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Moving Coordinate System in Multi-Body Analysis

User: "christian.gomeslves"
Altair Community Member
Updated by christian.gomeslves

Hi everyone,

 

in a multi-Body Analysis, I want to apply a force which is always to stay normal to a surface (i.e. it should maintain its orientation with regard to the applied node). I made a test model to see how I can achieve this (see attached). I would expect that the Body rotates endlessly when the force moves with the Body.

 

Here is what I tried:

  • Define the MBFRC with three nodes of the rigid Body on which it is applied --> not working, the force is only active in the global x-axis direction
  • Use a vector (again, defined with three nodes of the rotating body) as an intermediate --> not working
  • Use a local coordinate System (tried all CORDxR Systems) --> not working

 

The help states that CORD1R 'moves with GRID points defining the system' in a geometric nonlinear analysis. This does not seem to apply to multi-Body Dynamics Analysis (see attached example). The coordinate System stays static in the Simulation. The MBFRC doesn't even respect the x-axis direction of the local coordinate System, as the Body rotates in the other direction.

 

I can't get it to work and any help would be greatly appreciated :)/emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />

 

edit: Sorry, I forgot: I use Optistruct.

Unable to find an attachment - read this blog

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    User: "tinh"
    Altair Community Member
    Updated by tinh

    Hello Cristian

    You have to supply G4 field

    G4 point to the body so the system will rotate with body

    if G4 is blank, the system attached to GROUND

    User: "christian.gomeslves"
    Altair Community Member
    OP
    Updated by christian.gomeslves

    tinh, you are amazing :)/emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />  Thank you!

     

    Now, how do I get this to work with an MBFRCC force? The help file states that MBFRCC also has a G4 field but it is not in the card anymore after changing the load type to MBFRCC :huh:/emoticons/default_huh.png' title=':huh:' />

     

    It's working, however, when manually entering the G4 entry in the .fem-file. I just can't permanently enter it in the card in Hypermesh.

    User: "christian.gomeslves"
    Altair Community Member
    OP
    Updated by christian.gomeslves

    Just FYI, I solved the problem by deleting the force and moving the entire entry to BULK_UNSUPPORTED_CARDS and adding the G4 field. The force is sadly no longer visible in Hypermesh, but the MBFRCC acts properly in the simulation.

    User: "tinh"
    Altair Community Member
    Updated by tinh

    Did you use HM12?

    upgrade version to HM13/14 then you can enter G4 in MBFRCC card

    I can fix HM12 OS template to input the field, but everyone uses it no longer

    User: "christian.gomeslves"
    Altair Community Member
    OP
    Updated by christian.gomeslves

    I am on HM 13.0.