Dear community/developers, I am using FEniCSx 0.9 with Docker on Microsoft Windows. In the MWE posted below, I perform a 2-D displacement-controlled FEA and compute the displacement U_disp_ctrl and stress sigma_disp_ctrl. What I am interested in is: imposing tractions obtained by t_N = ufl.dot(sig…

Ah, if I understand your question well, then you’ve run into one of the more elegant but challenging bits of math in finite element analysis: flux extraction. Essentially, one should not evaluate the fluxes (i.e., traction in the case of elasticity/linear momentum equations) as simply the stress op…

Dear Stein, Thank you very much for your clear explanations and for directly pointing out the problem! As per your suggestion, I tried to find t_N out of a surface projection problem, for which the code is attached below: import dolfinx from dolfinx import fem import ufl import dolfinx.fem.petsc …

Dear Dokken, Thank you very much for your prompt and very helpful reply! I had to adapt the source you suggested a bit to match my problem and my dolfinx version, but the overall approach worked very well. Now the code runs in parallel too, and I achieve consistency. For the reference of other p…

Sorry for bothering you again! With this approach of setting the diagonals to one, do we still incur a cost of solving a big system of equations for all the dofs, or, is it only the cost of solving a small system for the specific boundary dofs? In case it is the big system, could you please explai…

The matrix will still be big. However, as the diagonal is an identity, the cost of solving the system with these are very low.

Consistency between displacement-controlled and load-controlled FEAs

dolfinx

dokken November 26, 2025, 10:33am 4

Have you considered: Modify matrix diagonal -- dolfinx version for A.ident_zeros() - #3 by dokken

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Consistency between displacement-controlled and load-controlled FEAs

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