Strain in

[pvsantos]

Hello,

I am using Elmer to calculate eigenmodes of elastic structures. The solver (part of the input file is listed below) yields the displacement field, which can be visualized using ElmerPost. I wonder whether one can also calculate the Strain field (and visualize in ElmerPost). I tried to include "Calculate Strains=Logical True" in the equation section, but the strain results are not stored in the *.ep file. Is there a simple way to get the strain (of stress) field for the eigenvectors?

Thanks in advance

Paulo

*************************************************************
Solver 1
Equation = Linear elasticity
Eigen System Shift = 11e6
Eigen System Values = 1
#Procedure = "StressSolve" "StressSolver"
Procedure = "StressSolvePML" "StressSolver"
Variable = -dofs 3 Displacement
Eigen System Select = Smallest magnitude
Eigen Analysis = True
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-8
Nonlinear System Max Iterations = 1
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Direct
Linear System Direct Method = Umfpack
End

Equation 1
Name = "Equation 1"
Calculate Strains = Logical True
Active Solvers(1) = 1
End

***************************************************************************************************

[pmanandhar]

Hi Paulo,

What I have found is that Calculate Stresses = true works as described in the ElmerModelsManual.pdf->Linear Elasticity Solver.
The elastic constants can then be used to get strains from the stresses.

The output has VonMises as well as stress tensor components Stress.1 to Stress.6

I assume the following, but trying to dig into the code or try a simple model to find out:

Stress.1 = tau_xx
Stress.2 = tau_yy
Stress.3 = tau_zz
Stress.4 = tau_xy = tau_yx
Stress.5 = tau_yz = tau_zy
Stress.6 = tau_zx = tau_xz
Correction: Stress.5 = tau_xz, Stress.6 = tau_yz


I think this is correct (see: viewtopic.php?f=4&t=1376&p=5145&hilit=stress+1#p5145)
[Stress components are: 11, 22, 33, 12, 13, 23]


Cheers, Prakash.

[pvsantos]

Dear Prakash,

thanks for the reply!
Calculate Stresses works for regular calculations, but not for Eigen Analysis (this was the subject of my previous message). I wonder if there is a way to get the stresses (or strains) for the eigenvalues.

Regards,

Paulo

[raback]

Hi

I think this may be a postprocessing issue. The generic saving of eigenmodes has not just been implemented in ElmerPost format. Try ResultOutputSolve + vtu output + Paraview.

-Peter

[raback]

Hi

Look at the recent consistency test "StrainComputation03". That provides with an example.

-Peter

[pvsantos]

Hi Peter,

thanks again. I could not find "StrainComputation03". Can you please send me a link to this file?

Regards,

Paulo