Eigen - complex

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Jhno
Posts: 214
Joined: Sat May 05, 2012 2:55 pm
Location: Laval

Eigen - complex

Post by Jhno » Thu Feb 23, 2017 6:30 pm

Hi,
when I issue the command eigen -fullGenLapack 5, I get the following warning :
- the eigenvalue 37 is complexe with magnitude 1
- the eigenvalue 38 is complexe with magnitude 1

I wonder why do I get this warning since I only asked for the first 5 values?

fmk
Site Admin
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Location: UC Berkeley
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Re: Eigen - complex

Post by fmk » Mon Feb 27, 2017 11:42 pm

need to see the script.

Jhno
Posts: 214
Joined: Sat May 05, 2012 2:55 pm
Location: Laval

Re: Eigen - complex

Post by Jhno » Wed Jun 28, 2017 7:05 am

The code is too long to post here. I however have funny result with this little code here :
wipe
model BasicBuilder -ndm 2 -ndf 2
node 1 0. 0.
node 2 1. 0.
node 3 1. 1.
node 4 0. 1.
fix 1 1 1
fix 2 1 1

set mDen 2000.
set WY [expr $mDen*9.81*-1]
set thick 1.0
set type PlaneStrain
nDMaterial ElasticIsotropic 0 100e3 0.3 2000.
element SSPquad 1 4 3 2 1 0 $type $thick 0. $WY
system FullGeneral
test NormDispIncr 1.e-5 20 1
constraints Transformation
integrator LoadControl 1 1 1 1
algorithm KrylovNewton
numberer RCM
analysis Static
analyze 1

Try the following :
eigen 1
Then :
eigen 2
Then :
eigen 3
Now compare with
eigen fullGenLapack 3
eigen fullGenLapack 2
why is this happening? In my larger model, when I issue eigen fullGenLapack it nevers print anythin and I have to kill the program. I am afraid of using eigen command because results looks wrong.

selimgunay
Posts: 913
Joined: Mon Sep 09, 2013 8:50 pm
Location: University of California, Berkeley

Re: Eigen - complex

Post by selimgunay » Thu Jun 29, 2017 1:38 pm

eigen command generally works properly.

To explore the source of the problem, could you change the material to uniaxial elastic and assign masses to the nodes.

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