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Inventor 2011 - FEA Bolt Head Simulation

4 REPLIES 4
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Message 1 of 5
yetirawr
4359 Views, 4 Replies

Inventor 2011 - FEA Bolt Head Simulation

I've been working with Inventor 2011 - Pro and have not had any success with utilizing a bolted connection (blind hole) in an FEA stress analysis. I have reviewed some of the forums regarding this and one suggestion involved a using a bolt placed "as custom" instead of "as standard". It appears however that there is a default setting that I currently have which doesn't allow this as a selection (see attached image).

 

Any help on this would be greatly appreciated or any suggestions regarding bolted blind hole connections.

 

Thanks,

Dan   

4 REPLIES 4
Message 2 of 5
henderh
in reply to: yetirawr

Hi Dan,

 

  I'm not sure why the "as-custom" option isn't available on your install.

 

  One way I was able to edit the "As standard" fastener is to move it out of the Content Center folder.  Copy / paste it to a different location (e.g. next to the assembly file) using windows explorer, then place it in the assembly.

 

Hope this helped...



Hugh Henderson
QA Engineer (Fusion Simulation)
Message 3 of 5
Senordan12
in reply to: yetirawr

Hugh,

 

Thanks for the reply. It would seem that the "Bolted Connection" created in my assembly that I'm working with would simply allow the FEA model to automatically detect the correct (ideal) type of contacts needed for a blind-hole connection.

 

I've tried repeatly with different types of contacts and/or fixed constraints to see if there is any resulting stresses.  

 

Are there any better ways to simulate the reaction force (bolt head stresses) created by an overturning moment on a flanged bolt pattern?  Do I need to make the bolts "dumb" solid objects with no relation to the Content Center or a Bolted Connection to make this work?

 

Thanks again,

Dan

Message 4 of 5
henderh
in reply to: Senordan12

Hi Dan,

 

  Inventor Stress Analysis doesn't have a way of detecting the ideal type of contacts for an assembly.  By default, all automatic contact types are the Bonded type.  It is up to the user to ensure the proper type of contacts are used in order to simulate "real life".  At the present time there isn't a dedicated "bolted connection" type contact or loading.  Also, we cannot directly specify a preload or pre-stressed condition in a component.

 

  This is a tricky business since most bolt preloads are specified with bolt head torque.  The resulting preload (or pre-stretch) greatly depends on the thread type, bolt diameter, thread surface roughness, lubrication, etc.  Due to all these factors a more accurate way to measure or specify preload is by directly measuring the bolt stretch.

 

  What we can do is create a workaround, the most common is to cut a chunk out of the bolt shank.  We can then add forces (to the faces created by the cut) to simulate the tensile preload.

 

  Another option would be to define a pre-stretch by using a fixed displacement (we can specify in the vector components in the fixed constraint) to the faces created by cutting out a chunk of the bolt shank. You can view the reaction forces resulting from the fixed displacement (RMB context menu on the the constraint in the browser) .

 

  If you're simulating whether or not preloaded bolts will keep flanges from separating under load, the cut-bolt preload workaround should work.  However, trying to simulate how much preload will result from a torque setting on the bolt head is probably not possible (due the the many factors involved) with our current set of tools in Inventor.  In fact it is said that 80% of the torque used to preload bolts is taken up in friction alone.

 

  Please let us know if you have any additional questions, comments or suggestions.

 

Best regards, -Hugh

 

 



Hugh Henderson
QA Engineer (Fusion Simulation)
Message 5 of 5
gagnonjp
in reply to: yetirawr

Hello Hugh, I would like to know how inventor handle parts in FEA when they are in collision? Exemple if 2 steel plate are superposed, does it make like a single plate? What if the materials are differents? 

 

thanks

JP

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