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GarrettML
Posts: 5
Registered: ‎02-10-2014
Accepted Solution

Enforcement of Zero Residual Force - Unconstrained Nodes in Static Linear Models

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02-10-2014 03:51 PM

Hello community,

I am a relatively new user of FEMPRO v23. I have been using the "Static Stress with Linear Material Models" method. I found in one of my simulations that my constrained nodes did not account for all of my residual forces. In essence, nodes that were not constrained were providing residual forces to the environment. I could not find a solution to this.

Is it possible to keep unconstrained nodes from having residual forces?

Due to file size restrictions, if you want to use my file, please message me to request it. I have attached some of the results in .csv format, in case you don't want to run the simulation.

 

Thanks for any help,

Garrett

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Valued Mentor
AstroJohnPE
Posts: 503
Registered: ‎08-30-2012

Re: Enforcement of Zero Residual Force - Unconstrained Nodes in Static Linear Mo

02-12-2014 09:02 AM in reply to: GarrettML

 

Hi Garrett,

 

I encountered a problem last week that sounds similar to yours. In my case, I had a very "weak" part in my model so that I could apply loads to the weak part, but I did not want the weak part to restrain the deflection of the "real" model. In my case, increasing the modulus of elasticity resolved the problem.

 

If you are using "smart bonding" in your analysis, try the analysis with smart bonding turned off. (On the "Contact" tab of the Analysis Parameters dialog.)

 

The last suggestion is to check the solver being used by looking through the log file (accessible from the Report tab). If the iterative solver was used, you could try a smaller tolerance (set on the Analysis Parameters "Solution" tab) or try switching to the sparse solver.

 

Good luck.

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
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Member
GarrettML
Posts: 5
Registered: ‎02-10-2014

Re: Enforcement of Zero Residual Force - Unconstrained Nodes in Static Linear Mo

02-13-2014 11:22 AM in reply to: AstroJohnPE

John,

Thanks for the reply. The removal of smart bonding proved to be helpful. Although the residuals were not identically zero, they were reduced to orders of 1E-17 or less. I also found that enforcing compatibility on each part of the model helped.

 

---

Garrett

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