On 7/10/20 9:15 AM, David F wrote:
I have a 2D system for which I create the stiffness tensor of an isotropic material, but for each finite element I create it with a different shear modulus. The shear modulus is random for each element (I use an exponential distribution, but any distribution leads to the same behavior as long as the std is high), with no structure such as layers or anything else. In this case, the system should clearly be macroscopically isotropic (up to statistical fluctuations due to the random properties) for symmetry reasons.

At least in the limit h->0 I agree. For finite mesh sizes, I would expect that the material has a degree of anisotropy that goes to zero as you make the mesh smaller. It is true that the axes of anisotropy should be oriented in random ways for different realizations of the same experiment on the same mesh. When you do your computations, have you checked (for different realizations of the random process): (i) whether the orientation of anisotropy is always the same, and always related to the principal directions of the mesh?
(ii) how the magnitude of anisotropy behaves as you refine the mesh?

Best
 W.

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Wolfgang Bangerth          email:                 [email protected]
                           www: http://www.math.colostate.edu/~bangerth/

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