Cantilever beam - reaction moments

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hello,

 

I am working on the cantilever beam well known study, and have done an own beam model. I use the cantilever beam tutorial to help me out. I wonder why the reaction moments of the /ANIM/VECT/MREAC is zero all along the simulation (implicit computation) (example of cantilever beam and own study), when the theory shows it is not (example of cantilever beam and own study).

Theory says : Mreac(Pconstrained) = P*L. (P load, L beam length). However both example simulation and my own simulation show zero.

 

Would anyone know how so and how to plot reaction moments ? 

 

Thanks in advance,

Alice

<?xml version="1.0" encoding="UTF-8"?>theory.png

<?xml version="1.0" encoding="UTF-8"?>mreacZ.png

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited November 2020

    Hi Alice,

    For /ANIM/VECT/MREAC card, the solver will provide reaction moments.

    Please find a simple model file created for cantilever.

    Unable to find an attachment - read this blog

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited January 2017

    Hi George,

    Thank you for your quick reply. I can see it works for your example but I still don't understand why, and why it does not work for mine nore for the 'cantilever_beam' example of the radioss demos ? 

     

    I ask for :
    /ANIM/ELEM/VONM
    /ANIM/VECT/FREAC
    /ANIM/VECT/MREAC

     

    but MREAC does always show zero, including with the demo file if I add /ANIM/VECT/MREAC.

     

    Regards,
    Alice

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited January 2017

    Hi Alice,

    Please share the files so that we can have a look into your model.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited November 2020

    Hi George, 

     

    here the files : beam_test correspond to my model, POUTRE10 is the DEMOS file number 37 ('Analytical Beam')

     

    thanks

    Unable to find an attachment - read this blog

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited November 2020

    Hi Alice,

    Reaction moments cannot be captured for solid elements. 

    Please create a beam section (solid rectangle) using HyperBeam and do the same analysis and you can extract the reaction moments.

     

     

    <?xml version="1.0" encoding="UTF-8"?>mreac.PNG

    Unable to find an attachment - read this blog

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited January 2017

    Hi George,

     

    Okay I didn't know this. I will do so. 

    Can you explain me why it is not possible to extract for solid elements ? 

     

    Thanks a lot,

    Alice

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited January 2017

    Hi Alice,

    Solid elements have no rotational stiffness.  Since there are no rotational degrees of freedom for solid elements the moments are not traced.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited January 2017

    Oh ok ... Thank you for this explanation

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