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Reference CID and Analysis CID

ron.kunz
Dear all,
I am trying to understand an example model with a bearing.
The two nodes which are used to constrain the bearing give for the Node Location Information:
Reference CID = Global Rectangular
Analysis CID = 4 Rectangular
 
All other nodes are referring also to Global Rectangular CID for the Analysis CID.
I would like to know what this means 4 Rectangular?
The RBE2s which are connected to these points have no reference to other CID so I assume they take the global CID.
 
In the BDF-file there are some CORD2R defined:
CORD2R* 4                              0.             0.
*       0.            1.              0.            0.
*      0.              0.            -1.
*
CORD2R* 5                              0.             0.
*       0.            -1.             0.            0.
*      0.              0.            1.
*
CORD2R* 6                              0.             0.
*       0.            1.              0.            0.
*      0.              0.            -1.
*
CORD2R* 7                              0.             0.
*       0.            -1.             0.            0.
*      0.              0.            1.
*
CORD2R* 12                            -160.81759643554368.5
*      -226.72961425781-160.81759643554691.1295443819 -556.83722631104
*      -168.57967172422698.56095064975695.8543142001753
 
I don`t see a special CID.
Can you explain the 4 Rectangular?
Thanks
 
 
 
 
Parents
  • 0
    What Patran refers to with the term "Analysis Coordinate System", is translated to Nastran terminaology as "Displacement Coordinate System". Other FE codes may use similar but different terminology.
     
    For Nastran:
    In linear static analysis, each grid point can undergo at most three orthogonal
    translational and three orthogonal rotational components of displacement.
    Each component is called a degree of freedom and adds one unknown to the
    system of simultaneous linear equations representing the structure.
     
    Each grid point refers to two coordinate systems:
    • One system is used to locate the grid point (CP in field 3)
    • The other is used to establish the grid point’s displacement (output) coordinate system (CD infield 7).
    The displacement coordinate system defines the direction of displacements, constraints, and other grid
    point related quantities such as reaction forces. The basic (default) coordinate system is indicated by a zero or blank in the CP and CD fields. CD and CP do not have to be the same coordinate system.
     
    so the analysis system is not so much "one can check with the analysis CID how your nodes are behaving?" it IS the system that the analysis dof (a particular term in the matrix that is being solved) is with reference to.
Reply
  • 0
    What Patran refers to with the term "Analysis Coordinate System", is translated to Nastran terminaology as "Displacement Coordinate System". Other FE codes may use similar but different terminology.
     
    For Nastran:
    In linear static analysis, each grid point can undergo at most three orthogonal
    translational and three orthogonal rotational components of displacement.
    Each component is called a degree of freedom and adds one unknown to the
    system of simultaneous linear equations representing the structure.
     
    Each grid point refers to two coordinate systems:
    • One system is used to locate the grid point (CP in field 3)
    • The other is used to establish the grid point’s displacement (output) coordinate system (CD infield 7).
    The displacement coordinate system defines the direction of displacements, constraints, and other grid
    point related quantities such as reaction forces. The basic (default) coordinate system is indicated by a zero or blank in the CP and CD fields. CD and CP do not have to be the same coordinate system.
     
    so the analysis system is not so much "one can check with the analysis CID how your nodes are behaving?" it IS the system that the analysis dof (a particular term in the matrix that is being solved) is with reference to.
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