How to create a spring acting in two directions

kotaro kanetsuki
kotaro kanetsuki Altair Community Member
edited February 1 in Community Q&A

Hello everyone.

I have a question about modeling in HyperMesh.
When I create a spring between two nodes, I want it to act in two directions.
In my traditional modeling, I created each of the two springs and assigned a separate PELAS property to each.

For working convenience, I would like to represent this with only one property.
I thought this functionality was in PBUSH, does it mean the same thing depending on the configuration?

Also, when I use BUSH for overlapping nodes, I often see the following error
　CBUSH 0000 has zero length. (Note: not a shared node)

How can I create this?

 

Thanks for reading.

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Answers

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited January 31

    PBUSH is the right way, as you can specify stiffness in each direction separately.

    Zero length CBUSH needs a system assigned to it, so that the PBUSH "knows" what are the DOF directions that you have. In a non-zero length, the X axis is usually from node1 to node2.

    When the 2 nodes are coincident, it cannot tell what is the orientation, unless you assign a local system to it as CID (coordinate system).

    Edit the element, and assign some local system to the CID field. If you want global, leave it 'unspecified'.

  • kotaro kanetsuki
    kotaro kanetsuki Altair Community Member
    edited February 1
    Adriano A. Koga_21884 said:

    PBUSH is the right way, as you can specify stiffness in each direction separately.

    Zero length CBUSH needs a system assigned to it, so that the PBUSH "knows" what are the DOF directions that you have. In a non-zero length, the X axis is usually from node1 to node2.

    When the 2 nodes are coincident, it cannot tell what is the orientation, unless you assign a local system to it as CID (coordinate system).

    Edit the element, and assign some local system to the CID field. If you want global, leave it 'unspecified'.

    Thanks for the answer, Adriano.
    My question has been answered.
    By the way, how do you do the GUI operation when assigning rigidity to PBUSH?
    Do I just check the "K_LINE" checkbox and enter values for K1 through K6?

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited February 1
    kotaro kanetsuki said:

    Thanks for the answer, Adriano.
    My question has been answered.
    By the way, how do you do the GUI operation when assigning rigidity to PBUSH?
    Do I just check the "K_LINE" checkbox and enter values for K1 through K6?

    correct. The K_LINE options define the spring stiffness in each DOF, related to the local coordinate system of the bush element.

    You also have an option for setting RIGID stiffness to set specific DOFs as reallly high stiffness.

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