OPT_PARAM

DV_UPDATE_STRATEGY

= CONVEX_SEPARABLE_APPROX (or CSA)

= MMA

Update strategy for design variables used in sensitivity-based optimization.

CSA: Algorithm based on convex separable approximations

MMA: Method of moving Asymptotes

MODETRACKING

Switch for mode tracking.

= OFF

Mode tracking is deactivated.

= ON

Mode tracking is activated.

= ON, <node_group>

Mode tracking is activated for specified nodegroup.

MODENUMBERS

= <number_of_modes>

= 5

Number of modes included in the mode tracking.

MODETRACK_REFERENCE

= INITIAL

Modes of present optimization iteration are tracked with respect to the modes of the initial optimization iteration.

= PREVIOUS

Modes of present optimization iteration are tracked with respect to the modes of previous optimization iteration.

DAMP_STRUCTURAL_MASS

= <real_value>

Structural mass damping for design element (or elements at design nodes).

DAMP_STRUCTURAL_STIFF

= <real_value>

Structural stiffness damping for design element (or elements at design nodes).

DAMP_VISCOUS_MASS

= <real_value>

Viscous mass damping for design element (or elements at design nodes).

DAMP_VISCOUS_STIFF

= <real_value>

Viscous stiffness damping for design element (or elements at design nodes).

SUM_Q_FACTOR

= <real_value>

= 6.0

Weighting function for peaks in frequency spectrum.

SCALE

= <real_value>

= <grow_scale>, <shrink_scale>

= 1

The displacements determined by the optimization algorithms are multiplied with the <real_value>. To switch the optimization direction of the controller a negative value can be entered (this is available only in the module Tosca Structure.nonlinear.). If two values are defined, the first value is the scale for nodes with growth and the second value the scale for nodes with shrinkage. Both scale values must have the same sign.

MID_NODES

Treatment of the midside nodes during the optimization.

= LINEAR

Midside node positions are linearly interpolated from the optimized position of the connected corner nodes.

= INTERPOLATE

Midside node-based optimization displacements are interpolated from the optimization displacement of the corner nodes.

CURV_SMOOTH

= <elem_edge_length>

= 5.0

The node-based optimization movement vector is modified in areas of high curvature to prevent a collapse of the mesh for large volume changes. A bigger radius causes a bigger curvature-based modification of the optimization movement vector. (0.0 = OFF).

FILTER

= <radius>, <sigma>, <exponent>

= <radius>, 0.2, 1.0

Filter for the nodal equivalence stress. The radius defines the maximum distance for influencing neighbor nodes, sigma defines the reduction of the radius depending on the surface bending, the exponent defines the weighting function depending on the distance.

VECTOR

= EVER

= FIRST

Update of the shape normal vectors occurs in every (EVER) or only in the first (FIRST) design cycle.

DISP

= MINIMUM

= AVERAGE

The permitted absolute step size is controlled by the medium node displacement (AVERAGE) or the minimum node displacement (MINIMUM).

TOL_VALUE

= <real_value>

= 0.001

Tolerance value for the constraint (relative value).

FILTER_RADIUS

= <positive_real_value>,[ABS|REL]

Filter radius. It is used to filter the objective function sensitivities and half of the value is used as radius for filtering the constraint sensitivities and the design variables.

The second parameter ABS or REL indicates if the radius is given in ABSolute units (default) or RELative; in terms of medium edge length

The default value is 4 * medium_edge_length

Use 0 or a negative value to disable the filters (not recommended).

Using the FILTER_RADIUS=<value> parameter is equivalent to using the three parameters

FILTER_SEN    = <value>
FILTER_CONSEN = 0.5*<value>
FILTER_DV     = 0.5*<value>

FILTER_SEN

= <positive_real_value>,[ABS|REL]

Filter radius for filtering the objective function sensitivities.

The second parameter ABS or REL indicates if the radius is given in ABSolute units (default) or RELative; in terms of medium edge length

The default value is 4 * medium_edge_length

This parameter is not available in Tosca Structure.gui.

FILTER_CONSEN

= <positive_real_value>,[ABS|REL]

Filter radius for filtering the sensitivities of the constraints.

