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Thread: Differences between data in PostView

  1. #1
    Join Date
    Nov 2012
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    Default Differences between data in PostView

    Hi all,

    I'm analyzing the results of my simulation and the Effective Stress values that appear on the color bar in PostView are different from the ones that are exported using PostView-Summarize-Save. I attached one image that shows these differences.

    1) Why are these values different?

    2) How can I access the values that appear on the color bar?

    Thanks!

    AndraValues.jpg

  2. #2
    Join Date
    Nov 2007
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    Salt Lake City, UTAH
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    Default

    Hi Andra,

    The range for the color bar is determined by the nodal values. Since stress is exported from FEBio as an element value, PostView calculates the nodal value by taking the average of the surrounding element values. The summary view, on the other hand, displays the stats of the element values. Due to the averaging, the color bar range will also be slightly smaller than the actual element value range. However, in your case, the difference seems to be a factor of two, which seems suspiciously high. Can you please send me that plot file? If it's too big to attach, you may email to steve dot maas at utah dot edu.

    To answer your question, to see the values from the color bar, select the nodes you are interested in and open the TrackView window.

    Cheers,

    Steve
    Department of Bioengineering, University of Utah
    Scientific Computing and Imaging institute, University of Utah

  3. #3
    Join Date
    Nov 2012
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    13

    Default

    Hi Steve!

    Thanks for your answer. I sent you an email with the model.

    Regards,
    Andra

  4. #4
    Join Date
    Jul 2020
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    13

    Default

    Hi Steve,

    I also seem to have this problem. The results that appear in the color bar in PostView have a significant difference from those in the Summary view, as you can see in the screenshot below. Do you have any suggestions ? Thank you in advance!

    Screenshot_4.png

  5. #5
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    Nov 2007
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    Default

    The data range in the color bar is taken from the nodal values. However, if the data field you are looking at is not a nodal field (e.g. stress), then the nodal values are interpolated from the element data. The Summary View, on the other hand, will not do any interpolation and use the actual data (so, an element field will only look at element values). So, in general, the ranges listed in the Summary view will be more accurate.
    Usually, the differences should be relatively small, and when they are not, this might be an indication that the mesh is too coarse and the solution is not converged.
    If you suspect that this does not explain what you are seeing, please send me the model and I'd be happy to take a closer look.

    Cheers,

    Steve
    Department of Bioengineering, University of Utah
    Scientific Computing and Imaging institute, University of Utah

  6. #6
    Join Date
    Jul 2020
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    13

    Default

    Hi Steve,

    It would really help actually if you could take a closer look. The mesh I am using is adequately fine but the data still have a relatively big difference. Is there something that I could try in the Step settings in order to resolve this ?
    What also made an impression on me is that I am using "isotropic elasticity" as the material and the elapsed time was around 8 minutes but when I was using the "fung orthotropic" material (with the exact same settings) the elapsed time was 8 hours. Could this be caused by the difference in the designated materials? Thank you in advance!
    https://we.tl/t-euNVttsOic
    Kostas

  7. #7
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    Nov 2007
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    Default

    Hi Kostas,

    It looks like the link expired. Can you please send me a new link or email me the file directly?

    Thanks,

    Steve
    Department of Bioengineering, University of Utah
    Scientific Computing and Imaging institute, University of Utah

  8. #8
    Join Date
    Jul 2020
    Posts
    13

    Default

    Hey Steve,
    Thanks again for taking the time.
    https://we.tl/t-I6lCBmHKP2

  9. #9
    Join Date
    Nov 2007
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    Salt Lake City, UTAH
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    Default

    Hi Kostas,

    The numbers in this file are different than the figure above, and they do seem to agree, so maybe double-check if you send me the right file. Also, try this:
    - On the Post\View panel, under the "Color Map" options, set Nodal Smoothing to "No". This will evaluate the raw element data, without smoothing. For the file you sent me, the resulting scale bar range and the numbers in the Summary panel nearly agree. Please give that a try and let me know what you find.

    Cheers,

    Steve
    Department of Bioengineering, University of Utah
    Scientific Computing and Imaging institute, University of Utah

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