Ansys Tips

Photo by  James Owen  on  Unsplash A surprisingly popular blog-post written here is Exporting Stiffness Matrix from Ansys . A sensible follow up question is what can one do with the exported stiffness matrix? In a recent Xansys Forum post, a question was raised on how we can edit the stiffness matrix of a superelement and use it for our model.  An approach presented below is to first create a superelement that has the same number of DOF and nodal location that will serve as a template. An APDL script can then be written to edit the stiffness matrix entries as desired before exporting to a new superelement *.SUB file for use in future models. The self-contained script below demonstrates this.  /prep7 et ,1, 185 mp , ex, 1, 200e3 mp , prxy, 1, 0.33 w = 0.1 ! single element (note nodal locations) n , 1, w, -w, -w n , 2, w, w, -w n , 3, -w, w, -w n , 4, -w, -w, -w n , 5, w, -w, w n , 6, w, w, w n , 7, -w, w, w n , 8, -w, -w, w e , 1, 2, 3, 4, 5, 6, 7, 8 /solu anty...

It is sometimes useful to extract the mass and stiffness matrix from Ansys.     *SMAT, MatK, D, IMPORT, FULL, file.full, STIFF       *PRINT, matk, matk, txt Exporting mass matrix would be similar:       *SMAT, MatM, D, import, full, file.full, MASS The above script uses APDL Math to get the job done. (Please see previous post for another example). The ordering of the matrix is unfortunately not concurrently exported. To verify the sequencing is as expected, we will work to replicate a truss example in the  Finite Element Trusses course notes by Bob Greenlee. Figure 1: Truss Problem Setup Model Creation Script to create model: /prep7 !! Creates Model to reflect course notes ! Properties et ,1,1  mp , ex, 1, 29.5e6 r , 1, 1 ! Geometry n ,1 $  n ,2, 40 $  n ,3, 40, 30 $  n ,4, 0, 30 e ,1,2 $  e ,2,3 $  e ,1,3 $  e ,3,4 ! Boundary Conditions d ,1,ux,0 $  d ,1,uy,0 d ,2,uy...

I read about APDL Math a few years ago with much intrigue. A very interesting write-up about it can be found here . What stood out to me was the possibility of computing modal sensitivity relative to different variables similar to what SOL 200 offers in NASTRAN for optimization. Web Resources Ansys Help Document : The commands are documented though the available examples are limited PADT Blog Post : Eric's article gives a good overview of the capabilities Ansys Knowledge Resource #2025879 : Additional guidance in usage. PADT Blog Post  [Edit: Sept 12, 2017]: Awesome post! Results back in 'User Ordering'! AnsysTips Blog Post [ Edit:  Oct 11, 2017]: Export Stiffness Matrix Unfortunately, that's about all I could find anywhere. APDL Math Example Overview DOF ordering is not addressed here. I have not yet figured out a good way to do it yet so please share if you can convert to the 'user ordering' all in one shot. Please see the script on how the solu...