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PrecisionManufacturingCorp
Posts: 9
Registered: ‎11-03-2011
Message 1 of 4 (530 Views)
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Why the simple bolts and nuts don't have any stress?

530 Views, 3 Replies
07-27-2012 12:47 PM

I created a sample of cylinder with simple bolts and nuts.

I place a gravity on top of the cylinder and a load of 37000 lbs and 313 lbs of side load.

I tried to find the stress on the bolts.

Why the simple bolts and nuts don't have any stress?

Is because the I set the constrains wrong when I try to assemble?

I attached the parts and assembly.

Please take a look at your convenient.

Thanks

 

I tried to find a simulation class (in person) but not around my area (Calgary) at this time.

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JDMather
Posts: 26,342
Registered: ‎04-20-2006
Message 2 of 4 (522 Views)

Re: Why the simple bolts and nuts don't have any stress?

07-27-2012 01:45 PM in reply to: PrecisionManufacturingCorp

r2013

I didn't look at this in-depth, but I might change the Contacts on some of the cylindrical faces of the fasteners (you had all default Bonded) (where going through clearance holes).

 

Fastener FEA.PNG

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henderh
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Registered: ‎06-07-2007
Message 3 of 4 (465 Views)

Re: Why the simple bolts and nuts don't have any stress?

07-30-2012 12:38 PM in reply to: PrecisionManufacturingCorp

I think JD is right on (as usual).

 

  Although you may have constrained the assembly so that if the bolts weren't there, the loading would cause the structure to 'fall over' under load.

 

  However, Stress Analysis isn't enhanced to the point where we can leverage the design intent of the assembly constraints and convert those over to the proper stress analysis contacts automatically...all automatic contacts are created as the bonded type, and it is up to the user to ensure the proper contact types are used.

 

  In your example, I assume that the design doesn't glue, or otherwise bond the base to the stand in 'real-life' to transfer the entire load directly.  I assume the bolts will carry much (if not all) of the 'side load'.

 

  This can be easily corrected by editing the Bonded:1 automatic contact and convert it to a Separation type contact (RMB on the contact in the browser => Edit contact).  i would also take JD's suggestion of changing other contacts that are created between the cylindrical faces of the bolts <=> holes to something other than bonded.

 

  This should get you closer to the results you're expecting...if our assumptions are correct :smileyhappy:

 

Hope this helps!  Please let us know if you have any additional questions, comments or suggestions.

 

Best regards, -Hugh

 

[Edit: forgot to attach the screen capture.  Also, if the bolts are under pre-load, you should also try to account for that as well.  There are numerous discussions on the various methods in this forum.]



Hugh Henderson
Simulation QA Engineer
DLS
Active Member
PrecisionManufacturingCorp
Posts: 9
Registered: ‎11-03-2011
Message 4 of 4 (377 Views)

Re: Why the simple bolts and nuts don't have any stress?

08-07-2012 02:32 PM in reply to: JDMather

Hello JD,

thanks for answer my question and it helped.

I tried to change the contacts but i couldn't get what you showed me.

Is possible for you to teach / show me what you did at your convenience?

like where you add the loads, constraints, and contacts.

That will be so much appreciated.

 

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