[Insight-users] ITK:FEM : FEM SOLVERS

[Barbara]

Thanks Brian,

I really appreciate your response.  I am working on a simple static 
problems.
I have created a new element, a 3D space bar, and I work with this 3D 
space bar and the tetrahedron element offered in ITK.  I've found loads 
of unconsistancies with the tetrahedron element in ITK, for example it 
took me a while to figure out the correct nodal numbering scene.  It 
turns out that if the numbering scene is wrong all solutions are wrong.  
The validation of the tetrahedron element offered in FEMElementTest, as 
far as I can tell, is wrong (tetra2.fem).  

I dont understand why this solver (Using LinearSystemWrapperItpack) is 
the only one that detects when an diagonal element in the stiffness 
matrix in negative. 

Also I will like to know if the solvers reduce the stiffness matrix.  I 
have small examples with 225 nodes that last 26 minutes to run.

I will be super glad to tell you more about what I am doing, hopefully 
getting your help I could speed up this validation stage in go into 
using ITK FEM to solve my static problems with confidence.

Thanks for your time,
Barbara.






Brian B Avants wrote:

>Barbara,
>
>The ITK-FEM framework is powerful but assumes a certain amount of
>knowledge about FEM.
>
>The three different solvers are for static (stress-strain), first-order
>time dependent (parabolic e.g. heat distributing through an idealized
>solid) and higher order time dependent (hyperbolic e.g. elastodynamics, a
>bridge oscillating) problems.
>
>These different problems need different amounts of information about
>'past' solutions that get used in the time stepping schemes.
>
>Hughes' 'the finite element method' discusses such things.
>
>It would be good to know what kind of problem you are interested in
>solving in order to help choose a solver.  Typically, we use the
>Crank-Nicolson solver for image registration.
>
>Good luck,
>
>Brian
>
>
>On Thu, 2 Mar 2006, Barbara wrote:
>
>
>
>  
>
>>Hello:
>>
>>I am very interested in knowing what was the purpose of providing 3
>>different solvers for the FEMElement Test setup.  What is the difference
>>among them?
>>More important, I will also like to know if there is someone in the
>>insight-developers that works in FEM and can answers questions about ITK
>>FEM?
>>
>>Please, let me know.
>>Barbara.
>>
>>
>>
>>_______________________________________________
>>Insight-users mailing list
>>Insight-users at itk.org
>>http://www.itk.org/mailman/listinfo/insight-users
>>
>>    
>>
>
>
>  
>