How to solve "STIFFNESS MATRIX SINGULAR OR NON-POSITIVE DEFINITE" error?

[Anonymous]

I have a 235,710 element model that fails with the error in the Title. Four elements are listed as having singular geometry. The model has in the past successfully completed, but it is very unstable and slight changes (increase/decrease in load) cause it to fail.

Is there a way to locate the four elements having a singular geometry? Also, any guidance on how to solve this error and make the model more stable would be greatly appreciated.

Thanks,

John

[James.Youmatz]

Hi @Anonymous ,

I would be curious to see the design. Can you share it with me? It can be dependent on the shape, but I usually look at the mesh and try to see any sliver faces, or potentially overlapping/singularity areas. The last time I saw this error message, the model had threads on a rod - and once the threads were removed in the Simplify environment, the error did not come back (regardless of load changes).

Thanks,

[Anonymous]

Hi James,

Thank you for the reply and offer to review the model. Can you provide your email for me to share it with you?

Thanks,

John