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Showing posts from August, 2017

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

Harmonic MSUP Using the Multiple SOLVE Method

Triangle Wave by Fourier Series * In the Ansys APDL documentation of Mode-Superposition Harmonic Analysis  and other Verification Manual documentation (e.g.  VM76 &  VM149 ), only load step file method was described. Personally, I favor  Multiple Solve Method  instead because you can vary the loads for different frequencies. This could come in handy for different loads at various engine orders or rotating unbalance force. Or say if you have the Fourier coefficients of the periodic force of irregular form (e.g. triangle wave ), the steady state response can be computed. The APDL script below replicates VM183  but uses the Multiple Solve Method. Do let me know if you could recommend ways to improve the script. Script !!   Modified from VM183 to use Multiple SOLVE Method !!   Results should be identical to VM183 ! Author: Sze Kwan (Jason) Cheah ! Modified: August 27, 2017 ! Disclaimer: Use at own risk! /PREP7 ANTYPE, MODAL         ! MODE - FREQUENCY ANALYSIS MODOP

Text List of Named Selections

PADT's script on writing out named selections to a text file in the ACT Console did not work for me when I copied-and-pasted it into the ACT console. Perhaps it was meant to be used with Linux OS? I tweaked the code a little for my Windows 10, Ansys WB 18.1. Here's my take: a = ExtAPI.DataModel.AnalysisList[0]   #Get the first Analysis if multiple are present workingdir = a.WorkingDir path = workingdir.split( "\\" ) #Put the output file in the "user_files" directory for the project. slashes =  '\\' userdir = slashes.join(path[:len(path)-4])+ '\\user_files' #Use the name of the system in case the snippet is #used on multiple independent systems in the project. system_name=a.Name system_name.replace(' ','_') model = ExtAPI.DataModel.Project.Model nsels = model.NamedSelections   #Get the list of Named Selections if nsels:     f = open( "%s\\%s_named_selections_checked.txt" %(userdir,system_name), &quo

Craig Bampton Method

In a previous post , the Craig -Bampton (CB) substructuring method was used in Ansys to simplify a part for reuse. To learn more about what Ansys does in the background, I did some reading up. Here are some good resources: Resources Original Paper link FEMCI general description:  link My Go-to Primer link Tom Irvine's tutorial papers and Matlab scripts link Octave/Matlab Scripts Inspired by Tom's Matlab script, I coded a script to condense two 'random' bodies, keep only 10 modes of each body with 3 nodal interface points between them. The 'random' bodies are positive definite matrix that is generated randomly for each run to represent two mass and stiffness matrices. Running the script again would generate a different system and different plots. Here are the links to the two Octave/Matlab scripts used to create the plots below: Main Script: Random2PartsCB.m   link   (run this one) Minion Script: CraigBampton.m   link A run of the script may yie

SpaceClaim is Awesome

From the title, you could infer my feelings towards this nifty tool offered by Ansys. There are some who are still sticking to DesignModeler as their cleanup tool of choice. To those, I would implore you to give SpaceClaim a try. I believe the reason why some hold back from switching is due to the sunk cost fallacy . Learning DesignModeler has been such a significant learning commitment that giving it up becomes difficult. A little known fact: the software could be accessed for free without feature restriction for personal education via the Ansys Student . Say you get an IGES file and it only imports as surfaces. You could stitch it together to create a solid, then save it as a STL file. Same as DesignModeler, SpaceClaim plays nice inside Ansys Workbench. After going through the tutorials , here are my top tips I find useful: 1. Navigation - Alternative 2 I was tired of the indentation on my finger as I use the middle mouse button (MMB). My preference is Alternative 2 which uses