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plot deformation

+1 vote

Hi, I want to plot the deformation map of a 2D elasticity problem.

I tried the following code, but it does not work, last line of code bring following error message : All terms in form must have same rank.

W = TensorFunctionSpace(mesh, "Lagrange", 2)
F = grad(u) + Identity(2)
E = 1/2*( F.T*F-Identity(2))
Ep=project(E,W)

Thank you in advance for your help, and for any references concerning the plot function.

related to an answer for: Plot my Stress Tensor Components
closed with the note: Question was answered !
asked Jan 15, 2015 by Claire L FEniCS User (2,120 points)
closed Jan 16, 2015 by Claire L

This code chunk worked fine for me (assuming that u is a vector). Have you tried using 0.5 instead of 1/2 in E? May be a problem with integer division if using Python version below 3.0.

commented Jan 16, 2015 by joakibo FEniCS User (1,140 points)

1 Answer

+1 vote

Yes you're right ! I've added a few lines to save deformation tensor in vtk format and open it with paraview :
file_E = File("deformations.pvd")
file_E << Ep
I wonder why it is saved with 9 components whereas my problem is in 2D (I saved displacement field in a separate file, and it also has 3 components instead of 2) ?

answered Jan 16, 2015 by Claire L FEniCS User (2,120 points)

Hi, 2d vectors and tensors are always padded with zeros to fill in the entire 3d vectors and tensors. See here.

commented Jan 16, 2015 by MiroK FEniCS Expert (80,920 points)

Ok, thanks ! So this is just for the output right ? I was wondering whether I correctly defined vector's dimension in my code...

commented Jan 16, 2015 by Claire L FEniCS User (2,120 points)

Yes, it just for the output.

commented Jan 16, 2015 by MiroK FEniCS Expert (80,920 points)
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