pressure loading in hollow sphere

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  • sumiray
    Junior Member
    • Aug 2012
    • 23

    pressure loading in hollow sphere

    hey,

    i have a hollow sphere of Mooney Rivlin material that i want to apply pressure loading in the inner surface of the sphere. so it's like the pressure source is inside and exerting its force radially out onto the inner surface of the sphere. i tried searching trough the forum but can't really find out how we can apply pressure loading on the inner surface.
  • maas
    Lead Code Developer
    • Nov 2007
    • 3400

    #2
    One way to do this is to select the outer surfaces first and then invert the selection (Edit/Invert Selection). This gives you the inner surfaces. You can then apply a pressure load to this selection to load the inner surface. Let me know if that works.

    Cheers,

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

    Comment

    • sumiray
      Junior Member
      • Aug 2012
      • 23

      #3
      hi steve,

      yupp it worked! [: So i applied the pressure load onto the inner surface of the sphere and edited the curve to mimic the pressure elevation from 0 mmHg to 30 mmHg; (0,0) to (30,30) via the load curve. But when i ran the file through postview, the deformation of the sphere seems to be concentrated on the right side of the sphere in frontal view. Shouldn't the deformation be uniform since i did apply the same pressure load on all the inner surfaces?

      I've uploaded the files for reference. So sorry for the hassle.
      And thanks for the help!
      Attached Files

      Comment

      • maas
        Lead Code Developer
        • Nov 2007
        • 3400

        #4
        That is not what I am seeing. I see a uniform deformation in the plot file you sent me (see attached image which shows a plane-cut through the sphere). Are you sure you are looking at total deformation and not e.g. x-deformation?

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

        Comment

        • sumiray
          Junior Member
          • Aug 2012
          • 23

          #5
          i checked again, and i wasn't looking at the total deformation.
          thanks for being such a help!
          [:

          Comment

          • pbarnouin
            Junior Member
            • Feb 2019
            • 1

            #6
            Pressure Loading from inside a hollow sphere

            Hi !
            I am working on a similar problem (hollow sphere with pressure loading from the inside), but I cannot get into run on FEBio.
            I get the following error (cf. screen shot).
            I've attached a copy of my file. Could anybody tell me what I am doing wrong?

            Screen Shot 2019-02-07 at 10.39.44 AM.png
            embryo_test5.prv.zip

            Thank you!
            Provence
            ---------------
            Department of Mechanical Engineering, Columbia University

            Comment

            • ateshian
              Developer
              • Dec 2007
              • 1824

              #7
              Hi Provence,

              This error message means that you are not allowed to use Poisson's ratio = 0.5, you need to use a smaller value (e.g., 0.49). If you are interested in modeling an incompressible material behavior, I recommend that you look into the uncoupled material models (e.g., Mooney-Rivlin). In those models you can simulate nearly incompressible behavior by selecting a bulk modulus which is about ~1000 times higher than other moduli in that material (such as c1 and c2 in Mooney-Rivlin).

              Best,

              Gerard

              Comment

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