Hi, I have thought about the problem again and now I have a solution proposal:
[[ u_i ]] = 0, would I fulfill by adding entries in the constraint matrix. E.g. u_i = u_j for each DoF pair on the boundary. I just have to figure out the DoF indices i and j. The average overall stress state, I want also archive with the constraint matrix: For the first DoF of the periodic boundary pair I would add a constrain like u_1 = A_1i u_i + A_1j u_j + ... + A_1N u_N + S_kl N_l u_1 = sum_i^N ( A_1i u_i ) + S_k N_l with i=2..N (all DoF indices on the periodic boundary), the prescribed stress tensor S and a global normal vector of the boundary N. And the coefficients are the the calculated by A_ij = C_ijkl sym(u_k,l) n_j Jwxq on the corresponding faces by iterating in standard fashion over all cells/faces and evaluating the terms with via FEFaceValues. [[ t_i n_i ]] = 0 should thereby be indirectly satisfied. But I'm not sure if the evaluating the coefficients in such a manner, leads in the end to the wanted behavior of the system (stress fluctuations on the boundaries but an average prescribed stress tensor). Is it a good idea to include coefficients in the constraint matrix that depends on some shape function. I thought those belonged in the system matrix. Can this still work? Another issue is how to make this concept work in a parallel context: Which process must know about which DoF? Regards, Lukas Schöller -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/ad96305f-99d0-4ca4-b37e-b68b0f0f9f93%40googlegroups.com.