Re: About the stiffness matrix
Thanks for your patient instructions, and I have solved the former problems under your help. But I’m sorry to have to bother you again. I could get the stiffness matrix with expected shape now, but the matrix elements are all zeros! I guess it’s most likely to go wrong in the material definition and term selection as well as term implementation steps. I have attached my code snippet together with the mesh used and a description file. Could you please help me check what’s wrong with my code snippet, especially my material definition part, and see if I have chosen the right terms to build equations? Thanks!
On 8/24/22 07:56, jhchen via SfePy wrote:
Thanks for your patient instructions, and I have solved the former problems under your help. But I’m sorry to have to bother you again. I could get the stiffness matrix with expected shape now, but the matrix elements are all zeros! I guess it’s most likely to go wrong in the material definition and term selection as well as term implementation steps. I have attached my code snippet together with the mesh used and a description file. Could you please help me check what’s wrong with my code snippet, especially my material definition part, and see if I have chosen the right terms to build equations?
You did not assemble the matrix by calling pb.equations.eval_tangent_matrices().
See the attached script. I changed dw_diffusion to dw_laplace, as D is isotropic. I also had to split the material, because the per-region definition seems not to work with the surface integrals.
r.
Thank you so much for your help! It now goes quite well except a minor glitch, and I guess this mostly likely relates to the former mesh problem. After loading mesh, it showed that the mesh.cmesh.n_coor was 23996, which means there were 23996 nodes in total. Then the domain was created with a warning: bad element orientation, trying to correct... corrected. And then I called omega = domain.create_region('Omega','all'), node_list=omega.entities[:,0]. Ideally the node_list should be in length 23996 and contain all node indices from 0 to 23995. However, len(node_list) = 23989 with several indices missing. Is this because of my bad file file and some nodes were deleted during the domain = FEDomain('domain',mesh) process? The final stiffness matrix K results in shape (23989,23989). I try to utilize this matrix by deleting my original nodes which are not in node_list. Is it appropriate to do so or what should I do to match the stiffness matrix to original nodes?
participants (3)
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jhchen -
jiahao chen
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Robert Cimrman