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Run Terminated Due To Excessive Pivot Ratios In Matrix KLL.

Creator
Creator

Hello Guys, How are you ?

 

I just graduated, so i started performing some analysis using FEMAP v10.3 besides that i was using SolidWorks Simulation to run my simulations.

 

Usually i model the part using solidworks and then import it to FEMAP. I am having problems to run this study, always getting the same error : " RUN TERMINATED DUE TO EXCESSIVE PIVOT RATIOS IN MATRIX KLL" i was aware that this error is due to the parts of the model are not connected or your model is not correctly constrained. To fix this you have to:

1- Change your fixtures.

2- Merge nodes.

3- Connect faces.

 

I tried all of this solutions but i did not get my problem solved. Could someone help me ?

 

 

8 REPLIES 8

Re: Run Terminated Due To Excessive Pivot Ratios In Matrix KLL.

Gears Phenom Gears Phenom
Gears Phenom

Run Modal analysis. If model is poor constrained then you get modes with near zero values (like 1e-6...1e-3) - they called "rigid body modes". Unconstrained parts of structure move without deformation at these modes. Now you can see what parts need to be fixed.

Re: Run Terminated Due To Excessive Pivot Ratios In Matrix KLL.

Siemens Phenom Siemens Phenom
Siemens Phenom

Where are the curved tubes in your model? Can you explain where/why you are using the curved tube properties versus the tube property. 

Re: Run Terminated Due To Excessive Pivot Ratios In Matrix KLL.

Creator
Creator

Hello Karachun, thanks for replying !

 

I performed modal analysis, and changed the property as T_Giampietro said. This is the outcome: 

 

NO EIGENVECTORS COMPUTED FOR COMPONENT MODE SYNTHESIS OR SYSTEM SOLUTION.

 

Range of interest: from 0 to 100.

Re: Run Terminated Due To Excessive Pivot Ratios In Matrix KLL.

Gears Phenom Gears Phenom
Gears Phenom

Can you post the model?

Re: Run Terminated Due To Excessive Pivot Ratios In Matrix KLL.

Creator
Creator

Yes, here it is.

Re: Run Terminated Due To Excessive Pivot Ratios In Matrix KLL.

Siemens Phenom Siemens Phenom
Siemens Phenom

It will run if you change the property to a beam using the same cross section. To do this use Modify > Element > Type, select all elements and create a new beam property with a circular tube cross section. 

Tube to Beam.png

Re: Run Terminated Due To Excessive Pivot Ratios In Matrix KLL.

Creator
Creator

Hello T_Giampietro, thanks for replying !

 

Do you know why tube property doesnt work ?

Re: Run Terminated Due To Excessive Pivot Ratios In Matrix KLL.

Gears Phenom Gears Phenom
Gears Phenom

According to the NX Nastran Element Library CTUBE element is similar to CROD and CROD have only axial and torsional stiffness but no bending stiffness.

Снимок1.JPGСнимок2.JPG