[Gmsh] eigenvalue + eigenvectors

[Emmanuel ROBBE]

hello, 

following to my previous mail, i've found a solution that could be eaysily 
done (maybe?) : 
is there a way (plugins) which can only keep the  values > 0 of a scalar 
results and replace the others by 0. ? Same for the values <0 ?
this way by using this plugin on the eigenvalues, you can create to 
results : one for the positiv values, the others fot the negativ ones. And 
then by using the "evaluate" plugin and multiply theses fields with the 
eigenvectors,  you can create two fields of eigenvectors corresponding to 
the positive values and negatives values.

regards, 

Emmanuel ROBBE

----- Réacheminé par Emmanuel ROBBE/CNEH/DE/EDFGDF/FR le 17/10/2008 17:21 
-----


Emmanuel ROBBE
17/10/2008 16:41

 
        Pour :  gmsh at geuz.org
        cc : 
        Objet : eigenvalue + eigenvectors

hello, 

I'm currently working with gmsh in order to view the results of some 
mechanicals problems solved with Code_Aster. First of all, i want to 
congratulate you for the very good job you've done with you software : 
every time I'm using it, I 'm impressed with the hign number of ways to 
draw and use the results of the calculation.

In order to understand the behaviour of some concrete structure, i'm using 
the plugins "eigenvalues" and "eigenvectors" in order to view the main 
stress direction / vectors in the structure. Usually, i run the 
eigenvectors plugins on the stress tensor with the option 'scale by 
eigenvalue' but unfortunatly, with this methode, you can not know anymore 
if the value is positiv or negativ, wich is very interesting for us in 
order to know if there is traction or not.

The idea is to be able to represent the eigenvectors with a line with the 
followings properties
 - the direction is the one of the vectors (which is already given by 
eigenvectors)
 - the size is related to the value
 - the colors depends of the value : for exemple green color for positiv 
value, and red for negativ. This last point can ben easily done by 
choosing a custom ange with 2 intervals
So, it's a sort of mix between eigenvectors and eigenvalue : this last 
option is keeping the information of the sign of the value.
I'm currently trying to use some operation with the plugins existing in 
order to do it, without success for the moment.

With this tool, you can very easily and quicky see the way the force are 
crossing the structure and where are the weak point.

I hope you will me able to help me. Sorry for the poor english, it would 
have be more easy for me to write in french. :)

regards, 

Emmanuel ROBBE

ps : actually, i've got some others questions about this type of results's 
visualization  . Let me know if you are interesting.







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