{"id":186767,"date":"2021-07-28T01:35:06","date_gmt":"2021-07-28T01:35:06","guid":{"rendered":"\/forum\/forums\/reply\/186767\/"},"modified":"2021-07-28T01:35:06","modified_gmt":"2021-07-28T01:35:06","slug":"186767","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/186767\/","title":{"rendered":"Reply To: How to Create a Stiffness Matrix in APDL"},"content":{"rendered":"

Dear Mr. Erik
\nMANY, MANY thanks for sharing the link<\/strong>. It was really helpful. This is what I did to get the stiffness matrix.
\nFirst, I open ANSYS Product Launcher<\/strong>. I defined the “Directory (or Folder)<\/strong>” where all the files could be generated or saved. Then, I executed my APDL code line by line. However, I am getting an error message when I am executing the command “combine, full<\/strong>!! combines all file*.full into file.full”.
\nYes, there is NO “file0.full” file in the Directory (or Folder)”. Is this error a concern <\/strong>not to provide the stiffness matrix properly? Could you please let me know?
\nHowever, my APDL code generates the MatK <\/strong>(name of the stiffness matrix) file properly. I am using Truss element (Link180<\/strong>). I am also using “1 element<\/strong>” model. So, I have only 2 nodes<\/strong>. Hence, the stiffness matrix will be a (2×2<\/strong>) matrix. After applying the Boundary Condition<\/strong>, the stiffness matrix from MATLAB <\/strong>is as follows:
\nI am using the *dmat <\/strong>command to create the dense stiffness matrix. Then, I am opening the MatKMMF.text file. This is what I am getting (as shown below). So, how to READ <\/strong>the file? Does it mean that K(1,1) = 1E6<\/strong>? Could you please correct me? Does APDL start the Row and Column numbers from ZERO<\/strong>? If so, then why I am NOT getting the K(0,0) = 1, K(0,1) = 0, and K(1,0) = -1E6? Could you please correct my understanding?
\n
\nThis is my APDL code. Is there anything wrong in this file?
\n!! Extracting Stiffness Matrix from ANSYS APDL<\/p>\n

finish!! It will finish all previous work
\n\/clear!! Clean woking window
\n\/title, How to Get Stiffness Matrix?
\n\/prep7!! Enter to pre-processor<\/p>\n

!! Choose a proper element type
\net,1,180!! et – element type
\n!! Define sectional properties
\nA=1!! Area, in^2
\nr,1,A!! r — real consant number
\n!! Define material
\nmp,ex,1,10e6!! mp — material properties
\nmp,prxy,1,0.3!! mp — <\/p>\n

!! Make FE Model, make nodes and elements
\nL= 10!! L — length, 10 inch
\nk,1!! n — making nodes
\nk,2,L
\nL,1,2
\n!! Make elements
\n!! Before making elements, we must recall ID #
\ntype,1!! type — element type
\nreal,1!! real — real constant
\nmat,1!! mat –materials
\nesize,,1 !! ONE Element
\nLmesh,all
\nelist
\n!! Apply BC- Boundary Conditions
\nd,1,all,0!! d — dof at nodes<\/p>\n

!! Apply force
\nf,2,fx,1000!! f — force at nodes
\nalls!! all select<\/p>\n

\/solution!! enter solution
\neqslv, sparse!! Equation solver
\nwrfull, 1!! Stops solution after assembling global matrix
\nsolve!! solve
\nfini!! finish with solutions
\nsave<\/p>\n

\/aux2!! Enters the binary file dumping processor
\ncombine, full!! combines all file*.full into file.full
\nfinish<\/p>\n

! Gets Stiffness Matrix
\n*dMAT, MatK, D, import, full, file.full, stiff
\n*dMAT, Nod2Bcs, D, import, full, file.full,NOD2BCS
\n*print, MatK, matk.txt! Exports Stiffness to Text File
\n*export, MatK, mmf, matkMMF.txt<\/p>\n

Any feedback will be highly appreciated. Thanks
\nAwlad.<\/p>\n

<\/p>\n","protected":false},"template":"","class_list":["post-186767","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t