The second parameter ABS or REL indicates if the radius is given in ABSolute units (default) or RELative; in terms of medium edge length

The default value is 2 * medium_edge_length

This parameter is not available in Tosca Structure.gui.

FILTER_DV

= <positive_real_value>,[ABS|REL]

Filter radius for filtering the design variables.

The second parameter ABS or REL indicates if the radius is given in ABSolute units (default) or RELative; in terms of medium edge length

The default value is 2 * medium_edge_length

This parameter is not available in Tosca Structure.gui.

VECTOR

= EVER

= FIRST

Update of the shape normal vectors occurs in every (EVER) or only in the first (FIRST) design cycle.

USE_SOLVER_ELEMS

= YES | NO

If Yes: Use solver element formulations instead own formulations. This will increase the number of FE solver calls.

NODAL_MOVE

= <real_value>

= 0.1

Relative move limit of node-based optimization displacement per iteration. Value is between 0 and 1.

NODAL_UPDATE

= CONSERVATIVE

= NORMAL

= AGGRESSIVE

Parameter to determine how the nodal displacements are updated in the optimization algorithm.

STOP_CRITERION_CONVERGENCE

= AUTO | YES | NO

Automatically create convergence stop criteria. For deactivation, select NO.

STOP_CRITERION_LEVEL

= BOTH

= SINGLE

Parameter if both (BOTH) or just one (SINGLE) of two stop criteria should be fulfilled.

STOP_CRITERION_OBJ

= <real_value>

= 0.001

Stop criterion based on the change in objective function.

STOP_CRITERION_DV

= <real_value>

= 0.005

Stop criterion based on the change in design variable values.

STOP_CRITERION_ITER

= <real_value>

= 4

Parameter defining from which optimization iteration should the two criteria be checked.

SPEED

SPEED size of increment.

= VERY_SLOW

Very small step size.

= SLOW

Small step size.

= MODERATE

Moderate step size.

= MEDIUM

Medium step size.

= FAST

FAST large step size (only permitted in optimization of stiffness with volume constraint).

= ITER, <number_of_iterations>

= ITER,15

Step size is modified dynamically, so the optimization end after the given number of iterations.

START_DELETE

= <operator>, <value>

Setting the volume that can be removed immediately in the first design cycle.

<operator>

= PERC

Specifying the volume in percent.

= ABS

Specifying the absolute volume.

<value>

Volume that is deleted in the first design cycle.

AUTO_FROZEN

= LOAD

All loaded elements and elements with loaded nodes are excluded from the optimization by an automated DVCON_TOPO FROZEN statement.

= OFF

Loaded elements are treated normally (are optimizable).

= SPC

Elements with boundary conditions are excluded from the optimization.

= ALL

All loaded elements and elements with loaded nodes and all with boundary conditions are excluded from the optimization by an automated DVCON_TOPO FROZEN statement.

DENSITY_UPDATE

Parameter for how the densities are updated in the optimization algorithm.

= NORMAL

Normal strategy.

= CONSERVATIVE

Conservative strategy.

= AGGRESSIVE

Aggressive strategy.

DENSITY_INITIAL

= <real_value>

= 0.5

Initial value of relative density when no volume/ mass constraint has been set. In case that a volume/ mass constraint exists and DENSITY_INITIAL is also defined by the user, the initial density values determined by Tosca Structure based on the volume constraint will be overwritten

DENSITY_UPPER

= <real_value>

= 1.0

Upper bound on design variables.

DENSITY_LOWER

= <real_value>

= 0.001

Lower bound on design variables.

DENSITY_MOVE

= <real_value>

= 0.25

Move limit on design variables.

MIN_INITIAL_DENSITY

= <real_value>

MIN_INITIAL_DENSITY can be used optionally to ensure a minimum density when working with low volume fractions. By default DENSITY_INITIAL is set to the value of the volume constraint, but MIN_INITIAL_DENSITY can be used to enforce an upper threshold.

MIN_INITIAL_DENSITY = 0.10 is often a good setting.

FILTER_RADIUS

= <radius>

= 1.3* <average_element_edge_length>

Filter for mesh independence and minimum member size.

FILTER_TYPE

= AUTO

Automatic selection of applied filter type in topology optimization as recommended by Tosca Structure.

