Defining a Reaction/ Internal Force Constraint

The aim of this optimization is to minimize the internal force of spot-weld elements. Both the relative material volume constraint and a displacement constraint are used.

This task shows you how to:

Define an Internal Force Constraint in Tosca ANSA® environment

  1. To create a constraint, select New > INTERNAL_FORCE_CONSTRAINT on CONSTRAINTS item.

  2. Choose TARGET = NODE_AND_ELEMENT_GROUP, ND_GROUP_DEF = ND_GROUP_DEF, EL_GROUP_DEF = EL_GROUP_DEF.

  3. Press "?" key in ND_GROUP_DEF field and choose the appropriate node group.

  4. Repeat for EL_GROUP_DEF where an element group shall be chosen, see the following figure.

Internally in SIMULIA Tosca Structure, a separate design response for each pair (node, element) is created, where the node belongs to the chosen node group and to the element (that itself belongs to the chosen element group). In the example, 32 nodes are connected to the cweld elements. Since there are two load cases, 64 design responses are produced in SIMULIA Tosca Structure.

Define an Internal Force Constraint in Tosca Structure.gui

  • Define an internal force constraint in Tosca Structure.gui as shown in the following figure:



Define a Reaction Force Constraint in Tosca Extension for ANSYS® Workbench

Before you begin: Internal forces are not available in the Tosca Extension for ANSYS® Workbench and thus the setup is performed using reaction forces.

  1. To define a Reaction Force constraint within a Design Response, add a Design Response first by clicking Optimization > Design Response.

  2. Select Reaction Force/Moment as Category and the desired direction as Response Type;:

  3. Assign a node to the design response.

  4. Call this Design Response in a Constraint.

    Tip: If you change the name of the Design Response by using the F2 button, it might be easier to use the Design Response later.

  5. Therefore add a Constraint to the project first, by clicking Optimization > Constraint.

Result and Convergence

Objective function plot (relative material volume) is presented in the next figure:

Internal force constraint values are pictured in the following figure:

Displacement constraint values are shown in the next figure:

The last figure presents the result of the optimization under force constraints in the spot weld elements:

SIMULIA Tosca Structure Parameter File

  • The commands in the parameter file look like follows:

    DRESP
 ID_NAME        = DRESP_VOLUME
 TYPE           = VOLUME
 DEF_TYPE       = SYSTEM
 GROUP_OPER     = Sum
 EL_GROUP       = ALL_ELEMENTS
END_
OBJ_FUNC
 ID_NAME        = MINIMIZE_VOLUME
 TARGET         = MIN
 DRESP          = DRESP_VOLUME, ,  
END_
GROUP_DEF
 ID_NAME        = CWELD_NODES
 TYPE           = NODE
 FORMAT         = LIST
 LIST_BEGIN
5291, 4055, 5295, 4051, 5299, 4047, 5303, 4043,
5501, 4026, 5505, 4030, 5509, 4034, 5513, 4038,
5186, 4685, 5190, 4681, 5194, 4677, 5198, 4673,
5396, 4656, 5400, 4660, 5404, 4664, 5408, 4668
END_
GROUP_DEF
 ID_NAME        = CWELD_ELEMENTS
 TYPE           = ELEM
 FORMAT         = LIST
 LIST_BEGIN
 100000-100015
END_
DRESP
 ID_NAME        = DRESP_INT_FORCE_ABS
 TYPE           = INTERNAL_FORCE_ABS
 DEF_TYPE       = SYSTEM
 GROUP_OPER     = Max
 EL_GROUP       = CWELD_ELEMENTS
 ND_GROUP       = CWELD_NODES
END_


    CONSTRAINT
 ID_NAME        = CONSTRAINT_INT_FORCE_ABS
 DRESP          = DRESP_INT_FORCE_ABS
 MAGNITUDE      = ABS
 LE_VALUE       = 15
END_
DRESP
 ID_NAME        = DRESP_DISP_LC11
 DEF_TYPE       = SYSTEM
 TYPE           = DISP_ABS
 NODE           = 3900
 LC_SET         = ALL,11,All
 GROUP_OPER     = Max
END_
DRESP
 ID_NAME        = DRESP_DISP_LC12
 DEF_TYPE       = SYSTEM
 TYPE           = DISP_ABS
 NODE           = 4530
 LC_SET         = ALL,12,All
 GROUP_OPER     = Max
END_
CONSTRAINT
 ID_NAME        = MAX_DISP_LC11
 MAGNITUDE      = ABS
 DRESP          = DRESP_DISP_LC11
 LE_VALUE       = 0.003
END_
CONSTRAINT
 ID_NAME        = MAX_DISP_LC12
 MAGNITUDE      = ABS
 DRESP          = DRESP_DISP_LC12
 LE_VALUE       = 0.003
END_


    OPTIMIZE
 ID_NAME        = TOPOLOGY_OPTIMIZATION
 DV             = DESIGN_VARIABLES
 OBJ_FUNC       = MINIMIZE_VOLUME
 CONSTRAINT     = MAX_DISP_LC11
 DVCON          = DVCON_FROZEN
 STRATEGY       = TOPO_SENSITIVITY
 CONSTRAINT     = MAX_DISP_LC12
 CONSTRAINT     = CONSTRAINT_INT_FORCE_ABS
END_
OPT_PARAM
 ID_NAME        = MY_PARAMETERS
 OPTIMIZE       = TOPOLOGY_OPTIMIZATION
 DENSITY_UPDATE = CONSERVATIVE
 STOP_CRITERION_DENSITY = 0.001
END_