What is the recommended way to implement the symmetric fourth rank tensor of elasticity?

[stefan]

I am really blocked since I know more but I read a document which succeeded in making that here my program with the same problem.

Linear elasticity with an anisotropic material

thank you for your answer. I have done this but I receive errors here is the form in voigt notation. That’s why I wonder where is the problem.Because I do not really know what to do anymore from fenics import * from mshr import * import numpy as np from math import * from matplotlib import pyplot as plt from dolfin import * import matplotlib.cm as cm import matplotlib.tri as tri from mpl_toolkits.axes_grid1 import make_axes_locatable import ufl c_11 = 1.19e11 c_12 = 0.84e11 c_13 = 0.83e11 c_33…