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Linear static solid contact erroneous results


I was just trying out a simple double lap joint config with contact enabled. The analysis was SOL 101. All geometry was represented using solid CHEXA elements in NX Nastran.


CAD Model SetupCAD Model SetupSet up in FEMAPSet up in FEMAP01.PNG


I don't understand the brown color of element faces for the pin. What does it mean? Never seen it before.

Contact Property DefinitionContact Property DefinitionResults :)Results Smiley Happy

I am not sure what I am doing wrong. I have attached a copy of the dat file. I would appreciate some help in resolving the above problem.




Re: Linear static solid contact erroneous results

  1. Definately do the tutorials.  Your question about "brown faces" tells me you don't know that FEMAP illustrates contact region definition in this manner.
  2. Build your model progressively (1 clevis + pin → Full Clevis with pin → Clevis + Pin + Lug) and check each part of the build via static and 6 zero runs.
  3. Further, when doing your debugging, start with all contact regions as "gluded", then progressively change them to "contact".  You'll isolate the individual contact region problems that way
  4. In your last shot I don't see any contact regions between lug and clevis faces.  What keeps your lug stable?
  5. I did not review your *.dat...I generally don't download zip files.

Re: Linear static solid contact erroneous results

[ Edited ]

Hi EWeiner,

Thx for your suggestions. 


I was just about to post my response about figuring out what the brown faces in Femap means. I have done some contact analysis before but its been a while. I guess I was a little preoccupied with figuring out the reason behind deformation pattern and the brown coloring appeared as an unknown surprise. 


I suddenly realized about an hour ago while driving that Femap represents the contact regions using brown color! 


I will try your other suggestions including starting out with a simpler model and progressivley increase the complexity. 

Re: Linear static solid contact erroneous results

Sounds like you're on your way!


Keep thinking modeling is like the parts up and continually check (with analysis runs) as you go.

Re: Linear static solid contact erroneous results

Wanted to report here that I was able to successfully run the double shear lap joint analysis with contact and arrive at results which are satisfactory. One of the key things was to create a contact pair between middle plate and top/bottom respectively and model the bolt head/rivet head.


I would like to thank EWiener for his suggestion on the first part.