= SENS

The conventional filter applied for sensitivities in topology optimization. Recommended for MAT_INTERPOLATION = SIMP

= DV

A new filter for design variables in topology optimization. Recommended for MAT_INTERPOLATION = MIMP

= DV_LEGACY

Legacy filter option of design variables filter, use this option to achieve similar results to version 2020x and before.

FILTER_GROUP

= AUTO

Automatic selection of element groups to be filtered during topology optimization as recommended by Tosca Structure

= ALL

All elements are taken into account when filtering.

= DESIGN_AREA

Only the elements that are contained in the design area are taken into account when filtering.

FILTER_MANU

= YES | NO

Filtering of manufacturing constraints. Set to NO to reproduce the behavior of older releases.

FILTER_USE_VOL

= YES | NO

Filtering will take element volumes into account. Set to NO to reproduce the filter behavior of older releases.

MAT_INTERPOLATION

The material interpolation scheme (generally, the relation between relative density and relative element stiffness, but also parameters effecting other physical properties and related settings).

= SIMP

Solid Isotropic Material with Penalization.

= RAMP

Rational Approximation of Material Properties.

= PEDE

Niels-Pedersen based Approach.

= MIMP

Mass Interpolation Material Penalization.

= 4_TH

Material interpolation using 4th-order polynomial. If this option is set the corresponding factors must be provided using the commands MAT_0_TH_FACTOR, ... , MAT_4_TH_FACTOR.

MAT_0_TH_FACTOR

= <real_value>

= 0.0

Coefficient of the 4th-order polynomial material interpolation, which corresponds to the power of 0 term.

MAT_1_TH_FACTOR

= <real_value>

= 0.0

Coefficient of the 4th-order polynomial material interpolation, which corresponds to the power of 1 term.

MAT_2_TH_FACTOR

= <real_value>

= 0.0

Coefficient of the 4th-order polynomial material interpolation, which corresponds to the power of 2 term.

MAT_3_TH_FACTOR

= <real_value>

= 3.0

Coefficient of the 4th-order polynomial material interpolation, which corresponds to the power of 3 term.

MAT_4_TH_FACTOR

= <real_value>

= 0.0

Coefficient of the 4th-order polynomial material interpolation, which corresponds to the power of 4 term.

MAT_PENALTY

= <real_value>

= 3.0

Penalty factor for interpolation scheme.

PROCESSORS

Number of CPU-processors for Abaqus in combination with sensitivity-based topology optimization and only when using the sensitivities calculated by Tosca Structure (SENS_CALC_MODE = TOSCA).

This option does NOT apply to SENS_CALC_MODE = SOLVER. Abaqus supports parallel execution for sensitivity calculation, see Abaqus documentation for details.

= SINGLE

Abaqus only, single CPU-processor in combination with sensitivity-based topology optimization.

= MULTI

Abaqus only, several CPU-processors in combination with sensitivity-based topology optimization.

STOP_CRITERION_CONVERGENCE

= AUTO | YES | NO

Automatically create convergence stop criteria. For deactivation, select NO.

STOP_CRITERION_LEVEL

= BOTH

= SINGLE

Parameter if both (BOTH) or just one (SINGLE) of two stop criteria should be fulfilled.

STOP_CRITERION_OBJ

= <real_value>

= 0.001

Stop criterion based on the change in objective function.

STOP_CRITERION_DENSITY

= <real_value>

= 0.005

Stop criterion based on the change in element densities.

STOP_CRITERION_ITER

= <real_value>

= 4

Parameter defining from which optimization iteration should the two criteria be checked.

SOFT_DELETE_METHOD

= <method>, <soft_delete_threshold_value>

Method selection for SOFT_DELETE.

<method>

= STANDARD

Removal of elements is done ensuring that there are no detached and floating elements caused by the soft delete.

= AGGRESSIVE

Removal of elements is done based on the rel. density without detachment checks. In this case, detached and floating elements can be caused by the soft delete. Some solvers have problems dealing with such elements but not the Abaqus solver. Note that check of elements in <radius> will still be performed but this procedure is independent of detachment checks.

= MAX_SHEAR_STRAIN

Removal of elements is based on maximum elemental shear strain (with positive shear threshold).

= MIN_PRINCIPAL_STRAIN

Removal of elements based on minimal elemental principal strain (with negative minimum principal threshold).

