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Nagativ eigenvalues in matrix
2

Nagativ eigenvalues in matrix

Nagativ eigenvalues in matrix

(OP)
I get two warning massages:

1. Strain output request le is not valid for some elements in this analysis. The request is switched to the strain measure, e.   and

2. The system matrix has ... negativ eingenvalues.

and the job stops with the Error "too many attempts for an increment".

What is the reason of the strain putput request?

Thanks

RE: Nagativ eigenvalues in matrix

If you have nonlinear geometry enabled, the default strain output request is LE (logarithmic strain measure).  However, this strain measure is not available for some elements, like beams.  The warning is issued to let you know that the strain output request is being changed by the software.  It should not affect the convergence of the solution.  

RE: Nagativ eigenvalues in matrix

Engelien01,

Negative eigenvalues usually mean not enough constraints leading to rigid body motion.

Gurmeet

RE: Nagativ eigenvalues in matrix

(OP)
Thanks for the help! Both were helpful to solve same negativ eigenvalues, but I still have one and I have really no idea how to fix them...

RE: Nagativ eigenvalues in matrix

(OP)
now I have no warnings anymore..

But Error "too many attemps for an increment" *grr*

RE: Nagativ eigenvalues in matrix

You could try to reduce the initial/minimum and maximum time  increments for the step causing the error.

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