Strange behaviour with RBE3 elements in Model

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

Hello,

 

I have a strange problem with the deformation of a pipe elemten under bending and torsion moments. I completely constrain the base of the pipe with RBE2 elements in every DOF and on the other side of the pipe I apply the moments with RBE3 elements.

I would expect the pipe to bend down for the bending moment and to twist around its z-axis for the torison. This is the case, but additionally I get a deformation of the end piece of the pipe.

The analysis results in an oval shape for the bending and an extremely widened end for torsion (please see pictures for reference).

I would not expect this with RBE3 elements. I also checked with RBE2 elements and get almost the same result.

 

What am I doing wrong?

Thanks for your help!

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

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

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2017

    Hi,

    Can you please share the model file so that we can review.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2017

    Thank you for your response. I just send the files to your Secure File DropBox

  • Rahul Rajan_21763
    Rahul Rajan_21763 New Altair Community Member
    edited August 2017

    I see you have applied moment for both the loadcases (Torque & Torsion).That is the reason for not getting bending behaviour in your model.(I got files from George to test & it contains RBE2 on both the ends)

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2017

    Hello Rahul,

     

    thank you very much for your response! Maybe there was a problem with the import, or I accidentally send you the wrong files, but the moments are connected to the geometry using RBE3.

    Nevertheless, I have the same problem no matter if I use RBE2 or RBE3.

     

    Could you go into a bit more detail why I don't get a bending behavior? What can I change to get more realistic results? Is there another way to apply torsion?

     

    I am looking forward to your answers!

    best,

    Chris

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