= PLASTICITY

Removal of elements based on maximum effective equivalent plastic strain (PEEQ) in Abaqus) (only to use with elastic-plastic constitutive material law).

= VOLUME_CHANGE

Removal of elements based on the minimum relative deformed elemental volume ((Vdeform - Vorg) / Vorg) with negative threshold value.

<soft_delete_threshold_value>

= <value>

Relative material density value for identification of elements to be removed (element with a value below will be removed from the finite element calculation file).

= 0.05

For METHOD = STANDARD or AGGRESSIVE.

no default value

For all other methods.

SOFT_DELETE

= <el_group>, <radius>

<el_group>

Name of the element group in which the soft elements should be deleted during optimization.

<radius>

For METHOD = STANDARD or AGGRESSIVE, the default of this value is the average element edge length of the model. User-defined value is considered to be an absolute one. This means that the corresponding units should be taken into account. If any of the elements enclosed in the sphere spanned by the <radius> has a relative density higher than the <soft_delete_threshold_value>, the element in origin will not be deleted.

SOLID_VOID_POST_STRATEGY

= DENSITY_MEASURE

To enforce clearer material distribution, this option can be activated. This will cause extra iterations of the optimization procedure, which are performed after convergence has been detected. Only supported for MIN or MAX objectives.

= NO

No further action is taken to enforce a clear material distribution.

AUTO_FROZEN

= LOAD

All loaded elements and elements with loaded nodes are excluded from the optimization by an automated DVCON_TOPO FROZEN statement.

= OFF

Loaded elements are treated normal (are optimizable).

= SPC/BC

Elements with boundary conditions are excluded from the optimization

= ALL

All loaded elements and elements with loaded nodes and all with boundary conditions are excluded from the optimization by an automated DVCON_TOPO FROZEN statement.

AUTO_FROZEN_CON

= CONTACT

Freeze elements and nodes with contact conditions.

= CONNECTOR

Freeze elements and nodes that are attached to connectors.

= ALL

Freeze elements and nodes with contact conditions and elements and nodes that are attached to connectors.

= OFF

Do not freeze elements and nodes with contact conditions and elements and nodes that are attached to connectors.

STRESS_DRESP_OPT

= YES | NO

For topology optimization with stress constraints the optimizer will use conservative update scheme automatically.

The maximum number of design cycles is set to ITER_MAX = 80, and the move limit DENSITY_MOVE = 0.1

To avoid these automatic settings, use STRESS_DRESP_OPT = NO.

STRESS_DRESP_ITER

= <int_value>

= 4

Parameter defining for how many initial optimization iterations precise sensitivity of stress DRESPs is calculated. In the following optimization iterations, the corresponding sensitivity is approximated. For precise stress sensitivity calculation, the solver is called twice, which can be time consuming.

STABILIZATION

= NO

= YES

When minimizing structural volume or mass, the mathematical optimization problem can be ill-posed, leading to convergence issues. Stabilization can be activated to improve convergence behavior.

UPDATE_CONVECTION

= THERMAL_OPT

The convection is modified modified to include new surfaces generated during the optimization only if a thermal design response is included in the optimization formulation (OPTIMIZE).

= EVER

The convection is always modified to include new surfaces generated during the optimization.

= NEVER

The convection is not modified during the optimization iterations. Therefore, the original convection is kept and used for all iterations during the optimization.

THICKNESS_INITIAL

= <real_value>

= 1.0

Scaling factor of the initial thicknesses when no volume/ mass constraint has been set. In case that a volume/ mass constraint exists and THICKNESS_INITIAL is also defined by the user, the initial thickness values determined by Tosca Structure based on the volume constraint will be overwritten.

THICKNESS_UPDATE

Parameter for how the thicknesses are updated in the optimization algorithm.

= NORMAL

Normal strategy.

= CONSERVATIVE

Conservative strategy.

= AGGRESSIVE

Aggressive strategy.

THICKNESS_MOVE

= <real_value>

= 0.25

Move limit on design variables.

FILTER_RADIUS

= <radius>

= 0.0

Filter for mesh independence and minimum member size.

FILTER_USE_VOL

= YES | NO

Filtering will take element volumes into account. Set to NO to reproduce the filter behavior of older releases.

