RBE2 Constraints & CBEAM

Oguzhan Coban
Oguzhan Coban New Altair Community Member
edited October 2020 in Community Q&A

Hello everyone, In my research I have found, that CROD elements support tension and compression only, whereas CBEAMs allow bending as well. Thats why I am thinking to use CBEAM elements to simulate a pullrod but I am not really sure.

My main point is to establish a connection between pullrod-bracket (upper left orange part) and pullrod which is modeled as CBEAM elements, so that the connection is only locked along pullrod (CBEAM elements). Like in picture 3, I used RBE2 and locked dof 1,2,3 (no constraint). Like in picture 2, I used RBE2 (all dofs locked) and additionaly I defined a constraint, that it is only locked DOF 1,2,3. After I run the analysis, I get an error :   ' ** ERROR # 725 *** An invalid rigid element. This RBE2 has rotational rigid body modes in all three directions. '.

Could you give me some suggestions, what is wrong or am I thinking the wrong way? By the way, I also have tried to define a diagonal constraint (along pullrod) directly on the independent point (pic 3) but I failed to assign the local axis system for this case.

 

Thanks in advance,
best regards.

 

 

<?xml version="1.0" encoding="UTF-8"?>1.jpg

<?xml version="1.0" encoding="UTF-8"?>2.jpg

<?xml version="1.0" encoding="UTF-8"?>3.jpg

Tagged:

Answers

  • Merula_20758
    Merula_20758 Altair Community Member
    edited February 2020

    Let me help you with the axis definition:

     

    Thats 1D - systems - assign

    there you have to assign all the nodes which should be expressed in the local coordinate system to that local system.

     

    Then it should be easy to apply the constraint. no rbe2 needed ;)

     

     

Categories