Warning Rigid Body _ is not being used

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  • rooks.t
    Junior Member
    • Mar 2010
    • 7

    Warning Rigid Body _ is not being used

    Hello,

    I'm attempting to use several different rigid bodies to model different insertion and origin sites on a cylinder (modeling an extreme simplification of the tibia). I have six different rigid bodies defined with generic Z forces applied right now. Eventually, I plan to use different forces to define a line of action for the forces on that rigid body. My problem right now is that when I run the simulation in FEBio, it says rigid bodies 2, 3, 4, 5, and 6 are not being used (leaving only one of the rigid bodies applying a force). I can't seem to find any differences between how I set up the rigid bodies that would cause some not to be used. Any suggestions would be very helpful.

    Thanks,
    Tyler
  • maas
    Lead Code Developer
    • Nov 2007
    • 3400

    #2
    Hey Tyler,

    It seems that all your rigid interfaces are the same, in that they are all applied to the same nodes. FEBio does not allow nodes to be attached to more than one rigid body. If FEBio detects nodes that have been assigned to more than one rigid body, it merges the rigid bodies, making one of the rigid bodies unused. Hence the warning message.

    Cheers,

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

    Comment

    • rooks.t
      Junior Member
      • Mar 2010
      • 7

      #3
      Steve,

      That makes sense why it would be condensing down to one rigid body. Following from that information, can you tell what I did to make all of the rigid bodies attach to the same nodes? I tried to make rigid interfaces with different groups (using the face selector under the mesh tab in PreView to select specific areas). Is there another way to select different regions for the groups?


      Thanks for the help,
      Tyler

      Comment

      • maas
        Lead Code Developer
        • Nov 2007
        • 3400

        #4
        Yes, you did make different name groups, but they all seems to reference the same nodes. If that is not what you had intended, can you upload your prv file too?

        Thanks,

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

        Comment

        • rooks.t
          Junior Member
          • Mar 2010
          • 7

          #5
          That isn't what I was trying to do, I'm trying to select regions on the surface that a muscle would attach to ideally. The first attached file is the .prv file that goes with the .feb file I uploaded first.

          The second attachment is the .prv file for the same problem, this time selecting only surface nodes (it accepted all the rigid bodies). I'm curious if there is a preferred way of using rigid bodies to apply loads? The only difference in between the models is that on the first one I used the face selector, and on the second one I used the node selector.

          Comment

          • maas
            Lead Code Developer
            • Nov 2007
            • 3400

            #6
            It seems there might be a bug in exporting rigid nodesets defined from surfaces. I'll take a closer look to see what's going on. If it is a bug, it might be a few weeks before I can fix it since I'm making some major changes to preview. In any case, the version with the nodesets seems to work, so I suggest using that for now.

            Cheers,

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

            Comment

            • rooks.t
              Junior Member
              • Mar 2010
              • 7

              #7
              Awesome. Thanks a lot for all the help today!

              Tyler

              Comment

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