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Thread: Deformation of hollow sphere

  1. #1
    Join Date
    May 2017

    Default Deformation of hollow sphere

    I am new to the Febio environment (2.6.3 Windows 64). To get warm I am trying to set up a pressurized thin walled elastic hollow sphere (Mooney-Rivlin material) and study the deformation. I have looked at a previous thread (http://mrlforums.sci.utah.edu/forums...=hollow+sphere), but a lot seems to have changed with Febio since 2012 and I can't get this to run.

    When setting up the problem from scratch I get the warning "No force acting on the system" even though I've assigned a nonlinear pressure load to the internal surface. I've tried different maximal pressures, sphere dimensions and material properties without luck. In postview no visible deformation can be seen.

    When trying the file from the old thread I get the "FATAL ERROR: invalid value "linear" for attribute "pressure.type" (line 9649)" and when changing this to nonlinear, wich I believe to be more appropriate, in PreView I get the "No force acting..." warning again. And, besides this warning, it failes to converge.

    I would greatly appreciate if someone could point me in the right direction: What do I do wrong? Enclosed are the febio files I'm trying to get to work (in this particular version the sphere is slightly pinched).

    Attached Files Attached Files

  2. #2
    Join Date
    May 2017


    I'm answering my own post: I never got the PreView-generated .feb file to run correctly in Febio. After manually updating it to febio_spec 2.0 instead of the febio_spec 1.2 created by PreView I got it to run: The most important change was probably changing <pressure> to <surface_load type="pressure"> under <Loads>. After this the "No force acting on the system" vanished and in postview the inflation of the sphere with increasing pressure was evident.

    I'm guessing there is a bug in the current PreView with regards to surface pressure load?

  3. #3
    Join Date
    Nov 2007
    Salt Lake City, UTAH



    The problem actually lies with FEBio. As of FEBio 2.0, the 1.2 file format is deprecated and some features are not fully supported anymore (such as pressure loads). It is highly recommended to use the 2.0 or 2.5 formats (Note that PreView does not read the 2.5 format yet, but will be able to as of its next, upcoming release 1.21). Future versions of PreView may also discontinue support for the 1.2 format.


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

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