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Defining Ansys Superelement SUB File Manually

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 antype , substr     ! analy

Ansys Workflow

Everyone has their own workflow in doing their analysis with different goals and preferences. Here's mine and a reasoning of why I do so. I would be eager to hear thoughts from other people on this subject.
  1. Geometry Cleanup in SpaceClaim
    • The first step here is self explanatory. The litmus test is a crude mesh.
    • Simplification of the model while maintaining objectives is next.
  2. Named Selection in SpaceClaim
    • For a middle to large size model, every object I need in Mechanical gets a Named Selection. This is critical in organizing contacts and mesh properties. Modeling decisions gets clarity at this stage. 
    • Rotating, hiding different parts and visualization is simply just easier in SpaceClaim compared to Mechanical. 
    • If any geometry changes needs to be made, much of the model could be reused (e.g. contacts, boundary conditions). 
  3. First Pass Analysis
    • The first analysis is usually very crude. The goal is to have a minimum viable product on hand that can be shared with the customer. We can then talk through the assumptions and risk/benefits of future analysis, sensitivity studies, parameter exploration etc. 
    • Going further without talking to the customer is risky as it may waste precious time chasing unwanted goals.
  4. Accumulate Additional Layers of Analysis Complexity
    • The first pass analysis has a lot of assumptions. By peeling away the assumptions, there are trade offs like solution time, untested scripts etc which can be isolated for faster iterative troubleshooting. 
    • Exporting the model to ANSYS Classic is sometimes done at this point for custom scripts testing. Standalone simple models with expected outcomes may be also created at this stage to verify implementation.
    • Any significant results are shared with the customer. It could be just a simple screenshot and a phone conversation but it heads off any surprises later. This also aids the customer in making design decisions in parallel to the analysis. 
  5. Report Writing
    • Not very sexy. This benefits from proper file naming and documentation of assumptions during analysis. 
    • As a legacy document, a well written report will help peers and successors recreate and build on the work.