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Negetive Eign Value

Negetive Eign Value

Negetive Eign Value

(OP)
My beam model worked fine for a small load. However, whenever I was trying to give a large load, its giving me an warning massege  "2 negative eign values" and followed by an error message. I am sure the load is not too much for the model. Any one have any idea whats going on and how I can avoid that problem.
 

RE: Negetive Eign Value

did u try to re-fine the mesh?

RE: Negetive Eign Value

If it is a very long beam, change the element type to hybride beam element may help.
Or you would like to try using stabilization in the step to check is if there is an error in the model such as material.

RE: Negetive Eign Value

Hi

What is the error message that you get?

Regards

Martin

RE: Negetive Eign Value

Did you set NLGEOM to ON ?

RE: Negetive Eign Value

(OP)
The Error Message is "Too many attempts...."

Yes, I Set Nlgeom to on.I think that is why the beam is distorting too much.

RE: Negetive Eign Value

have you tried the method I suggested?
And turning The NLGEOM On is a must in large deformation analysis in order to get the correct result.

RE: Negetive Eign Value

Try reducing the minimum time step size.

Regards

Martin

RE: Negetive Eign Value

or you could try changing the displacement tolerance to 100%. This relaxes the controls so the solver won't crash when it senses that the deformation is too big compared to the default spec.

try adding *controls after your *step. It helps with my solution sometimes.

*Controls, parameters=field, field=displacement
 , 100.0

RE: Negetive Eign Value

This type of negative eigenvalue warning is often caused by the structure starting to buckle. Have you done a buckling analysis to see if you indeed are loading it in such a way as to induce buckling?

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