## Autodesk Simulation Mechanical and Multiphysics

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Posts: 11
Registered: ‎03-03-2011

# Average stress over surface

196 Views, 5 Replies
03-19-2012 06:19 AM

I am trying to find a function that can give me the average stress over a selected surface, i just can't seem to find it, can somebody guide me on how to do this?

Konrad Lindblad
Mechanical Engineering
Royal Institute of Technology
Sweden
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Employee
Posts: 398
Registered: ‎05-06-2010

# Re: Average stress over surface

03-19-2012 06:24 AM in reply to: konradl

I don't think ASIM provides direct tools for this.

Usually, I export these data to some packages, such as MS Excel, and then calculate average.

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# Re: Average stress over surface

03-19-2012 06:45 AM in reply to: S.LI

Ok, thanks!

I found this function, but i don't know if its the average.

Mean: 0,35 N/(mm^2)

I need this just to verify that ASIM calculates bolted joints correctly in my master thesis paper.

What i've done is modeled two simple blocks with holes for two bolts. The blocks meet on a 1x1 cm contact surface, the average surface pressure should be 1 N per mm^2 if i put a preload of 50 N on each bolt.

So with a mean of 0,35 N/(mm^2) i am way off.

Konrad Lindblad
Mechanical Engineering
Royal Institute of Technology
Sweden
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Employee
Posts: 398
Registered: ‎05-06-2010

# Re: Average stress over surface

03-19-2012 07:03 AM in reply to: konradl

For your case, maybe an averaged reaction force may be better than stress. Stress is a tensor, which is sensitive with configurations, such as area, direction etc.

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# Re: Average stress over surface

03-19-2012 07:09 AM in reply to: konradl

Hi Konrad,

The function you found under the "Inquire Results" does give the average.

But that is a poor way of checking the load in the bolts. Your method assumes that the areas over which each of the 16 stresses are equal. In otherwords, the average is not the average of 16 nodes. The average is the integral of the stress times the area, and then that total divided by the total area to get the average. The softare will not do that directly.

Why not look at the force in the bolts to see if you have the desired preload? (Maybe that is too easy ). "Results Contours > Other Results > Element Forces > Axial Force".

Then when you discover that the force is the bolt is smaller than desired, please read the following page in the documentation: "Help > Autodesk Simulation > Setting Up and Performing the Analysis > Set Up Analyses > Linear > Loads and Constraints > Beam Preload"

The other way to get the calculation would be to get the reaction force between the two parts. This requires more work because our reaction forces are only between the model and the surroundings. By default, the reaction forces are 0 between parts. But there is an option that can be set so that reaction forces between parts is calculated and output. That setting is under the "Setup > Model Setup > Parameters" and then on the Solutions tab.

Sincerely,
John Holtz, P.E.
Senior User Experience Designer, Simulation
Autodesk, Inc.

Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)
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Posts: 11
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# Re: Average stress over surface

03-19-2012 07:30 AM in reply to: INACTIVE_AstroJohn

Thanks for the wiki link, explains pretty much everything i wondered about! I'll just use the Axial Force result and verify my model with that. Thanks alot!

Konrad Lindblad
Mechanical Engineering
Royal Institute of Technology
Sweden
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