The same connection modeled in two ways gives different results

Rafał Szypulski_22596
Rafał Szypulski_22596 Altair Community Member
edited August 2022 in Community Q&A

Hello!

I'm looking for help with understanding why the (seemingly same) 1D-2D connection modeled in two different ways gives dramatically different results (30% difference). I have a plate modeled with shell elements and a beam. Two variants of connection are described on the picture below. I'd be grateful for your assistance. Why are the results different?

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Best Answer

  • PaulAltair
    PaulAltair
    Altair Employee
    edited August 2022 Answer ✓

    In Case V1, you are coupling DOF6 at the CBEAM to an RBE2 that only has Translational DOFS coupled back to the hole. In this case I think the rotation of the beam in the hole remains unconstrained in effect since the RBE2 cannot carry that moment.

    In Case V2, you have directly coupled DOF6 of the Beam from independent of the RBE2 from one end to the other so I think moment between Beam and Hole will be carried.

    If you add DOF6 to the RBE2 in Case V1 does it give same/similar then to V2?

Answers

  • PaulAltair
    PaulAltair
    Altair Employee
    edited August 2022 Answer ✓

    In Case V1, you are coupling DOF6 at the CBEAM to an RBE2 that only has Translational DOFS coupled back to the hole. In this case I think the rotation of the beam in the hole remains unconstrained in effect since the RBE2 cannot carry that moment.

    In Case V2, you have directly coupled DOF6 of the Beam from independent of the RBE2 from one end to the other so I think moment between Beam and Hole will be carried.

    If you add DOF6 to the RBE2 in Case V1 does it give same/similar then to V2?

  • Rafał Szypulski_22596
    Rafał Szypulski_22596 Altair Community Member
    edited August 2022
    Paul Sharp_21301 said:

    In Case V1, you are coupling DOF6 at the CBEAM to an RBE2 that only has Translational DOFS coupled back to the hole. In this case I think the rotation of the beam in the hole remains unconstrained in effect since the RBE2 cannot carry that moment.

    In Case V2, you have directly coupled DOF6 of the Beam from independent of the RBE2 from one end to the other so I think moment between Beam and Hole will be carried.

    If you add DOF6 to the RBE2 in Case V1 does it give same/similar then to V2?

    Of course... The outcome is the same. Thank you, yet once again! :)

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