at xi when the value of Si is less than or equal to zero. Creo Simulate calculates Si at every point of the surface and uses Si to calculate the following slippage indicator measures:
• Any Slippage—Maximum of Si
A positive value of this measure indicates that slippage has occurred at at least one location in a contact region.
• Complete Slippage—Minimum of Si
A positive value indicates that slippage has occurred at all locations in a contact region.
• Average Slippage—Integral of Si over the contact surface.
A positive value indicates that slippage has occurred at most of the locations in a contact region.
This measure is created when both the surfaces in contact are planar.
I've tryed with a 5000N tangential force 
here are the results 
resultat1.PNG

In this case the yellow part must slip and I can notice than the Interface1_complete slippage is not positif ...weird again ...

the shear force must be about 5000 - 4000 = 1000 N , is it not ...weird ? 

Could you give me some hints to resolve my problem  or I make big mistakes ? 

thanks a lot for reading this post

BR

VV  

    2 replies

    B
    bafoster841-Visitor
    1-Visitor
    May 13, 2020

    Is it possible for you to share your model?

    R
    rrabe12-Amethyst
    12-Amethyst
    July 2, 2020

    You can select the contact surface (pink-yellow) and also create a force measurement in the direction of the applied force. This should be be easier to interpret. 

     

    You may spot local sliding in the interface but this not means that it will slide. Check the contact colors regarding sliding in the result.

     

    What I cannot identify in your simulation is if you are making use of the "real" preload - considering the flange stiffness. Simulate 5.0 has this option. It modifies the preload until get the "real"  8000N. But I think it is selected.

    D
    DenisJaunin15-Moonstone
    15-Moonstone
    July 6, 2020

    Bonjour verneinvirgile,

    C'est très intéressant.

    Cordialement.

    Denis

    V
    verneinvirgile6-ContributorAuthor
    6-Contributor
    March 14, 2021

    Bonjour , merci pour votre commentaire.

    cdlt

    VV

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