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Bolt Preload, Temp Method, Multi-Set

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Message 1 of 3
dferrierQ9L99
134 Views, 2 Replies

Bolt Preload, Temp Method, Multi-Set

I'm having trouble with a multi-step bolt preload. Case 1 works as expected. Case 2 shows the expected displacement behavior, BUT the "beam force end a-x" is unexpectedly compressive when loaded with a negative temp preload.

 

I'm modeling a clamp assembly with 2 parts and 2 bolts. First the bolt connecting the two parts together is tightened. Then the fastener that closes the clamp is tightened.

 

I'm using SOL 106 multi-step. Case 1 is a temp preload on the first bolt. Case 2 is the same, but with the second bolt temp load included.

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Message 2 of 3
John_Holtz
in reply to: dferrierQ9L99

Hi @dferrierQ9L99 . Welcome to the Inventor Nastran forum.

 

That is an interesting model and the first time I have seen the TEMPRB command.

 

The displacement results imply that the second bolt is getting shorter, correct? (It is late for me, so I may not be thinking clearly. :sleeping_face:) Is it possible that the direction of the bolts are reversed so a + force in one bolt indicates tension while a - force in the other bolt indicates tension? (That's a bit of a stretch, no pun intended, but that's all I have at this hour.)

 

Another test would be to reverse which bolt is tightened first to confirm that it behaves more as expected.

 

John



John Holtz, P.E.

Global Product Support
Autodesk, Inc.


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Message 3 of 3
John_Holtz
in reply to: John_Holtz

Try this @dferrierQ9L99 

 

  1. Keep your loads as currently defined.
  2. Add a new subcase (subcase 3). Keep the beam temperatures held at their constant temperatures (meaning the same amount of preload).
  3. Since the new load is the same in subcase 3 as in subcase 2, the results should not change. You only need to run 1 step in subcase 3.
  4. Run the analysis. Do the beam results "magically" change in subcase 3? 

John



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 :winking_face:

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