Simulation Mechanical Forums (Read-Only)
Welcome to Autodesk’s Simulation Mechanical Forums. Share your knowledge, ask questions, and explore popular Simulation Mechanical topics.
cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

boundary condition for a flange with grounded bolt connections

1 REPLY 1
Reply
Message 1 of 2
madg1
704 Views, 1 Reply

boundary condition for a flange with grounded bolt connections

Hi

I have a general question regarding boundary condtions which  helps novice users like me.

The attached image is a bolted flange and it is bolted to the ground.A moment load is applied as shown.model will be in 3d and meshed with brick elements.

 

Now In ASIM, I can use bolt generator and use grounded bolts, which essentially the one end node of the bolt is fixed.

Obviously, one side of the bolts in the pattern will be in tension and other will be in compression

Now in realty the ground resists displacement of nodes on the bottom surface of the flange which in turn effects the loads in the bolts.

 so my question is what REASONABLE boundary condtion can be assumed IN ASIM for the bottom surface of flange OTHER THAN USING GAP ELEMENTS.Smiley Happy Can we use spring elements? if so how the stiffness must be calculated.

 

thanks

flange with grounded bolt connection

madg1
ASIMM 2012
1 REPLY 1
Message 2 of 2
John_Holtz
in reply to: madg1

Hi madg1,

 

I think the answer depends on what assumption you want to make.

 

1) If the flange will remain in contact with the ground over the entire surface, then use general constraints.

2) If the flange will lift up, then you need to use contact.

 

If you know the stiffness of "the ground", then you will need to distribute that stiffness to the N constraints or gap elements using the law of equivalent stiffness for parallel springs. (1 known stiffness somehow equals N springs working in parallel.)

 

Naturally, option 1 is the fastest solution, and the reaction forces would indicate whether any of the nodes are trying to lift off of the ground (but are being restrained).

 

Be sure to apply the preload to the bolts; otherwise, the flange will be lifting off of the ground.

 



John Holtz, P.E.

Global Product Support
Autodesk, Inc.


If not provided already, be sure to indicate the version of Inventor Nastran you are using!

"The knowledge you seek is at knowledge.autodesk.com" - Confucius 😉

Can't find what you're looking for? Ask the community or share your knowledge.

Post to forums  

Autodesk Design & Make Report