I want to model this structure as Assembling and Dismantling Mechanism.

  1. Top ring
  2. Bottom ring
  3. Columns with hinge connection( all three rotation free) along the circumferential direction are attached to the top and bottom ring.

Refer to the image for more detail. A force is applied to the top ring. With that top ring will rotate and move up. Consider a cup of a bottle. As columns are attached to the top ring as a hinge connection they will move as well.


I have some questions

1. Which analysis should I use? Transient analysis

2. I want to model this structure with end release, not with joints or contacts. I try to model this structure as a beam element with end release. End release at the bottom and top of the column with all three rotation free and fixed support at the bottom ring. But I am getting Pivot Error.

Answers

  • peteroznewmanpeteroznewman Posts: 12,827Member
    edited November 25

    @Muhammadkhizer

    Item 3, the columns meshed with beam elements are the cause of the error.

    When you release all rotations at both ends, that makes the column free to spin on its axis, causing a pivot error.

    You must constrain the free rotation of the column about its axis on one end. The other end can have all three rotations free.

  • MuhammadkhizerMuhammadkhizer Posts: 2Member

    @peteroznewman.

    If you review my solution that will be helpful for me.

    I have created this model as a beam element in SpaceClaim.

    Initially, the columns are in rest condition to the ground. Please refer to the image above.

    1. Geometry

    Total 62 beam elements:

    Top ring ( beam element)

    Bottom ring (beam element)

    60 columns ( 60 beam elements )


    2. Connections

    I have provided 120 end releases. For a single column, 2 end releases, one at the top and one at the bottom of the column. ( free rotation in all directions and all translation fixed ).

    2 end release * 60 columns = 120 end release


    3 Mesh( haven't done anything.) I am sure about that how should I mesh this model.

    4 For time being I have provided a force at the edges of the top ring only to lift the top ring.


    Problems:

    1. I want to fix the bottom ring. How should I do that? I tried to fix the bottom edge but it is not working. As the bottom ring is attached to columns and columns have end release that is why I cannot apply for fixed support at the bottom ring edges.


    2. I am getting the solution. But I don't want to lift the top ring with the vertical force which I have provided. I want to apply a rotation at the top ring which rotates the top ring and lifts it. Like a cap of a bottle. Please refer to the image in the first post for the lifting process.

    How can I do that?


    3. The top and bottom of the columns are not connected properly with the top and bottom rings. The side of the column is getting out of the top and bottom rings. How can I solve this problem?

    In the Spaceclaim, first, I created the top and bottom ring as beam elements then I created the points on the top and bottom ring, for the columns I draw a line between points that were on the top and bottom rings.

    I am not sure but I think the problem can be due to the mesh.

    I have attached the Ansys file as well. The file contains the model only, it is without the results.

    Thank you

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