3D Design

3D Design

Topics related to Ansys Discovery and Ansys SpaceClaim.

Axisymmetric Model

    • Darren Kavanagh
      Subscriber

      Hi,

      I'm trying to make a model of an intervertebral disc using an axisymmetric model. The model is composed of 12 layers and the initial 11 layers are solid and I have been trying to use the hydrostatic fluid extension to make the last layer a fluid.

      A few issues I am having are:

      • The mesh works by using a symmetry - however when solved for a force, the centre layer (fluid) sinks in on itself. Additionally, the model splits at the boundaries of symmetry and when a moment is applied the boundaires overlap.
      • Is the hydrostatic fluid element the best method for making the central layer an incompressible fluid?
      • Trying to use a cyclic region as part of the symmetry however a static structural system seems to not agree with it.

      Posted a few pictures below. Any help would be greatly appreciated.

       

    • dlooman
      Ansys Employee

      The hydrostatic fluid needs to be completely surrounded by an enclosure.  You don't appear to have that.  Perhaps you could just use a soft elastic material to model the fluid.  It doesn't appear that the interface between the quarter meshes have contact between them (or share geometry faces.)  You could specify cyclic symmetry boundaries on the quarter model and apply a torsional moment to it.  The moment has to be applied to a remote point located on the centerline.  

    • Darren Kavanagh
      Subscriber

      Hi Dave,AdA

      Thanks for the reply. I modelled the fluid centre to be enclosed now to incorporate the HF elements. Also, I applied a cyclic symmetry (low and high) boundaries for the respective faces. 

      Regarding the remote point - could you confirm if I have placed it right as no matter where I have placed it and then apply a torsional moment I get a result as such. 

    • dlooman
      Ansys Employee

      What have you scoped the remote point to.  Hopefully not just an edge at the centerline.  A possible set of boundary conditions are a fixed support on the bottom face and the remote point scoped to the top face.  That would produce a uniform torque through the model.

      • Darren Kavanagh
        Subscriber

        The remote point is set to the top face, it appears to be working as expected. However, in the solution the model appears as a quarter model; is there a way I can view it as a full axisymmetric solution?

    • dlooman
      Ansys Employee

      Yes.  In the tree highlight Solution (B5).  In the Details for Solution (B5) you will see Cyclic Solution Display.  There you can specify the number of sectors to display.  In your case 4 sectors would be a full display.

      • Darren Kavanagh
        Subscriber

        Hi Dave, Appreciate the help! I have been able to apply a moment around the Z - axis, but I am trying to now simulate lateral bending and flexion, so applying a moment around the Y and X axis. When I try to do this around the remote point formerly created it does not allow me to insert values in for the x or y component, only the z component.

    • dlooman
      Ansys Employee

      Yes, that's a limitation of the Mechanical gui.  The torsional moment is a special case that produces the same result in all 4 quadrants.  A moment about X or Y does not and requires a special treatment.

    • Darren Kavanagh
      Subscriber

      I understand, is there any way I can produce a moment in X or Y with the current four quadrant model?

    • dlooman
      Ansys Employee

      I don't see how.  If you made a half model you wouldn't need cyclic symmetry.  You could just apply half the moment to the half model

Viewing 7 reply threads
  • The topic ‘Axisymmetric Model’ is closed to new replies.