Structure Constraints and Coordinate Systems

The software applies constraints in reference to a coordinate system. When you enter Structure, the current coordinate system is the WCS. You can change the current coordinate system. When you create a constraint, the current coordinate system is the reference coordinate system for the constraint. You can change reference coordinate systems on the Constraint dialog box as part of creating or editing constraints. For more information, see Coordinate Systems.

Within the context of Creo Simulate, you will probably use a Cartesian coordinate system most frequently. Cylindrical and spherical coordinate systems can be useful for symmetrical parts. For example, you could use a cylindrical coordinate system to constrain a slider to a rod (R, T fixed, Z free) without the presence of the rod. Radial enforced displacements simplify the modeling of shrink fits and similar processes.

You should not constrain geometry that touches the Z (phi=0) axis of the associated cylindrical or spherical coordinate system. Instead, you can change the coordinate system to Cartesian or change the orientation of the coordinate system so that it does not touch the geometry you want to constrain.

If you have a 2D plane strain, 2D plane stress, or 2D axisymmetric model, and you want to associate constraints to a UCS, the UCS must meet the following criteria:

• The UCS Z axis must be parallel to the WCS Z axis. (In Creo Parametric, the UCS Z axis must be parallel to the reference UCS Z axis.)

• The UCS origin must lie in the WCS Z=0 plane.

Creo Simulate does not report reaction force data at constrained points and edges when the constraint is associated to a UCS.

In FEM mode, there may be a conflict between your constraint coordinate systems and coordinate systems associated with connections and mesh controls.

Return to Guidelines for Structure Constraints.