General

Restrictions in bead optimization can either be defined as boundary conditions that limit the node displacement or as a LINK-condition. The latter is only allowed for controller-based bead optimization. A design variable constraint is a restriction that directly affects the individual design variables or the individual design nodes.

Possible restrictions are:

the specification of an allowable displacement area by limiting the signed absolute displacement.
the specification of variation and frozen areas.

It is also possible to influence the allowable displacement direction by limiting the displacement to specific coordinate directions. At last it is possible to link the design variables and thereby force them to be optimized in a symmetric way (only controller).

The definition of the design variable constraints for bead optimization is done using the DVCON_BEAD command.

Important:

Possible restrictions for bead optimization are very similar to the restrictions of shape optimization. The definition of the CHECK parameters is often identical.
Some of the design variable constraints for bead optimization relate not only to the design variable itself but also to the corresponding optimization displacement vectors or the design coordinates. The term ‘design variable constraint’ in this case should be interpreted in a more general way.

Restrictions for bead optimization

The following individual restrictions can be defined for bead optimization:

CHECK_GROW: Restriction of the absolute displacement in shell normal direction (see Restricting the absolute displacement)
CHECK_SHRINK: Restriction of the absolute displacement opposite the shell normal direction (see Restricting the absolute displacement)
CHECK_SOLID: Check the displacements against geometric primitive solids (see Displacement check against solids (CHECK_SOLID))
CHECK_ELGR: Check the displacements against elements of an element group (see Displacement check against elements (CHECK_ELGR))
CHECK_BC, CHECK_DOF: Restriction of the displacement direction (see Restricting the direction of displacement)
CHECK_LINK: Assignment of a coupling condition (only BEAD_CONTROLLER) (see Symmetry conditions (CHECK_LINK))

A DVCON_BEAD command using all of the individual restrictions appears as follows:

DVCON_BEAD
 ID_NAME = name_of_dvcon_bead
 ND_GROUP = name_of_node_group 
 CHECK_SOLID = name_of_solid
 CHECK_ELGR = name_of_element_group
 CHECK_GROW = <max_grow_value>
 CHECK_SHRINK = <max_SHRINK_value>
 CHECK_BC =	cs_name	, FREE/FIX, FREE/FIX, FREE/FIX
 CHECK_DOF = YES/NO
 CHECK_LINK = <	link_name>
END_

Important:

Using CHECK_GROW and CHECK_SHRINK is the easiest way to constrain design nodes for sensitivity-based optimization. See also Restricting the absolute displacement.
CHECK_SHRINK has no effect on controller algorithm while it only "grows".
CHECK_LINK has no effect on sensitivity-based algorithm.
The restrictions are checked only for the corner nodes of the node group (ND_GROUP parameter). If midside nodes are contained in the node group they are subsequently placed in between the neighboring corner nodes. Therefore, it’s not possible for mid-side nodes to guarantee adherence to the restrictions; a small amount of deviation may occur.
It is possible to define several individual CHECK_* restrictions within a DVCON_BEAD command. The order of the execution of the individual restrictions within a DVCON_BEAD command appears as follows: CHECK_GROW, CHECK_SOLID, CHECK_ELGR, CHECK_BC, CHECK_DOF, CHECK_LINK.
The individual restrictions are checked independently of each other, i.e. an individual restriction always overrides the previous restriction.
The activated DVCON_BEAD entries are executed in the order in which they are referenced in the OPTIMIZE command. The individual DVCON_BEAD entries are checked independently of each other, i.e. a DVCON_BEAD entry always overrides the previous DVCON_BEAD entry. If mutually independent restrictions are declared all restrictions are observed. If mutually dependent restrictions are declared the user must select an order of execution that is logical and specific to the problem.
It is possible to define several design variable constraints using the DVCON_BEAD command. Each DVCON_BEAD definition must have its own unique name.
The DVCON_BEAD definitions must be activated by a reference in the OPTIMIZE command. Non-activated definitions have no influence on the optimization. The reference in the OPTIMIZE command assigns the design variable constraints and the design area (see DV_BEAD command) to each other. The recommended procedure is to define the assigned restrictions immediately after defining the design area.