Defining a Rib Design Constraint

You can define a rib design restriction to obtain rib patterns in the optimization result.

This task shows you how to:

Before you begin: The rib design restriction can only be used with the sensitivity-based algorithm.
See Also
About Rib Design
In Other Guides
DVCON_TOPO

Rib Design Definition

  1. Using the graphical user interface choose Command > DVCON_TOPO in Tosca Structure.pre and define the rib restriction with the available fields shown in the following figure:

  2. Or use the DVCON_TOPO command: 

    
DVCON_TOPO
  ID_NAME       = <Name of DVCON object>
  EL_GROUP      = <Element group to be restricted>
  CHECK_TYPE    = RIB_DESIGN
  CHECK_GROUP   = <Element group to be checked for restriction>
  RIB_THICKNESS = <Averaged thickness of ribs>
  RIB_DISTANCE  = <Averaged distance between the ribs>
  RIB_DIRECTION = <X_COMP>, <Y_COMP>, <Z_COMP>
  RIB_CS        = <Name of coordinate system>
  RIB_HEIGHT    = MAX | AUTO | MIN, <minimum height>
  APPROXIMATE   = YES | NO, optional: <scale factor>
END_

  3. A rib restriction is activated by setting the CHECK_TYPE of the design variable constraint to RIB_DESIGN. The restriction definition contains the following parameters:
    1. ELEMENT_GROUP: The group of elements for which the constraint is active. Defining an element group is mandatory.
    2. CHECK_GROUP: The group of elements that are checked if elements are properly supported and do not violate the rib restriction. Most often it is best to use the same group as in ELEMENT_GROUP. All elements are used if this parameter is empty.
    3. RIB_THICKNESS: The averaged thickness of the ribs.
    4. RIB_DISTANCE: The averaged distance between the ribs. The distance must be larger than twice the average element edge length.
    5. RIB_DIRECTION: Out-of-plane growth direction of the ribs.
    6. RIB_CS: Coordinate system for the definition of the rib direction.
    7. RIB_HEIGHT: With MAX, all the design material in the defined RIB_DIRECTION is used for the ribs so they will always have the maximum possible height. Using MIN, a user-defined minimum height is set which leads to a variable height of the ribs. With AUTO, Tosca Structure automatically sets the minimum rib height.
    8. APPROXIMATE: Option to turn on or turn off an approximating, but more performant algorithm. The scale factor defines how coarse the evaluation of the constraint is.
      Important:
      • It is only required to define an additional volume/mass constraint for the design area when its constraint value is below RIB_THICKNESS / 2*RIB_DISTANCE. In addition, the recommendation is to use nonfrozen design elements only in the ELEMENT_GROUP.

Example: Rib Definition

The following figure shows the rib restriction for a given distance (radius of green circle) and given thickness (blue circle). The defined rib direction is out-of-plane of the image. The back and side walls are set to be frozen (grey) and not used in the defined rib restriction.