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  • K joint Ansys

    erbometro

    Member

    Updated: Oct 23, 2024
    Views: 1.1K
    Hey
    I am trying to use Ansys to model a K joint of tubular section.
    So my problem is, I want to check the strenght of K joint with tubular section by FEM analysis ( Ansys). So the point is how to create the model and how to mesh it.
    I already know what is the strenght of joint by using some formulas given by CIDECT. When I want to model an example given in this book for a correct K joint.
    I always found an equivalent stress higher than the yield stress of the material. That means that the joint is not well designed, whereas this joint is correct for CIDECT.
    When I decrease the size of element, the stress is decreasing that seems really normal, But when I refine the mesh around the connection part of the joint. The stress at this part increases.
    Any idea what is my mistake to model this K Joint?
    Really appreciate if someone can give me a hand.
    Charles
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Replies

  • Capt Spark

    Member • Jul 5, 2011

    that may not be a mistake. It is not possible to comment without seeing any result plots, but there are usually stress concentrations at joints if you model it in detail
    If you make the model finer, then sometimes it captures the effect of the concentration better which results in higher stress.
    Can you post a few stress / mesh pics?
    It is a good idea to cross check nodal solution (PLNSOL) and elemental solution (PLESOL) in ansys to find whether the results have converged. They shouldnt be much different
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  • erbometro

    Member • Jul 7, 2011

    Sorry for delay,
    I use Ansys workbench, I am not very familiar with apdl command. I tried to insert some command in Ansys mechanical but I got no chart in trade. So I don't really know. I use converge function to see convergence. But I guess this one make vary number of element and get result of the stress. So that doesn't really help me to check if i am at th right solution.
    Moreover the stress seems to be right located but always too big compared to standart.
    I can send you some picture as you want.
    Charles
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  • Aashish Joshi

    Member • Jul 8, 2011

    It would be great if you could post a pic of the section over here, both the solid model and the FE model.
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  • Capt Spark

    Member • Jul 8, 2011

    what I wanted to mean was that if you have a coarse mesh, it cannot be always presenting the correct geometry. usually it misses the correct radius and models something greater than it, resulting less stress intensity factor (refer the attached figure).
    But if you continue refining the mesh, at some point the stress should not change for any more refinement.
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  • Aashish Joshi

    Member • Jul 8, 2011

    Refining the mesh is one option. Depending upon the geometry, you can also go in for a higher order element!

    Which element type are you using anyway?
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  • erbometro

    Member • Jul 10, 2011

    As I a m using ansys workbench, I used Solid186 but I tried to model with shell181 by creating surface from solid. I got similar results.
    I attached some pictures. But in this case, more I increase the mesh, more stress decreased always over the yiel strenght of used steel.
    Fine mesh:

    Coarse mesh:
    [​IMG]
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  • erbometro

    Member • Jul 10, 2011

    In fact still can manage to post some picture, internet is really lagging and that doesn't work. But I can send by mail if you are interrested.
    send me email at #-Link-Snipped-#, I will send you picture of K Joint
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