Biphasic error

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  • ASori
    Junior Member
    • Jul 2015
    • 6

    Biphasic error

    I am running a tibia model with a biphasic callus and cancellous bone. No matter what I do a structural and biphasic test will not complete. Attached are the files - I am not sure why the structural test would not run. If I make the callus a non-biphasic material it runs a structural analysis, but it needs to be biphasic and run the biphasic analysis.

    I try to attach the .feb file but whenever I try to upload it it does not appear.

    EDIT: Even when compressed the file is too large, so here is a google drive link: https://drive.google.com/file/d/1eHv...ew?usp=sharing
    Last edited by ASori; 05-10-2018, 08:35 PM.
  • maas
    Lead Code Developer
    • Nov 2007
    • 3400

    #2
    Hi,

    There are size limits set for all attachments. For .feb I think it's 1 or 2 Megs. If your file is bigger, you can try zipping it or you can upload it to Google drive or some other file sharing service.

    Regarding the problem you are having, if you haven't already, check out the Troubleshooting chapter in the FEBio User's manual, especially section 8.5. Hope it helps.

    Cheers,

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

    Comment

    • ASori
      Junior Member
      • Jul 2015
      • 6

      #3
      I still could not get the file top run. I edited the original post with a google drive link to the .feb file.

      Comment

      • maas
        Lead Code Developer
        • Nov 2007
        • 3400

        #4
        Hi Asori,

        I took a look at the model, but unfortunately it's too big for me to debug. If you have not already done so, I would highly recommend creating a coarser test model that allows you to test your modeling approach in an easier setting. Perhaps even starting with a tet4 instead of tet10 might already make it easier to debug. Sorry I can't be more helpful.

        Best,

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

        Comment

        • ASori
          Junior Member
          • Jul 2015
          • 6

          #5
          Originally posted by maas View Post
          Hi Asori,

          I took a look at the model, but unfortunately it's too big for me to debug. If you have not already done so, I would highly recommend creating a coarser test model that allows you to test your modeling approach in an easier setting. Perhaps even starting with a tet4 instead of tet10 might already make it easier to debug. Sorry I can't be more helpful.

          Best,

          Steve
          Unfortunately I don't have the ability to remesh it. It never gets past the initial convergence. If I use the same model for structural analysis, it works. Also, if I use the same model but use an isotropic elastic material instead of a biphasic material for the callus it works during the biphasic analysis. Maybe I am using the wrong types of contacts between the callus and bone? Or the wrong penalty factors?

          Comment

          • maas
            Lead Code Developer
            • Nov 2007
            • 3400

            #6
            You can convert the tet10 elements to tet4 in PreView. With the mesh selected, activate the Mesh panel and find the Convert button on the Edit Mesh pane. There you will find the option to convert tet10 to tet4. I suspect that this will already greatly reduce the size of the model and allow you to play with the parameters. Alternatively, perhaps you can recreate the model using simpler geometry (e.g. a cylinder for the tibia, a half-tube for the knee implant. You could use PreView built-in primitives for this.) In the end, I agree it's probably fine-tuning the contact parameters, but it's really hard to do this in a model of this size. I hope this helps.

            Cheers,

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

            Comment

            • ateshian
              Developer
              • Dec 2007
              • 1824

              #7
              Hi Andrew,

              I took a quick look at your model and it seems that you did not place a contact interface between the femoral component and the tibial plateau. You need to constrain that interaction.

              Best,

              Gerard

              Comment

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