Planar joint between rigid bodies

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  • lingminl
    Junior Member
    • Dec 2010
    • 28

    Planar joint between rigid bodies

    Hi,

    I have a question about FEBio's capability of modeling a planar joint between two rigid bodies.

    I'm trying to build a model for a knee simulator machine, and the loading parts of the which are considered 2 rigid bodies. (Simply call one is tibia holder plate, the other is a loading cylinder.) I want to constrain all DOFs of the loading cylinder except the superior-inferior translation, where the load applies. And the tibia holder plate can only be free in superior inferior translation, medial-lateral translation, and varus-valgus rotation, and is pushed by the loading cylinder always.

    To model this, I want to create a "planar joint" (allows both translation and rotation) to connect the 2 rigid bodies. However, I can only find a "rigid joint" in "contact" menu that can connect 2 rigid bodies, and the rigid joint can be only spherical joint for now (if I understand it correctly?).

    My question would be, if FEBio is able to create a joint that connects 2 rigid body both translational and rotational? Or some other alternatives to help me model this knee simulator machine parts?

    Your help is greatly appreciated.
  • lingminl
    Junior Member
    • Dec 2010
    • 28

    #2
    I'm thinking this problem may be solved by a sliding contact not allowing normal motions, like the "sliding only" contact in NIKE3D. If so, the further questions would be:

    Does FEBio have a contact type like that?
    Or can FEBio import the "sliding only" contact from NIKE3D?

    Comment

    • maas
      Lead Code Developer
      • Nov 2007
      • 3400

      #3
      So if I understand correctly, you would like the contacting surfaces to stick together but allow them to slide across each other? That is currently not possible in FEBio, but if you post a feature request I would be more than happy to look into it.

      I'm not sure I understood your explanation of the planar joint. Do you have a drawing or a schematic that illustrates what you want to do?

      Thanks,

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

      Comment

      • lingminl
        Junior Member
        • Dec 2010
        • 28

        #4
        Steve,

        Thanks for your quick reply. You were right about the sliding contact, I will request it.

        The planar joint can be imagined like a desk top with X & Y axis parallel to its surface and Z axis normal to its surface, the block connect to the desk top by a planar joint can slide on it in X or Y direction arbitrarily, and can also spin along the direction of Z axis, but cannot leave the desk at all.

        Attached is a bad drawing of the planar joint and also the knee simulator machine I want to simulate.

        Thanks again,

        Laura,

        Comment

        • maas
          Lead Code Developer
          • Nov 2007
          • 3400

          #5
          Hi Laura,

          Thanks for the drawings. I think I understand now.

          Cheers,

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

          Comment

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