Springs with variable stiffness property

Javid Moraveji
Javid Moraveji Altair Community Member
edited April 2023 in Community Q&A

1) Is there an element type/property available that can represent a nonlinear spring with a variable stiffness as a table?   

2) Is there a way to specify the force at the tip of a spring (linear CBush1D or nonlinear as above) to follow the deformation direction of tip Grids when the deflections are large? 

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Best Answer

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited April 2023 Answer ✓
    Javid Moraveji said:

    Thanks Adriano. 

    I played with it and used it.

    I am guessing the answer to my second question is adding FLLWER to my input deck with option 1 for concentrated forces/moments. For the CBUSH example, if I want the force follow the the direction of the spring nodes, do I need to define its direction using a local coordinate system?

     

     

    correct. By defining a follower force (FORCE2, if I'm not wrong) you specify 2 nodes as reference for the force direction. If their position changes during the NL run, the force will follow this new direction accordingly.

Answers

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited April 2023

    hi,

     

    both CBUSH/PBUSH and CBUSH/PBUSH1D have the option of using a NL force x displcaement curve (TABLED1) and assign it to the NL stiffness KN;

    /try this one, attached

  • Javid Moraveji
    Javid Moraveji Altair Community Member
    edited April 2023

    Thanks Adriano. 

    I played with it and used it.

    I am guessing the answer to my second question is adding FLLWER to my input deck with option 1 for concentrated forces/moments. For the CBUSH example, if I want the force follow the the direction of the spring nodes, do I need to define its direction using a local coordinate system?

     

     

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited April 2023 Answer ✓
    Javid Moraveji said:

    Thanks Adriano. 

    I played with it and used it.

    I am guessing the answer to my second question is adding FLLWER to my input deck with option 1 for concentrated forces/moments. For the CBUSH example, if I want the force follow the the direction of the spring nodes, do I need to define its direction using a local coordinate system?

     

     

    correct. By defining a follower force (FORCE2, if I'm not wrong) you specify 2 nodes as reference for the force direction. If their position changes during the NL run, the force will follow this new direction accordingly.

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited April 2023
    Adriano A. Koga_21884 said:

    correct. By defining a follower force (FORCE2, if I'm not wrong) you specify 2 nodes as reference for the force direction. If their position changes during the NL run, the force will follow this new direction accordingly.

    sorry..FORCE1

    https://help.altair.com/hwsolvers/os/topics/solvers/os/force1_bulk_r.htm

     

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