Constraint Equations with named surfaces

PaulFlynn

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

Victor

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.

PaulFlynn

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