Cone speaker dynamic simulation

Happy New Year!

Just to share a model for simulating a cone speaker. The speaker is just a hypothetical one.

Let me know if you see any errors.
liml
liml
cone shell model 2 - dynamic Damping.liml
1M

Comments

  • Two problems:

    1) The elements at the center are collapsed quadrilaterals that are shaped like triangles, and all their center nodes are disconnected. To correct it, drag to select all 80 center nodes located at (0,0,13 mm) then use Mesh tools -> Merge nearby nodes to merge them to one. Then use Mesh tools -> Correct collapsed elements to change quad8 to tri6.

    2) The elements on the dome part are flat in the radial/axial directions, so the dome is faceted rather than a smooth curve. If the shape should be a sphere, correct it using Mesh tools -> Fit to curved surface. I haven't changed this because I'm not sure what the correct shape is.

    and two suggestions that aren't really problems:

    3) Since it's axially symmetric, you can improve the performance a lot by modeling only one segment and using frictionless support to enforce the symmetry boundary conditions.

    4)There's no need for the flat rings of elements around the outer edges that have fixed supports on them. You can put the fixed support directly on the edges.

    liml
    liml
    cone shell model 2 - dynamic Damping one segment.liml
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  • Dear Victor,

    Happy New Year! Thanks for your new year gift pointing the issues and giving suggestions.

    Should I scale materials' mass accordingly of the one-segment model for modal analysis? I got very strange result without doing so.

    Cheers.
    Suktan
  • edited January 2
    No, you shouldn't scale the density because the mass will be reduced in proportion to the volume. But you do need to scale the force down since you're only modelling a small part of the structure along with its small part of the force.

  • Without scaling the mass, mode 1 of modal analysis doesn't seem right.

    Did I make anything wrong?
    liml
    liml
    cone shell model 2 - dynamic Damping one segment Modal.liml
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  • It looks reasonable for the rubber surround to have the lowest frequency mode because it has a high mass and low stiffness compared to the other parts. Or is it the shape of the deformation that's the problem?

    Beware that modal vibration won't find any of the non-axisymmetric modes. It was OK for dynamic response because none of those modes would be activated.
  • edited January 3
    Hi Victor,

    Full 3D model's first mode is at 65.52 Hz. On the other hand, first mode of the one-segment mode is 279 Hz. Any idea?

    Thanks.
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  • I see. Mode 1 is missing in the 1-segment model and both have the 279 Hz mode. This does look like a problem and it seems to be something to do with the frictionless support on the tri6 element at the center. I'll look into it further to see if it's a bug - thanks for bringing it up.

    I worked around it by removing the boundary condition from one edge of that element. That introduces a small error and the frequency is off by about 2%.
    liml
    liml
    cone shell model 2 - dynamic Damping one segment Modal removed BC.liml
    43K
  • Thank you Victor.
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