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Need Help - Excessive Pivot Ratios Error

Experimenter
Experimenter

Hello,

 

I'm currently using NX 9.0 and am trying to perform an FEA on a part that I made. I have fixed constraints, a material selected, and a specified load, but I can't get the results to display. The results are not showing up because of the errors shown below:

NASTRAN Msg: *** USER WARNING MESSAGE 4698 (DCMPD)
STATISTICS FOR DECOMPOSITION OF MATRIX KLL .
NASTRAN Msg: ^^^ USER FATAL MESSAGE 9137 (SEKRRS)
^^^ RUN TERMINATED DUE TO EXCESSIVE PIVOT RATIOS IN MATRIX KLL

 

I have three fixed constraints on my part, so it shouldn't be able to rotate in any way. The load that I selected is just a gravitational force applied to the entire body. The only thing that I can think of is that the model thinks that all of the extrusions that I made while designing the part are not connected. All of the extrusions were definitely touching the face of whatever section of the part that I extruded from though. Does NX automatically connect extruded components together after making the whole part into a mesh or do I need to constrain these to each other? When I hover over my meshed part it highlights the entire part like it is one peice, but I know when I went to make the mesh I had to select all of the extrusions individually as if the program thought they weren't already connected.

Any help would be greatly appreciated. I would be glad to upload or send someone my .sim and .fem files if someone wants to open the file to look at my constraints and such. Also, I should mention that I am very new to NX still, so please explain in detail how I should fix the problem as I'm still learning.
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Thanks!

3 REPLIES

Re: Need Help - Excessive Pivot Ratios Error

Solution Partner Legend Solution Partner Legend
Solution Partner Legend
Hello,

I suggest that you create a Sol 103 normal modes solution, and apply the same constraints. The mode shapes should indicate to you where the model connections are missing.

You can also visualize free element boundaries in the fem using element outlines.

Phil

Philippe Tremblay
phillippe.tremblay.ext@siemens.com
www.mayahtt.com

Re: Need Help - Excessive Pivot Ratios Error

Solution Partner Genius Solution Partner Genius
Solution Partner Genius

Hello Speeding944T,

 

Noted that you have applied 3 fixed constraints, but your error is suggesting your simulation model is unstable. Probably your existing constraints are still not enough. Try increasing the nodes involved for constraints, or add more constraint definition.

 

I do not understand what is the meaning for connecting extruded component.... Separated meshes created from separated polygon bodies remain separated, unless you did mesh mating, or gluing definition. And if you really have more than 1 mesh, 3 constraint definition does not seem enough. 

 

Hope it helps.

Tuw

Re: Need Help - Excessive Pivot Ratios Error

Siemens Valued Contributor Siemens Valued Contributor
Siemens Valued Contributor

Hi

 

As others have mentioned, I think the issue is almost certainly that your parts are not connected.  Use either mesh mating or glue connections to address this.

 

Regards

Joe