Constraint Equations with named surfaces

PaulFlynnPaulFlynn
I understand how to make constraint equations with individual nodes, but to CE a surface with 100s of nodes is extremely tedious.  Is there a way to use named surfaces or selected node sets to move together as a plane, like in a mirror symmetry in a 3D model.
The manual and tutorials are very brief on CE's.
Paul

Comments

  • VictorVictor
    Not easily. You could generate the relevant parts of the liml file with a script or spreadsheet. 

    The equation:

    3 = 1(1/m)×ux1 + 2(1/m)×uy2

    is stored as:

      <constraintequation constant="3">
        <term coefficient="1 1/m" nid="1" dof="ux" />
        <term coefficient="2 1/m" nid="2" dof="uy" />
      </constraintequation>


    However, perhaps there's another way to achieve what you want:
    • For mirror symmetry of a flat surface about a fixed plane, you can use frictionless support.
    • For an irregular surface on a fixed plane, use a displacement constraint in the direction of the plane normal.
    • To constrain a surface to a plane which is allowed to move and rotate, if you're using the CCX solver, you can use the *MPC keyword.
    • For periodic symmetry, I don't know how.
    • For cyclic symmetry, you can use the cyclic symmetry constraint with the internal solver or enter the cards manually for CCX.

  • PaulFlynnPaulFlynn
    Victor

    This works:

    *Equation
    2
    3,2,1,4,2,-1
    *Equation
    2
    4,2,1,5,2,-1

    *MPC
    Plane
    Top_Nodes

    Nodes 3,4,5 are in the node set Top_Nodes

    Thanks, Paul
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