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Batch running stress recoveries

  1. Kevin Wang

    Hey all, I've been using VABS the past few months and have the workflow fully working from prevabs all the way to stress recoveries.

    Looking now at ways to batch run stress recoveries for hundreds of cases to speed up the workflow there.  For awareness, using Pre-VABS/VABS to create the beam properties, then RCAS to generate loads.  Here's what I'm envisioning the workflow to look like:

    1) Script #1 -  Convert RCAS outputs to stress recovery inputs.  I've been doing this in pre-VABS to get the -v option to visualize the result, however I realize this can be done in VABS as well, is there one recommend?

    2) Script #2 -

        a) Search through folders and pull all outputs (_lss.msh appears to hold all the elemental strains and stresses) into dataframe.

        b) Pull input file to create another table that defines each element relative to their material (which file is this?)

        c) Go through all cases, create summary table showcasing each element, their material, their max/min strains/stresses, and their respective case number that created the result

        d) Summarize table either further to than output a final table, one row for each material, their max/min strains/stresses, and their respective case number

    Has anyone done anything similar for any of these steps, especially 2a, 2b, and 2c?

    Tips/tricks would be appreciated, thanks!

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    Replying to Kevin Wang

    1. Wenbin Yu

      Please try It should be able to do what you want to do. I am not sure what is the purpose of visualizing stress, VABS not can compute the strength ratio (safety factor) distribution over the section under a given load. I thought this might be something you are after instead. 

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    2. Kevin Wang

      Looking through the documentation, it doesn't appear to be more catered towards optimizing the creation of beam properties instead of using an pre-defined property and running a bunch of cases, however I will look through it and see if I can tailor it for my needs.

      However, the 0.4 release only appears to have linux installations, while the documentation states there's a windows one.  Do you have the windows installer?


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      Replying to Kevin Wang

    3. Wenbin Yu

      Yes, we have windows installer. It will upload to the site in a few days. We can easily make changes to the code to accommodate the batch running of results. I don't quite understand what you try to achieve using Script #2. To identify max and min stresses for each element among all the load cases? As I said, strength ratio might be better indicator (it consider the interaction of multiple stresses/strains based on a failure criterion). 

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    4. Kevin Wang

      Thanks, much appreciated.

      Yes, Script #2 is basically parsing through all the outputs and summarizing it.  I'll be computing the margins on my end in the script, for which the failure criterion depends on the material.

      I've been looking through the outputs  but can't figure how to pull what material each element belongs to (question 2a).  It looks like there's a section called "Elemental Layup Definitions" under .sg.ech, but the numbers don't appear to correspond to anything.  Any tips there?

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    5. Wenbin Yu

      I still cannot understand why you want to compute margins yourself. You can a failure criterion for each material. We have 5 failure criteria build in for either isotropic materials or composite materials. You can also provide a user defined criterion.  VABS automatically does it for you without you processing the stress/strain and do the calculation yourself. 

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    6. Kevin Wang

      Sorry I'm just used to post processing everything in the raw strains/stresses for flexibility.  We use a similar approach for our full vehicle level finite element models so we can use the same post processed file for different things, such as strength margins, fatigue/fracture schedules, etc.

      From what you're saying, it seems like the best way in VABS is just to have it calculate my margins and we would just modify the input files and run the whole deck again anything we want to change anything.

      I'm currently running VABS III but update to 4.0 in the next week, thanks!

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    7. Wenbin Yu

      If you choose to do it yourself, VABS can also output stresses for each element. To relate each element with a particular material, you need to to use the element material definition, and layup definition. 
      If format_I is not equal to one, then material_type is directly used in the element. 
      If format_i=1, layer_type is used, then use layer definition to find the material type. 

      However, you also need to use the stresses/strains in the material coordinate system. Otherwise, you need to do two transformations related with \theta_3 and \theta_1. Please let me know if you have further questions. 

      Yes, let VABS to​​​​ compute safety margins will be much easier. You only need to run VABS each time according a given load sets. You don't have to change anything else. We are in the process to even update that so that uses can provide multiple set of loads on time. 


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      Replying to Wenbin Yu