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...

Fig 1: Project Schematic With the release of Mechanical 19.2, substructuring is now available for Modal & Rigid Dynamics without scripting. That just made my  earlier post on CMS outdated! Note that there is still a key limitation where Generation and Expansion Pass must be performed on your local machine. To get ahead of the game a bit, here is a way to do Harmonic Analysis extending on previous work . (Please go through that before this post). Some points of note: The method of merging the CMS and non-CMS models together into System C is the same. All files related to the superelement has to be copied over to the solver file directory as before. Modal analysis need not be performed first as the example here uses Full Method instead of Modal Superposition for simplicity.  The script expands the responses the same way as Modal Analysis does so the script will look familiar. Command Snippet for Combined Analysis D !!!!! Save full model fini /filnam...

Figure 1: CMS Reuse Project Schematic In the previous two posts ( here and here ), the workflow requires another generation pass when reusing the model. This diminishes the advantage of using a component mode synthesis (CMS) superelement model. The difficulty is that when the model changes, the superelement node numbering no longer matches the new workbench (WB) model. Everything gets shuffled around. To reuse a superelement body, we need the  nodes to persist in the final Analysis for expansion. Strategy We start out with an original modal analysis ( Analysis A ) that would have worked on it's own. Next, the original modal analysis is duplicated (becoming Analysis B ). Analysis A will be modified to only have the superelement body while  Analysis B will be modified to have the geometry and mesh of non-superelement body. When both analysis are assembled into a new modal Analysis C , Analysis B 's element and nodes are automatically offset so that ...