STOP_CRITERION_CONVERGENCE

= AUTO | YES | NO

Automatically create convergence stop criteria. For deactivation, select NO.

STOP_CRITERION_LEVEL

= BOTH

= SINGLE

Parameter if both (BOTH) or just one (SINGLE) of two stop criteria should be fulfilled.

STOP_CRITERION_OBJ

= <real_value>

= 0.001

Stop criterion based on the change in objective function.

STOP_CRITERION_THICKNESS

= <real_value>

= 0.005

Stop criterion based on the change in element densities.

STOP_CRITERION_ITER

= <real_value>

= 4

Parameter defining from which optimization iteration should the two criteria be checked.

AUTO_FROZEN

= LOAD

All loaded elements and elements with loaded nodes are excluded from the optimization by an automated DVCON_TOPO FROZEN statement.

= OFF

Loaded elements are treated normal (are optimizable).

= SPC/BC

Elements with boundary conditions are excluded from the optimization

= ALL

All loaded elements and elements with loaded nodes and all with boundary conditions are excluded from the optimization by an automated DVCON_TOPO FROZEN statement.

AUTO_FROZEN_CON

= CONTACT

Freeze elements and nodes with contact conditions.

= CONNECTOR

Freeze elements and nodes that are attached to connectors.

= ALL

Freeze elements and nodes with contact conditions and elements and nodes that are attached to connectors.

= OFF

Do not freeze elements and nodes with contact conditions and elements and nodes that are attached to connectors.

VECTOR

= FIRST

=EVER

Update of the optimization displacement vector occurs in the first or in each design cycle.

SCALE

= <real_value>

Definition of the direction of the optimization displacement.

BEAD_WIDTH

= <real_value>

Bead wide.

BEAD_ITER

= <int_value>

Definition of the number of iterations.

BEAD_MIN_STRESS

= <real_value>

= 0.001

Value, relative to the highest von Mises stress in the design area, under which, no optimization should be performed. Value between 0.0 and 1.0, where 1.0 is equal the highest von Mises stress.

BEAD_MAX_MEMBRANE

= <real_value>

= 1.0

Value of the maximal membrane stress relative to maximal bending stress in original model under which no optimization is performed. Value is greater than 0.

= CONTINUOUS

Sorting filter values by the bending loads.

= DISCRETE

Filtering whole design area.

CURV_SMOOTH

= <elem_edge_length>

= 5.0

Filtering the normals, effect for curved geometries. Value is relative to the medium element edge length.

BEAD_NODE_SMOOTH

= <real_value>

= 0.25 (of BEAD_WIDTH)

This defines the minimum distance between a node at zero optimization displacement and one at maximal bead height.

FILTER_RADIUS

= <real_value>, ABS

= <real_value>, REL

= 4.0, REL

Radius with which the sensitivities are filtered.

REL is relative to medium edge length of elements in the design area. Values might also be set absolute (ABS).

ONLY_DES_NODES

= YES

= NO

Calculate sensitivities for only design nodes (YES) or all nodes (NO) which is not recommended.

NODAL_MOVE

= <real_value>

= 0.1

Relative move limit of node-based optimization displacement per iteration. Value is between 0 and1.

NODAL_UPDATE

= CONSERVATIVE

= NORMAL

= AGGRESSIVE

Parameter for how the nodal displacements are updated in the optimization algorithm.

PERTURBATION

= <real_value>

= 0.0001

Sets perturbation size for finite differences (relative to medium element edge length).

STOP_CRITERION_CONVERGENCE

= AUTO | YES | NO

Automatically create convergence stop criteria. For deactivation, select NO.

STOP_CRITERION_LEVEL

= BOTH

= SINGLE

Parameter if both (BOTH) or just one (SINGLE) of two stop criteria should be fulfilled.

STOP_CRITERION_OBJ

= <real_value>

= 0.001

Stop criterion based on the change in objective function.

STOP_CRITERION_DV

= <real_value>

= 0.005

Stop criterion based on the change in design variable values.

STOP_CRITERION_ITER

= <real_value>

= 4

Parameter defining from which optimization iteration should the two criteria be checked.

VECTOR

= FIRST

=EVER

Update of the optimization displacement vector occurs in the first or in each design cycle.