Defining Symmetry Conditions

Different symmetry conditions can be defined for an optimization in SIMULIA Tosca Structure. They can be used for obtaining symmetrical results using nonsymmetrical meshes, saving the processing time for the FE-calculation. In addition, symmetrical load case can often be reduced in the FE model.

This task shows you how to:

Context:

The following symmetry conditions are available with SIMULIA Tosca Structure:

  • reflection symmetry
  • point symmetry
  • rotational symmetry
  • cyclic translational symmetry (replication of an area with a given distance)
  • link condition (coupling of arbitrary areas of the model)

The following figures show a beam without symmetry (left) and with reflection symmetry (right).

Example of rotational symmetry (left) and cyclic translational symmetry (right) is presented below.

Define the Symmetry Condition in Tosca Structure.gui

  1. Choose Command | LINK_SIZING in Tosca Structure.pre screen.
  2. In the LINK_SIZING dialog, define the type of symmetry, the coordinate system and, if necessary, the rotation angle (in case of rotation symmetry) or the translation distance (in case of cyclic symmetry). The symmetry definition can also be extended to frozen areas by selecting the corresponding checkbox.

    The frozen elements of one area are also considered as frozen for the linked areas, if the Frozen checkbox is checked.

  3. Choose Command | DVCON_SIZING.
  4. In the DVCON_SIZING dialog, apply the defined symmetry condition as Type = Link Sizing.

Parameter File

The resulting command looks like: 

LINK_SIZING
 ID_NAME     = <Name of LINK_SIZING object>
 CS          = <Name of the reference coordinate system>
 TYPE        = <Type of symmetry>, <axis>
 TRANSLATION = <Translation for cyclic symmetry>
 ANGLE       = <Segment angle for rotation symmetry>
END_



DVCON_SIZING
 ID_NAME    = <Name of DVCON_SIZING object>
 EL_GROUP   = <Element group to be restricted>
 CHECK_TYPE = LINK_SIZING
 CHECK_LINK = <Name of LINK_SIZING definition>
END_

More than one symmetry condition can be defined for an element group. Geometrically, different combinations must be feasible.

Important: The FE meshes do not must be symmetric. The restriction can also be applied to unstructured meshes or to tetrahedron meshes. The elements should have nearly the same size because the result is the resolution of the coarsest part of the mesh. It is possible that the linked elements are not determined correctly if the size of the elements differs too much.