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Thread: Volume of a Cavity

  1. #1
    Join Date
    Apr 2016
    Posts
    14

    Default Volume of a Cavity

    Hi Forum Members

    I need to find the volume of a cavity (an empty space within a hollow cylinder) in each time step, to plot Pressure-Volume curve. Is it possible in Febio/Postview? Any suggestions?
    I had the same issue with Abaqus. I solved it by defining a cavity as a new part. Then I found the volume of that part in each step.

    Thank You
    Sanaz
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  2. #2
    Join Date
    Nov 2007
    Location
    Salt Lake City, UTAH
    Posts
    1,683

    Default

    Hi Sanaz,

    Unfortunately, I can't think of a way to do this with any of the current features in FEBio or PostView. However, if this something you really need, I'd be happy to take a closer look and add a new feature. Would you please be willing to make a feature request in the appropriate forum Project PostView so that I stays on my radar? Let us know if you would prefer the feature in FEBio or PostView (or both?). If you need this quickly, then PostView is probably the way to go.

    Thanks,

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

  3. #3
    Join Date
    Apr 2016
    Posts
    14

    Default

    Hi Steve

    I made a feature request in PostView.

    Thanks,
    Sanaz

  4. #4
    Join Date
    May 2017
    Posts
    6

    Default

    I'm interested in the same functionality. I've tried to calculate the inner volume by two metods in PostView but get conflicting results:

    1. PostView/Tools/Measure Volume by selecting the inner surface (faces). This must, however, be done for each time step and it seems to be impossible to generate a plot directly.
    2. Selecting the inner surface (faces) and intergrating over total displacement to see the change in volume

    I've been trying these alternatives in i hollow sphere of Mooney-Rivlin material inflated by an increasing internal surface pressure.

    By method 1. I get a volume of 520 ml at P=0 and 820 ml at P=max. This equals a difference of 300 ml. This must be correct since the radius increases from 50 mm to 58 mm.
    By method 2. I get a volume difference of 400 ml.

    Metod 2 is preferable since it is possible to get a plot of volume with time in PostView. I do not understand why the integration of total face displacement overestimates the volume change. Any ideas?

    A direct way to plot inner volume vs pressure would be even better if it could be implemented. Perhaps through a custom x-y plot, where other parameters than time could be chosen as x?

    Regards

    Jonas

  5. #5
    Join Date
    Dec 2007
    Posts
    652

    Default

    Hi Jonas,

    I implemented a plot variable in FEBio called "enclosed volume", which can be used with a named surface. It evaluates the volume enclosed by a surface at each time point and associates it with any/all of the faces of that surface.

    The named surface is declared in the <Geometry> section, using <Surface name="unique_name">. The plot variable is declared in the <plotfile> section as <var type="enclosed volume" surface="unique_name"/>. This way you can create scatter plots in PostView that use this variable along either of the plot axes. Multiple declarations of this variable may be used to evaluate multiple enclosed volumes.

    This feature will become available in the next release.

    Best,

    Gerard

  6. #6
    Join Date
    May 2017
    Posts
    6

    Default

    Excellent. Looking forward to the next release then. In the current release you can not access named selections as defined in preview, right? They do not seem to show up under Model/Mesh in PostView.

    Regards,

    Jonas

  7. #7
    Join Date
    Dec 2007
    Posts
    652

    Default

    Hi Jonas,

    That's correct. The latest version of PreView will automatically save named selections and provide the option to plot "enclosed volume" for each named surface in the model.

    Best,

    Gerard

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